Abstract

Straight-crested and internally bipolar cross-stratified eolian dunes are common in the upper part of progradational cycles within the late Proterozoic Upper Bhander Sandstone, Son Valley, India. The Sandstone formed in a coastal setting, and it encompasses supralittoral storm, eolian sand sheet, draa, pond, and ephemeral stream deposits. Ripples of three different size and vector populations typically occur within the dune deposits. The smallest population shows migration parallel to the dune crests, and other two show migration obliquely towards the dune crests. Simple interpolation reveals only 98 deviation of the dune trend from the long-term resultant wind direction. In addition to the two primary wind vectors that control the duneforms, the sand transport ratio less than 1.2 suggests that these are longitudinal dunes. Forward computer modeling and calculation of the maximum gross bedform-normal transport direction further corroborate that the dunes were longitudinal. The dunes are smaller and architecturally simpler than most other longitudinal dunes described in the literature. The methodology adopted here is a useful approach to evaluate longitudinal dunes in the rock record.

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