End-Cretaceous marine extinction patterns + mercury peaks from Deccan volcanism and Chicxulub impact + more
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Ben Creisler
May 27, 2026, 2:00:17 PM (10 days ago) May 27
to DinosaurMa...@googlegroups.com
Ben Creisler
Recent or not yet mentioned K-Pg extinction papers:
The Chicxulub asteroid impact at the Cretaceous–Paleogene (K–Pg) boundary (66 Ma) is thought to have caused the extinction of around 75% of species in the fossil record by triggering catastrophic environmental changes. However, despite decades of research, the mechanisms linking the environmental changes to the selective extinction patterns observed in the marine fossil record remain unresolved. Here we use a global trait-based ecosystem model to establish this causality for the marine plankton community beyond the fossilized groups. Our model simulates diversity dynamics during the initial 100 years after the K–Pg boundary and represents explicitly extinction based on biomass thresholds that scales with body size. Under K–Pg climatic forcings, the model reproduces successfully key observed extinction patterns, including the high vulnerability of planktic foraminifera and other zooplankton, the survival of small mixotrophs4 and phytoplankton, and potential for reduced diversity loss in high-latitude settings. Our analysis suggests that impact-driven darkness and body-size-dependent extinction thresholds drove most of the observed extinction patterns. These results suggest that plankton ecologies enhance survival through differences in energy demand and acquisition. Our study bridges the gap between fossil evidence of extinction patterns and the K–Pg impact winter hypothesis, highlighting the value of trait-based models for understanding past biodiversity crises.
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Penny Barton, Gail Christeson, Sean Gulick, Joanna Morgan, Mario Rebolledo-Vieyra, Jaime Urrutia-Fucugauchi & Michael Warner (2026)
Seismic travel-time tomography under the peak ring of the Chicxulub impact crater
Geophysical Journal International, ggag152
doi: https://doi.org/10.1093/gji/ggag152
https://academic.oup.com/gji/advance-article/doi/10.1093/gji/ggag152/8661864
We present the results of a three-dimensional seismic tomography study of the upper crust beneath a quadrant of the peak ring structure of the Chicxulub meteorite impact crater, Mexico. Reflection and refraction travel-times from a grid of seismic profiles recorded by a 6 km streamer and 48 ocean bottom seismometer stations were inverted to give a well-resolved three-dimensional velocity model to a maximum depth of 6-8 km. The model comprised the thin water layer, a layer of low seismic velocity post-impact sedimentary infill, and the crater basement, which was separated from the fill by the interface representing the top of the crater, defined by normal incidence reflection picks. The crater basement shows a cylinder-shaped feature extending vertically downwards beneath the topographic peak ring to at least 8 km, the depth of resolution of this survey, characterised by slower seismic velocities than in the surrounding rocks at the same depth. This result supports and extends the observations of previous seismic refraction work in the peak ring, and also of scientific drilling, that the material in the peak ring has significantly reduced seismic velocity compared to typical granitic basement lithologies. We used the velocity model to perform a pre-stack depth migration of a key seismic reflection profile. In the best-fitting model presented here the prominent dipping reflector previously identified on seismic reflection profiles, which projects to the outer edge of the peak ring, dips inwards and crosses the low velocity cylinder without an apparent first order contrast in impedance. This result implies that the reflectivity of this dipping reflector is due to a thin, high-contrast layer such as entrapped impact melt or hydrothermal alteration within the overturned structures. We also identify well-imaged slump blocks from the crater rim/inner ring inwards, variations in the height and width of the peak ring, and associated variations in the velocity contrast that characterises the anomaly beneath the peak ring.
