| 1. |
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| 2. |
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| 3. |
- Ahlberg, Per, et al.
(författare)
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Furongian (Cambrian) agnostoids of Scandinavia and their implications for intercontinental correlation
- 2012
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Ingår i: Geological Magazine. - 0016-7568. ; 149:6, s. 1001-1012
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Tidskriftsartikel (refereegranskat)abstract
- Out of the 14 agnostoid species/subspecies so far recorded from the Furongian of Scandinavia, seven are excellent biostratigraphical indices and important for correlation between Baltica and other palaeocontinents. Glyptagnostus reticulatus, Aspidagnostus lunulosus and Agnostus (Homagnostus) obesus first appear at the base of the G. reticulatus Zone, allowing a precise correlation of the base of the Paibian Stage into Scandinavia. Tomagnostella orientalis and Psettdagnostus cyclopyge appear near the base of the Parabolina brevispina Zone, suggesting a correlation with the uppermost Paibian through the lowermost Jiangshanian stages. Lotagnostus americanus and Pseudagnostus rugosus have an intercontinental distribution and their first appearance in Scandinavia allows for a correlation with one of the most favourable levels for defining the base of Cambrian provisional Stage 10. In the Furongian of Scandinavia, agnostoids are conspicuously assembled in three different intervals: the lower Glyptagnostus reticulatus Zone, the lower Psettdagnostus cyclopyge Zone and the Lotagnostus americanus through lower Trilobagnostus holmi zones. The agnostoid-barren and largely unfossiliferous succession separating the lower and middle agnostoid-bearing intervals can be explained by means of subsequent dissolution of the calcareous fauna and/or a hostile environment. The middle agnostoid-bearing interval is succeeded by an anomalous succession dominated by the orthide brachiopod Orusia lenticularis, reflecting a regressive event coupled with increasing levels of oxygen at the sediment/water interface. This shallowing evidently resulted in unfavourable conditions for agnostoids.
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| 4. |
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| 5. |
- Bergstrom, Stig M., et al.
(författare)
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High-resolution δ13Corg chemostratigraphy links the Decorah impact structure and Winneshiek Konservat-Lagerstätte to the Darriwilian (Middle Ordovician) global peak influx of meteorites
- 2018
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Ingår i: Lethaia. - : Scandinavian University Press / Universitetsforlaget AS. - 0024-1164 .- 1502-3931. ; 51:4, s. 504-512
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Tidskriftsartikel (refereegranskat)abstract
- The precise age of the Winneshiek Shale, a recently discovered Konservat-Lagerstätte located in a very unusual depositional setting inside the Decorah impact structure, has remained uncertain in the absence of biostratigraphically highly diagnostic fossils. This chemostratigraphical study, based on δ13Corg data from 36 drill core samples through the shale, shows that the age ranges from the upper part of a small unnamed δ13C excursion in the Dw1 Stage Slice of the Darriwilian Global Stage to the lower part of the MDICE excursion in Stage Slice Dw2 of the same stage. This Dw1-Dw2 interval has an isotopic age of ~464-467 Ma. The gradational contact between the Winneshiek Shale and the underlying, rapidly deposited, impact breccia indicates minimal time difference between the impact event and the Winneshiek Shale. New age data show that the Decorah impact event was coeval with the early Darriwilian abnormally high influx of micrometeorites and meteorites recorded in sections in Baltoscandia, Russia and China and that the Decorah crater can be included among the unusually large number of meteorite craters formed during Middle and early Late Ordovician time. As is commonly the case in black shale deposits, the partly uniquely preserved Winneshiek Shale crater fauna is impoverished taxonomically and adds numerically relatively little to the conspicuous and much discussed Darriwilian global biodiversification increase.
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| 6. |
- Bergström, Stig M., et al.
(författare)
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Local and trans-Atlantic chemostratigraphic significance of new δ13Ccarb data from the Sandbian and Katian Stages (Middle–Upper Ordovician) of the Oslo region, Norway
- 2017
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Ingår i: GFF. - : Informa UK Limited. - 1103-5897 .- 2000-0863. ; 139:4, s. 289-300
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Tidskriftsartikel (refereegranskat)abstract
- Late Sandbian to early Katian δ13Ccarb chemostratigraphy has in Norway been described in only two previous reports that dealt with two geographically rather widely separated areas, namely the Oslo-Asker district and the Nes-Hamar district. No data have been available from the Ordovician outcrop areas between these districts that could help clarify the partly unclear regional stratigraphic relations across the Oslo region. A chemostratigraphic study of the classical road section at Tønnerud in the northwestern Hadeland district about halfway between the previously investigated districts resulted in the recognition of two δ13C excursions, namely one in the uppermost Furuberget Formation tentatively identified as the Guttenberg Isotopic Carbon Excursion and one in the lower Solvang Formation that is classified as the KOPE (RAKVERE) excursion. Based on these results, the Furuberget and Solvang formations are interpreted to be separated by a significant gap in the study area corresponding to the Oandu and lower Rakvere regional Baltoscandic stages. This suggests that the Tønnerud succession is less complete stratigraphically than those in the Oslo-Asker district. Similar gaps are not uncommon in this interval in Baltoscandia and in North America and probably reflect both eustatic and local epeirogenetic movements that make it difficult to establish a regionally applicable sequence stratigraphy.
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| 7. |
- Bergström, Stig M., et al.
(författare)
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Obituary Lennart Jeppsson 1940-2015
- 2015
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Ingår i: The Palaeontological Association Newsletter. - 0954-9900. ; 89, s. 103-105
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 8. |
- Bergström, Stig M., et al.
(författare)
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The age of the Middle Ordovician Winneshiek Shale : reply to a critical review by Lindskog & Young (2019) of a paper by Bergström et al. (2018a)
- 2020
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Ingår i: Lethaia. - : Scandinavian University Press / Universitetsforlaget AS. - 0024-1164 .- 1502-3931. ; 53:1, s. 1-4
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Tidskriftsartikel (refereegranskat)abstract
- A recent review by Lindskog & Young (2019) of a paper published in Lethaia by Bergström et al. (2018a) contains many errors, misleading statements and unsupported opinions. Their review claims that we did not consider biostratigraphy in our efforts to chemostratigraphically date the Winneshiek Shale. That this is incorrect is shown by the fact that Liu et al. (2017), which contains a two-page review of all fossil evidence that has a bearing on the age of the Winneshiek Shale and was written by Bergström, was cited in Bergström et al. (2018a) and used extensively in our chemostratigraphical age assessment of the unit. Interestingly, recent research provides support for our conclusion regarding the age of the Winneshiek Shale, indicating that at least its upper part is coeval with the Nicholsonograptus fasciculatus Graptolite Zone and the Eoplacognathus pseudoplanus Conodont Zone. In constructing their arguments, Lindskog & Young (2019) provide no alternative interpretations or corrections of scientific value.
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| 9. |
- Bergström, Stig M., et al.
