Provenance of the late Paleocene sandstones of the Jaisalmer Basin,Western India

Provenance of the late Paleocene sandstone of the Jaisalmer basin has been determined by petrographic and heavy minerals analysis supported by paleocurrent study. Petrography of the quartzose-arenite sandstone reveals an abundance of sub-angular to sub-rounded monocrystalline non-undulatory quartz and some amount of feldspar and rock fragments. The rock fragments are dominated by argillites (slate, phyllite) and limestone. The heavy minerals suite of these sandstones comprises of angular to sub-angular grains of magnetite, zircon, tourmaline, kyanite and staurolite. The paleocurrent analysis indicates bipolar paleocurrent pattern with the dominance of NW flow suggesting that the provenance was in the SE direction of the depositional basin. Q-F-L and Qm-F-Lt diagrams suggest for a provenance at the margin of the craton interior and transitional continental. It is envisaged that the basic igneous rocks of the Deccan basalt, low- to medium-grade metamorphic rocks of the Aravalli belt and Jurassic limestones present in the vicinity are the source rocks for the late Paleocene sandstones of the Jaisalmer basin.     

dC Variations in Late Jurassic Carbonates, Jaisalmer Formation, Western India

The carbon isotope measurements, carried out on subsurface carbonate samples from Oxfordian Jaisalmer Formation, western India, yield positive d¹³C values up to +3.17%. The most positive Oxfordian C-isotope value corresponds to the carbon isotope excursion measured in samples from from other late Jurassic basins of world. The latest Oxfordian C-isotope values of Jaisalmer Basin fluctuate around 2% while the C-isotope values of 1.50% mark the base of Kimmeridgian. The Oxfordian C-isotope excursion appears to correspond to a time of overall increased organic carbon burial triggered by increased nutrient transfer from continents to oceans during a time of rising global sea level.     

河南西峡盆地上白垩统河流及湖泊沉积中的遗迹组构

河南西峡盆地上白垩统马家村组沉积厚度巨大,达1 960 m,由辫状河沉积、曲流河沉积和湖泊沉积组成。在河流与湖泊沉积中,发育丰富的遗迹化石,共6种类型,分别为Skolithos linearis、Cylindricumichnosp、Palaeophycus tubularis“J”形潜穴、垂直分枝潜穴和垂直螺旋潜穴。从形态分析,大多数为居住迹,按照遗迹化石产出岩层的岩性、扰动特征和残留遗迹等总体特征,将所发现的遗迹化石层划分为两类遗迹组构,即软底组构和僵底组构。前者主要发育在纹层状极细砂岩和粉砂岩中,潜穴密度大,属种单一,包括Skolithos组构和Palaeophycus组构;后者主要发育在厚层泥岩中,潜穴密度较大,类型稍多,包括由Cylindricum ichnosp、垂直分枝潜穴J形潜穴和垂直螺旋潜穴所组成的遗迹组构。与报道过的其他地区陆相遗迹化石的对比表明,随着时间的推移,河流沉积中的组构特征在白垩纪有明显变化,而浅湖沉积中的遗迹组构表明造迹生物的扰动能力显著加强。     

Permian komatiites and associated basalts from the marine sediments of Chhongtash Formation, southeast Karakoram, Ladakh, India

Summary The Karakoram micro-plate is the southern most sector of the Central Asian micro-plate mosaic which was separated by a narrow rift basin. A major rifting phase started during Permian time, which lead to drift of not only Karakoram but of the entire Eurasian (Asian) Plate from Gondwana land. This was at a time when a prominent sequence of black argillites occupied most part of the Karakoram Tethys basin. The geodynamic setting for this sequence may be interpreted as the evolution of a passive margin affected by extensional tectonics. The extensional activity is evident from the extrusion of basalts and komatiitic rocks in the region. In this paper the geochemical relations between komatiites and basalts of the Chhongtash, southeast Karakoram are investigated. The basaltic and komatiitic (ultrabasic) flows are petrologically and geochemically distinct, yet they display a close spatial and temporal association, and they are related to each other through olivine and clinopyroxene fractionation. The chemical characteristics of the ultrabasic to basic magmatism in the region is consistent with formation above a mantle plume that impinged on the continental lithosphere. Hence, a model of partial melting in a mantle plume and fractional crystallization in a deep-seated magma chamber is envisaged to explain the evolution of these volcanic rocks. The komatiite melts are interpreted to have been derived by high degree partial melting of mantle plumes in the tail region, while the basalts were interpreted to be the result of interaction of source plume with cool mantle through which the plume head passed. This study is the first of its kind, to suggest a rift related nature in the Chhongtash, southeast Karakoram, that represent the initial stage of Mesozoic rifting along the southern margin of Eurasia when Gondwana started to drift away from Eurasia.     

