Zahid A. Khan

Entropy in Markov analysis of late paleozoic cyclical coal measures of East Bokaro basin, Bihar, India

Randomness in the occurrence of lithologies in a cyclical succession is evaluated in terms of entropies which can be calculated from a Markov chain matrix. Two types of entropies are linked with every lithologic state; one is the entropy before deposition E(pre)and the other is that after deposition E(post),which together form an entropy set. The entropy sets for pebbly sandstone, sandstone, shale, and coal for the Karharbari coal measures, and sandstone, shale, carbonaceous shale, and coal for the Barakar coal measures were plotted separately and compared with Hattoris idealized plots. These coal measures probably were essentially of symmetrical cyclical pattern (Type-B)of Hattori. The entropy of the whole sedimentation unit readily fits under the broad framework of fluvial cycles.

Net subsidence and number of cycles; their interrelationship in different Permian Gondwana basins of peninsular India

Abstract Seven data sets were structured from subsurface lithologs of Permian Gondwana coal measures comprising the Karharbari, Barakar and Raniganj formations of the Koel-Damodar and Mahanadi basins of peninsular India. All three formations are fluvial in nature and composed largely of fining-upward cycles of clastic sediments capped by coal/carbonaceous shale. Simple linear regression lines and correlation coefficients were computed for total thickness of strata (net subsidence) and number of cycles in each data set. The strong positive relationships between total thickness of strata and number of cycles in Permian coal measures suggest that the fluvial cycles of Karharbari, Barakar and Raniganj are formed by intrabasinal mechanisms of channel migration, sedimentation and subsidence rather than tectonic events in the source area. The slopes of linear regression lines fitted to the data sets vary more than has hitherto been supposed and are classified into two categories. Three out of seven regression lines exhibit steeper slopes and they are closely similar in this respect to other Permian and Upper Carboniferous coal measures of Australia, Great Britain and Germany; the other four have gentler slopes. These dissimilarities in the slopes of regression lines are attributed to the differential rate of increase in the number of cycles with respect to the total thickness of the strata (net subsidence) as well as the differential subsidence of the Permian Gondwana Supergroup through space and time.

Sedimentological synthesis of permian fluviatile sediments of East Bokaro basin, Bihar, India

Abstract The early Permian Karharbari and Barakar formations of East Bokaro basin comprise the following lithofacies: Lithofacies A, consisting of monomictic cobble- and pebble-conglomerate including pebbly sandstone, with faint crossbeds; deposited mainly by high-velocity aqueous currents as channel-lag deposit or longitudinal bars. Lithofacies B, coarse to medium sandstone, profusely crossbedded; interpreted as channel facies formed by downcurrent migration of sand bars in low-sinuosity streams. Lithofacies C, mainly fine sandstone with interbedded siltstone, characterised by small-scale ripple-lamination; formed in a low-energy environment such as swale-fill and/or overbank deposits. Lithofacies D, including carbonaceous shale and coal, with lack-of-current structures, indicating quiet-water deposition; interpreted as backswamp and lacustrine deposits. The overall context of the Karharbari and Barakar assemblage with relative abundance of pebbly coarse sandstone in the former and fine clastics in the latter, the presence of fining-upward cycles, widespread development of tabular and trough crossbedding and sample to sample variation of foreset azimuths, all suggest a generally alluvial environment. Analysis of crossbedding dip azimuth and dimensional fabric suggest that the sediment milieu in either case consisted of streams flowing persistently from the south-southeast to north-northwest direction. It is inferred that the unidirectional system of streams flowing across the East Bokaro basin changes systematically in channel sinuosity through time.

Principal component analysis of lithologic variables in Early Permian Barakar coal-measures, western Singrauli Gondwana sub-basin of central India

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.

