These rocks, which contain mud cracks, ripple marks
, and terrestrial plant debris, suggest deposition in a shallow, marginal sea with alternate desiccation and stream floodwater input.
The sedimentary structures noticed include laminations, cross bedding, ripple marks
, burrows, liesgang rings (?) and graded bedding.
Fossil ripple marks are important features indicative of a specific depositional environment of an ancient basin.
In Estonia fossil ripple marks have been identified in Cambrian and Devonian siliciclastics as well as in Ordovician and Silurian carbonate rocks.
Key features of these specimens include flaked surfaces running in two or more directions and ripple marks
, cracks and protrusions clearly resulting from the impact required to detach flakes from stone.
Mark and Ali (1961) and Ali (1962) studied the Tanawal Formation near Tarbela as well in the presently studied area and described preponderance of well- bedded quartzites with excellent cross bedding and ripple marks. Calkins et al.
The sequence is characterized by common cross bedding and ripple marks. The thickness of this member in the Sherwan Syncline is over 500 m.
Photos from underwater cameras showed that these storms erased animal tracks and created ripple marks
in the sediments.
Bioturbation, ripple marks
and mudcracks are observed in Mianwali Formation, while cross bedding is dominant in the overlying Tredian Formation.
and mud cracks are preserved in the Precambrian Bass, Hakatai, Dox, and Nankoweap Formations.
as indicators of Late Ordovician sedimentary environments in Northwest Estonia.
The sandstone is mainly composed of thin to thick bedded, gray to whitish gray to brown sandstone that is fine to medium grained and displays some laminations, ripple marks
, flat beds and cross beds at places.