Holocene paleoclimatic changes in Maxwell Bay of South Shetland Islands,West Antartica

Estimation of Sediment Accumulation Rate and Sediment Mixing Rate using Excess Lead-210 in the Sea around King George Island, West Antarctica

Distribution and Origin of Clay Minerals in the Soils of the Barton Peninsula, King George Island, West Antarctica

Dispersal of Suspended Particles Matter and Its Glaciomarine Implications at Marian Cove, Antarctica

Theoretical Approaches to the Fossilization of Plant Fragments and Its Application to the Antarctic

1. Based on the paleoclimatic changes during the Holocene in Maxwell Bay, West Antarctica, marine productivity seemed to have been extremely low prior to 4700 yr BP because sea ice permanently covered the surface. As the climate became relatively warm after 4700 yr BP, sea ice in the surface waters has been sporadically melted and thereby marine productivity has increased. The climate would become warm between about 4700 and 3000 yr BP, considering the rapid increase in TOC and BSi. Grounding glaciers seemed to be located near the core sites of Maxwell Bay prior to about 4700 yr BP. As the climate became warm, grounding glaciers have retreated and located at the present site since about 3000 yr BP.

2. Sediment accumulation rate and sediment mixing rate were estimated by the measurement of excess 210Pb in seven sediment cores around King George Island, West Antarctica. Apparent sediment accumulation rates estimated are 1.4 mm/yr in the inner part of the Maxwell Bay, 1.5 - 4.3 mm/yr in Marian Cove, 2.6 mm/yr in Potter Cove, 1.5 mm/yr and 2.0 mm/yr for two cores collected from the northern continental shelf off the King George Island, 0.35 mm/yr and 0.80 mm/yr for the two cores from the northeastern part of the Bransfield Strait. These results show that sediment accumulation rate decreases in order of the Marian and Potter Coves in the Maxwell Bay, innner part in the Maxwell Bay and the northern continental shelf of King George Island, and the northeastern part of the Bransfield Strait respectively.

3. The origin of clay minerals in the soils of the Barton Peninsula of King George Island, West Antarctica, was evaluated from the occurrence of the soils, the distribution patterns of clay and associated minerals, and the microscopic fabrics of the soils by using field survey, X-ray diffraction, thin section petrography, and electron microprobe analysis.

4.Glacier meltwater and suspended sediment discharge in Marian Cove occurs over a brief 3 month period in summer. The vertical hydrographic profiles obtained by CTDT (Conductivity/Temperature/Depth/Transmissivity) measurements at hourly intervals for about 2 days (Jan. 21 to 22, 1998) were examined to describe dispersal of SPM (suspended particulate matter) and oceanographic characters including water column properties under the present glaciomarine setting.

5. Theoretical approaches to the fossilization of the fragmentary plants were made in terms of general processes of fragmentation and fossilization of plants. There were many possibilities for plants to become fragmentary in alive as well as in depositional environments. It seems, a priori, very rare to find fragmentation of modern plants similar to the fragmentary plant fossils. The research of the fragmentary plants fossils will open a new path to understand environments and processes of plant fossilization. The fossil of the plant fragments collected from the Fildes Peninsula, King George Island seems to be carbonized after fragmentation of the plants.

Paleoclimate and paleoceanography occurred in the Northern Hemisphere have been well established through much of the evidences from marine cores from the Arctic Sea and ice cores from the Greenland Ice Cap. During the recent decade, much of paleoclimatic evidences have been obtained from the western Antarctic Peninsula by American and German scientists.

However, there are lack of paleoclimatic informations around the South Shetland Islands, which is further south and is characterized by strong climatic gradients, so that it is enough to reserve signals of untra-paleoclimatic fluctuations during the recent past. Thus, the collection and presentation of evidences of the paleoceanographic and paleoclimatic changes during the mid-to-late Holocene will be valuable for many scientists who is interested in the Antarctic Peninsula.