Organic matter from the Chicxulub crater exacerbated the K–Pg impact winter

An asteroid impact in the Yucatán Peninsula set off a sequence of events that led to the Cretaceous–Paleogene (K–Pg) mass extinction of 76% species, including the nonavian dinosaurs. The impact hit a carbonate platform and released sulfate aerosols and dust into Earth’s upper atmosphere, which cooled and darkened the planet—a scenario known as an impact winter. Organic burn markers are observed in K–Pg boundary records globally, but their source is debated. If some were derived from sedimentary carbon, and not solely wildfires, it implies soot from the target rock also contributed to the impact winter. Characteristics of polycyclic aromatic hydrocarbons (PAHs) in the Chicxulub crater sediments and at two deep ocean sites indicate a fossil carbon source that experienced rapid heating, consistent with organic matter ejected during the formation of the crater. Furthermore, PAH size distributions proximal and distal to the crater indicate the ejected carbon was dispersed globally by atmospheric processes. Molecular and charcoal evidence indicates wildfires were also present but more delayed and protracted and likely played a less acute role in biotic extinctions than previously suggested. Based on stratigraphy near the crater, between 7.5 × 1014and 2.5 × 1015g of black carbon was released from the target and ejected into the atmosphere, where it circulated the globe within a few hours. This carbon, together with sulfate aerosols and dust, initiated an impact winter and global darkening that curtailed photosynthesis and is widely considered to have caused the K–Pg mass extinction.

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BPOP-v1 model: exploring the impact of changes in the biological pump on the shelf sea and ocean nutrient and redox state

10.5194/gmd-2019-182 ◽

2019 ◽

Author(s):

Elisa Lovecchio ◽

Timothy M. Lenton

Keyword(s):

Organic Matter ◽

Deep Ocean ◽

Biological Pump ◽

Promising Tool ◽

Biogeochemical Fluxes ◽

Structure Changes ◽

Large Particles ◽

Shelf Sea ◽

Slope Sediment ◽

The Impact

Abstract. The ocean’s biological pump has changed over Earth history from one dominated by prokaryotes, to one involving a mixture of prokaryotes and eukaryotes with trophic structure. Changes in the biological pump are in turn hypothesised to have caused important changes in the ocean’s nutrient and redox properties. To explore these hypotheses, we present here a new box model including oxygen (O), phosphorus (P) and a dynamical biological pump. Our Biological Pump, Oxygen and Phosphorus (BPOP) model accounts for two – small and large – organic matter species generated by production and coagulation, respectively. Export and burial of these particles are regulated by a remineralization length (zrem) scheme. We independently vary zrem of small and large particles in order to study how changes in sinking speeds and remineralization rates affect the major biogeochemical fluxes, and O and P ocean concentrations. Modelled O and P budgets and fluxes lay close to present estimates for zrem in the range of currently measured values. Our results highlight that relatively small changes in zrem of the large particles can have important impacts on the O and P ocean availability and support the idea that an early ocean dominated by small particles was nutrient rich due to inefficient removal to sediments. The results also highlight that shelf ocean anoxia can coexist with an oxygenated deep open ocean for realistic values of zrem, especially for large values of the small particle zrem. This could challenge conventional interpretations that the Proterozoic deep ocean was anoxic, which are derived from shelf and slope sediment redox data. This simple and computationally inexpensive model is a promising tool to investigate the impact of changes in the organic matter sinking and remineralization rates as well as changes in physical processes coupled to the biological pump in a variety of case studies.

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Rock Magnetic and Magnetostratigraphic Study of Chicxulub Crater Impact Breccias and Post-Impact Carbonates in the Yaxcopoil-1 and Santa Elena Boreholes

10.5194/egusphere-egu2020-19628 ◽

2020 ◽

Author(s):

Jaime Urrutia-Fucugauchi ◽

Ligia Perez-Cruz ◽

Elia Escobar-Sanchez ◽

Miriam Velasco-Villarreal ◽

Edgar Garcia-Garnica

Keyword(s):

