Middle Eocene regressive phase evident in the uppermost part of the Harudi Formation, Kachchh Basin, western India

The present study focuses on the presence of gypsiferous foraminiferal packstone (GFP) facies which defines the top of the Lutetian aged Harudi Formation and separates it from the overlying Bartonian aged Fulra Limestone Formation. This facies has been reported from Harudi and Lakhpat areas of Kachchh District and may serve as a regressive stratigraphic boundary between the Harudi and Fulra Limestone Formations that had been previously considered as conformable succession. Here, the gypsum, halite and iron oxide minerals (hematite and/or goethite) are precipitated as secondary minerals in the desiccation cracks developed in the foraminiferal packstone facies. The precipitation of gypsum, halite and hematite/goethite along with desiccation cracks is suggestive of the oxidizing condition and would have been possible in supratidal environment under warm and dry semi-arid to arid climatic conditions. Thus, it is inferred that the cracks would have been formed during subaerial exposure of the foraminiferal packstone facies during relative sea-level fall.