Peak-ring formation in large impact craters: geophysical constraints from Chicxulub

Morgan, J. V.; Warner, Michael; Collins, G. S.; Melosh, H. J.; Christeson, G. L.

doi:10.1016/s0012-821x(00)00307-1

Cited by 119 publications

(142 citation statements)

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“…During this collapse, structural uplift of the crater floor produces a central uplift, which is overheightened and unstable under gravity. The subsequent outward collapse of the central uplift leads to the formation of a ring of peaks between the crater center and the crater rim (Morgan et al, 2000(Morgan et al, , 2011. This model for peak-ring formation is consistent with seismic data that show inward-collapsed Mesozoic rocks lie directly beneath the peak ring at Chicxulub at all azimuths (Morgan et al, 2000;Gulick et al, 2013).…”

Section: Introductionsupporting

confidence: 83%

“…The acquired seismic data show that the water was deeper and the Mesozoic sediments thicker in the northeast quadrant of the crater than in the other quadrants (Bell et al, 2004;Gulick et al, 2008) and that lateral variation in the target at the impact site might explain the current crater asymmetry (Collins et al, 2008). Velocities and densities of the rocks that form the peak ring are low (Morgan et al, 2000;Vermeesch and Morgan, 2008;Barton et al, 2010), and a high-resolution velocity model obtained using full-waveform inversion ( Figure F4) shows that the uppermost peak ring is formed from about 100-150 m of rocks with low P-wave velocity (3000-3200 m/s) (Morgan et al, 2011). Given the lack of intact peak rings exposed at the Earth's surface, there is no consensus as to either their geologic nature (of what material are they composed and from what stratigraphic location this material originates) or the mode of formation of a peak ring.…”

Section: Introductionmentioning

confidence: 94%

“…Geophysical data indicate that the peak ring at Chicxulub is formed from rocks that have low velocity and density, and one explanation for this is that they are highly fractured and porous (Morgan et al, 2000(Morgan et al, , 2011Gulick et al, 2013). Immediately after impact, the peak ring was submerged under water and located adjacent to a thick pool of hot impact melt.…”

Section: Introductionmentioning

confidence: 99%

“…Modified from ; from Nature Geoscience. formed during the collapse of a deep bowl-shaped "transient cavity" formed during the initial stages of cratering ( Figure F5) (Morgan et al, 2000;Collins et al, 2002;Ivanov, 2005;Senft and Stewart, 2009). During this collapse, structural uplift of the crater floor produces a central uplift, which is overheightened and unstable under gravity.…”

Section: Introductionmentioning

confidence: 99%

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Volume 364: Chicxulub: Drilling the K-Pg Impact Crater

Morgan¹,

Gulick²,

Mellett³

et al. 2017

Proceedings of the International Ocean Discovery Program

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The Chicxulub impact crater, on the Yucatán Peninsula of Méx-ico, is unique. It is the only known terrestrial impact structure that has been directly linked to a mass extinction event and the only terrestrial impact with a global ejecta layer. Of the three largest impact structures on Earth, Chicxulub is the best preserved. Chicxulub is also the only known terrestrial impact structure with an intact, unequivocal topographic peak ring. Chicxulub's role in the Cretaceous/Paleogene (K-Pg) mass extinction and its exceptional state of preservation make it an important natural laboratory for the study of both large impact crater formation on Earth and other planets and the effects of large impacts on the Earth's environment and ecology. Our understanding of the impact process is far from complete, and despite more than 30 years of intense debate, we are still striving to answer the question as to why this impact was so catastrophic.During International Ocean Discovery Program (IODP) and International Continental Scientific Drilling Program (ICDP) Expedition 364, Paleogene sedimentary rocks and lithologies that make up the Chicxulub peak ring were cored to investigate (1) the nature and formational mechanism of peak rings, (2) how rocks are weakened during large impacts, (3) the nature and extent of post-impact hydrothermal circulation, (4) the deep biosphere and habitability of the peak ring, and (5) the recovery of life in a sterile zone. Other key targets included sampling the transition through a rare midlatitude Paleogene sedimentary succession that might include Eocene and Paleocene hyperthermals and/or the Paleocene/Eocene Thermal Maximum (PETM); the composition and character of suevite, impact melt rock, and basement rocks in the peak ring; the sedimentology and stratigraphy of the Paleocene-Eocene Chicxulub impact basin infill; the geo-and thermochronology of the rocks forming the peak ring; and any observations from the core that may help constrain the volume of dust and climatically active gases released into the stratosphere by this impact. Petrophysical properties measurements on the core and wireline logs acquired during Expedition 364 will be used to calibrate geophysical models, including seismic reflection and potential field data, and the integration of all the data will calibrate models for impact crater formation and environmental effects. The drilling directly contributes to IODP Science Plan goals:Climate and Ocean Change: How does Earth's climate system respond to elevated levels of atmospheric CO 2 ? How resilient is the ocean to chemical perturbations? The Chicxulub impact represents an external forcing event that caused a 75% species level mass extinction. The impact basin may also record key hyperthermals within the Paleogene.Biosphere Frontiers: What are the origin, composition, and global significance of subseafloor communities? What are the limits of life in the subseafloor? How sensitive are ecosystems and biodiversity to environmental change? Impact craters can create habitats fo...

