The first day of the Cenozoic

Highly expanded Cretaceous–Paleogene (K-Pg) boundary section from the Chicxulub peak ring, recovered by International Ocean Discovery Program (IODP)–International Continental Scientific Drilling Program (ICDP) Expedition 364, provides an unprecedented window into the immediate aftermath of the impact. Site M0077 includes ∼130 m of impact melt rock and suevite deposited the first day of the Cenozoic covered by <1 m of micrite-rich carbonate deposited over subsequent weeks to years. We present an interpreted series of events based on analyses of these drill cores. Within minutes of the impact, centrally uplifted basement rock collapsed outward to form a peak ring capped in melt rock. Within tens of minutes, the peak ring was covered in ∼40 m of brecciated impact melt rock and coarse-grained suevite, including clasts possibly generated by melt–water interactions during ocean resurge. Within an hour, resurge crested the peak ring, depositing a 10-m-thick layer of suevite with increased particle roundness and sorting. Within hours, the full resurge deposit formed through settling and seiches, resulting in an 80-m-thick fining-upward, sorted suevite in the flooded crater. Within a day, the reflected rim-wave tsunami reached the crater, depositing a cross-bedded sand-to-fine gravel layer enriched in polycyclic aromatic hydrocarbons overlain by charcoal fragments. Generation of a deep crater open to the ocean allowed rapid flooding and sediment accumulation rates among the highest known in the geologic record. The high-resolution section provides insight into the impact environmental effects, including charcoal as evidence for impact-induced wildfires and a paucity of sulfur-rich evaporites from the target supporting rapid global cooling and darkness as extinction mechanisms.

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Probing the hydrothermal system of the Chicxulub impact crater

Science Advances ◽

10.1126/sciadv.aaz3053 ◽

2020 ◽

Vol 6 (22) ◽

pp. eaaz3053 ◽

Cited By ~ 6

Author(s):

David A. Kring ◽

Sonia M. Tikoo ◽

Martin Schmieder ◽

Ulrich Riller ◽

Mario Rebolledo-Vieyra ◽

...

Keyword(s):

Hydrothermal System ◽

Earth’S Crust ◽

Scientific Drilling ◽

Chicxulub Impact Crater ◽

Earth's Crust ◽

International Ocean Discovery Program ◽

Geomagnetic Polarity ◽

Chicxulub Impact ◽

The Impact ◽

Yellowstone Caldera

The ~180-km-diameter Chicxulub peak-ring crater and ~240-km multiring basin, produced by the impact that terminated the Cretaceous, is the largest remaining intact impact basin on Earth. International Ocean Discovery Program (IODP) and International Continental Scientific Drilling Program (ICDP) Expedition 364 drilled to a depth of 1335 m below the sea floor into the peak ring, providing a unique opportunity to study the thermal and chemical modification of Earth’s crust caused by the impact. The recovered core shows the crater hosted a spatially extensive hydrothermal system that chemically and mineralogically modified ~1.4 × 105 km3 of Earth’s crust, a volume more than nine times that of the Yellowstone Caldera system. Initially, high temperatures of 300° to 400°C and an independent geomagnetic polarity clock indicate the hydrothermal system was long lived, in excess of 106 years.

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Shock-deformed zircon from the Chicxulub impact crater and implications for cratering process

Geology ◽

10.1130/g48278.1 ◽

2021 ◽

Author(s):

Jiawei Zhao ◽

Long Xiao ◽

Zhiyong Xiao ◽

Joanna V. Morgan ◽

Gordon R. Osinski ◽

...

