Browsing by Subject "Basin"
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Item Cenozoic sedimentation and exhumation of the foreland basin system in the Precordillera fold-thrust belt (31-32°S), southern central Andes, Argentina(2013-05) Levina, Mariya; Horton, Brian K., 1970-; Stockli, Daniel F; Ketcham, Richard AAndean retroarc shortening associated with flattening of the Pampean segment of the subducting Nazca plate has resulted in a thin-skinned, east-directed thrust system that partitioned and uplifted Cenozoic foreland basin fill in the Precordillera of west-central Argentina. The temporal and kinematic evolution of the Precordillera fold-thrust belt can be approached through detailed analyses of the clastic sedimentary deposits now preserved in intermontane regions between major thrust faults. In this project, we focus on the uppermost Oligocene–Miocene basin fill exposed in the axial and eastern Precordillera along the San Juan River (Quebrada Albarracín and Pachaco regions) and western flank of the frontal structure (Sierra Talacasto). The nonmarine successions exposed in these regions record hinterland construction of the Frontal Cordillera, regional arc volcanism, and initial exhumation of the Precordillera thrust sheets. Measured stratigraphic sections and lithofacies analyses of the preserved stratigraphic successions reveal initial development at ~24 Ma of an eolian depositional system influenced by regional volcanism and fluvial interactions, becoming a fully eolian system by 21-19 Ma. This system transitioned to a distributary fluvial system in which regions closer to the deformation front recorded sandy-gravelly braided stream sedimentation and regions farther east recorded more-distal floodplain-dominated deposition of thin-bedded mudstone and sandstone. The youngest sedimentary record is preserved in the Albarracin basin, a zone strongly influenced by explosive volcanism of nearby eruptive centers around 14 Ma, followed by a progradational alluvial-fan succession of pebbly, cross-stratified sandstone and thick, pebble to cobble conglomerate. Provenance changes recorded by detrital zircon U-Pb age populations suggest that initial deformation in the Frontal Cordillera coincided with the early Miocene transition from eolian to fluvial deposition in the adjacent foreland basin. The overall upward coarsening nature of the fluvial succession and increased presence of Paleozoic clasts reflect the eastward progression of thin-skinned deformation in the Precordillera and resultant structural partitioning of the synorogenic foreland successions. Using apatite (U-Th)/He thermochronometry we are able to further constrain the age of uplift-induced exhumation and cooling of several Precordillera thrust sheets to 12-9 Ma. This apparent pulse of exhumation is evident in all three sections, suggesting rapid, large-scale exhumation by synchronous thrusting above a single décollement linking major structures of the eastern Precordillera.Item Pore pressure within dipping reservoirs in overpressured basins(2013-08) Gao, Baiyuan; Flemings, Peter Barry, 1960-A systematic study of how mudstone permeability impacts reservoir pore pressure is important to understand the regional fluid field within sedimentary basins and the control of sediment properties on subsurface pressure. I develop a 2D static model to predict reservoir overpressure from information estimated from the bounding mudstones and structural relief. This model shows that close to a dipping reservoir, the mudstone permeability is high in the up-dip location and low in the down-dip location. This characteristic mudstone permeability variation causes the depth where reservoir pressure equals mudstone pressure (equal pressure depth) to be shallower than the mid-point of the reservoir structure. Based on the 2D static model, I constructed a nomogram to determine the equal pressure depth by considering both farfield mudstone vertical effective stress and reservoir structural relief. I find the equal pressure depth becomes shallower with decreasing vertical effective stress, increasing reservoir structural relief, and increasing mudstone compressibility. Pressure predicted by the static model agrees with pressure predicted by a more complete model that simulates the evolution of the basin and is supported by field observations in the Bullwinkle Basin (Green Canyon 65, Gulf of Mexico). This study can be applied to reduce drilling risk, analyze trap integrity, and facilitate safe and efficient exploration.Item Quantitative seismic geomorphology of a confined channel complex, southern Atwater fold belt, Gulf of Mexico, U.S.A.