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1.
  • Amman, B., et al. (författare)
  • Quantification of biotic responses to rapid climatic changes around the Younger Dryas – a synthesis.
  • 2000
  • Ingår i: Palaeogeography, Palaeoclimatology, Palaeoecology. - 0031-0182 .- 1872-616X. ; 159:3-4, s. 313-347
  • Tidskriftsartikel (refereegranskat)abstract
    • To assess the presence or absence of lags in biotic responses to rapid climatic changes, we: (1) assume that the delta(18)O in biogenically precipitated carbonates record global or hemispheric climatic change at the beginning and at the end of the Younger Dryas without any lag at our two study sites of Gerzensee and Leysin, Switzerland; (2) derive a time scale by correlating the delta(18)O record from these two sites with the delta(18)O record of the GRIP ice core; (3) measure delta(18)O records in ostracods and molluscs to check the record in the bulk samples and to detect possible hydrological changes; (4) analyse at Gerzensee and Leysin as well as at two additional sites (that lack carbonates and hence a delta(18)O record) pollen, plant macrofossils, chironomids, beetles and other insects, and Cladocera; (5) estimate our sampling resolution using the GRIP time scale for the isotope stratigraphies and the biostratigraphies; and (6) summarise the major patterns of compositional change in the biostratigraphies by principal component analysis or correspondence analysis. We conclude that, at the major climatic shifts at the beginning and end of the Younger Dryas, hardly any biotic lags occur (within the sampling resolution of 8-30 years) and that upland vegetation responded as fast as aquatic invertebrates. We suggest that the minor climatic changes associated with the Gerzensee and Preboreal oscillations were weakly recorded in the biostratigraphies at the lowland site, but were more distinct at higher altitudes. Individualistic responses of plant and animal species to climatic change may reflect processes in individuals (e.g. productivity and phenology), in populations (e.g. population dynamics), in spatial distributions (e.g. migrations), and in ecosystems (e.g. trophic state). We suggest that biotic responses may be telescoped together into relatively short periods (50 to 150 years), perhaps disrupting functional interactions among species and thus destabilising ecosystems.
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3.
  • Henriksson, Anders (författare)
  • Coccolithophore response to oceanographic changes in the Equatorial Atlantic during the last 200,000 years
  • 2000
  • Ingår i: Palaeogeography, Palaeoclimatology, Palaeoecology. - 0031-0182 .- 1872-616X. ; 156:1-2, s. 161-173
  • Tidskriftsartikel (refereegranskat)abstract
    • A deep-sea core from the eastern equatorial Atlantic (Meteor core 16772, 1 degrees 21'S, 11 degrees 58'W) revealed strong primary productivity variations (70-230 gC/m (super 2) /year) based on the relative abundance (%) of the deep living coccolithophore Florisphaera profunda with productivity maxima following temperature minima during the last 200,000 years. The response of the coccolithophore flora was investigated by relative and absolute abundance records of coccoliths. The wind strength and the resulting equatorial upwelling intensity are thought to comprise the most important control of coccolith abundance and species composition, which reflects the different abundance of coccolithophores living in the upper or lower photic zone. Relative abundances of the different species varies widely throughout the core. Although a wide range of species were present in the different samples, three different taxa dominated the assemblage. The lower photic zone species F. profunda was the most abundant, with a mean relative abundance of 49.4% throughout the core. The upper photic zone flora were divided into three groups. Emiliania huxleyi together with small Gephyrocapsa (<3mu m) was the second most abundant species group (mean 20.8%). Gephyrocapsa oceanica was the third most important species in the core and had a mean relative abundance of 16.8%. All other species together represented a mean of 13%. Highest absolute abundance of coccoliths (number/gram sediment) occurs in sediments deposited during periods of high SST, mainly in warm isotope stages 1 and 5. The accumulation rates of coccoliths (number/cm (super 2) /ky) show peaks in isotope stages 1 and 5, but also in some parts of cool isotope stages 4 and 6. High relative and absolute abundance of F. profunda were found in warm isotope stages, which suggests that a deep nutricline existed and that primary productivity was low. Absolute and relative abundance records of E. huxleyi and small Gephyrocapsa (<3mu m) mainly showed higher values in sediments from warm periods. The other upper photic zone coccolith species were generally more abundant during periods of low SST, particularly in isotope stages 2, 4, and 6, which were times of high primary productivity and a shallow nutricline. This suggest that E. huxleyi and small Gephyrocapsa probably were able to live deeper in the water column than most other species during periods of low nutrient supply to the upper photic zone. In summary, the composition of the coccolith flora can be explained by the nutricline depth level with three different assemblages being recognized, a deep photic zone assemblage consisting of F. profunda, a middle-upper photic zone assemblage of E. huxleyi and small Gephyrocapsa and an upper photic zone assemblage consisting of all other species.
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4.
  • Lemdahl, Geoffrey (författare)
  • Lateglacial and Early Holocene insect assemblages from sites at different altitudes in the Swiss Alps - implications on climate and environment.
  • 2000
  • Ingår i: Palaeogeography, Palaeoclimatology, Palaeoecology. - 0031-0182 .- 1872-616X. ; 159:3-4, s. 293-312
  • Tidskriftsartikel (refereegranskat)abstract
    • Insect analyses from four sites at differentaltitudes in the SwissAlps are presented. The dominant insect group considered here is Coleoptera (beetles), though other insect orders are also recorded. The study includes the first detailed insect records dating to the Younger Dryas in Switzerland. The quantitative climatic reconstructions based on coleopteran assemblages were made using the MCR method. Mean temperatures of the warmest month similar to modern intensities are indicated at the end of Allerød interstadial (AL) and at the beginning of the Holocene (PB). The winters during the AL were rather colder, implying more continental conditions than at present. During the Younger Dryas stadial (YD), the mean temperatures of the warmest month were 5–8°C colder than those of the present day, and the mean temperatures of the coldest month were about 10–12°C colder than today. A rapid change in the faunal composition was found at the Gerzensee and Zeneggen sites during the transition YD/PB. The change is characterized by the disappearance of cold-adapted species between two contiguous samples (i.e. within 1.0 cm of sediment sampled). At Gerzensee, the cold-adapted species assemblage was immediately replaced by temperate species. The Coleoptera thus indicate extremely rapid and intense climatic oscillations at the Lateglacial–Holocene transition.
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5.
  • Abbott, P. M., et al. (författare)
  • Re-evaluation and extension of the Marine Isotope Stage 5 tephrostratigraphy of the Faroe Islands region : The cryptotephra record
  • 2014
  • Ingår i: Palaeogeography, Palaeoclimatology, Palaeoecology. - : Elsevier BV. - 0031-0182 .- 1872-616X. ; 409, s. 153-168
  • Tidskriftsartikel (refereegranskat)abstract
    • Previous studies of marine sequences from the Faroe Islands region have identified a series of coarse-grained tephra horizons deposited during Marine Isotope Stage (MIS) 5. Here we reassess the MIS 5 tephrostratigraphy of the Faroe Islands region and focus on the cryptotephra deposits preserved within the fine-grained fraction of marine core LINK 16. We also extend the record to encompass the late MIS 6 and early MIS 4 periods. A density separation technique, commonly used for tephra investigations in lacustrine settings but rarely applied to marine sediments, is utilised to explore the fine-grained material and EPMA and LA-ICP-MS are employed to determine the major and trace element composition of individual tephra shards. In total, 3 basaltic and 3 rhyolitic Icelandic cryptotephra deposits with homogeneous geochemical compositions are identified - all of which have the potential to act as isochronous tie-lines. Geochemical results highlight that the Grimsvotn volcanic system of Iceland is the predominant source of the basaltic horizons and the Oraefajokull or Torfajokull systems are the likely sources of the rhyolitic deposits. Three of the horizons have been previously recognised in Faroe Islands region marine sequences, with two of these deposits traceable into a Norwegian Sea sequence. An early MIS 4 rhyolitic horizon is the most widespread deposit as it can be traced into the Norwegian Sea and to the south into a record from the Rockall Trough. Basaltic and rhyolitic horizons deposited during late MIS 6 have not been recognised in other sequences and represent new additions to the regional tephrostratigraphy.
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6.
  • Agic, Heda, et al. (författare)
  • Life through an Ediacaran glaciation : Shale- and diamictite-hosted organic-walled microfossil assemblages from the late Neoproterozoic of the Tanafjorden area, northern Norway
  • 2024
  • Ingår i: Palaeogeography, Palaeoclimatology, Palaeoecology. - : Elsevier. - 0031-0182 .- 1872-616X. ; 635
  • Tidskriftsartikel (refereegranskat)abstract
    • New organic-walled microfossil (OWM) assemblages are reported from upper Neoproterozoic glacial and interglacial siliciclastic deposits in Finnmark, northern Norway. A nearly continuous sedimentary succession of the Vestertana Group contains two glaciogenic units, the Smalfjorden and Mortensnes formations, interpreted as end-Cryogenian Marinoan and Ediacaran glaciations, respectively. We investigated the OWM record in the Nyborg, Mortensnes, and St ' ahpogieddi formations to assess the impact of a glacial interval on the diversity of microscopic eukaryotes. A modified acid-extraction technique was applied to recover OWM from the diamictite matrix. The upper Nyborg Formation contains morphologically complex Doushantuo-Pertatataka acritarchs (DPA), restricting the age of the Nyborg Formation to early-mid Ediacaran. DPA occur below the dolostones that record a negative carbon isotope excursion correlated with the Shuram anomaly and below a glacial diamictite. A decline in species richness and compositional change is observed in the Mortensnes glacial assemblage. DPA are replaced by bacterial filaments and cell aggregates. The overlying Indreelva Member, St ' ahpogieddi Formation contains Ediacara-type biota and palaeopascichnids, but only a depauperate OWM assemblage of leiosphaerids and flask-shaped microfossils characteristic of the late Ediacaran.The succession of assemblages in the Vestertana Group demonstrates a turnover from large eukaryotic OWM to a microbial community in the glacial interval, to a low diversity post-glacial assemblage during the rise of macroscopic life. We compared the Vestertana record to global DPA occurrences. Although one DPA assemblage zone postdates the Shuram excursion, no DPA occur above Ediacaran glacial diamictites in successions where those deposits are present. Considering this, and the community changes in the Vestertana succession, we suggest that DPA were affected by the onset of an Ediacaran glaciation. Lastly, we combined the biostratigraphic markers in the Vestertana Group to constrain the age of the Mortensnes diamictite.
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7.
  • Albanesi, Guillermo L., et al. (författare)
  • Darriwilian (Middle Ordovician) delta C-13(carb) chemostratigraphy in the Precordillera of Argentina: Documentation of the middle Darriwilian Isotope Carbon Excursion (MDICE) and its use for intercontinental correlation
  • 2013
  • Ingår i: Palaeogeography, Palaeoclimatology, Palaeoecology. - : Elsevier BV. - 1872-616X .- 0031-0182. ; 389, s. 48-63
  • Tidskriftsartikel (refereegranskat)abstract
    • Although documented from Estonia, Latvia, Sweden, eastern North America, and China, the Middle Ordovician (Darriwilian) positive delta C-13 excursion known as the MDICE has previously not been recognized with certainty in South America. The most promising region in South America for detailed Middle Ordovician carbon isotope research is the Precordillera of western Argentina, where there are many excellent exposures of biostratigraphically well-dated carbonate successions spaning the Tremadocian through Sandbian stratigraphic interval. For this project, we collected numerous isotope and conodont samples from the middle Darriwilian Las Chacritas and Aguaditas formations at their type localities, which yielded important biostratigraphic data as well as informative delta C-13(carb) values. In the E. pseudoplanus Zone in the upper half of the Las Chacritas Formation, there is a relatively modest but distinct delta C-13(carb) excursion. Because its stratigraphic position and magnitude closely agree with the MDICE in other parts of the world, we recognize it as the first firm record of this excursion in South America. The fact that the delta C-13(carb) curve from the Las Aguaditas Formation shows no such excursion is due to the existence of a stratigraphic gap between the Lower and Middle Members of this formation that cuts out the excursion interval. The Precordilleran MDICE is used for detailed long-range correlations with successions in Baltoscandia, Newfoundland, and China illustrating the usefulness of also this delta C-13(carb) excursion as a global stratigraphic tool. A recent proposal of a greatly extended chronostratigraphic range of the Table Head Group on Newfoundland is rejected based on well-established biostratigraphic evidence. (C) 2013 Elsevier B.V. All rights reserved.
