The Experts below are selected from a list of 117 Experts worldwide ranked by ideXlab platform
Wolfgang Zacher - One of the best experts on this subject based on the ideXlab platform.
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Major-element analysis of cyclic black Shales: Paleoceanographic implications for the early Cretaceous deep western Tethys
Paleoceanography, 1999Co-Authors: Ulrich G. Wortmann, Reinhard Hesse, Wolfgang ZacherAbstract:Lower Cretaceous sediments are frequently characterized by a well expressed cyclicity. While the processes influencing environments above the carbonate compensation depth (CCD) are reasonably well understood, almost nothing is known about the deep ocean. Cretaceous sub-CCD sediments from the Tethys and Atlantic Oceans typically show rhythmic black/Green Shale successions. To gain insight into the nature of these black/Green Shale cycles, we performed detailed geochemical analyses (X-ray fluorescence, Rock-Eval and reactive iron analysis) on a 3 m long section of latest Aptian age. The major-element distribution of the analyzed Shale sequence indicates a periodic change from a high-productivity and well-oxygenated Green Shale mode to a low-productivity oxygen-deficient black Shale mode. It is proposed here that the preservation of organic matter was dependent on the strength of salinity-driven deepwater generation. Furthermore, the data show that the Corg content covaries with changes in the detrital composition. Therefore we hypothesize that Tethyan deepwater circulation was sensitive to changes in the monsoonal system. Time series analysis suggests that these changes are periodic in nature, although we are currently unable to prove that the dominant periodicity is related to the precession component of the Milankovitch frequencies.
Ulrich G. Wortmann - One of the best experts on this subject based on the ideXlab platform.
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Major-element analysis of cyclic black Shales: Paleoceanographic implications for the early Cretaceous deep western Tethys
Paleoceanography, 1999Co-Authors: Ulrich G. Wortmann, Reinhard Hesse, Wolfgang ZacherAbstract:Lower Cretaceous sediments are frequently characterized by a well expressed cyclicity. While the processes influencing environments above the carbonate compensation depth (CCD) are reasonably well understood, almost nothing is known about the deep ocean. Cretaceous sub-CCD sediments from the Tethys and Atlantic Oceans typically show rhythmic black/Green Shale successions. To gain insight into the nature of these black/Green Shale cycles, we performed detailed geochemical analyses (X-ray fluorescence, Rock-Eval and reactive iron analysis) on a 3 m long section of latest Aptian age. The major-element distribution of the analyzed Shale sequence indicates a periodic change from a high-productivity and well-oxygenated Green Shale mode to a low-productivity oxygen-deficient black Shale mode. It is proposed here that the preservation of organic matter was dependent on the strength of salinity-driven deepwater generation. Furthermore, the data show that the Corg content covaries with changes in the detrital composition. Therefore we hypothesize that Tethyan deepwater circulation was sensitive to changes in the monsoonal system. Time series analysis suggests that these changes are periodic in nature, although we are currently unable to prove that the dominant periodicity is related to the precession component of the Milankovitch frequencies.
Pierre St-julien - One of the best experts on this subject based on the ideXlab platform.
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The Saint‐Daniel Melange: Evolution of an accretionary complex in the Dunnage Terrane of the Quebec Appalachians
Tectonics, 1992Co-Authors: Pierre A. Cousineau, Pierre St-julienAbstract:The Saint-Daniel Melange is part of a series of melanges located along the Baie Verte-Brompton line in the Northern Appalachians. This line marks the suture between rocks of oceanic affinities and those of the ancient passive margin of North America with which they collided during the Taconian (Middle to Late Ordovician) orogeny. The Saint-Daniel Melange contains a wide variety of lithologies including well-bedded to dismembered sedimentary sequences, pebbly mudstone, olistostromes, and slivers of igneous and metamorphic rocks. Black Shales with interbeds of Green Shale, calcareous siltstone, or sandstone are the dominant units. They exhibit various stages of melange formation such as those present in shallow parts of an accretionary complex. Units of oceanic origin include sediments derived from the forearc basin and slivers of an ophiolite and of a magmatic arc. Units derived from sediments of the passive margin of North America are also present. The ratio between these various lithologies changes greatly within the melange on a kilometric scale along strike. The Saint-Daniel Melange is a structural complex in which the various units were assigned a sequential order mimicking a stratigraphic order. The Saint-Daniel Melange is interpreted as the relict of an accretionary complex because of its actual structural position within the Northern Appalachians and because all its lithologies and their structural fabric can be found in modern accretionary complexes.
