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11.
西藏金沙江缝合带西段晚三叠世碰撞作用与沉积响应 总被引：17，自引：4，他引：17
青藏高原是由若干条缝合带和其间所夹的沉积盆地构成,其中晚三叠世北羌塘盆地位于金沙江缝合带南缘,盆地的充填实体显示为南薄北厚,为楔形沉积体;在垂向上,以不整合面为界可将该套充填地层划分为两个构造层序,下部构造层序以复理石建造为特征,上部构造层序以磨拉石建造为特征,具有典型的前陆盆地充填序列;盆地具双物源和双古流向体制,沉降中心和沉积中心具有不一致,显示其为金沙江缝合带南侧的周缘前陆盆地,从而确定了晚三叠世北羌塘前陆盆地与金沙江缝合带的成因关系。在此基础上,结合在金沙江缝合带西段新发现和确定的蛇绿岩的最小年龄和碰撞型花岗岩的年龄,本文根据下部构造层序复理石的年龄、前缘隆起的形成年龄、冲断带隆升成为地貌高地的年龄、下部不整合面的时代和前缘隆起型碳酸岩缓坡的形成时间标定了金沙江缝合带碰撞事件的时代下限,根据上部构造层序磨拉石的年龄、上部不整合面的年龄、花岗岩和构造碎裂岩成为物源的年龄标定了金沙江缝合带碰撞事件的时代上限,表明金沙江缝合带初始碰撞事件为卡尼克期与诺利克期之间,最终碰撞事件介于诺利克期与瑞替克期之间. 相似文献
12.
Biostratigraphy of the lower red shale interval in the Rhenodanubian Flysch Zone of Austria 总被引：2，自引：1，他引：2
In the Rhenodanubian Flysch Zone of Austria, between the Aptian–Albian “Gault Flysch” and the Cenomanian–Turonian Reiselsberg Formation, an interval with predominant red shales (“Untere Bunte Schiefer”) occurs. In the Oberaschau section near Attersee (Upper Austria) a ca. 18-m-thick interval of alternating red and grey shales and marlstones with minor sandstones is present. Thin sandstone intercalations are interpreted as distal turbidites. Dinoflagellate cyst assemblages indicate the Litosphaeridium siphoniphorum Zone. The concurrent presence of Litosphaeridium siphoniphorum and Ovoidinium verrucosum in all samples allows a correlation to the lower part of this zone, thus defining a Late Albian–Early Cenomanian age. Based on foraminifera, the red beds can be assigned to the topmost Rotalipora appenninica Zone and the Rotalipora globotruncanoides Zone due to the presence of small morphotypes of the index taxa. Nannofossils indicate standard zones CC9/UC0 throughout the red interval, defined by the first occurrence of Eiffellithus turriseiffelii, and UC1 above the red shales. Based on these multistratigraphic data, a latest Albian–Early Cenomanian age can be inferred. 相似文献
13.
藏北查桑上三叠统复理石沉积大地构造背景的初步探讨 总被引：10，自引：1，他引：9
藏北羌塘地块的构造性质和构造局是中国地学界长期争论的重要问题。这里人迹罕至,研究程度很低,基础地质资料缺乏。这是有关地质问题得不到解决的根本原因之一。本项研究的首要目的也是为该地区的地质研究提供一份基础资料,羌塘地块腹地查桑地区的上三叠统肖茶上涨且,下部为细碧岩、中基性火山岩、玄武质角砾岩来灰岩和大理岩,上部主要为碎屑岩（复理石）和灰岩,我们在肖茶卡组上部的复理石中采集砂岩、粉砂岩样品,进行主量元 相似文献
14.
Karel Šilhán Rudolf Brázdil Tomáš Pánek Petr Dobrovolný Lucie Kašičková Radim Tolasz Ondřej Turský Marek Václavek 《地球表面变化过程与地形》2011,36(14):1898-1909
Rockfall is an important process in the final sculpturing of escarpments and scree slopes that originate in bedrock landslides in the Flysch Carpathians. The spatio‐temporal characteristics of rockfall activity were studied at four localities representative of old landslides in the highest part of the Czech Flysch Carpathians (Moravskoslezské Beskydy Mountains). Historical activity, chronology, and spatial context of rockfall activity were reconstructed using dendrogeomorphic techniques and rockfall rate index (RR). A total of 1132 increment cores from 283 trees growing in the rockfall transport and accumulation zones enabled the dating of 989 rockfall events. Reconstruction of a 78‐year‐long RR chronology suggests similar rockfall histories and trends at all study sites, indicating the existence of major common factors driving rockfall dynamics in the region. Temporal analysis and correlation of the RR series obtained with monthly mean temperatures, numbers of days with temperature transitions through 0 °C and monthly precipitation totals show that meteorological characteristics have evident but variable influence on rockfall activity. The most important factor is the effect of freeze–thaw cycles throughout the year, supplemented by low temperatures, especially during autumn. The influence of precipitation totals is of lesser importance. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
15.