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9.
  • Andrén, Elinor, et al. (författare)
  • Medieval versus recent environmental conditions in the Baltic Proper, what was different a thousand years ago?
  • 2020
  • Ingår i: Palaeogeography, Palaeoclimatology, Palaeoecology. - : Elsevier. - 0031-0182 .- 1872-616X. ; 555
  • Tidskriftsartikel (refereegranskat)abstract
    • A sediment record from the western Gotland Basin, northwestern Baltic Proper, covering the last 1200 years, was investigated for past changes in climate and the environment using diatoms as a proxy. The aim is to compare the environmental conditions reconstructed during Medieval times with settings occurring the last century under influence of environmental stressors like eutrophication and climate change. The study core records more marine conditions in the western Gotland Basin surface waters during the Medieval Climate Anomaly (MCA; 950–1250C.E.), with a salinity of at least 8 psu compared to the present 6.5 psu. The higher salinity together with a strong summer-autumn stratification caused by warmer climate resulted in extensive long-lasting diatom blooms of Pseudosolenia calcar-avis, effectively enhancing the vertical export of organic carbon to the sediment and contributing to benthic hypoxia. Accordingly, our data support that a warm and dry climate induced the extensive hypoxic areas in the open Baltic Sea during the MCA. During the Little ice Age (LIA; 1400–1700C.E.), the study core records oxic bottom water conditions, decreasing salinity and less primary production. This was succeeded during the 20th century, about 1940, by environmental changes caused by human-induced eutrophication. Impact of climate change is visible in the diatom composition data starting about 1975C.E. and becoming more pronounced 2000C.E., visible as an increase of taxa that thrived in stratified waters during autumn blooms typically due to climate warming.
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10.
  • Bajdek, Piotr, et al. (författare)
  • Putative dicynodont coprolites from the Upper Triassic of Poland
  • 2014
  • Ingår i: Palaeogeography, Palaeoclimatology, Palaeoecology. - : Elsevier BV. - 0031-0182 .- 1872-616X. ; 411, s. 1-17
  • Tidskriftsartikel (refereegranskat)abstract
    • A significant number (more than 100) of brownto dark and silty, carbonate or pyrite-mineralized, in part organic carbon-rich, spherical or oval-shaped structures have been collected fromthe Upper Triassic (uppermost NorianlowerRhaetian) sediments of the Lipie Śląskie clay-pit at Lisowice near Lubliniec town, Poland. Their geological context, morphology, content, geochemistry and association with skeletal remains suggest they are fecal masses of a sizable herbivorous tetrapod. The only large herbivore known from the site is a giant 5 meter-long dicynodont (Synapsida: Anomodontia), represented by numerous bones and also by large, oval-shaped footprints. The putative dicynodont coprolites were collected from mudstone and siltstone with numerous organic remains that were deposited in anoxic conditions. In addition, REEs and other trace element concentrations suggest that the burial environment and diagenesis of these coprolites were under anoxic conditions. SEM and thin section images of the coprolite matrix show numerous nests with pyrite (probably bacterial in origin) and large amount of mineral particles. The putative dicynodont coprolites contain also amorphous, dark organic matter, poorly preserved palynomorphs, small fragments of plant cuticle. Detailed characteristic of these coprolites reveals possible implications for the ecology and physiology of the source animal species. The δ 13C values of the gymnospermcuticle and dark organic matter measured in three coprolites are −23.4‰, −21.2‰and −20.3‰, all average. The evidence from these coprolites suggests that dicynodonts processed plant soft elements into very small pieces, but wood fragments were found also in a mass accumulation in two coprolites.
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11.
  • Bajdek, Piotr, et al. (författare)
  • Residues from the Upper Permian carnivore coprolites from Vyazniki in Russia - key questions in reconstruction of feeding habits
  • 2017
  • Ingår i: Palaeogeography, Palaeoclimatology, Palaeoecology. - : ELSEVIER SCIENCE BV. - 0031-0182 .- 1872-616X. ; 482, s. 70-82
  • Tidskriftsartikel (refereegranskat)abstract
    • Residues of twenty-five coprolite fragments collected from the Upper Permian of Vyazniki (European Russia) were studied in detail. The phosphatic composition, general shape and size, and bone inclusions of these specimens indicate that medium to large-sized carnivores, such as therocephalian therapsids or early archosauriforms, were the most likely coprolite producers. The contents of the examined fossils (i.e. Scale, bone and tooth fragments, mineral grains, and microbial structures) do not differ significantly among the samples, implying fairly comparable feeding habits of their producers. Fragments of large tooth crowns in two of the analyzed samples imply that either (1) the coprolite producer swallowed the cranial elements of its prey or (2) the coprolite producer broke and swallowed its own tooth while feeding (such tooth damage is known in archosaurs that have tooth replacement, e.g. crocodiles and dinosaurs). Indeed, the most complete tooth fragment in these fossils is serrated, most likely belonging to an early archosauriform known from skeletal records from the Late Permian of Vyaznilci. Another coprolite fragment contains the etched tooth of a lungfish, while putative actinopterygian fish remains (scales and small fragments of bones) are abundant in some samples. Mineral particles (mostly quartz grains, feldspars and mica) may have been swallowed accidentally. The preserved microbial colonies (mineralized fossil fungi and bacteria or their pseudomorphs), manifested in the coprolites as Fe-rich mineral structures, seem to have developed on the expelled feces rather than on the items before they were swallowed.
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12.
  • Baker, Andrea, et al. (författare)
  • Biomarker records of palaeoenvironmental variations in subtropical Southern Africa since the late Pleistocene : Evidences from a coastal peatland
  • 2016
  • Ingår i: Palaeogeography, Palaeoclimatology, Palaeoecology. - : Elsevier. - 0031-0182 .- 1872-616X. ; 451:1, s. 1-12
  • Tidskriftsartikel (refereegranskat)abstract
    • Southern Africa's unique global position has given rise to a dynamic climate influenced by large sea surface temperature gradients and seasonal fluctuations in the Inter Tropical Convergence Zone. Due to the semi-arid climate of the region, terrestrial palaeorecords are rare and our understanding of the long-term sensitivity of Southern African terrestrial ecosystems to climatic drivers is ambiguous. A 810 cm continuous peat core was extracted from the Mfabeni peatland with a 14C basal age of c. 47 thousand years calibrated before present (kcal yr BP), positioning it as one of the oldest known sub-tropical coastal peatlands in Southern Africa. This peat core provides an opportunity to investigate palaeoenvironmental changes in subtropical Southern Africa since the late Pleistocene. Biomarker (n-alkane, n-alkanoic acid and n-alkanol) analysis, in conjunction with previously published bulk geochemical data, was employed to reconstruct organic matter (OM) sources, rates of OM remineralisation and peatland hydrology. Our results showed that the principal OM source into the peatland was emergent and terrestrial plants with exception of shallow lake conditions when submerged macrophytes dominated (c. 44.5–42.6, 29.7, 26.1–23.1, 16.7–7.1 and 2.2 kcal yr BP). n-Alkane proxies suggest that local plant assemblages were predominantly influenced by peatland hydrology. By incorporating temperature sensitive n-alkanoic acid and n-alkanol proxies, it was possible to disentangle the local temperature and precipitation changes. We report large variations in precipitation intensities, but subdued temperature fluctuations during the late Pleistocene. The Holocene period was characterised by overall elevated temperatures and precipitation compared to the preceding glacial period, interspersed with a millennial scale cooling event. A close link between the Mfabeni archive and adjacent Indian Ocean marine core records was observed, suggesting the regional ocean surface temperatures to be the dominant climate driver in this region since the late Pleistocene.
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13.
  • Baker, A., et al. (författare)
  • Geochemical records of palaeoenvironmental controls on peat forming processes in the Mfabeni peatland, Kwazulu Natal, South Africa since the Late Pleistocene
  • 2014
  • Ingår i: Palaeogeography, Palaeoclimatology, Palaeoecology. - : Elsevier. - 0031-0182 .- 1872-616X. ; 395, s. 95-106
  • Tidskriftsartikel (refereegranskat)abstract
    • The Mfabeni peatland is the only known sub-tropical coastal fen that transcends the Last Glacial Maximum (LGM). This ca. 10 m thick peat sequence provides a continuous sedimentation record spanning from the late Pleistocene to present (basal age c. 47 kcal yr BP). We investigated the paleaeoenvironmental controls on peat formation and organic matter source input at the Mfabeni fen by: 1) exploring geochemical records (mass accumulation rate, total organic carbon, carbon accumulation rate, delta C-13, delta N-15 and C/N ratio) to delineate primary production, organic matter source input, preservation and diagenetic processes, and 2) employ these geochemical signatures to reconstruct the palaeoenvironmental conditions and prevailing climate that drove carbon accumulation in the peatland. We established that the Mfabeni peat sediments have undergone minimal diagenetic alteration. The peat sequence was divided into 5 linear sedimentation rate (LSR) stages indicating distinct changes in climate and hydrological conditions: ISR stage 1 (c. 47 to c. 32.2 kcal yr BP): predominantly cool and wet climate with C4 plant assemblages, interrupted by two short warming events. LSR stage 2 (c. 32.2 to c. 27.6 kcal yr BP): dry and windy climate followed by a brief warm and wet period with increased C4 sedge swamp vegetation. LSR stage 3 (c. 27.6 to c. 20.3 kcal yr BP): initial cool and wet period with prevailing C4 sedge plant assemblage until c. 23 kcal yr BP; then an abrupt change to dry and cool glacial conditions and steady increases in C3 grasses. LSR stage 4 (c. 203 to c. 10.4 kcal yr BP): continuation of cool and dry conditions and strong 0 grassland signature until c. 15 kcal yr BP, after which precipitation increases. LSR stage 5 (c. 10.4 kcal yr BP to present): characterised by extreme fluctuations between pervasive wet and warm to cool interglacial conditions with intermittent abrupt millennial-scale cooling/drying events and oscillations between C3 and C4 plant assemblages. In this study we reconstructed a high-resolution record of local hydrology, bulk plant assemblage and inferred climate since the Late Pleistocene, which suggest an anti-phase link between Southern African and the Northern Hemisphere, most notably during Heinrich (5 to 2) and Younger Dryas events.
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14.
  • Balestra, Barbara, et al. (författare)
  • Bottom-water oxygenation and environmental change in Santa Monica Basin, Southern California during the last 23kyr
  • 2018
  • Ingår i: Palaeogeography, Palaeoclimatology, Palaeoecology. - : Elsevier BV. - 0031-0182. ; 490, s. 17-37
  • Tidskriftsartikel (refereegranskat)abstract
    • The Southern California Borderland is a region that experiences strong natural variations in bottom water oxygen and pH. We use marine sediments from Santa Monica Basin to reconstruct environmental conditions in the basin's bottom water from the Last Glacial Maximum (LGM) to present. We then compare the records to the adjacent Santa Barbara Basin and Santa Lucia Slope. High-resolution records of benthic foraminiferal oxygen and carbon isotopes (δ18O and δ13C), benthic foraminiferal assemblages, and bulk sedimentary organic matter geochemistry records exhibit major changes associated with late Quaternary millennial-scale global climate oscillations. Our data show the dominance of low-oxygen benthic foraminiferal assemblages during warm intervals, and assemblages representing higher dissolved oxygen during cooler intervals, as also seen in Santa Barbara Basin and Santa Lucia Slope. However, our record shows a stronger and longer-lasting oxygen minimum zone (OMZ) between the mid Younger Dryas (YD) and the Early Holocene than at neighboring sites, indicated by dominance of Bolivina tumida (characteristic of major hypoxia) in the assemblage. The middle to late Holocene (from ∼9 to 0kyr) had weaker hypoxia than the early Holocene, with assemblages mainly composed of Bolivina argentea and Uvigerina peregrina. Santa Monica Basin remained slightly hypoxic throughout the past 23kyr, however, differences in the degree of hypoxia from Santa Barbara Basin and Santa Lucia Slope (especially from the B-A to the Early Holocene) are seen. The Santa Monica Basin bottom water is affected by regional processes, such as changes in the source of intermediate water and/or changing ventilation (oxygenation) of the intermediate water source. This is due to the greater depth and the more southern geographic position of the Basin, which reduces exposure to the oxygenated North Pacific Intermediate Water current. Additional local processes also affect the basin, such as the effects of sediment influx from submarine canyons. This analysis utilizing parallel geochemical and micropaleontological records brings new insights into bottom water and climate conditions in Santa Monica Basin, indicating regional similarities and differences from adjacent basins, and provides insight into the causes for changes in bottom water oxygenation.
