| 1. |
- Akikuni, Kenichi, et al.
(author)
-
Stratigraphy of Triassic-Jurassic boundary sequences from the Kawhia coast and Awakino gorge, Murihiku Terrane, New Zealand
- 2010
-
In: Stratigraphy. - 1547-139X. ; 7:1, s. 7-24
-
Journal article (peer-reviewed)abstract
- We have examined the stable carbon isotope stratigraphy, bio- and litho-stratigraphy of the Upper Triassic (Otapirian) - Lower Jurassic (Aratauran) boundary strata from the Awakino gorge and Kawhia coast sections, Murihiku Terrane, North Island, New Zealand. Successive occurrences of species of the bivalve genus Otapiria, O. dissimilis, O. marshalli and O. aff. marshalli, and also of age diagnostic ammonites indicate that the Hettangian strata in both sections are very thin compared with the Rhaetian sequences. Lamination structures are well developed at the Tr-Jr (Rhaetian-Hettangian) boundary transition interval. The delta C-13 values of organic matter from siltstone and carbonate nodules in the sedimentary rocks range from -28.5 to -25.5 parts per thousand and there is no correlation between delta C-13(org) and C/N ratios. The excursion patterns of delta C-13(org) from both sections are similar, showing a negative spike at the uppermost Rhaetian and a positive spike immediately below the Tr-Jr boundary. A long-lived positive shift is also recognized in the Awakino gorge section, which coincides in pattern with those reported in Tr-Jr boundary successions from the Queen Charlotte Islands, British Columbia, Canada. These results suggest that although magnitude and absolute values are slightly different, the integrated pattern of stable carbon isotope signatures over the Tr-Jr boundary could be a valuable tool for correlation, at least between sedimentary rocks from similar depositional settings in the Panthalassa.
|
|
| 2. |
|
|
| 3. |
- Bercovici, Antoine, et al.
(author)
-
Palynostratigraphy of John's Nose, a new Cretaceous-Paleogene boundary section in southwestern North Dakota, USA
- 2012
-
In: Palynology. - : Informa UK Limited. - 1558-9188 .- 0191-6122. ; 36, s. 36-47
-
Journal article (peer-reviewed)abstract
- This study documents the terrestrial palynological record at the John's Nose section, a new Cretaceous-Paleogene (K-Pg) boundary site in North Dakota, USA. In addition to Mud Buttes and Pyramid Butte, John's Nose represents the third K-Pg section in southwestern North Dakota that preserves direct evidence of the Chicxulub asteroid impact, allowing for direct comparison over the timing and trends of the palynological record in respect to this event. The palynological analysis of John's Nose section reveals the presence of 68 pollen and spore taxa. Immediately above the boundary clay, a high abundance of fern spores of the genera Cyathidites and Laevigatosporites is recorded (with 59% of the assemblage being represented by Cyathidites). This very distinctive K-Pg 'fern spike' event is correlated with the devastation of land plants immediately following the asteroid impact and matches the composition generally reported from other sites in southwestern North Dakota. Palynostratigraphy demonstrates that the placement of the K-Pg boundary based upon the identification of the Last Appearance Datum (LAD) of typical Maastrichtian taxa (K-taxa) may be misleading. The presence of occasional K-taxa up to a few meters above the boundary clay at John's Nose represents an important difference when compared to previous reports. In light of this observation, LADs should be used cautiously as the primary criteria to identify the boundary; some K-taxa may have a short-term presence in the earliest Paleogene, or be reworked. In the John's Nose section, major changes and extinction in the palynological record occur at the geochemical K-Pg boundary, indicating that a catastrophic turnover took place over a short time.
|
|
| 4. |
- Bercovici, Antoine, et al.
(author)
-
Palynostratigraphy of the cretaceous-paleogene mass-extinction interval of the Northern Hemisphere
- 2012
-
In: Dìcéngxué zázhì. - 0253-4959. ; 36:2, s. 165-178
-
Journal article (peer-reviewed)abstract
- For a long time debate has taken place regarding the trends and extinction rates associated with the Cretaceous- Paleogene (K-Pg) mass extinction event on land. While mainly focussed on vertebrates and more especially non-avian dinosaurs, the dynamics of the plant cover remains nonetheless a major component for the understanding the biological response across the K-Pg interval and associated ecosystem destabilization. In this paper, we present a review of the late Cretaceous to Paleogene pollen and spore stratigraphy within the Northern Hemisphere Aquilapollenites paleophytogeographic province. In the United States of America, Late Cretaceous assemblages are marked by the appearance of a series of key-taxa, the Santonian-Campanian transition is characterized by the appearance of Aquilapollenites and associated triprojectate genera, while the base of the Maastrichtian is marked by the appearance of the oculate genus Wodehouseia as well as Kurtzipites sp. The K-Pg extinction event remains easily identifiable in the palynological record with the disappearance of a series of angiospermous taxa part of the Wodehouseia spinata Assemblage Zone, which are characterized by relatively large size and complex wall structure. The recovery palynoflora in the Paleocene is represented by assemblages dominated by porate grains, with key-species from the Momipites and Caryapollenites genera. As current data covers mostly the North American terrestrial record, more research efforts are needed within Chinese,European and Southern Hemisphere localities to provide for a better understanding of the global response of the terrestrialbiosphere to the K-Pg impact event.
|
|
| 5. |
- Bercovici, Antoine, et al.
