Study On Lithofacies Palaeogeography Of Mesozoic And Cenozoic Of Northwest India Plate And Its Adjacent Areas

Guided by the multidisciplinary theory of plate tectonics,sedimentology,tectonic geology and tectonostratigraphy,this paper dissects five representative basins using a large number of published documents in IHS database,summarizes,summarizes and analyses six Mesozoic and Cenozoic strata(Triassic,Jurassic,Lower Cretaceous,Upper Cretaceous)of 39 basins and orogenic belts in the study area.The lithofacies assemblages and palaeogeographic types of the Series,Paleogene and Neogene have been compiled,relevant maps have been compiled,ArcGis attribute table has been filled in,lithofacies palaeogeographic maps of six strata have been compiled,and the lithofacies palaeogeographic characteristics of the Mesozoic and Mesozoic in the northwest of the Indian plate and its adjacent areas have been revealed.The Mesozoic and Mesozoic lithofacies assemblages in the study area are unified into the following 14 types: sandstone+mudstone,sandstone+mudstone+carbonate rock,conglomerate+sandstone+mudstone,evaporite+carbonate rock,evaporite+clastic rock,evaporite rock,carbonate rock,mudstone,coal-bearing rock series,moraine,volcanic rock+clastic rock,volcanic rock+carbonate rock and metamorphic rock.Palaeogeography is divided into 10 units: uplift denudation area,alluvial area,Lake area,coastal area,shallow sea area,coastal shallow sea and salt marsh,delta,island arc,semi-deep sea area and submarine fan.The uplift denudation area lacks sedimentary records;while the alluvial area is composed of sandstone + mudstone,conglomerate + sandstone + mudstone or volcanic + clastic rock;the lake area and delta are sandstone + mudstone facies assemblages;the shallow sea area is mainly composed of sandstone + mudstone + conglomerate,sandstone + mudstone facies assemblages,with locally developed evaporite + clastic rocks,and the semi-deep sea-deep sea area is composed of mudstone and volcanic + clastic rocks.The main lithofacies of island arc is volcanic rock.The littoral shallow sea area and semi-deep sea-deep sea area of orogenic belt and basin basement are mainly composed of metamorphic lithofacies assemblages.The Triassic study area is dominated by uplift erosion and post-Triassic terrain.The littoral-shallow sea area characterized by evaporite,carbonate,clastic and metamorphic rocks develops in the northwest of the Indian plate,the East and north of the Arab plate,and the Pamir area is a semi-deep-sea area with metamorphic rocks as its record.The Jurassic shallow sea area expanded,the uplift denudation area shrank,the Pamir area evolved into an island arc,and the Helmand area is a semi-deep seadeep sea area with metamorphic rocks and volcanic rocks as its records.The early Cretaceous shallow sea area expanded further,the uplift denudation area narrowed further,the island arc inheritance developed in Pamir area,and the semi-deep sea-deep sea area recorded by volcanic rocks in the southern side of Helmand area expanded significantly.Late Cretaceous basically inherited the palaeogeographic pattern of early Cretaceous.The most significant change is that the southern,western and northeastern sides of Helmand area evolved from oceanic area to island arc.Compared with the previous period,the eastern uplift denudation area of the study area expanded and the northwest island arc increased significantly.In Neogene,the uplift denudation area and alluvial area expanded significantly,and the whole shallow sea contracted to the periphery of the Arabian Sea.The Mesozoic lithofacies and palaeogeography characteristics and evolution laws in the above-mentioned study areas are closely related to the opening and closing history of the New Tethys Ocean.