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15.
  • Bao, Guang, et al. (författare)
  • April–September mean maximum temperature inferred from Hailar pine (Pinus sylvestris var. mongolica) tree rings in the Hulunbuir region, Inner Mongolia, back to 1868 AD
  • 2012
  • Ingår i: Palaeogeography, Palaeoclimatology, Palaeoecology. - : Elsevier BV. - 0031-0182. ; 313-314, s. 162-172
  • Tidskriftsartikel (refereegranskat)abstract
    • Two robust tree-ring width chronologies were developed for the Hulunbuir region, Inner Mongolia, northeast China. Both chronologies were significantly correlated with each other and were arithmetically averaged to build a regional chronology (NBSTD). NBSTD showed significant and negative correlations with the growing season maximum temperature from April to September. Based on this relationship, the mean maximum temperature of April to September was reconstructed for the period from 1868 to 2008. The percentage of variance in the data explained by the reconstruction was 40.3% during the calibration period of 1953–2008. Five severe warm events of two years or more were found in 1905–1909, 1996–1997, 2000–2001, 2003–2005 and 2007–2008. Five cold events occurred during the periods 1880–1881, 1897–1900, 1948–1949, 1955–1960 and 1962–1964. On a decadal scale, several warm intervals (above the 1868–2008 mean) were 1904–1913, 1920–1933, 1968–1975 and 1990–2003. Cold intervals (below the mean) were 1893–1901, 1950–1963 and 1976–1989. Warmer events and intervals corresponded to dry periods. Colder events and intervals coincided with wet or moist conditions in and near the study region. Spatial correlation patterns revealed that our reconstruction represents a regional temperature and drought signal for the central and eastern Mongolian Plateau. Comparison with other tree ring-based temperature reconstructions from surrounding areas provides a high degree of confidence in our reconstruction. Power spectrumandwavelet analyses suggest that the reconstructed mean maximum temperature variation may be related to large-scale atmospheric–oceanic variability such as the Pacific Decadal Oscillation (PDO), El Niño–Southern Oscillation (ENSO) and sunspot activity.
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16.
  • Bergstrom, Stig M., et al. (författare)
  • Katian (Upper Ordovician) delta C-13 chemostratigraphy and sequence stratigraphy in the United States and Baltoscandia: A regional comparison
  • 2010
  • Ingår i: Early Palaeozoic sea level and climate - Selected papers presented at the IGCP 503 closing meeting in Lille (France), 23-31 August 2008 (Palaeogeography, Palaeoclimatology, Palaeoecology). - : Elsevier BV. - 0031-0182 .- 1872-616X. ; 296:3-4, s. 217-234
  • Konferensbidrag (refereegranskat)abstract
    • delta C-13 values of numerous limestone samples from Katian (Upper Ordovician) successions in Oklahoma and the Upper Mississippi Valley document the presence of at least three of the four positive excursions that have been recognized in the lower-middle Katian interval in the Cincinnati region in Ohio. Kentucky, and Indiana. A comparison with Estonia reveals that five out of the six positive excursions now recorded through the Katian succession in the Cincinnati region are present in the coeval stratigraphic intervals in Estonia, which suggests that these represent global perturbations in the carbon cycle A study of the relations between flooding events and delta C-13 excursions shows that only some of the excursions occur in transgressive intervals whereas other excursions are in regressive strata and hence, this is in conflict with the idea that positive carbon isotope excursions are forced by rises in sea level Part of a previously published attempt to use Upper Ordovician sequence stratigraphy for trans-Atlantic correlation is shown to be seriously out of phase with the biostratigraphy and chemostratigraphy Several of the sequences recognized in the Cincinnati region do not appear to have counterparts in Estonia, which suggests that they do not reflect eustatic, but local, conditions (C) 2010 Elsevier B V All rights reserved.
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17.
  • Bergström, Stig M., et al. (författare)
  • Upper Ordovician δ13Corg chemostratigraphy, K-bentonite stratigraphy, and biostratigraphy in southern Scandinavia : A reappraisal
  • 2016
  • Ingår i: Palaeogeography, Palaeoclimatology, Palaeoecology. - : Elsevier BV. - 0031-0182. ; 454, s. 175-188
  • Tidskriftsartikel (refereegranskat)abstract
    • A pioneer δ13Corg study through the upper Sandbian and Katian (Upper Ordovician) succession in the Röstånga 1 drill core in the classical geological outcrop area at Röstånga in southernmost Sweden produced a wealth of new carbon isotope data which are useful for local and regional correlations. Among the Upper Ordovician positive δ13C excursions, the Guttenberg (GICE), Waynesville (Saunja), Whitewater (Moe), Paroveja, and Hirnantian (HICE) isotopic carbon excursions are recognized but the Kope (Rakvere) δ13C excursion is missing, suggesting a stratigraphic gap. All these isotopic excursions are tied closely to biostratigraphy, especially graptolite biostratigraphy, and in the case of the Waynesville (Saunja) and Whitewater (Moe) excursions, for the first time anywhere in the world. The Röstånga GICE δ13Corg curve from the upper Sularp Shale shows a striking similarity to that of the Katian GSSP in Oklahoma, suggesting the potential of trans-Atlantic correlation. Based on a projection from the Katian GSSP, the previously poorly constrained position of the base of the Katian in southern Sweden appears to be in the uppermost Sularp Shale in strata of the upper Diplograptus foliaceus Zone. Previous interpretations of the relations between K-bentonite successions in southern Scandinavia are somewhat revised and the Kinnekulle K-bentonite is recognized for the first time in Scania. Based on new radiometric dates, this very prominent and widespread ash bed appears to be slightly older than the Deicke and Millbrig K-bentonites in eastern North America.
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18.
  • Bicknell, Russell D. C., et al. (författare)
  • Cambrian carnage : Trilobite predator-prey interactions in the Emu Bay Shale of South Australia
  • 2022
  • Ingår i: Palaeogeography, Palaeoclimatology, Palaeoecology. - : Elsevier. - 0031-0182 .- 1872-616X. ; 591
  • Tidskriftsartikel (refereegranskat)abstract
    • The Cambrian explosion represents the rapid emergence of complex marine ecosystems on Earth. The propagation of predator-prey interactions within these systems was almost certainly one of the major drivers of this evolutionary event, sparking an arms race that promoted the proliferation of biomineralised exoskeletons and shells, and the evolution of the first durophagous (shell-crushing) predators. The most commonly documented evidence of Cambrian durophagous predation comes from injured trilobites. However, quantitative analysis based on multiple specimens from single localities is lacking. Such studies are required to reveal the dynamics of ancient predator-prey systems at fine ecological scales (e.g. at the population or community level). This study documents injured specimens of two trilobite species, Redlichia takooensis and Redlichia rex, from the Emu Bay Shale Konservat-Lagersta center dot tte (Cambrian Series 2, Stage 4) on Kangaroo Island, South Australia. A total of 38 injured specimens exhibiting various healed cephalic and thoracic injuries are documented, in addition to the mangled remains of two individuals that probably resulted from the activities of a durophagous predator or scavenger. Specimens of both species show that most injuries are located on the posterior portion of the thorax, indicating that predators preferentially attacked from behind and/or prey individuals presented the posterior of the trunk towards the predator when threatened or fleeing. The larger sample of injured R. takooensis shows that while unilateral injuries are more common than bilateral ones, there is no evidence for a left-or right-side bias, contrasting with previous suggestions that Cambrian trilobites exhibit right-sided injury stereotypy. Comparing the position of injured and non-injured R. takooensis and R. rex in bivariate space, we illustrate that injured specimens of both species typically represent some of the largest individuals of these taxa. This suggests that smaller individuals were completely consumed during an attack and/or larger individuals were more likely to survive an attack and thus record a healed injury. We argue that R. rex, rather than radiodonts, was likely the chief producer of exoskeletal injuries and large shelly coprolites in the Emu Bay Shale biota, and represents one of the earliest cannibalistic trilobites.
  •  
19.
  •  
20.
  • Blaesild, Paulina, et al. (författare)
  • Early Holocene vegetation development at Mesolithic fen dwelling sites in Dagsmosse, south-central Sweden, and its implications for understanding environment–human dynamics at various scales
  • 2024
  • Ingår i: Palaeogeography, Palaeoclimatology, Palaeoecology. - 0031-0182. ; 641
  • Tidskriftsartikel (refereegranskat)abstract
    • Recent discoveries of several Mesolithic sites within the Dagsmosse Basin, south-central Sweden, offer an opportunity to study the lifestyle and skillsets of Mesolithic hunter-gatherer-fishers operating in wetland environments. In this paper, we present a combined archaeological and palaeoecological analysis of a Mesolithic fenland environment using Repetitive-Proxy Pollen Analysis (RPPA) of early Holocene sequences. Based on comparison of stratigraphic profiles from two cores within the basin, we infer that the variance in pollen composition and anthropogenic signals reflect variability in human/vegetation interactions in the fenland, at different distances to the main human dwelling at Jussberg (9.0–8.2 ka cal BP). Our study describes the socio-environmental relations within the wetland and adjacent terrestrial areas, providing a basis for tracking changes in forager interactions with their surroundings during the Mesolithic. Pollen analysis is consistent with the previously established sequence of settlement phases and extent as well as providing new data concerning the anthropogenic impacts on plant communities within the wetland including the use, reuse, and management of vegetation taxa. Correlations between palaeoecological and archaeological data demonstrate that forager communities (i) prevailed in the open fenland landscape between 9.3 and 8.2 ka cal BP, (ii) actively altered taxa composition through small-scale clearings of pine (Pinus), birch (Betula) and sedges (Cyperaceae) and (iii) reduced canopy cover, possibly to intentionally encourage the growth of taxa such as hazel (Corylus), but that also promoted the establishment of pioneer plants such as mugwort (Artemisia) and bracken (Pteridium).
  •  
21.
  • Blaesild, Paulina, 1994, et al. (författare)
  • Early Holocene vegetation development at Mesolithic fen dwelling sites in Dagsmosse, south-central Sweden, and its implications for understanding environment–human dynamics at various scales
  • 2024
  • Ingår i: Palaeogeography, Palaeoclimatology, Palaeoecology. - 0031-0182. ; 641
  • Tidskriftsartikel (refereegranskat)abstract
    • Recent discoveries of several Mesolithic sites within the Dagsmosse Basin, south-central Sweden, offer an opportunity to study the lifestyle and skillsets of Mesolithic hunter-gatherer-fishers operating in wetland environments. In this paper, we present a combined archaeological and palaeoecological analysis of a Mesolithic fenland environment using Repetitive-Proxy Pollen Analysis (RPPA) of early Holocene sequences. Based on comparison of stratigraphic profiles from two cores within the basin, we infer that the variance in pollen composition and anthropogenic signals reflect variability in human/vegetation interactions in the fenland, at different distances to the main human dwelling at Jussberg (9.0–8.2 ka cal BP). Our study describes the socio-environmental relations within the wetland and adjacent terrestrial areas, providing a basis for tracking changes in forager interactions with their surroundings during the Mesolithic. Pollen analysis is consistent with the previously established sequence of settlement phases and extent as well as providing new data concerning the anthropogenic impacts on plant communities within the wetland including the use, reuse, and management of vegetation taxa. Correlations between palaeoecological and archaeological data demonstrate that forager communities (i) prevailed in the open fenland landscape between 9.3 and 8.2 ka cal BP, (ii) actively altered taxa composition through small-scale clearings of pine (Pinus), birch (Betula) and sedges (Cyperaceae) and (iii) reduced canopy cover, possibly to intentionally encourage the growth of taxa such as hazel (Corylus), but that also promoted the establishment of pioneer plants such as mugwort (Artemisia) and bracken (Pteridium).
  •  
22.
