Palaeobotany of Gondwana basins of Orissa State,India: A bird's eye view

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.     

Occurrence of Cordaitales from lower Gondwana sediments of Ib-River Coalfield, Orissa, India: An Indian scenario

The Ib-River Coalfield in Orissa State is a part of Mahanadi Master Basin. Recent extensive investigations were conducted in this Coalfield to locate fossiliferous beds in the Lower Gondwana deposits and as a result a large cache of plant fossils were recovered from Lower Permian sediments (Barakar Formation) exposed in Jurabaga and Lajkura Collieries. The complete flora includes 23 genera representing nine orders viz., Lycopodiales, Equisetales, Sphenophyllales, Filicales, Cordaitales, Coniferales, Ginkgoales, Cycadales and Glossopteridales. Only the Cordaitales, represented by four genera i.e., Noeggerathiopsis, Cordaites, Euryphyllum and Kawizophyllum are discussed in this paper. Cordaitalean leaves are described for the first time from this coalfield; the remaining plant groups will be considered in a subsequent publication. Cordaitalean leaves attributable to Noeggerathiopsis hislopii, Noeggerathiopsis minor, Euryphyllum whittianum, Euryphyllum maithyi, Kawizophyllum dunpathriensis and Cordaites sp. constitute about 13.90% (111 specimens) of the total plant assemblage collected from this Coalfield. Of the cordaitaleans, N. hislopii is most abundant (47.75%; 53 specimens) followed by E. whittianum (40.54%; 45 specimens). A summary of the distribution of Cordaitales throughout the Indian Gondwana is also presented. Floristic composition varies stratigraphically at the two Barakar exposures (Lajkura and Jurabaga Collieries). Cordaitales are preserved only in the lowermost (4th) horizon (lower floral zone). Strata in these collieries have been assigned to the lower and upper Barakar Formation based on floristic content and an Early Permian (Artinskian) age is assigned.     

Similarity of palaeocurrent pattern of Lower Gondwana formations of the Talchir and the Ong-river basins of Orissa, India – An indication of dismemberment of a major Gondwana basin

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.     

Structural architecture of the northern composite terrane, the Eastern Ghats Mobile Belt, India: Implications for Gondwana tectonics

New data from structural mapping and tectonic evaluation in the northern parts of the Eastern Ghats Mobile Belt (EGMB-north) involving the interpretation of satellite images, field traverses, critical outcrop mapping and kinematic studies of macro- as well as microstructures of the shear zone rocks together with the geometry and disposition of Gondwana basins led to, for the first time, the elucidation of post-Grenvillian structural architecture of the terrane. This helps in assessing the sequence of successive tectonothermal events that were responsible for the origin and progressive evolution of the Permo-Carboniferous coal bearing sediments along the Mahanadi rift that forms significant in the reconstruction models of east Gondwana.The composite terrane of high-grade metamorphic rocks (EGMB-north), strikes E–W in contrast to the regional NE–SW trend of the EGMB. The structural architecture obtained from this study is controlled by the boundary shear zones and associated link shear zones. The dextral kinematic displacements along the Northern Boundary Shear Zone (NBSZ) as well as the Mahanadi Shear Zone (MSZ) and Koraput–Sonapur–Rairakhol Shear Zone (KSRSZ) were derived from multi-scale field based structural observations. A N–S structural cross-section presents a crustal-scale ‘flower structure’ across the composite terrane exposing different domains displaying distinctive internal structures with widely varying different geological evolution history and strain partitioning, separated by crustal-scale shear zones. Deep seismic imaging and gravity signatures support ‘flower structure’ model. The pervasive first formed gneissic fabrics were continuously reworked and partitioned into a series of E–W, crustal-scale shear zones.The Neoproterozoic regional dextral transpressional tectonics along the shear zones and their repeated reactivation could be responsible for initiation and successive evolution of Gondwana basins and different episodes of sedimentation. Available geochronological data shows that the structural architecture presented here is post-Grenvillian, which has been repeatedly reactivated through long-lived transpressional tectonics. The composite terrane is characterized by all the typical features of an oblique convergent orogen with transpressional kinematics in the middle to lower crust. The kinematic changes from transpression to transtensional stresses were found to be associated with global geodynamics related to the transformation from Rodinia to Gondwana configuration.     

