Physical rock properties of the Eyreville core, Chesapeake Bay impact structure

Sibylle I. Mayr, Hans Burkhardt, Yuri Popov, Raissa Romushkevich, Dmitry Miklashevskiy, Denis Gorobtsov, Philipp Heidinger, Helmut Wilhelm

Research output: Contribution to journalArticlepeer-review

8 Citations (Scopus)

Abstract

The physical properties of rocks in drill core from impact structures can be used to distinguish individual nonimpact and impact-generated lithologies, and to investigate the effect of the impact process on the target rocks. Here, we present the results of laboratory measurements of porosity, density, velocity, and thermal properties on the densely sampled cores from the Eyreville borehole in the Chesapeake Bay impact structure, USA. With increasing depth, the lithologies encountered (and porosities) are: postimpact sediments (40%-60%), Exmore breccia and sedimentary blocks (27%-44%), a large megablock of granitoids (<1%), suevite and polymict lithic impact breccia (1%-25%), and schist, granite, and pegmatite of the basementderived section (1%-13%). The low bulk densities and thermal properties of the postimpact sediments show a good correlation with the high porosity values. The physical properties within the Exmore bed sequence overall display relatively small variation but are heterogeneous on the core sample scale. Physical properties along the impact-breccia sequence are highly variable on all scales, and they are interpreted to be controlled by the structural arrangement of particles as well as by the highly variable mineral and clast compositions of the samples. The physical properties of the rocks of the lowermost basement-derived section are also heterogeneous and are interpreted as having been influenced by both lithology and overprinting as a result of the impact process. These results are important for further lithological and petrophysical interpretation and for calibrating future geophysical models of the Chesapeake Bay impact structure.

Original languageEnglish
Pages (from-to)137-163
Number of pages27
JournalSpecial Paper of the Geological Society of America
Volume458
DOIs
Publication statusPublished - 2009
Externally publishedYes

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