(author)
-
Terrestrial paleoenvironment characterization across the Permian-Triassic boundary in South China
- 2015
-
In: Journal of Asian Earth Sciences. - : Elsevier BV. - 1367-9120 .- 1878-5786. ; 98, s. 225-246
-
Journal article (peer-reviewed)abstract
- Well-preserved marine fossils in carbonate rocks permit detailed studies of the end-Permian extinction event in the marine realm. However, the rarity of fossils in terrestrial depositional environments makes it more challenging to attain a satisfactory degree of resolution to describe the biotic turnover on land. Here we present new sedimentological, paleontological and geochemical (X-ray fluorescence) analysis from the study of four terrestrial sections (Chahe, Zhejue, Mide and Jiucaichong) in Western Guizhou and Eastern Yunnan (Yangtze Platform, South China) to evaluate paleoenvironmental changes through the Permian-Triassic transition. Our results show major differences in the depositional environments between the Permian Xuanwei and the Triassic Kayitou formations with a change from fluvial-lacustrine to coastal marine settings. This change is associated with a drastic modification of the preservation mode of the fossil plants, from large compressions to small comminuted debris. Plant fossils spanning the Permian-Triassic boundary show the existence of two distinct assemblages: In the Xuanwei Formation, a Late Permian (Changhsingian) assemblage with characteristic Cathaysian wetland plants (mainly Gigantopteris dictyophylloides, Gigantonoclea guizhouensis, G. nicotianaefolia, G. plumosa, G. hallei, Lobatannularia heinanensis, L. cathaysiana, L. multifolia, Annularia pingloensis, A. shirakii, Paracalamites stenocostatus, Cordaites sp.) is identified. In the lowermost Kayitou Formation, an Early Triassic (Induan) Annalepis-Peltaspermum assemblage is shown, associated with very rare, relictual gigantopterids. Palynological samples are poor, and low yield samples show assemblages almost exclusively represented by spores. A similar to 1 m thick zone enriched in putative fungal spores was identified near the top of the Xuanwei Formation, including diverse multicellular forms, such as Reduviasporonites sp. This interval likely corresponds to the PTB "fungal spike" conventionally associated with land denudation and ecosystem collapse. While the floral turnover is evident, further studies based on plant diversity would be required in order to assess contribution linked to the end-Permian mass extinction versus local paleoenvironmental changes associated with the transition between the Xuanwei and Kayitou formations. (C) 2014 Elsevier Ltd. All rights reserved.
|
|
| 6. |
- Bergström, J., et al.
(author)
-
In memoriam: Leif Carserud
- 2008
-
In: Geologiskt Forum. - 1104-4721. ; 57, s. 56-56
-
Journal article (pop. science, debate, etc.)
|
|
| 7. |
- BERMÚDEZ,, Hermann Darío, et al.
(author)
-
The Cretaceous/Paleogene boundary deposits on Gorgonilla Island
- 2018
-
In: The Geology of Colombia: Volume 3 Paleogene – Neogene. - Bogota : Servicio Geológico Colombiano. ; , s. 1-34
-
Book chapter (peer-reviewed)abstract
- A ~20 mm thick spherule bed representing Chicxulub impact ejecta deposits and marking the Cretaceous/Paleogene (K/Pg) boundary was recently discovered on Gorgonilla Island (Gorgona National Natural Park, Pacific of Colombia). This discovery represents the first confirmed record of the K/Pg event in Colombia, South America and the eastern Pacific Ocean. The deposit consists of extraordinarily well–preserved glass spherules (microtektites and microkrystites) reaching 1.1 mm in diameter. Importantly, the Gorgonilla spherule bed is unique relative to other K/Pg boundary sites in that up to 90% of the spherules are intact and not devitrified, and the bed is virtually devoid of lithic fragments and microfossils. The spherules were deposited in a deep marine environment, possibly below the calcite compensation depth. The preservation, normal size–gradation, presence of fine textures within the spherules, and absence of bioturbation or traction transport indicate that the Gorgonilla spherules settled within a water column with minimal disturbance. Thus, the spherule bed may represent one of the first parautochthonous primary deposits of the Chicxulub impact known to date. 40Ar/39Ar dating and micropaleontological analysis reveal that the Gorgonilla spherule bed resulted from the Chicxulub impact. Intense soft–sediment deformation and bed disruption in Maastrichtian sediments of the Gorgonilla Island K/Pg section provide evidence for seismic activity triggered by the Chicxulub bolide impact, 66 million years ago. It is also notable that the basal deposits of the Danian in the Colombian locality present the first evidence of a recovery vegetation, characterized by ferns from a tropical habitat, shortly following the end–Cretaceous event.
|
|
| 8. |
- Bermúdez, Hermann, et al.