Late Pleistocene sea-level oscillations (MIS 10–2) recorded in shallow marine and coastal plain sediments of the southern Wanganui Basin, New Zealand

The northern Wanganui Basin, New Zealand, is one of the key global sites for understanding marine cyclic sedimentation during the Quaternary. This paper presents the first evidence of marine cyclic sedimentation from its central-southern parts. Sedimentological, micropalaeontological and palynological analyses on a 280-m-deep borehole encountered units dating back to MIS 10. The sequence includes four marine cycles spanning MIS 9–5, which are overlain by terrestrial fluvial aggradation surfaces dating from MIS 4–2. Each marine unit represents a progressively shallowing depositional environment from the mid-shelf to coastal plain. This is overlain by a terrestrial sequence of lowstand fluvial terraces. Localized fault movements appear to have influenced the sedimentary character of the sequence during MIS 7a and 5e producing basement highs which provided protection to the shoreline. The cyclothems described in this paper now extend the already extensive, previously described record from MIS 17–10 to produce a combined eustatic record of Quaternary sea level change within the basin to MIS 5. They also provide an excellent example of the sedimentary response of a coastal basin to a progressive loss of sedimentation accommodation space.     

Facies analysis and high-resolution sequence stratigraphy of the Lower Eocene shallow marine Ametlla Formation, Spanish Pyrenees

The Lower Eocene Ametlla Formation of the Ager Basin, Spanish Pyrenees, is a rapidly deposited shallow marine unit formed in a setting characterized by syn-sedimentary tectonic activity. Mapping of the formation over a distance of 25 km was conducted according to sequence stratigraphical principles with emphasis on facies analysis. Twelve facies, grouped in five facies associations, have been recognized in the Ametlla Formation. The studied succession records a vertical transition from deltaic systems prograding onto a sediment-starved shelf, via estuarine deposits associated with incised valleys, to sandbar complexes in a tidal seaway. In terms of sequence stratigraphy, three scales of genetic sedimentary units were recognized. (1) At the regional scale, elements of two 3rd-order composite sequences (sensu Exxon) have been recognized. These include a 3rd-order highstand sequence set encompassing the lowermost part of the Ametlla Formation and the underlying Passarella Formation, and a 3rd-order transgressive sequence set that constitutes the middle parts of the Ametlla Formation. The sequence sets are separated by an unconformity with up to 35 m of incision that is interpreted as a major sequence boundary. It is argued that the incised valleys associated with this unconformity were infilled during landward-stepping of the shelfal depositional system. Basinwards, the unconformable surface becomes subhorizontal and is overlain by a 2 m thick oyster bed formed in a sediment-starved setting subsequent to flooding of the incised valleys (which still acted as sediment conduits). Sandstones dominate the transgressive sequence set, whereas the highstand sequence set is dominated by siltstones, particularly in the lower part. In the transgressive sequence set, an upward increase in sand content and calibre is observed, relatable to punctuations of the transgressive trend by high-frequency sea-level fluctuations, and to downslope redistribution of sand. (2) At the subregional scale, detailed mapping indicates the presence of five 4th-order sequences. The 4th-order sequence boundaries are associated with sediment bypassing and minimal erosional relief, and were created by forced regressions during periods of relative sea-level fall. Sharp-based sandstones overlying these unconformities are believed to have accumulated during subsequent rise of relative sea-level. Where 4th-order maximum flooding surfaces can be recognized, the sequences may be subdivided into a sandstone-dominated transgressive systems tract and a siltstone-dominated highstand systems tract. (3) At the local scale, 2–9 5th-order parasequences are present within the 4th-order sequences. Superimposed parasequences are separated by flooding surfaces characterized by bioclastic accumulations, pervasive burrowing and extensive calcite cementation. The parasequences are commonly stacked in a landward-stepping manner.     

