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Facies and depositional sequences of the Asmari Formation, Shajabil Anticline, North of the Izeh Zone, Zagros Basin, Iran

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Acta Geologica Sinica(English Edition) 2013年第6期87卷 1520-1532页

作者： Zahra SALEH Ali SEYRAFIAN Department of Geology University of Isfahan

Outcrop and microscopic studies have been applied in this research paper in order to find out the Asmari Formation depositional sequences in the Shajabil Anticline section located at the north of the Izeh Zone,Zagros Basin,*** depositional sequences were identified based on 11 facies types （bioclast Nummulitidae Lepidocyclinidae packstone,bioclast perforate foraminifera Nephrolepidina Miogypsinoides wackestone-packstone,bioclast perforate foraminifera Corallinacea wackestone-packstone,bioclast echinoid Neorotalia Brachiopoda wackestone-packstone,coral floatstone-rudstone,bioclast Corallinacea imperforate foraminifera wackestone-packstone,bioclast imperforate foraminifera Archaias wackestone-packstone,bioclast imperforate foraminifera Dendritina wackestone-packstone-grainstone,bioclast imperforate foraminifera Borelis wackestonepackstone and very fine sandy mudstone） corresponding to the tidal flat,restricted and semirestricted lagoon and open marine environments of an inner and middle shelf ***-exposed outcrop horizons of Thalassinoides at the study section are a favorable tool for the regional outcrop sequence *** is considered as an outcrop key-bed for recognition of the Rupelian-Chattian maximum flooding depositional *** remnants （small colonies） in outcrop exposures also are associated with the HST depositional sequence （Chattian） for the Asmari *** most important achievement of this research is use of associated maximum flooding surfaces （Pg30,Pg40,Pg50,Ngl0 and Ng20） in the Arabian *** maximum flooding surfaces could be recorded as an isochrones surface.

关键词： depositional sequence Thalassinoides Asmari Formation north-central High Zagros Iran

Evolution of an Eocene–Oligocene Saline Lake depositional System and Its Controlling Factors, Jianghan Basin, China

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Journal of Earth Science 2014年第6期25卷 959-976页

作者： Chunju Huang Linda Hinnov State Key Laboratory of Biogeology and Environmental Geology School of Earth SciencesChina University of Geosciences Department of Earth and Planetary Sciences Johns Hopkins University

The Upper Eocene–Lower Oligocene Qianjiang Formation of the Jianghan Basin in central China consists of a 4700-m-thick lacustrine succession, containing 1800 m of halite deposits. The maximum thickness of the formation is 4700 m, and includes 1800 m of halite. We have identified eight third-order depositional sequences based on pinch-out and onlap stratigraphic patterns in 2-D and 3-D seismic data and well logs. The basin evolved from a deep to shallow under-filled lake during the Eocene–Oligocene interval. The main rock types are dark mudstones, halite, and siltstone/sandstone in the depocenter, and alternating mudstone and gypsum in shallower areas. The vertical succession indicates a strong sedimentary cyclicity. depositional facies indicate the presence of two lake system types. Halite developed in a saline lake system, whereas clastic sediments were deposited in freshwater lake systems. The alternating sediment types indicate that the basin cycled repeatedly between saline and freshwater lake systems. This cyclicity was caused by availability of accommodation space that was controlled by a combination of climate change, tectonic subsidence and sediment supply; notably, the highest frequency cycles occurred at Milankovitch timescales controlled by the Earth＇s orbital variations. The cyclic halite plays an important role in generating and preserving oil in the Qianjiang Formation of the Qianjiang depression.

关键词： saline lake depositional sequence Eocene Oligocene Milankovitch cycle Jianghan Basin Qianjiang Formation

Sedimentary Characteristics of the Cretaceous in the Songliao Basin

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Acta Geologica Sinica(English Edition) 1993年第2期67卷 167-180页

作者： Liu Zhaojun, Wang Dongpo, Liu Li, Liu Wanzhu, Wang Pujun, Du Xiaodi and Yang Guang Changchun University of Earth Sciences, Changchun, Jilin Sun Sheping Changchun University of Earth Sciences Changchun Jilin

The rupture of the lithosphere in Late Jurassic brought about the eruption of basaltic magma in the Songliao Basin. The evolution of the basin in Cretaceous progressed through six stages: pre-rift doming, extensional fracturing, fault subsidence, fault downwarping, downwarping and shringkage, resulting in the deposition of terrstrial facies nearly 10,000 m thick. There are different depositional sequences in these stages: the depositional period of the Early Cretaceous Shahezi and Yincheng Formations is the development stage of the down-faulted basin, forming a volcanic rock-alluvial fan-fan delta-lacustrine (intercalated with episodic turbidites)-swamp facies sequences; the period of the Early Cretaceous Dengluku Formation is the transformation stage of fault subsidence into fault downwarping of the basin, forming a sequence mainly of alluvial plain-lacustrine facies; the depositional period of the Early Cretaceous Quantou Formation-Late Cretaceous Nenjiang Formation is the downwarping stage of the basin, forming an alluvial plain-delta-lacustrine facies sequence; the period of the Late Cretaceous Sifangtai Formation-Mingshui Formation is the shringkage stage of the basin, forming again a sequence mainly of alluvial plain-alluvial fan and small relict lacustrine facies. These vertical depositional sequences fully display the sedimentary characteristics of a failed continental rift basin. Many facts indicate that the two large-scale lake invasions, synchronous with the global rise of sea level, which took place in the downwarping stage of the basin development, led to the connection between the lake and sea.

关键词： depositional sequence eustasy anoxic event Songliao Basin