(author)
-
The Cretaceous/Paleogene Boundary Deposits on Gorgonilla Island
- 2019. - 1
-
In: <em>The Geology of Colombia, Volume 3 Paleogene – Neogene </em><em></em>. - Bogota : Servicio Geológico Colombiano. ; , s. 1-19
-
Book chapter (peer-reviewed)abstract
- A ca. 20 mm thick spherule bed representing Chicxulub impact ejecta deposits and marking the Cretaceous/Paleogene (K/Pg) boundary was recently discovered on Gorgonilla Island (Gorgona National Natural Park, Pacific of Colombia). This discovery represents the first confirmed record of the K/Pg event in Colombia, South America and the eastern Pacific Ocean. The deposit consists of extraordinarily well–preserved glass spherules (microtektites and microkrystites) reaching 1.1 mm in diameter. Importantly, the Gorgonilla spherule bed is unique relative to other K/Pg boundary sites in that up to 90% of the spherules are intact and not devitrified, and the bed is virtually devoid of lithic fragments and microfossils. The spherules were deposited in a deep marine environment, possibly below the calcite compensation depth. The preservation, normal size–gradation, presence of fine textures within the spherules, and absence of bioturbation or traction transport indicate that the Gorgonilla spherules settled within a water column with minimal disturbance. The spherule bed may represent one of the first parautochthonous primary deposits of the Chicxulub impact known to date. 40Ar/39Ar dating and micropaleontological analysis reveal that the Gorgonilla spherule bed resulted from the Chicxulub impact. Intense soft–sediment deformation and bed disruption in Maastrichtian sediments of the Gorgonilla Island K/Pg section provide evidence for seismic activity triggered by the Chicxulub bolide impact, 66 million years ago. It is also notable that the basal deposits of the Danian in the Colombian locality present the first evidence of a recovery vegetation, characterized by ferns from a tropical habitat, shortly following the end–Cretaceous event.
|
|
| 9. |
- Bomfleur, Benjamin, et al.
(author)
-
Fossilized nuclei and chromosomes reveal 180 millionyears of genomic stasis in Royal Ferns
- 2014
-
In: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 343, s. 1376-1377
-
Journal article (peer-reviewed)abstract
- Rapidly permineralized fossils can provide exceptional insights into the evolution of life over geological time. Here, we present an exquisitely preserved, calcified stem of a royal fern (Osmundaceae) from Early Jurassic lahar deposits of Sweden in which authigenic mineral precipitation from hydrothermal brines occurred so rapidly that it preserved cytoplasm, cytosol granules, nuclei, and even chromosomes in various stages of cell division. Morphometric parameters of interphase nuclei match those of extant Osmundaceae, indicating that the genome size of these reputed “living fossils” has remained unchanged over at least 180 million years—a paramount example of evolutionary stasis.
|
|
| 10. |
- Bralower, Timothy, et al.
(author)
-
Origin of a global carbonate layer deposited in the aftermath of the Cretaceous-Paleogene boundary impact
- 2020
-
In: Earth and Planetary Science Letters. - Amsterdam : Elsevier. - 0012-821X .- 1385-013X. ; 548
-
Journal article (peer-reviewed)abstract
- Microcrystalline calcite (micrite) dominates the sedimentary record of the aftermath of the Cretaceous–Paleogene (K–Pg) impact at 31 sites globally, with records ranging from the deep ocean to the Chicxulub impact crater, over intervals ranging from a few centimeters to more than seventeen meters. This micrite-rich layer provides important information about the chemistry and biology of the oceans after the impact. Detailed high-resolution scanning electron microscopy demonstrates that the layer contains abundant calcite crystals in the micron size range with a variety of forms. Crystals are often constructed of delicate, oriented agglomerates of sub-micrometer mesocrystals indicative of rapid precipitation. We compare the form of crystals with natural and experimental calcite to shed light on their origin. Close to the crater, a significant part of the micrite may derive from the initial backreaction of CaO vaporized during impact. In more distal sites, simple interlocking rhombohedral crystals resemble calcite precipitated from solution. Globally, we found unique calcite crystals associated with fossilized extracellular materials that strikingly resemble calcite precipitated by various types of bacteria in natural and laboratory settings. The micrite-rich layer contains abundant bacterial and eukaryotic algal biomarkers and most likely represents global microbial blooms initiated within millennia of the K–Pg mass extinction. Cyanobacteria and non-haptophyte microalgae likely proliferated as dominant primary producers in cold immediate post-impact environments. As surface-water saturation state rose over the following millennia due to the loss of eukaryotic carbonate producers and continuing river input of alkalinity, “whitings” induced by cyanobacteria replaced calcareous nannoplankton as major carbonate producers. We postulate that the blooms grew in supersaturated surface waters as evidenced by crystals that resemble calcite precipitates from solution. The microbial biomass may have served as a food source enabling survival of a portion of the marine biota, ultimately including life on the deep seafloor. Although the dominance of cyanobacterial and algal photosynthesis would have weakened the biological pump, it still would have removed sufficient nutrients from surface waters thus conditioning the ocean for the recovery of biota at highertrophic levels.
|
|
| 11. |
- Bralower, T, et al.