  • Bornmalm, Lennart, 1956, et al. (författare)
  • Quantification of past environmental and biological processes by analysis of physical properties of fossils and fossil assemblages
  • 2013
  • Ingår i: Palaeogeography, Palaeoclimatology, Palaeoecology. - : Elsevier BV. - 0031-0182. ; 391
  • Tidskriftsartikel (refereegranskat)abstract
    • During the last four decades, reconstructions of past environments and biological processes based on fossil data have reached a remarkably high level of mathematical sophistication and statistical rigour. This development proceeded hand in hand with the increase in computing capacity and enabled researchers to extract new patterns from complex data, characterise uncertainty and formulate and test process-based hypotheses. From analysis of morphological evolution to reconstructions of past temperatures, between foraminifera and corals, climatological data, isotopes and assemblage counts, this field has been closely linked with the work of Professor Björn A. Malmgren, who has been one of the most prominent and innovative researchers in the field, applying cutting-edge mathematical techniques to Earth-science problems in a visionary manner that inspired several generations, and to whom this special issue is dedicated. Among the multitude of possibilities to analyse fossil data, applications in the field of paleoproxies are most numerous and most prominent. In this context, measurable properties of fossils are used as indirect representations of the state of the ambient environment acting on the organism that delivered the fossil and of the state of the environment to which the fossil has been exposed after the death of the organism. Two fundamental approaches to fossil proxies exist. The state of the environment can be reconstructed either from the chemical composition of the material of the fossil or from the physical properties of the fossil. The former is more prominent and has been the topic of many recent reviews, whereas the latter is conceptually more complex and less commonly used. The difference stems from the way in which the environmental signal is reflected in the proxy parameter. In geochemical proxies, passive incorporation or kinetic fractionation allows a more direct mechanistic interpretation of the signal, even though biological overprint is often present. Physical properties of fossils comprise characteristics of individual specimens, analysed by means of biometry (see Moller et al. and Quillévéré et al., in this issue), and properties of fossil assemblages, analysed by multivariate techniques (see Seidenkrantz et al. and Hernandez-Almeida et al., in this issue). Unlike geochemical proxies, these parameters are chiefly the result of biological processes such as individual growth, biomineralisation and population dynamics, which are inherently more difficult to link to environmental variables. This issue is dedicated to the interesting and somewhat overlooked field of proxies based on physical properties of fossils. It presents a selection of studies covering the main facets of quantitative analyses of fossil physical properties: morphometry and assemblage structure. It combines evaluation of uncertainty with proxy development and application for the understanding of past environmental processes. Although the concepts and approaches are equally applicable to any type of fossils, the examples in this issue all refer to microfossils. Due to their high abundance in small samples, microfossils have always been most amenable to quantitative treatment and they have also been the main object of study by Björn Malmgren. The difficulty to link shape and abundance of fossils to specific environmental variables results in a conceptually complex layer of uncertainty surrounding quantitative reconstructions based on physical properties of fossils. This complexity has multiple sources, beginning with the fidelity of taxonomic concepts, reflecting our ability to correctly identify biologically meaningful and ecologically homogenous taxa from morphological properties of fossils alone. This specific issue and its consequences are covered in contributions by Quillévéré et al. and Morard et al. in this issue. Collectively, this issue aims to reaffirm the central role that quantitative methods continue to play in analyses of fossil properties across an unexpectedly broad range of fields and to highlight the potential of this approach when sources of uncertainty are considered.
  •  
23.
  • Bornmalm, Lennart, 1956, et al. (författare)
  • Quantitative analysis of fossil data in the development and application of paleoproxies.
  • 2013
  • Ingår i: Palaeogeography, Palaeoclimatology, Palaeoecology. - 0031-0182. ; 391:Part A, s. 1-82
  • Tidskriftsartikel (refereegranskat)abstract
    • During the last four decades, reconstructions of past environments and biological processes based on fossil data have reached a remarkably high level of mathematical sophistication and statistical rigour. This development proceeded hand in hand with the increase in computing capacity and enabled researchers to extract new patterns from complex data, characterise uncertainty and formulate and test process-based hypotheses. From analysis of morphological evolution to reconstructions of past temperatures, between foraminifera and corals, climatological data, isotopes and assemblage counts, this field has been closely linked with the work of Professor Björn A. Malmgren, who has been one of the most prominent and innovative researchers in the field, applying cuttingedge mathematical techniques to Earth-science problems in a visionary manner that inspired several generations, and to whom this special issue is dedicated. Among the multitude of possibilities to analyse fossil data, applications in the field of paleoproxies are most numerous and most prominent. In this context, measurable properties of fossils are used as indirect representations of the state of the ambient environment acting on the organism that delivered the fossil and of the state of the environment to which the fossil has been exposed after the death of the organism. Two fundamental approaches to fossil proxies exist. The state of the environment can be reconstructed either from the chemical composition of the material of the fossil or from the physical properties of the fossil. The former is more prominent and has been the topic of many recent reviews, whereas the latter is conceptually more complex and less commonly used. The difference stems from the way in which the environmental signal is reflected in the proxy parameter. In geochemical proxies, passive incorporation or kinetic fractionation allows a more direct mechanistic interpretation of the signal, even though biological overprint is often present. Physical properties of fossils comprise characteristics of individual specimens, analysed by means of biometry (see Moller et al. and Quillévéré et al., in this issue), and properties of fossil assemblages, analysed by multivariate techniques (see Seidenkrantz et al. and Hernandez-Almeida et al., in this issue). Unlike geochemical proxies, these parameters are chiefly the result of biological processes such as individual growth, biomineralisation and population dynamics, which are inherently more difficult to link to environmental variables. This issue is dedicated to the interesting and somewhat overlooked field of proxies based on physical properties of fossils. It presents a selection of studies covering the main facets of quantitative analyses of fossil physical properties: morphometry and assemblage structure. It combines evaluation of uncertainty with proxy development and application for the understanding of past environmental processes. Although the concepts and approaches are equally applicable to any type of fossils, the examples in this issue all refer to microfossils. Due to their high abundance in small samples, microfossils have always been most amenable to quantitative treatment and they have also been the main object of study by Björn Malmgren. The difficulty to link shape and abundance of fossils to specific environmental variables results in a conceptually complex layer of uncertainty surrounding quantitative reconstructions based on physical properties of fossils. This complexity has multiple sources, beginning with the fidelity of taxonomic concepts, reflecting our ability to correctly identify biologically meaningful and ecologically homogenous taxa from morphological properties of fossils alone. This specific issue and its consequences are covered in contributions by Quillévéré et al. and Morard et al. in this issue. Collectively, this issue aims to reaffirm the central role that quantitative methods continue to play in analyses of fossil properties across an unexpectedly broad range of fields and to highlight the potential of this approach when sources of uncertainty are considered.
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24.
  • Borromei, Ana Maria, et al. (författare)
  • Multiproxy record of Holocene paleoenvironmental change, Tierra del Fuego, Argentina
  • 2010
  • Ingår i: Palaeogeography, Palaeoclimatology, Palaeoecology. - 0031-0182. ; 286:1-2, s. 1-6
  • Tidskriftsartikel (refereegranskat)abstract
    • We interpret Holocene environmental conditions in a subantarctic high Andean valley from palynological and diatom analysis, peat stratigraphy, and local geomorphology. The multiproxy data from Las Cotorras mire (54° 41′ 13″ S; 68° 02′ 51″ W; 420 m a.s.l.) indicate the development of a soligenous mire, as a result of a fine grained tephra layer deposition over the mineral soils sometime prior to 8000 cal yr BP. The paleoecological conditions in the mire after 8000 cal yr BP show a rapid succession from a limnic to a telmatic stage as the mire is colonized by sedges (Cyperaceae) and herbaceous communities. The upland vegetation changed from cushion and shrub heaths to an expansion of Nothofagus forest at high altitudes after 6500 cal yr BP. The peat is interbedded with clastic sediment that originates from mass wasting events or floods. These depositional changes affected the mire ecosystem water-table level and nutrient status (oligotrophic and/or eutrophic conditions). Maxima in total pollen influx at about 2800, 1100 and 700 cal yr BP coincide with heightened mineral flux, and these changes are related to precipitation and slope processes. The major vegetational change registered in the pollen record is the decline of Nothofagus pollen after 1000 cal yr BP, which reaches a minimum between ca. 680 and 300 cal yr BP. This minimum was likely caused by cool, wet conditions that coincided with the Little Ice Age (LIA) in the Southern Hemisphere. Our results indicate the sensitivity of subantarctic Nothofagus forest and mire ecosystems to changes during the Holocene.
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25.
  • Bowman, Chelsie N., et al. (författare)
  • Integrated sedimentary, biotic, and paleoredox dynamics from multiple localities in southern Laurentia during the late Silurian (Ludfordian) extinction event
  • 2020
  • Ingår i: Palaeogeography, Palaeoclimatology, Palaeoecology. - : Elsevier BV. - 0031-0182. ; 553
  • Tidskriftsartikel (refereegranskat)abstract
    • The Silurian was a time of major climatic transition punctuated by multiple biotic crises and global carbon cycle perturbations. The most severe of these biotic events was the late Silurian (Ludfordian) Lau/Kozlowskii extinction event (LKE) and the associated Lau carbon isotope excursion (CIE). Although the extinction event and Lau CIE are globally documented, the only records thus far of local and global marine paleoredox conditions through this interval are from a single region in Scandinavia. Here we examine four sections along a bathymetric transect of mixed carbonate-siliciclastic sediments from western Tennessee, USA. A novel approach using a multi-proxy dataset combining high-resolution geochemical data and microfacies analyses from multiple localities explores the possibilities of local/regional-scale redox heterogeneities during a time of widespread environmental upheaval on a global scale. Paired positive excursions recorded in carbonate carbon isotopes and carbonate-associated sulfate sulfur isotopes support recent work from carbonate and siliciclastic successions from Scandinavia, suggesting a global enhancement of organic carbon and pyrite burial driven by an expansion of euxinic (anoxic and sulfidic water column) conditions in the oceans during the mid-Ludfordian. Furthermore, positive excursions in organic carbon isotopes and pyrite sulfur isotopes reflect the global changes in redox. Stratigraphic trends in I/Ca ratios imply a local expansion of low-oxygen conditions, with low, but non-zero values during the rising limb and peak of the CIE. The fossil assemblages vary across the shelf and through the CIE interval. Stratigraphic changes in fossil assemblages and I/Ca are closely associated with local and global changes in oxygenation and sea level during the mid-Ludfordian. The collective data indicate significant biotic reorganization in response to changes in marine redox conditions and in conjunction with sea-level variation during the LKE interval, but detailed macroscopic biodiversity is currently unconstrained for this region.
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26.
  • Bradák, Balázs, et al. (författare)
  • Magnetic susceptibility in the European Loess Belt : New and existing models of magnetic enhancement in loess
  • 2021
  • Ingår i: Palaeogeography, Palaeoclimatology, Palaeoecology. - : Elsevier. - 0031-0182 .- 1872-616X. ; 569
  • Tidskriftsartikel (refereegranskat)abstract
    • Magnetic susceptibility measurements play a key role in Quaternary studies. Magnetic proxies, such as low field and frequency-dependent magnetic susceptibility, are widely applied in the reconstruction of terrestrial paleoclimate, e.g., in the study of loess-paleosol successions. In general, the interpretation of loess magnetic susceptibility signals is based on two commonly accepted models: the pedogenic magnetic enhancement and wind-vigour models. However, there are an increasing number of cases where such models cannot be used. These cases show unusual relationships between the two common loess magnetic susceptibility proxies: low field and frequency-dependent magnetic susceptibility. Such relationships have been attributed to various phenomena including the dissolution of fine-grain minerals and the formation of ultrafine magnetic rims on the surface of coarser grains by weathering. Despite the growing number of these exceptional cases of magnetic enhancement, our knowledge about the occurrence and potential causes of the unusual behaviour of magnetic susceptibility parameters is still limited. This, in turn, hinders the wider application of magnetic susceptibility parameters in loess. To fill this knowledge gap, magnetic susceptibility data of various profiles from the European Loess Belt were collected and compared to reveal various enhancement trends in loess. Along with the analysis of magnetic susceptibility parameters, combined scanning electron microscopy (SEM) and rock magnetic analyses were applied to samples from the Paks loess sequence in Hungary to describe some of the irregular cases, notably the cause of increasing frequency-dependent susceptibility in non-altered sediments. Analysis of loess, paleosol and common mineral samples separated from loess (e.g., muscovite) revealed that various features may be responsible for these increasing frequency-dependent susceptibility values: i) surface weathering (maghemitization) of coarser detrital grains, ii) nanofragmentation by physical weathering and iii) the appearance of significant amounts of ultrafine magnetic inclusions in micas. These special modes of magnetic enhancement of loess do not undermine the importance of the basic theories suggested above, but rather provide three mechanisms that account for some of the increasing number of unusual cases. To aid in the wider and more accurate use of magnetic susceptibility parameters in loess, we review the current magnetic enhancement models with special emphasis on the identification of unusual trends in magnetic enhancement and understanding their drivers.
