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Comparison of clast frequency and size in the resurge deposits at the Chesapeake Bay impact structure (Eyreville and Langley cores): Clues to the resurge process

Kapitel i bok
Författare Jens Ormö
Erik Sturkell
Wright J. Horton Jr
David S. Powars
Lucy E. Edwards
Publicerad i Geological Society of America Special Papers, 458
Sidor 617–632
ISBN 978-0-8137-2458-4
Publiceringsår 2009
Publicerad vid Institutionen för geovetenskaper
Sidor 617–632
Språk en
Ämneskategorier Geovetenskap och miljövetenskap, Annan geovetenskap och miljövetenskap

Sammanfattning

Collapse and inward slumping of unconsolidated sedimentary strata expanded the Chesapeake Bay impact structure far beyond its central basement crater. During crater collapse, sediment-loaded water surged back to fill the crater. Here, we analyze clast frequency and granulometry of these resurge deposits in one core hole from the outermost part of the collapsed zone (i.e., Langley) as well as a core hole from the moat of the basement crater (i.e., Eyreville A). Comparisons of clast provenance and flow dynamics show that at both locations, there is a clear change in clast frequency and size between a lower unit, which we interpret to be dominated by slumped material, and an upper, water-transported unit, i.e., resurge deposit. The contribution of material to the resurge deposit was primarily controlled by stripping and erosion. This includes entrainment of fallback ejecta and sediments eroded from the surrounding seafloor, found to be dominant at Langley, and slumped material that covered the annular trough and basement crater, found to be dominant at Eyreville. Eyreville shows a higher content of crystalline clasts than Langley. There is equivocal evidence for an anti-resurge from a collapsing central water plume or, alternatively, a second resurge pulse, as well as a transition into oscillating resurge. The resurge material shows more of a debris-flow–like transport compared to resurge deposits at some other marine target craters, where the ratio of sediment to water has been relatively low. This result is likely a consequence of the combination of easily disaggregated host sediments and a relatively shallow target water depth.

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