Browsing by Subject "Turbidites"
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Item Detrital zircon U-Pb and (U-Th)/He geo-thermochronometry and submarine turbidite fan development in the Mio-Pliocene Gulf of California, Fish Creek-Vallecito Basin, southern California(2014-08) Cloos, Michael Ethan; Steel, R. J.; Stockli, Daniel F.The Fish Creek-Vallecito Basin exposes an archive of sediment related to early rifting of the Gulf of California beginning at 8.0 Ma followed by Colorado River delta progradation from 5.3-3.0 Ma. Mio-Pliocene deposits from the Fish Creek-Vallecito Basin of southern California and a sample from the modern Colorado River delta were analyzed through detrital zircon U-Pb (n=1996) and (U-Th)/He (n=280) double-dating in order to better constrain sediment provenance, hinterland exhumation, and Colorado River evolution. Coupling this dataset with outcrop study of the first Colorado River-sourced turbidites into the basin at 5.3 Ma, allows for evolution of the Colorado River system to be viewed from a source-to-sink perspective. Detrital zircon U-Pb and (U-Th)/He (ZHe) ages obtained in this study suggest earliest derivation of sediment was from the Peninsular Ranges followed by more distant sediment sourcing from the Colorado River. Initial Colorado River-sourced deposits show Yavapai-Mazatzal U-Pb ages with Laramide ZHe ages suggesting that the river was sourcing from Laramide basement cored uplifts at the onset of deposition into the Gulf of California, supporting a top-down model of river evolution. An increased percentage of Grenville U-Pb age grains as well as a wider range of ZHe ages associated with western US basement-derived zircon from a modern Colorado River delta sample indicate erosion into older stratigraphic units through time which is consistent with deep erosion on the Colorado Plateau since ~6 Ma. Vertically measured sedimentology logs through the Wind Caves Member, the first Colorado River-sourced unit deposited, were used to determine slope and basin floor architecture as the Colorado River and delta dispersed subaqueous sediment gravity flows into the marine Gulf. Measured sections arrayed along depositional strike show a 4.5 km wide pod of sand-rich turbidites that were delivered through a broad Fish Creek exit point from the paleo-Colorado shelf. The vertical sedimentation trend is one showing thick bedded, amalgamated channelized and sheet-like sandstones initially, shifting to thinnerbedded sheets and more isolated channels higher in the increasingly muddy section. The facies variability up section is interpreted as a change from a submarine basin floor fan to a lower slope environment as the Colorado River prograded its delta into the Gulf.Item Late Cretaceous turbidites, Heidrun field, Norwegian Continental Shelf(2011-05) Ramnarine, Sarika Kala; Moscardelli, Lorena Gina, 1977-; Fisher, WilliamThe Heidrun field is located in the Halten Terrace of the Mid-Norwegian Continental Shelf and is one of the first giant oil fields found on the Norwegian Sea. Modern 3D seismic reflection data acquired over the field, as well as well data were used to define the key structural and stratigraphic elements within the study area. The basic geologic history of the Heidrun field is typical of most North Sea plays, and includes Triassic rift sequences that are masked by the reactivation of bounding faults that were active during the Jurassic rift phase. This rifting phase was followed by deposition of marine black shales and subsequent carbonaceous shales during the Latest Jurassic to Earliest Cretaceous. The next sequence was characterized by the deposition of Paleocene-Eocene boundary tuffs, which were formed due to volcanism associated with a rifting event that separated Norway and Greenland. Finally, an Eocene to present passive margin marine sequence is dominant over the study area that is mainly composed by glacial deposits. Traditional reservoir intervals within the Heidrun field are located within the Jurassic age inter-rift sequence. However, most recently Cretaceous-age turbidites have been explored in the Norwegian and North Sea as possible targets with some success. These Cretaceous turbidites are traditionally found as basin floor fan deposits within rifted deeps along the Norwegian continental shelf and are believed to be sourced from localized erosion of Jurassic- age rifted highs. Data within our study area revealed the existence of a deep-water Cretaceous age wedge located within the downthrown hanging wall of several smaller half-grabens formed on the Halten Terrace. Seismic attribute extractions taken within this Cretaceous wedge show the presence of several elongate to lobate bodies that seem to cascade over fault-bounded terraces associated with the rifted structures. These high amplitude elongated bodies are interpreted as proximal sedimentary conduits that are time equivalent to the Cretaceous basin floor fans located in more distal portions of the basin to the west. Several wells penetrate the updip, tilted half-graben hanging walls which are believed to be sourcing these turbidite systems. These half graben fills have the potential to contain high quality Cretaceous sandstones that might represent a potential new reservoir interval within the Heidrun field.Item Morphodynamics and geometry of channels, turbidites and bedforms(2011-12) Peyret, Aymeric-Pierre Bernard; Mohrig, David; Kocurek, Gary; Kim, Wonsuck; Lake, Larry W.; Fulthorpe, CraigThe evolution of landscapes and seascapes in time is the result of the constant interaction between flows and topography. Flows change topography, which in turn change the flow. This feedback causes evolution processes to be highly non-linear and complex. When full analytical derivations of the co-evolution of topography and flow are not possible without oversimplifications, as is the case in river bends, recent large topographical datasets and modern computers allow for correlations between horizontal (planview) and cross-sectional geometry of channels. Numerical analysis in the Mississippi and Trinity rivers indicate that the type of correlation between river radius of curvature and bankfull channel width depends on the migration behavior of the river. In other cases, channel topography may only have a second-order effect on its own evolution, as is the case for fully depositional turbidity currents, and the evolution of aeolian field topography may only be a function of this topography. I show that in these situations, changes in topography may be decoupled from details of the flow field and modeled very easily with a good accuracy.