Keyword(s):

High Pressure ◽

Thermal Evolution ◽

Ground Truth ◽

Large Impact ◽

Impact Melt ◽

Collapse Model ◽

Chicxulub Impact Crater ◽

International Ocean Discovery Program ◽

Chicxulub Impact ◽

The Impact

Large impact structures with peak rings are common landforms across the solar system, and their formation has implications for both the interior structure and thermal evolution of planetary bodies. Numerical modeling and structural studies have been used to simulate and ground truth peak-ring formative mechanisms, but the shock metamorphic record of minerals within these structures remains to be ascertained. We investigated impact-related microstructures and high-pressure phases in zircon from melt-bearing breccias, impact melt rock, and granitoid basement from the Chicxulub peak ring (Yucatán Peninsula, Mexico), sampled by the International Ocean Discovery Program (IODP)/International Continental Drilling Project (IODP-ICDP) Expedition 364 Hole M0077A. Zircon grains exhibit shock features such as reidite, zircon twins, and granular zircon including “former reidite in granular neoblastic” (FRIGN) zircon. These features record an initial high-pressure shock wave (>30 GPa), subsequent relaxation during the passage of the rarefaction wave, and a final heating and annealing stage. Our observed grain-scale deformation history agrees well with the stress fields predicted by the dynamic collapse model, as the central uplift collapsed downward-then-outward to form the peak ring. The occurrence of reidite in a large impact basin on Earth represents the first such discovery, preserved due to its separation from impact melt and rapid cooling by the resurging ocean. The coexistence of reidite and FRIGN zircon within the impact melt–bearing breccias indicates that cooling by seawater was heterogeneous. Our results provide valuable information on when different shock microstructures form and how they are modified according to their position in the impact structure, and this study further improves on the use of shock barometry as a diagnostic tool in understanding the cratering process.

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Introduction

Large Meteorite Impacts and Planetary Evolution VI ◽

10.1130/2021.2550(002) ◽

2021 ◽

Author(s):

Wolf Uwe Reimold ◽

Christian Koeberl

Keyword(s):

Electron Backscatter Diffraction ◽

Planetary Science ◽

Impact Cratering ◽

Scientific Drilling ◽

Meteorite Impacts ◽

International Ocean Discovery Program ◽

The University ◽

Backscatter Diffraction ◽

Chicxulub Impact ◽

The Impact

ABSTRACT This paper does not have an abstract. CONFERENCE The Large Meteorite Impacts and Planetary Evolution Conference VI (LMI VI) took place between 30 September and 3 October 2019 on the campus of the University of Brasília (UnB) in Brasília, Brazil. This series of essentially quintennial conferences has been a mainstay for three decades. It was initiated with the aim to review major research outcomes, share ideas, and fertilize new collaborations in the impact cratering and planetary science fields. The timing for LMI VI, related to the state of impact cratering research, was a good one. For example, the studies resulting from the important IODP-ICDP (International Ocean Discovery Program–International Continental Scientific Drilling Program) project, in which a deep drill core was retrieved from the peak ring of the Chicxulub impact structure—the smoking gun for the Cretaceous-Paleogene (K-Pg) boundary impact event coincident with the mass extinction at that time—were nearing completion and could be presented, in part, at LMI VI. Numerous other advances in impact research had been made in the preceding years (for example, state-of-the-art microstructural studies on accessary minerals with electron backscatter diffraction [EBSD]) and were extensively discussed at the conference. And, finally, interest in impact cratering has significantly increased in recent years, not only...

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Formation of the crater suevite sequence from the Chicxulub peak ring: A petrographic, geochemical, and sedimentological characterization

Geological Society of America Bulletin ◽

10.1130/b36020.1 ◽

2021 ◽

Author(s):

Pim Kaskes ◽

Sietze J. de Graaff ◽

Jean-Guillaume Feignon ◽

Thomas Déhais ◽

Steven Goderis ◽

...

