Impact‐Induced Porosity and Microfracturing at the Chicxulub Impact Structure

Catalina.Gebhardt [ at ]


Porosity and its distribution in impact craters has an important effect on the petrophysicalproperties of impactites: seismic wave speeds and reflectivity, rock permeability, strength, and density.These properties are important for the identification of potential craters and the understanding of theprocess and consequences of cratering. The Chicxulub impact structure, recently drilled by the jointInternational Ocean Discovery Program and International Continental scientific Drilling ProgramExpedition 364, provides a unique opportunity to compare direct observations of impactites withgeophysical observations and models. Here, we combine small-scale petrographic and petrophysicalmeasurements with larger-scale geophysical measurements and numerical simulations of the Chicxulubimpact structure. Our aim is to assess the cause of unusually high porosities within the Chicxulubpeak ring and the capability of numerical impact simulations to predict the gravity signature and thedistribution and texture of porosity within craters. We show that high porosities within the Chicxulub peakring are primarily caused by shock-induced microfracturing. These fractures have preferred orientations,which can be predicted by considering the orientations of principal stresses during shock, and subsequentdeformation during peak ring formation. Our results demonstrate that numerical impact simulations,implementing the Dynamic Collapse Model of peak ring formation, can accurately predict the distributionand orientation of impact-induced microfractures in large craters, which plays an important role in thegeophysical signature of impact structures.

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DOI 10.1029/2019JE005929

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Rae, A. S. P. , Collins, G. S. , Morgan, J. V. , Salge, T. , Christeson, G. L. , Leung, J. , Lofi, J. , Gulick, S. P. S. , Poelchau, M. , Riller, U. , Gebhardt, C. , Grieve, R. A. F. and Osinski, G. R. (2019): Impact‐Induced Porosity and Microfracturing at the Chicxulub Impact Structure , Journal of Geophysical Research: Planets, 124 (7), pp. 1960-1978 . doi: 10.1029/2019JE005929



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