Eocene foraminiferal biofacies in Kutch Basin(India) in context of palaeoclimate and palaeoecology  

作　　者：Sonal Khanolkar Pratul Kumar Saraswati 

机构地区：[1]Department of Earth Sciences, Indian Institute of Technology Bombay, Mumbai 400076, India [2]Department of Earth Sciences, Indian Institute of Technology Kanpur, Kanpur 208016, India

出　　处：《Journal of Palaeogeography》2019年第3期209-224,共16页古地理学报（英文版）

基　　金：University Grants Commission(UGC);India for providing the funds to carry out the research work

摘　　要：The Eocene Epoch passed through multiple hyperthermal events and recorded highest temperatures in the Cenozoic. Very few studies from Eocene palaeotropical sites have recorded changes in shallow marine foraminiferal assemblages. The present study investigates the foraminiferal biofacies of shallow marine successions from a palaeotropical site in western India (Kutch Basin) to understand the palaeoclimate and its impact on the ecology of foraminifera. The sections were biostratigraphically con strained using planktic and larger benthic foraminifera. Four biofacies are recognized by detrended correspondence analysis of the sample-wise distribution of foraminifera. Low diversity and dwarfed foraminifera characterize Bulimina-Chiloguembelino biofacies (SBZ5/6-SBZ10), corresponding to the interval of Paleocene-Eocene Thermal Maxima (PETM) and Eocene Thermal Maxima 2 (ETM 2). Rectilinear benthic foraminifera and biserial and triserial planktic foraminifera, typical of high runoff, upwelling or eutrophic conditions, are dominant taxa in this biofacies. The specialist taxa increased significantly in Asterigerina-Cibicides biofacies, corresponding to SBZ11 (Early Eocene Climatic Optimum, EECO), and the environment became oligotrophic. The Jenkinsina-Brizalina biofacies (E12) is distinguished by foraminiferal assemblage ecologically like that of Bulimina-Chiloguembelina biofacies. It is characterized by high abundance of rectilinear benthic foraminifera and bloom of triserial planktic foraminifera, suggesting eutrophy and high runoff at the initiation of Middle Eocene Climatic Optimum (MECO). The foraminifera were more diverse and abundant in Cibicides-Nonion biofacies. The highly diverse larger benthic foraminiferal assemblage in this biofacies, signify warm and clear-water oligotrophic sea that promoted the development of platform carbonate in Kutch Basin and other basins in western India. The EECO and MECO did not have an adverse impact on shallow marine foraminifera, and particularly the larger benthic foraminifera attThe Eocene Epoch passed through multiple hyperthermal events and recorded highest temperatures in the Cenozoic. Very few studies from Eocene palaeotropical sites have recorded changes in shallow marine foraminiferal assemblages. The present study investigates the foraminiferal biofacies of shallow marine successions from a palaeotropical site in western India(Kutch Basin) to understand the palaeoclimate and its impact on the ecology of foraminifera. The sections were biostratigraphically constrained using planktic and larger benthic foraminifera. Four biofacies are recognized by detrended correspondence analysis of the sample-wise distribution of foraminifera. Low diversity and dwarfed foraminifera characterize Bulimina–Chiloguembelina biofacies(SBZ5/6–SBZ10), corresponding to the interval of Paleocene–Eocene Thermal Maxima(PETM) and Eocene Thermal Maxima 2(ETM 2). Rectilinear benthic foraminifera and biserial and triserial planktic foraminifera, typical of high runoff, upwelling or eutrophic conditions, are dominant taxa in this biofacies. The specialist taxa increased significantly in Asterigerina–Cibicides biofacies, corresponding to SBZ11(Early Eocene Climatic Optimum, EECO), and the environment became oligotrophic. The Jenkinsina–Brizalina biofacies(E12) is distinguished by foraminiferal assemblage ecologically like that of Bulimina–Chiloguembelina biofacies. It is characterized by high abundance of rectilinear benthic foraminifera and bloom of triserial planktic foraminifera, suggesting eutrophy and high runoff at the initiation of Middle Eocene Climatic Optimum(MECO). The foraminifera were more diverse and abundant in Cibicides–Nonion biofacies. The highly diverse larger benthic foraminiferal assemblage in this biofacies, signify warm and clear-water oligotrophic sea that promoted the development of platform carbonate in Kutch Basin and other basins in western India. The EECO and MECO did not have an adverse impact on shallow marine foraminifera, and particularly the larger benthic foraminife

关 键 词：Hyperthermal events Shallow marine Morphogroups Carbonate platform Stable isotopes EOCENE KUTCH BASIN 

分 类 号：P[天文地球]