PERMAFROST OCCURRENCE AT ICE-FREE GROUND IN JAMES ROSS AND SEYMOUR ISLANDS, ANTARCTIC PENINSULA AREA

• Main Authors: フクダ マサミ, / シモカワ カズオ, タカハシ ノブユキ, ソネ トシオ, Masami FUKUDA, Jorge STRELIN, Kazuo SHIMOKAWA, Nobuyuki TAKAHASHI, Toshio SONE
• Format: Report
• Language: English
• Published: ABSTRACT 1991
• Subjects: Antarctic; The Antarctic; Antarctic Peninsula; Ross Island; Argentina; Seymour; Seymour Island; Croft; Croft Bay; Antarc*; Ice; James Ross Island; permafrost
• Online Access: https://nipr.repo.nii.ac.jp/?action=repository_uri&item_id=2700; http://id.nii.ac.jp/1291/00002700/; https://nipr.repo.nii.ac.jp/?action=repository_action_common_download&item_id=2700&item_no=1&attribute_id=18&file_no=1

The Japan-Argentina joint expedition was established by the support of Grant-in-Aid for Overseas Scientific Research from the Ministry of Education, Science and Culture, Japan. The authors conducted the field survey related to the genesis and occurrence of permafrost in James Ross Island and Seymour Island, in the east of the Antarctic Peninsula, during the 1989-1990 Antarctic summer season. The climatic condition of the area with mean annual temperature of -10℃ is favorable to the existence of permafrost if the ground surface is not overlain by the glaciers for certain periods of time. In James Ross Island, more than 90% of the ground surface is covered with the glaciers and ice-sheets. The ice-free ground is narrowly distributed in the north western region along Croft Bay. In this region, marine terraces at three different levels are observed with the elevations of 32-35m a.s.l. at upper level, 10-17m a.s.l. at middle level and 3-5m at the lowest level. Aiming to obtain the chronological information of terraces, detailed topographic mapping and stratigraphic survey were conducted on-the-spot. According to the results of survey, the glacial till deposited on the subsurface layer of the highest terrace indicates the coverage of glaciers over this terrace. No glacial tills were observed on the surface of both middle and lowest terraces. It implies that the glaciers had retreated before the formations of these lower terraces and the physical conditions were favorable to the development of permafrost. Sea shell specimens collected from the layers constituting the middle terrace indicate that the ground surface of the middle terrace was submerged under the sea level. Once the ground surface submerges under the sea level, the surface of the ground is subjected to the warmer boundary temperature than that enables permafrost to exist. No permafrost develops in the underlying sediments, or a pre-existed permafrost may have diminished under these environments. Then the submerged ground is upheaved above the sea level to ...