Marinoan glaciation in the Indian subcontinent——Anatomy and global implications

Detailed sedimentological analysis of the Pokaran Boulder Bed,representing the most basal unit of the Neoproterozoic-Lower Cambrian Marwar Supergroup,clearly indicates its glacial origin.The glacial sediments are interpreted as an ice-contact submarine fan deposit.Based on the detrital and inherited zircon population of the Marwar Supergroup sediments and interlayered pyroclastic deposits,a Marinoan cryochron of the Cryogenian Period is envisaged for the Pokaran Boulder Bed.The well-preserved Ediacaran elements in the post-glacial sedimentary succession also support a Cryogenian to Early Cambrian age of the Marwar Supergroup.The glacial deposition at the base of the Marwar Supergroup strengthens the regional correlation between the studied sediments with the Lesser Himalayan Blaini-Krol-Tal sediments and the Haqf Supergroup of Oman.The available zircon ages and paleomagnetic data of the Malani Igneous suite,along with the Marinoan glacial deposits,detrital zircon ages,and Ediacaran fossil elements of the Marwar Supergroup add significant information to the Neoproterozoic Earth history.

Lithofacies architecture and palaeogeography of the Late Paleozoic glaciomarine Talchir Formation,Raniganj Basin,India

Talchir Formation （Permo-Carboniferous） of the Gondwana Supergroup records the Late Paleozoic glaciation in Peninsular India. Talchir sedimentary succession of the Raniganj Basin, Damodar Valley Coalfields, Peninsular India, bears ten facies types grouped under three facies associations, viz., the proglacial conglomerate-sandstone facies association （CS）, the foreshore-shoreface conglomerate-sandstone-mudstone facies association （CSM） and the prodelta-shelf sandstone-mudstone facies association （SM）. Overall facies architecture reflects initial ice-covered terrestrial subgiacial sedimentation, which was subsequently reworked and emplaced subaqueously in front of the ice-grounding line, and finally overlapped by storm-laid prodelta-shelf sediments. Repeated glacial advance-retreats with shifts in the position of the ice-grounding line during phases of climatic amelioration led to multiple deglaciation-related fining-up cycles. Decoupled ice sheet and floating icebergs contributed icerafted debris （IRD） to these sediments. Gradual retreat of the ice sheet, however, restricted the supply of IRD towards top of the succession. Overlap of wave-agitated shoreface-shelf sediments on the glaciogenic sediments indicates widespread marine transgression caused by glacier melting during ice-house to green-house climatic transition, and crustal downsagging related to giacioisostasy. Subsequently, complete disappearance of the ice sheet caused basinal exhumation along with crustal uplift due to isostatic rebound, leading to multiple horst-graben bounded basinal systems, which received post-Talchir coal-bearing Gondwana sediments.