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Free pdf:
Rui Ying, Fanny M. Monteiro, James D. Witts & Daniela N. Schmidt (2026)
Darkness and body size shaped end-Cretaceous marine extinction patterns
Nature (advance online publication)
doi: https://doi.org/10.1038/s41586-026-10541-4
https://www.nature.com/articles/s41586-026-10541-4
Rui Ying, Fanny M. Monteiro, James D. Witts & Daniela N. Schmidt (2026)
Darkness and body size shaped end-Cretaceous marine extinction patterns
Nature (advance online publication)
doi: https://doi.org/10.1038/s41586-026-10541-4
https://www.nature.com/articles/s41586-026-10541-4
The Chicxulub asteroid impact at the Cretaceous–Paleogene (K–Pg) boundary (66 Ma) is thought to have caused the extinction of around 75% of species in the fossil record by triggering catastrophic environmental changes. However, despite decades of research, the mechanisms linking the environmental changes to the selective extinction patterns observed in the marine fossil record remain unresolved. Here we use a global trait-based ecosystem model to establish this causality for the marine plankton community beyond the fossilized groups. Our model simulates diversity dynamics during the initial 100 years after the K–Pg boundary and represents explicitly extinction based on biomass thresholds that scales with body size. Under K–Pg climatic forcings, the model reproduces successfully key observed extinction patterns, including the high vulnerability of planktic foraminifera and other zooplankton, the survival of small mixotrophs4 and phytoplankton, and potential for reduced diversity loss in high-latitude settings. Our analysis suggests that impact-driven darkness and body-size-dependent extinction thresholds drove most of the observed extinction patterns. These results suggest that plankton ecologies enhance survival through differences in energy demand and acquisition. Our study bridges the gap between fossil evidence of extinction patterns and the K–Pg impact winter hypothesis, highlighting the value of trait-based models for understanding past biodiversity crises.
=====
Kunio Kaiho, Jeroen E. Sonke, Stephen E. Grasby, Akane Yamakawa, Satoshi Takahashi & Laure Laffont (2026)
Dual Hg peaks and isotopic convergence reveal sequential Deccan volcanism and Chicxulub impact at the K–Pg boundary
Palaeogeography, Palaeoclimatology, Palaeoecology 695: 113831
doi: https://doi.org/10.1016/j.palaeo.2026.113831
https://www.sciencedirect.com/science/article/abs/pii/S0031018226002944
Highlights
Two Hg peaks identified across the K–Pg boundary at proximal and distal sites.
First Hg peak indicates Deccan volcanism (low Ir, moderate coronene)
Second Hg peak reflects Chicxulub impact (high Ir, coronene; R = 0.97)
Hg isotopes converge, indicating mixed volcanic and hydrocarbon sources.
Impact-driven Hg release coincides with plankton extinction horizon.
Abstract
Iridium (Ir) and mercury (Hg) enrichments at the Cretaceous–Paleogene (K–Pg) boundary are widely attributed to the Chicxulub impact and Deccan Traps volcanism, although their relative contributions remain debated. We present high-resolution analyses of Hg, Ir, coronene, and Hg isotopes from marine sediments in Haiti and Spain, representing proximal and distal settings relative to the impact site. Elevated Hg/TOC ratios at both sites indicate substantial atmospheric Hg input immediately before and after the impact. At the proximal site, impact-related turbidites are overlain by marl containing an Hg–Ir-enriched orange layer. Two Hg peaks are identified: one preceding the turbidites and another within the orange layer. The first peak shows low Ir and moderate coronene values, indicating a volcanic origin linked to Deccan Traps activity. The second peak is characterized by strongly correlated Hg and Ir concentrations (R = 0.97) and high coronene values, consistent with an impact origin. Similar patterns at the distal site support the global extent of these events. Hg isotope compositions (δ202Hg and Δ199Hg) converge during peak intervals, indicating mixing among volcanic, crustal, and hydrocarbon-derived sources. Mass balance calculations show that Hg enrichment in the Ir-rich layer can be explained by release from hydrocarbon-bearing impact target rocks. The second peak coincides with the extinction of Cretaceous planktonic foraminifera, suggesting the Chicxulub impact as the primary driver, with a possible contribution from volcanism. These results underscore the importance of integrating multiple geochemical proxies to resolve the complex interplay of volcanic and impact-related processes in Earth's history.
