Journal of Geological Society of India (Online archive from Vol 1 to Vol 78)

U. K. Shukla ¹, Z. A. Khan ², I. B. Singh ¹

Affiliations
1 Department of Geology, Lucknow University, Lucknow - 226 007, IN
2 Uttar Pradesh, Khanij Bhawan, 2 Way Road, Lucknow - 226001, IN

Abstract

Cyclic characteristics of lithofacies of the shallow marine Bhuj Sandstone were studied statistically, using embedded Markov chain analysis and the concept of entropy. Data came from thirteen measured sections. The upward transmissions from one sedimentary lithofacies to another are plotted on a 5×5 matrix and a transition tree is constructed. Results strongly suggest that the Bhuj Sandstone was influenced by a Markovian mechanism and accumulating in well-defined depositional environments; the vertical distribution of lithofacies was controlled by a number of natural processes. The preferential upward transition path of lithologic and depositional envitonment changes are as follows: Carbonaceous siltstone/shale (A) (Coastallagoon) → Coarse-grained cross bedded Sandstone (8) (Estuarine channel) → interbedded sandstone siltstone (C) (Tidal flat-tidal channel) → silty sandstone (D) (Sandflat - shoal) → Bioturbated sandstone (E) (Shelf Sheet sand) → Carbonaceous siltstone/shale (A) (Coastal lagoon).

This sequence is an asymmetrical cycle. It can be identified into a progradational event (lithofacies A-D) and a transgressive event (lithofacies E). The statistical results concur with the sedimentological evidence for depositional environments.

Entropy plots of the E^(pre) and E^(post) values of each lithological state correspond to the type A-4 category (Hattori, 1976), signifying lower and upper truncated asymmetrical cycles. The values of E (system) fall just on the boundary of the area allocated for the neritic environment. The area occupied by the Bhuj Sandstone evidently represents the domain of deposits of a coastal complex of estuary, lagoon and tidal flat environments, deposits for which Hattori had no data base.

Keywords

Sedimentology, Bhuj Sandstone, Markov Analysis, Kachchh Basin, Gujarat.

Full Text

     

Bengt R. Ingre ¹, S. C. Srivastava ¹, P. N. Mehrotra ², Z. A. Khan ², K. C. Pant ², K. K. Srivastava ²

Affiliations
1 United Nations Development Programme, IN
2 U. P., IN

Abstract

The application of VLF has acquired an important role in the search for sulphide ores, groundwater and the detection of geologic faults, in the western countries during the past one decade. This method has now been tried for the first time in India over anomalies known from other type of EM measurement and the results indicate a good correlation. The advantage of the VLF method is that it requires only one operator and is, therefore, considerably cheaper and faster than any other EM method.

Full Text

   

Z. A. Khan ¹, Ram Chandra Tewari ²

Affiliations
1 Directorate of Geology and Mining, Khanij Bhawan, Lucknow - 226 001, IN
2 Department of Geology, Sri J.N.P.G. College, Lucknow - 226 001, IN

Abstract

The quantitative relationships between lithological variables of Early Permian Barakar coal measures of western Singrauli Gondwana sub-basin are investigated using principal component analysis in an attempt to reveal simple relationships undetected by conventional quantitative methods. The results not only confirm and amplify those of the simple regression analysis described in Casshyap et.al. (1988), but are also interpreted in terms of evolution of coal swamps. If the total thickness of strata, total thickness of clastic sediments, total thickness of coal seams, number of sandstone beds, number of shale beds, number of coal seams and clastic ratio are considered, the first three components accounts for 80% of the total variance and the lithological variables generally fall into two groups. One group contains the first four variables, namely, total thickness of strata, total thickness of sandstone, total thickness of shale and total thickness of coal seams, all of which have basin-like regional patterns of sedimentation linked to net subsidence. The other group of variables, which are somewhat less closely related to net subsidence such as number of sandstone beds, number of shale beds and number of coal seam. The sand/shale ratio and clastic ratio are dependent on the other variables and seem to be unrelated to net subsidence. The principal component results, at best in geological term, may be explained by the to and fro lateral migration of a river channel across its flood plain coupled with a gradual isostatic adjustment of the basin floor in response to the weight of the sediments and differential subsidence through space and time.

Keywords

Principal Component Analysis, Barakar Coal Measures, Singrauli Sub-Basin, Gondwana.

Full Text