Pull-apart origin of the Satpura Gondwana basin, central India

The Gondwana basins of peninsular India are traditionally considered as extensional-rift basins due to the overwhelming evidence of fault-controlled synsedimentary subsidence. These basins indeed originated under a bulk extensional tectonic regime, due to failure of the attenuated crust along pre-existing zones of weakness inherited from Precambrian structural fabrics. However, disposition of the basins and their structural architecture indicate that the kinematics of all the basins cannot be extensional. To maintain kinematic compatibility with other basins as well as the bulk lateral extension, some basins ought to be of strike-slip origin. The disposition, shape and structural architecture of the Satpura basin, central India suggest that the basin could be a pull-apart basin that developed above a releasing jog of a left-stepping strike-slip fault system defined by the Son-Narmada south fault and Tapti north fault in consequence to sinistral displacement along WSW-ENE. Development of a sedimentary basin under the above-mentioned kinematic condition was simulated in model experiments with sandpack. The shape, relative size, stratigraphic and structural architecture of the experimental basin tally with that of the Satpura basin. The experimental results also provide insights into the tectono-sedimentary evolution of the Satpura basin in particular and pull-apart basins in general.     

Trace element chemistry of major rivers in Orissa State, India

 Geochemical analyses of surface waters from rivers flowing through Orissa State, India, indicated that trace element concentrations were extremely variable and consistently higher than world river average. The Brahmani River was the most solute-rich river studied, followed by the Baitarani and Mahanadi Rivers. Although all three rivers drain similar geology, the Brahmani River catchment is heavily industrialized, and water samples collected upstream and downstream from industries indicated that anthropogenic activity directly influenced its chemical composition. Samples collected from several towns, in all three river systems, did not invariably show similar patterns, with various elements having higher dissolved concentrations upstream. Because the concentration of total solids increased downstream, this implied that some components of the sewage had effectively sequestered available elements from solution and converted them to particulate material. Although the impact of pollution is clearly recognizable in water samples collected in proximity to the anthropogenic source, there are only slight elemental accumulations in the lower reaches of the Mahanadi River, with no accumulation in the Brahmani River. Apparently for these large rivers, discharged effluent becomes rapidly diluted, while complexation and sedimentation further removes trace elements from the water column. However, in the less voluminous Baitarani River, elementar enrichment near the river's mouth suggests that in this secondary river, where dilution effects are less, the concerns over regional water quality may be more prevalent. Received: 1 April 1995 · Accepted: 30 August 1995     

Cyclic sedimentation of the Karharbari Formation (Damuda Group), Talchir Gondwana basin, Orissa

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.     

Comparative Study of Cyclicity of Lithofacies in Lower Gondwana Formations of Talchir Basin, Orissa, India: A Statistical Analysis of Subsurface Logs

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.     

Taxonomy and affinity of Early Mesoproterozoic megascopic helically coiled and related fossils from the Rohtas Formation, the Vindhyan Supergroup, India

A well preserved assemblage of compressed, straight, circular to sinuously coiled megascopic and helical carbonaceous fossils and other varied megascopic morphoforms are known from the Early Mesoproterozoic Rohtas Formation, Semri Group within Vindhyan Supergroup exposed in Katni district of central India. These megascopic remains are preserved as impressions, compressions, partially mineralized remains, and/or epi-relief. Some of the forms are typical filamentous empty sheaths and others are trichomes, with cell like entities under various stages of degradation. This study, based on fresh collections and also of the topotype material of the helically coiled megascopic fossils, straight forms and related fossilized remains occurring as epi-relief from Katni indicate that the two morphotaxa are distinct entities and possibly appear to be prokaryotes. Grypania spiralis and Katnia singhii are most likely of cyanobacterial origin. Spirally coiled and circular fossils, with epi-relief, and which probably represents a tissue grade organism, are considered as Spiroichnus beerii Mathur, 1983. Linear sheet-like carbonaceous solitary form has been placed in the morphotaxon Proterotainia and described as P. katniensis n. sp. Certain rare circular, carbonaceous forms are considered as Chuaria sp. A few circular disc-like forms found in the assemblage are treated as dubiofossils.     

Deglacial Control on Sedimentation and Basin Evolution of Permo-Carboniferous Talchir Formation, Talchir Gondwana Basin, Orissa, India

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.     

