Centropyxis aculeata (Testate lobose amoebae) and associated diatoms from the intertrappean lacustrine sediments (maastrichtian) of central India: Implications in understanding paleolake ecology

Abstract

The Deccan Continental Flood Basalt (DCFB) sequence of India includes the volcanic flows of the Deccan Traps and the intertrappean sedimentary lacustrine deposits that lie in between the flows. The well-preserved arcellinidan taxon Centropyxis acu-leata and associated diatoms on their tests are described for the first time in India from palaeolake sediments (Maastrichtian) of the Bagwanya Intertrappean sequence in Central India. Laminated shales and clays yielded diatoms, arcellinidans and sponge spicules, whereas other lithofacies composed mainly of black cherts yielded marker palynomorphs of Maastrichtian age. Diatoms isolated from the sediments include the poorly preserved centric diatom Aulacoseira and other pennate diatoms. Sponge spic-ules are present in this microfossil assemblage and show similarity with the extant genus Corvospongilla. Five diatom taxa, Cyclotella sp. (? meneghiniana); Pantocsekiella sp. (? ocellata); Achnanthes sp. (? brevipes); Diadesmis sp. (? confervacea); and Oricymba sp. (? tian-muensis), found associated with the tests of Centropyxis aculeata have been described. Palaeoecological interpretation of this palaeolake is based on the information derived from lithology, arecllinidans, diatoms and the palynomorphs. Bagwanya Palaeolake was a perennial, warm water, well oxygenated and very low salinity lake, surrounded by tropical to subtropical terrestrial and aquatic plants along its coast and also under shallow waters. The environment in this lake was under stress due to ongo-ing and extensive volcanism in the region, leading to SO2 and CO2 outgassing. Xeno-somes of sand and various species of diatoms on the test of Centropyxis aculeata indicate that the shallow benthic environments of the lake had a sandy substrate.