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2.
The Permo-Carboniferous Talchir Formation in the southeastern part of the Talchir basin is represented by about 260 m thick clastic succession resting on the Precambrian basement rocks of the Eastern Ghats Group. The succession is tentatively subdivided into four lithostratigraphic units, namely A-I, A-II, B and C from base to top. Unit A-I comprises mud-matrixed, very poorly sorted diamictites and interbedded thin sandstone and mudstone yielding dropstones. They reveal deposition in a proglacial lake environment in which ice rafting and suspension sedimentation, as well as meltwater-underflow processes, produced variety of facies. The succession of unit A-II is dominated by pebble to boulder conglomerates and sandstones. They were deposited mostly from various kinds of high-energy sediment gravity flows, both subaerial and subaqueous, and formed steep-faced fan-delta on the margin of the basin. Unit B demonstrates turbidite sedimentation in lake-margin slope and base-of-slope environments, in which a sublacustrine channel-fan system developed. The lake-margin slope was dissected by channels which were accompanied by overbank and levee deposits. Sediments delivered from the mouth of a channel were deposited at the base-of-slope, forming a fan lobe which prograded onto the lake basin floor. Unit C dominantly consists of mudstone with intercalations of siltstone and sandstone and forms a large-scale coarsening-upward deltaic sequence eventually covered by the fluvial deposits of the Karharbari Formation.Following the glacially influenced sedimentation, the Talchir succession shows a vertical facies progression suggesting gradual deepening of the lake basin and eventual filling up of it due to rapid delta progradation. Such a succession represents deglacial control on basin evolution during the Talchir time. In the initial stage of glacial recession, collapse of a glacier and failure of montane glacial lakes frequently occurred and gave rise to generation of a highly sediment-laden debris flow and a catastrophic flood, which brought abundant coarse clastics into the lake and built a fan-delta on the basin margin. The continued recession and disappearance of glacier resulted in abundant supply of ice-melt water into the graben as well as eustatic sea-level rise, being the cause of the rise in lake-level. Subsequent rapid delta progradation and eventual filling-up of the lake basin suggest rapid lake-level fall after deepening of lake basin. It was possibly caused by the regional uplift due to post-glacial isostatic rebound. Rapid draining of lake water through the graben gave rise to the establishment of an axial drainage system which rapidly filled the lake basin in form of an axially fed delta. 相似文献
3.
The cyclic arrangement of lithofacies of the Karharbari Formation of the Damuda Group from a part of the Talchir Gondwana
basin has been examined by statistical techniques. The lithologies have been condensed into five facies states viz. coarse-,
medium-, fine-grained sandstones, shale and coal for the convenience of statistical analyses. Markov chain analysis indicates
the arrangement of Karharbari lithofacies in form of fining upward cycles. A complete cycle consists of conglomerate or coarse-grained
sandstone at the base sequentially succeeded by medium-and fine-grained sandstones, shale and coal at the top. The entropy
analysis categorizes the Karharbari cycles into the C-type cyclicity, which is essentially a random sequence of lithologic
states. Regression analysis undertaken in the present study indicates the existence of sympathetic relationship between total
thickness of strata (net subsidence) and number and average thickness of sedimentary cycle and antipathic relationship between
number and average thickness of sedimentary cycle. These observations suggest that cyclic sedimentation of the Karharbari
Formation was controlled by autocyclic process by means of lateral migration of streams activated by intrabasinal differential
subsidence, which operated within the depositional basin and the channels carrying coarse grade clastic sediments, which make
the cycles thicker, tend to be more common in the areas of maximum subsidence. Clastic sediments issued from the laterally
migrating rivers interrupted the cyclic sedimentation of the Karharbari Formation in many instances. 相似文献
4.
Cyclic characters of Karharbari, Barakar and Barren Measures Formations of the Talchir Gondwana basin have been studied in the subsurface logs statistically using first order Markov chain and entropy analyses. Results strongly suggest that the sediments of these formations were deposited by Markovian mechanism and all the three formations represent cyclic sedimentation. The complete cycles of all the three formations are identical and exhibit fining-upward character. Each complete cycle starts with a thin conglomerate or pebbly to coarse-grained sandstone at the base and successively followed by medium- and fine-grained sandstones, interbedded sandstone-shale, shale and terminates with a coal seam at the top. There are, however, minor variations of facies transition in different formations. Entropy analysis also corroborates these findings. The upward sequence of facies states, which is stationary at individual localities, is non-stationary over the entire area. Broad regional variations in the depositional environment, that are not significant at the local scale, may be the plausible explanation. The Karharbari, Barakar and Barren Measures sediments of the Talchir Gondwana basin fit suitably into the concept of fluvial cycles. 相似文献
5.