Structures and sequences in early Permian fluvial Barakar rocks of peninsular India Gondwana basins using binomial and Markov chain analysis

Cyclic characteristics of bed forms (sedimentary structures) of early Permian fluvial Barakar rocks are studied statistically, using quasi-independence Markov chain and entropy. The hierarchy of sedimentary structures confirms that the corresponding bed forms do not represent random depositional event and follow a definite pattern of Markovian mechanism in a predictable cyclic arrangement. The preferential upward transition of sedimentary structures that can be derived for the Barakar sandstone is scoured surface (Ss) → horizontal bedding (Sh) → planar cross-bedded sandstone (Sp) → trough cross-bedded sandstone (St) → ripple cross-lamination (Sr) → parallel lamination (Fl) → scoured surface (Ss). The sequence is an asymmetrical cycle and characteristic of the lateral accretion and aggradations of fluvial channels. Entropy analysis corroborate the above inference, and E (pre) vs E(post) plots for each sedimentary structure correspond to the type B category, suggesting lower and upper truncated asymmetrical cycles. Hydro-dynamically, the Barakar cycles represent a vertical sequence of bedding types which implies a steady upward decrease in the intensity of flow—from the upper flow regime in the lower part, the lower flow regime of moderate to high intensity in the middle part, and the lower flow regime of low to very low intensity in the upper part.

Problems in Accepting Plate Tectonics and Subduction as a Mechanism of Himalaya Evolution.

The available geological and structural data from Chaman fault and Indus-Tsangpo regions does not support the new global tectonic concept and the presence of suture zone between Indian and the northern landmass. Instead, it is suggested that the Indus-Tsangpo is a rift valley that appeared in the Triassic and became dormant in the Cretaceous, after a spurt of volcanic activity long before the supposed suturing in the Eocene. The paleontological evidences based on plants, marine and fresh-water invertebrates, insects and vertebrates indicate that Gondwanaland was never a separate entity. Paleoclimatic continuity was maintained over this landmass of India and Tibet from the Paleozoic through Cenozoic eras up to the Pleistocene Epoch. Similarly, the widespread glacial deposits of northern Tibet bespeak of a continental landmass extending from Peninsular India up to northern Tibet, and may be beyond. Thus, Pangaea existed till its breakup beginning in the Triassic and Tethys was an epicontinental sea from west Proto-Pacific to east Proto-Pacific. At no stage was it oceanic in character, although narrow shifting belts along and across it, became rift or geosynclines in the process of crustal development. Thus, the Tethys did not form a wide, funnel shaped gulf, opening into the Pacific as depicted in many reconstructions. On the other hand, the Himalayan sequence is dominantly nongeosynclinals sediments, and therefore, genetically different from such classic mountains as the Caledonian, Hercynian, Urals, and Aravallis etc. It is significant that the Himalayan orogeny was initiated in the Cretaceous, and the major episode was Eocene, i.e. earlier than the supposed collision, rules neither out continental collision and subduction nor even in geosynclines. However, the Himalayas, could, then, not have been borne due to collision of landmasses as suggested by plate-tectonics. Instead, they are an interplatform type of mountain range formed by vertical uplift, by intrusive magmas and gravity gliding played an important part too. Terrestrial gravity, seismic (including DSS), geodetic, geomorphologic and field tectonic studies independently and collectively support the above contention. The Himalaya along with some other ranges in Central Asia may be unique in Earth history, and all the mountain ranges of the past seem apparently to have been originated in geosynclines. The plate tectonic concept, however, considers the term geosynclines redundant.

A Critical Analysis of North-South Continuity of Landmasses across Indus-Yarlu-Tsangpo Suture Zone: Its Bearing on the Himalayan Evolution