(author)
-
The Habitat of the Nascent Chicxulub Crater
- 2020
-
In: AGU Advances. - : American Geophysical Union (AGU). ; 1
-
Journal article (peer-reviewed)abstract
- An expanded sedimentary section provides an opportunity to elucidate conditions in the nascent Chicxulub crater during the hours to millennia after the Cretaceous‐Paleogene (K‐Pg) boundary impact. The sediments were deposited by tsunami followed by seiche waves as energy in the crater declined, culminating in a thin hemipelagic marlstone unit that contains atmospheric fallout. Seiche deposits are predominantly composed of calcite formed by decarbonation of the target limestone during impact followed by carbonation in the water column. Temperatures recorded by clumped isotopes of these carbonates are in excess of 70°C, with heat likely derived from the central impact melt pool. Yet, despite the turbidity and heat, waters within the nascent crater basin soon became a viable habitat for a remarkably diverse cross section of the food chain. The earliest seiche layers deposited with days or weeks of the impact contain earliest Danian nannoplankton and dinocyst survivors. The hemipelagic marlstone representing the subsequent years to a few millennia contains a nearly monogeneric calcareous dinoflagellate resting cyst assemblage suggesting deteriorating environmental conditions, with one interpretation involving low light levels in the impact aftermath. At the same horizon, microbial fossils indicate a thriving bacterial community and unique phosphatic fossils including appendages of pelagic crustaceans, coprolites andbacteria‐tunneled fish bone, suggesting that this rapid recovery of the base of the food chain may have supported the survival of larger, higher trophic‐level organisms. The extraordinarily diverse fossil assemblage indicates that the crater was a unique habitat in the immediate impact aftermath, possibly as aresult of heat and nutrients supplied by hydrothermal activity.
|
|
| 12. |
|
|
| 13. |
- Cavalcante, Larissa Lopes, et al.
(author)
-
Analysis of fossil plant cuticles using vibrational spectroscopy: A new preparation protocol
- 2023
-
In: Review of Palaeobotany and Palynology. - : Elsevier. - 0034-6667 .- 1879-0615. ; 316
-
Journal article (peer-reviewed)abstract
- Analyses for organic “fingerprints” on fossilized plant cuticles and pollen hold valuable chemotaxonomic and palaeoclimatic information, and are thus becoming more utilized by palaeobotanists. Plant cuticle and pollen composition are generally analyzed after standard treatments with several chemical reagents for mineral and mesophyll removal. However, the potential alterations on the fossil composition caused by the different cleaning reagents used are still poorly understood. We tested the effects of commonly used palaeobotanical processing methods on the spectra of fossilized cuticles from successions of Late Triassic to Early Jurassic age, including the gymnosperms Lepidopteris, Ginkgoites, Podozamites, Ptilozamites and Pterophyllum astartense. Our study shows that standard chemical processing caused chemical alterations that might lead to erroneous interpretation of the infrared (IR) spectra. The difference in pH caused by HCl induces changes in the proportion between the two bands at ~1720 and 1600 cm 1 (carboxylate and C-C stretch of aromatic compounds) indicating that the band at ~1610 cm 1 at least partially corresponds to carboxylate instead of C-C stretch of aromatic compounds. Interestingly, despite being used in high concentration, HF did not cause changes in the chemical composition of the cuticles. The most alarming changes were caused by the use of Schulze ’s solution, which resulted in the addition of both NO2 and (O)NO2 compounds in the cuticle. Consequently, a new protocol using H2CO3, HF, and H2O2 for preparing fossil plant cuticles aimed for chemical analyses is proposed, which provides an effective substitute to the conventional methods. In particular, a less aggressive and more sustainable alternative to Schulze’s solution is shown to be hydrogen peroxide, which causes only minor alteration of the fossil cuticle ’s chemical composition. Future work should carefully follow protocols, having in mind the impacts of different solutions used to treat leaves and other palaeobotanical material such as palynomorphs with aims to enable the direct comparison of spectra obtained in different studies.
|
|
| 14. |
- Coiro, Mario, et al.
(author)
-
Parallel evolution of angiosperm-like venation in Peltaspermales : a reinvestigation of Furcula
- 2024
-
In: New Phytologist. - 0028-646X .- 1469-8137.