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27.
  • Bradák, B., et al. (författare)
  • Potential drivers of disparity in early Middle Pleistocene interglacial climate response over Eurasia
  • 2022
  • Ingår i: Palaeogeography, Palaeoclimatology, Palaeoecology. - : Elsevier. - 0031-0182 .- 1872-616X. ; 585
  • Tidskriftsartikel (refereegranskat)abstract
    • Poor understanding of the differential evolution of interglacial climate over various regions in Eurasia greatly limits our ability to predict the specific local impacts of future climate change. Here we demonstrate starkly opposing trends in interglacial intensities in Asia and Europe over the early Middle Pleistocene and Mid-Brunhes Transitions based on the study of various climate proxies in the Paks loess record (Hungary), a key profile in the European Loess Belt. These contrasting climate trends imply major but unexplained differences in the regional response of Quaternary climate to shifts in forcing mechanisms during two major reorganizations of Earth's climate across Eurasia. Using new rock magnetic datasets from the Paks record we suggest that the changing dominance of Mediterranean, Atlantic (Westerlies) and continental air masses under the influence of the quasi permanent high pressure centres over the Fennoscandian ice sheet played a key role in the observed differences in the evolution of early Middle Pleistocene climate. We also propose that the intensification of the early Middle Pleistocene glaciation of Central Asian mountains may have strengthened and shifted the Siberian High west-ward on multi-millennial/orbital timescales, which in turn forced geographically contrasting expressions of the MIS 19 to 11 interglacials in Eurasia. This is the first coherent explanation for the geographically diverse response of regional climate to the early Middle Pleistocene climate transitions and points to the clear role of global cooling and expanded mid-latitude glaciers in driving these events.
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28.
  • Brown, Caleb M., et al. (författare)
  • Evidence for taphonomic size bias in the Dinosaur Park Formation (Campanian, Alberta), a model Mesozoic terrestrial alluvial‐paralic system
  • 2013
  • Ingår i: Palaeogeography, Palaeoclimatology, Palaeoecology. - : Elsevier. - 0031-0182 .- 1872-616X. ; 372:SI, s. 108-122
  • Tidskriftsartikel (refereegranskat)abstract
    • A study of the distribution of dinosaurian body masses in the Dinosaur Park Formation (DPF; Campanian; southern Alberta), reveals a prominent negative skew; a pattern distinct from those of modern terrestrial faunas. We find a direct and robust correlation between taxon size (estimated live body mass) and known completeness. There is a clear dichotomy between large and small-bodied taxa at around 60 kg, in which taxa less than 60 kg are significantly less complete (mean completeness = 7.6%) than those with an estimated mass of 60 kg or greater (mean = 78.2%). Along with completeness, there is also a strong association of body size and taphonomic mode, with small taxa known largely from isolated and occasionally associated remains, and large taxa known from articulated skeletons. In addition, there is a significant correlation between taxon body mass and both date of discovery and of description, with taxa < 60 kg taking an average of 65.9 and 75.6 years to discover and describe, respectively, compared to 33.6 and 34.1 years for taxa > 60 kg. The rates of both cumulative discovery and description for large taxa are best described by a logarithmic curve nearing an asymptote, whereas small taxa show either a linear or power increase through time. This suggests that our current knowledge of the large-bodied dinosaur assemblage is reasonably representative of the true biological fauna with few discoveries likely to be made in the future. However, small taxa are greatly underestimated in both their diversity and abundance, with many more potential discoveries to be made. Given that (1) the sedimentary deposits and fossil assemblages in the DPF together represent one of the best studied examples of a Mesozoic alluvial‐paralic (terrestrial) ‘palaeoecosystem,’ and (2) similar patterns have been suggested (but not documented) for other Mesozoic terrestrial ecosystems in the Western Interior of North America, we suggest that this pattern of size bias may typify vertebrate fossil assemblages in terrestrial Mesozoic systems. If so, such biases must be considered before patterns of diversity in dinosaur communities through time can be considered accurate, or used to compare and interpret Mesozoic palaeoecosystems.
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29.
  • Brylka, Karolina, et al. (författare)
  • Biogenic silica accumulation and diatom assemblage variations through the Eocene-Oligocene Transition : A Southern Indian Ocean versus South Atlantic perspective
  • 2024
  • Ingår i: Palaeogeography, Palaeoclimatology, Palaeoecology. - 0031-0182. ; 636
  • Tidskriftsartikel (refereegranskat)abstract
    • It is widely interpreted that there is a significant link between climate cooling at the Eocene-Oligocene Transition(EOT; ~34 Ma) and subsequent diatom proliferation in the world’s oceans during the mid to late Cenozoic. Yet,our understanding of biogenic silica flux through the EOT interval is based on limited data from a few sites, andthere are many complications in making a meaningful comparison based on biogenic silica concentration datagenerated using different techniques. Here, we present new biogenic opal flux and diatom assemblage recordsacross EOT from Ocean Drilling Program Site 748 (Southern Kerguelen Plateau, southern Indian Ocean), inaddition to new biogenic opal flux records from the South Atlantic (Deep Sea Drilling Project Site 511, FalklandPlateau and Ocean Drilling Program Site 1090, Agulhas Ridge). Observed opal flux shifts and variability at Site748 are consistent with published data from nearby Site 744; both sites show considerable shifts in biogenic opalaccumulation rates corresponding to shifts in published benthic oxygen isotope records through the EOT. Incontrast, our new opal flux record for Site 511, derived from biogenic opal concentration measurements viaspectrophotometry, differs from the published record derived from insoluble residues, whereas new datagenerated for Site 1090 are generally consistent with previously published flux reconstructions. The SouthAtlantic biogenic opal flux records, however, are dissimilar from one another, and both are dissimilar from theSouthern Indian Ocean records. Also, the taxonomic composition of the diatom assemblages from Sites 511, 748and 1090 display considerable differences, with hemiauloids and rhizosolenids – generally inferred as indicativeof oligotrophic conditions – being the dominant diatoms at the Southern Kerguelen Plateau (Site 748). Publishedrecords show that hemiauloid taxa are absent from the earliest Oligocene interval at Site 1090, which is widelyseen as a record of deposition from nutrient-rich waters sustaining abundant diatom assemblages. These differencesin diatom assemblages testify to regional differences in nutrient concentrations. In particular, the timingof biogenic opal flux pulses between Sites 1090 and 748 imply a shift in the locus of opal deposition to areasfurther south in the Southern Ocean across the EOT, likely related to proto-ACC development and strengtheningof frontal boundaries. Thus, combined geochemical and micropaleontological evidence points to a regionallyvariable rather than a global, unified opal flux response to climate cooling through the Eocene-OligoceneTransition.
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30.
  • Burdett, Heidi, et al. (författare)
  • Using coralline algae to understand historic marine cloud cover
  • 2011
  • Ingår i: Palaeogeography, Palaeoclimatology, Palaeoecology. - : Elsevier. - 0031-0182 .- 1872-616X. ; 302:1-2, s. 65-70
  • Tidskriftsartikel (refereegranskat)abstract
    • Free-living coralline algae lay down growth bands formed by areas of more and less calcified cells which, in certain species, are associated with winter and summer growth respectively. Band width and cell calcification of Lithothamnion glaciale from Scotland were compared to annual and seasonal cloud cover and sea surface temperature (SST). There was a negative relationship between summer calcification (the degree of cellular carbonate infilling) and winter cloud cover. Annual and summer SST were also negatively related to summer calcification. This indicates that summer calcification may be affected by the previous winter's cloud cover and that summer's/year's SST. No relationships between band width and cloud cover were observed. A cloud cover hindcast using summer calcification and SST indicated a modest rise in cloud cover trends from 1910 to 2006 and a 12 (mean) year cyclicity in cloud cover, however, the latter may be associated with other site-specific factors. This study demonstrates the utility of densitometric algochronology in understanding marine temperature and cloud cover histories. 
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31.
  • Byrne, Hannah, et al. (författare)
  • Coprolite diversity reveals a cryptic ecosystem in an early Tournaisian lake in East Greenland : Implications for ecosystem recovery after the end-Devonian extinctio
  • 2022
  • Ingår i: Palaeogeography, Palaeoclimatology, Palaeoecology. - : Elsevier. - 0031-0182 .- 1872-616X. ; 605
  • Tidskriftsartikel (refereegranskat)abstract
    • The early Tournaisian (Carboniferous) stage represents a key episode in the evolution of vertebrates. It follows the end-Devonian Hangenberg extinction event, which led to a major perturbation to both terrestrial and aquatic vertebrate ecosystems, and resulted in a significant restructuring of assemblages. However, few faunal associ-ations of this age have been described, and our understanding of faunal turnover across the Devonian -Carboniferous boundary remains poor. In this paper, we present an analysis of coprolite material from early Tournaisian lacustrine facies at Celsius Bjerg on Ymer o in East Greenland, which overlies the world-famous latest Devonian tetrapod-bearing localities. Fifty-five coprolite specimens (defined as a single coprolite or a piece of shale containing coprolites) were analysed using propagation phase-contrast synchrotron micro -tomography (PPC-SR mu CT). Through a study of external morphology, shape and size combined with information about internal structures, we categorise coprolite morphotypes, and interpret their origin. Notably, we identify a greater number of coprolite morphotypes compared to vertebrate taxa known from skeletal material, indicating the existence of a cryptic ecosystem that has not yet been recovered as body fossils. Vertebrate diversity in the immediate aftermath of the end-Devonian extinction is inferred to have been higher than expected, and might have included transient faunal elements within an open system, perhaps involving marine basin connections. Our results show that coprolites offer an alternative fossil data source, revealing diversity that is otherwise not always captured by the skeletal record.
  •  
32.
  • Calner, Mikael, et al. (författare)
  • Palaeokarst evidence for widespread regression and subaerial exposure in the middle Katian (Upper Ordovician) of Baltoscandia: significance for global climate.
  • 2010
  • Ingår i: Palaeogeography, Palaeoclimatology, Palaeoecology. - : Elsevier BV. - 1872-616X .- 0031-0182. ; 296:3-4, s. 235-247
  • Tidskriftsartikel (refereegranskat)abstract
    • We report on widespread and contemporary palaeokarst in the middle Katian (Upper Ordovician) of Sweden, Estonia and Latvia, the first major palaeokarst horizon to be reported from the Ordovician of Baltoscandia. The solution features occurwithin a fewmetres of thick zone of limestone immediately belowthe widespread Fjäcka Shale and are related to an unconformity with preserved palaeorelief in the Slandrom Limestone in Sweden and the time-equivalent Saunja Formation in Estonia and Latvia. Facies evidence for a karst origin comes fromseveral outcrops and core sections and includes 1) frequent karren-likemorphologies interpreted as ‘Swiss-cheese’ karst [sensu Baceta et al., 2001], 2) local occurrences of solution/collapse breccia, 3) presence of bladed pseudospar crystals in solution cavities, and 4) carbon isotope values indicating meteoric influence to the succession. These findings are herein put in context with previously reported, large-scale erosional channels that may cut down several tens of metres below the Fjäcka Shale in the subsurface Baltic Sea area, and with regional, anomalous thickness variations in the Slandrom Limestone and Saunja Formation, all together forming strong support for regional exposure of the Baltoscandian continent in the middle Katian. High-resolution stable isotopic data show that the regression and lowstand of sea-level overlap with theWaynesville carbon isotope excursion. It resulted in basin-wide cessation of carbonate production near the Amorphognathus superbus and A. ordovicicus conodont zonal boundary. The contemporary development of palaeokarst in different confacies belts of the basin suggests that this was an extraordinary sea-level lowstand, herein interpreted as reflecting a middle Katian glaciation.
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33.
