南米・パタゴニア地域における完新世の氷河変動と近年の氷河変動機構の解明

科学研究費助成事業（科学研究費補助金）研究成果報告書：基盤研究(A)2） 平成10～11年度 課題番号：国10041105はしがき........................................................................................................................V研究組織、研究経費、研究発表............................................................................VIパタゴニア地域概念図..............................................................................................IXパタゴニア・ソレール河谷の完新世の環境変動-氷河を中心として............1北パタゴニア氷原溢流氷河の1995/96-1998/99の変動.........................21北パタゴニア氷原の空撮........................................................................................31パタゴニア・ソレール氷河の表面プロファイルの測量................................41パタゴニア・ソレール氷河における流動観測結果.........................................47パタゴニア・ソレール氷河における歪速度観測結果....................................55氷河モデルにおける底面すべりの重要性..........................................................601998年夏季のソレール氷河における気象条件と熱収支の特徴...............64北パタゴニア氷原・ソレール氷河の水文特性.................................................75パタゴニア・ソレール氷河における氷雪崩の観測.........................................821998年ソレール氷河調査行動表........................................................................90南パタゴニア氷原ティンダル氷河における氷河調査の概要........................93南パタゴニア氷原ティンダル氷河涵養域における雪氷コア堀削............106南パタゴニア氷原ティンダル氷河における気象観測..................................139南パタゴニア氷原ティンダル氷河消耗域の雪氷生物調査..........................168パタゴニア・ペリートモレノ氷河の表面プロファイルの測量および氷河末端の流動とカービングの観測....................................................................................................................191Perito Moreno 氷河からのcalving（氷山分離）観測報告......................195パンタグラフ型アンチトルク機構の試作.........................................................20

Landforms of the Balchenfjella area, the Sør Rondane, East Antarctica

Landforms of Balchenfjella (Balchen Mountain) and nunataks near it in the Sør Rondane, East Antarctica, were described using a geomorphological map compiled from field work and aerial photographic interpretation for Balchenfjella and aerial photographic stereograms for major nunataks. While the nunataks are in general standing out above the general surrounding ice surfaces and many of them show landforms of alpine glacier origin, Balchenfjella is characterized by landforms of areal scouring owing to continental ice-sheet glaciation and most of the area still lies below the surrounding ice surface. In this regard, Balchenfjella is found to be very unique in the Sør Rondane. Distinctive demarcation lines between the surfaces of weathered materials and fresh bedrocks found at the eastern side of the several nunataks and Balchenfjella suggest a recent lowering of the ice-sheet surface by several tens of meters. Wide covers of weathered erratics and/or tills over Balchenfjella indicate that the mountain was once covered by ice tongues spilling and closing in from surrounding sides and ablation was very extensive there. Based on the spatial distribution of weathered materials, the relative deglaciation sequence was inferred for Balchenfjella, finding that the eastern part, although higher, was most recently deglaciated. Schematic sequences of weathering, erosional and depositional processes working after deglaciation and their effects on the exposed surface were tentatively presented and the surface characteristics were listed for parts of Balchenfjella and each nunatak

LANDFORMS OF MT. VECHERNYAYA, NEAR SOVIET MOLODEZHNAYA STATION, EAST ANTARCTICA

The Mt. Vechernyaya (272m above the surrounding sea level) area covers several square kilometers and the exposed bedrock area can be divided into western and eastern sections by an ice/snow body running north-south in the middle. The present landforms of the study area are primarily the results of selective erosion by the ice sheet, which was influenced by geologic factors such as joints, gneissosity and rock types. The joint-controlled linear trends in topography are very evident. Another characteristic of the area is step-like topographies. In the western section, five levels of relatively flat surfaces can be recognized, while in the eastern section, four levels can be distinguished. Steps are interpreted as the results of selective/differential erosion along the old faults, joints and geologic contacts, coupled with different lithologies. Tills are widespread, particularly in the lower area of the eastern section, although the cover is thin. Erratics are relatively small, typically less than 30cm in long axis and usually subangular to subround with relatively fresh appearance. Development of tafoni on erratics is very good, and so is development of sorted patterned grounds (chiefly polygons) on the tills. At present, it appears that periglacial processes such as freeze and thaw, gelifluction and nivation are strongly working in this area