Keyword(s):

Compositional Data ◽

Ocean Water ◽

New Classification ◽

Planktic Foraminifera ◽

Data Set ◽

Scientific Drilling ◽

International Ocean Discovery Program ◽

Chicxulub Impact ◽

The Impact

This study presents a new classification of a ∼100-m-thick crater suevite sequence in the recent International Ocean Discovery Program (IODP)-International Continental Scientific Drilling Program (ICDP) Expedition 364 Hole M0077A drill core to better understand the formation of suevite on top of the Chicxulub peak ring. We provide an extensive data set for this succession that consists of whole-rock major and trace element compositional data (n = 212) and petrographic data supported by digital image analysis. The suevite sequence is subdivided into three units that are distinct in their petrography, geochemistry, and sedimentology, from base to top: the ∼5.6-m-thick non-graded suevite unit, the ∼89-m-thick graded suevite unit, and the ∼3.5-m-thick bedded suevite unit. All of these suevite units have isolated Cretaceous planktic foraminifera within their clastic groundmass, which suggests that marine processes were responsible for the deposition of the entire M0077A suevite sequence. The most likely scenario describes that the first ocean water that reached the northern peak ring region entered through a N-NE gap in the Chicxulub outer rim. We estimate that this ocean water arrived at Site M0077 within 30 minutes after the impact and was relatively poor in rock debris. This water caused intense quench fragmentation when it interacted with the underlying hot impact melt rock, and this resulted in the emplacement of the ∼5.6-m-thick hyaloclastite-like, non-graded suevite unit. In the following hours, the impact structure was flooded by an ocean resurge rich in rock debris, which caused the phreatomagmatic processes to stop and the ∼89-m-thick graded suevite unit to be deposited. We interpret that after the energy of the resurge slowly dissipated, oscillating seiche waves took over the sedimentary regime and formed the ∼3.5-m-thick bedded suevite unit. The final stages of the formation of the impactite sequence (estimated to be <20 years after impact) were dominated by resuspension and slow atmospheric settling, including the final deposition of Chicxulub impactor debris. Cumulatively, the Site M0077 suevite sequence from the Chicxulub impact site preserved a high-resolution record that provides an unprecedented window for unravelling the dynamics and timing of proximal marine cratering processes in the direct aftermath of a large impact event.

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Rapid macrobenthic diversification and stabilization after the end-Cretaceous mass extinction event

Geology ◽

10.1130/g47589.1 ◽

2020 ◽

Vol 48 (11) ◽

pp. 1048-1052

Author(s):

Francisco J. Rodríguez-Tovar ◽

Christopher M. Lowery ◽

Timothy J. Bralower ◽

Sean P.S. Gulick ◽

Heather L. Jones

Keyword(s):

Mass Extinction ◽

Rapid Recovery ◽

Community Recovery ◽

Scientific Drilling ◽

Extinction Event ◽

Chicxulub Impact Crater ◽

Mass Extinction Event ◽

International Ocean Discovery Program ◽

Extinction Events ◽

The Impact

Abstract Previous ichnological analysis at the Chicxulub impact crater, Yucatán Peninsula, México (International Ocean Discovery Program [IODP]/International Continental Scientific Drilling Program [ICDP] Site M0077), showed a surprisingly rapid initial tracemaker community recovery after the end-Cretaceous (Cretaceous-Paleogene [K-Pg]) mass extinction event. Here, we found that full recovery was also rapid, with the establishment of a well-developed tiered community within ∼700 k.y. Several stages of recovery were observed, with distinct phases of stabilization and diversification, ending in the development of a trace fossil assemblage mainly consisting of abundant Zoophycos, Chondrites, and Planolites, assigned to the Zoophycos ichnofacies. The increase in diversity is associated with higher abundance, larger forms, and a deeper and more complex tiering structure. Such rapid recovery suggests that favorable paleoenvironmental conditions were quickly reestablished within the impact basin, enabling colonization of the substrate. Comparison with the end-Permian extinction reveals similarities during recovery, yet postextinction recovery was significantly faster after the K-Pg event. The rapid recovery has significant implications for the evolution of macrobenthic biota after the K-Pg event. Our results have relevance in understanding how communities recovered after the K-Pg impact and how this event differed from other mass extinction events.