Sadegh Elyasi - One of the best experts on this subject based on the ideXlab platform.
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petroleum source rock potential of the piranj oil field zagros basin
Marine and Petroleum Geology, 2016Co-Authors: Sadegh ElyasiAbstract:Abstract Zagros basin constitutes one of the most prolific hydrocarbon producing habitats and the second largest basin in the Middle East. The Piranj oil field is part of The Middle Cretaceous–Early Miocene Petroleum System in Zagros basin and southwest of Iran. This study mainly focuses on organic matter characterization and thermal history of two potential source rock's name Gurpi and Pabdeh formations. To evaluate the candidate source rocks, 50 cuttings and core samples of these rock units from well M-11 (the only well drilled up to the probable source rocks) were analysed, using Rock-Eval pyrolysis and organic petrography. In addition, 1D basin modelling and reconstruction of burial history were applied to analyse the thermal history of these source rocks. The Green Shale, limestone and marls of Pabdeh formation with average 2.52%wt Total Organic Matter (TOC) and Hydrogen Index (HI) higher than 250 is more favourite source rock in comparison with dark Shale and limestone of Gurpi formation by 1.8%wt and HI R ) (from 0.44% to 1.23%) indicate that samples from the well M-11 have reached maturities corresponding to early to peak oil generation. Reconstruction of the thermal history suggests various steady heat flow values (53–91 mW/m 2 ) resulted in the best fit between the observed and the calculated bottom hole temperatures (BHT) and Vitrinite reflectance (V R ) in the model. Rock-Eval pyrolysis results and Vitrinite reflectance (V R ) suggest that the most of samples are in the early mature to mature stage of hydrocarbon generation. Furthermore, according to the modelling results, petroleum generation from the studied source rocks has began after deposition of related seal-rocks and formation of traps which ensures entrapment and preservation of migrated hydrocarbon.
Minoru Ikehara - One of the best experts on this subject based on the ideXlab platform.
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Sedimentology of the Paleoproterozoic Kungarra Formation, Turee Creek Group, Western Australia: A conformable record of the transition from early to modern Earth
Precambrian Research, 2015Co-Authors: Martin J. Van Kranendonk, Rajat Mazumder, Kosei E. Yamaguchi, Koji Yamada, Minoru IkeharaAbstract:Abstract This paper presents the first, detailed sedimentological analysis of the Paleoproterozoic Kungarra Formation, the lowermost of three formations comprising the Turee Creek Group in Western Australia, which was deposited across the rise in atmospheric oxygen (the Great Oxidation Event, or GOE) and the transition from early to modern Earth. The data show that the Kungarra Formation has a gradational, conformable lower contact with underlying banded iron-formation of the Hamersley Group and predominantly comprises an upward-shallowing succession from deepwater Shales and siltstones, through rippled fine-grained sandstones and stromatolitic carbonates, to tidal flat deposits that immediately underlie coastal–fluvial deposits of the overlying Koolbye Formation. At the base of the Kungarra Formation is a gradual transition from alternating units of magnetic Green Shale and thin units of banded iron-formation that pass upsection to units of non-magnetic Shale and ferruginous chert and grey chert, reflecting a gradual loss of iron from the world's oceans accompanying the rise of atmospheric oxygen. A falling stage systems tract is recognised above this transition in the Hardey Syncline area, capped by stromatolitic carbonates and a period of exposure marked by an erosional unconformity and carbonate beachrock. Two glacio-eustatic cycles are recognised within the middle to upper parts of the Kungarra Formation, each of which is marked by the rapid onset of falling systems tracts and characterised by falling systems tracts during and following diamictite deposition. Stratigraphic data are used to infer a depobasin filled by a sediment wedge prograding from southeast to northwest, in contrast to previous models of a north-northeastward deepening foreland basin. The lack of seismites or internal unconformities within the formation precludes a foredeep setting. Rather, deposition is interpreted as having occurred within an intracratonic basin, with detritus sourced from erosion of uplifted bedrock to the southeast.
