Exposed outcrop sections were measured in the Mesri River and its tributary Kuej in the Mainland Gujarat region. The studied sections fall in the transition zone between uplands and pediments and thus can give important clues on the behavior of the river and its depositional regime. Mesri river is the first order tributary of the major Mahisagar River south of which lies the oil rich Cambay graban.
The present study includes detailed description of the section, graphic log of the measured section and outcrop total gamma ray measurements at an interval of 15cm. Onsite gamma ray has provided a ready reference for the fining upward cycles with their top and bottom bounding surfaces which is otherwise very difficult to pickup from the exposed section.
The high and low spikes within the fining upward sequences may indicate the sudden change in the channel velocities and thus in grain size. The variation in gamma count can be related to the compositional variations but in this case since the source rocks are similar throughout the drainage basin so the factor of compositional variations can be negated. Both the exposed sections show complex amalgamated fluvial channel fills with moderately to poorly developed flood plain deposits. Most of the deposits are thought to be results of braid and point bars. Various types of calcretes from soft friable to very hard nodular and ferromanganese nodules were commonly seen throughout the studied sections.
Most of the section is moderately to poorly pedogenised. Slabbed sections of the calcretes were studied to see the internal structures. The calcretes offered new insights on the prevailing climatic conditions during the formation of the entire set of deposits. Insitu gamma ray measurements proved useful in identifying the lithofacies variations.