Description stratigraphique de la région des Alpes du Sud.

Le Massif de Peyre Haute est constitué de trois nappes qui se superposent : - nappe de Champcella - nappe supérieur du Guil ou de Peyre Haute - nappe du flysch de Furfande Cette étude en décrit la stratigraphie.

<p>The architecture, distribution and facies of sandstone bodies in the Gog Group of the southern Rocky Mountains of western Canada record the dynamics of sand movement on the broad continental shelf of West Laurentia during the Early Cambrian phase of worldwide transgression. This study focuses on the stratigraphy, sedimentology and ichnology in the Bow Valley region, specifically the sector from Mount Assiniboine northwest to the North Saskatchewan River. The objectives of this project were several-fold: (1) revise the existing stratigraphic nomenclature; (2) document the sedimentary facies; (3) identify facies assemblages and interpret them in terms of sedimentary processes and environments; (4) characterize sandstone body geometries; (5) develop a sequence-stratigraphic framework; (6) document trace-fossil occurrences; and (7) characterize different trace-fossil assemblages in terms of colonization trends and prevailing paleoenvironmental conditions.</p> <p>The Gog Group in this area has historically comprised four units, the Fort Mountain, Lake Louise, St. Piran and Peyto formations. North of Bow Pass an additional unit, the Jasper Formation, occurs below the Fort Mountain Formation and is related to accommodation created by active rift-faulting during the latest Neoproterozoic. In the Lake Louise and Lake O'Hara area, four new formal subdivisions within the St. Piran Formation are proposed: Lake O'Hara, Lake Oesa, Lake Moraine and Wiwaxy Peaks members.</p> <p>The sequence stratigraphy of tide-dominated setting has yet not been fully explored. The stratal architecture of the Lake O'Hara and Lake Oesa members reveals a new mechanism for the formation of the regressive surface of marine erosion landward of the lever point of balance between sedimentation and erosion in the subtidal environment. As the shoreline is forced to regress with falling sea level, the laterally continuous tidal flats advance and the preexisting shallow-subtidal compound dunes are scoured by strong tidal currents that carve gradually a new equilibrium profile. We argue that the accretion of intertidal flats on top of subtidal sands is an overlooked yet predictable component of falling-stage systems tracts in tide-dominated settings.</p> <p>The Gog Group also offers an opportunity to explore animal-sediment relationships in a high-energy setting, during the early phase of Phanerozoic diversification. The presence of constrasting ichnofabrics within a single Early Cambrian sand-sheet complex illuminates how the colonisation trends of suspension and detritus feeders were controlled by factors specific to the various subenvironments.<p> <p>The variety of sandbody types in the Gog Group reflects varying sediment supply and location on the inner continental shelf. Five types of compound cross-stratified sandstone are distinguished based on foreset geometry, sedimentary structures and internal heterogeneity. These represent five broad categories of subtidal sandbodies: (1) compound-dune fields; (2) sand sheets; (3) sand ridges; and (4) patchy dunes. Trace-fossil distribution in these tide-dominated sand bodies and adjacent sediments is mostly controlled by an interplay of substrate mobility, grain size, turbidity, water-column productivity, and sediment organic matter. Salinity is a critical factor in marginal-marine locations but played no role in this region of the shelf.</p>

Approche stratigraphique, géologique du Mont Ventoux.