Oxygen Isotope ◽

Carbonate Platform ◽

Magnetic Hysteresis ◽

Magnetization Vector ◽

Carbonate Sediments ◽

Carbon And Oxygen Isotope ◽

Post Impact ◽

Chicxulub Crater ◽

The Impact ◽

Santa Elena

Chicxulub crater was formed ~66 Ma ago by an asteroid impact at the Cretaceous/Paleogene (K/Pg) boundary on the Yucatan carbonate platform in the southern Gulf of Mexico. The crater is the youngest and best preserved of the three large impact basins, with a ~200 km diameter and multi-ring and peak ring morphology. The crater, covered by post-impact carbonate sediments with thickness up to ~1.1 km, has been investigated by geophysical studies and drilling programs. Initial drilling in Yucatan was carried out by the Pemex oil company, followed by the National University UNAM Chicxulub program, the ICDP Yaxcopoil-1 project and the IODP-ICDP Expedition 364 marine drilling. Here, results of combined paleomagnetic, rock magnetic, petrographic and geochemical studies are used to characterize the sequence and constrain the unit&#8217;s emplacement and crater formation. We analyze core samples of suevitic breccias and Paleogene carbonates from the Yaxcopoil-1 and Santa Elena boreholes drilled in the southern sector, inside and to the south of the crater rim marked by the ring of cenotes. &#160;Magnetic hysteresis, low-field susceptibility and coercitivity analyses indicate that main carriers are titanomagnetites and magnetite. Mineralogical and magnetic properties indicate effects of hydrothermal alteration, associated with the high temperature system generated by the impact. Higher coercitivity minerals are also observed in some samples. In the carbonate sections, hydrothermal effects as marked by the geochemical logs decrease upwards from the breccia-carbonate contact. Alternating field and thermal demagnetization is used to investigate the magnetization vector composition and isolate the characteristic remanent components. Magnetic polarities defined from the inclination data show a sequence of reverse to normal, which correlate to polarity chrons 29r to 26r, with impact occurring within 29r chron.&#160; The correlations of the magnetostratigraphy and stable isotopes indicate a hiatus at the basal Paleocene section. In Santa Elena cores, d13C values range from 1.2 to 3.5%0 and d18O values range from -1.4 to -4.8%0, with variation trends correlating with the marine carbon and oxygen isotope records for the late Maastrichtian and early Paleocene. The positive carbon isotopes indicate high productivity after the K/Pg extinction event, while the oxygen isotope values are more negative reflecting regional and local effects. Silica contents decrease from high in the suevites to low values in carbonates showing higher variability and then increased contents at the Paleocene-Eocene Thermal Maximum (PETM). The geochemical trends correlate in other elements including iron, titanium, potassium and aluminum that record impact-induced hydrothermal effects and possibly changing depositional conditions. Ca shows an opposite trend, with lower values in the upper suevitic breccias, higher values in the Paleocene carbonates and lower values in the PETM.

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Anoxic metabolism after the 21st century in oxygen minimum zones

10.5194/egusphere-egu2020-13038 ◽

2020 ◽

Author(s):

Wolfgang Koeve ◽

Angela Landolfi

Keyword(s):

Organic Matter ◽

Ocean Circulation ◽

Large Scale ◽

Deep Ocean ◽

Sulphate Reduction ◽

Oxygen Minimum Zones ◽

The Future ◽

Ocean Models ◽

The Impact ◽

Oxygen Minimum

Global models project a decrease of marine oxygen over the course of the 21th century. The future of marine oxygen becomes increasingly uncertain further into the future after yr 2100 , partly because ocean models differ in the way organic matter remineralisation continues under oxygen- and nitrate-free conditions. Using an Earth system model of intermediate complexity we found that under a business-as-usual CO2-emission scenario ocean deoxygenation further intensifies for several centuries until eventually ocean circulation re-establishes and marine oxygen increases again. (Oschlies et al. 2019, DOI 10.1038/s41467-019-10813-w).In the Pacific Ocean the deoxygenation after yr 2100 goes along with the large scale loss of nitrate from oxygen minimum zones. Here we explore the impact on simulated ocean biogeochemistry of three different process formulation of anoxic metabolism, which have been used in other ocean models: (1) implicit sulphate reduction (organic matter degradation continues without oxidant), (2) no sulphidic metabolism (organic matter is not degraded under anoxic conditions), and (3) explicit sulphate reduction (with H2S as explicit model tracer). The model with explicit sulfphate reduction supports larger regional organic matter fluxed into the deep ocean and an increase in respired carbon storage, compared with the model applying implicit sulphate. We discuss the impact of anoxic metabolism on the coupling between export production and respired carbon stored in the ocean interior.