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Review on Sublethal Effects of Environmental Contaminants in Honey Bees (Apis mellifera), Knowledge Gaps and Future Perspectives

International Journal of Environmental Research and Public Health ◽

10.3390/ijerph18041863 ◽

2021 ◽

Vol 18 (4) ◽

pp. 1863 ◽

Cited By ~ 2

Author(s):

Agata Di Noi ◽

Silvia Casini ◽

Tommaso Campani ◽

Giampiero Cai ◽

Ilaria Caliani

Keyword(s):

Apis Mellifera ◽

Honey Bees ◽

Sublethal Effects ◽

Integrated Approach ◽

Anthropogenic Contamination ◽

Knowledge Gaps ◽

Pollination Services ◽

General Decline ◽

Polycyclic Aromatic ◽

The Impact

Honey bees and the pollination services they provide are fundamental for agriculture and biodiversity. Agrochemical products and other classes of contaminants, such as trace elements and polycyclic aromatic hydrocarbons, contribute to the general decline of bees’ populations. For this reason, effects, and particularly sublethal effects of contaminants need to be investigated. We conducted a review of the existing literature regarding the type of effects evaluated in Apis mellifera, collecting information about regions, methodological approaches, the type of contaminants, and honey bees’ life stages. Europe and North America are the regions in which A. mellifera biological responses were mostly studied and the most investigated compounds are insecticides. A. mellifera was studied more in the laboratory than in field conditions. Through the observation of the different responses examined, we found that there were several knowledge gaps that should be addressed, particularly within enzymatic and molecular responses, such as those regarding the immune system and genotoxicity. The importance of developing an integrated approach that combines responses at different levels, from molecular to organism and population, needs to be highlighted in order to evaluate the impact of anthropogenic contamination on this pollinator species.

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Grill Workers Exposure to Polycyclic Aromatic Hydrocarbons: Levels and Excretion Profiles of the Urinary Biomarkers

International Journal of Environmental Research and Public Health ◽

10.3390/ijerph18010230 ◽

2020 ◽

Vol 18 (1) ◽

pp. 230

Author(s):

Marta Oliveira ◽

Sílvia Capelas ◽

Cristina Delerue-Matos ◽

Simone Morais

Keyword(s):

Polycyclic Aromatic Hydrocarbons ◽

Aromatic Hydrocarbons ◽

High Performance ◽

Principal Component ◽

Fold Increase ◽

Urinary Biomarkers ◽

Analysis Model ◽

Exposed Workers ◽

Polycyclic Aromatic ◽

The Impact

Grilling activities release large amounts of hazardous pollutants, but information on restaurant grill workers’ exposure to polycyclic aromatic hydrocarbons (PAHs) is almost inexistent. This study assessed the impact of grilling emissions on total workers’ exposure to PAHs by evaluating the concentrations of six urinary biomarkers of exposure (OHPAHs): naphthalene, acenaphthene, fluorene, phenanthrene, pyrene, and benzo(a)pyrene. Individual levels and excretion profiles of urinary OHPAHs were determined during working and nonworking periods. Urinary OHPAHs were quantified by high-performance liquid-chromatography with fluorescence detection. Levels of total OHPAHs (∑OHPAHs) were significantly increased (about nine times; p ≤ 0.001) during working comparatively with nonworking days. Urinary 1-hydroxynaphthalene + 1-hydroxyacenapthene and 2-hydroxyfluorene presented the highest increments (ca. 23- and 6-fold increase, respectively), followed by 1-hydroxyphenanthrene (ca. 2.3 times) and 1-hydroxypyrene (ca. 1.8 times). Additionally, 1-hydroxypyrene levels were higher than the benchmark, 0.5 µmol/mol creatinine, in 5% of exposed workers. Moreover, 3-hydroxybenzo(a)pyrene, biomarker of exposure to carcinogenic PAHs, was detected in 13% of exposed workers. Individual excretion profiles showed a cumulative increase in ∑OHPAHs during consecutive working days. A principal component analysis model partially discriminated workers’ exposure during working and nonworking periods showing the impact of grilling activities. Urinary OHPAHs were increased in grill workers during working days.