Geotechnical characterization of marine sediments in the Ulleung Basin,East Sea

The geotechnical characteristics of Ulleung Basin sediments are explored using depressurized samples obtained at 2100 m water depth and 110 m below the sea floor. Geotechnical index tests, X-ray diffraction, and SEM images were obtained to identify the governing sediment parameters, chemical composition and mineralogy. We use an instrumented multi-sensor oedometer cell to determine the small-strain stiffness, zero-lateral strain compressibility and electromagnetic properties, and a triaxial device to measure shear strength. SEM images show a sediment structure dominated by microfossils, with some clay minerals that include kaolinite, illite, and chlorite. The preponderant presence of microfossils determines the high porosity of these sediments, defines their microstructure, and governs all macroscale properties. The shear wave velocity increases as the vertical effective stress increases; on the other hand, porosity, permittivity, electrical conductivity, and hydraulic conductivity decrease with increasing confinement. All these parameters exhibit a bi-linear response with effective vertical stress due to the crushable nature of microfossils. Well-established empirical correlations used to evaluate engineering parameters do not apply for these diatomaceous sediments which exhibit higher compressibility than anticipated based on correlations with index properties. Settlements will be particularly important if gas production is attempted using depressurization because this approach will cause both hydrate dissociation and increase in effective stress.     

Fusain in Carboniferous shallow marine sediments, Donegal, Ireland: the sedimentological effects of wildfire

Evidence from fusain deposits in Lower Carboniferous rocks of western Ireland indicates that a catastrophic wildfire destroyed thousands of square kilometres of Carboniferous ‘forest’. In addition to yielding large quantities of charcoal, this wildfire event resulted in increased surface water runoff which affected sedimentation in an adjacent estuarine environment where the fusain is now preserved. This is the oldest documented evidence for a catastrophic palaeowildfire and a clear example of the sedimentological effects of large-scale fires. The Lower Carboniferous (Visean) rocks in the Largymore Syncline of western Donegal, Ireland, are shallow marine sandstones, mudstones and limestones. The Upper Shalwy Beds are mudstones and cross-bedded sandstones which show bi-polar cross-stratification and mud drapes on cross-bed foresets indicating deposition in a tidal environment, probably a large estuary. In three coastal exposures a bed containing up to 20% fusain is found at the same stratigraphic horizon. The fusain is interpreted as fossil charcoal produced by palaeowildfire in a land area to the north-west. The volume of fusain present in the unit can be estimated and by comparison with charcoal production in modern wildfires it has been calculated that around 95 000 km² (more than the present land area of Ireland) was burnt. Along with the fusain, other effects of the wildfire can be seen in the deposits, which are poorly sorted compared to the rest of the Upper Shalwy Beds and are characterized by inclined heterolithic stratification produced by the draping of underlying bedforms. These features are considered to be due to a considerably increased sediment load in the estuary, resulting from enhanced surface runoff and soil erosion due to the wildfire.     

Depositional systems and sequence stratigraphy analysis of the Upper Callovian to Tithonian sediments in the Central and Western Kopet‐Dagh Basin,Northeast Iran

Upper Callovian to Tithonian (late Jurassic) sediments represent an important hydrocarbon reservoir in the Kopet‐Dagh Basin, NE Iran. These deposits consist mainly of limestone, dolostone, and calcareous mudstone with subordinate siliciclastic interbeds. Detailed field surveys, lithofacies and facies analyses at three outcrop sections were used to investigate the depositional environments and sequence stratigraphy of the Middle to Upper Jurassic interval in the central and western areas of the basin. Vertical and lateral facies changes, sedimentary fabrics and structures, and geometry of carbonate bodies resulted in recognition of various carbonate facies related to tidal flats, back‐barrier lagoon, shelf‐margin/shelf‐margin reef, slope and deep‐marine facies belts. These facies were accompanied by interbedded beach and deep marine siliciclastic petrofacies. Field surveys, facies analysis, parasequences stacking patterns, discontinuity surfaces, and geometries coupled with relative depth variation, led to the recognition of six third‐order depositional sequences. The depositional history of the study areas can be divided into two main phases. These indicate platform evolution from a rimmed‐shelf to a carbonate ramp during the late Callovian–Oxfordian and Kimmeridgian–Tithonian intervals, respectively. Significant lateral and vertical facies and thickness changes, and results obtained from regional correlation of the depositional sequences, can be attributed to the combined effect of antecedent topography and differential subsidence related to local tectonics. Moreover, sea‐level changes must be regarded as a major factor during the late Callovian–Tithonian interval. Copyright © 2015 John Wiley & Sons, Ltd.     