-
Journal article (peer-reviewed)abstract
- Leaf venation is a pivotal trait in the success of vascular plants. Whereas gymnosperms have single or sparsely branched parallel veins, angiosperms developed a hierarchical structure of veins that form a complex reticulum. Its physiological consequences are considered to have enabled angiosperms to dominate terrestrial ecosystems in the Late Cretaceous and Cenozoic.Although a hierarchical-reticulate venation also occurs in some groups of extinct seed plants, it is unclear whether these are stem relatives of angiosperms or have evolved these traits in parallel. Here, we re-examine the morphology of the enigmatic foliage taxon Furcula, a potential early Mesozoic angiosperm relative, and argue that its hierarchical vein network represents convergent evolution (in the Late Triassic) with flowering plants (which developed in the Early Cretaceous) based on details of vein architecture and the absence of angiosperm-like stomata and guard cells.We suggest that its nearest relatives are Peltaspermales similar to Scytophyllum and Vittaephyllum, the latter being a genus that originated during the Late Triassic (Carnian) and shares a hierarchical vein system with Furcula.We further suggest that the evolution of hierarchical venation systems in the early Permian, the Late Triassic, and the Early Cretaceous represent ‘natural experiments’ that might help resolve the selective pressures enabling this trait to evolve.
|
|
| 15. |
- Coney, Louise, et al.
(author)
-
Geochemical and mineralogical investigation of the Permian-Triassic boundary in the Continental Realm of the Southern Karoo Basin, South Africa
- 2007
-
In: Palaeoworld. - : Elsevier BV. - 1875-5887 .- 1871-174X. ; 16, s. 67-104
-
Journal article (peer-reviewed)abstract
- Mineralogical and geochemical studies of the non-marine Permian–Triassic (P–Tr) boundary across two stratigraphically wellconstrained sections (Commando Drift Dam and Wapadsberg, Eastern Cape Province) in the southern Karoo Basin, South Africa, have been undertaken to provide further input on the cause of this mass extinction event, and so has a sedimentological and geochemical evaluation of a third P–Tr boundary section at Injusiti (Kwazulu-Natal) in the eastern Karoo Basin, South Africa. The Commando Drift Dam section has been constrained by previous palaeontological and palaeomagnetic work, with a palaeomagnetic reversal positioned 5.3m above the palaeontological P–Tr boundary. The Wapadsberg section has been constrained palaeontologically. All these P–Tr sections studied here mostly comprise mudstones, together with siltstones, sandstones, and in the southern Karoo Basin, carbonate nodular horizons. A change in colour of the mudstones from green-grey to red-brown takes place at the palaeontologically defined boundary. Variations in the major and trace element abundance profiles are usually limited to the carbonate nodular horizons, besides the overall effects of weathering. Bulk carbon isotopic studies of the Commando Drift Dam section revealed a negative δ13Cbulk excursion (background values of −15 to −20‰, with total extent of excursion to −24.9‰) 2 cm below the palaeontological boundary, followed by a gradual recovery and then another decrease in values leading towards the palaeomagnetic boundary. Above this boundary recovery to less negative δ13Cbulk values (ca. −18‰) occurs. The organic carbon record from the Commando Drift Dam (southern Karoo Basin) and Injusiti (eastern Karoo Basin) oscillates between −26.1 and −28.9‰, which is comparable to previous studies of different sections in the southern Karoo Basin. The magnitude of both the bulk and organic carbon isotopic variation can be interpreted to indicate a number of inputs (due to the fluctuating values) of organic carbon. The carbon isotope data for carbonates in the Injusiti section are different from the results on carbonates from other studies, but more work to expand this dataset is necessary. The palynological studies on the Commando Drift Dam section reveal the presence of a low diversity flora composed principally of bryophytes, lycophytes, and gymnosperms. These forms, including several Late Permian key-species, are traces of the surviving plants enduring after the major extinction-pulse. The presence of fungal palynomorphs and dearth of pollen/spores related to photosynthetic plants some metres above the palaeontological P–Tr boundary demonstrate similarities to the pattern of floral extinction at the Cretaceous–Palaeogene (K–Pg) boundary. The timing of vertebrate extinctions in the Karoo Basin has so far not been determined, but the 252.5 Ma age for a single zircon crystal from Commando Drift Dam dated here gives a maximum constraint on the age of the event bed, which is in agreement with the accepted age of the boundary. No evidence for impact-produced microdeformation features were found in quartz grains from either the Wapadsberg or Commando Drift Dam sections. Also, siderophile element data (including platinum group element (PGE)concentrations) do not support the possible presence of a meteoritic component at the boundary. Thus, a link between impact and P–Tr extinction is not indicated by the results of this study.
|
|
| 16. |
- Cui, Ying, et al.
(author)
-
Carbon cycle perturbation expressed in terrestrial Permian–Triassic boundary sections in South China
- 2015
-
In: Global and Planetary Change. - : Elsevier. - 0921-8181 .- 1872-6364.