ヒガシ ナンキョク セールロンダーネ サンチ バルヒュン サン ト ソノ シュウヘン ノ ヌナタック ノ チケイ

東南極セールロンダーネ山地の東端に位置するバルヒェン山とその周辺のヌナタックの地形について, バルヒェン山では現地調査と空中写真判読から作成した地形学図を, 主なヌナタックについては空中写真のステレオグラムを使って記載した。ヌナタックは周辺の大陸氷床よりも高くそびえ, その多くはおもに山岳氷河の侵食による起伏の大きい景観を呈しているが, バルヒェン山は大陸氷床の侵食による, 全体に起伏の緩い滑らかな地形である。またバルヒェン山の大部分は周辺の氷床より低く, その地形的な特徴と相まってセールロンダーネ山地では特異な地域となっている。 いくつかのヌナタックとバルヒェン山の東面は, 風化した物質が載る斜面と新鮮な基盤岩の斜面が上下にきれいに分かれており, 最近大陸氷床が数10m低下したことを示している。バルヒェン山では, 風化したerraticsやtillsが広域にわたって新鮮な基盤の上に堆積している。これは, 過去に周辺の大陸氷床から流れ下ってきた氷舌がこの付近で合流し, 消耗したからと考えられる。これらの風化基盤と風化堆積物の分布に基づき解氷過程が推定され, バルヒェン山の西面が標高が低いにもかかわらず一番早く氷から開放され, 東面が標高が高いにもかかわらず一番新しいと判断された。 最後に, 解氷後の風化・侵食・堆積プロセスの作用とそれらによって作られる地形・地表状態について考察し表にまとめた。さらに, バルヒェン山やヌナタックではどのような地形・地表状態が分布するかを表にして, 相対的な新旧が比較できるようにした。Landforms of Balchenfjella (Balchen Mountain) and nunataks near it in the Sør Rondane, East Antarctica, were described using a geomorphological map compiled from field work and aerial photographic interpretation for Balchenfjella and aerial photographic stereograms for major nunataks. While the nunataks are in general standing out above the general surrounding ice surfaces and many of them show landforms of alpine glacier origin, Balchenfjella is characterized by landforms of areal scouring owing to continental ice-sheet glaciation and most of the area still lies below the surrounding ice surface. In this regard, Balchenfjella is found to be very unique in the Sør Rondane. Distinctive demarcation lines between the surfaces of weathered materials and fresh bedrocks found at the eastern side of the several nunataks and Balchenfjella suggest a recent lowering of the ice-sheet surface by several tens of meters. Wide covers of weathered erratics and/or tills over Balchenfjella indicate that the mountain was once covered by ice tongues spilling and closing in from surrounding sides and ablation was very extensive there. Based on the spatial distribution of weathered materials, the relative deglaciation sequence was inferred for Balchenfjella, finding that the eastern part, although higher, was most recently deglaciated. Schematic sequences of weathering, erosional and depositional processes working after deglaciation and their effects on the exposed surface were tentatively presented and the surface characteristics were listed for parts of Balchenfjella and each nunatak

LANDFORMS AROUND MT. RIISER-LARSEN, AMUNDSEN BAY, EAST ANTARCTICA

Landforms recognized in the Mt. Riiser-Larsen (about 1150m above the surrounding sea level) area, Amundsen Bay, Enderby Land, East Antarctica, were described and presented in a geomorphological map compiled from the result of field work and aerial photographic interpretation. Major landforms, primarily of glacial and periglacial origin, include aretes, cirques, free faces, slopes covered with frost-shattered rock fragments, talus and/or tills, moraines at several levels, glacio-fluvial channels and ponds, and sorted patterned grounds (mostly polygons).The till fields are located at several levels. From their locations, lithogical compositions, and the relative degree of development of patterned grounds on them, two levels were recognized to have been laid by the continental ice sheets (C-I and II), while four levels were judged to have been left by alpine glaciers (A-I, II, III and IV). Based on the distribution of these tills, the glacial sequence was inferred, although in a relative sense, as from older to newer, C-I, C-II, A-I, A-II, A-III, and A-IV. At present, it appears that the glaciation is not very active in this area, as three remaining small alpine glaciers appear to have been stagnant or started retreating