Browsing by Subject "Gulf of California"
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Item Earliest turbidite emplacement ~(6.3 -5.6 Ma) in the newly opening Gulf of California (Fish Creek-Vallecito Basin)(2015-05) Bateman, Sarah Blake; Steel, R. J.; Mohrig, David; Milliken, Kitty L; Olariu, CornelThe Fish Creek-Vallecito Basin chronicles late Miocene through Pleistocene sedimentation into the newly rifting Gulf of California. Initial rifting in the basin began around 8.0 Ma, subsequently followed by sedimentation of locally derived alluvial fan conglomerates. Subsequent deepening of the basin created conditions for deposition of subaqueous gravity flow deposits. The deposition of the initial marine sediments is known lithostratigraphically as the Lycium Member turbidites (~6.3 to 5.6 Ma) of the Latrania Formation, comprising a thick succession of coarse-grained sediment up to 115m in thickness. Sedimentation and facies distribution throughout the system is a direct result of the tectonically derived topography in this rift basin environment. Detailed study of the facies distribution and nature of the sediment fill allows for realization of models of facies variability in rift basin environments. Deposition of this turbidite succession is somewhat problematic. A significant run-out distance as well as water depth is needed to deposit a turbidite succession of this magnitude and although there is currently no field evidence of a transitional shoreline or delta system previous detrital zircon analysis suggests a possible more northerly source. This study aims to seek out the processes which led to a thick turbidite succession in an early rift basin sequence and provide a complete picture of source-to-sink deposition. In depth analysis of turbidite architecture variability was conducted using over 500 m of outcrop logged section taken laterally throughout the 7 km outcrop belt. Lithofacies and architectural variability, reconstructed and imaged using correlation of high resolution sections and photo panel interpretations, show a transition from a proximal to distal basin floor fan environment. Provenance data, constrained through petrographic inspection of samples taken systematically throughout the system, indicate that the initial marine sediments deposited in the Miocene-Gulf of California are derived from the neighboring Peninsular Range Batholith. In depth stratigraphic analysis coupled with provenance study allows us to decipher the depositional history and basin paleogeography during initial marine inundation into the newly formed Gulf of California. A paleogeographic model of the Late Miocene (~6.3 to 5.6 Ma) is proposed. Sediment was transported from the northwest to the southeast along the West Salton Detachment Fault, depositing in a basin floor fan system.Item Mass transport deposit and turbidite interaction in the Mio-Pliocene Gulf of California : Fish Creek-Vallecito Basin, Salton Trough(2015-05) Slaugenwhite, Jeremy Scott; Steel, R. J.; Mohrig, David; Olariu, CornelMass transport deposits represent a significant component of modern and ancient deep-water depositional systems. However, geophysical data lack the resolution needed to identify meso-scale (meters to tens of meters) interactions between mass transport deposits and the underlying and overlying sediment. An exposed section of supra- detachment rift basin sedimentary deposits containing subaerial and subaqueous debris flows and coarse-grained turbidites provides an opportunity to examine both the variability related to debris flow emplacement and the unique type of debris flow known as a sturzstrom. The Fish Creek -- Vallecito Basin, part of the larger Salton Trough region of southern California, contains a late Miocene to Pliocene stratigraphic section that records the opening of the rift basin, marine flooding by the Gulf of California, and the arrival of the Colorado River. The lower Split Mountain Group debris flow (up to 50 m thick) was deposited subaerially and was extensive enough to partially cover the previously deposited alluvial fans. At this time it is likely that the subaerial basin floor had subsided below sea-level, much like the floor of the Salton Sea today. Breaching of the basin walls then led to a rapid marine incursion into an already deep basin, such that the lower debris flow was immediately and conformably overlain by gypsum, mudstones, and coarse- grained Lycium member turbidites of the Imperial Group. A second major debris flow (up to 45 m thick), this one a subaqueous flow, severely deformed, scoured, and truncated the underlying Lycium member turbidites, and profoundly impacted the routing and deposition of the overlying Wind Caves member turbidites that signal the arrival to the basin of the Colorado River. Each of the turbidite successions thus follows an event of catastrophic mass transport. This thesis describes and documents the variable meso-scale erosion of the underlying turbidite deposits by the younger debris flow, the impact of variable upper debris flow surface bathymetry on subsequent turbidite deposition and connectivity, and links these findings to observations made by other workers studying similar deep-water deposits in outcrop and in seismic-reflection data. Building on the efforts of previous workers, this thesis also describes the characteristics of the subaerial lower and subaqueous upper sturzstroms, investigates emplacement mechanism implications of micro-scale features, and provides the first paleogeographic reconstruction of the basin during the time of subaerial to marine transition and the arrival of the Colorado River into the region.Item Origin and Seismicity of the Gulf of California(Texas Tech University, 1972-05) Castro, Louis ReyesNot Available.