Ben Creisler
Some recent papers about paleoenvironments and extinction events:
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Landon Burgener, Ethan Hyland, Emily Griffith, Helena MitÃÅovÃ, Lindsay E. Zanno & Terry A. Gates (2021)
An extreme climate gradient-induced ecological regionalization in the Upper Cretaceous Western Interior Basin of North America.
GSA Bulletin (advance online publication)
DOI: https://doi.org/10.1130/B35904.1
https://pubs.geoscienceworld.org/gsa/gsabulletin/article-abstract/doi/10.1130/B35904.1/594464/An-extreme-climate-gradient-induced-ecological
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The Upper Cretaceous Western Interior Basin of North America provides a unique laboratory for constraining the effects of spatial climate patterns on the macroevolution and spatiotemporal distribution of biological communities across geologic timescales. Previous studies suggested that Western Interior Basin terrestrial ecosystems were divided into distinct southern and northern communities, and that this provincialism was maintained by a putative climate barrier at ~50ÂN paleolatitude; however, this climate barrier hypothesis has yet to be tested. We present mean annual temperature (MAT) spatial interpolations for the Western Interior Basin that confirm the presence of a distinct terrestrial climate barrier in the form of a MAT transition zone between 48ÂN and 58ÂN paleolatitude during the final 15 m.y. of the Cretaceous. This transition zone was characterized by steep latitudinal temperature gradients and divided the Western Interior Basin into warm southern and cool northern biomes. Similarity analyses of new compilations of fossil pollen and leaf records from the Western Interior Basin suggest that the biogeographical distribution of primary producers in the Western Interior Basin was heavily influenced by the presence of this temperature transition zone, which in turn may have impacted the distribution of the entire trophic system across western North America.
The Upper Cretaceous Western Interior Basin of North America provides a unique laboratory for constraining the effects of spatial climate patterns on the macroevolution and spatiotemporal distribution of biological communities across geologic timescales. Previous studies suggested that Western Interior Basin terrestrial ecosystems were divided into distinct southern and northern communities, and that this provincialism was maintained by a putative climate barrier at ~50ÂN paleolatitude; however, this climate barrier hypothesis has yet to be tested. We present mean annual temperature (MAT) spatial interpolations for the Western Interior Basin that confirm the presence of a distinct terrestrial climate barrier in the form of a MAT transition zone between 48ÂN and 58ÂN paleolatitude during the final 15 m.y. of the Cretaceous. This transition zone was characterized by steep latitudinal temperature gradients and divided the Western Interior Basin into warm southern and cool northern biomes. Similarity analyses of new compilations of fossil pollen and leaf records from the Western Interior Basin suggest that the biogeographical distribution of primary producers in the Western Interior Basin was heavily influenced by the presence of this temperature transition zone, which in turn may have impacted the distribution of the entire trophic system across western North America.
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Gregory J. Retallack (2021)
Multiple Permian-Triassic life crises on land and at sea.
Global and Planetary Change 198: 103415
https://doi.org/10.1016/j.gloplacha.2020.103415
https://www.sciencedirect.com/science/article/abs/pii/S0921818120303064
Highlights
Stable isotopes and Bk metrics of paleosols reveal Permian to Triassic events in South Africa.
Four Late Permian to Early Triassic CO2 spikes coincide with extinctions on land and at sea.
The Karoo Basin was mainly arid throughout this interval, but for four warm and humid spikes.
Extinctions on land were due to respiratory distress for vertebrates and roots of wetland plants.
Abstract
The largest mass extinction in the history of life was during the Late Permian, ca 252 Ma. New evidence from stable isotopic composition and Bk metrics of paleosols from the Late Permian to the Middle Triassic in the southern Karoo Basin of South Africa, reveal at least four atmospheric carbon dioxide spikes, coinciding with extinctions on land and at sea. The Karoo Basin was mainly arid throughout this interval, but the four life crises correlate with extreme greenhouse spikes of carbon dioxide and transient episodes of warmer and more humid climate, with respiratory distress for vertebrates and roots of wetland plants. These most extreme greenhouse crises in the history of life provide worst-case scenarios for modern global climate change.
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Multiple Permian-Triassic life crises on land and at sea.
Global and Planetary Change 198: 103415
https://doi.org/10.1016/j.gloplacha.2020.103415
https://www.sciencedirect.com/science/article/abs/pii/S0921818120303064
Highlights
Stable isotopes and Bk metrics of paleosols reveal Permian to Triassic events in South Africa.
