A Reappraisal of Stratigraphy of Bagh Group of Rocks in Dhar District, Madhya Pradesh with an Outline of Origin of Nodularity of Nodular Limestone Formation

摘要

Upper Cretaceous Bagh Group of rocks in M.P. have been studied by many workers. Several stratigraphic successions have been proposed. It has resulted in controversies in terms of applicability, absence of characterization of contact surfaces, no mention of locality names where characteristic features are well visible. Hence a new stratigraphic succession has been proposed. Besides, the entire area is characterized by different types of nodularity at least in the lower part of carbonates. This worldwide unique characteristic has not been resolved earlier. The present authors have tried to explain the origin of this nodularity on the basis of adequate field evidences and came to the conclusion that overburden mechanical compaction produced by Lametas and Deccan Trap and subsequent chemical compaction are the ultimate cause of nodularity in the carbonates. Later entire area was reactivated and churned by Thallassinoid burrow producing organism, the presence of which bears testimony.