| 词条 | Rajmahal Traps |
| 释义 |
GenesisThese volcanic rocks were formed from the eruptions over the Kerguelen hotspot in the early Cretaceous.[2] The similarity between the geochemical data of Rajmahal volcanis and lavas of the Kerguelen Plateau confirms this. According to plate tectonics, the Indian subcontinent was over this hot spot during the Cretaceous Period. The original lava flow covered an area of nearly {{convert|4100|sqkm|sqmi|abbr=on}}. Below the Bengal basin the flows cover {{convert|200000|sqkm|sqmi|abbr=on}}.[3] LithologyThe Rajmahal volcanics are predominantly tholeiitic basalt, quartz tholeiite, olivine tholeiite and alkali basalt. The Intertrappean Beds are composed of sedimentary rock such as siltstone, claystone and shale.[1] Structural evolutionThe western boundary of the Rajmahal Traps is faulted and down-thrown towards the east. The eastern boundary of this trap has a North-South trending, fault-controlled basement. This basement connects the Purnea basin of the Ganga valley with the Bengal basin. These faulted contacts, along with the Damodar Gondwana graben, form a triple junction at the mouth of the Bengal basin. The traps evolved along the then eastern continental margin of India, following rifting of Gondwanaland. Over the epochs, the upper part of the lava deformed in a cold, brittle fashion and formed graben structures.[3] FossilsThe Intertrappean Beds contain an assamblage of Lower Cretaceous plant fossils. The assemblage includes Cladophlebis indica, Dictyozamites indicus, Taeniopteris spatulata, and Brachyphyllum rhombium. See also
References1. ^1 {{cite book|last=Valdiya|first=K. S.|title=The Making of India, Geodynamic Evolution|year=2010|publisher=Macmillan Publishers India Ltd.|isbn=978-0230-32833-4|pages=323}} 2. ^Courtillot, Vincent. Evolutionary Catastrophes: The Science of Mass Extinctions. Cambridge, Cambridge University Press, 1999; p. 95. 3. ^1 {{cite journal|last=Singh|first=A. P.|author2=Niraj Kumar |author3=Bijendra Singh|title=Magmatic underplating beneath the Rajmahal Traps: Gravity signature and derived 3-D configuration|journal=Proc. Indian Acad. Sci. (Earth Planet. Sci.)|date=December 2004|volume=113|issue= 4|url=http://www.ias.ac.in/article/fulltext/jess/113/04/0759-0769|accessdate=8 March 2017}} 4 : Cretaceous volcanism|Extinction events|Geography of Jharkhand|Volcanism of India |
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