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Deccan Volcanism or the Chicxulub Impact: The Chicken or Egg Question

10.5194/egusphere-egu2020-22414 ◽

2020 ◽

Author(s):

Gerta Keller

Keyword(s):

Mass Extinction ◽

Impact Crater ◽

Global Climate ◽

Mass Extinctions ◽

Deccan Volcanism ◽

Asteroid Impact ◽

Global Climate Warming ◽

Chicxulub Impact Crater ◽

Chicxulub Impact ◽

The Impact

The Cretaceous&#8211;Paleogene boundary (KTB or KPB) mass extinction is primarily known for the demise of the dinosaurs, the Chicxulub impact, and the rancorous forty-year-old controversy over the cause of this mass extinction. For the first 30 years, the controversy primarily revolved around the age of the impact claimed as precisely KTB based on the assumption that it caused the mass extinction. The iridium (Ir) anomaly at the KTB was claimed proof of the asteroid impact, but no Ir was ever associated with impact evidence and recent findings reveal no extraterrestrial component in PGEs or the KTB Ir anomaly. Impact melt rock glass spherules are also claimed as indisputable evidence of the KTB age impact, but such spherule layers are commonly reworked from the primary (oldest) layer in late Maastrichtian, KTB and Danian sediments; thus only the oldest impact spherule layer documented near the base of zone CF1 ~200 ky below the KTB can approximate the impact&#8217;s age. Similarly, the impact breccia in the Chicxulub impact crater predates the KTB. The best age derived from Ar/Ar dating of impact glass spherules is within 200 ky of the KTB and thus no evidence for the KTB age. All evidence strongly suggests the Chicxulub impact most likely predates the mass extinction ~ 200 ky and played no role in it. Deccan volcanism (LIP) was dismissed as potential cause or even contributor to the KTB mass extinction despite the fact that all other mass extinctions are associated with Large Igneous Province (LIP) volcanism but none with an asteroid impact. During the last decade, Deccan volcanism gained credence based on a succession of discoveries: 1) the mass extinction in between the longest Deccan lava flows across India; 2) high-precision dating of the entire sequence of Deccan volcanism based on UPb zircon dating; 3) recognition of four distinct eruption pulses all related to global climate warming with the largest pulse beginning 20 ky prior to and ending at the KTB; 4) Identifying the climate link to Deccan volcanism based on age dating and mercury from Deccan eruptions in marine sediments; and 5) Identifying the KTB mass extinction directly related to the major Deccan eruption pulse, hyperthermal warming and ocean acidification all linked to global mercury fallout from Deccan eruptions in marine sediments. Despite this remarkable culmination of evidence, the controversy continues with impact proponents arguing that Deccan volcanism didn&#8217;t exist at the KTB &#8211; the impact was the sole cause.

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Microbial life in the nascent Chicxulub crater

Geology ◽

10.1130/g46799.1 ◽

2020 ◽

Vol 48 (4) ◽

pp. 328-332 ◽

Cited By ~ 9

Author(s):

Bettina Schaefer ◽

Kliti Grice ◽

Marco J.L. Coolen ◽

Roger E. Summons ◽

Xingqian Cui ◽

...

Keyword(s):

Microbial Mats ◽

Nutrient Supply ◽

Core Material ◽

Asteroid Impact ◽

Microbial Life ◽

Sulfur Bacteria ◽

Post Impact ◽

Photosynthetic Sulfur Bacteria ◽

Chicxulub Crater ◽

The Impact

Abstract The Chicxulub crater was formed by an asteroid impact at ca. 66 Ma. The impact is considered to have contributed to the end-Cretaceous mass extinction and reduced productivity in the world’s oceans due to a transient cessation of photosynthesis. Here, biomarker profiles extracted from crater core material reveal exceptional insights into the post-impact upheaval and rapid recovery of microbial life. In the immediate hours to days after the impact, ocean resurge flooded the crater and a subsequent tsunami delivered debris from the surrounding carbonate ramp. Deposited material, including biomarkers diagnostic for land plants, cyanobacteria, and photosynthetic sulfur bacteria, appears to have been mobilized by wave energy from coastal microbial mats. As that energy subsided, days to months later, blooms of unicellular cyanobacteria were fueled by terrigenous nutrients. Approximately 200 k.y. later, the nutrient supply waned and the basin returned to oligotrophic conditions, as evident from N2-fixing cyanobacteria biomarkers. At 1 m.y. after impact, the abundance of photosynthetic sulfur bacteria supported the development of water-column photic zone euxinia within the crater.

