Biostratigraphy and depositional environment of the Miocene limestone bed of Baripada, Mayurbhanj district, Odisha: Foraminiferal, sedimentological and bulk organic geochemical evidences

摘要

AbstractBaripada Marine Beds (BMB) have been studied extensively in terms of its mega fossil content. However, not much has been discussed about the foraminiferal content and the organic matter assemblage in these beds. The fossiliferous sequence of BMB consists of sandstone, shale and limestone units. The present study is persued on the limestone unit of BMB. Foraminiferal, thin section and rock-eval pyrolysis studies were performed on the 33 surface samples collected from five sections of Jamdapal and Mukurmatia region along the Budhabalang river bank. Foraminifera are less abundant in the samples of Jamdapal, whereas Mukurmatia is comparatively rich. First appearance datum ofGloborotalia menardii[ranges since middle Miocene (12.6 Ma); FAD at planktic foraminiferal zone N12] and last appearance datum ofNeogloboquadrina continuosa[ranges between early Miocene (23.2 Ma) to late Miocene (8.3 Ma); FAD at planktic foraminiferal zone N4B and LAD at N16] together suggest that the limestone unit was deposited in between 12.6 to 8.3 Ma within the upper Miocene. Also, the association of shallow water benthic foraminifera (Species ofAmmonia,Asterorotalia,Bolivina,Buliminella,Cibicides,Challengerella,Criboelphidium,Cribononion,Elphidium,Hanzawaia,Nonionella) and planktic foraminifera (Globigerina falcoensis,Globigerina woodi,Globorotalia menardii,Neogloboquadrina contin