-
Journal article (peer-reviewed)abstract
- Stable isotopes of inorganic and organic carbon are commonly used in chemostratigraphy to correlate marine and terrestrial sedimentary sequences based on the assumption that the carbon isotopic signature of the exogenic carbon pool dominates other sources of variability. Here, sediment samples from four Permian–Triassic boundary (PTB) sections of western Guizhou and eastern Yunnan provinces in South China, representing a terrestrial to marine transitional setting, were analyzed for δ13C of organic matter (δ13Corg). These values were subsequently compared to published δ13C values of carbonates (δ13Ccarb) from the Global Stratotype Section and Point at Meishan and many other marine and terrestrial sections. A similar isotopic trend evident through all four sections is characterized by a negative shift of 2–3‰ at the top of the Xuanwei Formation, where we tentatively place the PTB. This negative shift also corresponds to a turnover in the vegetation and the occurrence of fungal spores, which is generally interpreted as a proliferation of decomposers and collapse of complex ecosystems during the end-Permian mass extinction event. Moreover, the absolute values of δ13Corg are more extreme in the more distal (marine) deposits. The δ13Corg values for the studied sediments are more variable compared to coeval δ13Ccarb records from marine records especially in the interval below the extinction horizon. We contend that the depositional environment influenced the δ13Corg values, but that the persisting geographic δ13Corg pattern through the extinction event across the four independent sections is an indication that the atmospheric δ13C signal left an indelible imprint on the geologic record related to the profound ecosystem change during the end-Permian extinction event.
|
|
| 17. |
- Cui, Ying, et al.
(author)
-
Carbon cycle perturbation expressed in terrestrial Permian–Triassic boundary sections in South China
- 2017
-
In: Global and Planetary Change. - Amsterdam : Elsevier. - 0921-8181 .- 1872-6364. ; 148, s. 272-285
-
Journal article (peer-reviewed)abstract
- Stable isotopes of inorganic and organic carbon are commonly used in chemostratigraphy to correlatemarine andterrestrial sedimentary sequences based on the assumption that the carbon isotopic signature of the exogenic carbon pool dominates other sources of variability. Here, sediment samples fromfour Permian–Triassic boundary (PTB) sections ofwesternGuizhou and eastern Yunnan provinces in South China, representing a terrestrial tomarine transitional setting,were analyzed for δ13C of organic matter (δ13Corg). These valueswere subsequently compared to published δ13C values of carbonates (δ13Ccarb) from the Global Stratotype Section and Point at Meishan and many other marine and terrestrial sections. A similar isotopic trend evident through all four sections is characterized by a negative shift of 2–3‰ at the top of the Xuanwei Formation, where we tentatively place the PTB. This negative shift also corresponds to a turnover in the vegetation and the occurrence of fungal spores, which is generally interpreted as a proliferation of decomposers and collapse of complex ecosystems during the end-Permian mass extinction event. Moreover, the absolute values of δ13Corg are more extreme in the more distal (marine) deposits. The δ13Corg values for the studied sediments aremore variable compared to coeval δ13Ccarb records from marine records especially in the interval below the extinction horizon. We contend that the depositional environment influenced the δ13Corg values, but that the persisting geographic δ13Corg pattern through the extinction event across the four independent sections is an indication that the atmospheric δ13C signal left an indelible imprint on the geologic record related to the profound ecosystem change during the end-Permian extinction event.
|
|
| 18. |
- Danise, Silvia, et al.
(author)
-
Land-sea ecological connectivity during a Jurassic warming event
- 2022
-
In: Earth and Planetary Science Letters. - Amsterdam : Elsevier. - 0012-821X .- 1385-013X. ; 578, s. 117290-117290
-
Journal article (peer-reviewed)abstract
- Knowledge on how climate change affects land-sea ecological connectivity in deep time is scarce. To fill this knowledge gap we have assembled a unique dataset through a Jurassic (early Toarcian) warming event that includes quantitative abundance data from pollen and spores, organic-walled marine plankton and benthic macro-invertebrates, in association with geochemical data derived from the same sampled horizons, from the Cleveland Basin, UK. Using this dataset we: (i) reconstruct the timing of degradation and recovery of land-plants, marine primary producers and benthic fauna in response to this event, and (ii) test for connectivity between changes in land and marine ecosystems. We find a discrepancy between the timing of the response of land-plant and marine ecosystems to the event. Land-plants were the first to be affected by initial warming, but also recovered relatively quickly after the peak of warmth to return to pre-event levels of richness and diversity. Plankton and benthic fauna instead experienced a delayed response to initial warming, but as warming peaked, they suffered a rapid and extreme turnover. Recovery in the shelf sea was also delayed (particularly for the benthos) compared to the vegetation. Ecological connectivity analyses show a strong link between changes in terrestrial and marine ecosystems. The loss of large trees on land contributed to changes in marine plankton, from dinoflagellate-to prasinophyte algal-dominated communities, by enhancing erosion, runoff and nutrient-supply into shallow seas. Eutrophication and changes in primary productivity contributed to the decrease of dissolved oxygen in the water column and in bottom waters, which in turn affected benthic communities. Such cause-effect mechanisms observed in the Cleveland Basin are likely to have occurred in other basins of the Boreal Realm, and in part also in basins of the Sub-Boreal and Tethyan realms. Although palaeolatitudinal and palaeoceanographic gradients may have controlled local and regional changes in land-plants and marine ecosystems during the Early Jurassic, the main climatic and environmental changes linked to rapid global warming, enhanced weathering and high primary productivity, are shared among all the examined realms.
