North American tektite debris and impact ejecta from DSDP Site 612

Abstract

Abstract— A layer of tektite glass and shock‐metamorphosed grains found in an upper Eocene section of core 21 from DSDP Site 612 taken on the continental slope off New Jersey may belong to the North American tektite strewn field. However, the Site 612 glasses generally have higher K2O and lower Na2O contents for a given SiO2 content and different Sr and Nd isotopic compositions. In order to better define the layer, a series of samples was taken continuously through the layer at 1 cm intervals. Tektite fragments are in an 8 cm thick layer; microtektites are concentrated in the upper 4 cm, while spherules with “crystalline” textures (microkrystites) are concentrated in the lower half of the layer. Millimeter‐size splash forms are mostly in the lower part of the tektite‐bearing layer. Rock and mineral grains showing evidence of shock metamorphism are abundant in the upper half of the tektite‐bearing layer. Coesite is abundant, and stishovite was found in one rock fragment. The size and abundance of the tektite glass and the abundance of shocked debris indicate that Site 612 is relatively close to the source crater, which may be to the north of Site 612 on the coastal plain or adjacent continental shelf.