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Herein we document and interpret an absolute chronological dating attempt using geomagnetic paleointensity data from a post-glacial sediment drape on the western Antarctic Peninsula continental shelf. Our results demonstrate that absolute dating can be established in Holocene Antarctic shelf sediments that lack suitable material for radiocarbon dating. Two jumbo piston cores of 10-m length were collected in the Western Bransfield Basin. The cores preserve a strong, stable remanent magnetization and meet the magnetic mineral assemblage criteria recommended for reliable paleointensity analyses. The relative paleomagnetic intensity records were tuned to published absolute and relative paleomagnetic stacks, which yielded a record of the last ∼8500 years for the post-glacial drape. Four tephra layers associated with documented eruptions of nearby Deception Island have been dated at 3.31, 3.73, 4.44, and 6.86 ± 0.07 ka using the geomagnetic paleointensity method. This study establishes the dual role of geomagnetic paleointensity and tephrochronology in marine sediments across both sides of the northern Antarctic Peninsula. 相似文献
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Radiocarbon (14C) dating yields variable and high reservoir and core-top ages for glacimarine sediments around Antarctica. To test the suitability of luminescence as an alternate dating method we investigated the effectiveness of clock zeroing (by daylight) within fine-silt-size siliciclastic sediments from year-long vertical-array sediment traps in Andvord Bay and Brialmont Cove at the Antarctic Peninsula. Both long-bleach and short-bleach multi-aliquot IR-PSL (infrared photon stimulated luminescence) and single-aliquot, post-IR blue-PSL dating tests were conducted. As well, dual-bandwidth-bleaching thermoluminescence (TL) tests were performed on samples from Brialmont Cove. These TL bleaching tests indicate that silt from the middle and bottom traps at this site has had little or no exposure to daylight, but that silt from the top trap has had some exposure. All 24 samples (representing different seasons and different trap depths) exhibit anomalously old apparent ages (12 ka–60 ka) across annual seasons and depths of deposition when either long-bleach multi-aliquot or late-background-subtraction single-aliquot PSL procedures were employed. Thus regional bottom silts would be unsuited for dating by these two luminescence dating approaches. However, a short-bleach multi-aliquot IR-PSL procedure yields the expected zero ages for several samples, a promising result that requires further exploration. 相似文献
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The Antarctic Peninsula is one of the most sensitive regions of Antarctica to climate change. Here, ecological and cryospheric systems respond rapidly to climate fluctuations. A 4.4 m thick laminated diatom ooze deposited during the last deglaciation is examined from a marine sediment core (ODP Site 1098) recovered from Basin I, Palmer Deep, western Antarctic Peninsula. This deglacial laminated interval was deposited directly over a glaciomarine diamict, hence during a globally recognised period of rapid climate change. The ultra‐high‐resolution deglacial record is analysed using SEM backscattered electron imagery and secondary electron imagery. Laminated to thinly bedded orange‐brown diatom ooze (near monogeneric Hyalochaete Chaetoceros spp. resting spores) alternates with blue‐grey terrigenous sediments (open water diatom species). These discrete laminae are interpreted as austral spring and summer signals respectively, with negligible winter deposition. Sub‐seasonal sub‐laminae are observed repeatedly through the summer laminae, suggesting variations in shelf waters throughout the summer. Tidal cycles, high storm intensities and/or intrusion of Circumpolar Deep Water onto the continental shelf introduced conditions which enhanced specific species productivity through the season. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
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Camerlenghi Angelo Domack Eugene Rebesco Michele Gilbert Robert Ishman Scott Leventer Amy Brachfeld Stefanie Drake Allison 《Marine Geophysical Researches》2001,22(5-6):417-443
We present the results of a marine geophysical investigation of the northern Prince Gustav Channel. By comparative analysis of multibeam bathymetric data, single channel seismic reflection profiles, underway chirp sonar data, ADCP current data and sediment coring, we define the main morphological elements of the area. In particular we define the glacial morphogenesis in relation to the excavation of inner shelf basins and troughs along structural discontinuities and lithologic boundaries. We identify streamlined surfaces that testify to the grounding of ice and past ice flow directions. These glacial forms are found only on glacial tills preserved in the deepest part of the basins, while net erosion to bedrock has occurred elsewhere. Since the Last Glacial Maximum (LGM), the relict glacial morphology has been draped by hemipelagic and diatomaceous mud, and bottom currents have played a major role in focusing sedimentation within small depocentres, that we define as contouritic drifts. Based on shallow sediment architecture and supported by direct measurements, we propose that the direction of bottom water flow is from the outer shelf into the Prince Gustav channel as a result of a combination of tidal currents and ice shelf-related thermohaline circulation. 相似文献
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