The lowest unit of the Talchir Formation of Talchir Basin, Orissa, was described by pioneer workers as the ‘basal boulder
bed’. In an attempt to explain the co-existence of gravel and clay, materials of contrasting hydraulic properties, a probable
situation resembling the effects of the action of ground-ice enabled boulders to be carried down by sluggish currents resulting
in an intermixture of large boulders and fine mud was conceived. Misinterpretation of this conclusion led to a general tendency
to describe the ‘basal boulder bed’ as ‘glacial tillite’. However, the unit described as ‘basal boulder bed’ is actually represented
by a matrix rich conglomerate with pockets of normally graded silty clay. The present study reveals that the depositional
imprints preserved in this part of the sedimentary succession indicate emplacement of successive debris flows generated through
remobilization of pre-existing unconsolidated sediments. Small pockets of fine-grained turbidites presumably deposited from
the entrained turbidity currents associated with the debris flows suggest the composite character of the debris flow deposit. 相似文献
6.
The Permian Barakar Formation in the Mohpani coalfield, Satpura Gondwana basin, is composed of three broad lithologies that occur repetitively and are iterdigitated: (1) several metres thick coarse- to medium-grained sandstone bodies with scoured bases, (2) 5-20 m thick medium- to fine-grained sandstone bodies and (3) 5-20 m thick mudstone-dominated packages with variable proportions of centimetre- to decimetre-scale, fine- to medium-grained sandstone, carbonaceous shale and coal. The Barakar strata were previously interpreted as deposits of braided rivers and associated inter-channel flood basin in a continental setting. However, this study recognizes signatures of tidal current from the mudstone-dominated packages implying marine influence during Barakar sedimentation. The mudstone-dominated sediment bodies are the focus of this paper and comprise of three lithofacies that bear imprints of tidal processes during Barakar sedimentation: (1) heterolith, (2) sandstone, and (3) coal-carbonaceous shale, which alternate with one another within individual bodies. The heterolithic facies show interlayering of sandstone and claystone resembling flaser, wavy and lenticular bedding, as well as pinstripe stratification. Successive sandstone-mudstone couplets indicate periodic waxing and waning of flows. Within individual heterolithic packages, the sandstone:claystone ratio along with the bedding style, varies cyclically upwards giving rise to alternate sandstone-dominated and claystone-dominated intervals suggesting tidal velocity fluctuation reflective of spring-neap lunar cycle. Thickness plots of successive sand-mud couplets also reveal cyclic variation with a conspicuous periodicity of around 12 couplets per cycle, which corroborates the spring-neap-spring (or neap-spring-neap) lunar cycle. Presence of abundant desiccation cracks indicates periodic emergence and points towards an intertidal setting. The sandstone facies is characterized by a variety of wave-generated features such as bundled and chevron upbuilding of lamina, bi-directional foreset orientations, offshooting and draping laminae, scour-and-drape feature, swollen lens-like geometries suggesting their emplacement under storm-induced combined-flow on the tidal-flat. The coal-carbonaceous shale facies represent supratidal marsh environment. 相似文献
7.
In peninsular India, Gondwana strata are disposed linearly as strings of isolated basins conforming to the trend of the present day Koel–Damodar, Son–Mahanadi and Prahnita–Godavari river valleys. There are seven exposed and one concealed Gondwana basins/outliers in Orissa belonging to the Son–Mahanadi valley system. The present study is concerned with the consanguinity of the Talchir and Ong-river basins of Orissa. Similarity and dissimilarity of palaeocurrent population in these two basins were taken into consideration to test the consanguinity of the basins under consideration. Statistical analysis suggests that the sampled palaeocurrent data of the same formation belong to the same population when considered for both basins. In geologic terms, the basin parameters were identical when considered for either the Talchir or the Karharbari Formation that proves the consanguinity of both the basins and the possible existence of a master basin that encompassed other sister Gondwana basins in Orissa. 相似文献
8.