|
|
| 19. |
- Einarsson, Elisabeth
(author)
-
First evidence of the Cretaceous decapod crustacean Protocallianassa from Sweden
- 2016
-
In: Geological Society, London, Special Publications. - London : Geological Society of London. - 0305-8719. ; 434, s. 241-250
-
Journal article (peer-reviewed)abstract
- An assemblage of the burrowing ghost shrimp, Protocallianassa faujasi, is described, providing the first evidence of this decapod species from Sweden. The fossils occur in successions of the informal earliest late Campanian Belemnellocamax balsvikensis Zone at Åsen and the latest early Campanian B. mammillatus zone at Ivö Klack, both in the Kristianstad Basin of NE Skåne. Numerous, heavily calcified chelipeds were found within a restricted bed at Åsen that was rich in carbonate-cemented nodules. Based on the burrowing lifestyle of modern mud shrimps, we interpret these nodules as infilled burrow chambers. The low abundance of molluscs within the Protocallianassa beds is also consistent with analogous extant communities, indicating that a similar ecologically exclusive relationship ruled within the Late Cretaceous shallow marine ecosystems.
|
|
| 20. |
|
|
| 21. |
|
|
| 22. |
- Einarsson, Elisabeth
(author)
-
Paleoenvironments, palaeoecology and palaeobiogeography of late cretaceous (campanian) faunas from the Kristianstad basin, southern Sweden, with applications for science education
- 2018
-
Doctoral thesis (other academic/artistic)abstract
- This thesis is thematically divided into two sections: Part1 presents studies related to the palaeoenvironments,palaeoecology and palaeobiogeography of the LateCretaceous (Campanian) faunas from the KristianstadBasin of southern Sweden; Part 2 reports on applicationsof palaeontological research for science education inschools.Part 1 was based on personally conducted fieldworkand biostratigraphical analysis at various Santonian-Campanian localities throughout Skåne. However, themost complete section at Åsen provided the primary datasource and was systematically excavated with a team ofvolunteers, who employed wet-sieving methods to extractbulk fossil material from each bed within the sequence. Aseries of globally correlated temperature-induced changeswas detected in the stepwise declining abundanceand disappearance of rudists, sclerorhynchids and therajiforms Rhinobatos and Squatirhina, as well as marinecrocodilians, various mosasaurid lizard taxa. A rangeof local palaeoenvironments were also reconstructed,including estuaries, rocky coastlines, sandy beaches,drowned river valleys, shallow neritic settings, anddeeper offshore conditions. An archipelago bordering theFennoscandian landmasses also supported continentalecosystems comprising ferns, conifers and early floweringplants, with dinosaurs, pterosaurs and non-marine turtles.Trophic levels within the marine system incorporatedred algae and dinoflagellates as primary producers, withcorals, brachiopods, bivalves, echinoids, barnacles anddecapod crustaceans as benthos, and belemnites withinthe water column. Actinopterygian fish, sharks, rays andchimaeroids, chelonioid sea turtles, marine crocodilians,polycotylid and elasmosaurid plesiosaurians, variousmosasaurids and aquatic hesperornithiform birdscollectively represented middle level and apex predators.Herbivorous and carnivorous dinosaurs, lizards and softshelledtryonichid turtles evidence elements of terrestrialisland communities. The palaeobiogeographicalrelationships and dispersal of these local assemblageswas probably influenced by marine transgressions andregressions. These would have affected habitat availabilityand connectivity via changing water depths.Part 2 presents three school education projects aimed atincreasing awareness of geoscience and natural history inschools. The better integration of geological time conceptsand geosciences into the Swedish school curriculum isalso discussed. The first study described a project wherebyfossils were found in the sandboxes in preschools, andtheir use as a tool for learning about dinosaurs, fossilsand natural history. A survey of teachers and childrenfound that both increased their knowledge base throughthis approach, and that the local context of the fossilsin particular generated interest about the subject. Theconcepts of geological time was similarly addressed in thesecond study, which utilized timescale projects and otherhands-on activities to create memory triggers for childrenand students, and to demonstrate how the perspective of‘deep time’ is relevant for understanding large-scale Earthprocesses, such as evolution and environmental change.The integration of geosciences into the Swedish schoolcurriculum is currently inadequate. Therefore, the finalpaper in this sequence discusses how geosciences forman interdisciplinary bridge between school subjects andcan be used to teach geography and biology at all schoollevels.
|
|
| 23. |
- Ferrow, Embaie, et al.
