高レベル放射性廃棄物の地層処分の安全評価に資するため, 日本原子力研究開発機構では, 広域を対象とした長期的な地下水流動評価手法の整備を進めている. 本研究はその一環として, 将来的な寒冷気候の到来に伴った地下水流動状況を予測評価するために, 凍土が形成されていた可能性の高い北海道幌延地域を対象として, 空中写真と高精度 DEM (数値標高モデル) を使用した地形解析を行い, 最終氷期からへの地下水流動の変化要因について検討した. その結果, 幌延地域では氷期に周氷河性の平滑斜面が広く発達し, に入ると降水量の増大に伴ってこの平滑斜面が侵食され, 相対的に急傾斜の斜面が形成されたこと, およびこのの侵食作用は対象地域内で一様ではなく, 地質の違いによって明瞭な差があることがわかった. すなわち, 勇知層や更別層では平滑斜面の60％以上がすでに侵食され, 一部では谷の切り合いにより稜線高度が低下していた. 一方, 声問層や稚内層では水系密度が低く, 平滑斜面の40％未満を侵食するに留まっていた. また, に形成された谷は, 声問層以上の比較的浅い谷と稚内層以下の比較的深い谷とに分類できることがわかった. これらに加え, 対象地域の北部と南部での河床高度の変化の違い等について検討した結果, 最終氷期からへの地下水流動の変化要因として①永久凍土の消滅, ②本流河床標高の上昇, ③降水量の増加が重要であると考えられる.

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バイカル湖堆積物に残された光合成色素とその誘導体の分布から、過去数万年から数百万年にわたる、湖内の植物プランクトン組成の変動を推定した。以降を代表する堆積物については、クロロフィル誘導体の他、カロチノイド類がこのために利用できた。最終氷期以前に対応する堆積物中に残存する光合成色素の大部分は、植物プランクトンが動物プランクトンに捕食されて生成するステリルクロリンエステルであるが、これを使って植物プランクトン組成の変動を推定できた。

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香川県綾歌郡綾川町の綾川中流域で採取した8mのボーリングコアを岩相に基づいて下位より9層（No. 9～No. 1）に区分し，年代測定，花粉分析を行った．年代測定結果から，コア深度8.00～3.55mは上部更新統，コア深度3.55mより上部は完新統と判明した．花粉分析結果から，最終氷期中期はQuercus subgen. Lepidobalanus（コナラ属コナラ亜属）を主とする落葉広葉樹林が分布する冷涼な環境が，前期はQuercus subgen. Cyclobalanopsis（コナラ属アカガシ亜属）を含む落葉広葉樹林主体のやや冷涼な環境が，そして後期には温帯針葉樹を含むCyclobalanopsis優占の照葉樹林が分布する温暖な環境が推定できた．この傾向は既存の瀬戸内地域における古植生研究の結果とおおむね一致する．この地域の特徴として，後期にはCastanopsis（シイ属）がほとんど産出しない．これは，この地域の試料採取上流域からのCastanopsis供給が少なく，瀬戸内海地域の中でも年間降水量が1,200mm以下と少ない乾燥した地域であるためと考えられる．

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モンゴル・フブスグル湖のグラビティコア中の有機成分により，最終氷期からにおけるユーラシア大陸北東部における環境変動を推定した．全有機炭素濃度は最終氷期(約0.2%）からにかけて著しく増大し，気候最良期には約6％に達した．バイオマーカーの変遷より氷期には湖岸に草本植物が少し分布していたが，には生物生産量が増加するとともに高木植物が繁茂してきたと考えられる．

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Coral reefs are related to all the factors of the predicted global changes for the next century : CO₂ increase, global warming and sea-level rise. The analysis and modeling of postglacial reef responses to these changes with a time scale of 10³ years provide ground truth information as to the possible responses of reefs to the future changes. The sea-level rise might bring about submergence of reefs. The threshold rate is 4 m/1, 000 years : if the sea-level rise over 40 cm occurs in the next century, reef surface will not keep up with the rising sea. Rise in sea surface temperature might cause bleaching of corals in the tropical region. On the other hand, the distribution area of reef corals was expanded at the hypsithermal time in the subtropical region such as Japan. Calcium carbonate deposition in coral reefs releases CO₂ into the atmosphere. The postglacial CO₂ increase did not match the time of reef calcium carbonate deposition. This might show the effect of photosynthetic CO₂ fixation which occurs simultaneously in reefs. Postglacial records show that reef responses to global changes are not simple ones.

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Calcium carbonate deposition in the ocean results in a release of CO₂ to the atmosphere. Based on this process, a "coral reef hypothesis" was proposed to explain postglacial CO₂ increase as a result of reef growth. The model assumed that if twice the mass of atmospheric carbon (2 ACM) were deposited into coral reefs between 15,000 and 10,000 years B. P., the accompanying release of CO₂ would account for 40 ppm increase of the atmospheric CO₂. In this paper, calcium carbonate deposition rates into postglacial reefs with a time scale of 1000 years is calculated based on shallow core researches to test the hypothesis. The total reef mass is estimated to be 2 ACM. Calcium carbonate deposition rates of postglacial reefs attained their maximum between 5000 and 6000 years B. P. with a rate of 0.45 ACM for 1000 years. This major deposition phase does not match the period of observed CO₂ increase in the atmosphere. This discrepancy is not in agreement with the "coral reef hypothesis" .

