Deutsch, Alexander and Koeberl, Christian (2006): Establishing the link between the Chesapeake Bay impact structure and the North American tektite strewn field; the Sr-Nd isotopic evidence

Leg/Site/Hole:
DSDP 95
DSDP 95 612
Identifier:
2006-069411
georefid

Creator:
Deutsch, Alexander
Westfaelische Wilhelms-Universitaet Muenster, Munster, Federal Republic of Germany
author

Koeberl, Christian
University of Vienna, Austria
author

Identification:
Establishing the link between the Chesapeake Bay impact structure and the North American tektite strewn field; the Sr-Nd isotopic evidence
2006
Meteoritics & Planetary Science
Meteoritical Society, Fayetteville, AR, United States
41
5
689-703
The Chesapeake Bay impact structure, which is about 35 Ma old, has previously been proposed as the possible source crater of the North American tektites (NAT). Here we report major and trace element data as well as the first Sr-Nd isotope data for drill core and outcrop samples of target lithologies, crater fill breccias, and post-impact sediments of the Chesapeake Bay impact structure. The unconsolidated sediments, Cretaceous to middle Eocene in age, have epsilon (sub Sr) (super t = 35.7 Ma) of +54 to +272, and epsilon (sub Nd) (super t = 35.7 Ma) ranging from -6.5 to -10.8; one sample from the granitic basement with a T (super Nd) (sub CHUR) model age of 1.36 Ga yielded an epsilon (sub Sr) (super t = 35.7 Ma) of +188 and an epsilon (sub Nd) (super t = 35.7 Ma) of -5.7. The Exmore breccia (crater fill) can be explained as a mix of the measured target sediments and the granite, plus an as-yet undetermined component. The post-impact sediments of the Chickahominy formation have slightly higher T (super Nd) (sub CHUR) model ages of about 1.55 Ga, indicating a contribution of some older materials. Newly analyzed bediasites have the following isotope parameters: +104 to +119 (epsilon (sub Sr) (super t = 35.7 Ma) ), -5.7 (epsilon (sub Nd) (super t = 35.7 Ma) ), 0.47 Ga (T (super Sr) (sub UR) ), and 1.15 Ga (T (super Nd) (sub CHUR) ), which is in excellent agreement with previously published data for samples of the NAT strewn field. Target rocks with highly radiogenic Sr isotopic composition, as required for explaining the isotopic characteristics of Deep Sea Drilling Project (DSDP) site 612 tektites, were not among the analyzed sample suite. Based on the new isotope data, we exclude any relation between the NA tektites and the Popigai impact crater, although they have identical ages within 2sigma errors. The Chesapeake Bay structure, however, is now clearly constrained as the source crater for the North American tektites, although the present data set obviously does not include all target lithologies that have contributed to the composition of the tektites.
English
Serial
Coverage:Geographic coordinates:
North:37.4600
West:-77.2000East: -76.4400
South:37.1400

Isotope geochemistry; alkali metals; alkaline earth metals; Aquia Formation; Asia; bediasite; Cenozoic; Chesapeake Bay; Chesapeake Bay Structure; Chickahominy Formation; Chickamoniny Formation; Commonwealth of Independent States; Cretaceous; Deep Sea Drilling Project; DSDP Site 612; ejecta; Eocene; Exmore Breccia; impact features; IPOD; isotope ratios; isotopes; Leg 95; Lower Cretaceous; lower Eocene; major elements; mass spectra; Mesozoic; metals; neodymium; North American tektites; Paleogene; Piney Point Formation; Popigay Structure; Potomac Group; radioactive isotopes; rare earths; Rb-87/Sr-86; rubidium; Russian Federation; samarium; Sm-147/Nd-144; spectra; stable isotopes; strewn fields; strontium; target rocks; tektites; Tertiary; thermal ionization mass spectra; trace elements; United States; upper Eocene; X-ray fluorescence spectra;

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