Talchir Sedimentation in Jayanti Gondwana Basin: A Case of Glacio-Lacustrine Low Slope Prograding Delta Sedimentation

Reconstruction of sedimentation pattern and palaeogeographic model during Talchir sedimentation in Jayanti Gondwna basin has been attempted in the present paper.

The Talchir rocks in the basin consist of three distinct facies assemblages : Finer facies assemblage (Unit I) representing lake bottom sediments emplaced by two sets of processes namely - suspension from sediments introduced into the lake by interflow and overflow currents and turbidity current triggered by slumping in lake floor and delta front.

Sandstone facies assemblage (Unit II) representing mainly low slope (∼5°) delta deposits. Channels, interchannel and bar sediments fonn the topset of the delta. The foreset beds are difficult to identify because of very low slope of the delta margin.

The upper coarser facies assemblages (Unit III) introduced into the lake by various glaciogenic processes. The most dominant process was range of gravity flow processes generated on the steeper slope in the subaerial part to the south of the lake margin. Sudden change of slope from steep in the subaerial part to gentle in the lake margin has restricted the distribution of the facies along the southern low slope lake margin.

The depositional model is that of a low slope, prograding glacio-fluvial delta advancing over glacio-lacustrine sediments. The model suggested is a modification of available glacio-lacustrine model of moderate to high slope glacial lakes.