(författare)
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The δ13C chemostratigraphy of Ordovician global stage stratotypes : geochemical data from the Floian and Sandbian GSSPs in Sweden
- 2020
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Ingår i: GFF. - : Informa UK Limited. - 1103-5897 .- 2000-0863. ; 142:1, s. 23-32
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Tidskriftsartikel (refereegranskat)abstract
- The δ13C chemostratigraphy of five of the seven Ordovician global stages has been published previously but no such data have been available from the Floian GSSP and most of the Sandbian GSSP in Sweden. This lack of information has now been remedied by isotope data obtained from series of closely spaced shale samples collected from the Floian stratotype at Diabasbrottet in Västergötland and the Sandbian stratotype at Fågelsång in Scania. Although the bases of these stages cannot be precisely tied to levels of conspicuous δ13C excursions, that of the Floian Stage, which is marked by the appearance of the graptolite Tetragraptus approximatus, is between the closely spaced excursions named LTNICE and BFICE. The base of the Sandbian Stage, which is defined as the appearance level of the graptolite Nemagraptus gracilis, is just below a negative excursion previously known as the “Upper Kukruse Low”, which is nowadays known as the LSNICE. The relations between chemostratigraphy and graptolite and conodont biostratigraphy in the Swedish GSSPs and some coeval key sections in Baltoscandia, China, and America are briefly discussed. It is concluded that the data at hand indicate that there is good regional agreement in these relations.
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| 10. |
- Boschi, Samuele, et al.
(författare)
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Late Eocene 3He and Ir anomalies associated with ordinary chondritic spinels
- 2017
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Ingår i: Geochimica et Cosmochimica Acta. - : Elsevier BV. - 0016-7037. ; 204, s. 205-218
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Tidskriftsartikel (refereegranskat)abstract
- During the late Eocene there was an enigmatic enhancement in the flux of extraterrestrial material to Earth. Evidence comes from sedimentary 3He records indicating an increased flux of interplanetary dust during ca. 2 Myr, as well as two very large impact structures, Popigai (100 km diameter) and Chesapeake Bay (40–85 km), that formed within 10–20 kyr at the peak of the 3He delivery. The Massignano section in Italy has one of the best sedimentary records of these events, including a well-defined 3He record, an Ir-rich ejecta bed related to the Popigai impact event, and two smaller Ir anomalies. Recently we showed that the Popigai ejecta is associated with a significant enrichment of chromite grains (>63 μm) with an H-chondritic elemental composition (17 grains in 100 kg of rock). Most likely these grains are unmelted fragments from the impactor. Slightly higher up (ca. 20 cm) in the section, where a small Ir anomaly possibly related to the Chesapeake Bay impact has been measured, we found a weak enrichment in L-chondritic grains (8 grains in 208 kg of rock). Here we report an extended data set increasing the total amount of sediment dissolved in acid and searched for extraterrestrial chromite grains from 658 to 1168 kg. In altogether 760 kg of background sediment from 17 levels over 14 m of strata outside the interval corresponding to the Popigai and Chesapeake Bay impacts, we only found 2 extraterrestrial chromite grains. Both grains have L-chondritic compositions and were found in a 100 kg sample from the ca. 10.25 m level in the section where the second of the smaller Ir anomalies has been reported. A correlation appears to exist between Ir, 3He and chromite from ordinary chondrites. We also report oxygen three-isotope measurements of the extraterrestrial chromite grains associated with the Popigai ejecta and confirm an H-chondritic composition. The new results strengthen our scenario that the upper Eocene 3He and Ir enrichments originate from the asteroid belt rather than the Oort cloud as originally proposed when the 3He anomaly was discovered. The generally low background concentrations of extraterrestrial chromite through the section speak against any major single asteroid breakup event such as in the mid-Ordovician after the break-up of the L-chondrite parent body. Instead the data reconcile with a small, possibly a factor of 2–3, increase in the flux of extraterrestrial material to Earth, but of both H- and L-chondritic composition. We also report the composition of all the 2310 terrestrial chrome spinel grains recovered, and show that their chemical composition indicates a dominantly regional ophiolitic source. Four anomalous chrome spinel grains with high Ti and V concentrations were found in the Popigai ejecta. These grains originate from Siberian Traps basalts in the Popigai crater at the time of impact.
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| 11. |
- Boschi, Samuele, et al.
(författare)
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Popigai impact ejecta layer and extraterrestrial spinels recovered in a new Italian location—The Monte Vaccaro section (Marche Apennines, Italy)
- 2019
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Ingår i: 250 Million Years of Earth History in Central Italy: Celebrating 25 Years of the Geological Observatory of Coldigioco. - : Geological Society of America. - 0072-1077. ; 542, s. 355-367
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- The Popigai (100 km in diameter) and the Chesapeake Bay (40–85 km diameter) impact structures formed within ~10–20 k.y. in the late Eocene during a 2 m.y. period with enhanced flux of 3He-rich interplanetary dust to Earth. Ejecta from the Siberian Popigai impact structure have been found in late Eocene marine sediments at numerous deep-sea drilling sites around the globe and also in a few marine sections outcropped on land, like the Massignano section near Ancona in Italy. In the Massignano section, the Popigai layer is associated with an iridium anomaly, shocked quartz, and abundant clinopyroxene-bearing (cpx) spherules, altered to smectite and flattened to “pancake spherules.” The ejecta are also associated with a significant enrichment of H-chondritic chromite grains (>63 µm), likely representing unmelted fragments of the impactor. The Massignano section also contains abundant terrestrial chrome-spinel grains, making reconstructions of the micrometeorite flux very difficult. We therefore searched for an alternative section that would be more useful for these types of studies. Here, we report the discovery of such a section, and also the first discovery of the Popigai ejecta in another locality in Italy, the Monte Vaccaro section, 90 km west of Ancona. The Monte Vaccaro section biostratigraphy was established based on calcareous nannoplankton, which allowed the identification of a sequence of distinct bioevents showing a good correlation with the Massignano section. In both the Monte Vaccaro and Massignano sections, the Popigai ejecta layer occurs in calcareous nannofossil zone CNE 19. The ejecta layer in the Monte Vaccaro section contains shocked quartz, abundant pancake spherules, and an iridium anomaly of 700 ppt, which is three times higher than the peak Ir measured in the ejecta layer at Massignano. In a 105-kg-size sample from just above the ejecta layer at Monte Vaccaro, we also found an enrichment of H-chondritic chromite grains. Because of its condensed nature and low content of terrestrial spinel grains, the Monte Vaccaro section holds great potential for reconstructions of the micrometeorite flux to Earth during the late Eocene using spinels.
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| 12. |
- Boschi, Samuele, et al.
(författare)
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The micrometeorite flux to Earth during the earliest Paleogene reconstructed in the Bottaccione section (Umbrian Apennines), Italy
- 2020
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Ingår i: Meteoritics and Planetary Science. - : Wiley. - 1086-9379 .- 1945-5100. ; 55:7, s. 1615-1628
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Tidskriftsartikel (refereegranskat)abstract
- Based on sediment-dispersed extraterrestrial spinel grains in the Bottaccione limestone section in Italy, we reconstructed the micrometeorite flux to Earth during the early Paleocene. From a total of 843 kg of limestone, 86 extraterrestrial spinel grains (12 grains > 63 μm, and 74 in the 32–63 μm fraction) have been recovered. Our results indicate that the micrometeorite flux was not elevated during the early Paleocene. Ordinary chondrites dominated over achondritic meteorites similar to the recent flux, but H chondrites dominated over L and LL chondrites (69%, 22%, and 9%, respectively). This H-chondrite dominance is similar to that recorded within an enigmatic 3He anomaly (70, 27, and 3%) in the Turonian, but different from just before this 3He anomaly and in the early Cretaceous, where ratios are similar to the recent flux (~45%, 45%, and 10%). The K-Ar isotopic ages of recently fallen H chondrites indicate a small impact event on the H-chondrite parent body ~50 to 100 Ma ago. We tentatively suggest that this event is recorded by the Turonian 3He anomaly, resulting in an H-chondrite dominance up to the Paleocene. Our sample spanning the 20 cm above the Cretaceous–Paleogene (K–Pg) boundary did not yield any spinel grains related to the K–Pg boundary impactor.