(2010-08) Morgan, Jessica Leanne; Wood, Lesli J.; Steel, Ronald; Fisher, William L.The structures along the Atwater Fold belt form important deep-water hydrocarbon traps in the northern Gulf of Mexico. The purpose of this study is to map and quantify the morphology, sedimentology and architecture of Plio-Pleistocene basin floor fan systems outboard of the Poseidon Minibasin, located along the Atwater deep-water fold belt (mid-Miocene to Pliocene), and apply that information to determine the temporal and spatial nature of the fill and its implications as a reservoir analog. The data set includes ~2200 km sq. of 3D seismic data, along with information from several wells. Wireline logs show the Tertiary age deposits outboard of the Sigsbee Escarpment to be several hundred feet thick, sharp-based, dominantly coarse-grained (sandy) but fining up cycles composed of sandy basin floor fans, mass transport complexes and leveed channels developed in a confined setting within deep-water “valleys.” The largest valley formed in five main stages: initiating from narrow channel incision, widening through lateral incision and sidewall slumping, straightening, and finally flooding and infilling. The valley system is ~20,000 feet across and ~ 1,400 feet deep, with what look like well-developed levees ranging from 700 to 1300 feet at their thickest point extending ~19000 feet away from the channel. This system is underlain by a ~700 foot thick mass transport complex and overlain by younger, low sinuosity leveed channel systems. Both of these systems appear to have been sourced by large submarine drainages, originating from a shelf edge sediment source system to feed the rugose slope with deep-water channel pathways uninhibited by salt wall inflation at the time of valley deposition. Major phases of salt thrusting along the southern edge of the Atwater were contemporaneous with the formation of these large, through-going valley system, which appear to be associated with the period of sheet thickening and development of monoclinal basinward dip related to rafted mini-basin docking. Well log signatures show evidence for armored clay drapes along the valley margins as well as a flattening of lateral accretion packages toward the distal end of the system. The flattening of these packages seems to signal proximity to the fan terminus, which would serve as an important indicator of spatial extent of plays in deep-water.Item Sedimentary, structural, and provenance record of the Cianzo basin, Puna plateau-Eastern Cordillera boundary, NW Argentina(2011-05) Siks, Benjamin Charles; Horton, Brian K., 1970-; Steel, Ronald J.; Milliken, Kitty L.The fault-bounded Cianzo basin represents a Cenozoic intermontane depocenter between the Puna plateau and Eastern Cordillera of the central Andean fold-thrust belt in northern Argentina. New characterizations of fold-thrust structure, nonmarine sedimentation, and sediment provenance for the shortening-induced Cianzo basin at 23°S help constrain the origin, interconnectedness, and subsequent uplift and exhumation of the basin, which may serve as an analogue for other intermontane hinterland basins in the Andes. Structural mapping of the Cianzo basin reveals SW and NE-plunging synclines within the >6000 m-thick, upsection coarsening Cenozoic clastic succession in the shared footwall of the N-striking, E-directed Cianzo thrust fault and transverse, NE-striking Hornocal fault. Growth stratal relationships within upper Miocene levels of the succession indicate syncontractional sedimentation directly adjacent to the Hornocal fault. Measured stratigraphic sections and clastic sedimentary lithofacies of Cenozoic basin-fill deposits show upsection changes from (1) a distal fluvial system recorded by vi fine-grained, paleosol-rich, heavily bioturbated sandstones and mudstones (Paleocene‒Eocene Santa Bárbara Subgroup, ~400 m), to (2) a braided fluvial system represented by cross-stratified sandstones and interbedded mudstones with 0.3 to 8 m upsection-fining sequences (Upper Eocene–Oligocene Casa Grande Formation, ~1400 m), to (3) a distributary fluvial system in the distal sectors of a distributary fluvial megafan represented by structureless sheetflood sandstones, stratified pebble conglomerates and sandstones, and interbedded overbank mudstones (Miocene Río Grande Formation, ~3300 m), to (4) a proximal alluvial fan system with thick conglomerates interbedded with thin discontinuous sandstone lenses (upper Miocene Pisungo Formation, ~1600 m). New 40Ar/39Ar geochronological results for five interbedded volcanic tuffs indicate distributary fluvial deposition of the uppermost Río Grande Formation from 16.31 ± 0.6 Ma to 9.69 ± 0.05 Ma. Sandstone petrographic results show distinct upsection trends in lithic and feldspar content in the Casa Grande, Río Grande, and Pisungo formations, potentially distinguishing western magmatic arc (Western Cordillera) sediment sources from evolving eastern thrust-belt sources (Puna‒Eastern Cordillera). In addition to growth stratal relationships and 40Ar/39Ar constraints, conglomerate clast compositions reflect distinct lithologic differences, constraining the activation of the Cianzo thrust and coeval movement on the reactivated Hornocal fault. Finally, U-Pb geochronological analyses of sandstone detrital zircon populations in conjunction with paleocurrent data and depositional facies patterns help distinguish localized sources from more distal sources west of the basin, revealing a systematic eastward advance of Eocene to Miocene fold-thrust deformation in the central Andes of northern Argentina.