滇中川街盆地中侏罗世弓鲛(软骨鱼类)化石新材料

云南禄丰县川街盆地中侏罗统产出弓鲛鱼类化石后甸弓鲛(Hybodus houtienensis Young)、新庄弓鲛(新种)(Hybodus xinzhuangensis Sun)、川街弓鲛(新种)(Hybodus chuanjieensis Sun)。后甸弓鲛(Hybodus houtienensis Young)是中国发现最早的弓鲛鱼类之一,正型标本为破碎的鳍棘,副型标本为一枚牙齿齿冠。依据在川街盆地相同层位发现的新化石材料,对后甸弓鲛副型标本进行了增补,补充了描述,建立了2个弓鲛新种:新庄弓鲛与川街弓鲛,丰富了"后甸弓鲛带"弓鲛类群,并讨论了弓鲛属的生物地层、生活的古环境和地理分布特征。     

Dimorphism in Placenticeras mintoi from the Upper Cretaceous Bagh Beds, central India

The Upper Cretaceous Bagh Beds yield many biota of which ammonoids are particularly well known. Previously Bagh ammonoids were grouped into many genera and species within several families. The present study, however, shows that failure to recognize dimorphism and a wide range of interspecific variation within the single genus Placenticeras perhaps results in taxonomic oversplitting. Specific dimorphism in P. mintoi has been established.     

A history of the ‘Zambian copper flower', Becium centraliafricanum (B. homblei)

This contribution is a short history of the Zambian copper flower, Becium homblei (recently renamed B. centraliafricanum that has attracted attention as a plant associated with Cu-rich soils. It has a peculiar discontinuous distribution in Central Africa which has been explained in terms of biotype depletion. A field investigation into the ecology of the species shows that it is able to tolerate soil Cu concentrations of up to 15,000 μg/g (ppm), and soil nickel concentrations of nearly 5000 μg/g. B. homblei is also found on areas where soil metals are in trace quantities, and where soil bases, particularly Ca, are low. In spite of its tolerance to a wide range of edaphic conditions, the distribution of the species is very restricted in Zimbabwe, and this is almost certainly due to severe interspecific competition with a closely related species, B. obovatum, which is common on soils not unusually enriched in heavy metals. Pioneering work on geobotanical prospecting by use of Becium homblei was carried out by the late G. Woodward and others in the 1950s and 1960s. This species was used successfully for geobotanical prospecting for Cu. This present report is a brief history of these pioneering studies     

The age of the Cuddapah and Kurnool systems,southern India

In southern India the older Precambrian is overlain unconformably in the Cuddapah Basin by the Cuddapah and Kurnool Systems. The former is tilted and unmetamorphosed in the west but eastwards becomes strongly folded and metamorphosed. It contains lavas and sills, particularly in the lower two groups, is intruded by dolerites and at Chelima by diatremes of kimberlitic affinities related to those intruding the older gneisses west of the Cuddapah Basin in the Wajrakarur area. The Kurnool System lacks any igneous rocks; its basal conglomerate is diamondi‐ferous.

Rb‐Sr dating of lava samples from the lowest group of the Cuddapah System shows that the age of the base of the system may be as great as 1,700 m.y. Together with data for a granite which intrudes probable Cuddapah rocks near the disturbed eastern margin of the basin the data imply that the base is unlikely to be younger than 1,555 m.y. Metamorphism affected some lavas at about 1,360 m.y. The diatremes have two ages of intrusion, about 1,225 m.y. and 1,140 m.y., the latter being the age of the Majhgawan pipe near Panna in northern India. Pre‐Kurnool dolerites have an age of 980 ±110 m.y.

The lavas and dolerites show a range of initial ⁸⁷Sr/⁸⁶Rb ratios from about 0.704 to 0.708 and possibly 0.712.

The age data suggest that no simple correlation can be made with other Precambrian sequences in northern peninsular India. Deposition of the Cuddapah System appears to have started well before the start of the deposition of the Vindhyan System, while the Kurnool System is coeval with only part of the Upper Vindhyan. The data also suggest that present interpretations of the structural development of the Cuddapah Basin may need some revision.     

Reconstructing the migration patterns of late Pleistocene mammals from northern Florida, USA

We used analyses of the strontium isotope (⁸⁷Sr/⁸⁶Sr) ratios of tooth enamel to reconstruct the migration patterns of fossil mammals collected along the Aucilla River in northern Florida. Specimens date to the late-glacial period and before the last glacial maximum (pre-LGM). Deer and tapir displayed low ⁸⁷Sr/⁸⁶Sr ratios that were similar to the ratios of Florida environments, which suggest that these taxa did not migrate long distance outside of the Florida region. Mastodons, mammoths, and equids all displayed a wide range of ⁸⁷Sr/⁸⁶Sr ratios. Some individuals in each taxon displayed low ⁸⁷Sr/⁸⁶Sr ratios that suggest they ranged locally, while other animals had high ⁸⁷Sr/⁸⁶Sr ratios that suggest they migrated long distances (> 150 km) outside of the Florida region. Mastodons were the only taxa from this region that provided enough well-dated specimens to compare changes in migration patterns over time. Pre-LGM mastodons displayed significantly lower ⁸⁷Sr/⁸⁶Sr ratios than late-glacial mastodons, which suggests that late-glacial mastodons from Florida migrated longer distances than their earlier counterparts. This change in movement patterns reflects temporal changes in regional vegetation patterns.     