Dual Hg peaks and isotopic convergence reveal sequential Deccan volcanism and Chicxulub impact at the K–Pg boundary
Palaeogeography, Palaeoclimatology, Palaeoecology 695: 113831
doi: https://doi.org/10.1016/j.palaeo.2026.113831
https://www.sciencedirect.com/science/article/abs/pii/S0031018226002944
Highlights
Two Hg peaks identified across the K–Pg boundary at proximal and distal sites.
First Hg peak indicates Deccan volcanism (low Ir, moderate coronene)
Second Hg peak reflects Chicxulub impact (high Ir, coronene; R = 0.97)
Hg isotopes converge, indicating mixed volcanic and hydrocarbon sources.
Impact-driven Hg release coincides with plankton extinction horizon.
Abstract
Iridium (Ir) and mercury (Hg) enrichments at the Cretaceous–Paleogene (K–Pg) boundary are widely attributed to the Chicxulub impact and Deccan Traps volcanism, although their relative contributions remain debated. We present high-resolution analyses of Hg, Ir, coronene, and Hg isotopes from marine sediments in Haiti and Spain, representing proximal and distal settings relative to the impact site. Elevated Hg/TOC ratios at both sites indicate substantial atmospheric Hg input immediately before and after the impact. At the proximal site, impact-related turbidites are overlain by marl containing an Hg–Ir-enriched orange layer. Two Hg peaks are identified: one preceding the turbidites and another within the orange layer. The first peak shows low Ir and moderate coronene values, indicating a volcanic origin linked to Deccan Traps activity. The second peak is characterized by strongly correlated Hg and Ir concentrations (R = 0.97) and high coronene values, consistent with an impact origin. Similar patterns at the distal site support the global extent of these events. Hg isotope compositions (δ202Hg and Δ199Hg) converge during peak intervals, indicating mixing among volcanic, crustal, and hydrocarbon-derived sources. Mass balance calculations show that Hg enrichment in the Ir-rich layer can be explained by release from hydrocarbon-bearing impact target rocks. The second peak coincides with the extinction of Cretaceous planktonic foraminifera, suggesting the Chicxulub impact as the primary driver, with a possible contribution from volcanism. These results underscore the importance of integrating multiple geochemical proxies to resolve the complex interplay of volcanic and impact-related processes in Earth's history.
====
Free pdf:
Roberto Bartali, Jaime Urrutia-Fucugauchi, Jose Ramon Torres-Hernandez, Ligia Perez-Cruz & Rosa Lina Tovar-Tovar (2026)
Unraveling the Cretaceous-Paleogene boundary event across the Gulf of Mexico—High-resolution Rayon reef section, Valles-San Luis Potosi platform, Mexico
PLOS ONE 21(4): e0345692
doi: https://doi.org/10.1371/journal.pone.0345692
https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0345692
The Cretaceous/Paleogene boundary, marked by the Chicxulub impact ejecta layer has a global distribution, with distal, intermediate and proximal boundary sections of distinct mineralogy, geochemistry and stratigraphy. Distal sections show a thin double-layer of spherulites and clay, enriched in platinum group elements and impact minerals. Proximal boundary sections around the Gulf of Mexico-Caribbean Sea are thicker, with clastic tsunami and debris flow deposits and the fireball layer in between the spherulitic and clay layers. Impact-induced disturbance and stratigraphic gaps have limited the resolution in unveiling the event sequence. Here we present a study on a recently discovered reef section in a carbonate platform, ~ 1,050 km away across the Gulf of Mexico. The boundary is marked by a black clay with shock quartz, glassy spherules, metallic particles, broken zircons, gypsum crystals with fragmented spherules and platinum group elements (Ir, Os, Pd). Fossils in the black clay are absent and only fossil evidence at the bottom is charred matter, covered by lignite mixed with spherules. Corals and pelecypod shells are incrusted by spherules. The lower unit is formed by cream-colored sandstones of a rudist-coral reef environment with variable thickness and the upper unit by sandstones with few gastropods and fragmented shells. The Rayon reef in the Valles-San Luis platform provides a high-resolution proximal record of Chicxulub impact in the Gulf of Mexico.
