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  • 1
    Publication Date: 2010-04-01
    Description: In south-central Turkey, a carbonate platform system of early middle Miocene age is exposed in three-dimensional outcrops displaying a rich variety of carbonate facies associated with exceptionally well-preserved depositional geometries. This paper presents a detailed reconstruction of the geometries and facies organization across the prograding margin of one intra-platform carbonate bank that grew during the Langhian on the Ermenek Platform. The total thickness of the margin is approximately 250 m, and it has prograded over a distance of 1.2 km. The geometrical pattern shows an alternation between sigmoid, sigmoid-oblique, and oblique accretionary units at different scales. Based on the facies distribution and the geometrical framework two large-scale depositional sequences and eight medium-scale depositional sequences were defined. The general evolution from a low-angle shelf geometry to a prograding flat-topped platform was associated with an evolution from oligophotic-dominated carbonate producers, such as large benthic foraminifera, molluscs, echinoderms, red algae and bryozoans at the base, to mesophotic and euphotic carbonate producer organisms, such as corals, red algae and porcellaneous small benthic foraminifera at the top. The eight medium cycles were defined primarily using the depositional geometries, since facies changes were observed only locally within these cycles. Several mechanisms influenced the stratigraphic architecture of this margin: (1) eustatic sea-level controlled the overall transgressive-regressive Langhian sequence, and two superposed large-scale sequences. Medium cycles were probably also influenced by higher frequency sea-level fluctuations; (b) climate change probably influenced the overall evolution of the faunal assemblage; and (c) antecedent topography determined the overall architecture of a shelf bordering a deeper basin.
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  • 2
    Publication Date: 2003-01-01
    Description: A 3D stratigraphic database has been constructed from the inspection of 1100 wells and outcrops in the Paris basin. The database contains 88 surfaces correlated at high temporal resolution using sequence stratigraphy. For each well and each surface, the present-day depth, the depositional environment and the lithology between two layers are available. This database provides a key to quantify the tectonics associated with this intracratonic basin and to model the thermal and mechanical processes at the origin of the tectonics. Three types of numerical modelling have been carried out in order (1) to better constrain the long-term thermal subsidence and its cause, (2) to characterize the spatial and temporal evolution of the crustal tectonics during the extensional' period and (3) to test a lithospheric folding origin during the end-Cretaceous to present-day compressional period. The philosophy of these three models are different. The Chablis model for the lithospheric thermal evolution is used to predict the long-term subsidence of the Paris Basin. The thermal evolution of the lithosphere is computed, taking account of a constant temperature or heat flow at the base of the lithosphere, temperature- and pressure-dependent thermal characteristics, metamorphism in the crust, top-crustal erosion and phase transition in the mantle. The long-term subsidence of the Paris basin results from the decay of a thermal anomaly initiated during late Variscan times. The subsidence data can be explained by short- (Stephano-Autunian) as well as long- (Stephano-Triassic) lasting extension. These hypotheses both implicitly refer to extensional collapse of the Variscan belt. The characterization of the spatial and temporal evolution of the crustal tectonics during the thermal relaxation period has been need to quantify the local effect of the sediment load on vertical crust movements. From sedimentary thickness and bathymetric data, maps of relative tectonics have been drawn at a time scale around 500 ka. These maps show two different tectonic behaviours: (1) narrow regions with a high horizontal gradient of tectonics (faults), and (2) domains with a diffuse subsidence correlated with topographic domes and high rates of sedimentation. The geometrical and temporal characteristics of the regions of diffuse subsidence are compatible with a model of flow of the lower crust if the thickness of the flowing channel is at least 20 km with a viscosity of 1020 Pas. The Tertiary characteristics of the Paris Basin could be the record of large-scale lithospheric folding. The numerical experiments demonstrate that extremely low (0.2 mm a-1) shortening rates are largely sufficient to induce large-scale low-amplitude folding under low maximum values of tectonic stresses (c. [~]50 MPa). These values suggest that alpine compression is largely sufficient to activate this deformation. From the data collected in this database and from the models described here, the evolution of the Paris Basin is better understood. The Paris Basin Meso-Cenozoic evolution can be described as a long-term thermal subsidence, inherited from the Permian extension and perturbed by intraplate deformations in reaction to the geodynamic events occurring in western Europe, i.e. the Ligurian Tethys opening and closure, and the Atlantic opening. Those tectonic events modify in space and time both subsidence and facies distributions. The Paris Basin was initially an extensional' basin which progressively evolved into a compressional one, temporarily (lower Berriasian and late Aptian) and then permanently (late Turonian to present day). The present-day geometry of the Paris Basin is the consequence of lithospheric folding occurring mainly during the Tertiary. In consequence, (1) the Paris Basin is not still a subsiding basin but an uplifted area, and (2) during the Jurassic and part of the Cretaceous, the surrounding present-day outcropping basement massifs were subsiding areas flooded by the sea.