The Athgarh Formation is the northernmost extension of the east coast Upper Gondwana sediments of Peninsular India. The formation of the present area is a clastic succession of 700 m thick and was built against an upland scarp along the north and northwestern boundary of the basin marked by an E-W-ENE-WSW boundary fault. A regular variation in the dominant facies types and association of lithofacies from the basin margin to the basin centre reveals deposition of the succession in an alluvial fan environment with the development of proximal, mid and distal fan subenvironments with the distal part of the fan merging into a lake. Several fans coalesced along the basin margin, forming a southeasterly sloping, broad and extensive alluvial plain terminating to a lake in the centre of the basin. Aggradation of fans along the subsiding margin of the basin resulted in the Athgarh succession showing remarkable lateral facies change in the down-dip direction. The proximal fan conglomerates pass into the sandstone-dominated mid-fan deposits, which, in turn, grade into the cyclic sequences of sandstone-mudstone of the distal fan origin. Further downslope, thick sequence of lacustrine shales occur. The faulted boundary condition of the basin and a thick pile of lacustrine sediments at the centre of the basin suggest that tectonism both in the source area and depositional site has played an important role throughout the deposition of the Athgarh succession of the present area. The vertical succession fines upward with the coarse proximal deposits at the base and fine distal deposits at the top, suggesting deposition of the succession during progressive reduction of the source area relief after a single rapid uplift related to a boundary fault movement.The NW-SE trending fault defining the Son-Mahanadi basin of Lower Gondwana sediments are shear zones of great antiquity and these were rejuvenated under neo-tensional stress during Lower Gondwana sedimentation. The E-W-ENE-WSW trending fault of the Athgarh basin, on the other hand, define tensional rupture of much younger date. In the Early Cretaceous period, there was a reversal of palaeoslope in the Athgarh basin (southward slope) with respect to the Son-Mahanadi basin (northward slope). During the phase drifting of the Indian continent and with the evolution of Indian Ocean in the Early Cretaceous period, the tectonic events in the plate interior was manifested by formation of new grabens like the Athgarh graben. 相似文献
10.
The trace fossil assemblages of the ice-marginal shallow marine sediments of the Talchir Formation (Permo-Carboniferous), Raniganj Basin, India, record the adverse effect of extreme climatic conditions on biota. The glaciomarine Talchir succession starts with glacial sediments near the base and gradually passes to storm-laid shallow marine sediments up-section. The fine-grained storm sediments host abundant trace fossils. Although the studied ichnites characteristically show marginal marine affinity, the ichnodiversity and bioturbation intensity suggest a lower than normal shallow marine trace fossil population. Further, endobenthic annelids, worms and crustaceans are identified as dominant trace-makers. Sediment reworking near the ice-grounding line, extremely cold climate, high-energy storm sedimentation and anomalous water chemistry hindered organic colonization during the early phases of Talchir sedimentation. Later, climatic amelioration ushered in a favourable ambience for the benthic community to colonize within or beyond the storm weather wave-base in the outer shoreface–shelf environment. Fluctuating storm energy dominantly controlled the availability and influence of other environmental stimuli in the environment, and thus, governed the distribution, abundance and association of the studied ichnites. However, impoverished ichnodiversity, sporadic distribution of the traces, overall smaller burrow dimensions, absence of body fossils, dominance of worms and annelids as trace-makers all indicate a stressed environmental condition, induced by cold climate and lowered marine salinity due to influx of glacier melt-out freshwater during climatic amelioration, in the Permo-Carboniferous ice-marginal sea. 相似文献
11.
Oriented cylindrical cores of rock samples were collected from the Talchir and Barakar formations of the Lower Gondwana Supergroup of the Raniganj Basin exposed in and around Kalyaneshwari and Maithon areas. The cores (2.54 cm diameter and 2.2 cm height) were studied in the low field anisotropy of magnetic susceptibility (AMS) measurement to determine the nature of magnetic fabrics, to correlate it with the sedimentological characteristics and to determine the palaeocurrent patterns. The results derived from the statistical parameters (especially the q-factor), the shapes of the susceptibility ellipsoids and directional data of the AMS indicate that the magnetic fabrics within the studied units are primary (depositional) and are correlatable form the palaeoenvironmental features. The orientation of the maximum ( K1), intermediate ( K2) and minimum ( K3) susceptibility axes is dispersed on the lower hemisphere equal area diagram rather than strong clusters which is not because of secondary (tectonic) influence but due to the moderate to high-energy environment of deposition of the sediments in the studied units. Based on the q-factor (which is 0.581 for Barakar Formation and 0.565 for Talchir Formation which are both <?0.7), it is suggested the AMS indicates that the imbrication of the K1 axis is the indicator of palaeocurrent. Also, the magnetic foliation (average value?=?1.255) exceeds the magnetic lineation (average value?=?1.107) and the shape parameter exceeds 0 in most cases pointing towards an oblate fabric. The palaeocurrent in the present study as indicated by the K1 axis imbrication is very similar in both the units under study and is due SW. However, apart from this precise palaeocurrent direction, there exists a certain degree of randomness of the susceptibility axes which are very clear indication of corresponding depositional environments. 相似文献
12.