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| 13. |
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| 14. |
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| 15. |
- Eriksson, Mats, et al.
(författare)
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Anomalous facies and ancient faeces in the latest middle Cambrian of Sweden
- 2007
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Ingår i: Lethaia. - : Scandinavian University Press / Universitetsforlaget AS. - 0024-1164. ; 40:1, s. 69-84
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Tidskriftsartikel (refereegranskat)abstract
- The middle Cambrian -Furongian transitional interval was a time of significant biotic and environmental changes. Strata of this age in Scania, southern Sweden, contain two interlayered biofacies, a normal one dominated by trilobites and an anomalous one dominated by phosphatocopines (small bivalved arthropods). In places these biofacies are separated by intervals barren of fossils. In a phosphatocopine facies without trilobites in the upper Agnostus pisiformis Zone at Andrarum we recovered scattered fossil aggregates with a homogeneous composition of tightly packed and stacked phosphatocopines. These aggregates are interpreted as coprolites produced by an undetermined predator, possibly the chaetognath-like protoconodont animal or some other softbodied metazoan. The so-called barren intervals of Scania are not necessarily barren of fossils, but only trilobites, brachiopods, and other skeletal elements with a calcium-carbonate composition. The phosphatocopine facies with coprolites in the uppermost part of the A. pisiformis Zone correlates with the trilobite mass extinction at the top of the Marjumiid Biomere in Laurentia and immediately prior to the onset of the Steptoean Positive Carbon Isotope Excursion (SPICE), inferring a global shift in the oceanic chemistry that in Scania favoured phosphatocopines over the more common, trilobite-dominated faunas.
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| 16. |
- Eriksson, Mats, et al.
(författare)
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Baring it all- undressing Cambrian ´Orsten´phosphatocopine arthropods using synchrotron X-ray tomographic microscopy
- 2016
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Ingår i: Lethaia. - : Scandinavian University Press / Universitetsforlaget AS. - 0024-1164. ; 49:3, s. 312-326
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Tidskriftsartikel (refereegranskat)abstract
- Synchrotron radiation X-ray tomographic microscopy (SRXTM) was used to virtually dissect and peel the shields off of the microscopic, bivalved phosphatocopine crustaceans in the Cambrian ‘Orsten’ type of preservation of Sweden. Doing so opened up for an array of concealed internal structures to be observed in a fully enclosed specimen of Hesslandona ventrospinata and a semi-enclosed specimen of Hesslandona angustata. For comparison, also a head-larva stage specimen of H. angustata, with shields in ‘butterfly position’, was analysed. The X-ray tomographic data sets revealed excellently preserved structures, such as labrum, sternum, antennae, mandibular and post-mandibular limbs with their minute setae, all of which were more or less dis-guised by the enclosing shields. This, moreover, allowed assignment to growth stages of the specimens, which is impossible based solely on external morphology and size.Microspherules observed inside the shields of the semi-enclosed H. angustata specimen may represent remains of food particles, and the feeding biology of phosphatocopines is discussed in detail. Our analyses suggest that phosphatocopines were particle feeders. The SRXTM technique offers the ability to three-dimensionally reconstruct the morphology in high resolution, construct virtual serial sections and study concealed structures. The resulting data allow for new structures to be revealed for previously known taxa and for new taxa to be identified, with the added benefit of not destroying the specimens in the process. Hence, we do not longer have to rely on serendipitous finds of broken and/or open phosphatocopine specimens to elucidate their diagnostic ventral morphology.
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| 17. |
- Eriksson, Mats, et al.
(författare)
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Biotic dynamics and carbonate microfacies of the conspicuous Darriwilian (Middle Ordovician) 'Taljsten' interval, south-central Sweden
- 2012
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Ingår i: Palaeogeography, Palaeoclimatology, Palaeoecology. - : Elsevier BV. - 1872-616X .- 0031-0182. ; 367, s. 89-103
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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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| 18. |
- Eriksson, Mats, et al.
(författare)
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Exceptionally Preserved Cambrian Trilobite Digestive System Revealed in 3D by Synchrotron-Radiation X-Ray Tomographic Microscopy.
- 2012
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Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 7:4
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Tidskriftsartikel (refereegranskat)abstract
- The Cambrian 'Orsten' fauna comprises exceptionally preserved and phosphatised microscopic arthropods. The external morphology of these fossils is well known, but their internal soft-tissue anatomy has remained virtually unknown. Here, we report the first non-biomineralised tissues from a juvenile polymerid trilobite, represented by digestive structures, glands, and connective strands harboured in a hypostome from the Swedish 'Orsten' fauna. Synchrotron-radiation X-ray tomographic microscopy enabled three-dimensional internal recordings at sub-micrometre resolution. The specimen provides the first unambiguous evidence for a J-shaped anterior gut and the presence of a crop with a constricted alimentary tract in the Trilobita. Moreover, the gut is Y-shaped in cross section, probably due to a collapsed lumen of that shape, another feature which has not previously been observed in trilobites. The combination of anatomical features suggests that the trilobite hypostome is functionally analogous to the labrum of euarthropods and that it was a sophisticated element closely integrated with the digestive system. This study also briefly addresses the preservational bias of the 'Orsten' fauna, particularly the near-absence of polymerid trilobites, and the taphonomy of the soft-tissue-harbouring hypostome.
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| 19. |
- Eriksson, Mats, et al.
(författare)
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Fossilt bajs berättar om rovdjur
- 2008
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Ingår i: Forskning & framsteg. - 0015-7937. ; 2008:3, s. 54-55
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Tidskriftsartikel (populärvet., debatt m.m.)
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| 20. |
- Eriksson, Mats, et al.
(författare)
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Internal soft-tissue anatomy of cambrian 'orsten' arthropods as revealed by synchrotron x-ray tomographic microscopy.
- 2012
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Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 7:8
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Tidskriftsartikel (refereegranskat)abstract
- The world-famous 'Orsten' Konservat-Lagerstätte has yielded detailed information about Cambrian arthropods and their morphology. Internal organs or soft tissues have, however, rarely been reported, an obvious palaeobiological drawback. In this study, we employed synchrotron radiation X-ray tomographic microscopy (SRXTM) to study microscopic 'Orsten' arthropods from the Cambrian of Sweden: Skara minuta and two phosphatocopine species, Hesslandona sp. and Hesslandona trituberculata. This exceptionally high-resolution technique reveals internal organs or soft tissues that allow detailed comparison with equivalent structures in extant crustaceans and functional inferences to be made. The S. minuta specimen shows the digestive system and muscles that extend to the extremities. The slanting anterior portion of the head and anterior position of the mouth with a straight oesophagus suggest a primarily brushing and scraping way of feeding. The prominent head appendage muscles indicate muscle strength and good capacity for food manipulation. In the phosphatocopines the bulbous labrum is one of the most prominent morphological structures of the body. All specimens analysed reveal pairs of muscle bundles within the labrum. Based on comparisons with extant crustacean relatives, these muscles would fulfil the function of moving the labrum up and down in order to open the buccal cavity. The results of this pilot study demonstrate that there is still much to be learned about the 'Orsten' taxa.
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| 21. |
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| 22. |
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| 23. |
- Heck, Philipp R., et al.
(författare)
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Unusual sources of fossil micrometeorites deduced from relict chromite in the small size fraction in ~467 Ma old limestone
-
Ingår i: Meteoritics and Planetary Science. - 1086-9379.