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Viral infection switches the balance between bacterial and eukaryotic recyclers of organic matter during algal blooms

10.1101/2021.10.25.465659 ◽

2021 ◽

Author(s):

Flora Vincent ◽

Matti Gralka ◽

Guy Schleyer ◽

Daniella J Schatz ◽

Miguel Cabrera-Brudau ◽

...

Keyword(s):

Organic Matter ◽

Viral Infection ◽

Algal Blooms ◽

Large Scale ◽

Deep Ocean ◽

Trophic Levels ◽

Microbiome Composition ◽

Carbon Release ◽

Open Question ◽

The Impact

Algal blooms are hotspots of marine primary production and play central roles in microbial ecology and global nutrient cycling. When blooms collapse, organic carbon is transferred to higher trophic levels, microbial respiration or sinking in proportions that depend on the dominant mortality agent. Viral infection can lead to bloom termination, but its impact on the fate of carbon remains an open question. Here, we characterized the consequences of viral infection on the microbiome composition and biogeochemical landscape of marine ecosystems by conducting a large-scale mesocosm experiment. Moniroting of seven induced coccolithophore blooms, which showed different degrees of viral infection, revealed that only high levels of viral infection caused significant shifts in the composition of free-living bacterial and eukaryotic assemblages. Intriguingly, viral infection favored the growth of eukaryotic heterotrophs (thraustochytrids) over bacteria as potential recyclers of organic matter. By combining modeling and quantification of active viral infection at a single-cell resolution, we estimate that viral infection can increase per-cell rates of extracellular carbon release by 2-4.5 fold. This happened via production of acidic polysaccharides and particulate inorganic carbon, two major contributors to carbon sinking into the deep ocean. These results reveal the impact of viral infection on the fate of carbon through microbial recyclers of organic matter in large-scale coccolithophore blooms.

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Chicxulub Structure: A Volcanic Sequence of Late Cretaceous Age

The Paleontological Society Special Publications ◽

10.1017/s2475262200009692 ◽

1994 ◽

Vol 7 ◽

pp. 425-436

Author(s):

Charles B. Officer

Keyword(s):

New Zealand ◽

Residence Time ◽

Late Cretaceous ◽

Food Chain ◽

Mass Extinction ◽

Dust Cloud ◽

Asteroid Impact ◽

Extinction Event ◽

Mass Extinction Event ◽

The Impact

The present Cretaceous/Tertiary extinction debate started with findings by Alvarez et al. (1980) of enhanced levels of iridium at K/T sections in Italy, Denmark and New Zealand. They postulated that the iridium was extraterrestrial in origin and related to a 10 km diameter asteroid impact which would have produced a crater some 200 km in diameter. They further suggested that a giant dust cloud would have been injected into the stratosphere from the impact with a residence time of several years and that the resulting darkness would have suppressed photosynthesis with a consequent elimination of succeeding members in the biological food chain — ergo, a mass extinction event.

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Severe perturbations of the marine biosphere following the Chicxulub impact

10.5194/egusphere-egu2020-8025 ◽

2020 ◽

Author(s):

Georg Feulner ◽

Julia Brugger ◽

Matthias Hofmann ◽

Stefan Petri

Keyword(s):

Nutrient Availability ◽

Primary Productivity ◽

Mass Extinction ◽

Net Primary Productivity ◽

Ocean Model ◽

Sulfate Aerosols ◽

Surface Cooling ◽

Chicxulub Impact ◽

The Impact ◽

Marine Biosphere

Among the "big five" mass-extinction events during the Phanerozoic, the end-Cretaceous extinction 66 million years ago is particularly well known because it marks the demise of the non-avian dinosaurs. Evidence for the Chicxulub impact as the primary cause of this mass extinction has been accumulating over the past four decades, but there are still many open questions regarding the detailed course of events.Building on our earlier modelling results demonstrating strong global cooling due to sulfate aerosols formed in the wake of the Chicxulub impact (Brugger, Feulner & Petri 2017, Geophys. Res. Lett., 44:419-427), we here explore the response of the ocean in more detail. Specifically, we added a marine biogeochemistry module to a coupled atmosphere-ocean model to investigate the effects of the impact on ocean geochemistry and primary productivity.We find that the formation of stratospheric sulfate aerosols leads to a marked decrease in annual global mean surface air temperatures by at least 26&#176;C in the coldest year after the impact, returning to pre-impact temperatures after about one century. The strong surface cooling induces vigorous ocean mixing that leads to changes in oxygen distributions and nutrient availability. Due to the darkness, marine net primary productivity essentially shuts down in the first years after the impact. Once the light returns, however, we find a significant increase in primary productivity caused by a surge in nutrient availability, both due to upwelling in the ocean and delivery by the impactor. These strong perturbations of the marine biosphere further support the notion that the impact played a decisive role in the end-Cretaceous mass extinction.