Basal part of the Gondwana Supergroup represented by Talchir and Karharbari Formations (Permo-Carboniferous) records an abrupt
change-over from glacio-marine to terrestrial fluviolacustrine depositional environment. The contact between the two is an
unconformity. Facies analysis of the glacio-marine Talchir Formation reveals that basal glaciogenic and reworked glaciogenic
sediments are buried under storm influenced inner and outer shelf sediments. Facies associations of the Karharbari Formation
suggest deposition as fluvio-lacustrine deposits in fault-controlled troughs. An attempt has been made in this paper to explain
the sedimentation pattern in Talchir and Karharbari basins, and the abrupt change-over from glacio-marine to terrestrial fluviolacustrine
depositional environment in terms of glacio-isostacy. 相似文献
13.
The succession of lithofacies of a part of the Barren Measures Formation of the Talchir Gondwana basin has been studied by
statistical techniques. The lithologies have been grouped under five facies states viz coarse-, medium-, and fine-grained
sandstones, shale and coal for statistical analyses. Markov chain analysis indicates the arrangement of Barren Measures lithofacies
in the form of fining upward cycles. A complete cycle consists of conglomerate or coarse-grained sandstone at the base sequentially
succeeded by medium-and fine-grained sandstones, shales and coal at the top. The entropy analysis puts the Barren Measures
cycles into A-4 type cyclicity, which consists of different proportions of lower, upper and side truncated cycles of lithologic
states. Regression analysis indicates a sympathetic relationship between total thickness of strata (net subsidence) and number
of cycles and an antipathic relationship between average thickness and number of sedimentary cycles. The cyclic sedimentation
of the Barren Measures Formation was controlled by autocyclic process which occurred due to the lateral migration of streams
triggered by intrabasinal differential subsidence. In many instances, the clastic sediments from the laterally migrating rivers
interrupted the cyclic sedimentation resulting in thinner cycles in areas where the number of cycles are more. Principal component
and multivariate regression analyses suggest that the net subsidence of the basin is mostly controlled by the thickness of
sandstones, shale beds and coal stringers. 相似文献
14.
A facies classification of sedimentary rocks is presented for the Upper Permian Inta Formation of the southern Pechora Coal
Basin. A correlation has been revealed between clay mineral assemblages and certain facies types of lacustrine sediments. 相似文献
15.
Gondwana basins of Orissa State constitute a major part of the Mahanadi Master Basin. These Gondwana sediments, ranging from Asselian to Albian in age, contain remnants of three basic floral assemblages i.e. Glossopteris Assemblage, Dicroidium Assemblage and Ptilophyllum Assemblage which can be recognized through the Permian, Triassic and Early Cretaceous, respectively. The megafloral assemblages of different basins of this state are discussed briefly. This report mainly deals with the plant species diversification in different lithological formations and the development of flora in the Gondwana basins of Orissa. A number of successive megafloras are recognized. Among those, leaves are the dominant part of the preserved flora, followed by fruits and roots. No wood parts are preserved in the major basins. These pre-angiospermic floras have been systematically analyzed to depict the evolutionary trends, and palaeofloristics of these basins. The distribution of plant fossils in different formations of these basins depicts provincialism in Gondwana flora within the Orissa. 相似文献
16.
