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| 1.
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荒木, 祐二 ; 長岡, 一樹 ; 塚脇, 真二 ; Araki, Yuji ; Nagaoka, Kazuki ; Tsukawaki, Shinji
概要:
The Noto Peninsula, situated in an intermediate-temperate forest region in the north of Japan, was designated as an area containing .. Globally Important Agricultural Heritage Systems (GIAHS)" by the Food and Agricultural Organization
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(FAQ) of the United Nations (UN) in 2011. Nonetheless, despite this status, artificial forests on the peninsula are being abandoned and suffer from poor undergrowth vegetation. Therefore there are concerns that the forests are losing their original functions such as the development of water catchment areas and the prevention of surface soil erosion. In order to make a contribution to sustainable artificial forestry management, this study aimed to clarify the relationship between undergrowth vegetation and the topography in the artificial forests of the Noto Peninsula. Undergrowth vegetation was investigated using phytosociological methods in 27 randomly set 100m2 quadrats in September and October 2015. As a result, the undergrowth vegetation in an artificial forest of the Noto Peninsula was classified into three vegetation types: (I) a high-altitude area type, (2) a low-altitude area in the peninsula's northern outer region (.. sotoura") type, and (3) a low-altitude area in the peninsula's southern inner region (.. uchiura") type. The differences in species composition between the vegetation types is mainly defined by the sea level, secondary to have been located at a position facing the seaside.
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| 2.
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Tsukawaki, Shinji ; Okawara, Masafumi ; Lao, Kim-Leang ; Tada, Motohiko
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カンボジア中部に位置するトンレサップ湖は, 雨季と乾季とでその冠水面積が3倍以上にも変化し, 季節的水位変動に支配された特異な堆積作用の存在が予想される。また, 同湖はインドシナ半島最大の湖であり, 湖底堆積物には同半島における地域的気候・
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環境変動が記録されている可能性がある。そこで, トンレサップ湖研究の第一段階として, 湖の北部, 同湖とメコン河とを連絡し雨季に同湖へと逆流するトンレサップ川, ならびに湖の周辺に分布する沖積層の堆積物組成から同湖における堆積作用の予察的検討を行なった。 その結果, 粘土鉱物組成にもとづき, トンレサップ湖北部の湖底堆積物は, 沖積層ならびにメコン河水系に分布する地質岩体の双方を起源とし, 堆積物はおもに雨季に湖に流入することが判明した。また, 同湖での存在が確認された海洋性レリックから, 過去の高海水準期における同湖の南シナ海との連絡が推定された。さらに, 湖底堆積物に雨季と乾季との季節変化記録の可能性が示された。 Lake Tonle Sap, the largest lake in the Indochina Peninsula, lies in central Cambodia. Unique sedimentation is expected in the lake due to drastic changes in its water area between the rainy and dry seasons. As the first step to examine the sedimentary processes of the lake, bottom sediments of the lake and the Tonle Sap River, and surface soils of alluvial deposits were collected and examined in order to reveal the origin of the lake bottom sediments. As the results it becomes clear that clay minerals in the bottom sediments of the northern part of Lake Tonle Sap are derived both from surface soils on the alluvial deposits around the lake, and metamorphic and granitic rock bodies lying in the Mekong River basin. The latter is transported, as suspended sediments by backward current in the rainy season, into the lake from the Tonle Sap River. The presence of marine creatures in bottom sediments of the lake suggests that the lake was closely connected with the sea during the last sea-level high stand. Furthermore, there is a strong possibili ty that annual changes due to alternating rainy and dry seasons will be recorded in the lake bottom sediments over the long geological period.
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| 3.
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Tamura, Toru ; Saito, Yoshiki ; Sieng, Sotham ; Ben, Bunnarin ; Kong, Meng ; Choup, Sokuntheara ; Tsukawaki, Shinji
概要:
The depositional facies and radiocarbon ages of a long Holocene sediment core (KS) from Cambodia are reported here to cl
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arify the sedimentary environments of the Mekong River delta system at the time of Holocene maximum flooding by the sea. The 30.7-m-long KS core, from the upper Mekong River lowland about 20 km southeast of Phnom Penh, penetrated five depositional facies, A to E in ascending order. Facies A is cross-laminated fluvial sand. Facies B is laminated, very fine sand with mud drapes.Facies C to E are salt marsh, flood-plain and natural-levee deposits, characterized by a succession of peat, organic clay, and reddish brown silt. Facies B dates to 9.0 to 7.5 ka and is interpreted as aggradational tidal deposits, 16.5 m thick, deposited during a rapid rise of sea level; these deposits became overlain by an accumulation of salt marsh and flood-plain deposits during the subsequent period of slowly rising and then falling sea level. The maximum flooding surface lies in the Facies B interval. The presence of tidal deposits implies that the core site, about 230 km inland from the present river mouth, was near the shoreline and experienced strong tidal influences during the early Holocene.© 2006 Elsevier Ltd. All rights reserved.