The Maldives atolls, the very top of one of the largest modern carbonate platforms, occupy the central and largest part of the Chagos-Laccadives ridge located in the equatorial Indian Ocean. In the central part of the archipelago, the large atolls form two parallel north-south relatively continuous chains surrounding an internal basin, the Inner Sea, with water depths not exceeding 550 m. The Maldives carbonate system, uniquely evolved through a combination of global sea level fluctuations, subsiding history, and more regional seasonally varying monsoon circulation. Although the long-term evolution of this system is relatively well-established, the understanding of the detailed evolution of the Maldives carbonate edifice in the last 5 million years has remained limited. The latest phase of its stratigraphic evolution is explained by a shift from a well-developed Miocene-Pliocene progradational pattern to a mostly late Pliocene-Quaternary aggradational depositional signature. This last aggradation phase, forming the atolls the way we know them today, consists of stacked inner neritic limestone sequences, separated by a series of exposure horizons. The succesive periods of atoll exposure and re-flooding are recorded in the Inner Sea by late Pliocene-Quaternary glacial/interglacial clearly cyclic deposition of periplatform oozes. This cyclic sedimentary pattern also appears in the internal prograding geometry of carbonate drifts in the Inner Sea. A200 m-thick deep carbonate sediment drift was first observed on a Shell E-W seismic line north of Gaafaru Falhu atoll in the NE corner of the Maldives Inner Sea, in a range of water depths from ~300 to 500 m. During the NEOMA 2007 research cruise on the RV Meteor lead by Universität Hamburg, the deep water sandy drift in the area north of Gaafaru Falhu atoll and an adjacent deeper muddy drift was extensively surveyed via 12 kHz multibeam bathymetry, a 4 kHz sub bottom profiler (Atlas Hydrographics), multi channel high resolution seismics, and three box and piston cores. My study focuses on understanding the Plio-Quaternary overall evolution of the set of adjacent sandy and muddy drifts, just north of Gaafaru Falhu Atoll. The sandy and muddy drift interconnected internal geometries observed in the available seismic data sets are integrated into a sequence stratigraphic framework. Analyses of two piston cores collected from the upper part of the muddy drift and a box core from the top of the sandy drift determine the overall downcore lithology variations and made possible the development of high-resolution chrono and cyclo-stratigraphies. In the muddy drift periplatform sequence, downcore cyclic variations in, (1) sediment coarse fraction, (2) Sr counts as proxy for atoll-derived fine aragonite, (3) planktic foraminifer oxygen stable isotope composition, in addition to carbonate preservation and biostratigraphic markers, were determined. These downcore lithologic and geochemical variations in the muddy drift were tied to the seismic lines imaging the sandy-muddy drifts to resolve the timing of the carbonate sandy drift establishment and its overall evolution. Based on this aforementioned interpretation, the results of my research document the nature and timing of the longer-term evolution of the sandy and muddy drifts over multiple glacial-interglacial sea level cycles in the last 3 million years. Once the timing of the drift was determined, the prograding internal architecture of the sandy drift was examined and interpreted in the context of the relatively well-established Plio-Pleistocene sea level fluctuations and the bottom current variations

The current study has evaluated shoreline dynamics and environmental change at St. Catherines Island, Georgia, with attention to the two major controls of barrier island formation and modification processes. These major controls include the increase in accommodation space, or the rate of sea level rise for the Georgia Bight which has remained constant in 20th and 21st century tide gauge data and dynamically changing rates of sediment supply based on anthropogenic modifications to land cover (Trimble, 1974) that are reflected in sediment transport (McCarney-Castle et al., 2010). Vibracoring and radiocarbon data provided valuable insights into the stratigraphy and development of St. Catherines Island. A stratigraphic model has been developed for the sediments associated with the Late Holocene accretional terrains where multiple small scale fluctuations in sea level have resulted in the formation of a sedimentary veneer punctuated with transgressive surfaces and regressive sequences. A working model for an interpolated Late Holocene sea level curve has been constructed using direct evidence from vibracore data as constraining points and indirect evidence from other regional sea level studies to provide additional structure. The relationship between the timing of the regressions versus periods of beach ridge formation and implications from the current shoreline dynamics study regarding the role of sediment supply complement each other. The ages of beach ridge formation strongly correlate to periods that are associated with regressions in sea level based on the sedimentary record and an evaluation of Late Holocene sea level conditions. The evaluation of anthropogenic modifications to the rate of sediment supply performed under the current study indicates that in spite of significant changes in sediment flux rates of +300% (pre-dam era) and -20% (post-dam era), shoreline retreat was continuous during the study period with an acceleration noted in the rates of shoreline retreat associated with spit and berm landforms during the post-dam or modern era. The two associations indicate strongly that the rate of sediment supply plays a secondary role to the major control of the rate of sea level rise in the formation and modification processes at St. Catherines Island.

