Search results for " ROC"

Modalites sequentielles de la transgression aaleno-bajocienne sur le sud-est du Bassin parisien

2000

Abstract Sedimentologic, biostratigraphic and diagenetic studies made on Middle Aalenian to Lowermost Bathonian deposits in 25 outcrops of the Burgundy High (southeastern Paris basin) lead to a sequence stratigraphy subdivision of the early Dogger record into 7 third order depositional sequences. These sequences make up a second-order transgressive phase whose lower limit is a tectonically enhanced unconformity (the Mid-Cimmerian unconformity), associated with a large scale uplift during the Upper Toarcian and the Lower Aalenian. In the largest outcrops, where the geometry of sedimentary bodies is observable at the hectometre to kilometre scale, the combination of diagenetic, biostratigraph…

Sedimentological and deformational criteria for discriminating subglaciofluvial deposits from subaqueous ice-contact fan deposits: A Pleistocene exam…

2014

A pit located near Ballyhorsey, 28 km south of Dublin (eastern Ireland), displays subglacially deposited glaciofluvial sediments passing upwards into proglacial subaqueous ice-contact fan deposits. The coexistence of these two different depositional environments at the same location will help with differentiation between two very similar and easily confused glacial lithofacies. The lowermost sediments show aggrading subglacial deposits indicating a constrained accommodation space, mainly controlled by the position of an overlying ice roof during ice-bed decoupling. These sediments are characterized by vertically stacked tills with large lenses of tabular to channelized sorted sediments. The…

Cyclostratigraphy and high-frequency carbon isotope fluctuations in Upper Cretaceous shallow-water carbonates, southern Italy

2002

A detailed carbon isotope study has been carried out on a Santonian (Upper Cretaceous) carbonate platform succession that crops out at Monte Sant'Erasmo (southern Italy). Previous centimetre-scale studies on this succession have shown that high-frequency eustatic changes, resulting from the Earth's orbital fluctuations, controlled the hierarchical organization of the depositional and early diagenetic features in elementary cycles, bundles (groups of three to five elementary cycles) and superbundles (groups of three or four bundles). The elementary cycles, which correspond to single beds, suggest a control caused by Earth's precession; the bundles and superbundles record the short ( 100 kyr)…

Mineralogical and chemical variability of fluvial sediments: 1. Bedload sand (Ganga–Brahmaputra, Bangladesh)

2010

This study investigates the natural processes that control concentration of detrital minerals and consequently chemical elements in river sand. The novelty of our approach consists in the systematic integration of detailed textural, petrographical, mineralogical and chemical data, and in the quantitative description and modeling of relationships among mineralogical and chemical variables for each sample and each grain-size class in each sample. Bed sediment in transit in the largest sedimentary system on Earth chiefly consists of fine-grained lithofeldspatho quartzose sand including rich amphibole–epidote–garnet suites, mixed with minor very-fine grained-sand to silt subpopulations containi…

Integrated techniques to study sedimentary rocks from Sicily used in Cultural Heritage

2005

Magmatic and metamorphic development of an early to mid-Paleozoic continental margin arc in the southernmost Central Asian Orogenic Belt, Inner Mongo…

2013

The Bainaimiao arc in Inner Mongolia, China, comprises a weakly metamorphosed volcani-sedimentary sequence and alow-P/Tmetamorphic complex.In this study wepresent SHRIMP zircon ages and geochemical data to document the temporal and genetic relationships between these two tectonic units. Zircons from a rhyolite and two dacites (high-K calc-alkaline) of the volcani-sedimentary sequence yielded 206 Pb/ 238

Recension of Collins, M.E., Manchester, S.R. & Wilde, W. 2012

2020

Collins, M.E., Manchester, S.R. & Wilde, W. 2012. Fossil fruits and seeds of the Middle Eocene Messel biota, Germany.Abhandlungen der Senckenberg Gessellschaft für Naturforschung, 570, 251 pp. ISBN 978-3-510-61400-4 This book presents a survey of the extensive fruit and seed collection found at the Middle Eocene Messel site. The first part of the book is dedicated to a few introductory chapters about the site, geologic setting, age control of the sedimentary sequence and taphonomy of the fossil remains. It is worth pointing out that unlike many lacustrine deposits in which fruits are preserved as impressions, most of the Messel plant macrofossils are preserved as remnants of the original pl…

Time Markers for the Evolution and Exhumation History of a Late Palaeozoic Paired Metamorphic Belt in North-Central Chile (34°-35°30'S)

2005

A multi-method geochronological approach is applied to unravel the dynamics of a paired metamorphic belt in the Coastal Cordillera of central Chile. This is represented by high-pressure - low-temperature rocks of an accretionary prism (Western Series), and a low-pressure- high-temperature overprint in the retro-wedge with less deformed metagreywackes (Eastern Series) intruded by magmas of the coeval arc. A pervasive transposition foliation formed in metagreywackes and interlayered oceanic crust of the Western Series during basal accretion near metamorphic peak conditions (∼350-400°C, 7-11 kbar) at 292-319 Ma (

Distribution of radioactive elements in three progressively metamorphosed pelite series of the Bohemian Massif

1980

The variations of the content of radioactive elements in pelitic rocks in dependence on the grade of metamorphism were studied in three regions of the Bohemian Massif with a different character and age of metamorphism. The concentrations of Th, U and K were determined by gammaspectrometric method, the major elements Si, Ti, Al, Fe, Mn, Ca, K, P by the X-ray fluorescence method. An increasing mobility of radioactive elements was found with the help of variation diagrams in the higher stages of metamorphism, the migration being apparent especially for Th and usually starting in the garnet or biotite zone. A significant negative correlation of both Th and U content with the content of SiO2 was…

Soil erosion risk, Sicilian Region (1:250,000)

2014

Assessing the risk of soil erosion caused by water at the regional level is important for current and future planning of land use and environmental actions to combat land degradation. The gravity of the risk depends not only on the rate of soil erosion by water, but also on other factors, primarily soil depth and workability of the underlying rocks and sediments, which may be used to calculate the eroded soil. We estimate the rate of erosion by water (tons ha-1 year-1) applying the Universal Soil Loss Equation model. The map of soil content (tons ha21) to the effective rooting depth was divided by the map of soil erosion rate to obtain the risk of erosion by water in Sicily, expressed in te…