New paleomagnetic pole and magnetostratigraphy of the Cauvery Basin sediments, southern India
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Indian Academy of Sciences (0123456789().,-volV)(0123456 789().,-volV)
New paleomagnetic pole and magnetostratigraphy of the Cauvery Basin sediments, southern India M VENKATESHWARLU* CSIR-National Geophysical Research Institute, Hyderabad 500 007, India. e-mail: mamila˙[email protected] MS received 18 November 2019; revised 24 June 2020; accepted 11 July 2020
Magnetostratigraphy or magnetic polarity stratigraphy (MPS) is constructed with paleomagnetic parameters for the Campanian–Maastrichtian (Upper Cretaceous) onshore sediment sequences of the Cauvery Basin, southern India. Twenty-nine sedimentary outcrops in the vicinity of Ariyalur district of Tamil Nadu, India were studied using AF (5–150 mT) and thermal demagnetization (100–700C). The observed remanence carrier is attributed to hematite through rock magnetic experiments. The virtual geomagnetic pole (VGP) latitudes were computed using the acquired characteristic remanent magnetization (ChRM) directions. The mean ChRM produce Dm= 338, Im= –38, (a95=23.91, k = 15.73, N=60). The mean VGP is estimated at 51.33N, 292.71E deriving a paleolatitude of 21.3S. The constructed magnetic polarity stratigraphy (MPS) is correlated with the standard geomagnetic polarity time scale (GPTS). The composite MPS of these sequences comprises of 12 magnetozones (6 normal and 6 reversed events) that are corroborated with Chron C33n to Chron C30n of the GPTS. The derived paleolatitude position from the present study places Indian subcontinent at little shallow southern latitudes indicating moderately higher drift velocities during Upper Cretaceous. Keywords. Paleomagnetism; magnetostratigraphy; Upper Cretaceous; Cauvery Basin; southern India.
1. Introduction The Cauvery Basin, southern India is a pericratonic basin located along the southeast coast of India formed as a consequence of the break-up of the Gondwana land during the late Jurassic (Rangaraju et al. 1993). After the break up of Gondwana, the Indian subcontinent remained isolated as an island continent and re-established based on biotic links with Africa, Madagascar, South America, and Asia during the Upper Cretaceous (Sahni and Bajpai 1988; Chatterjee and Scotese 1999; Khosla and Sahni 2003). ConBguration of the Indian plate changed during the Upper Jurassic and lower Cretaceous as it separated sequentially from Gondwana, east Gondwana,
Madagascar, and Seychelles Island (Chatterjee and Scotese 1999). The plate reconstructions suggest that India was an isolated island continent during the Cretaceous for more than 100 Ma until it docked with Eurasia in early Eocene (Barron and Harrison 1980; Smith 1988). In a recent hypothesis, Chatterjee and Scotese (2010) suggested that the Oman–Kohistan–Dras Island arc are the northern biotic link between Africa and India during the Upper Cretaceous period. During the Cenomanian period, India rifted away from Madagascar and headed northward at a speed of 18–20 cm/year covering a distance of about 6,000 km, and then slowed to 5 cm/year during early Eocene after a continental collisi
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