Four Late Permian to Early Triassic CO2 spikes coincide with extinctions on land and at sea.
The Karoo Basin was mainly arid throughout this interval, but for four warm and humid spikes.
Extinctions on land were due to respiratory distress for vertebrates and roots of wetland plants.
Abstract
The largest mass extinction in the history of life was during the Late Permian, ca 252 Ma. New evidence from stable isotopic composition and Bk metrics of paleosols from the Late Permian to the Middle Triassic in the southern Karoo Basin of South Africa, reveal at least four atmospheric carbon dioxide spikes, coinciding with extinctions on land and at sea. The Karoo Basin was mainly arid throughout this interval, but the four life crises correlate with extreme greenhouse spikes of carbon dioxide and transient episodes of warmer and more humid climate, with respiratory distress for vertebrates and roots of wetland plants. These most extreme greenhouse crises in the history of life provide worst-case scenarios for modern global climate change.
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Samuel L. Goldberg, Theodore M. Present, Seth Finnegan, and Kristin D. Bergmann (2021)
A high-resolution record of early Paleozoic climate.
Proceedings of the National Academy of Sciences 118 (6): e2013083118
doi: https://doi.org/10.1073/pnas.2013083118
https://www.pnas.org/content/118/6/e2013083118
Significance
The Cambrian-Ordovician (541 million to 443 million y ago) climate record is poorly constrained due to the sparsity of carbonate fossils typically used for temperature reconstructions. We demonstrate that the abundant carbonate sediments from this time can preserve isotopic compositions and trends similar to those of fossil material and combine sediment records into a high-resolution proxy record of Late Cambrian and Ordovician climate. Examination of this record in the context of evolutionary and tectonic changes demonstrates that Earthâs climate was tightly coupled to tectonic and volcanic activity and played a strong role in biodiversity trends during the time of early animal evolution.
Abstract
The spatial coverage and temporal resolution of the Early Paleozoic paleoclimate record are limited, primarily due to the paucity of well-preserved skeletal material commonly used for oxygen-isotope paleothermometry. Bulk-rock Î18O datasets can provide broader coverage and higher resolution, but are prone to burial alteration. We assess the diagenetic character of two thick Cambro-Ordovician carbonate platforms with minimal to moderate burial by pairing clumped and bulk isotope analyses of micritic carbonates. Despite resetting of the clumped-isotope thermometer at both sites, our samples indicate relatively little change to their bulk Î18O due to low fluid exchange. Consequently, both sequences preserve temporal trends in Î18O. Motivated by this result, we compile a global suite of bulk rock Î18O data, stacking overlapping regional records to minimize diagenetic influences on overall trends. We find good agreement of bulk rock Î18O with brachiopod and conodont Î18O trends through time. Given evidence that the Î18O value of seawater has not evolved substantially through the Phanerozoic, we interpret this record as primarily reflecting changes in tropical, nearshore seawater temperatures and only moderately modified by diagenesis. Focusing on the samples with the most enriched, and thus likely least-altered, Î18O values, we reconstruct Late Cambrian warming, Early Ordovician extreme warmth, and cooling around the Early-Middle Ordovician boundary. Our record is consistent with models linking the Great Ordovician Biodiversification Event to cooling of previously very warm tropical oceans. In addition, our high-temporal-resolution record suggests previously unresolved transient warming and climate instability potentially associated with Late Ordovician tectonic events.
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R. B. Firestone (2021)
The correlation between impact crater ages and chronostratigraphic boundary dates.
Monthly Notices of the Royal Astronomical Society 501(3): 3350â3363
doi: https://doi.org/10.1093/mnras/staa3790
https://academic.oup.com/mnras/article-abstract/501/3/3350/6041705
The correlation between impact crater ages and chronostratigraphic boundary dates.