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Tidskriftsartikel (refereegranskat)abstract
- Extraterrestrial chrome spinel and chromite extracted from the sedimentary rock record are relicts from coarse micrometeorites and rarely meteorites. They are studied to reconstruct the paleoflux of meteorites to the Earth and the collisional history of the asteroid belt. Minor element concentrations of Ti and V, and oxygen isotopic compositions of these relict minerals were used to classify the meteorite type they stem from, and thus to determine the relative meteorite group abundances through time. While coarse sediment-dispersed extraterrestrial chrome-spinel (SEC) grains from ordinary chondrites dominate through the studied time windows in the Phanerozoic, there are exceptions: We have shown that ~467 Ma ago, 1 Ma before the breakup of the L chondrite parent body (LCPB), more than half of the largest (>63 μm diameter) grains were achondritic and originated from differentiated asteroids in contrast to ordinary chondrites which dominated the meteorite flux throughout most of the past 500 Ma. Here, we present a new data set of oxygen isotopic compositions and elemental compositions of 136 grains of a smaller size fraction (32–63 μm) in ~467 Ma old pre-LCPB limestone from the Lynna River section in western Russia, that was previously studied by elemental analysis. Our study constitutes the most comprehensive oxygen isotopic data set of sediment-dispersed extraterrestrial chrome spinel to date. We also introduce a Raman spectroscopy-based method to identify SEC grains and distinguish them from terrestrial chrome spinel with ~97% reliability. We calibrated the Raman method with the established approach using titanium and vanadium concentrations and oxygen isotopic compositions. We find that ordinary chondrites are approximately three times more abundant in the 32–63 μm fraction than achondrites. While abundances of achondrites compared to ordinary chondrites are lower in the 32–63 μm size fraction than in the >63 μm one, achondrites are approximately three times more abundant in the 32–62 μm fraction than they are in the present flux. We find that the sources of SEC grains vary for different grain sizes, mainly as a result of parent body thermal metamorphism. We conclude that the meteorite flux composition ~467 Ma ago ~1 Ma before the breakup of the LCPB was fundamentally different from today and from other time windows studied in the Phanerozoic, but that in contrast to the large size fraction ordinary chondrites dominated the flux in the small size fraction. The high abundance of ordinary chondrites in the studied samples is consistent with the findings based on coarse extraterrestrial chrome-spinel from other time windows.
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| 24. |
- Lindskog, Anders, et al.
(författare)
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Mollusk maxima and marine events in the Middle Ordovician of Baltoscandia
- 2015
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Ingår i: Palaeogeography, Palaeoclimatology, Palaeoecology. - : Elsevier BV. - 1872-616X .- 0031-0182. ; 440, s. 53-65
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Tidskriftsartikel (refereegranskat)abstract
- Except for the scattered cephalopod conchs that have given the rock type its name, mollusk fossils are relatively rare in the Middle Ordovician 'orthoceratite limestone' of Sweden. However, an interval in the Darnwilian stands out as being unusually rich in various types of mollusks. Throughout southern Sweden, gastropods became relatively abundant close to the Volkhov-Kunda Baltoscandian Stage boundary, and their numbers increase significantly in the Kundan. This increase is most apparent in the microscopic realm. A distinct peak in abundance is seen toward the middle Kundan, across the boundary between the regionally recognized Asaphus expansus and Asaphus raniceps trilobite zones, close to the Lenodus variabilis-Yangtzeplacognathus crassus conodont Zone boundary (Dw1-Dw2 transition). Hyoliths, which are otherwise exceptionally rare, are also more common in these beds, as are putative bivalves. Moreover, macroscopic cephalopod conchs occur in unusually high numbers. Gastropods and other small mollusks become relatively rare again in the upper half of the Kundan, but cephalopods are concentrated in some beds. The mollusk-rich intervals coincide with diverse assemblages and multiple morphotypes were distinguished. Point counting of skeletal grains in thin sections showed that the relative abundance of gastropods fluctuates in a pulse-like (cyclic?) manner throughout the studied succession. The concurrent paleontologic and sedimentologic development suggests a correlation to sea level, and thus that gastropod abundance can be used as a paleobathymetric proxy. Abundance peaks are associated with inferred lowstand intervals. Closely similar abundance patterns throughout southern Sweden suggest that the increase in mollusks was a geographically widespread phenomenon, perhaps even global in extent. (C) 2015 Elsevier B.V. All rights reserved.
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| 25. |
- Lindskog, Anders, et al.
(författare)
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Palaeozoic 'conodont pearls' and other phosphatic micro-spherules
- 2017
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Ingår i: Lethaia. - : Scandinavian University Press / Universitetsforlaget AS. - 0024-1164. ; 50:1, s. 26-40
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Tidskriftsartikel (refereegranskat)abstract
- Sub-millimetre-sized phosphatic spherules are often found in acetic acid-insoluble residues produced for microfossil extraction. As they are typically associated with conodont elements and have a similar chemical composition, they are informally known as 'conodont pearls'. Still, the origin of these micro-spherules has been controversial, and authors have disagreed regarding their mode of formation, or if they are biogenic or not. In this study, an assortment of micro-spherules from several localities and stratigraphical levels were analysed using multiple methods, in an effort to shed light on the origin of these enigmatic objects: ocular investigation with a stereomicroscope, chemical analyses employing energy-dispersive mass spectrometry, imaging through scanning electron microscope, and synchrotron radiation X-ray tomographic microscopy. Collectively, the techniques employed allow for near-complete characterization and description of the study specimens. At least five different groups, or morphotypes, of spherules can be discerned, which differ both in morphological and chemical details. Most specimens are notably spherical and display concentric layers of growth. Several of the specimens have a central nucleus, sometimes with one or more objects located closely together. Internal details and chemistry suggest that the phosphatic spherules probably are of different origin. Thus, the term 'conodont pearl' encompasses confusingly similar objects deriving from different organisms and/or processes, and only careful analysis can reveal their individual origin. The only organisms unequivocally associated with (in situ) phosphatic micro-spherules are ceramoporid bryozoans, and the conodonts Cordylodus and Westergaardodina, but the possible function and significance of these objects remain enigmatic.
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| 26. |
- Nielsen, Arne Thorshoj, et al.
(författare)
-
Upper Cambrian (Furongian) biostratigraphy in Scandinavia revisited: definition of superzones
- 2014
-
Ingår i: GFF. - : Informa UK Limited. - 2000-0863 .- 1103-5897. ; 136:1, s. 193-197
-
Tidskriftsartikel (refereegranskat)abstract
- The traditional Furongian trilobite biozones of Scandinavia, recently proposed abandoned due to inconsistent boundary definitions [Terfelt, F., Eriksson, M.E., Ahlberg, P. & Babcock, L.E., 2008: Furongian Series (Cambrian) biostratigraphy of Scandinavia - a revision. Norwegian Journal of Geology88, 73-87], are resurrected and elevated to superzonal rank. These superzones are usually readily recognized in the field, even by non-specialists, and for general correlation and mapping the more wide-ranging biozones are considerably more practicable than the very detailed zonation (formerly subzonation) introduced by Terfelt et al. (2008). Formal definition of the superzones is outlined including designation of stratotype sections. The superzones are each defined by the FAD of a characterizing species group and upwards delimited by the base of the succeeding superzone. The long used Olenus, Parabolina and Leptoplastus (super)zones as well as the recently introduced Acerocarina Superzone (= Acerocare Zone of older literature) are maintained and formalized. The Protopeltura praecursor, Peltura minor and Peltura scarabaeoides zones are abandoned and replaced by two new units, named the Protopeltura and Peltura superzones, respectively. Accordingly, all Furongian superzones have a uniform naming style referring to a characteristic genus. The six Furongian superzones currently comprise 27 trilobite zones. The Paradoxides forchhammeri Superzone (Cambrian Series 3) is extended upwards to the base of the Olenus Superzone, thereby formally including the Agnostus pisiformis Zone.
