Indicator Of Deposition Research Articles

Laser 40Ar/39Ar dating of single detrital muscovite grains from early foreland-basin sedimentary deposits in India: Implications for early Himalayan evolution

Research Article| June 01, 1997 Laser 40Ar/39Ar dating of single detrital muscovite grains from early foreland-basin sedimentary deposits in India: Implications for early Himalayan evolution Y. M. R. Najman; Y. M. R. Najman 1Department of Geology and Geophysics, Edinburgh University, West Mains Road, Edinburgh EH9 3JW, United Kingdom2Department of Earth Sciences, Cambridge University, Downing Street, Cambridge CB2 3EQ, United Kingdom Search for other works by this author on: GSW Google Scholar M. S. Pringle; M. S. Pringle 3Scottish Universities Research and Reactor Centre, Scottish Enterprise Technology Park, East Kilbride G75 0QF, United Kingdom Search for other works by this author on: GSW Google Scholar M. R. W. Johnson; M. R. W. Johnson 1Department of Geology and Geophysics, Edinburgh University, West Mains Road, Edinburgh EH9 3JW, United Kingdom Search for other works by this author on: GSW Google Scholar A. H. F. Robertson; A. H. F. Robertson 1Department of Geology and Geophysics, Edinburgh University, West Mains Road, Edinburgh EH9 3JW, United Kingdom Search for other works by this author on: GSW Google Scholar J. R. Wijbrans J. R. Wijbrans 4Faculty of Earth Sciences, Vrije Universiteit, De Boelelaan 1085, 1081HV Amsterdam, The Netherlands Search for other works by this author on: GSW Google Scholar Geology (1997) 25 (6): 535–538. https://doi.org/10.1130/0091-7613(1997)025<0535:LAADOS>2.3.CO;2 Article history first online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Y. M. R. Najman, M. S. Pringle, M. R. W. Johnson, A. H. F. Robertson, J. R. Wijbrans; Laser 40Ar/39Ar dating of single detrital muscovite grains from early foreland-basin sedimentary deposits in India: Implications for early Himalayan evolution. Geology 1997;; 25 (6): 535–538. doi: https://doi.org/10.1130/0091-7613(1997)025<0535:LAADOS>2.3.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract In India, the Dagshai and overlying Kasauli Formations represent the oldest exposed continental foredeep sediments eroded from the Himalayan orogen. 40Ar/39Ar dating of individual detrital white micas from these sedimentary units has provided maximum depositional ages of <28 Ma for the Dagshai Formation at one locality and <25 Ma at a second locality, whereas deposition of the Kasauli Formation occurred after 28 Ma at two localities and after 22 Ma at a third locality. This timing suggests that, in India, the start of substantial exhumation and erosion from the rising Himalayan orogen was delayed until 28 Ma. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Sedimentary indicators of lake-level changes in the humid temperate zone: a critical review

Evidence for lake-level changes derived from stratigraphic sequences in cores from littoral zones is reviewed in the context of lake sedimentation processes. These are illustrated with published case-studies which have used multiple-core data. Possible approaches for choosing optimum sites are examined. Sedimentation controls which may change over time are also considered; these include, wind strength and frequency, wind exposure, water depth and underwater slopes, sediment type and littoral vegetation. A final section discusses how lake-level studies can be optimised so that results can be used with confidence in paleoclimatic and paleohydrological reconstructions. Sedimentary data showing shifts in littoral vegetation along shallow underwater gradients in sheltered margins, and transitions between sediment compositions linked to specific hydrological conditions give the strongest lines of evidence.

