The geochemical analyses of the lower Neogene marine argillaceous rocks from central-Northeast Sarawak, Malaysia, gave the following information on their sedimentary environments. They were mostly derived from the granitic provenance without any indication of mafic to ultramafic components. Generally higher horizons are more enriched in exposed weathered materials resulted from the uplift of the hinterland. Concurrently, the source of the detritus shows recycling nature, suggesting the deformation of the forearc basin during the middle Paleogene time. As for their source-rock potential of the hydrocarbon resources, the bottom water conditions during their deposition seem to have kept rather oxygenated, while the frequent anoxizations are also recognized. These sediments seem to have been deposited in a near shore shallow open ocean situation where the terrestrial organic materials were accumulated. Although the source rock potential is poor due to the post-depositional oxidation, some anoxic event may be developed somewhere onshore to form rather good source rock facies.

抄録全体を表示

In this paper are shown the results of the heavy mineral analysis of ice-rafted sand fractions of undisturbed surface sediments collected from several gravity cores in and around the Ross Sea shelf area during the TH91 and TH92 Antarctic research cruises by Technology Research Center, Japan National Oil Corporation, using R/V Hakurei-maru. The areal distribution pattern of the frequency of each heavy mineral suggests the existence of at least two petrographic provinces, i. e. western and central-eastern areas. Especially, olivine and clinopyroxene with titanaugite, which were probably supplied from the late Quaternary McMurdo alkaline basaltic rocks fringing the eastern margin of the Victoria Land, are exclusively or dominantly distributed in the western area of the Ross Sea. This results support the northward movement of icebergs nearly parallel to the east coast of the Victoria Land at least in the western part of the Ross Sea shelf area.

抄録全体を表示

The size of ancient seaway can be estimated from paleo-wave conditions reconstructed from wave ripples and other sedimentary rock records. Possible combinations of wind speed, fetch and length of wave decay are obtained for a given paleo-wave condition by making a reverse use of wave forecasting and swell forecasting methods. This method is unique in that it pays regard to the process of wave decay. The calculated possible fetches fall into a certain range. The maximum value of calculated fetch is that for fully developed waves having no chance to decay. The range of fetches can be reduced using some sedimentological criteria, e. g. storm/fair weather sedimentation. Reference to present-day ocean waves further provides a basis for omitting unrealistic fetch lengths. Estimated fetch and decay lengths place some constraint on the minimum size of the paleo-seaway.

抄録全体を表示

Major and trace element concentrations of 38 shales and sandstones from Northern Shimanto belt in southwestern Shikoku were determined by X-ray fluorescence. SiO₂ contents range in 56-69wt% for shale, and in 67-78 wt% for sandstone. TiO₂, Al₂O₃, Fe₂O₃, MgO, K₂O, and Rb decrease with increasing SiO₂. This chemical trend could be formed by mixing of mafic and clay minerals with quartz. CaO, Na₂O, Sr, and Ba do not show correlation with SiO₂, and scatters of the contents are large. Concentration of these elements may be controlled by mode and composition of feldspars in sedimentary rocks.

抄録全体を表示

Grain-size distributions of the single transport modes, after sand transport downstream from the brink of an experimental microdelta, are neither Gaussian nor log-hyperbolic. Instead, the sands transported by suspension downstream of the microdelta derive many of their grain-size attributes from those of the sand fed into the flume at its upstream end. Relationships between the grain-size distributions of individual transport modes and the texture of the “original sand” are best demonstrated by normalizing data to the grain size of the “original sand”. The experimental data suggest that the suspension process does not prefer a peculiar size among the grains which can be suspended; i. e., grains present in the suspended load are represented in the same proportion as in the “original sand”. This result can be reproduced by Rouse's diffusion model.

抄録全体を表示

The study area is situated on the right side of the middle of Sai-river, the southern part of the Northern Fossa Magna region. There are large cliff exposures which consist of an upper Miocine sedimentary rocks, Aoki Formation. The sedimentary environment of these rocks was fan-delta slope in the progradational stage of fan-delta system. Exposures show discordances which concave upward, and large slump structures being followed for about 100m. Discordances are interpreted as slump scars formed by downslope sliding or slumping of fan-delta slope sediments. The large slump structure resulted from a slumping sidewall of scar into scarsurface. In this case, slumping and sliding occuerred frequently on the fan-delta slope. Then, a lot of clust were released down-slope and formed lobe shaped sediments. This is characteristic of fan-delta slope sedimentation during the progradational stage and may reflect hightstand of the relative sea-level.

抄録全体を表示

北部九州, 津屋崎海岸の渡半島南端には礫浜がよく発達している. その一部は幅100m, 延長約500mの礫堆をなし, 海岸から斜めに沖合へ突き出している. その礫堆の背後は含礫砂質プールを形成している. このプール砂地には海草が付着した大礫が散在している. 本研究では海草付着礫の礫径分布, 円磨度, 礫種等を検討し, その堆積学的意義を明らかにした. その結果, この種の礫は礫堆で冬～春季に礫表面に付着, 成長した海草が波浪の強いときに礫とともに“sail effect”で礫堆を越えてプールに運ばれたものであり, パラシュート礫ということができる. このような礫は含礫砂岩の堆積過程を考えるときに重要な示唆を与えるものである.

抄録全体を表示

上部白亜系御船層群は, 九州中軸帯白亜系堆積盆地の一層群で, 陸成・汽水成ならびに浅海成堆積物からなる. 本層群は下位より基底層・下部層・上部層に区分され, 全層厚は1500m以上に達する一海進・海退シーケンスをなす. 本研究では堆積相解析・古流向解析より陸成層の御船層群上部層中の赤色層の堆積学的特徴を記載し, さらに本層群の堆積環境の変遷を明らかにした. 御船層群中には17の堆積相が識別され, それらの堆積相群から8つの堆積環境が推定できる. その堆積環境変遷は, 層群北部域では下位から扇状地・河口・泥質干潟・湖沼と変化するのに対し, 南部域では扇状地末端部・砂質干潟・沖浜・外浜・湖沼と変化することから東に海域が面していた内湾的な地形が考えられる. また赤色層を含む細粒層は, 級化・リップルなどの堆積構造が発達する湖沼成堆積物に比較され, 古流向などから北方へ前進する湖成デルタによって形成されたと考えられる.

抄録全体を表示