Tsenchumo Lotha and S.K. Srivastava*

Department of Geology, Nagaland University, Kohima-797004, Nagaland, India (*Corresponding Author, E-mail: skssrivastava@nagalanduniversity.ac.in)

Abstract

The Dillai Parbat is known for its rich limestone deposits represented dominantly by wacke, grain and pack stones. In addition to that fine to medium grained sandstones and carbonaceous shale / shale are also present. Both epifaunal and infaunal forms of the microfossils have been observed. Plane/cross laminations, herringbone and hummocky cross stratifications are the sedimentary structures recorded in the study area. The sediments of the study area are intensely bioturbated which has imported a mottled character to it. Benthic forms of the identified microfossils include Bolivina, Lagena, Anomalina, Rotalia, Pararotalia, Neoeponides, Spiroloculina, Quinqueloculina, Triloculina, Bolivina, Bulimina, Trifarina, Nummulites, Operculina, Cibicides. Globigerina and Globorotaloides represent planktic forms of the microfossils. Mega fossils such as gastropods, echionoides and varieties of crabs have also been encountered. Trace fossils including Skolithos verticalis, Palaeophycus tubularis and Thallasinoides horizontalites have also been observed. Based on the above evidence a shallow marine warm water, rich in nutrients and oxygen within a lagoon /shallow marine environmental set up with fluctuating regime have been envisaged for these limestones.

Keywords: Depositional Environment, Palaeoecology. Shallow Marine, Environment, Dillai Parbat, Nagaland