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Review of the relationship between aggregates geology and Los Angeles and micro-Deval tests

Bulletin of Engineering Geology and the Environment ◽

10.1007/s10064-020-02097-y ◽

2021 ◽

Vol 80 (3) ◽

pp. 1963-1980

Author(s):

Solomon Adomako ◽

Christian John Engelsen ◽

Rein Terje Thorstensen ◽

Diego Maria Barbieri

Keyword(s):

Los Angeles ◽

Crystal Size ◽

Grain Shape ◽

Mechanical Performance ◽

Pore Space ◽

Construction Material ◽

Engineering Properties ◽

Coarse Grained ◽

The Impact ◽

The Relationship

AbstractRock aggregates constitute the enormous volume of inert construction material used around the globe. The petrologic description as igneous, sedimentary, and metamorphic types establishes the intrinsic formation pattern of the parent rock. The engineering properties of these rocks vary due to the differences in the transformation process (e.g. hydrothermal deposits) and weathering effect. The two most common mechanical tests used to investigate the performance of aggregates are the Los Angeles (LA) and micro-Deval (MD) tests. This study reviewed the geological parameters (including mineralogy, grain and crystal size, grain shape, and porosity) and the relationship to Los Angeles and micro-Deval tests. It was found that high content of primary minerals in rocks (e.g. quartz and feldspar) is a significant parameter for performance evaluation. Traces of secondary and accessory minerals also affect the performance of rocks, although in many cases it is based on the percentage. Furthermore, some studies showed that the effect of mineralogic composition on mechanical strength is not sufficient to draw final conclusions of mechanical performance; therefore, the impact of other textural characteristics should be considered. The disposition of grain size and crystal size (e.g. as result of lithification) showed that rocks composed of fine-grain textural composition of ≤ 1 mm enhanced fragmentation and wear resistance than medium and coarse grained (≥ 1 mm). The effect of grain shape was based on convex and concave shapes and flat and elongated apexes of tested samples. The equidimensional form descriptor of rocks somehow improved resistance to impact from LA than highly flat and elongated particles. Lastly, the distribution of pore space investigated by means of the saturation method mostly showed moderate (R = 0.50) to strong (R = 0.90) and positive correlations to LA and MD tests.

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Evaluating the impact of exposure to environmental contaminants on human health

Clinical Chemistry ◽

10.1093/clinchem/42.8.1345 ◽

1996 ◽

Vol 42 (8) ◽

pp. 1345-1349 ◽

Cited By ~ 22

Author(s):

J B Silkworth ◽

J F Brown

Keyword(s):

Chemical Substances ◽

The Public ◽

Aromatic Hydrocarbon Receptor ◽

Naturally Occurring ◽

Synthetic Chemicals ◽

Low Concentrations ◽

Polycyclic Aromatic ◽

Coplanar Polychlorinated Biphenyls ◽

Proportional Contribution ◽

The Impact

Abstract Humans are exposed daily to low concentrations of many different chemical substances, natural and some man-made. Although many of these substances can be toxic at high levels, typical exposures are far below the effect levels. The responses produced by man-made aromatic hydrocarbon receptor agonists, such as dioxins, polychlorinated dibenzofurans, coplanar polychlorinated biphenyls, and polycyclic aromatic hydrocarbons, are also produced, often to greater extents [corrected], by naturally occurring constituents of fried meat, cabbage, broccoli, cauliflower, cocoa, and curry. Our society seems to be concerned about the health risks associated only with the synthetic chemicals, regardless of their proportional contribution to the total agonist activity, and regulates on the basis of such concerns. It would be more protective of the public health to determine acceptable concentrations for each type of response, regardless of the origin of the inducing agent, and issue advisories or regulations accordingly.

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