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  • 3
    Publication Date: 2019-07-19
    Description: Onboard the Mars Science Laboratory (MSL) Curiosity rover, the ChemCam instrument consists of :(1) a Laser-Induced Breakdown Spectrometer (LIBS) for elemental analysis of the targets [1;2] and (2) a Remote Micro Imager (RMI), for the imaging context of laser analysis [3]. Within the Gale crater, Curiosity traveled from Bradbury Landing through the Rocknest region and into Yellowknife Bay (YB). In the latter, abundant light-toned fracture-fill material were seen [4;5]. ChemCam analysis demonstrate that those fracture fills consist of calcium sulfates [6].
    Keywords: Geophysics
    Type: JSC-CN-31277 , International Conference on Mars; Jul 14, 2014 - Jul 18, 2014; Pasadena, CA; United States
    Format: application/pdf
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  • 4
    Publication Date: 2019-07-13
    Description: Sedimentary rocks examined by the Curiosity rover at Yellowknife Bay, Mars, were derived from sources that evolved from an approximately average martian crustal composition to one influenced by alkaline basalts. No evidence of chemical weathering is preserved, indicating arid, possibly cold, paleoclimates and rapid erosion and deposition. The absence of predicted geochemical variations indicates that magnetite and phyllosilicates formed by diagenesis under low-temperature, circumneutral pH, rock-dominated aqueous conditions. Analyses of diagenetic features (including concretions, raised ridges, and fractures) at high spatial resolution indicate that they are composed of iron- and halogen-rich components, magnesium-iron-chlorine-rich components, and hydrated calcium sulfates, respectively. Composition of a cross-cutting dike-like feature is consistent with sedimentary intrusion. The geochemistry of these sedimentary rocks provides further evidence for diverse depositional and diagenetic sedimentary environments during the early history of Mars.
    Keywords: Exobiology
    Type: GSFC-E-DAA-TN21724 , Science (ISSN 0036-8075) (e-ISSN 1095-9203); 343; 6169; 1244734
    Format: text
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  • 5
    Publication Date: 2019-07-13
    Description: Onboard the Mars Science Laboratory (MSL) Curiosity rover, the ChemCam instrument consists of : (1) a Laser-Induced Breakdown Spectrometer (LIBS) for elemental analysis of the targets and (2) a Remote Micro Imager (RMI), for the imaging context of laser analysis. Within the Gale crater, Curiosity traveled from Bradbury Landing through the Rocknest region and into Yellowknife Bay (YB). In the latter, abundant light-toned fracture-fill material occur. ChemCam analysis demonstrates that those fracture fills consist of calcium sulfates.[
    Keywords: Lunar and Planetary Science and Exploration; Geophysics
    Type: JSC-CN-30424 , Lunar and Planetary Science Conrference; Mar 17, 2014 - Mar 21, 2014; The Woodlands, TX; United States
    Format: application/pdf
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  • 6
    Publication Date: 2019-07-13
    Description: The Mars Science Laboratory (MSL) mission is focused on assessing the past or present habitability of Mars, through interrogation of environment and environmental records at the Curiosity rover field site in Gale crater. The MSL team has two methods available to collect, process and deliver samples to onboard analytical laboratories, the Chemistry and Mineralogy instrument (CheMin) and the Sample Analysis at Mars (SAM) instrument suite. One approach obtains samples by drilling into a rock, the other uses a scoop to collect loose regolith fines. Scooping was planned to be first method performed on Mars because materials could be readily scooped multiple times and used to remove any remaining, minute terrestrial contaminants from the sample processing system, the Collection and Handling for In-Situ Martian Rock Analysis (CHIMRA). Because of this cleaning effort, the ideal first material to be scooped would consist of fine to very fine sand, like the interior of the Serpent Dune studied by the Mars Exploration Rover (MER) Spirit team in 2004 [1]. The MSL team selected a linear eolian deposit in the lee of a group of cobbles they named Rocknest (Fig. 1) as likely to be similar to Serpent Dune. Following the definitions in Chapter 13 of Bagnold [2], the deposit is termed a sand shadow. The scooping campaign occurred over approximately 6 weeks in October and November 2012. To support these activities, the Mars Hand Lens Imager (MAHLI) acquired images for engineering support/assessment and scientific inquiry.