The first occurrence (FO) of Marthasterites furcatus was correlated with the FOs of other nannofossils, inoceramid bivalves and foraminifers in the Bohemian Cretaceous Basin and Outer Flysch Carpathians. The correlation showed that the FO of M. furcatus was diachronous, becoming younger from east to west. In the Silesian Unit it appears in the lower Turonian in association with Eprolithus moratus (UC6b nannofossil Zone). In the Pavlovské vrchy klippes it appears in the upper middle Turonian together with Lithastrinus septenarius (UC9 Zone). In the Bohemian Cretaceous Basin, the FO of M. furcatus was observed in the lower upper Turonian just above the FO of Liliasterites angularis. The presence of M. furcatus in Turonian strata is scarce and discontinuous up to its sudden quantitative increase (represented by 5–27% in assemblages) below the FO of the inoceramid bivalve species Cremnoceramus waltersdorfensis and C. deformis erectus in the Turonian–Coniacian boundary interval. The top of the M. furcatus acme was recorded below the FO of Micula staurophora. The second quantitative rise of M. furcatus (12% in assemblage) was found in the lower lower Campanian of the Pavlovské vrchy klippes above the FO of Broinsonia parca parca in the UC14a Zone and the last occurrence of the planktonic foraminifer Whiteinella baltica. Above this second acme M. furcatus disappears. The significantly earlier appearance of M. furcatus in the Silesian Basin may be connected with a southeast-heading surface current from the North European epicontinental sea where the species appeared in the early Turonian too. 相似文献
16.
AbstractFlysch and molasse are discussed in the light of alpine geodynamics. They are pre-collision and post-collision orogenic clastics which accumulated in basins under different geodynamic controls. We propose that in the case of the Alps, their succession records the change in geodynamics from pre-collision inversion of shallower extensio-nal structures, to post-collision inversion of one or more deep-seated features.The classical flysch of the Prealps, lying within a pile of nappes at the front of the Western Alps, are invariably turbidite deposits. Flysch has therefore acquired a sedimentological connotation over the years, and this has been emphasized over the last few decades. Turbidite facies were also laid down in marginal and foreland locations during and a little after the collision between the South and North Tethyan Alpine margins, and this has obscured the possible deeper signification of flysch and molasse.Geodynamic regimes dictate the subsidence behaviour of basins, so by use of geohistory analysis, the time and place of the onset of Molasse basin development may be located. This was at the southern margin of the Helvetic belt, from the start of the Oligocene. Along the Alpine traverse of Western Switzerland, the change in regime from flysch to molasse (i.e. from trench and forearc or retro-arc, to foreland basin deposits) suggests that a major deep-seated inversion structure was situated near the Helvetic-Ultrahelvetic boundary. 相似文献
17.
Ancient flow type landslides are relatively frequent fossil forms of the relief in mid-mountain conditions of the Czech Carpathian Mountains.Sixty rather distinctive displays of debris flows,rock avalanches,and debris avalanches have been mapped in the uppermost part of the territory.Unlike contemporary sporadic and low volume debris flows,ancient (Pleistocene and Lower Holocene) accumulations are a few orders of magnitude more extensive and were of considerable geomorphologic significance in forming the steep sections of mountain valleys and slopes.This geomorphic pattern does not hold for flow type slides,the source of which is material released as a consequence of numerous deep-seated landslides.Due to deep disruption of slopes,a few high-magnitude flow type landslides (e.g.,rock avalanches),quite rare in flysch mid-mountain conditions,also occurred in the Late Holocene. 相似文献
18.
Davide Lenaz Claudio Mazzoli Jan Spišiak Francesco Princivalle Lara Maritan 《International Journal of Earth Sciences》2009,98(2):345-355
The Šambron–Kamenica Zone is situated on the northern margin of the Levočské vrchy mountains and Šarišskà vrchovina Highland,
where the Central Carpathian Paleogene joins the Pieniny Klippen Belt. Sandstone outcrops in this area. From Cretaceous to
Late Oligocene in age, these sediments suggest transport directions from S and SE. The heavy mineral assemblages of this sandstone
include Cr-spinel grains, mainly displaying types II and III alpine-peridotite affinities, and are representative of Ocean
Island Basalt volcanism. A sample from Upper Eocene sediments at Vit’az shows a clear change in Cr-spinel composition, which
turns out to have types I and II peridotite affinities, and to derive from arc and Middle Ocean Ridge Basalt volcanism, with
sediment transport directions from SW and WSW. These data indicate major variations in the Upper Eocene tectonic setting,
giving constraints to paleogeographic reconstruction of the Slovak Central Carpathians. 相似文献
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20.
Paola de Capoa Angelida Di Staso Francesco Guerrera Vincenzo Perrone Mario Tramontana Mohamed Najib Zaghloul 《Geodinamica Acta》2013,26(2):141-157
Abstract Volcaniclastic debris-rich formations, characterising the Troina-Tusa Unit in the Sicilian Maghrebian Chain, are examined. The Troina-Tusa Unit terrains sedimented in the Maghrebian Flysch Basin, which, from Jurassic to Early Miocene, constituted the southernmost branch of the Western Tethys, located between Africa and the Mesomediterranean Terrane margins. New field, biostratigraphic and pétrographie data enable a reconstruction of the palaeogeographic and structural evolution of the Flysch Basin immediately before its deformation. All the studied formations transpired to be Burdigalian in age. The sandstone compositions, showing different source areas (magmatic arc, recycled orogen and continental block), indicate a provenance for the clastic material from a crystalline basement with an active volcanic arc, replaced by a remnant volcanic arc, which was rapidly completely eroded. The source area that has been considered is Sardinia, where Upper Oligocene -Aquitanian calc-alkaline volcanites are widespread, but the sedimentological characteristics and the Burdigalian age do not fit with this provenance. The Burdigalian calc-alkaline arc should be located on the internal side of the Troina-Tusa Basin, above the already stacked Peloritanian units. A migration of the volcanic activity, connected with the subduction plain roll-back, can be envisaged from the Sardinia Block to the Peloritanian Chain, this latter still docked to the Sardinia-Corsica massif. © 2002 Editions scientifiques et médicales Elsevier SAS. All rights reserved. 相似文献