Earliest Acheulian Industry from Peninsular India

Decouverte d'un assemblage de 152 objets lithiques a Bori (Maharashtra, Inde) representant le plus ancien materiel connu de l'Acheuleen du subcontinent indien

Rare earth deposits in India - An outline of their types, distribution, mineralogy-geochemistry and genesis

Rare earth deposits in India are divided here into two principal types : endogenic and exogenic. While the former includes some carbonatites, metamorphic-metasomatic veins, the latter comprises coastal or beach placer, inland placer and offshore placer. As of to-day, the endogenic deposits do not appear to be very much attractive from exploitational point of view. Mainly beach placers are mined in India at present. Monazite is the principal ore mineral for REE in India, although xenotime holds out some prospect for the future. Of India's estimated reserve of 5 million tonnes of monazite, 70-75 % occur in beach placer and the rest in the inland and offshore varieties. Monazite-content of beach sands may be upto 11 wt%. ThO 2 ranges between 8-10.5%. Average Σ REO 60%. Inland placers contain either monazite or xenotime as the principal REE-bearing mineral. Of late, work on inland placer has started for xenotime. Factors controlling placer formation are : (1) provenance, (2) physico-chemical properties of the minerals in the placer, (3) physico-chemical ambience, the source rocks/earlier deposits are exposed to, and (4) physical process of concentration. In the development of India's beach placer deposits, granites, granitic pegmatites, migmatites, gneisses, charnockites, leptynites and khondalites provided the necessary source and the tropical climate with heavy rainfall and strong wave action was especially conducive to the concentration of the placer-minerals in suitable locales.

Rank evaluation of the Neyveli lignite deposit on the basis of reflectance parameter : A. Singh & B. D. Singh, Journal — Geological Society of India, 44(4), 1994, pp 391–397

The Neyveli field is well known for Tertiary lignite deposits in India. The reflectance of organic constituents (humioite macerals) has been measured to find out organic maturation level (rank) of the main lignite seam lying either at same time level or at different time levels in space. The deposits are of sub-bituminous C stage (ASTM) with the mean refectance (Ro max. in oil) range from 0.34 to 0.42% (average 0.39%). Evidences from rank study indicate that the quality of lignite deteriorates towards southern part of the field.

Paleolimnological assessment of damage to fish communities in three acidic, Canadian Shield lakes

Long-term fisheries data from small lakes are often sadly lacking. We employ three classes of sedimentary remains (mandibles of larval Chaoborus, diatom valves and chrysophyte scales) to verify that the fish communities of three small, acidic (pH 5.3–5.6) Canadian Shield lakes in south-central Ontario were richer 20–100 years ago at a time when the lakes were almost certainly less acidic. To do this, we first verify that Chaoborus americanus is never abundant in the presence of fish using data from a new survey of 50 lakes that corrects for methodological flaws of the past. We then examine changes with sediment depth in our three classes of indicators in Lakes Drummer, Little Eastern, and Shoelace. In all cases, appearrances of Chaoborus americanus and changes among algl remains in recent sediments suggest that fish were lost at a time when lake waters were acidifying, particulary because of pH depressions during spring melt. These results contribute to a growing body of literature indicating that the use of multiple sedimentary indicators can provide assessments of past limnological conditions that are of interest to both lake managers and aquatic ecologists. They also suggest that the fish communities of some small, currently acidic lakes in south-central Ontario were almost certainly richer in the past.

Geology and geochemistry of the Degana pluton?A proterozoic rapakivi granite in Rajasthan, India

The Degana pluton hosts one of the few known tungsten deposits in India It is an epizonal, moderately high silica pluton emplaced during the Proterozoic in a posttectonic setting. Though homogeneous in composition, it displays textural heterogeneity from coarse-grained hypidiomorphic to fine-grained porphyritic to hypabyssal granite porphyry. Genetically related rhyolites are also present. Coherency of geochemical and mineralogical attributes in the Degana pluton can be explained by fractional crystallisation. Complex variety of hydrothermal and pneumatolytic features is also present. At shallow depths, emanation differentiation has led to progressive enrichment of Li, Rb, and W. Both the plutonic and volcanic phases of the magma show development of rapakivi texture and other diagnostic characteristics of the rapakivi granites.

Sedimentary palaeoclimatic indicators: what they are and what they tell us

The significance of sedim entary indicators of palaeoclimate to future palaeoclimatic research will depend on more rigorous calibration of the climatic controls on the formation of those indicators.