The sequence stratigraphy of the middle Eocene-Pliocene of the Pannonian Basin permits to differentiate fifty-nine depositional sequences. An earlier compressional Paleogene basin in the central and eastern Pannonian Basin is unconformably overlain by a Neogene extensional basin. Tectonic regimes interacted with transgressive-regressive facies cycles. The boundaries of these cycles coincide with regional stage boundaries. Unconformities separating these cycles mark the episodic closure of connections between the Pannonian Basin and the European epicontinental seas from Oligocene through middle Miocene time. The unconformities are the result of short-term glacio-eustatic falls, sometimes enhanced by tectonic events. Within the limits of biostratigraphic resolution during the Eocene-middle Miocene, many of the sequences of the Pannonian Basin correlate well with the sequences proposed by Haq et al. (1987). However, eight sequences, i.e. one in the Lutetian, three in the Bartonian, one in the Priabonian, one in the Rupelian and two in the Burdigalian, were not identified by Haq et al. (1987). The sequences and their boundaries are directly correlated with global oxygen isotope events. Glacioeustasy generates sequence boundaries beginning as early as the middle Eocene. Within the lacustrine setting of the Pannonian Basin (late Miocene- Pliocene time) relative lake level changes appear to control the overall sequence development. However, other minor variables, the sediment supply and the topography of the initial depositional surface were additional controlling factors. Thus differences in the physiography of the basin lead to totally different sequence types that all reflect to lake level fluctuations. In lateral direction, during a short time period, these lacustrine sequences are more sensitive to changes in the initial depositional profile and sediment supply. / pages 390 and 396 are missing from text.

<p>The architecture, distribution and facies of sandstone bodies in the Gog Group of the southern Rocky Mountains of western Canada record the dynamics of sand movement on the broad continental shelf of West Laurentia during the Early Cambrian phase of worldwide transgression. This study focuses on the stratigraphy, sedimentology and ichnology in the Bow Valley region, specifically the sector from Mount Assiniboine northwest to the North Saskatchewan River. The objectives of this project were several-fold: (1) revise the existing stratigraphic nomenclature; (2) document the sedimentary facies; (3) identify facies assemblages and interpret them in terms of sedimentary processes and environments; (4) characterize sandstone body geometries; (5) develop a sequence-stratigraphic framework; (6) document trace-fossil occurrences; and (7) characterize different trace-fossil assemblages in terms of colonization trends and prevailing paleoenvironmental conditions.</p> <p>The Gog Group in this area has historically comprised four units, the Fort Mountain, Lake Louise, St. Piran and Peyto formations. North of Bow Pass an additional unit, the Jasper Formation, occurs below the Fort Mountain Formation and is related to accommodation created by active rift-faulting during the latest Neoproterozoic. In the Lake Louise and Lake O'Hara area, four new formal subdivisions within the St. Piran Formation are proposed: Lake O'Hara, Lake Oesa, Lake Moraine and Wiwaxy Peaks members.</p> <p>The sequence stratigraphy of tide-dominated setting has yet not been fully explored. The stratal architecture of the Lake O'Hara and Lake Oesa members reveals a new mechanism for the formation of the regressive surface of marine erosion landward of the lever point of balance between sedimentation and erosion in the subtidal environment. As the shoreline is forced to regress with falling sea level, the laterally continuous tidal flats advance and the preexisting shallow-subtidal compound dunes are scoured by strong tidal currents that carve gradually a new equilibrium profile. We argue that the accretion of intertidal flats on top of subtidal sands is an overlooked yet predictable component of falling-stage systems tracts in tide-dominated settings.</p> <p>The Gog Group also offers an opportunity to explore animal-sediment relationships in a high-energy setting, during the early phase of Phanerozoic diversification. The presence of constrasting ichnofabrics within a single Early Cambrian sand-sheet complex illuminates how the colonisation trends of suspension and detritus feeders were controlled by factors specific to the various subenvironments.<p> <p>The variety of sandbody types in the Gog Group reflects varying sediment supply and location on the inner continental shelf. Five types of compound cross-stratified sandstone are distinguished based on foreset geometry, sedimentary structures and internal heterogeneity. These represent five broad categories of subtidal sandbodies: (1) compound-dune fields; (2) sand sheets; (3) sand ridges; and (4) patchy dunes. Trace-fossil distribution in these tide-dominated sand bodies and adjacent sediments is mostly controlled by an interplay of substrate mobility, grain size, turbidity, water-column productivity, and sediment organic matter. Salinity is a critical factor in marginal-marine locations but played no role in this region of the shelf.</p>

