The principal coring objectives were to sample the crystalline basement rocks, determine the succession of crater-fill deposits, and retrieve samples of interstitial waters from the Exmore breccia. The upper surface of the granodiorite forms a sharp contact with the overlying sedimentary section. We interpret this to be a zone of decollement, the sediments of which were contorted as megablocks from the crater wall slid and slumped along the basement surface.
Bedding is more consistent here than in lower intervals, and bedding angles are somewhat higher.
Sedimentary clasts derived from Cenozoic as well as Cretaceous formations make up the surgeback unit, and millimeter-size clasts of crystalline basement are moderately abundant within the glauconitic quartz sand matrix. The Chesapeake Coring Team - T. Scoff Bruce, Laurel M. Bybell, Thomas M. Cronin, Lucy E. Edwards, Norman 0. Gerald H. Johnson, E. Randolph McFarland, C. Wylie Poag, David S. Powars, James E. Quick, J. Stephen Schindler, Jean M. SelfTrail, Matthew J. Smith, Robert G. Stamm, Robert E. Weems.