    Keywords: Lunar and Planetary Science and Exploration
    Type: JSC-CN-27937 , Lunar and Planetary Science Conference; Mar 18, 2013 - Mar 22, 2013; The Woodlands, TX; United States
    Format: application/pdf
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  • 7
  • 8
    Publication Date: 2006-03-30
    Description: The purpose of this paper is to document the influence of depositional environments on shallow-water, low-relief clinoforms from the description of five ancient carbonate platforms: the Neoproterozoic (Namibia), Middle Jurassic (France), Lower Cretaceous (France), Upper Cretaceous (Oman) and Miocene (Turkey). These examples have been investigated on the basis of field observations. The clinoforms are described with reference to geometric and compositional attributes: declivity, shape, height, sedimentary structures, sediment fabric and components. The results show great variability in stratal geometry, declivity and facies distribution: (1) depositional profiles vary from exponential, to sigmoidal, to oblique; (2) maximal slope angles range from 3 to 25°, most of them being grouped between 10 and 18°; (3) facies differentiation identified from lateral facies successions along beds, and vertical facies successions through beds, is pronounced to subtle. This study documents linkages between depositional environments and clinoform attributes. Proximal/shallow clinoforms display round-edged exponential profiles. Sediment deposition has resulted from unidirectional currents in the upper convex section, and storm-generated oscillatory currents in the lower concave part. The sediment fabric changes gradually along this type of clinoform. There is little vertical facies differentiation through these clinobeds which have formed from a continuous amalgamation of deposits. By contrast, distal clinoforms (shelf break, distally steepened ramp settings) yield a much broader spectrum of profiles and are generally shorter and steeper. Sedimentary structures in gravel-sized deposits of the upper slope indicate pure traction by unidirectional currents. Conversely, marks of oscillatory flows (undular, wavy top bounding surfaces of clinobeds) are common in the lower slope. Intercalation of massive, fine-grained deposits suggests offshore transport of carbonate mud by suspension. Each distal clinobed represents a single flow event. Accordingly, facies differentiation is weak laterally but may be pronounced through the clinobeds. Our study suggests that low-relief forms of proximal/shallow environments, which contain coarse-grained and photo-independently produced debris, record hydrodynamic equilibrium profiles, whereas the higher-relief forms of this setting rather reflect a high differential production rate of carbonate sediment with water depth. The carbonate sediment of the distal clinobeds mainly derives from skeletal production by oligophotic and photo-independent biota of the middle shelf/ramp and upper portion of the clinoforms. The contribution by in situ skeletal biota only becomes significant on the lower slope, indicating that the distal, submerged slopes of carbonate platforms are not organically but hydrodynamically generated. Our compilation shows that the slope angles of shallow marine, low-relief clinoforms do not simply correlate to the sediment grain size and fabric, in contrast to what has been documented for the high, linear slope profiles. This difference stems from the depositional settings, namely the involved transport mechanisms. Low-relief clinoform accretion seems to be dominantly influenced by wave-induced sediment transport, in contrast to linear flanks of high-relief clinoforms that build to the angle of repose, and for which gravity is the primary transport process.
    Print ISSN: 0016-7568
    Electronic ISSN: 1469-5081
    Topics: Geosciences
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  • 9
    Publication Date: 2003-08-01
    Print ISSN: 0012-821X
    Electronic ISSN: 1385-013X
    Topics: Geosciences , Physics
    Published by Elsevier
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  • 10
    Publication Date: 2004-12-01
    Description: A quantitative stratigraphic model of mixed carbonate/siliciclastic continental shelves is presented to investigate the relationships between depositional processes and stratigraphic responses at longterm, large spatial scales. A diffusion model is combined with a fluid-flow approach to simulate both long-term factors, i.e. the processes controlling large-scale architecture, and short-term processes, i.e. sediment redistribution by storms. Any net sediment accumulation is the result of the succession of a storm and a fair-weather period. Sediments are mobilized by waves and advected by low-frequency currents during storm events. Sediments are then reworked and redistributed downslope by diffusive processes during fair-weather period. The results are successful in capturing several major characteristics of both modern and ancient depositional systems (geometry, differential preservation, net accumulation rates). The study highlights the importance of waves and unidirectional currents. Depositional geometry and shelf morphology depend on the balance between available sediment supply (generated in situ or detrital) and the transport energy, which is related to the style of sediment transport (diffusive or advective), and to the magnitude and frequency of storms. © 2004 Blackwell Publishing Ltd.
    Print ISSN: 0950-091X
    Electronic ISSN: 1365-2117
    Topics: Geosciences
    Published by Wiley
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