CORRELATION OF FOUR MAGNETOSTRATIGRAPHICALLY CONSTRAINED SECTIONS OF MIOCENE BHUBAN FORMATION OF SURMA BASIN IN MIZORAM, INDIA PAUL LALNUNTLUANGA 1* , J. MALSAWMA 1 , C. LALREMRUATFELA 1 , R.P.TIWARI 1 and S.J. SANGODE 2 1 DEPARTMENT OF GEOLOGY, MIZORAM UNIVERSITY, AIZAWL-796004, MIZORAM 2 DEPARTMENT OF GEOLOGY, UNIVERSITY OF PUNE, GANESHKHIND, PUNE, INDIA *Corresponding author’s e-mail: paultluanga@gmail.com ABSTRACT In the present study, four magnetostratigraphically constrained isolated sections in the Mizoram part of the Surma basin, namely, Kolasib-Rengtekawn (KR) section in Kolasib district; and Bawngkawn–Durtlang (BD); Tuirial and Sairang sections in Aizawl district of Mizoram have been successfully correlated. The youngest magnetozone of BD section i. e. C5Cn magnetozone (16.726-16.014 Ma) has also been recorded in the KR section and both the sections expose Middle Bhuban Unit of Bhuban Formation, Surma Group. Thus KR section is correlated with the upper part of BD section. Three younger magnetozones, viz., C4 An (9.025 - 8.699 Ma), C4Ar.1n (9.308 - 9.230 Ma) and C4Ar.2n (9.642 - 9.580 Ma) of Tuirial section have been delineated in the Sairang section and both the sections belong to Upper Bhuban Unit. Thus Sairang section is correlatable with the upper part of Tuirial section. Stratigraphically also, KR and BD sections are older than the Tuirial and Sairang sections. Similar pattern in rate of deposition has been noticed in the KR and BD sections and Turial and Sairang sections. The study thus demonstrates that magnetostratigraphy may emerge as the reliable tool for regional correlation of isolated successions of varied litho-stratigraphic units in the Surma basin. An integrated study on litho-, bio- and magnetostratigraphy along with sedimentology is needed to reconstruct the tectono-depositional history of the basin and biotic evolution in it. Keywords: Magnetostraigraphy, Surma basin, Bhuban Formation, Mizoram, regional correlation. INTRODUCTION Surma succession is exposed in a large area extending southward from the centre of the Kohima syncline through Surma Valley, Tripura and Chittagong to Indo-Myanmar Range. Mizoram is considered as the depocentre for the Surma basin as thickest sedimentary succession is developed in Mizoram part of this basin. The major lithostratigraphic unit exposed in the Mizoram State is the Surma Group of Miocene age represented by Bhuban and Bokabil Formations. Lithologically, Bhuban Formation is further subdivided into Lower, Middle and Upper Bhuban Units. Main rock facies of this formation are sandstone, siltstone, shale, mudstone and their admixtures in various proportions and a few pockets of shell limestone, calcareous sandstone and intraformational conglomerate (Tiwari and Kachhara, 2003). Previously, attempts were made to classify and correlate the Surma succession based on lithology by Evans (1932), sand/shale ratio by Holtrop and Kaizer (1970) and with heavy mineral assemblages by Sinha and Sastri (1972). In spite of the success of such attempts in broad stratigraphic correlations and in regional mapping (Dasgupta, 1982), these have limited applications in the correlations of the isolated sections of the Surma Group, both at local as well as on regional scale. Extensive palaeontological studies were performed in the Bhuban Formation comprising bivalves, gastropods, echinoids, crab, corals, foraminifers, ichnofossils and fishes (Rajkonwar et al., 2013; Jauhri et al.,. 2003; Lokho and Raju, 2007, 2011; Srivastava et al., 2008; Tiwari, 2001, 2006; Tiwari and Kachhara, 2000,Tiwari and Mehrotra, 2002, Tiwari and Victor, 2012; Tiwari et al. 1997, 2011, 2013; and Victor et al . 2011).These fossil assemblages have broadly indicated the changes in depositional environments throughout the stratigraphy with shallow marine, near shore, lagoonal through coastal to fluvial (Malsawma et. al., 2010). Such efforts have however not yielded desirable results in terms of fine resolution SPECIAL PUBLICATION OF THE PALAEONTOLOGICAL SOCIETY OF INDIA No. 5; February, 2014; ISBN: 978-81-926033-2-2; pp. 87-100