Environmentally Compatible Coal Extraction and Utilisation Indian Scenario

Environmental quality is as much an indicator of the level of development as the generally accepted norm of per capita consumption of energy. Coal, being the mainstay of energy in India, will continue to play a crucial role on both the counts as annual coal utilization is expected to increase by 2.5 times by the year 2005. Indian coal being of poor quality with 35 to 48% ash content has serious adverse implications on air, water and land environment which will be aggravated further by opening up extensive areas for opencast coal mining operations to meet the increased coal demand. Many coal deposits in India are located in areas rich in bio-diversity and, these areas need to be specially protected as they are crucial for our very survival. Mining operations, therefore, need to be harmonised with protection of genetic stock and the forest areas which serve as cheap “Carbon-dioxide Sinks”. A prerequisite in coal extraction and its utilization is the need for making technological conversion processes as efficient as possible to achieve a higher output from the same resource base. This calls for setting up a chain of coal washeries for better plant performance, reduced environmental pollution and overall cost savings. Demonstrated benefits of coal washeries include 5–15% saving in coal consumption with a freight saving alone to the tune of $3 billion in the year 2000; 2% increase in plant availability for every percent drop in ash content and, improved plant load factor netting annual savings of $1.4 million in a single 210 MW thermal power plant. Switching over to cleaner technologies and replacement or retrofitting of vintage boilers can further add to coal savings, and an improved environment. Optimisation of coal utilisation and internalisation of environmental concerns demands adoption of “carrying capacity based” planning process. Adoption of rational pricing at full cost, introduction of fiscal incentives for promoting Clean Coal Technologies and, reorientation of lending policies towards “Greener Credit” can also contribute to improved benefit stream with reduced environmental damage. This paper outlines the strategy for sustainable development while concurrently meeting the obligations for controlling Green House Gases under the International Conventions.

Paleographic Atlas of Northern Eurasia: Aims and Current Progress

A project aimed at paleographic reconstruction of northern Eurasia (the former USSR and adjacent territories) commenced in 1993 in Russia under the auspices of two nongovernmental scientific organizations: Scientific Council on Plate Tectonics and Institute of Tectonics of Lithospheric Plates. The project is sponsored by the State Committee on Geology and Exxon and Shell companies. Twenty-six data-base maps and corresponding paleogeographic maps on a set of new paleotectonic reconstructions are to be compiled within two years, covering a period from Devonian to present. The next two-year phase is expected to follow, with a compilation of similar maps for Early Paleozoic and late Riphean. the best experts on regional geology, paleoenvironment, paleomagnetics, and paleotectonic reconstructions participate in the program. A special group, Geocentre Company, is assigned to the computerization of maps. The 1993 compilation of 15 database maps is to be completed and the first reconstructions produced. The database maps (starting from Tithonian upward) contain information on lithology, facies and thickness of sedimentary formations, and magnetic and structural indicators of plate tectonic data; oil and gas deposits are indicated. Emphasis is placed on the paleogeographic evolution of sedimentary basins, potential reservoirs of hydrocarbons. Narrow time intervals between maps (about 10 m.y.)more » permit detailed reconstructions of the basins' evolution. Examples of database and paleogeographic maps are presented in the poster.« less

Announcing the 1993 SEPM Theme Meeting August 8th–12th, 1993, State College, Pa Stratigraphic Record of Global Change: Climate, Sea Level, and Life

The Society of Sedimentary Geology (SEPM) joins with the Department of Geosciences and Keller Conference Center, Penn State University, in hosting the Society's 1993 Theme Meeting on the biotic, sedimentary, and geochemical indicators of past global change. The goal of this meeting is to bring together researchers studying the stratigraphic record with researchers using physically based models. Tentative Symposia topics include:

Tectonic-climatic supercycle in the billion-year plate-tectonic eon: Permian Pangean icehouse alternates with Cretaceous dispersed-continents greenhouse