(author)
-
Multiproxy analysis of a new terrestrial and a marine Cretaceous-Paleogene (K-Pg) boundary site from New Zealand
- 2011
-
In: Geochimica et Cosmochimica Acta. - : Elsevier BV. - 0016-7037. ; 75:2, s. 657-672
-
Journal article (peer-reviewed)abstract
- An integrated study of palynology, Mossbauer spectroscopy, mineralogy and osmium isotopes has led to the detection of the first K-Pg boundary clay layer in a Southern Hemisphere terrestrial setting. The K-Pg boundary layer was independently identified at centimetre resolution by all the above mentioned methods at the marine K-Pg boundary site of mid-Waipara and the terrestrial site of Compressor Creek (Greymouth coal field), New Zealand. Mossbauer spectroscopy shows an anomaly of Fe-containing particles in both K-Pg boundary sections: jarosite at mid-Waipara and goethite at Compressor Creek. This anomaly coincides with a turnover in vegetation indicated by an interval dominated by fern spores and extinction of key pollen species in both sections. In addition to the terrestrial floristic changes, the mid-Waipara section reveals a turnover in the dinoflagellate assemblages and the appearance of global earliest Danian index species. Geochemical data reveal relatively small iridium enrichments in the boundary layers of 321 pg/g at mid-Waipara and 176 pg/g at Compressor Creek. Unradiogenic Os-187/Os-188 values of the boundary clay reveal the presence of a significant extraterrestrial component. We interpret the accumulation of Fe nano-phases at the boundary as originating from both the impactor and the crystalline basement target rock. The goethite and jarosite are interpreted as secondary phases formed by weathering and diagenesis. The primary phases were probably controlled by the initial composition of the vapor plume and condensation kinetics rather than condensation thermodynamics. This investigation indicates that identification of Fe in nano-phases by Mossbauer spectroscopy is an accurate and cost-effective method for identifying impact event horizons and it efficiently complements widely used biostratigraphic and geochemical methods. (C) 2010 Elsevier Ltd. All rights reserved.
|
|
| 24. |
- Field, Daniel J, et al.
(author)
-
Early Evolution of Modern Birds Structured by Global Forest Collapse at the End-Cretaceous Mass Extinction
- 2018
-
In: Current Biology. - Amsterdam : Elsevier. - 0960-9822 .- 1879-0445. ; 28, s. 1825-1831
-
Journal article (peer-reviewed)abstract
- The fossil record and recent molecular phylogenies support an extraordinary early-Cenozoic radiation of crown birds (Neornithes) after the Cretaceous-Paleogene (K-Pg) mass extinction [1–3 ]. However, questions remain regarding the mechanisms underlying the survival of the deepest lineages within crown birds across the K-Pg boundary, particularly since this global catastrophe eliminated even the closest stem-group relatives of Neornithes [4 ]. Here, ancestral state reconstructions of neornithine ecology reveal a strong bias toward taxa exhibiting predominantly non-arboreal lifestyles across the K-Pg, with multiple convergent transitions toward predominantly arboreal ecologies later in the Paleocene and Eocene. By contrast, ecomorphological inferences indicate predominantly arboreal lifestyles among enantiornithines, the most diverse and widespread Mesozoic avialans [5–7 ]. Global paleobotanical and palynological data show that the K-Pg Chicxulub impact triggered widespread destruction of forests [8, 9 ]. We suggest that ecological filtering due to the temporary loss of significant plant cover across the K-Pg boundary selected against any flying dinosaurs (Avialae [10 ]) committed to arboreal ecologies, resulting in a predominantly non-arboreal postextinction neornithine avifauna composed of totalclade Palaeognathae, Galloanserae, and terrestrial total-clade Neoaves that rapidly diversified into the broad range of avian ecologies familiar today. The explanation proposed here provides a unifying hypothesis for the K-Pg-associated mass extinction of arboreal stem birds, as well as for the post-K-Pg radiation of arboreal crown birds. It also provides a baseline hypothesis to be further refined pending the discovery of additional neornithine fossils from the Latest Cretaceous and earliest Paleogene.
|
|
| 25. |
- Fielding, Christopher, et al.
(author)
-
Age and pattern of the southern high-latitude continental end-Permian extinction constrained by multiproxy analysis
- 2019
-
In: Nature Communications. - London : Springer Science and Business Media LLC. - 2041-1723. ; 10:385, s. 1-12
-
Journal article (peer-reviewed)abstract
- Past studies of the end-Permian extinction (EPE), the largest biotic crisis of the Phanerozoic, have not resolved the timing of events in southern high-latitudes. Here we use palynology coupled with high-precision CA-ID-TIMS dating of euhedral zircons from continental sequences of the Sydney Basin, Australia, to show that the collapse of the austral Permian Glossopteris flora occurred prior to 252.3 Ma (~370 kyrs before the main marine extinction). Weathering proxies indicate that floristic changes occurred during a brief climate perturbation in a regional alluvial landscape that otherwise experienced insubstantial change in fluvial style, insignificant reorganization of the depositional surface, and no abrupt aridification. Palaeoclimate modelling suggests a moderate shift to warmer summer temperatures and amplified seasonality in temperature across the EPE, and warmer and wetter conditions for all seasons into the Early Triassic. The terrestrial EPE and a succeeding peak in Ni concentration in the Sydney Basin correlate, respectively, to the onset of the primary extrusive and intrusive phases of the Siberian Traps Large Igneous Province.
|
|
