Melt Particles in the Chesapeake Bay Impact Structure Eyreville Drill Core – A Progress Report

Introduction: The Chesapeake Bay impact structure, 35 Myr old and 85 km in diameter, is one of the largest and best preserved impact structures on Earth [1]. The structure was drilled in the central part at Eyreville in 2005-2006 during an ICDP-USGS drilling project. Three drill cores (Eyreville A, B, and C), intersecting the impact structure to a total depth of 1766 m, were recovered within the central zone of the structure in the deep crater moat. The crater fill comprises post-impact sediments, sediment clast breccias and sedimentary megablocks (the so-called Exmore breccia beds, interpreted as resurge breccias), a large granitic and a small amphibolitic megablock, gravelly sand, impact breccia (IB; 1397-1551 m; [2]), and granites/pegmatites and mica schists [1]. In the upper part (above ~1474 m) the IB section consists of melt-rich suevite that contains two intervals (5.5 and 1 m thick) of impact melt rock [3]. In the deeper part of the IB section (below 1474 m) melt-poor suevite and polymict lithic impact breccia alternate with large blocks of cataclastic gneiss [2].