The earth alternates in a supercycle 400 m.y. long from a single continent (Pangea) and ocean (Panthalassa) with an icehouse climate to many continents and oceans with a greenhouse climate. The supercycle is driven by the heat that accumulates beneath the insulator of Pangea, and the greenhouse is made by the excess CO 2 vented from the mantle during the faster rate of plate activity. In the current supercycle (A) since the mid-Carboniferous (320 Ma), the growth and decay of Pangean heat is observed in globally synchronous cratonic sedimentary sequences that represent, in ascending order: (1) a stratigraphic gap, (2) sagging, (3) rifting, (4) fast, and (5) slow seafloor spreading. Stages 4 and 5 of the previous supercycle (B) are observed back to the start of the Phanerozoic; in the Proterozoic, earlier stages of B are postulated back to 720 Ma and a third supercycle (C) to 1100 Ma. The big glaciations of the latest Proterozoic (700-600 Ma) and Late Palaeozoic (320-260 Ma) are confined to the icehouse state during stages 1–3; the Sturtian (800 Ma), latest Ordovician (440 Ma), and Quaternary (2-0 Ma) glaciations fall within greenhouse states during stage 5 of slow seafloor spreading. The next icehouse glaciation is expected 80 Ma hence. The problem of long-term past (and future) climate change is soluble by global studies. Urgently needed are (1) global stock-takes of (a) the rate of granite emplacement, which serves as a proxy via plate activity for the mantle source of atmospheric CO 2, and (b) carbonate sinks and other sedimentary indicators of CO 2; and (2) the extension of the sea-level curve back past 570 Ma to the start of the plate-tectonic eon 1100 Ma ago. From such studies, environmental baselines for past climatic states can be drawn for gauging present and future “background” variations.

Alkalinity and pH of three lakes in northern New England, U. S. A., over the past 300 years

Three-hundred-year histories of pH and total alkalinity (alk) have been inferred from diatom and chrysophyte remains in deep-water sediment cores from Mud Pond (pH 4.6, alk — 23 ueq 1_1) and Little Long Pond (pH 5.7, alk 4 ueq1-1), Maine and Haystack Pond (pH 4.8, alk —18 peq 1-1), Vermont. Three replicate cores were studied from each Mud Pond and Haystack Pond; one core from Little Long Pond; pH and alk inferences from diatoms were based on three different calibration equations: cluster, decorana and cca (canoco) (only cca for chrysophytes). Replication of pH and alk inferences between cores was excellent. Different calibration approaches led to the same conclusions with minor exceptions. There were minor differences between chrysophyte- and diatom-based inferences, but both led to similar conclusions regarding acidification. These were: Mud Pond, ca. 1700-1925, pH 5.2-5.3, alk 0 to — 15 ueq1-1; 1925-1970, acidification to pH ~ 4.8 and alk —20 to —30 ueq1-1. Little Long Pond ca. 1700-1950, pH ~ 5.9, alk 20-50 ueq1-1; 1950 ff, possible slight acidification to pH 5.7-5.8. Haystack Pond, ca. 1700-1925, pH 5.2-5.3, alk 0 to -1 0 ueq 1-1; 1925-1970, acidification to pH ~ 4.9 and alk —10 to —30 ueq 1-1. Correlation of lake acidification with great increases in sedimentary indicators of air pollution (carbonaceous particles, Pb, polycyclic aromatic hydrocarbons) and absence of correlated catchment disturbance point to anthropogenic acid deposition as the cause of lake acidification. Extreme acid sensitive lakes like these three are atypical for northern New England.

Herpetofauna of the Ipswichian Interglacial Bed (Late Pleistocene) of the Itteringham Gravel Pit, Norfolk, England