Gondwana glaciations are well known from the India, and therefore the Pole must have lingered long enough in the subcontinent to deposit some 1600 m thick glacio-marine sediments in northern Tibet. Similarities of these deposits with those of basal Gondwana Talchir rocks indicate that India and Tibet (and hence the rest of Asia) were united in the Upper Carboniferous and Lower Permian. Further, paleo-biogeography of the region suggests their continuity through Permian, Triassic and Jurassic, and up to Cretaceous. The collision is supposed to have taken place in the Eocene-Miocene, and there should at least have been a very short time of compression at this stage. Instead, the immense batholiths intrusion in the area strongly suggests tension. Moreover, the ophiolites along the suture have yielded two different ages of emplacement, Jurassic-Lowest Cretaceous, and then a little later in Lower Cretaceous, i.e. the emplacement took place 100 Ma before the supposed collision in the Eocene. It is believed that the Indian Plate is progressively underthrusting the Tibetan Plate, though a large part of central and southern Tibet is traversed by active normal and transform faults and rift valleys, cutting across the Bongong-Nujiang and the Indus-Tsangpo suture zone and entering the Himalayan region imply tension all over the area, and not compression, that is expected from subduction/collision zone. Thus, the modern global plate tectonic concept and subduction/collision mechanism are thus, untenable for Himalaya evolution. Alternatively the Himalayas are formed under tensional regime by vertical uplift, intrusive magmas, boudins, sills sand dykes. Gravity gliding played an important role. The various geological arguments such as structure, paleo-biogeography, paleoclimate and volcanic history, including the presence of Tibetan glacial deposits therefore, do not convincingly support the concept of collision of two landmasses, as popularly believed today or by the plate convergence and the hypothetical subduction in this part of world. Even the Paleomagnetic data is replete with contradictory evidence. The collisional along the Indus-Tsangpo suture is, therefore, doubtful in as much as India has all along been adjacent to Tibet, certainly at least since the Ordovician, and hence a part of the great Pangaea landmass. The modern global plate tectonic concept and subduction mechanism are, thus, untenable for Himalayan evolution. The Himalaya is formed under tensional regime by vertical uplift and gravity sliding.

Origin of banded structure and coal lithotype cycles in Kargali coal seam of East Bokaro sub-basin, Jharkhand, India: Environmental implications

The Kargali seam of Early Permian Barakar cyclothems of East Bokaro sub-basin of Jharkhand, India is 12–30 m thick, splits into two parts, and extends throughout the length of the basin. It is made up of interbedded sequences and variable proportions of Vitrain, Clarain, Durain and Fusain. Application of embedded Markov chain model rejects the phenomenon of randomness in the repetition of coal lithotypes. The preferential upward transition path for coal lithotypes that can be derived for the Kargali top coal seam is: Vitrain → Clarain → Durain ↔ Fusain → Vitrain, and for the Kargali bottom coal seam is: Clarain ↔ Vitrain → Fusain → Durain → Clarain. By and large, the cyclic repetition of coal lithotypes is similar in the Kargali bottom and top seams. Among the noteworthy features are two-way transitions between Durain and Fusian in Kargali top and between Clarain and Vitrain in the case of Kargali bottom coal seam. Entropy analysis corroborates Markov chain and indicates the presence of type A-4 asymmetrical cycles of coal lithotypes.It is suggested that the banded structure of a coal seam is not a random feature and follows a definite cyclic pattern in the occurrence of coal lithotypes in vertical order and is similar to that described in Australian and European coal seams. Asymmetrical cyclic sequences are a normal, rather than an unusual condition, within coal seams. It is visualized that a gradual decline of toxic environment and ground water level resulted in the coal lithotype cycles in the Kargali seam of East Bokaro sub-basin. The close interbedding of Vitrain and Clarain is suggestive of seasonal fluctuation in anaerobic and aerobic conditions during peat formation.

Paleocurrents, Paleohydraulics, and Palaegeography of Miocene-Pliocene Siwalik Foreland Basin of India

Early Miocene-Pliocene Middle Siwalik Subgroup of Kuluchaur area, Uttarakhand, North India, comprises sheet-like, coarse to medium grained, cross bedded sandstone bodies and multistoreyed variegated mudstones. Paleocurrent study shows commonly unimodal and locally bimodal distribution and displays a high magnitude of resultant () oriented towards south-southwest (206°  ±  42.27°). Palaeochannel morphological attributes suggest that the depositing river system was about 230 m wide and 4.5 m deep. These broad, shallow, and low sinuous channels with extensive flood plain flowed on a steeper slope (0.00043 degrees) with flow velocity of 60–140 cm/sec. It is visualized that the immature Middle Siwalik rocks were deposited by southward flowing braided rivers transverse to the Himalayas, predominantly in the form of overlapping alluvial fans similar to those depositing sediments at present in the Indo-Gangetic plains. Fairly consistent fluvial palaeoslopes, together with enormous thickness of sediments, are evidences of rapid subsidence of the basin. We conclude that the paleogeography of Indian subcontinent established at the onset of Miocene-Pliocene Siwalik sedimentation is continuing till today.