Monthly Notices of the Royal Astronomical Society 501(3): 3350â3363
doi: https://doi.org/10.1093/mnras/staa3790
https://academic.oup.com/mnras/article-abstract/501/3/3350/6041705
The accurately measured ages of 89 large impact craters and layers were compared with the boundary dates for periods, epochs, and ages of the geological time-scale by a weighted least-squares fit. They are highly correlated with a Ï2/f = 0.63. A Monte Carlo simulation of randomly chosen crater ages gives a >99.8 percent probability that this result is not random. No craters are found in the oceans or, until recently, in ice which collectively cover 80 percent of Earthâs surface indicating that far more impacts have occurred than are known. Multiple impacts cluster near the times of boundary dates so, based on the observed cluster sizes assuming a binomial distribution, it was determined that the average cluster multiplicity is five. Comparison of the impact ages with the dates of the great extinctions revealed a strong correlation with Ï2/f = 0.36 and a multiplicity of 8â9 impacts. It is shown that volcanism, although correlated with boundary dates, is a continuous process unrelated to sudden extinctions. During the past 125 Ma, the rate of global change and the impact rate have increased dramatically as the Earth passes near the OB star association. Multiple impacts 12.9 ka ago ended the Pleistocene epoch at the onset of the Younger Dryas (YD) causing worldwide extinctions. The date and extent of the YD impact may be consistent with a 62 Ma cycle of major impact events. During the Holocene 20 crater, airburst and impact tsunami chevron ages correspond to dates of global cooling with a Ï2/f = 0.75 and >99 percent probability. Future impacts could reverse global warming or even induce next ice age.
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Mingming Ma, Mei He ÂMengting Zhao, Chao Peng & Xiuming Liu (2021)
Evolution of atmospheric circulation across the Cretaceous-Paleogene (KâPg) boundary interval in low-latitude East Asia.
Global and Planetary Change (advance online publication)
https://doi.org/10.1016/j.gloplacha.2021.103435
https://www.sciencedirect.com/science/article/abs/pii/S0921818121000205
Highlights
Evolution of atmospheric circulation across the Cretaceous-Paleogene (KâPg) boundary interval in low-latitude East Asia.
Global and Planetary Change (advance online publication)
https://doi.org/10.1016/j.gloplacha.2021.103435
https://www.sciencedirect.com/science/article/abs/pii/S0921818121000205
Highlights
A new terrestrial record spanning the K-Pg in low-latitude East Asia has been obtained.
Monsoon circulation could reach the studied area during the Danian "greenhouse" period.
While it was beyond the control of the monsoon circulation during the Maastrichtian "cold greenhouse" period.
Abstract
The Cretaceous-Paleogene (K-Pg) boundary interval is an important time interval for deep-time paleoclimatic research, and most records of this interval are derived from marine sections. In this study, we conduct high-resolution magnetic and geochemical analyses in a terrestrial sedimentary succession from the Nanxiong Basin (Southeast China). We combine this data with previous work to compare these results with global marine and other terrestrial records. We find that the magnetic and geochemical parameters record a sequence of global climatic changes across the K-Pg boundary interval. Moreover, during the Maastrichtian cold "greenhouse" time interval, the climate changes in the studied area are consistent with the benthic foraminiferal Î18O record from the North Atlantic, and we observe no correlation between the Î13Ccarb and Î18Ocarb; in contrast, during the Danian "greenhouse" time interval, the climate changes in the studied area are consistent with the benthic foraminiferal Î18O records from both the Pacific and the North Atlantic, and we observe a positive correlation between Î13Ccarb and Î18Ocarb. We suggest that the observed changes are likely linked to the transformation of atmospheric circulation in low-latitude East Asia. These new insights have implications for "global monsoon" research and understanding the causes of the mass extinction
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Electromagnetic effects of K-Pg impact helped kill the dinosaurs...
Z.K. Silagadze (2021)
Asteroid impact, Schumann resonances and the end of dinosaurs.
Physics Letters A 127156
doi: https://doi.org/10.1016/j.physleta.2021.127156
https://www.sciencedirect.com/science/article/abs/pii/S0375960121000207
Highlights
Expected magnitudes of the Schumann resonances after the Chicxulub impact are estimated.
Biological effects of ELF electromagnetic fields are reviewed.
Excitation and distortion of the Schumann resonances are considered as a stressor contributing to the dinosaur demise.
Abstract
It is believed that an asteroid/comet impact 65 million years ago ended the dinosaur era. The researchers named the corresponding impact crater Chicxulub, the Mayan word roughly translated as "the dragon's tail." We estimate the expected magnitudes of the Schumann resonance fields immediately after the Chicxulub impact and show that they exceed their present-day values by about Âtimes. Long-term distortion of the Schumann resonance parameters is also expected due to the environmental impact of the Chicxulub event. If Schumann resonances play a regulatory biological role, as some studies indicate, it is possible that the excitation and distortion of Schumann resonances after the asteroid/comet impact was a possible stress factor, which, among other stress factors associated with the impact, contributed to the demise of dinosaurs.