  • Chen, Junyuan, et al. (författare)
  • Early Cambrian Yangtze Plate Maotianshan Shale macrofauna biodiversity and the evolution of predation
  • 2007
  • Ingår i: Palaeogeography, Palaeoclimatology, Palaeoecology. - : Elsevier BV. - 0031-0182 .- 1872-616X. ; 254:1-2, s. 250-272
  • Forskningsöversikt (refereegranskat)abstract
    • The large number of soft-part preserved fossils from the Lower Cambrian Maotianshan Shale (Chengjiang) Lagerstätten suggests particularly favourable conditions for a rich life on the shelf-zone sea bottom of the Yangtze Plate, China. This high degree of biodiversity opens an excellent window into the early radiation phase of Metazoa and represents a significant data source for the study of adaptive strategies among early animals. Feeding and locomotion are the main life strategies of organisms we investigated with regard to two major benthic macrofaunal components of the Maotianshan Shale biota, the nemathelminths and the arthropods. Our attempt was to test whether food, feeding and locomotory strategies of the benthic Lower Cambrian shallow-water communities were as diversified as it appears from the morphological diversity of the organisms present. Two major types of feeders can be discerned: suspension/micro-particle feeders – mostly epibenthic sedentary taxa – and larger-particle feeders, living in benthic to bentho-pelagic realms. Scant evidence exists for exclusive vegetarians, fungi eaters, biomat utilizers and for in-faunal vertical burrowers or grazers (bioturbators). Predation, in a wider sense, seems to be a, if not the, major feeding mode among metazoans. Nemathelminths and arthropods are amongst the best examples. In the benthic shallow-water regime, as exposed by the Maotianshan Shale biota, animals and their ontogenetic stages were the most suitable and readily available food source. At least for arthropods, we propose that improvement of predatory strategies was paralleled by the enhancement of locomotory and food manipulation structures. Accumulating evidence of late Precambrian to Early Cambrian metazoans exposing diverse morphologies and life styles indicates that, on the large scale, phylogenesis progressed gradually in the Late Precambrian. This renders an “explosive” radiation of Metazoa unlikely.
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34.
  • Clements, Jeff C., et al. (författare)
  • Ocean acidification and molluscan shell taphonomy: Can elevated seawater pCO(2) influence taphonomy in a naticid predator-prey system?
  • 2018
  • Ingår i: Palaeogeography Palaeoclimatology Palaeoecology. - : Elsevier BV. - 0031-0182. ; 507, s. 145-154
  • Tidskriftsartikel (refereegranskat)abstract
    • The size and frequency of gastropod drill holes in shells of their prey are common indicators of predator-prey ecology in the fossil record. Taphonomic processes occurring after predation, however, can influence the preservation of shells in a given fossil assemblage and can thus influence ecological inferences based on preserved shells. To determine if ocean acidification (OA) has the capacity to influence prey shell taphonomy in a gastropod drilling predation system, we tested for effects of elevated pCO(2) on dissolution rates, breakage force, and drill hole diameters in non-fragmented shells of two prey species of the cannibalistic naticid gastropod, Euspira heros. Drilled and non-drilled shells of Littorina littorea and E. heros were exposed to control (similar to 300 mu atm) and elevated (similar to 800 and 4000 mu atm) pCO(2) treatments for five weeks. Dry shell weight and drill hole diameter (outer and inner) were recorded for individual shells before and after exposure; the force required for shell breakage was recorded at the end of the exposure period. Shell mass loss in 800 and 4000 mu atm, respectively, were similar to 1 and 7% for E. heros, and similar to 0 and 4% for L. littorea, compared to similar to 0% in the control for both species. Shell breakage force was unaffected by elevated pCO(2), but was affected by species and drill hole presence, with E. heros shells requiring a force of similar to 220 and 269 Newtons in drilled and non-drilled shells, respectively, compared to similar to 294 and 415 Newtons in L. littorea. At 4000 mu atm, outer drill hole diameter significantly increased by similar to 12% for E. heros, while inner drill hole diameter significantly increased by similar to 13% in E. heros and similar to 10% in L. littorea. Ultimately, this study provides the first documentation of molluscan shell taphonomy in the context of OA for a gastropod drilling predation system and sets the stage for future research.
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35.
  • Cobianchi, M., et al. (författare)
  • Effects of oceanic circulation and volcanic ash-fall on calcite dissolution in bathyal sediments from the SW Pacific Ocean over the last 550 ka
  • 2015
  • Ingår i: Palaeogeography, Palaeoclimatology, Palaeoecology. - : Elsevier BV. - 0031-0182 .- 1872-616X. ; 429, s. 72-82
  • Tidskriftsartikel (refereegranskat)abstract
    • The effects on calcite dissolution of both oceanic circulation and volcanic ash-fall were evaluated in lower bathyal sediments over the last 550 ka record from core MD 97-2114, recovered on the northern slope (depth of 1936 m, in the Pacific Deep Water, PDW) of the Chatham Rise (east of New Zealand, SW Pacific Ocean). This area has been impacted by changes in glacial/interglacial circulation and ocean chemistry as well as by the explosive volcanic activity of the Taupo Volcanic Zone. Several micro-paleontological dissolution proxies, based on planktonic foraminifera and calcareous nannofossils, were analysed in order to evaluate the calcite dissolution of the deep-sea sediments. These were compared with a couple of proxies of primary productivity (benthic foraminiferal epifaunal/infaunal ratio and delta C-13(benthic) (foraminifera)) and the abundance of volcanic glass. The dissolution proxy data from MD 97-2114 were compared with two nearby ODP sites, ODP 1123 (3290 m deep, bathed by the lower Circumpolar Deep Water, LCDW) and ODP 1125 (1365 m deep, bathed by the Antarctic Intermediate Water, AAIW). The results suggest: (1) the calcite dissolution/preservation cycles at all three core sites show Glacial-Interglacial (G-I) periodicities that match the previously described "Pacific-style" CaCO3 cycles; (2) several short-term dissolution events do not follow this general scheme and occur following tephra deposition. The dissolution related to the tephra deposition seems to have mostly affected calcareous nannofossils, thus we hypothesise that the ash-fall induced a temporary reduction of the surface water pH (below 7.8), which affected the coccolithophores that inhabit the surface waters. (3) Other short-term dissolution events (1000 years) are unrelated to tephra deposition and are possibly driven by the slowing of deep-sea circulation and a reduced Deep Western Boundary Current (DWBC). This lead to the dominance of older, more corrosive Pacific Deep Water (POW) flowing in to the region, resulting in coeval dissolution episodes at all three core sites (depth range from 1365 to 3290 m).
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36.
  • Cohen, Timothy, et al. (författare)
  • Late Quaternary mega-lakes fed by the northern and southern river systems of central Australia : varying moisture sources and increased continental aridity
  • 2012
  • Ingår i: Palaeogeography, Palaeoclimatology, Palaeoecology. - : Elsevier BV. - 0031-0182 .- 1872-616X. ; 356:Special Issue, s. 89-108
  • Tidskriftsartikel (refereegranskat)abstract
    • Optically stimulated and thermoluminescence ages from relict shorelines, along with accelerator mass spectrometer 14C ages from freshwater molluscs reveal a record of variable moisture sources supplied by northern and southern river systems to Lake Mega-Frome in southern central Australia during the late Quaternary. Additional lacustrine, palynological and terrestrial proxies are used to reconstruct a record that extends back to 105 ka, confirming that Lakes Mega-Frome and Mega-Eyre were joined to create the largest system of palaeolakes on the Australian continent as recently as 50–47 ka. The palaeohydrological record indicates a progressive shift to more arid conditions, with marked drying after 45 ka. Subsequently, Lake Mega-Frome has filled independently at 33–31 ka and at the termination of the Last Glacial Maximum to volumes some 40 times those of today. Further sequentially declining filling episodes (to volumes 25–10 those of today) occurred immediately prior to the Younger Dryas stadial, in the mid Holocene and during the medieval climatic anomaly. Southern hemisphere summer insolation maxima are a poor predictor of palaeolake-filling episodes. An examination of multiple active moisture sources suggests that palaeolake phases were driven independently of insolation and at times by some combination of enhanced Southern Ocean circulation and strengthened tropical moisture sources.
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37.
  • Cortese, G., et al. (författare)
  • Late Pleistocene-Holocene radiolarian paleotemperatures in the Norwegian Sea based on artificial neural networks
  • 2005
  • Ingår i: Palaeogeography Palaeoclimatology Palaeoecology. - : Elsevier BV. - 0031-0182. ; 224:4, s. 311-332
  • Tidskriftsartikel (refereegranskat)abstract
    • Artificial Neural Networks (ANN) were trained by using an extensive radiolarian census dataset from the Nordic (Greenland, Norwegian, and Iceland) Seas. The regressions between observed and predicted Summer Sea Temperature (SST) indicate that lower error margins and better correlation coefficients are obtained for 100 m (SST100) compared to 10 m (SST10) water depth, and by using a subset of species instead of all species. The trained ANNs were subsequently applied to radiolarian data from two Norwegian Sea cores, HM 79-4 and MD95-2011, for reconstructions of SSTs through the last 15,000 years. The reconstructed SST is quite high during the Bolling-Allerod, when it reaches values only found later during the warmest phase of the Holocene. The climatic transitions in and out of the Younger Dryas are very rapid and involve a change in SST100 of 6.2 and 6.8 degrees C, taking place over 440 and 140 years, respectively. SST100 remains at a maximum during the early Holocene, and this Radiolarian Holocene Optimum Temperature Interval (RHOTI) predates the commonly recognized middle Holocene Climatic Optimum (HCO). During the 8.2 ka event, SST100 decreases by ca. 3 degrees C, and this episode marks the establishment of a cooling trend, roughly spanning the middle Holocene (until ca. 4.2 ka). Successively, since then and through the late Holocene, SST100 follows instead a statistically significant warming trend. The general patterns of the reconstructed SSTs agree quite well with previously obtained results based on application of Imbrie and Kipp Transfer Functions (IKTF) to the same two cores for SST0. A statistically significant cyclic component of our SST record (period of 278 years) has been recognized. This is close to the de Vries or Suess cycle, linked to solar variability, and documented in a variety of other high-resolution Holocene records. (c) 2005 Elsevier B.V. All rights reserved.
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38.
  • Cramer, Bradley D., et al. (författare)
  • Paleobiogeography, high-resolution stratigraphy, and the future of Paleozoic biostratigraphy: Fine-scale diachroneity of the Wenlock (Silurian) conodont Kockelella walliseri
  • 2010
  • Ingår i: Palaeogeography, Palaeoclimatology, Palaeoecology. - : Elsevier BV. - 0031-0182 .- 1872-616X. ; 294:3-4, s. 232-241
  • Konferensbidrag (refereegranskat)abstract
    • The Wenlock Epoch of the Silurian Period has become one of the chronostratigraphically best-constrained intervals of the Paleozoic. The integration of multiple chronostratigraphic tools, such as conodont and graptolite biostratigraphy, sequence stratigraphy, and delta C-13(carb) chemostratigraphy, has greatly improved global chronostratigraphic correlation and portions of the Wenlock can now be correlated with precision better than +/- 100 kyr. Additionally, such detailed and integrated chronostratigraphy provides an opportunity to evaluate the fidelity of individual chronostratigraphic tools. Here, we use conodont biostratigraphy, sequence stratigraphy and carbon isotope (delta C-13(carb)) chemostratigraphy to demonstrate that the conodont Kockelella walliseri, an important guide fossil for middle and upper Sheinwoodian strata (lower stage of the Wenlock Series), first appears at least one full stratigraphic sequence lower in Laurentia than in Baltica. Rather than serving as a demonstration of the unreliability of conodont biostratigraphy, this example serves to demonstrate the promise of high-resolution Paleozoic stratigraphy. The temporal difference between the two first occurrences was likely less than 1 million years, and although it is conceptually understood that speciation and colonization must have been non-instantaneous events, Paleozoic paleobiogeographic variability on such short timescales (tens to hundreds of kyr) traditionally has been ignored or considered to be of little practical importance. The expansion of high-resolution Paleozoic stratigraphy in the future will require robust biostratigraphic zonations that embrace the integration of multiple chronostratigraphic tools as well as the paleobiogeographic variability in ranges that they will inevitably demonstrate. In addition, a better understanding of the paleobiogeographic migration histories of marine organisms will provide a unique tool for future Paleozoic paleoceanography and paleobiology research. (C) 2010 Elsevier B.V. All rights reserved.
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39.