Gondwana basins of Orissa State constitute a major part of the Mahanadi Master Basin. These Gondwana sediments, ranging from Asselian to Albian in age, contain remnants of three basic floral assemblages i.e. Glossopteris Assemblage, Dicroidium Assemblage and Ptilophyllum Assemblage which can be recognized through the Permian, Triassic and Early Cretaceous, respectively. The megafloral assemblages of different basins of this state are discussed briefly. This report mainly deals with the plant species diversification in different lithological formations and the development of flora in the Gondwana basins of Orissa. A number of successive megafloras are recognized. Among those, leaves are the dominant part of the preserved flora, followed by fruits and roots. No wood parts are preserved in the major basins. These pre-angiospermic floras have been systematically analyzed to depict the evolutionary trends, and palaeofloristics of these basins. The distribution of plant fossils in different formations of these basins depicts provincialism in Gondwana flora within the Orissa. 相似文献
17.
Four types of soft-sediment folds of distinct geometry can be recognized in the upper part of the Talchir Formation (Lower Permian) of Jharia Basin, India. These folds, on systematic examination, indicate some events of progressive deformation. Experimental study reveals that if a layered stack of clay and overlying sand is allowed to flow slowly down a slope, differential velocity due to viscosity contrast leads to the deformation of the rheologic interface. The sharp planar contact gradually becomes wavy leading to the development of round-hinged folds involving sediments adjacent to it. With the advancement of the flow these folds gradually become overturned with the rotation of the axial plane in the direction of flow. Computer simulation suggests that progressive deformation of these folds by simple shearing may lead to the formation of tight isoclinal folds, which on dislocation along intrastratal normal faults may lead to the development of rootless isoclinal folds. The sheath folds observed in the studied section also indicate accentuation of the curved hinge due to simple shearing. The spatial distribution of these fold types in conjunction with the inferred direction of progressive deformation indicate basinward translation of the slump slice. If the same stack of sediments rapidly flows down the slope, the waveform generated at the interface quickly breaks in the form of roll-up recumbent fold due to Kelvin–Helmholtz instability. 相似文献
18.
The present work provides a detailed lithological map of the western part of the Satpura basin around Sohagpur and reports the presence of new archosauromorph fossil bones from that region. The study area is dominated by the Bagra Formation along with a narrow patch of the underlying upper part of the Denwa Formation. The lower Denwa and the underlying Pachmarhi formations are absent here. The presence of the Pachmarhi Formation, as a tongue shaped area, as mapped by Crookshank (1936) is discarded in this study on the basis of lithology and petrographic analyses, instead the presence of the Bagra Formation is suggested in this area. A comparison of the lithologies and the vertebrate faunas of the upper Gondwana formations between eastern and western part of the basin has been carried out for the first time. The comparison indicates that the Denwa Formation present in the western sector represents only the topmost part of the formation while the complete succession of Denwa is preserved in the eastern sector. The Bagra Formation in the western sector documents the presence of sheet-like sandstone bodies unlike the eastern part. The vertebrate fauna of the eastern part is dominated by temnospondyl amphibians while that of the western part is dominated by archosauromorph. The vertebrate fossils of upper part of Denwa Formation, found from similar lithologies in west and east though, have differences in the amount of transportation before their burial. 相似文献
19.
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. 相似文献
20.
ABSTRACT The Upper Triassic (Carnian?) Molteno Formation in the main Karoo (Gondwana) Basin, South Africa forms a northerly thinning, intracratonic clastic wedge comprising sandstones, shales and coals occurring within thick (up to 140 m) laterally persistent fining-upward sequences. These sequences were deposited by braided streams draining an alluvial plain which may have been built on to the distal slopes of alluvial fan complexes of glacial outwash type. Geometric relations between sequences indicate three phases of tectonic activity. The lowermost fining-upward sequence in the south accumulated against a rising mountain front; cessation of movement and an eastward shift in the main locus of tectonism and sedimentation was followed by renewed uplift and basinwide progradation of the second fining-upward sequence adjacent to a fault-block granite terrain located close to the present south-east coastline of South Africa. This is believed to be the granite at the eastern end of the Falkland Island Plateau, an interpretation consistent with its position on most continental reconstructions and the fracture zone marking its northern scarp face. Faulting is attributed to the first phase of extension prior to continental breakup. The sourceward recession and lack of gross fining-upward trends shown by the uppermost fining-upward sequences is accounted for by limited back-faulting of the still active basin margin. Cessation of activity and further basin margin recession occurred with deposition of the overlying floodplain deposits (Elliot Formation) which were distal equivalents of the braided alluvial plain. 相似文献
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