C. Yeh, Dallas H. Abbott, M. H. Anders and D. Breger

What is the age and origin of the spherule bearing layer in some Ross Sea cores? (in AGU 2012 fall meeting )

American Geophysical Union Fall Meeting(December 2012), 2012

Index Terms/Descriptors: Antarctica; continental shelf; Deep Sea Drilling Project; DSDP Site 274; Leg 28; marine sediments; Ross Sea; sediments; Southern Ocean

Latitude & LongitudeS68°59'49'' - S68°59'49'' and E173°25'38'' - E173°25'38''


L. P. Khyranina (1985) was the first to suggest that there were two structures present on the Antarctic continental shelf beneath the Ross Sea. One was the approximately 100 km Bowers impact crater candidate. However, there was no solid evidence that proved an extraterrestrial impact produced the Bowers structure. Debate has ensued for decades on whether the Bowers structure was an impact crater. Now we have come close to finding an answer. We used core samples taken near the crater and sieved into four size fractions (>250, >125, >63, >38 mu m). Impact ejecta candidates were then picked from cores ELT 32-08, ELT 32-03, ELT 32-43, ELT 32-06, DSDP 273, DSDP 274, and NPB 95-01 39KC and were analyzed for chemical composition and physical features. All but DSDP site 274 contain pure SiO2 glasses that resemble tektites. We also found candidates for flow textured impact glass and shocked quartz. This led us to conclude that the origin of the spherule-bearing layer was from an impact. With the use of dated core NBP 95-01 39KC, we have constrained the age to lie between 7,305+ or -80 BP and 11,150+ or -95 BP (corrected radiocarbon ages) (Cunningham et al., 1999).