Shales from the off-shore drill core, west coast of India: studies on natural radioactivity and thermoluminescence

Natural radioactivity (U, Th and K by gamma spectrometry) and thermoluminescence studies were carried out on twenty-two core samples (250 m to 2540 m depths) consisting of shales and limestones from the Arabian Sea off the west coast of India. The radioactivity values (Th, U and Th/U) of the shale samples correspond to that of marine shales and the limestone data agree with the values found for marine black shales. An abrupt break at 1620 m depth in the K/Th and K/U ratios was observed, which was also apparent in TL data. This could be a consequence of the major fault in the west coast resulting in the change of depositional environment and/or change in provenance of the sediments