The RPI-based high-resolution age models established by Sagnotti et al. The ages of these sequences were determined using relative paleomagnetic intensity (RPI), with biostratigraphic and chemostratigraphic information providing additional age constraints. on seven gravity cores (SED-02, SED-04, SED-06, SED-14, SED-15, SED-16, and SED-17) collected on drift 7 ( Figure 1). Paleomagnetic and mineral magnetic studies were conducted by Sagnotti et al. The SEDANO program collected 17 gravity cores from drift 7 and an additional two cores at drift 4, while BAS recovered 11 piston cores from the drifts located to the NE of drift 7 on cruise JR19 with RRS James Clark Ross.
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During two SEDANO cruises with the R/V OGS-Explora (1995/1997–98), seismic surveys, gravity coring, and moorings with current meters and sediment traps yielded information about the morphology and mechanisms of deposition along the Pacific continental margin. During the 1990s, these drifts were intensely investigated by the SEDANO program (Sediment Drift of the Antarctic Offshore) of the Italian Programma Nazionale di Ricerche in Antartide (PNRA), the British Antarctic Survey (BAS), and by Ocean Drilling Program (ODP) Leg 178. The hatched blue arrow illustrates episodic intrusion of Circumpolar Deep Water onto the shelf. The inset is a schematic of the present-day surface and bottom water circulation along the western margin of the Antarctic Peninsula. Key PointsĬolor-shaded relief bathymetric map of sediment drift 7 off the Antarctic Peninsula Pacific margin with location of SEDANO gravity cores (mentioned in the text) and ODP Leg 178 drill sites.
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Understanding this sediment provenance delivery signature at a wider spatial scale should provide information about ice sheet dynamics in West Antarctica over the last ∼100 kyr. The observed change of magnetic mineralogy in sediments deposited during Heinrich events on drift 7 appears to be related to warming periods, which temporarily modified the normal glacial transport pathways of glaciogenic detritus to and along the continental rise and thus resulted in deposition of sediments with a different provenance. We did not find evidence for diagenetic magnetic iron sulfides as has been previously suggested for these drift deposits. These two forms vary in amount and stratigraphic distribution across the drifts. The titanomagnetite occurs in two magnetic forms: (1) a low-coercivity form similar to laboratory-synthesized titanomagnetite and (2) a high-coercivity form (B cr > 60 mT). Low- and high-temperature magnetic measurements in conjunction with microscopic and mineralogic observations from drifts 4, 5 and 7 indicate that pseudosingle-domain detrital titanomagnetite (partially oxidized and with limited Ti substitution) is the dominant magnetic mineral in the drift sediments. High-resolution magnetic measurements on u channel samples provide detailed age models for three cores collected from drift 7, which document an age of 122 ka for the oldest sediments recovered near the drift crest at site SED-07 and a high sedimentation rate (11 cm/kyr) at site SED-12 located close to the Alexander Channel system. We present results of detailed paleomagnetic investigations on deep-sea cores from sediment drifts located along the Pacific continental margin of the Antarctic Peninsula.