  • Cunningham, Laura, et al. (författare)
  • Climatic variability during the last interglacial inferred from geochemical proxies in the Lake El'gygytgyn sediment record
  • 2013
  • Ingår i: Palaeogeography, Palaeoclimatology, Palaeoecology. - : Elsevier. - 0031-0182 .- 1872-616X. ; 386, s. 408-414
  • Tidskriftsartikel (refereegranskat)abstract
    • The Last Interglacial Period (LIP) is often regarded as a good analogue for potential climatic conditions under predicted global warming scenarios. Despite this, there is still debate over the nature, duration and frequency of climatic changes during this period. One particularly contentious issue has been the apparent evidence of climatic instability identified in many marine cores but seemingly lacking from many terrestrial archives, especially within the Arctic, a key region for global climate change research. In this paper, geochemical records from Lake El'gygytgyn, north-eastern Russia, are used to infer past climatic changes during the LIP from within the high Arctic. With a sampling resolution of similar to 20-similar to 90 years, these records offer the potential for detailed, high-resolution palaeoclimate reconstruction. This study shows that the LIP commenced in central Chukotka similar to 129 thousand years ago (ka), with the warmest climatic conditions occurring between similar to 128 and 127 ka before being interrupted by a short-lived cold reversal. Mild climatic conditions then persisted until similar to 122 ka when a marked reduction in the sedimentation rate suggests a decrease in precipitation. A further climatic deterioration at similar to 118 ka marks the return to glacial conditions. This study highlights the value of incorporating several geochemical proxies when inferring past climatic conditions, thus providing the potential to identify signals related to environmental change within the catchment. We also demonstrate the importance of considering how changes in sedimentation rate influence proxy records, in order to develop robust palaeoenvironmental reconstructions. (C) 2013 Elsevier B.V. All rights reserved.
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40.
  • Dahlqvist, Peter, et al. (författare)
  • Late Ordovician palaeoceanographic changes as reflected in the Hirnantian-early Llandovery succession of Jamtland, Sweden
  • 2004
  • Ingår i: Palaeogeography, Palaeoclimatology, Palaeoecology. - : Elsevier BV. - 1872-616X .- 0031-0182. ; 210:2-4, s. 149-164
  • Tidskriftsartikel (refereegranskat)abstract
    • A study of the Upper Ordovician-Lower Silurian strata in Jamtland, central Sweden, shows that large-scale changes in shelf deposition took place close to the systems boundary. These changes include unconformity development and the replacement of a siliciclastic shelf with a carbonate-dominated shelf, suggesting the interaction of allocyclic controls such as changing eustatic sea-level and climate. The 6-m-thick Ede Formation is a key lithosome for interpretation of this transition. Its sediments were deposited in the Caledonian foreland basin, situated east of the closing Iapetus Ocean on the western margin of the Baltic craton. A major part of the late. Caradoc to late Ashgill (into the Hirnantian) was characterised by continuous and uniform deposition over wide areas (Kogsta Formation), whereas erosional surfaces and complex lateral facies relationships characterise the Ordovician-Silurian boundary strata (Ede Formation and lateral equivalents). The Ede Formation represents the end of terrigenous deposition, which in the middle Aeronian was followed by regional expansion of carbonate deposition (Berge Formation). A syn-sedimentary erosional surface, with at least I in of relief locally, forms the lower boundary of the Ede Formation. This surface is overlain by two types of conglomerate. Lower parts of the Ede Formation consist of medium to thick-bedded quartzites. A second erosional surface with only minor (few centimetres) relief occurs on top of these quartzites. The upper parts of the Ede Formation consist of a thin, basal favositid biostrome overlain by thin bedded, calcareous sandstones, limestones and intensely bioturbated shales. Analysis of stratigraphic boundaries and the facies succession suggests that the lower Ede Formation represents a major downward shift in coastal onlap and by-pass sedimentation that created the lower erosional surface. The erosional surface in the middle of the Ede Formation is inferred to have formed during the subsequent maximum lowstand or as a ravinement surface, and is interpreted as an unconformity. The succession is subdivided into four facies associations, each corresponding to a specific systems tract: (a) a Shale-Siltstone Association (uppermost Kogsta Formation), deposited during a highstand situation in mid-outer shelf areas; (b) a Quartzite Association (the lower Ede Formation), deposited during forced regression in a shoreface environment; (c) a Mixed Carbonate-Siliciclastic Association (the upper Ede Formation), deposited during transgression in a wave-dominated, proximal shelf environment when elastic supply was reduced; and (d) a Micritic Limestone Association (lowermost Berge Formation), deposited during a second highstand situation in a low-energy, offshore environment. Conodont data, together with a previously reported Hirnantia fauna, constrain the position of the Ordovician-Silurian boundary to the lower 1.65 m of the Ede Formation, or less likely, to the uppermost metre of the underlying Kogsta Formation, i.e., within a 2.65-m-thick uncertainty interval. The base of the Berge Formation is about 4 m above the top of the uncertainty interval, and is dated as being mid-Aeronian in age, suggesting condensation and/or a hiatus close to, or at, the Ordovician-Silurian boundary. These data tie the unconformity and the regional facies change from a siliciclastic to a carbonate-dominated shelf to Late Ordovician-Early Silurian eustatic and climatic changes. (C) 2004 Elsevier B.V. All rights reserved.
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41.
  • Denk, Thomas, et al. (författare)
  • Early Miocene climate and biomes of Turkey: Evidence from leaf fossils, dispersed pollen, and petrified wood
  • 2019
  • Ingår i: Palaeogeography, Palaeoclimatology, Palaeoecology. - Amsterdam : Elsevier. - 0031-0182 .- 1872-616X. ; 530, s. 236-248
  • Tidskriftsartikel (refereegranskat)abstract
    • The early Miocene was a period of major palaeogeographic reorganization in the eastern Mediterranean region, during which time the Anatolian Plateau became subaerial and several intracontinental basins intermittently became connected to the Paratethys and Mediterranean seas. In this paper, we analyse early Miocene vegetation and climate using leaf records, palynological assemblages, and fossil wood at 36 localities from western and central Turkey, most of which have precise age control based on radiometric dating and mammal faunal ages. Using the leaf flora of Güvem (Beş Konak, Keseköy), Climate Leaf-Analysis Multivariate Program (CLAMP) analyses and Köppen signatures were employed to infer a palaeoclimate typical of modern laurel forest regions. Based on the palynological records, abundance of various pollen-taxa was used as a measure of openness of vegetation and regional presence of major tree taxa. Most pollen floras are dominated by tree pollen (ranging from 85 to 98%) and indicated widespread afforestation. In the pollen diagrams, shifts in dominance from swamp forest elements (Taxodioideae) to well-drained forests (Pinaceae) indicate changes in lake levels or phases of basin development. Such shifts may have been associated with the development of more xeric forest vegetation. Wood anatomical features such as false tree rings further may indicate seasonal climate. Pollen diagrams and macrofossils reflect zonal and azonal broadleaf and needleleaf forest and extrazonal open vegetation. The latter occurred in areas with shallow soils on volcanic rocks or limestone (e.g. cycads, Dracaena), or coastal areas (herb dominance). Taxonomic composition and biogeographic affinities suggest laurel forest as a major forest biome on well-drained soils and ecotones between laurel forest and broadleaf deciduous forest biomes. A comparison with younger floras shows that these are neither more diverse nor more warmth-loving despite an increase in global temperature (Mid-Miocene Climatic Optimum) suggesting bottlenecks during previous (Oligocene) cooler times for warmth-loving taxa.
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42.
  • Dong, Jiang, et al. (författare)
  • Millennial-scale interaction between the East Asian winter monsoon and El Niño-related tropical Pacific precipitation in the Holocene
  • 2021
  • Ingår i: Palaeogeography, Palaeoclimatology, Palaeoecology. - : Elsevier BV. - 0031-0182. ; 573
  • Tidskriftsartikel (refereegranskat)abstract
    • Both the East Asian winter monsoon (EAWM) and El Niño (EN) activities are vital climate modes that regulate the Pacific hydrologic cycle. However, the Holocene interactions among the EAWM, EN activities, and tropical Pacific precipitation remain unclear due to the lack of appropriate EAWM proxies. Here, we present high-resolution grain size records from the East China Sea shelf along with a transient climate model simulation to study the Holocene EAWM evolution and compare the findings with paleo-EN precipitation-related proxies records. The millennial-scale oscillations of grain size records, which are indicative of the intensity of the EAWM-driven coastal current, reveal an anti-phase coupling between the EAWM and EN-related tropical Pacific precipitation on a millennial timescale since 5.8 ka. These results, which are consistent with simulation results, indicate that the intensified EAWM could not only reduce equatorial western Pacific precipitation by reducing the sea surface temperature but also likely change boundary conditions in the tropical Pacific (i.e., the east-west Pacific temperature gradient and westerly anomaly) to favor the formation of subsequent intensive EN activities. The enhanced EN activities, inferred by the positive tropical eastern Pacific precipitation anomalies, could subsequently suppress the EAWM through anomalous low-level anticyclones and associated southerly anomalies, thereby generating intensified tropical western Pacific (mainly tropical monsoon areas) precipitation. Our study highlights these intrinsic interactions during the mid- to late Holocene and has useful implications for understanding this millennial-scale climate oscillation, which may represent periodic atmospheric exchange between high- and low-latitude climate systems by mediating the EAWM.
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43.
  • Dupret, Vincent, et al. (författare)
  • First Perigondwanan record of actinolepids (Vertebrata: Placodermi: Arthrodira) from the Lochkovian (Early Devonian) of Spain and its palaeobiogeographic significance
  • 2011
  • Ingår i: Palaeogeography, Palaeoclimatology, Palaeoecology. - : Elsevier BV. - 0031-0182 .- 1872-616X. ; 310:3-4, s. 273-282
  • Tidskriftsartikel (refereegranskat)abstract
    • Different palaeogeographic models have been proposed for the position of Laurussia ( including Baltica) and Gondwana-derived microcontinents ( including Ibero-Armorica) during Ordovician to Late Carboniferous times. Principal differences concern the presence and duration of a large ocean, the Rheic Ocean, acting as a faunal barrier between these areas. The timing of the collision of Laurussia with Gondwana and/or Gondwana-derived terranes continues to be debated. Here we present new faunal data revealing close biogeographical relations between Ibero-Armorica ("Perigondwanan" or Gondwanan derivate terranes) and Podolia (SE margin of Baltica, in Laurussia). The placoderm assemblage found in the mid-late Lochkovian (Lower Devonian) of Celtiberia (north-central Spain), consisting of the 'actinolepid' species Kujdanowiaspis podolica, Erikaspis zychi and the acanthothoracid Palaeacanthaspis aff. P. vasta, is similar, both in terms of taxonomy and stratigraphic record, to that encountered in the Lochkovian of Podolia (Ukraine; Laurussia) and until now considered as endemic to this region. Moreover, vertebrate faunal links between Podolia and Celtiberia are also extended to the chondrichthyan scale-based species Seretolepis elegans and Altholepis composita previously documented exclusively from Laurussian localities (Podolia and Mackenzie Mountains in Canada), which occur together with the placoderm remains described herein. These evidences support the hypothesis that intermittent shallow neritic migration paths between Podolia (as well as "Avalonia") and Iberia existed in the late Lochkovian, agreeing with a palaeogeographic reconstruction showing close proximity between peri-Gondwanan or Gondwana-derived terranes and Laurussia. It supports the palaeogeographic model of the non-oceanic Variscan Mobile Crustal Field and it corroborates the arguments against wide oceans, acting as biogeographical relevant barriers, between Baltica and Gondwana in early Devonian times. The distribution patterns of heavy-shelled ostracods, turbidicolous brachiopods, and Rhenish trilobites also support these conclusions.
  •  
44.
  • Ebbestad, Jan Ove R. (författare)
  • Gastropoda, Tergomya and Paragastropoda (Mollusca) from the Lower Ordovician Fezouata Formation, Morocco
  • 2016
  • Ingår i: Palaeogeography, Palaeoclimatology, Palaeoecology. - : Elsevier BV. - 0031-0182 .- 1872-616X. ; 460, s. 87-96
  • Tidskriftsartikel (refereegranskat)abstract
    • Gastropoda, Tergomya, and Paragastropoda (GTP) are a small but recognizable part of the collective Fezouata biota from the Lower Ordovician (Tremadocian-Floian) Fezouata Formation in Morocco. GTP range through the sequence but become more abundant and diverse in the stratigraphically higher and shallower marine parts of the succession. About 200 rock samples in existing collections have GTP but usually each slab contains several specimens so the number of individual is many times higher. A total of seven species are recognized of which four were known earlier. Gastropods are represented by the planispiral bellerophontoid Sinuites sp., recognized for the first time in the Tremadocian part of the succession, and the anisostrophic, nearly planispiral Lesueurilla prima (Barrande in Perner). Tergomyans are most abundant, dominated by the genus Carcassonnella with Carcassonnella courtessolei Horny and Peel, Carcassonnella vizcainoi Horny and Peel, and Carcassonnella sp. The latter encompass several specimens from different localities and stratigraphical levels, and may represent one of the named species or new varieties. Carcassonnella is for the first time recorded in the Tremadocian part of the succession. A second tergomyan is Thoralispira laevis (Thoral), while paragastropoda are represented byPelecyogyra fezouataensis Ebbestad and Lefebvre. In the peri-Gondwana area Carcassonnella, Thoralispira, and Lesueurilla are considered signature taxa, and the Fezouata GTP compare closely with those of Montagne Noire, France, both in composition and distribution. The Bohemian fauna is slightly younger (Floian-Darriwilian) with different species, except for Lesueurilla prima. The latter may have a wider distribution, being tentatively recognized in the Lower Ordovician of Argentina and Spain.