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Section: Introductionsupporting

confidence: 83%

Section: Introductionmentioning

confidence: 94%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Volume 364: Chicxulub: Drilling the K-Pg Impact Crater

Morgan¹,

Gulick²,

Mellett³

et al. 2017

Proceedings of the International Ocean Discovery Program

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“…Breccias formation for the first approximation was considered as a homogeneous layer, which resulted in a relatively poor fit over the low gravity values. Morgan et al (2000) reported low seismic velocities, which may indicate an area of low densities that could be linked to highly fractured rocks. Therefore we decided to split the breccias formation into two units: bunte and suevites, which associated different density contrasts.…”

Section: Methodsmentioning

confidence: 97%

Three-dimensional gravity modeling of Chicxulub Crater structure, constrained with marine seismic data and land boreholes

2013

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We present a three-dimensional multi-formation inversion model for the gravity anomaly over Chicxulub Crater, constrained with available marine seismic data and land boreholes. We used eight formations or rock units as initial model, corresponding to: sea water, Paleogene sediments, suevitic and bunte breccias, melt, Cretaceous carbonates and upper and lower crust. The model response fits 91.5% of the gravity data. Bottom topography and thickness plots for every formation are shown, as well as vertical cross-sections for the 3-D model. The resulting 3-D model shows slightly circular features at crater bottom topography, which are more prominent at the base of the breccias unit. These features are interpreted as normal faults oriented towards the crater center, revealing a circular graben-like structure, whose gravity response correlates with the rings observed in the horizontal gravity gradient. At the center of the model is the central uplift of upper and lower crust, with the top covered by an irregular melt layer. Top of the upper crust shows two protuberances that can be correlated with the two positive peaks of the gravity anomaly. Top of Cretaceous seems to influence most of the response to the gravity anomaly, associated with a high density contrast.

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Ejecta thickness and structural rim uplift measurements of Martian impact craters: Implications for the rim formation of complex impact craters

2016

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The elevated rim in simple craters results from the structural uplift of preimpact target rocks and the deposition of a coherent proximal ejecta blanket at the outer edge of the transient cavity. Given the considerable, widening of the transient cavity during crater modification and ejecta thickness distributions, the cause of elevated crater rims in complex craters is less obvious. The thick, proximal ejecta in complex impact craters is deposited well inside the final crater rim and target thickening should rapidly diminish with increasing distance from the transient cavity rim. Our study of 10 complex Martian impact craters ranging from 8.2 to 53.0 km in diameter demonstrates that the mean structural rim uplift at the final crater rim makes 81% of the total rim elevation, while the mean ejecta thickness contributes 19%. Thus, the structural rim uplift seems to be the dominant factor to build up the total amount of the raised crater rim of complex craters. To measure the widening of the transient cavity during modification and the distance between the rim of the final crater and that of the transient cavity, we constructed balanced cross section restorations to estimate the transient cavity of nine complex Martian impact craters. The final crater radii are~1.38-1.87 times the transient cavity radii. We propose that target uplift at the position of the final crater rim was established during the excavation stage.

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Peak-ring formation in large impact craters: geophysical constraints from Chicxulub

Cited by 119 publications

References 14 publications

Volume 364: Chicxulub: Drilling the K-Pg Impact Crater

Volume 364: Chicxulub: Drilling the K-Pg Impact Crater

Three-dimensional gravity modeling of Chicxulub Crater structure, constrained with marine seismic data and land boreholes

Ejecta thickness and structural rim uplift measurements of Martian impact craters: Implications for the rim formation of complex impact craters

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