作者: James V. Browning , Kenneth G. Miller , Peter P. McLaughlin , Lucy E. Edwards , Andrew A. Kulpecz
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摘要: The Eyreville core holes provide the first continuously cored record of postimpact sequences from within deepest part central Chesapeake Bay impact crater. We analyzed upper Eocene to Pliocene sediments A and C for lithology (semiquantitative measurements grain size composition), sequence stratigraphy, chronostratigraphy. Age is based primarily on Sr isotope stratigraphy supplemented by biostratigraphy (dinocysts, nannofossils, planktonic foraminifers); age resolution approximately ±0.5 Ma early Miocene ±1.0 younger older sequences. Eocene-lower are subtle, middle lower more clearly distinguished, Miocene- display a distinct facies pattern recognize two Eocene, Oligocene, nine Miocene, three Pliocene, one Pleistocene correlate them with those in New Jersey Delaware. through strata at changes from: (1) rapidly deposited, extremely fi ne-grained that probably represent deposited deep (>200 m) basin; (2) highly dissected Oligocene (two very thin sequences) (three long hiatus; (3) thick, (43-73 m/Ma), ne-grained, biosiliceous (16.5-14 Ma) section divided into (V5-V3) neritic paleoenvironments; (4) 4.5-Ma-long hiatus (12.8-8.3 Ma); (5) sandy, shelly (8.3-2.0 six shelf shoreface environments; and, last, (6) sandy paralic (~400 ka). cores thus lling impact-generated basin where timing boundaries heavily infl uenced eustasy. © 2009 Geological Society America.