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| 27. |
- Peng, Shanchi, et al.
(författare)
-
Intraspecific variation and taphonomic alteration in the Cambrian (Furongian) agnostoid Lotagnostus amerkanus: new information from China
- 2015
-
Ingår i: Bulletin of Geosciences. - : Czech Geological Survey. - 1214-1119 .- 1802-8225. ; 90:2, s. 281-306
-
Tidskriftsartikel (refereegranskat)abstract
- The concept of the agnostoid arthropod species Lotagnostus americanus (Billings, 1860), which has been reported from numerous localities in the upper Furongian Series (Cambrian) of Laurentia, Gondwana, Baltica, Avalonia, and Siberia, is reviewed with emphasis on morphologic and taphonomic information afforded by large collections from Hunan in South China, Xinjiang in Northwest China, and Zhejiang in Southeast China. Comparisons are made with type and topotype material from Quebec, Canada, as well as material from elsewhere in Canada, the USA, the United Kingdom, Sweden, Russia, and Kazakhstan. The new information clarifies the limits of morphologic variability in L. americanus owing to ontogenetic changes and variation within holaspides, including inferred microevolution. It also provides details on apparent variation of taphonomic origin. The Chinese collections demonstrate a moderately wide variation in L. americanus, indicating that arguments favoring restriction of Lotagnostus species to narrowly defined, geographically restricted forms are unwarranted. Species described as L. trisectus (Salter, 1864), L. asiaticus Troedsson, 1937, and L. punctatus Lu, 1964, for example, fall within the range of variation observed in L. americanus, and are regarded as junior synonyms. The effaced form Lotagnosilis obscurus Palmer, 1955 is removed from synonymy with L. americanus. A review of the stratigraphic distribution of L. americanus as construed here shows that the earliest occurrences of the species in all regions of the world are nearly synchronous.
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| 28. |
- Schmitz, Birger, et al.
(författare)
-
A fossil winonaite-like meteorite in Ordovician limestone: A piece of the impactor that broke up the L-chondrite parent body?
- 2014
-
Ingår i: Earth and Planetary Science Letters. - : Elsevier BV. - 1385-013X .- 0012-821X. ; 400, s. 145-152
-
Tidskriftsartikel (refereegranskat)abstract
- About a quarter of all meteorites falling on Earth today originate from the breakup of the L-chondrite parent body similar to 470 Ma ago, the largest documented breakup in the asteroid belt in the past similar to 3 Ga. A window into the flux of meteorites to Earth shortly after this event comes from the recovery of about 100 fossil L chondrites (1-21 cm in diameter) in a quarry of mid-Ordovician limestone in southern Sweden. Here we report on the first non-L-chondritic meteorite from the quarry, an 8 cm large winonaite-related meteorite of a type not known among present-day meteorite falls and finds. The noble gas data for relict spinels recovered from the meteorite show that it may be a remnant of the body that hit and broke up the L-chondrite parent body, creating one of the major asteroid families in the asteroid belt. After two decades of systematic recovery of fossil meteorites and relict extraterrestrial spinel grains from marine limestone, it appears that the meteorite flux to Earth in the mid-Ordovician was very different from that of today. (C) 2014 The Authors. Published by Elsevier B.V.
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| 29. |
- Schmitz, Birger, et al.
(författare)
-
An extraterrestrial trigger for the mid-Ordovician ice age : Dust from the breakup of the L-chondrite parent body
- 2019
-
Ingår i: Science Advances. - : American Association for the Advancement of Science (AAAS). - 2375-2548. ; 5:9
-
Tidskriftsartikel (refereegranskat)abstract
- The breakup of the L-chondrite parent body in the asteroid belt 466 million years (Ma) ago still delivers almost a third of all meteorites falling on Earth. Our new extraterrestrial chromite and 3He data for Ordovician sediments show that the breakup took place just at the onset of a major, eustatic sea level fall previously attributed to an Ordovician ice age. Shortly after the breakup, the flux to Earth of the most fine-grained, extraterrestrial material increased by three to four orders of magnitude. In the present stratosphere, extraterrestrial dust represents 1% of all the dust and has no climatic significance. Extraordinary amounts of dust in the entire inner solar system during >2 Ma following the L-chondrite breakup cooled Earth and triggered Ordovician icehouse conditions, sea level fall, and major faunal turnovers related to the Great Ordovician Biodiversification Event.
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| 30. |
- Schmitz, Birger, et al.
(författare)
-
Fragments of Late Eocene Earth-impacting asteroids linked to disturbance of asteroid belt
- 2015
-
Ingår i: Earth and Planetary Science Letters. - : Elsevier BV. - 1385-013X .- 0012-821X. ; 425, s. 77-83
-
Tidskriftsartikel (refereegranskat)abstract
- The onset of Earth's present icehouse climate in the Late Eocene coincides with astronomical events of enigmatic causation. At similar to 36 Ma ago the 90-100 km large Popigai and Chesapeake Bay impact structures formed within similar to 10-20 ka. Enrichments of He-3 in coeval sediments also indicate high fluxes of interplanetary dust to Earth for 2 Ma. Additionally, several medium-sized impact structures are known from the Late Eocene. Here we report from sediments in Italy the presence of abundant ordinary chondritic chromite grains (63-250 pm) associated with the ejecta from the Popigai impactor. The grains occur in the 40 cm interval immediately above the ejecta layer. Element analyses show that grains in the lower half of this interval have an apparent H-chondritic composition, whereas grains in the upper half are of L-chondritic origin. The grains most likely originate from the regoliths of the Popigai and the Chesapeake Bay impactors, respectively. These asteroids may have approached Earth at comparatively low speeds, and regolith was shed off from their surfaces after they passed the Roche limit. The regolith grains then settled on Earth some 100 to 1000 yrs after the respective impacts. Further neon and oxygen isotopic analyses of the grains can be used to test this hypothesis. If the Popigai and Chesapeake Bay impactors represent two different types of asteroids one can rule out previous explanations of the Late Eocene extraterrestrial signatures invoking an asteroid shower from a single parent-body breakup. Instead a multi-type asteroid shower may have been triggered by changes of planetary orbital elements. This could have happened due to chaos-related transitions in motions of the inner planets or through the interplay of chaos between the outer and inner planets. Asteroids in a region of the asteroid belt where many ordinary chondritic bodies reside, were rapidly perturbed into orbital resonances. This led to an increase in small to medium-sized collisional breakup events over a 2-5 Ma period. This would explain the simultaneous delivery of excess dust and asteroids to the inner solar system. Independent evidence for our scenario are the common cosmic-ray exposure ages in the range of ca. 33-40 Ma for recently fallen H and L chondrites. The temporal coincidence of gravity disturbances in the asteroid belt with the termination of ice-free conditions on Earth after 250 Ma is compelling. We speculate that this coincidence and a general correlation during the past 2 Ga between K-Ar breakup ages of parent bodies of the ordinary chondrites and ice ages on Earth suggest that there may exist an astronomical process that disturbs both regions of the inner asteroid belt and Earth's orbit with a potential impact on Earth's climate. (C) 2015 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license.
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| 31. |
- Schmitz, Birger, et al.