Lepidorbitoides (Foraminifera) from the lower Maastrichtian Kallankuruchchi Formation,Cauvery Basin,India: Morphometry and paleobiogeography

The southernmost occurrence of the early Maastrichtian larger benthic foraminifera (LBF) in Tethys is known from the Kallankuruchchi Formation in the Cauvery Basin, SE India, represented by Lepidorbitoides-Siderolites assemblages. The systematics, age and paleobiogeography of Lepidorbitoides here have as yet remained unresolved due to lack of information particularly on the nepionic arrangement, whereas their links with the Western Tethyan and Caribbean biogeographic domains were speculated. Lepidorbitoides, studied from the same level in seven samples in two separate areas, invariably possess quadriserial nepionts and adauxiliary chamberlets, whose mean number ranges from 3.79 to 4.67. The ratio between the sample means of the internal diameter of deuteroconch and protoconch varies between 1.72 and 1.86. The equatorial layer in the early stage consists of arcuate chambers with basal stolons, and ogival-to spatulate chamberlets with annular and oblique stolons in the later stages. These features are consistent with the phylogenetically advanced members of the Western Tethyan Lepidorbitoides lineage, such as L. minor (Schlumberger) and L. socialis (Leymerie), and all samples were assigned to the transitional development stages of these species based on the morphometry. The taxonomic status of some Lepidorbitoides species, originally described from the Kallankuruchchi Formation and widely adopted in previous works, such as L. blanfordi (Rao) and L. inornata (Rao), are not justified. We extend the geographic range of Western Tethyan Lepidorbitoides to southern India.     

The evolution of a thick shallow marine succession, the South Munster Basin, Ireland

The relatively fine-grained Late Devonian to Early Carboniferous 'Cork Beds' succession of the South Munster Basin includes continuous sections of paralic facies that are over 1000 m thick and individual sandstone units over 300 m thick. However, the succession does not reflect prolonged phases when facies belts were stationary, but rather multiple stacking of small-scale, high-frequency sequences, each associated with pronounced migration of shorelines. What seems to have been unusual about the South Munster Basin succession was that the geographical positioning of these high-frequency sequences was fixed. This resulted from an unusual combination of tectonics, shelf hydrodynamics, sedimentation rates and the textural maturity of the sediment within the basin. Of these, tectonics was probably most critical, particularly the juxtaposition of rapid subsidence in basinal areas and a basin margin zone (to the north) that was sufficiently up-standing to pin the maximum extent of transgression during repeated highstands of sea-level, yet not so upstanding as to have diverted the major regional drainage system. The embayed palaeogeography of the area may also have been influential.     

Radioactive occurrence in sediments of Cenozoic age near Bandha village,Jaisalmer district,Rajasthan

The radioactivity is dependent on the isotope and their concentration in the mineral such as potassium (K), uranium (U) and thorium (Th). In this paper the presence of a 3 to 5 m thick uranium and thorium bearing sediment of Cenozoic age is reported above Goru Formation of Jaisalmer basin. Gamma ray log response of Well-1 which falls under the study area has marked with very high GR (gamma ray) readings ranging from 350-1488 API coupled with high uranium and thorium content from spectral gamma ray log ranging from 92-178 ppm and 60-80 ppm respectively at the depth of 50 m from ground surface (-110m above MSL). Further studies are required to delineate the lateral thickness variation for mining purpose which may be a radioactive source.     

