Microvertebrate Paleontology of the Infratrappean Beds of Bacharam and Jaidpalli, Rangareddy District, Telangana

Kanimeraka, Dhanush Kumar (2022) Microvertebrate Paleontology of the Infratrappean Beds of Bacharam and Jaidpalli, Rangareddy District, Telangana. Masters thesis, Indian Institute of Science Education and Research Kolkata.

Text (MS dissertation of Dhanush Kumar Kanimeraka (17MS176)) 17MS176_Thesis_file.pdf - Submitted Version Restricted to Repository staff only Download (3MB)

Abstract

Deccan volcanism of peninsular India was considered as one of the possible causes for the mass extinction at the Cretaceous-Palaeogene. If Deccan volcanism of India could wipe out the life significantly globally one would like to know what are the effects of volcanism at the actual site of eruption. In order to evaluate this, one should examine the fossil biota preserved in the sedimentary beds deposited in the lacustrine basins during the dormant stages of volcanism. The sedimentary beds that occur below the oldest flows are known as the infratrappean beds while those deposited in between the volcanic flows are known as the intertrappean beds. The intertrappean beds have been extensively studied in the recent past with reference to their vertebrate faunas. As compared to this, the infratrappean beds, except for those of Jabalpur and Pisdur-Nand-Dongargaon basins, were least explored for their vertebrate faunas. Dinosaur body fossils and nests and eggs are extensively known from the infratrappean beds or Lameta Formation, but we know very little about other lower vertebrates and mammals. As it is important to know the biotic changes from the infratrappean to intertrappean beds to better understand the effects of initial Deccan volcanism on contemporaneous biota, the infratrappean beds, viz., Bacharam and Jaidpalli, of Rangareddi District, Telengana were selected for detailed microvertebrate palaeontological investigation. Secondly, Bacharam is the only infratrappean bed that yielded a mammal as compared to several mammal-yielding intertrappean beds. Therefore, it is also aimed at knowing whether there is any difference between the mammalian faunal composition of the infratrappean and intertrappean beds. The infratrappean beds of Bacharam yielded the late surviving haramiyid mammal. No haramiyid mammal was documented from the well-studied intertrappean beds, rather they yielded gondwanatherian and eutherian mammals. Since the area around Vikarabad is known to preserve several infratrappean horizons, this area is chosen for the present work. To achieve the objectives of the present work, both mechanical and chemical, methods were used in the microvertebrate fossil extraction from various kinds of rocks. Sorting of screen-washed residue under stereoscopic microscope led to the recovery of limited number of microvertebrate fossils. The fossils collected are a mix of both marine and terrestrial elements. The microvertebrate assemblage is an admixture of marine/brackish water taxa (e.g., pycnodontids) and freshwater taxa (e.g., Lepisosteus, Osteoglossids, Silurifomes, turtles and crocodiles). You can have only such a mixed fauna because of the occurrence of depositional basins close to coastal environments or coastal plains. The marine elements get incorporated into a fresh water lake or pond during short term marine incursion. The fossils recovered from the studied infratrappean beds are very similar to those of the other infratrappean and intertrappean beds that have been dated as Late Cretaceous in age.

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