| Abstract: | Biostratigraphic analysis of sedimentary breccias and diamictons in the Chesapeake Bay impact structure provides information regarding the timing and processes of late-stage gravitational crater collapse and ocean resurge. Studies of calcareous nannofossil and palynomorph assemblages in the International Continental Scientific Drilling Program (ICDP)–U.S. Geological Survey (USGS) Eyreville A and B cores show the mixed-age, mixed-preservation microfossil assemblages that are typical of deposits from the upper part of the Chesapeake Bay impact structure. Sparse, poorly preserved, possibly thermally altered pollen is present within a gravelly sand interval below the granite slab at 1392 m in Eyreville core B, an interval that is otherwise barren of calcareous nannofossils and dinocysts. Gravitational collapse of water- saturated sediments from the transient crater wall resulted in the deposition of sediment clasts primarily derived from the nonmarine Cretaceous Potomac Formation. Collapse occurred before the arrival of resurge. Low pollen Thermal Alteration Index (TAI) values suggest that these sediments were not thermally altered by contact with the melt sheet. The arrival of resurge sedimentation is identified based on the presence of diamicton zones and stringers rich in glauconite and marine microfossils at 866.7 m. This horizon can be traced across the crater and can be used to identify gravitational collapse versus ocean-resurge sedimentation. Glauconitic quartz sand diamicton dominates the sediments above 618.2 m. Calcareous nannofossil and dino-flagellate data from this interval suggest that the earliest arriving resurge from the west contained little or no Cretaceous marine input, but later resurge pulses mined Cretaceous sediments east of the Watkins core in the annular trough. Additionally, the increased distance traveled by resurge to the central crater in turbulent flow conditions resulted in the disaggregation of Paleogene unconsolidated sediments. As a result, intact Paleogene clasts in Eyreville cores are rare, but clasts of semilithified Potomac Formation silts and clays are common. |
| Genre: | Article |
| ProdID: | 70003464 |
| Citation Author: | Self-Trail, Jean M.; Edwards, Lucy E.; Litwin, Ronald J. |
| Citation Contributing Office: | Eastern Geology and Paleoclimate Science Center |
| Citation Datum: | |
| Citation Day: | |
| Citation Edition: | |
| Citation Editor: | |
| Citation End Page: | 654 |
| Citation Issue: | |
| Citation Keywords: | |
| Citation Language: | English |
| Citation Larger Work Title: | Geological Society of America Special Papers |
| Citation LatN: | |
| Citation LatS: | |
| Citation LonE: | |
| Citation LonW: | |
| Citation Month: | |
| Citation No Pagination: | |
| Citation Number Of Pages: | |
| Citation Online Only Flag: | |
| Citation Phsyical Description: | 22 p. |
| Citation Projection: | |
| Citation Public Comments: | |
| Citation Publisher: | The Geological Society of America |
| Citation Series: | |
| Citation Series Code: | |
| Citation Series Number: | |
| Citation Search Results Text: | Paleontological interpretations of crater processes and infilling of synimpact sediments from the Chesapeake Bay impact structure; 2009; Article; Journal; Geological Society of America Special Papers; Self-Trail, Jean M.; Edwards, Lucy E.; Litwin, Ronald J. |
| Citation Start Page: | 633 |
| Citation Volume: | 458 |
| Citation Year: | 2009 |
| Type: | citation/reference |
| Text: | Paleontological interpretations of crater processes and infilling of synimpact sediments from the Chesapeake Bay impact structure; 2009; Article; Journal; Geological Society of America Special Papers; Self-Trail, Jean M.; Edwards, Lucy E.; Litwin, Ronald J. |
| URL (THUMBNAIL): | http://pubs.er.usgs.gov/thumbnails/outside_thumb.jpg |
| URL (DIGITAL OBJECT IDENTIFIER): | http://dx.doi.org/10.1130/2009.2458(28) |
| Date Other: | Wed, 28 Sep 2011 00:00 -0500 |
| Publisher: | The Geological Society of America |
