Palaeoenvironmental reconstruction for the Permian(lower Gondwana)succession of the Godavari Valley Coalfield in southern India based on a combined palynofacies,carbon isotope,and biomarker study  

作　　者：Neha Aggarwal Runcie Paul Mathews Arif Husain Ansari Biswajeet Thakur Shailesh Agrawal 

机构地区：[1]Birbal Sahni Institute of Palaeosciences,53 University Road,Lucknow 226007,India

出　　处：《Journal of Palaeogeography》2022年第1期123-144,共22页古地理学报（英文版）

基　　金：funded by the Birbal Sahni Institute of Palaeosciences,Department of Science and Technology,Lucknow,India(BSIP/RDCC/Publication no.63)。

摘　　要：The study presents integrated palynofacies,organic carbon isotope,and biomarker data to reconstruct palaeoenviromental setting for the Permian sediments(borehole MGK-6)of the Kachinapalli block of the Godavari Valley Coalfield,southern India.The palynofacies data reveal three distinct palynofacies(A-C)as follows.Palynofacies A is dominated by abundant arborescent vegetation(glossopterids and conifers)along with structured organic matter,suggesting freshwater forest swamps in proximal settings.Palynofacies B is dominated by abundant degraded organic matter and amorphous organic matter,suggesting lakeshore/flooded palaeomires in slightly dismal settings.It has a high water level in the hinterland,which enables bacterial degradation of organic matter and establishes low-oxygenation conditions within the water column.These conditions would have provided grounds for the accumulation of either degraded or amorphous organic matter.Palynofacies C is dominated by the abundance of charcoal/opaque phytoclasts,indicating prolonged transportation or postdepositional alteration,suggesting a highly-oxidizing condition in distal settings.The bulk organic δ^(13)C range(-25.1‰ to-20.9‰)in the borehole MGK-6 is in close agreement with the global Permian records.This study also shows a weak but statistically significant correlation with the major forms of palynofacies A and C.The interlinked behaviour of bulk organic δ^(13)C and palynofacies suggests that the changes in palaeobiogeography/palaeodepositional settings were most likely driven by the change in mean annual precipitation.The biomarker study shows the presence of n-alkane from C_(15) to C_(31) with unimodal and bimodal distribution patterns,revealing the source materials as vascular plants and microbially-altered organic matter.The combined palynofacies,organic carbon isotope,and biomarker data provide vital clue to salient findings for the development of environmental conditions of Godavari Valley Coalfield during lower Gondwana sedimentation.

关 键 词：Artinskian GUADALUPIAN Depositional environment Carbon isotope BIOMARKER Godavari valley coalfield 

分 类 号：P534.51[天文地球—古生物学与地层学]