(författare)
-
Meteorite flux to Earth in the Early Cretaceous as reconstructed from sediment-dispersed extraterrestrial spinels
- 2017
-
Ingår i: Geology. - 0091-7613. ; 45:9, s. 807-810
-
Tidskriftsartikel (refereegranskat)abstract
- We show that Earth’s sedimentary strata can provide a record of the collisional evolution of the asteroid belt. From 1652 kg of pelagic Maiolica limestone of Berriasian–Hauterivian age from Italy, we recovered 108 extraterrestrial spinel grains (32–250 μm) representing relict minerals from coarse micrometeorites. Elemental and three oxygen isotope analyses were used to characterize the grains, providing a first-order estimate of the major types of asteroids delivering material at the time. Comparisons were made with meteorite-flux time “windows” in the Ordovician before and after the L-chondrite parent-body breakup. In the Early Cretaceous, ∼80% of the extraterrestrial spinels originated from ordinary chondrites. The ratios between the three groups of ordinary chondrites, H, L, LL, appear similar to the present, ∼1:1:0.2, but differ significantly from Ordovician ratios. We found no signs of a hypothesized Baptistina LL-chondrite breakup event. About 10% of the grains in the Maiolica originate from achondritic meteorite types that are very rare (<1%) on Earth today, but that were even more common in the Ordovician. Because most meteorite groups have lower spinel content than the ordinary chondrites, our data indicate that the latter did not dominate the flux during the Early Cretaceous to the same extent as today. Based on studies of three windows in deep time, we argue that there may have been a gradual long-term (a few hundred million years) turnover in the meteorite flux from dominance of achondrites in the early Phanerozoic to ordinary chondrites in the late Phanerozoic, interrupted by short-term (a few million years) meteorite cascades from single asteroid breakup events.
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| 32. |
- Schmitz, Birger, et al.
(författare)
-
The breakup of the L-chondrite parent body 466 Ma and its terrestrial effects-a search for a mid-Ordovician biodiversity event
- 2023
-
Ingår i: Estonian Journal of Earth Sciences. - 1736-4728. ; 72:1, s. 94-97
-
Tidskriftsartikel (refereegranskat)abstract
- About a third of all meteorites that fall on Earth today, the stony L-chondrites, originate from a major breakup event in the asteroid belt 466 Ma, in the early Darriwilian. This is the largest asteroid breakup in the past three billion years documented by K-Ar gas-retention ages of recently fallen meteorites. There has been a debate whether the breakup had any effects on Earth’s biota. Based mainly on brachiopod data from western Russia, some authors have argued for the existence of a major biodiversity ‘event’ at approximately the time of the L-chondrite breakup. An analysis of the distribution of three fossil groups (conodonts, ostracods and trilobites) across the late Dapingian and early Darriwilian in three sections in southern Sweden shows no evidence of any biodiversity event. The only biotic changes outside a normal trend are those related to a sea-level fall following the arrival of large amounts of dust from the asteroid breakup. We conclude that the Great Ordovician Biodiversification Event represents a sequence of changes over about 20 Myr, coinciding with an asteroid shower from the breakup of the L-chondrite parent body.
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| 33. |
- Schmitz, Birger, et al.
(författare)
-
The micrometeorite flux to Earth during the Frasnian–Famennian transition reconstructed in the Coumiac GSSP section, France
- 2019
-
Ingår i: Earth and Planetary Science Letters. - : Elsevier BV. - 0012-821X. ; 522, s. 234-243
-
Tidskriftsartikel (refereegranskat)abstract
- We have reconstructed the distribution of extraterrestrial chrome spinels in a marine limestone section across the Frasnian–Famennian stratotype section at Coumiac in southern France, providing the first insights on the types of micrometeorites and meteorites that fell on Earth at this time. The data can test whether the small cluster of roughly coeval, large impact structures is related to an asteroid breakup and shower with possible bearings also on the late Devonian biodiversity crisis. A total of ∼180 extraterrestrial spinel grains (>32 μm) were recovered from 957 kg of rock. Noble-gas measurements of individual grains show high solar-wind content, implying an origin from decomposed micrometeorites. Element analyses indicate a marked dominance of ordinary chondritic over achondritic grains, similar to the recent flux. The relation between H, L and LL meteorites is ∼29–58–13%, similar to the late Silurian flux, ∼31–63–6%, but different from the distribution, ∼45–45–10%, in the recent and the Cretaceous flux. Our data show no indication of a generally enhanced late Devonian micrometeorite flux that would accompany an asteroid shower. However, in a single limestone bed that formed immediately before the Upper Kellwasser horizon, that represents the main end-Frasnian species-turnover event, we found an enrichment of ∼10 ordinary chondritic grains (>63 μm) per 100 kg of rock, compared to the ∼1–3 grains per 100 kg that characterise background. The anomalously abundant grains are of mixed H, L and LL types and may be related to an enhanced flux of extraterrestrial dust during postulated minima in both the 405 ka and 2.4 Ma Earth-orbit eccentricity cycles at the onset of the Upper Kellwasser event. In the present solar system the dust accretion at Earth is the highest at eccentricity minima because of the spatial distribution of dust bands of the zodiacal cloud. Besides this small grain anomaly the data here and in previous studies support a stable meteorite flux through the late Silurian and Devonian, in contrast to the mid-Ordovician, when achondritic meteorites that are rare on Earth today were common, followed by the influx of a flood of debris related to the breakup of the L-chondrite parent body. Our accumulated data for six time windows through the Phanerozoic indicate that the ordinary chondrites make up a major fraction in the meteorite flux since at least the mid-Ordovician. We note that the sources in the asteroid belt of the H and L meteorites, the two most common types of meteorites today and through much of the Phanerozoic, remain elusive.
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| 34. |
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| 35. |
- Terfelt, Fredrik, et al.
(författare)
-
Asteroid break-ups and meteorite delivery to Earth the past 500 million years
- 2021
-
Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424. ; 118:24
-
Tidskriftsartikel (refereegranskat)abstract
- The meteoritic material falling on Earth is believed to derive from large break-up or cratering events in the asteroid belt. The flux of extraterrestrial material would then vary in accordance with the timing of such asteroid family-forming events. In order to validate this, we investigated marine sediments representing 15 time-windows in the Phanerozoic for content of micrometeoritic relict chrome-spinel grains (>32 μm). We compare these data with the timing of the 15 largest break-up events involving chrome-spinel–bearing asteroids (S- and V-types). Unexpectedly, our Phanerozoic time windows show a stable flux dominated by ordinary chondrites similar to today’s flux. Only in the mid-Ordovician, in connection with the breakup of the L-chondrite parent body, do we observe an anomalous micrometeorite regime with a two to three orders-of-magnitude increase in the flux of L-chondritic chrome-spinel grains to Earth. This corresponds to a one order-of-magnitude excess in the number of impact craters in the mid-Ordovician following the L-chondrite break-up, the only resolvable peak in Phanerozoic cratering rates indicative of an asteroid shower. We argue that meteorites and small (<1-km-sized) asteroids impacting Earth mainly sample a very small region of orbital space in the asteroid belt. This selectiveness has been remarkably stable over the past 500 Ma.
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| 36. |
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| 37. |
- Terfelt, Fredrik, et al.
(författare)
-
Complete record of Furongian polymerid trilobites and agnostoids of Scandinavia : a biostratigraphical scheme
- 2011
-
Ingår i: Lethaia. - : Scandinavian University Press / Universitetsforlaget AS. - 0024-1164. ; 44:1, s. 8-14
-
Tidskriftsartikel (refereegranskat)abstract
- So far, 112 polymerid trilobite species/subspecies and 13 agnostoid species/subspecies have been recorded from the Furongian (upper Cambrian) of Scandinavia. For the first time, their zonal occurrences are summarized in a biostratigraphical scheme serving as a practical synopsis for students of this interval in time. Ninety-six of the recorded polymerid trilobite species/subspecies belong to the family Olenidae whereas the remaining 16 are distributed across eight other families. Levels of increased speciation and low diversity (including stratigraphical range gaps) are conspicuous and these may be correlated with recorded physical and chemical anomalies.