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In the central part of the Ryukyu Islands, especially at Takara I., Yoron I., and Iheya-lzena Is., the post-glacial sea level is discussed by means of considering the beaches. In the coral reef coasts, the post-glacial sea level higher than at present, may be testified by (1) the formation of red soil in the sediments, (2) terraces and beaches, (3) beach ridges and recent dunes, (4) notches and caves, (5) beach rocks, (6) the limestone filling up the fissures, (7) the reef under the negro heads and (8) the lowest knick point in the streams, etc. If these are considered in relation to C-14 dating, the period of the sea level will be clearer. In this paper terraces and benches were mainly discussed in addition to the reef under negro heads. In the central part of the Ryukyu Islands the post-glacial terraces and benches may be safely classified roughly into (1) Kikai-jima type, (2) Yoron-jima type, and (3) Izena-Yanoshita-jima type. Kikai-jima type has the characteristics of the broad terraces often more than I km in width, of the height of more than 5 - 6 m at the highest terraces, and of being unable to distinguish the benches. But, Takara-jima subtype shows less than 3 m in height, thin sand and gravel bed, and often benches at high tide level or mean tide level. Yoron-jima type has the broad reef at present sea level which is often more than 1 km in width. Former shoreline can be identified by beach rocks and notches, but there are no distinct benches higher than high tide level. Yanoshita-jima type which is the intermediate type between Kikai-jima type and Yoron-jima type, is the characterized by broad and flat benches, and former notches. In the case that the limestone is not sufficiently consolidated, the bedding-plane is weak and torn off like a storm bench. This may fittingly be called Okinoerabu-type. It is estimated by the distribution of beach rocks and double notches that the post-glacial high sea stand in Yoron-jima attained to 2 - 3 m in height. At that time the barrier reef was situated in the inner part where we can see minute pedestals at present. But it must be noticed that the surface of flat topped minute pedestals do not indicate the sea level then, because the benches have been lowered by erosion since the time of formation. 6 m-bench represented at Yoron-jima, showing incomplete distribution and shape, and overlying red soils, seems to be formed before the last glacial period. It cannot be considered also that 3 m bench was formed at the post-glacial period, because the distribution and shape of benches is very incomplete, but it has been deformed to a storm bench. The reef flat covered with the negro heads would have been relieved of the erosion. Accordingly in the most desirable case, it has reserved the initial reef surface exactly. This will Simultaneously show that the raised reef be lowered in parallel with the former surface as time goes on' Therefore the former sea level cannot be identified directly with the present geomorphological surface' The conclusion of this paper is that the post-glacial high Sea stand attained a few meter higher that at present in the central part of Ryukyu Islands.

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The aims of the symposium “Termination of Last Glaciation and the Formation and Development of Jomon culture in Japan” are to clarify (1) what changes have occurred in natural environments in and around the Japanese Islands from the Last Glacial Maximum to the Postglacial periods, (2) what changes have occurred from Late Paleolithic culture to Jomon culture in terms of the relationship between natural and cultural environments, in paticular changes in coastal and land ecosystems and ways of human life, and (3) how and when the Jomon culture was established in terms of natural environmental changes.
The symposium consisted of three different parts: (1) Last Glacial Maximum (the age of upper Paleolithic culture, 20-15ka), (2) a transition period from Late Glacial to Postglacial (the age of formation of Jomon culture, 15-10ka), and (3) Postglacial period (the age of the development of Jomon culture, after 10ka). The topics were presented by three speakers for each part from the viewpoints of geology, paleoecology, pedology, and archeology.
The topics of presentations in the symposium are the following: Upper Paleolithic culture in Japan and East Asia (Masao Ambiru); Spatial distribution of the vegetation around the Last Glacial Maximum in Japan (Mutsuhiko Minaki); Paleoenvironmental changes of the Japan Sea since the Last Glacial period (Ryuji Tada); A land ecosystem in the transition to the Jomon age (Sei-ichiro Tsuji); The formation of Jomon culture in the Southern and Northern parts of Japanese Islands (Michio Okamura); Soil formation and the environmental change (Kan-ichi Sakagami); Development of Jomon villages (Yasuhiro Okada); Forest vegetation and utilization of wood during the Jomon period in Japan (Mitsuo Suzuki and Shuichi Noshiro), and Jomon agriculture: retrieval of evidence (Masakazu Yoshizaki). The discussions in the symposium have focused on the relationship between the changes in natural environments and ways of human life, in particular the change of land ecosystems and the utilization of natural resources.
The state of the art in studies of the natural environmental changes from the termination of the Last Glacial to the Postglacial and their relations to the regional development from the upper paleolithic culture to the Jomon culture in Japan are reviewed from various viewpoints, and future tasks of research are presented.

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The following differences can be recognized world-widely between the last glacial and postglacial periods. In the last glacial period, 1) δ¹³C value of benthic foraminiferal test was 0.5‰ smaller, 2) cadmium and calcium ratio of benthic foraminiferal test was about 20% higher, 3) atmospheric CO₂ content was about two-third, and 4) large amount of dust had accumulated in polar region. And also 5) calcium carbonate preservation spike had occurred during the transitional period from the last glacial to postglacial. The oceanic environmental change which can systematically explain these differences is discussed in detail.

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最近のの海面変動の研究については, 杉村 (1977), 森脇 (1978), 太田ほか (1982), KIDSON (1982) などの手頃な総説があり, いまさらあらためてこの種の解説を書く必要もないくらいであるが, ここでは今まであまり取り上げられなかった問題を含め所見を述べることにする。

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