Litho-Biostratigraphy and Depositional Environment of Albian-Maastrichtian Sedimentary Succession of Cauvery Basin in Ariyalur Area

Abstract

AbstractCretaceous sequences of the Cauvery Basin serve as an analogue to understand the subsurface successions. In this area, the distribution of hydrocarbon reservoir and source rock facies was profoundly influenced by relative sea level changes amplified by rifting and related tectonic activities. Of particular interest are the outcrop sedimentary strata exposed in and around Ariyalur area of Tamil Nadu that emulate subsurface strata. The first marine transgression close to Aptian/Albian boundary at the western margin of the basin terminates the syn-rift tectonic phase. Two regional tectonic episodes of global significance, driven by the activity of mantle plumes, are well documented in the basin. A major basinal uplift during late Turonian caused by Marion hot mantle plume resulted in widespread subaqueous volcanism in the southern part of the Cauvery Basin. This uplift also led to relative sea level (RSL) fall of about 100 m in Cauvery Basin, in tune with the global sea level fall, and an unconformity of a magnitude of 2.3 Ma. This volcanic episode also resulted in Madagascar detachment from India. The reunion mantle plume that led to Deccan volcanism in central India resulted in the E-SE tilt of the Cauvery Basin during upper Maastrichtian (CF1-CF3 zones). This tilt caused a sea level fall of about 80 m and lateral withdrawal of shoreline by about 50 km developing a major erosional unconformity ranging in the magnitude of ~1.8–30 Ma. The magnitude of the RSL corresponded well with global sea level fall. This sea level fall caused widespread development of canyon features in the Cauvery Basin, resulting in differential subaqueous erosion. The globally significant ocean anoxic events viz. OAE-1b, OAE-1d, OAE-2 and OAE-3 are fairly discernible in the Cauvery Basin. The new isotopic palaeotemperature data suggests that southern India and Madagascar were located apparently in middle latitudes within the tropical-subtropical climatic zone during Albian and early Maastrichtian. The magnitude of hiatus across K-T boundary varying from 0 to 30 Ma is estimated based on planktic foraminifera for subsurface sections. The magnetostratigraphy of outcrop sediments reveals 13 magnetozones in the Late Cretaceous sedimentary strata.KeywordsCauvery basinCretaceousGeological eventsAriyalurPaleogeogeographyBiostratigraphyMagnetostratigraphy