-At least four species of anurans, one tortoise and one snake were identified from the Ipswichian interglacial bed (Late Pleistocene) of the Itteringham Gravel Pit, Norfolk, England. A tree frog (Hyla sp.) is reported for the first time as a British fossil. The herpetofauna indicates that the major habitat was a lentic one. The occurrence of the tree frog (Hyla sp.), continental water frogs (Rana), and the European pond tortoise (Emys orbicularis) indicates a continental climate with warmer summers than occur in England today. The mammalian fauna of the British Pleistocene has been well-studied (Stuart, 1982), but the British Pleistocene herpetofauna has been largely neglected until recently. These recent works include reports of the European pond tortoise from interglacial sites (Stuart, 1979, 1982), and short herpetofaunal papers on Cromerian (Holman, 1987c; Holman et al., 1988), Hoxnian (Holman, 1987a), Ipswichian (Holman, 1987b), Devensian/Flandrian (Holman, 1988) and Flandrian (Holman, 1985, 1987a) localities. Studies of fossil herpetofaunas are important in making paleoecological interpretations, for modern amphibians and reptiles have specific ecological requirements and most Pleistocene species have modern equivalents that have been well-studied in Britain and on the continent. Moreover, certain species may be particularly important in indicating specific environmental conditions because of stringent climatic reproductive constraints (Stuart, 1979). The Ipswichian Interglacial Stage.-Except for the Flandrian, the Ipswichian is the best known of the British interglacials. The Ipswichian (ca. 120,000-110,000 years before present) occurs between the cold glacial times of the older Wolstonian stage and the younger Devensian stage. Stuart (1982) provides a general discussion of the most important Ipswichian sites and their vertebrate fauna. The presence of fossils of the African hippo (Hippopotamus amphibius) is generally accepted as diagnostic of the Ipswichian. Some other mammals which no longer are native to Britain but do appear in the Ipswichian are the horse (Equus ferus), spotted hyena (Crocuta crocuta) and the lion (Panthera leo). The Ipswichian has also yielded the European pond tortoise (Emys orbicularis) from many of its sites. The type site of the Ipswichian is Bobbitshole, Ipswich, England. The Itteringham Deposit.-The Itteringham Gravel Pit (National Grid Reference 139305) is located beside the River Bure in the parish of Oulton, 6 km west of Aylsham, Norfolk, England. Deposits belonging to four distinct climatic stages have been identified. The uppermost valley deposits (mostly peat) belong to the present (Flandrian) interglacial. Beneath these are gravels and clays with fossil and sedimentary indications of intense cold and these are assigned to the last (Devensian) glacial. Stratigraphically lower are detrital muds and organic sands which are fully interglacial in character. 33 This content downloaded from 207.46.13.167 on Thu, 21 Jul 2016 05:09:32 UTC All use subject to http://about.jstor.org/terms L. A. HALLOCK ET AL.

Two decades of phosphorite investigations in India

Abstract Phosphate rock has been known for many years in some of the sedimentary basins of India. Several discoveries in the 1960s and 1970s have proved of economic importance although the country continues to remain dependent upon imports for most of its phosphate requirements. Scope for further finds of phosphate rock have probably not been exhausted and a much more co-ordinated exploration programme is recommended. Proterozoic basins continue to offer the best exploration potential and currently account for the bulk of the known domestic phosphate rock resources. Nevertheless, geologically younger basins should not be discounted in terms of their phosphate potential. Geological ages for the main phosphorite sequences in India are not well established and there is no precise stratigraphic correlation with Proterozoic-Cambrian phosphorite provinces in other parts of the world. Since the discovery of phosphorite beds of Palaeozoic age near Dehra Dun, Uttar Pradesh, and Jaisalmer, in southeastern Rajasthan, considerable progress has been made in both the exploration for and exploitation of phosphate deposits in India. One notable, promising development in recent years has been that associated with research, in India, on the beneficiation of low-grade and highly dolomitic phosphate rock.

Paleogeography of the northern portion of the Mixteca terrain, southern Mexico, during the Middle Jurassic

A preliminary paleogeographic reconstruction of the northern Mixteca terrain in southern Mexico is presented for the Middle Jurassic. The reconstruction is derived from combined analyses of spatial distribution of marine-continental Jurassic sedimentary units, identification of sediment source, and observations based on sedimentary indicators of environment and transport directions, as well as paleomagnetic and anisotropy of magnetic susceptibility (AMS) results. There is an overall agreement between the AMS magnetic fabric results and the sedimentary indicators of current directions and paleogeographic elements. The results suggest a coastline at the south-southwest portion of this terrain, a general transport of fluvial sediments to the south and southwest, and marine influxes from the south. A Pacific margin provenance is supported by the paleomagnetic results for the northern portion of the Mixteca terrain.