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Viral infection switches the balance between bacterial and eukaryotic recyclers of organic matter during algal blooms

10.21203/rs.3.rs-1045578/v1 ◽

2021 ◽

Author(s):

Flora VINCENT ◽

Matti Gralka ◽

Guy Schleyer ◽

Daniella Schatz ◽

Miguel Cabrera-Brufau ◽

...

Keyword(s):

Organic Matter ◽

Viral Infection ◽

Algal Blooms ◽

Large Scale ◽

Deep Ocean ◽

Trophic Levels ◽

Microbiome Composition ◽

Carbon Release ◽

Open Question ◽

The Impact

Abstract Algal blooms are hotspots of marine primary production and play central roles in microbial ecology and global nutrient cycling. When blooms collapse, organic carbon is transferred to higher trophic levels, microbial respiration or sinking in proportions that depend on the dominant mortality agent. Viral infection can lead to bloom termination, but its impact on the fate of carbon remains an open question. Here, we characterized the consequences of viral infection on the microbiome composition and biogeochemical landscape of marine ecosystems by conducting a large-scale mesocosm experiment. Moniroting of seven induced coccolithophore blooms, which showed different degrees of viral infection, revealed that only high levels of viral infection caused significant shifts in the composition of free-living bacterial and eukaryotic assemblages. Intriguingly, viral infection favored the growth of eukaryotic heterotrophs (thraustochytrids) over bacteria as potential recyclers of organic matter. By combining modeling and quantification of active viral infection at a single-cell resolution, we estimate that viral infection can increase per-cell rates of extracellular carbon release by 2-4.5 fold. This happened via production of acidic polysaccharides and particulate inorganic carbon, two major contributors to carbon sinking into the deep ocean. These results reveal the impact of viral infection on the fate of carbon through microbial recyclers of organic matter in large-scale coccolithophore blooms.

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BPOP-v1 model: exploring the impact of changes in the biological pump on the shelf sea and ocean nutrient and redox state

Geoscientific Model Development ◽

10.5194/gmd-13-1865-2020 ◽

2020 ◽

Vol 13 (4) ◽

pp. 1865-1883 ◽

Cited By ~ 1

Author(s):

Elisa Lovecchio ◽

Timothy M. Lenton

Keyword(s):

Organic Matter ◽

Deep Ocean ◽

Biological Pump ◽

Low Oxygen ◽

Promising Tool ◽

Structure Changes ◽

Large Particles ◽

Shelf Sea ◽

Slope Sediment ◽

The Impact

Abstract. The biological pump of the ocean has changed over Earth's history, from one dominated by prokaryotes to one involving a mixture of prokaryotes and eukaryotes with trophic structure. Changes in the biological pump are in turn hypothesized to have caused important changes in the nutrient and redox properties of the ocean. To explore these hypotheses, we present here a new box model including oxygen (O), phosphorus (P) and a dynamical biological pump. Our Biological Pump, Oxygen and Phosphorus (BPOP) model accounts for two – small and large – organic matter species generated by production and coagulation, respectively. Export and burial of these particles are regulated by a remineralization length (zrem) scheme. We independently vary zrem of small and large particles in order to study how changes in sinking speeds and remineralization rates affect the major biogeochemical fluxes and O and P ocean concentrations. Modeled O and P budgets and fluxes lie reasonably close to present estimates for zrem in the range of currently measured values. Our results highlight that relatively small changes in zrem of the large particles can have important impacts on the O and P ocean availability and support the idea that an early ocean dominated by small particles was nutrient rich due to the inefficient removal of P to sediments. The results also suggest that extremely low oxygen concentrations in the shelf can coexist with an oxygenated deep open ocean for realistic values of zrem, especially for large values of the small-particle zrem. This could challenge conventional interpretations that the Proterozoic deep ocean was anoxic, which are derived from shelf and slope sediment redox data. This simple and computationally inexpensive model is a promising tool to investigate the impact of changes in the organic matter sinking and remineralization rates as well as changes in physical processes coupled with the biological pump in a variety of case studies.

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