Palaeoecology, facies and stratigraphy of shallow marine macrofauna from the Upper Oligocene (Palaeogene) of the southern Pre-North Sea Basin of Astrup (NW Germany)

The 22 meter thick marine carbonate Upper Oligocene series of Astrup (NW Germany) is correlated with the Chattian type section of Doberg. It indicates a more constrained palaeogeographical and biostratigraphical position ranging from the biozones of Chlamys (C.) decussata (upper Chattian A) to Chlamys (C.) semistriatus (lower Chattian C). The macrofauna can be subdivided into three main benthic communities: A. the ?coarse gravel spondylid beach fauna?? of the shore zone with ?pebble beach facies?? dominated by sessile brachiopods, large balanids, spondylids, oysters or small regular echinoids. Borings are common in pebbles; B. the ?glauconite fine gravel brachiopod-bryozoan littoral fauna?? of the shallow subtidal zone where a terebratulid/lithothamnid dominated fauna/flora is present. The rhodophyceans were most possibly anker stones and substrates for cirripeds and serpulids; C. the ?glauconite carbonate sand phytal fauna?? of the shallow subtidal zone with a rich benthic mollusc dominated fauna. Indirect evidence for seagrass and macroalgae occurs on the attachment negatives of balanids and oysters, and also on Cibicides foraminifera or bryozoans like Cellepora. The facies types along the Wiehengebirge Island and Teutoburger Wald Peninsula coasts of the southern Pre-North Sea Basin differ with respect to their benthic communities to that of the siliciclastic Leipziger and the Rhenish Bay facies.     

An Early or Middle Weichselian sequence of proglacial, shallow marine sediments on western Svalbard

A 20 m thick shallow marine sequence, capped by a Late Weichselian lodgement till, is exposed for 200111 along the river in Linnedalen on the west coast of Svalbard. Five formations are recognized: Formation A, the oldest, consists of a shallow marine, proglacial fan, of channelized sandy turbidites, possibly fed from an ice-contact deposit. Formation B, a sequence of proglacial channels and ice-rafted debris, was formed during a small oscillation of the glacier. Formation C, a prograding, storm-dominated shoreline sequence, was formed during a sea level fall, assumed to be a result of glacio-isostatic uplift.
Formation D, a lodgement till formed during the last glacier advance in Linnedalen and formation E, a coarsening upwards sequence, were formed during the post-glacial sea level fall. The subtill sequence (fm. A, B and C) is dated to between 40,000BP (radiocarbon dates) and 120,000BP (thermoluminescence and amino acid D/L ratios). The glacier front was 10 km downvalley during deposition of formations A and B, relative to the present glacier terminus, and more than 12km during the late Weichselian maximum.     

The age of the Nodular Limestone Formation (Late Cretaceous), Narmada Basin,central India

The age of the marine Nodular Limestone Formation of the Bagh Group is refined at Substage level through ammonoid and inoceramid index taxa. The study is based on the fresh collections from three well-defined successive intervals (Lower Karondia, Upper Karondia and Chirakhan members) of this formation having excellent exposures in different localities of the Narmada Basin, central India. The first record of the widely distributed Turonian ammonoid genera Spathites Kummel and Decker and Collignoniceras Breistroffer from the Nodular Limestone Formation constrained its age exclusively to Turonian. The Early Turonian species Spathites (Jeanrogericeras) aff. revelieranus (Courtiller) and Mytiloides labiatus (Sclotheim) occur in the lower part, while the Middle Turonian marker Collignoniceras cf. carolinum (d’Obrbigny) and Inoceramus hobetsensis (Nagao and Matsumoto) occurs in the upper part of the Karondia Member. The record of the index species Inoceramus teshioensis (Nagao and Matsumoto) in association with Placenticeras mintoi Vredenburg from Chirakhan Member allows a definite Late Turonian age. The present contribution is an attempt to resolve the controversies in the age of the Nodular Limestone Formation and also demarcation of the three divisions (Early, Middle and Late) of the Turonian Stage in the Narmada Basin, central India.     

