ABSTRACT

A 40-m-thick eolian sand sheet deposit characterizes the upper part of the Proterozoic Shikaoda Formation near Hosangabad. It sharply overlies shoreface deposits and comprises wind-ripple strata ( 50%), adhesion strata ( 17%) and subaqueous strata ( 33%). Each stratification type defines stratal packages tens of centimeters thick and few meters wide that are superposed upon one another in a nearly random fashion. The eolian facies is inferred to have been deposited in a low-gradient, sandy supratidal setting. The subaqueous deposits of the sand sheet also reflect a tide-affected, westward-opening coastal setting with an approximately north-south shoreline. Abundance of aqueous and adhesion strata coupled with the absence of granule-rich coarse-grained layers, corrugated erosion surfaces and evaporites are the typical features of the Shikaoda eolian sand sheet. These features indicate that in spite of abundant sand supply from the coastal sources and a net aggradational setting, repeated flooding and high surface moisture were the principal factors that inhibited dune-building processes and favored the growth of a flat-bedded eolian sand sheet in the Shikaoda Sandstone.

Numerous subhorizontal, nearly flat bounding surfaces split the sand sheet succession into tabular sediment bodies 50-100 cm thick. Each of the bounding surfaces can be traced for a few tens of meters and can be correlated to an event of aqueous flooding. Vertical stacking of tabular sandstone bodies implies that long-term sediment aggradation rate in the low-lying supratidal region kept pace with that of basin subsidence.

The sedimentological features of the Shikaoda sand sheet facies when compared with known modern and ancient sand-sheet deposits suggest that the Shikaoda sand sheet developed independent of an erg in a comparatively wet climatic setting. The sub-humid coastal eolian sedimentary system of Padre Island, Texas is probably the closest modern analogue of the Shikaoda sand-sheet facies.