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45.
  • Egger, H, et al. (författare)
  • Early Eocene climatic, volcanic, and biotic events in the northwestern Tethyan Untersberg section, Austria
  • 2005
  • Ingår i: Palaeogeography, Palaeoclimatology, Palaeoecology. - : Elsevier BV. - 1872-616X .- 0031-0182. ; 217:3-4, s. 243-264
  • Tidskriftsartikel (refereegranskat)abstract
    • The 40 in thick Untersberg section (Salzburg, Austria) of the Northern Calcareous Alps comprises the Palaeocene-Eocene transition and spans the upper part of calcareous nannoplankton zone NP9 and the lower part of zone NP10 (subzone NP10a). These zones are equivalent to planktonic foraminifera zone P5 and the lower part of zone P6 (sub-zone P6a). The succession was deposited in a lower bathyal slope environment at a palaeodepth of about 2000 in. Within the dominantly marlstone succession, a 5.5-m-thick intercalation of red and green claystone and marly claystone represents the global negative carbon isotope excursion (CIE) which is used to recognize the Palaeocene-Eocene boundary. The CIE was associated with a shallowing of the calcite compensation depth by at least 1 km. Throughout the section, clay mineral assemblages are dominated by smectite, indicating a seasonal climate with alternating wet and dry conditions. A 49% increase in detrital quartz and feldspar within the CIE-interval suggests enhanced continental run-off This was probably the result of the establishment of a monsoonal setting, in which vegetation was sparse, while periodic high rainfall caused pronounced sediment transport. The increased terrestrially derived input is associated with abundant radiolarian casts indicating high primary productivity. This suggests that seasonal nutrient pulses resulting from intensified precipitation during the wet season have caused high surface-water fertility. The benthic foraminifera faunas of the samples rich in siliceous plankton are strongly dominated by Glomospira spp., Nuttalides truempyii, Abyssamina poagi, Anomalinoides praeacutus, Anomalinoides nobilis, and Oridorsalis spp. We assume that the Glomospira-Nuttalides fauna consists of opportunistic species which quickly react to seasonally varying amounts of food. The calcareous nannoplankton assemblage of the CIE-interval is characterized by the first occurrences of the genus Rhomboaster and of Discoaster araneus and Discoaster mahmoudii, whereas Scapholithus apertus become extinct at the Palaeocene-Eocene boundary. Within nannoplankton sub-zone NP10a, a series of primarily basaltic ashes give evidence for a major episode of explosive volcanism which can be correlated with the positive ash-series of the Fur-Formation in northern Denmark. The wide dispersal distance of the tephras implies Plinian-scale eruptions and multiple ejections of large volumes of pyroclastic material.
  •  
46.
  • Ekblom, Anneli, 1969-, et al. (författare)
  • Dung fungi as indicators of past herbivore abundance, Kruger and Limpopo National Park
  • 2010
  • Ingår i: Palaeogeography, Palaeoclimatology, Palaeoecology. - : Elsevier BV. - 0031-0182 .- 1872-616X. ; 296:1-2, s. 14-27
  • Tidskriftsartikel (refereegranskat)abstract
    • Effective wildlife management needs historical data on herbivore abundance and its interactions with vegetation, climate and disturbance over longer time periods than is available through observational and archive data. Spores specific to herbivore dung provide a potential source of information on past herbivore abundances. This paper sets out to evaluate the potential of fungal spores as environmental indicators and in particular the use of coprophilous fungi in understanding past herbivore densities and their impact on the savanna landscape of Kruger and Limpopo National Parks (South Africa and Mozambique). Spore assemblages from six sedimentary cores are analysed and compared with the pollen data. Spores of coprophilous fungi, Coniochaeta cf ligniaria, and Sordariaceae in particular provide a valuable source of information about past herbivore densities.  The spore assemblages of investigated localities show historical fluctuations in herbivore abundance. Peaks in wild/domestic herbivore densities can be seen, on a local scale from 800– 900 AD and another at 1400 AD, however, these cannot be linked with any significant changes in vegetation. The last 200-300 years have seen an increased abundance of herbivores in the Limpopo floodplain sites, particularly domestic cattle. There is no clear correspondence between changes in herbivore abundance and local vegetation in this period or the 20th century. However, domestic cattle, together with wild herbivores, probably contributed to creating a mosaic type of landscape with heterogeneous tree cover.
  •  
47.
  • Ekblom, Anneli, 1969-, et al. (författare)
  • Rainfall variability and vegetation dynamics of the lower Limpopo Valley, Southern Africa, 500 AD to present
  • 2012
  • Ingår i: Palaeogeography, Palaeoclimatology, Palaeoecology. - : Elsevier BV. - 0031-0182 .- 1872-616X. ; 363, s. 69-78
  • Tidskriftsartikel (refereegranskat)abstract
    • The long-term responses of vegetation to climate variability are of relevance for predicting present and future vegetation change, and have implications for the management of savanna and riparian ecosystems. This paper explores the links between regional rainfall, hydrology and vegetation dynamics in the savannas and riverine forests of the lower Limpopo Valley, southern Africa, from 800 AD to the present, reviewing palaeoecological data (fossil pollen, spores, diatoms and lithology) from several hydrological systems in Kruger National Park (KNP), South Africa and Limpopo National Park (PNL), Mozambique. The PNL-KNP records show that riverine arboreal taxa expanded during wetter periods, including 800-1400 AD and after 1800 AD. Between 1400 and 1800 AD, grasses, savanna taxa and generalist taxa were favored over riparian taxa, a change that is linked with the onset of dry spells in the region (corresponding to the so-called Little Ice Age). The most extreme drought events around 1700 AD resulted in a marked decline of riparian forest taxa near Lake Mapimbi, KNP. In contrast, many water-scarce sequences away from the riverine environment, such as Radio Pan, Mafayeni Pan, Malahlapanga Pan and Lake Makwadzi show stable grassland vegetation throughout the last 1200 years. The results demonstrate the resilience of the grassland-savanna ecosystems to projected climate change with warmer and overall drier climate. The riverine forests are predicted to be more vulnerable especially as more extreme weather events are projected.
  •  
48.
  • Elgh, Erik, et al. (författare)
  • Pterosaur track assemblages from the Upper Jurassic (lower Kimmeridgian) intertidal deposits of Poland : Linking ichnites to potential trackmakers
  • 2019
  • Ingår i: Palaeogeography, Palaeoclimatology, Palaeoecology. - : ELSEVIER. - 0031-0182 .- 1872-616X. ; 530, s. 32-48
  • Tidskriftsartikel (refereegranskat)abstract
    • Two distinct tetrapod track assemblages, dominated by pterosaur traces, are reported from Upper Jurassic (lower Kimmeridgian, Hypselocyclum Zone) tidal flat carbonate deposits exposed in Wierzbica Quarry, 20 km south of Radom, Poland. The pterosaur tracks, tentatively assigned to Pteraichnus isp. are well preserved as a positive hyporelief in intertidal facies. Some are preserved with anatomical details (e.g., skin, claw or digital pad impressions) and quality sufficient to make preliminary ichnotaxonomic assignment. Nearly all collected specimens are larger than most other pterosaurian ichnites of the Late Jurassic age, thus adding to the growing diversity of pterosaur traces known from this time period. Morphometrical and anatomical analyses show that ctenochasmatoids or possibly non-pterydactyloid monofenestratans or rhamphorhynchids were most likely the trackmakers. Anatomical comparisons give new insights into the morphology of the pes of pterydactyloids and the most closely related non-pterodactyloids which may be correlated with a niche expansion into marginal marine and lacustrine environments by Middle and Late Jurassic pterosaurs. The palaeoenvironmental interpretation as tidal flat is confirmed by presence of vertically accreted tidal bundles, each representing deposition in one tidal cycle. Most likely then, this was one of the environments frequented by these pterosaurs and other small tetrapods. The wider palaeoecological significance of the tracks is evaluated in the context of other similar reports from the Late Jurassic of Europe, Africa and North America.
  •  
49.
  • Emmanouilidis, Alexandros, et al. (författare)
  • Holocene paleoclimate variability in the eastern Mediterranean, inferred from the multi-proxy record of Lake Vouliagmeni, Greece
  • 2022
  • Ingår i: Palaeogeography, Palaeoclimatology, Palaeoecology. - : Elsevier. - 0031-0182 .- 1872-616X. ; 595
  • Tidskriftsartikel (refereegranskat)abstract
    • This study presents a Holocene multi-proxy record from Lake Vouliagmeni, eastern Gulf of Corinth, Greece. The lake is subjected to intense climatic and tectonic forces causing stratigraphic variations with laminated sediments frequently interrupted by homogenous sections and event deposits. Lamination couplets consist of aragonite layers alternating with detrital and organic residues formed during periods of seawater intrusion and stratification of the lake water. The discontinuous occurrence of laminated deposits excludes a varve based chronology from being established but highlights the susceptibility of the lake to record environmental and climatic changes. Our synthesis model for regional climatic reconstruction and local environmental changes derives from δ18O and δ13C data from laminated and homogenous sediments studied separately and depending on the dominant carbonate mineral. This is further strengthened by high-resolution geochemical proxies, diatom and sedimentological data. Regional climatic signals from key sites and possible links to the Lake Vouliagmeni record are explored in response to atmospheric circulation patterns. Phases of overall humid conditions are recorded by increased inflow of siliciclastic material to the lake and negative δ18Obulk values. In contrast, periods of marine intrusion and enhanced evaporation are recorded by aragonite precipitation, positive δ18OAr values and laminations. The laminations formed in the lake seem to occur during periods of sea water intrusion into the lake, which led to pycnocline stabilization and stratified lake waters.
  •  
50.
  • Eriksson, Mats, et al. (författare)
  • Biotic dynamics and carbonate microfacies of the conspicuous Darriwilian (Middle Ordovician) 'Taljsten' interval, south-central Sweden
  • 2012
  • Ingår i: Palaeogeography, Palaeoclimatology, Palaeoecology. - : Elsevier BV. - 1872-616X .- 0031-0182. ; 367, s. 89-103
  • Tidskriftsartikel (refereegranskat)abstract
    • Enclosed in the Darriwilian (Middle Ordovician) part of the reddish 'orthoceratite limestone' of Baltoscandia is a conspicuous c. 1.5 m thick unit colloquially known as the 'Taljsten' interval. It has a wide geographical distribution in the Baltoscandian paleocontinent but is particularly well exposed in south-central Sweden. The unit is characterized by its deviant gray color and beds with a mass occurrence of cystoid echinoderms. Moreover, the recent discovery of an anomalous abundance of extraterrestrial chromite grains and micrometeorites in the 'Taljsten' and immediately adjacent strata bear witness of a time of deposition correlating to an increased influx of extraterrestrial matter to Earth. In this study we analyze the faunal dynamics, based primarily on microfossils and carbonate microfacies, across this intriguing interval. Generally known as a macrolithologically monotonous succession, the 'Taljsten' proved more heterogeneous than previously believed in terms of fossil content and preservation, as well as mineral content and composition. The general texture is wackestone/packstone, but local heterogeneities are frequent. A microfaunal reorganization occurred with a transition from a trilobite- and brachiopod-dominated community to one dominated by echinoderms, which is mirrored also macroscopically by the cystoids. The latter pelmatozoans seem to have flourished and might even have aided in the formation of the numerous hardgrounds. The increase in echinoderms is linked to a Volkhovian increase in echinoderms in eastern Baltica. In the immediate post-'Taljsten' strata there is no distinct change back to the pre-'Taljsten' biota. Conodont and ostracod faunal diversity data reveal peak values in the 'Taljsten' compared to the enclosing strata, suggesting that the paleoenvironment was more suitable for higher diversity faunas of these metazoan groups. All data collectively support a regression in the beginning of the 'Taljsten', likely followed by transgression in its upper part. (C) 2012 Elsevier B.V. All rights reserved.
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