Arsenic associations in sediments from shallow aquifers of northwestern Hetao Basin,Inner Mongolia

Understanding the mechanism of arsenic mobilization from sediments to groundwater is important for water quality management in areas of endemic arsenic poisoning, such as the Hetao Basin in Inner Mongolia, northern China. Aquifer geochemistry was characterized at three field sites (SH, HF, TYS) in Hangjinhouqi County of northwestern Hetao Basin. The results of bulk geochemistry analysis of sediment samples indicated that total As concentrations have a range of 6.8–58.5 mg/kg, with a median of 14.4 mg/kg. The highest As concentrations were found at 15–25 m depth. In the meanwhile, the range of As concentration in the sediments from background borehole is 3–21.8 mg/kg, with a median value of 9 mg/kg. The As sediments concentrations with depth from the SH borehole were correlated with the contents of Fe, Sb, B, V, total C and total S. Generally, the abundance of elements varied with grain size, with higher concentrations in finer fractions of the sediments. Distinct lithology profile and different geochemical characteristics of aquifer sediments indicate the sediments are associated with different sources and diverse sedimentary environments. Up to one third of arsenic in the sediments could be extracted by ammonium oxalate, suggesting that Fe oxyhydroxides may be the major sink of As in the aquifer. Sequential extraction results indicate that arsenic occurs as strongly adsorbed on and/or co-precipitated with amorphous Fe oxyhydroxides in sediments accounting for 35 and 20%, respectively, of the total contents of arsenic. The release of As into groundwater may occur by desorption from the mineral surface driven by reductive dissolution of the Fe oxide minerals. Furthermore, small proportions of As associated with iron sulfides occur in the reductive sediments.     

Nature and origin of arsenic carriers in shallow aquifer sediments of Bengal Delta,India

Sediments from shallow aquifers in Bengal Delta, India have been found to contain arsenic. Rivers of Ganga-Brahmaputra system, responsible for depositing these sediments in the delta, have created a store of arsenic. Geomorphological domains with different depositional styles regulate the pattern of distribution of zones with widely different content of groundwater arsenic. The high arsenic zones occur as narrow sinuous strips confined to channel deposits. A few iron-bearing clastic minerals and two post-depositional secondary products are arsenic carriers. Secondary siderite concretions have grown on the surface of the clastic carriers in variable intensity. The quantity of arsenic in all clastic carriers is in excess of what is generally expected. Excess arsenic is contributed by the element adsorbed on the concretion grown on the surface of the carriers, which adds up to the arsenic in the structure of the minerals. Variable abundance of concretions is responsible for the variable quantity of arsenic in the carriers and the sediment samples. Fe²⁺ for the growth of siderite concretions is obtained from the iron-bearing clastic carriers. The reaction involves reduction of trivalent iron to bivalent and the required electron is obtained by transformation of As³⁺ to As⁵⁺. It is suggested that oxidation of As³⁺ to As⁵⁺ is microbially mediated. In the Safe zone arsenic is retained in the carriers and groundwater arsenic is maintained below 0.05 mg/l. In the Unsafe zone sorbed arsenic is released from the carriers in the water through desorption and dissolution of concretion, thereby elevating the groundwater arsenic level to above 0.05 mg/l.     

Spherules from the Late Cretaceous Phosphorite of the Fatehgarh Formation, Barmer Basin, India

A first report of discovery of spherules, glassy balls, highly magnetic fine dust and microbracciated matrix in the Fatehgarh Formation of Barmer Basin, Rajasthan, India is being presented in this paper. The Fatehgarh Formation is a mixed siliciclastic, carbonate and phosphorite formation of Cretaceous age in the Barmer Basin that comprises sediments of Middle Jurassic to Lower Eocene age. The phosphorite zone in the Fatehgarh Formation is 8 metre-thick zone that comprises phosphatic sandstone, bone bed, bedded phosphorite and phosphatic and non phosphatic gastropod beds. The spherules occur in a thin phosphatic-clay mud and silt band of bone bed, which also yielded a very rich and diverse microvertebrate assemblage with a dominant Late Cretaceous (Maastrichtian) form of Igdabatis along with forms comprising of Semionodontid, Lapisosteum and Enchodontid. The end Cretaceous is marked for a mass extinction of numerous species including dinosaurs. An extraterrestrial impact is interpreted as the reason for this mass extinction. Whether these spherules are related to the volcanic source or K/T Boundary impact ejecta found at Caribbean and Gulf of Mexico region needs detailed chemical and age characterization for which study is in progress.