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| 38. |
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| 39. |
- Terfelt, Fredrik, et al.
(författare)
-
Furongian (upper Cambrian) biostratigraphy and trilobites of the Haslov-1 drill core, Scania, S. Sweden
- 2005
-
Ingår i: GFF. - 2000-0863. ; 127, s. 195-203
-
Tidskriftsartikel (refereegranskat)abstract
- A drilling made in 1972 at Haslov, Scania, southern Sweden, penetrated a 2572 m thick succession of Phanerozoic strata. The only cored parts of the succession derive from the Upper Ordovician and the Furongian (upper Cambrian) series. Merely the uppermost part of the Furongian was recovered, comprising eight metres of Alum Shale with limestone concretions. Nine species and subspecies of trilobites are identified and their succession is used for subdividing the core into the Peltura scarabaeoides Zone, comprising the Parabolina lobata and the Peltura paradoxa subzones, and the Acerocare Zone, comprising the Peltura transiens Subzone. The conodont Cordylodus proavus? was found in the uppermost part of the core. The faunal succession is interrupted by conspicuous unfossiliferous intervals; the most extensive one measuring 3.39 m. Approximately coeval barren intervals have been recorded from other localities in Scania. Although the ecological significance of these intervals remains to be evaluated, it can be concluded that they are a regional feature in the Furongian of Scania.
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| 40. |
- Terfelt, Fredrik, et al.
(författare)
-
Macropyge (Promacropyge) Scandinavica new species; The first macropyginid trilobite recorded from the Furongian of Baltica
- 2007
-
Ingår i: Journal of Paleontology. - 0022-3360. ; 81:6, s. 1516-1522
-
Tidskriftsartikel (refereegranskat)abstract
- Macropyge (Promacropyge) scandinavica new species is described from the Furongian Peltura minor Zone on northwestern Mount 14 Kinnekulle, southcentral Sweden. It represents the first macropyginid trilobite recorded in Baltica. M. (P.) scandinavica closely resembles other species of the same subgenus from southeast China, suggesting a correlation between the Scandinavian P. minor Zone and the Lotagnostus americanus-Hedinaspis regalis Zone of China. The specimens are preserved in two limestone lithologies, interpreted as representing alternating 14 normal and storm deposits, supporting the idea of an intrabasinal paleohigh in Vastergotland, southcentral Sweden.
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| 41. |
- Terfelt, Fredrik, et al.
(författare)
-
Pseudagnostus rugosus Ergaliev, 1980: a key agnostoid species for intercontinental correlation of upper Furongian (Cambrian) strata
- 2010
-
Ingår i: Geological Magazine. - 0016-7568. ; 147:5, s. 789-796
-
Tidskriftsartikel (refereegranskat)abstract
- Pseudagnostus rugosus Ergaliev, 1980 is described from the Furongian Ctenopyge tumida Zone at Gislovshammar, Scania, southern Sweden. This is the first record of this distinctive agnostoid in Scandinavia. The species is known previously from Malyi Karatau, Kazakhstan, and northwestern Hunan and western Zhejiang, South China, and provides a newly recognized link between middle-upper Furongian successions in Baltica, Kazakhstan and South China. The occurrences of P. rugosus allow a correlation between the C. tumida Zone of Baltica, the lower Eolotagnostus scrobicularis-Jegorovaia Zone of Kazakhstan and the lower Lotagnostus americanus Zone of South China.
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| 42. |
- Terfelt, Fredrik, et al.
(författare)
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Re-evaluation of the conodont Iapetognathus and implications for the base of the Ordovician System GSSP
- 2011
-
Ingår i: Lethaia. - : Scandinavian University Press / Universitetsforlaget AS. - 0024-1164. ; 45:2, s. 227-237
-
Tidskriftsartikel (refereegranskat)abstract
- In 2000, the International Union of Geological Sciences (IUGS) ratified the decision from the International Working Group on the Cambrian–Ordovician Boundary (COBWG) to place the Global boundary Stratotype Section and Point (GSSP) for the base of the Ordovician System in the Green Point section, Newfoundland, Canada, at a point coinciding with the first appearance of the conodont Iapetognathus fluctivagus. However, a restudy of the conodont successions from Green Point shows that this species is not present at the boundary interval, and as a consequence the section does not fulfil the biostratigraphical requirements of a GSSP. The GSSP horizon as now defined is based on a level part-way through the range of I. preaengensis – a species with lower first appearance datum (FAD). The true FAD of I. fluctivagus is above the FAD of planktonic graptolites and well above the FAD of I. preaengensis. As a consequence of these problems, a restudy of the GSSP section and the other sections in the Cow Head Group is necessary. A redefinition of the GSSP horizon is suggested. The following four alternative horizons have potential as new horizons for the GSSP level: the FAD of Cordylodus intermedius; the FAD of Cordylodus andresi; the FAD of Eoconodontus notchpeakensis; and the FAD of the agnostoid Lotagnostus americanus.
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| 43. |
- Terfelt, Fredrik
(författare)
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Review of uppermost Furongian trilobites from Scania, Southern Sweden, based on type material
- 2006
-
Ingår i: Palaeontology. - : Wiley. - 1475-4983 .- 0031-0239. ; 49:6, s. 1339-1355
-
Forskningsöversikt (refereegranskat)abstract
- The Scandinavian trilobites described in the classical papers by Moberg and Moller (1898) and Moberg (1898) are reviewed, based on the original type collections. The ten species and subspecies originally described are here considered to represent 12 species and subspecies, ranging in age from the latest Furongian (late Cambrian) through the Tremadocian (Early Ordovician). Lectotypes are selected for Parabolina (Parabolina) acanthura (Angelin), Acerocare ecorne Angelin and Westergaardia lata (Matthew). Leptoplastus claudicans (Moberg and Moller) is regarded as a junior subjective synonym of L. stenotus Angelin. These, and lectotypes formerly only figured by hand-drawings, are illustrated by high-resolution photographs.
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| 44. |
- Terfelt, Fredrik, et al.
