Do Laminated Sediment-Gravity-Flow Deposits on the Antarctic Peninsula Continental Shelf Record Ice Sheet Grounding Events?
Barker and Camerlenghi (2002) proposed that drifts on the continental rise of the Antarctic Peninsula may record a high-resolution record of ice-sheet expansions on the adjacent continental shelf. In their view, laminated sediments were deposited during glacial periods, whereas during interglacial periods, sediment supply to drifts was negligible. As a consequence of low sediment supply, the tops of laminated sequences were bioturbated. Therefore, a bioturbated-laiminated couplet should represent a complete glacial cycle. Bioturbated and laminated (B-L) sediment couplets were compiled from cores at two drift sites obtained from Ocean Drilling Program (ODP) Leg 178 Sites 1095, 1096, and 1101. If the hypothesis is correct, then coeval sections should have the same number of B-L couplets given that glacial advance to the shelf edge is a major regional event. The comparison shows that the number of couplets in coeval section is similar for only 14% of the sections evaluated. The number of B-L couplets was also compared to the number of peak oscillations on ?18O records. The comparison of the B-L couplets to oscillations on the ?18O record shows that the two cycles agree for only 32% of the sections compared. The pervasive mismatch in the number of B-L couplets with coeval sections indicates that the couplets on the drifts cannot be simply associated with regional advance and retreat of grounded ice to the outer continental shelf of the Antarctic Peninsula. Bioturbation on the drifts and/or sediment delivery to the drift lacked sufficient spatial continuity to create a consistent record of glacial cycles. The mismatch with cycles on ?18O records likewise shows that B-L couplets on the Antarctic Peninsula cannot be directly related to global-scale ice-volume changes.
Advisor:Philip J. Bart; Brooks Ellwood; Ray Ferrell Jr.
School:Louisiana State University in Shreveport
School Location:USA - Louisiana
Source Type:Master's Thesis
Date of Publication:04/14/2009