Characteristics Genesis and Sedimentary Environm

Authors: Liangtian Ni Jianhua Zhong Zhufu Shao Yong Li Cui Mao Shengxin Liu

Publish Date: 2015/10/21

Volume: 26, Issue: 5, Pages: 677-689

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Abstract

A particular type of softsediment deformation structure similar to imbricate structure is developed in the Jurassic strata at Honggouzi western Qaidam Basin China We refer to this structure as a duplexlike deformation structure because it is inferred to have been formed by the action of fastmoving submarine gravity current sediments gliding across a preexisting semiconsolidated sedimentary layer The layers of duplexlike structure crop out in the southeastern limb of the core of a mediumsized anticline The average dip direction of the duplexlike structure is 3012° and the average dip angle is 547° Duplexlike deformed laminations are composed mainly of weakly metamorphosed extremely poorly sorted feldspathic lithic graywacke Sericite can be observed along bedding planes The duplexlike structure occurs within a sequence of riverchannel fine conglomerate interchannel carbonaceous mudstone shale shallowwater delta sandshale shallowlake calcareous mudstone olistostromes and a turbidite At the bottom of the sequence we found brownishred shallowlake calcareous mudstone and carbonaceous mudstone and at the top olistostromes whose genesis is related to the slip and drag of a slumped body of submarine sediment In combination with other symbiotic and associated structures it is considered that the duplexlike structure was formed by the slumping and subsequent movement and traction of deltafront semiconsolidated sediments over the bottom sediments of a shore or shallowlake sedimentary environment probably triggered by an earthquake The attitude of the duplexlike structure indicates that the direction of gliding was from NW3012° toward SE121° which is consistent with the current location of the Altun Mountains indicating that the Altun Mountains existed in the Jurassic The orogenesis of these mountains likely involved seismic activity and an earthquake was the triggering factor in the formation of the duplexlike structure by causing the slumping/gliding of the olistostrome sedimentsNi L T Zhong J H Shao Z F et al 2015 Characteristics Genesis and Sedimentary Environment of DuplexLike Structures in the Jurassic Sediments of Western Qaidam Basin China Journal of Earth Science 265 677–689 doi101007/s1258301505782 http//enearthsciencenet

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