====
Roberto Bartali, Jaime Urrutia-Fucugauchi, Jose Ramon Torres-Hernandez, Ligia Perez-Cruz & Rosa Lina Tovar-Tovar (2026)
Unraveling the Cretaceous-Paleogene boundary event across the Gulf of Mexico—High-resolution Rayon reef section, Valles-San Luis Potosi platform, Mexico
PLOS ONE 21(4): e0345692
doi: https://doi.org/10.1371/journal.pone.0345692
https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0345692
The Cretaceous/Paleogene boundary, marked by the Chicxulub impact ejecta layer has a global distribution, with distal, intermediate and proximal boundary sections of distinct mineralogy, geochemistry and stratigraphy. Distal sections show a thin double-layer of spherulites and clay, enriched in platinum group elements and impact minerals. Proximal boundary sections around the Gulf of Mexico-Caribbean Sea are thicker, with clastic tsunami and debris flow deposits and the fireball layer in between the spherulitic and clay layers. Impact-induced disturbance and stratigraphic gaps have limited the resolution in unveiling the event sequence. Here we present a study on a recently discovered reef section in a carbonate platform, ~ 1,050 km away across the Gulf of Mexico. The boundary is marked by a black clay with shock quartz, glassy spherules, metallic particles, broken zircons, gypsum crystals with fragmented spherules and platinum group elements (Ir, Os, Pd). Fossils in the black clay are absent and only fossil evidence at the bottom is charred matter, covered by lignite mixed with spherules. Corals and pelecypod shells are incrusted by spherules. The lower unit is formed by cream-colored sandstones of a rudist-coral reef environment with variable thickness and the upper unit by sandstones with few gastropods and fragmented shells. The Rayon reef in the Valles-San Luis platform provides a high-resolution proximal record of Chicxulub impact in the Gulf of Mexico.
====
Free pdf:
Penny Barton, Gail Christeson, Sean Gulick, Joanna Morgan, Mario Rebolledo-Vieyra, Jaime Urrutia-Fucugauchi & Michael Warner (2026)
Seismic travel-time tomography under the peak ring of the Chicxulub impact crater
Geophysical Journal International, ggag152
doi: https://doi.org/10.1093/gji/ggag152
https://academic.oup.com/gji/advance-article/doi/10.1093/gji/ggag152/8661864
We present the results of a three-dimensional seismic tomography study of the upper crust beneath a quadrant of the peak ring structure of the Chicxulub meteorite impact crater, Mexico. Reflection and refraction travel-times from a grid of seismic profiles recorded by a 6 km streamer and 48 ocean bottom seismometer stations were inverted to give a well-resolved three-dimensional velocity model to a maximum depth of 6-8 km. The model comprised the thin water layer, a layer of low seismic velocity post-impact sedimentary infill, and the crater basement, which was separated from the fill by the interface representing the top of the crater, defined by normal incidence reflection picks. The crater basement shows a cylinder-shaped feature extending vertically downwards beneath the topographic peak ring to at least 8 km, the depth of resolution of this survey, characterised by slower seismic velocities than in the surrounding rocks at the same depth. This result supports and extends the observations of previous seismic refraction work in the peak ring, and also of scientific drilling, that the material in the peak ring has significantly reduced seismic velocity compared to typical granitic basement lithologies. We used the velocity model to perform a pre-stack depth migration of a key seismic reflection profile. In the best-fitting model presented here the prominent dipping reflector previously identified on seismic reflection profiles, which projects to the outer edge of the peak ring, dips inwards and crosses the low velocity cylinder without an apparent first order contrast in impedance. This result implies that the reflectivity of this dipping reflector is due to a thin, high-contrast layer such as entrapped impact melt or hydrothermal alteration within the overturned structures. We also identify well-imaged slump blocks from the crater rim/inner ring inwards, variations in the height and width of the peak ring, and associated variations in the velocity contrast that characterises the anomaly beneath the peak ring.
====
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