The South China Sea is a region of significant importance in terms of the records of SE Asian tectonics, including Tibetan Plateau uplift, and the onset and evolution of the East Asian monsoon. The Mekong River has been a dominant sediment source since at least late Miocene time and has headwaters on the eastern Tibetan Plateau. Understanding the Pliocene to Recent stratigraphy of the paleo-Mekong Delta and associated shelf-edge deposits aids in understanding changes in accommodation, sea level, and sediment supply. This record might then be useful in interpreting the longterm history of basin evolution in the Nam Con Son Basin. Nine sequence boundaries and associated sequences are recognized along the late Miocene to latest Pleistocene shelf in the East Nam Con Son Basin. Age constraints were assigned to key stratigraphic horizons by correlating sequence boundaries with published sea level curves. Accommodation in the study area is controlled by shelf -edge compaction, rift-related thermal subsidence, non-rift-related anomalous subsidence,Two primary sources supplied sediment to the southwestern South China Sea during Pliocene to Recent time and likely include the paleo-Mekong Delta and a fluviodeltaic system originating from the Sunda Shelf, such as the Molengraaff River. Changes in thickness, area, and location of Pliocene to Recent shelf-edge delta deposits reflect changes in accommodation and sediment supply over time, as well as progradation of the shelf edge during Pliocene to Recent time and avulsion of the shelf edge delta. Anomalous subsidence of LGM shelf edge deposits is estimated at approximately 40-50 m deeper than expected. The current depth of the LGM deltaic wedge may indicate renewed rapid tectonic subsidence during the last 18,000 yrs, possible compaction effects or a combination of these. eustatic change, and shelf edge faulting.

This study is a statistical analysis of the sandstone distribution within the Arkansas Jackfork Group which is a passive margin fan complex. Passive margin fan systems are typically associated with long fluvial transport, fed by deltas, wide shelf, efficient basin transport, that result in a bypassing system. Passive margin fans are generally fine-grained, mud rich, and well sorted. These fans can be separated into three units (upper, middle, and lower fan) based on their location within the fan and how the sediments are deposited. Five outcrops from the Arkansas Jackfork Group have been chosen for this study and each were divided into different facies dependent on sandstone percentages in certain bed sets. The amount of sandstone for each facies was calculated and a statistical approximation for each outcrop was determined. Sandstone distribution curves were made for each outcrop to show a graphic representation of how the sandstone is dispersed. After analyzing different upper, middle, and lower fan outcrops, it is clear there is an obvious change in the sandstone percentage and distribution. The upper fan deposit has an overall sandstone percentage of approximately 77.5% and is deposited in beds that are mainly amalgamated; 10-30m thick. Sandstone is deposited moderately even and is quite concentrated throughout the exposure. The middle fan outcrops contain approximately 72.6% sandstone and show similar patterns, except that the amalgamated sandstone beds are not as thick, 5-15m and contain more shale in between layers. As expected the lower fan outcrop is completely different in both sandstone percentage and distribution. The lower fan has approximately 65.4% sandstone. The distribution of sandstone is more concentrated in each of the individual units, or systems, but the overall complex has two systems separated by a massive marine shale bed, 33.5 m, that contains virtually no sand.