(författare)
-
The Cambrian–Ordovician transition in dysoxic facies in Baltica— diverse faunas and carbon isotope anomalies
- 2014
-
Ingår i: Palaeogeography, Palaeoclimatology, Palaeoecology. - : Elsevier BV. - 1872-616X .- 0031-0182. ; 394, s. 59-73
-
Tidskriftsartikel (refereegranskat)abstract
- The Cambrian–Ordovician boundary interval in Scandinavia is characterized by largely endemic trilobite species and fossil-meager intervals within the Alum Shale Formation. Previous investigations of this interval in Scandinavia, based on drill cores, are rather sketchy. In order to characterize the faunal signature in a largely dysoxic setting during this time interval, as well as providing biostratigraphic and chemostratigraphic data valuable for intercontinental correlation, a small strip in the outskirts of the village Södra Sandby in Scania, southern Sweden, was excavated. Nearly 5 m of the Cambrian–Ordovician boundary strata, largely represented by alum shale, were exposed and the profile was meticulously investigated for fossil content and lithological characteristics and sampled for δ13Corg analyses. The uppermost Cambrian in Sweden has previously been described as barren of fossils; however, the present study reveals a rather diverse fauna, including lingulid brachiopods, trilobites, protoconodonts, paraconodonts and euconodonts in the uppermost 1.6 m of the Furongian. The first appearance datum of planktic graptolites is represented by a single shale surface covered by specimens of Rhabdinopora flabelliforme parabola at 1.74 m above the base of the section and roughly corresponds to the Cambrian–Ordovician boundary. The conodont fauna includes several cordylodids important for intercontinental correlation. The Södra Sandby section δ13Corg data were coupled with isotope data from two Scanian drill cores, Håslöv-1 and Tosterup-2, in order to compile a composite isotope curve spanning the uppermost Ctenopyge linnarssoni Trilobite Zone in the Furongian to the upper R. flabelliforme parabola Graptolite Zone in the Lower Ordovician (Lower Tremadocian). Two isotope shifts from baseline values, observed at the base of the Peltura paradoxa Trilobite Zone and the lower part of the Peltura transiens Trilobite Zone, respectively, can be correlated with contemporaneous shifts in other parts of the world. The former, a negative shift of approximately 0.4–0.7‰, corresponds to the widely documented Top of Cambrian carbon isotope Excursion (TOCE) and the latter, a positive shift of approximately 1‰, corresponds to an as-yet-unnamed excursion at the base of the Cordylodus proavus Conodont Zone. In terms of faunal content and isotopic signals, the present study represents the first detailed description of the Cambrian–Ordovician boundary interval in Baltica. The relatively diverse fauna recorded suggests that the dysoxic environment was not a serious inhibitor for marine life. Globally, no isotope values significantly different from background values have been reported at the Cambrian–Ordovician boundary. This is confirmed by the present study; however, as the base of the Ordovician GSSP lacks meaningful isotope data, global correlation of this important boundary is problematic.
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| 45. |
- Terfelt, Fredrik, et al.
(författare)
-
The first Remopleuridioidean trilobite and the earliest Parabolinella species recorded in the Furongian of Scandinavia
- 2009
-
Ingår i: Journal of Paleontology. - : Cambridge University Press (CUP). - 0022-3360 .- 1937-2337. ; 83:2, s. 299-306
-
Tidskriftsartikel (refereegranskat)abstract
- The furongian of Mount Kinnekulle, Västergötland, Sweden (Fig. 1) is exposed in a number of road cuts, stream cuts, and abandoned alum shale quarries scattered around the mountain (e.g., Westergård, 1922, fig. 18; Müller and Hinz, 1991, fig. 2). Stratigraphically, the exposed successions span the Olenus gibbosus Zone through the Peltura paradoxa Zone (Fig. 2), and they have a maximum thickness of ca 12 m (Westergård, 1943). The strata consist of interfingering layers of alum shale and bituminous limestone (colloquially referred to as “orsten”). Trilobites, predominantly olenids, occur frequently throughout the succession, although they are generally restricted to the limestones. During an investigation of trilobites in the Lotagnostus americanus Zone (Fig. 2) at two localities on Kinnekulle, the second author (JA) recovered two unusual trilobites. After a closer examination they could be assigned to Elkanaspis Ludvigsen, 1982 and Parabolinella Br⊘gger, 1882, both of which are extremely rare in the Furongian of Scandinavia.
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| 46. |
- Terfelt, Fredrik
(författare)
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Upper Cambrian trilobite biostratigraphy and taphonomy at Kakeled on Kinnekulle, Vastergotland, Sweden
- 2003
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Ingår i: Acta Palaeontologica Polonica. - 0567-7920. ; 48:3, s. 409-416
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Tidskriftsartikel (refereegranskat)abstract
- A section through the Upper Cambrian black shales and limestones at Kakeled on Kinnekulle, Vastergotland, Sweden, extends from the lower-middle part of the Agnostus pisiformis Zone into the Peltura scarabaeoides Zone. Fossils are usually preserved only in the stinkstones, but in the A. pisiformis Zone trilobites can be found also in the shales. Lithologically, the stinkstones can be subdivided into primary coquinoid limestone, which include the majority of the fossils, and early diagenetically formed limestone. The orientation of cephala and pygidia of A. pisiformis were measured on four shale surfaces and one stinkstone surface. The majority of the shields were deposited with the convex side up and showed a preferred orientation, suggesting that their positions were affected by currents. Above the A. pisiformis Zone the section comprises the Olenus/Homagnostus obesus Zone (0.30 m), the upper part of the Parabolina spinulosa Zone (0.05 m), the Peltura minor Zone (1.15 m), and the Peltura scarabaeoides Zone (2.50 m). The Leptoplastus and Protopeltura praecursor zones are missing. The Olenus/H. obesus Zone is represented only by the O. gibbosus and O. wahlenbergi subzones, whereas the O. truncatus, O. attenuatus, O. dentatus, and O. scanicus subzones are missing.
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- Terfelt, Fredrik
(författare)
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Upper middle Cambrian through Furongian of Scandinavia with focus on trilobites, paleoenvironments and correlations
- 2006
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis is based on studies of upper middle Cambrian through Furongian strata in Scandinavia with focus on trilobite biostratigraphy, taxonomy, paleoecology, and intercontinental correlation. The material studied derives mainly from Västergötland and Scania, southern Sweden. Three new trilobite species are described: Macropyge (Promacropyge) scandinavica, Elkanaspis kinnekullensis, and Parabolinella sandtorpensis. The former two proved important for correlations with China and North America, respectively, whereas the latter is important for our understanding of the systematic position of the genus Parabolinella. All these species were recovered from Mount Kinnekulle, Västergötland, Sweden. The strata studied at Kinnekulle show features here interpreted as indicative of an intrabasinal paleohigh, including current-oriented fossils, the presence of thin sand wedges, the large proportion of limestone, different limestone lithologies, and gaps in the succession. This is in contrast to the biostratigraphically complete, upper middle Cambrian through Furongian successions in Scania, where the strata are unaffected by water movements and reflect a deeper water setting on the outer shelf. The succession in Scania is, however, punctuated by five major fossil-barren intervals. The upper part of such an interval, in the uppermost middle Cambrian Agnostus pisiformis Zone, yielded phosphatocopines, protoconodont elements, and enigmatic trace fossils. Thus, these intervals, or at least parts of them, are, not necessarily barren of fossils, but of the normal, trilobite-dominated faunas. Moreover, the phosphatocopine-dominated and trilobite-dominated intervals represent two interdigitating biofacies of which the former, anomalous facies, correlates with a trilobite extinction event in North America and the onset of the globally recognizable Steptoean Positive Carbon Isotope Excursion (SPICE). The lowermost Furongian biozone in Scandinavia, the Olenus & A. (Homagnostus) obesus Zone, has here been replaced by two new zones; the globally recognized Glyptagnostus reticulatus Zone and the Olenus Zone. A drill core comprising middle Cambrian (Ptychagnostus atavus Zone) to Furongian (Parabolina spinulosa Zone) strata from Andrarum, Scania, southernmost Sweden, was sampled for ?13Corg-analysis. The resulting curve has a distinct positive ?13Corg excursion corresponding to the SPICE. This is the first time that the SPICE has been recorded in Baltica and from organic matter in an alum shale setting. A study from another drill core comprising upper Furongian strata recovered from c. 2500 m depth at Håslöv, in the southwesternmost tip of Scania, revealed a succession comparable to other sections and cores in Scania regarding biostratigraphy, lithology and the presence of major barren intervals. Moreover, from this drilling the conodont Cordylodus proavus Müller? was recovered from non-reworked sediments for the first time in Sweden. A review of 10 species and subspecies of upper Furongian trilobites originally described by Moberg and Möller (1898) and Moberg (1898), revealed that they, in fact, represent 12 species and subspecies. One species name was regarded as a junior subjective synonym, and lectotypes for three species were selected.
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