Geothermometry based on fractionation of Mn and Cd between coexisting sphalerite and galena from some carbonate-hosted sulfide deposits in India

Geothermometry based on the fractionation of Mn and Cd between coexisting sphalerite and galena from concordantly banded, strata-bound ores and younger vein ores of Rajpura-Dariba, Zawar, and Bandalamottu has been attempted. Different fractionation trends for the banded and vein ores in the same deposit at Rajpura-Dariba indicate different thermal regimes of final equilibration for the two varieties of ores. In contrast, a single trend incorpo- rating both types of ores is suggestive of isothermal condi- tions of final equilibration for the banded and vein ores at Zawar. Unrealistically high temperatures obtained for the vein ores of Bandalamottu suggest equilibrium in the sphalerite-galena aggregates of this deposit was not at- tained. Thermometric data from Mn and Cd fractionation are compared with other independent geothermometric de- terminations obtained from fluid inclusion homogenization studies and based on phase equilibria. It has been found that, in general, the Cd-fractionation temperature (Tcd) is a more reliable geothermometer than the Mn-fractionation temperature (Tun). This presumably may be due to the sus- ceptibility of aqueous Mn species to subtle changes in fo2 in the ore fluid and consequent heterogeneity in Mn concentra- tion in sphalerite, thus affecting the distribution coefficient. The investigation also suggests that Tca becomes increasing- ly more dependable when the ores are metamorphosed and reequilibrated at higher grades of metamorphism.

Determinants of Commercial Bank Deposits in India

Determinants of Commercial Bank Deposits in India

Lead-zinc resource prediction in India: An application of Zipf's law

Resource prediction is necessary for allocation of exploration efforts to keep pace with future demand and the growth pattern of a commodity. Zipf's law, a mathematical relationship between size and rank of discrete phenomena, has been used for resource prediction of oil in Western Canada, uranium, gold, tin, and lead-zinc deposits in Australia, and copper deposits in Zambia. The model, applied to lead-zinc metal accumulation of 24 known “precambrain” deposits in India, indicates that about 75% of the lead-zinc metal is yet to be discovered. The probability of occurrence of 14 deposits of larger dimensions based on the cumulative percentage frequency for different accumulations lies between 5 and 30%. In future exploration, preference should be given to more effort in the Banded Gneissic Complex of Rajasthan in comparison to Aravalilis of Rajasthan, followed by similar environments throughout the country and Palaeozoic strata of the Himalayas.

Paleolimnological reconstruction of the effects of atmospheric deposition of acids and heavy metals on the chemistry and biology of lakes in New England and Norway

Sediment cores from nine lakes in southern Norway (N) and six in northern New England (NE) were dated by 137Cs, 210Pb and in NE also by pollen, and were analyzed geochemically and for diatoms. Cores from two N and three NE lakes were analyzed for cladocerans. 137Cs dating is unreliable in these lakes, probably due to mobility of Cs in the sediment. In Holmvatn sediment, an up-core increase in Fe, starting ca. 1900, correlates with geochemical indications of decreasing mechanical erosion of soils. Diatoms indicate a lake acidification starting in the 1920's. We propose that soil Fe was mobilized and runoff acidified by acidic precipitation and/or by soil acidification resulting from vegetational succession following reduced grazing. Even minor land use changes or disturbances in lake watersheds introduce ambiguity to the sedimentary evidence relating to atmospheric influences. Diatom counts from surface sediments in 36 N and 31 NE lakes were regressed against contemporary water pH to obtain coefficients for computing past pH from subsurface counts. Computed decreases of 0.3–0.8 pH units start between I890 and I930 in N lakes already acidic (pH 5.0–5.5) before the decrease. These and lesser decreases in other lakes start decades to over a century after the first sedimentary indications of atmospheric heavy metal pollution. It is proposed that the acidification of precipitation accompanied the metal pollution. The delays in lake acidification may be due to buffering by the lakes and watersheds. The magnitude of acidification and heavy metal loading of the lakes parallels air pollution gradients. Shift in cladoceran remains are contemporary with acidification, preceding elimination of fishes.