A record of late-Holocene environmental change from southern New England, USA

Analyses of a sediment core from Little Pond, located in the town of Bolton, Massachusetts, provide new insights into the history of environmental and ecological changes in southern New England during the late Holocene. Declines in organic content and peaks in the abundance of Isoetes spores indicate reduced water depth at 2900–2600, 2200–1800, and 1200–800 calibrated years before present (cal yr BP), generally consistent with the timing of dry conditions in records from elsewhere in the northeastern United States. The Little Pond pollen record features little change over the last 3000 yr, indicating that the surrounding vegetation was relatively insensitive to these periods of drought. The 1200–800 cal yr BP dry interval, however, coincides with increased abundance of Castanea pollen, suggesting that the expansion of Castanea in southern New England may have been influenced by late-Holocene climatic variability.     

A biogeochemical orientation survey in the Moisan gold-mineralized area, Haenam district in Korea

A biogeochemical orientation survey was carried out in the vicinity of an epithermal Au deposit in the Moisan Au–Ag mineralized area, Haenam district in Korea. The Au–Ag bearing quartz veins of the mine occur as narrow open-space fillings within Cretaceous silicic pyroclastics. The vein minerals consist mainly of quartz, sericite, pyrite, chalcopyrite, and galena, with some electrum and argentite. The main objectives of this study were to study the geochemical characteristics of rocks, soils and plants in this area, to investigate the spatial relationship between Au and associated elements in rock–soil–plant system, and to evaluate the applicability of biogeochemical prospecting for Au vein occurrences in Korea. Samples of rocks and soils, and leaves of three plant species (Japanese red pine — P. densiflora, oriental white oak — Q. aliena, Japanese mallotus — M. japonicus) were collected from the target mineralized area and control barren locations, and analyzed for trace elements by instrumental neutron activation analysis. Sampling lines were composed of one slope line which is almost parallel to the mineralized quartz-veins, and four transect lines spaced 100 m apart across the veins at 20 m sampling intervals. From the multi-element data of rock samples (n = 9), high values of Au (maximum 2030 ppb) are spatially related to Au–quartz veins. Soil samples (n = 61) collected from five sampling lines show higher values of Au (24–825 ppb) whereas soil samples from the control locations have lower values of Au (below 25 ppb). Many plant species collected from the vicinity of the veins have high Au contents compared with those at the control locations, but the ranges of Au values are variable among plant species. In a total of 128 samples of plant leaves, Q. aliena yielded Au values of 0.4 to 6.9 ppb, and M. japonicus 0.9 to 4.1 ppb. Gold contents in P. densiflora ranged from 0.1 to 5.6 ppb. Plant leaves from control areas show less than 1.6 ppb Au. The biological absorption coefficient (BAC) of Au in plants decreases in the order of Q. aliena > M. japonicus > P. densiflora. Based on the results of the study, Q. aliena appeared to be the best sampling media for biogeochemical prospecting of Au in the study area.     

First recorded evidence in the fossil record of snipe flies (Diptera: Rhagionidae) in Cretaceous amber, France

Novelaria, a new genus of rhagionid of late Albian age with three new species, is the first record of this family from Charentes amber (southwestern France). The new genus is probably closely related to the recent genus Chrysopilus. However its relationship with the other fossils in amber is discussed. A key for separation of the new species is provided and the diversity of the family during the Cretaceous is also briefly discussed.     

Ptychodus decurrens Agassiz (Elasmobranchii: Ptychodontidae) from the Upper Cretaceous of India

Although a very high invertebrate faunal diversity is known from the outcrops of the Ariyalur group in the Cauvery Basin, southern India, little is known about its vertebrate fauna. Recent fieldwork in the badland exposures of the Karai Formation (Upper Cenomanian-Lower Turonian) near Garudamangalam in the basin has yielded two teeth belonging to the Late Cretaceous shark Ptychodus decurrens (Ptychodontidae). The fossil record of Ptychodus decurrens from the southern continents is very poor, being known from a single Late/Middle Albian occurrence in Australia. This finding documents the first record of fossil P. decurrens in India and second from a Gondwanan landmass, and provides the first evidence of a cosmopolitan, Pangaean, distribution of the species during the Albian-Turonian and additional insights into the palaeoecology of the Cauvery Basin during the deposition of the Karai Formation.