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Internal Stratigraphy of the Mesoarchean Keonjhar Siliciclastics, Singhbhum Craton, Eastern India: Paleogeographic Implications
Journal of the Geological Society of India ( IF 1.3 ) Pub Date : 2021-02-12 , DOI: 10.1007/s12594-021-1642-1
Saheli De , B. C. Sarkar , Ashim Jana , Joydip Mukhopadhyay , D. K. Sinha , M. B. Verma

In comparison to the greenstone belt volcano-sedimentary successions, mature arenite dominated sedimentary deposits are very rarely preserved in Paleo-Mesoarchean rock record. Such arenitic deposits may be important for the recognition of extensive development of continental freeboard and onset of Phanerozoic style plate tectonics. The Keonjhar siliciclastics are ∼715-m thick mature arenite-dominated Mesoarchean succession that unconformably overlies Paleo-Mesoarchean granite-greenstone core of the Singhbhum craton. The succession is mapped on 1:50,000 scale, and is designated as the Keonjhar Quartzite. It is subdivided into conglomerate dominated lower unit as the Asurkhol Member and mature arenite dominated upper unit as the Kamalpur Member. A lensoid body of iron ore clast bearing conglomerate unconformably overlies the Keonjhar Quartzite, and is designated here as the Chamakpur Conglomerate. The succession is repeated by three westerly dipping reverse faults that have upthrown the deeper parts of the basinal transects against shallower parts. The Asurkhol Member represents subaerial part of a coastal alluvial fan. The Kamalpur Member represents shallow-shelf depositional setting. Detailed mapping and recognition of the fault slices led to the reconstruction of the paleogeographic setting. The present study also highlights the importance for the stratigraphic correlation of the Keonjhar Quartzite with underlying metabasics of Malangtaoli-Jagannathpur lava and the overlying western IOG succession. The internal stratigraphic classification proposed here is also significant from economic point of view with regard to the occurrences of uraniferous QPCs in the Asurkhol Member and detrital iron ore deposits in the Chamakpur Conglomerate.



中文翻译:

Mesoarchean Keonjhar硅质碎屑的内部地层学,印度东部Singhbhum Craton:古地理学意义

与绿岩带火山沉积相继的相比较,在古美苏拉奇纪的岩石记录中,很少有成熟的以褐砂岩为主的沉积物。这样的球状沉积物对于认识大陆干舷的广泛发展和生代样式板块构造的发生可能是重要的。Keonjhar硅质碎屑岩约为715米厚,是成熟的,以花岗岩为主体的中生代阶地,不整合地覆盖了Singhbhum克拉通的古中生代花岗岩-绿岩岩心。该系列以1:50,000比例绘制,并命名为Keonjhar石英岩。它被细分为以Asurkhol成员身份的大企业为主的下部单元,以及作为Kamalpur成员身份的成熟的以花岗岩为主体的上部单元。铁矿石碎屑的类球体不均匀地覆盖在Keonjhar石英岩上,并在此处指定为Chamakpur集团。通过三个向西倾斜的逆断层重复演替,这些断层使盆地样带的较深部分与较浅部分发生了颠覆。Asurkhol成员代表沿海冲积扇的陆上部分。Kamalpur成员代表浅层沉积环境。断层切片的详细映射和识别导致了古地理环境的重建。本研究还强调了Keonjhar石英岩与Malangtaoli-Jagannathpur熔岩潜在的元成因和上覆的IOG演替对地层相关性的重要性。

更新日期:2021-02-15
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