Elemental concentration of U, Th and K in tectonically active regions of Khari River basin, Kachchh, Western India

Abstract

Elemental concentrations of U, Th and K were determined using alpha counter and gamma-ray spec- trometer to study the natural environmental radiation over a wide tectonically active region of Khari river basin in Kachchh, western India. Activity concentrations of 238 U, 232 Th and 40 K estimated in different types of sediments deposited/relocated in the Khari river cliff due to neotec- tonic activity near Bharasar (2311 0 36.5 00 N, 6935 0 22.6 00 E) and Kodki transverse fault (2314 0 37.37 00 N, 6934 0 59. 99 00 E) near Bhuj in the Khari River basin. Distribution of these radioactive elements on the earth's surface is con- trolled by geological features like faults, shear zones, metamorphism etc. Mainland Kachchh has two E-W trending major faults viz. Kachchh Mainland Fault and Katrol Hill Fault, which exhibits evidences of active tec- tonics during Quaternary. Kodki transverse fault is one of several NNE-SSW and NNW-SSE trending transverse faults affecting the Katrol Hill Range. The River Khari flows from the Katrol Ridge and traverses through Creta- ceous sediments of Bhuj Formation (fluvio-deltaic, com- prised dominantly of sandstones) in its course. All the three tectonically relocated sediments in the Khari river cliff have similar 238 U and much lower 232 Th activity concen- tration values corresponding to the worldwide median values of 35 and 30 Bqkg -1 , respectively, while 40 K activity concentrations were quite lower for two sediments and almost similar for the scarp-derived colluvium com- pared to the worldwide median value of 400 Bqkg -1 . Kodki transverse fault, however, has higher 238 U and 232 Th and almost half of 40 K activity concentration values rela-