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Sugawara, Daisuke ; Minoura, Koji ; Nemoto, Naoki ; Tsukawaki, Shinji ; Goto, Kazuhisa ; Imamura, Fumihiko
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Micropaleontological analysis of nearshore to offshore sediments recovered from the southwestern coast of Thailand was p
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erformed to clarify the submarine processes of sediment transport and deposition during the 2004 Indian Ocean tsunami. The distribution pattern of benthic foraminifers showed seaward migration after the tsunami event. Agglutinated foraminifers, which are characteristic of an intertidal brackish environment, were identified in the post-tsunami samples from foreshore to offshore zones. These suggest that sediments originally distributed in foreshore to nearshore zones were transported offshore due to the tsunami backwash. On the other hand, the distribution pattern of planktonic and benthic species living in offshore zones showed slight evidence of landward migration by the tsunami. This suggests that landward redistribution of sediments by the tsunami run-up did not occur in the offshore seafloor of the study area. Our results and a review of previous studies provide an interpretation of submarine sedimentation by tsunamis. It is possible that tsunami backwashes induce sediment flows that transport a large amount of coastal materials seaward. Thus, traces of paleotsunami backwashes can be identified in offshore sedimentary environments as the accumulation of allochthonous materials. This can be recognized as changes in benthic foraminiferal assemblages. © 2009 The Authors Journal compilation © 2009 Blackwell Publishing Asia Pty Ltd.
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| 5.
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Tsukawaki, Shinji ; Asano, Izumi ; Kamiya, Takahiro
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南タイのクロントムならびにサトゥン両地域に分布するマングローブ林周辺水域での堆積作用の解明を目的とし,1996年12月および1997年8月にクロントム地域から56ならびにサトゥン地域から53の水底堆積物をそれぞれ採取し,堆積物の組成およびそ
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の水平分布・変化を調べた。また,内部水域にへの海水の到達範囲の確認および全域にわたる水底地形の把握のため,表層水の水質調査および測深を採泥と並行して行った。クロントム地域の水底には全域にわたって砂質堆積物が卓越する。これに対してサトゥン地域ではおもに泥質堆積物が分布する。これは両地域における砕屑性堆積物の主供給源となる後背地の地質をそれぞれ反映するものと考えられる。また,両地域の堆積物に含まれる砕屑性堆積物が主として両地域の背後に分布する古～中生界に由来するのに対し,底生有孔虫や介形虫などの生物源堆積物は,おもにマラッカ海峡などの海底を起源とするものといえる。これに加え,いずれの堆積物にも豊富に含まれる炭粒子は,マングローブ林内または周辺地域の村落や炭焼窯から流出したものと判断される。このように,これらの堆積物はいずれも生産地が特定されるものであり,両調査地ともに生産地から離れるにつれて,これらの堆積物の堆積物全体に対する含有量の減少や細粒化が追跡される。したがって,これらの堆積物の粒度変化や含有量の変化に加え,両地域における陸上・水底地形の特徴にもとづき,両地域における堆積物の移動過程・経路が推定される。
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| 6.
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Okawara, Masafumi ; Tsukawaki, Shinji
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金沢大学環日本海域環境研究センターエコテクノロジー研究部門
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Tsukawaki, Shinji ; Domitsu, Hanako ; Fukaya, Yasuyuki ; Furuuchi, Masami ; Kamada, Kotaro ; Kamiya, Takahiro ; Kumakiri, Michiko ; Murase, Takahiro ; Sakano, Takeo ; Seikai, Tadahisa ; Takahashi, Yoshie
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Tsukawaki, Shinji ; Ozawa, Hirokazu ; Ooji, Akihito
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Tsukawaki, Shinji ; Domitsu, Hanako ; Oda, Motoyoshi
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Tsukawaki, Shinji
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