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.

This study maps the facies architecture and geometry of stratigraphic surfaces within the tide-influenced upper Sego Sandstone exposed in the Book Cliffs between Crescent Junction and Thompson Springs, Utah. A bedding diagram was constructed by correlating 32 measured stratigraphic logs across this 8.5 kilometer strike-oblique outcrop to interpret depositional environments and the sequence stratigraphic setting of this tidally-influenced sandstone. Five facies associations are defined: marine shale, lower shoreface, tidally-influenced bedsets, heterolithic tidal bedsets, and tidal flat deposits. Vertical facies trends define two sandy intervals separated by a marine shale, that are interpreted to record episodic progradation of deltaic shorelines. Erosion surfaces at the base of these intervals are interrupted to record tidal scouring of the sea floor during falling stage regression. Sandstone-bodies within these intervals shingle westward recording delta lobes that thinned and became more heterolithic. Although sandstone intervals are interpreted to record progradation, internal cross stratification is dominantly tidal-flood oriented. This is interpreted to record preferential preservation of bedload transported by flood tidal currents onshore, even though net sediment was directed offshore in a suspended ebb-oriented hypopycnal plume and as fluid mud during uncommon river floods. Deposits above high-relief erosion surfaces observed to cut down into the upper Sego Sandstone do not meet the criteria for incised valley fills. These surfaces are interpreted to record tidal current enlargement of distributary channels after abandonment. Such incisions thus do not necessarily record changes in sea level.

Thesis (M.S.)--Ohio University, August, 2009. / Title from PDF t.p. Includes bibliographical references.

Differential loading induced deformation of a mobile substrate (e.g., salt tectonics) is an important process for the development of accommodation space and stratigraphic architectures in intra-slope minibasins. Numerous studies of minibasin systems have focused on either the tectonic processes involved in salt body deformation or the stratigraphic interpretation of the overburden sediment deposits. This study, however, focuses on coevolution of depositional and tectonic processes and provides a new insight of the linked evolution into the stratigraphic patterns. Using a silicone polymer to simulate a viscous mobile substrate, a series of 2D experiments were conducted to explore the effects of variation in 1) sedimentation rate, 2) depositional style (intermittent sediment supply), and 3) the thickness of the deformable salt substrate on subsidence patterns and minibasin evolution. Experiments results have shown that larger initial thickness of salt substrate as well as lower sedimentation rate caused greater amounts of subsidence for a given amount of deposit. Furthermore, increase in subsidence rate was observed as sedimentation continued, while decrease in subsidence rate occurred once sedimentation ceased. Due to the linked depositional and tectonic processes, higher sediment supply resulted in relatively slower subsidence and more actively widening minibasins. Lower sediment supply was observed to have the reverse effect, resulting in higher relative subsidence and a narrow basin width. A numerical model that captures viscous flow under the deposit is also presented here. The model for minibasin formation showed the effects of interaction of the two processes (deposition and tectonics) on the development of minibasin strata in the experiments. Experimental and modeled findings have resulted in a new model of minibasin development that incorporates the effects of sedimentation rates on subsidence patterns into basin evolution. / text

The Lagonegro Zone comprises three structural units which outcrop within the pile of decollement nappes forming the southern Italian Appenines. Stratigraphic, structural and sedimentological evidence suggests that the zone represents the relics of a Mesozoic basin that developed amidst the carbonate platforms bordering the southern margin of Tethys. Mapping has confirmed that the Lagonegro I, Lagonegro II and Monte Foraporta Units are separated by thrusts and are stacked in ascending order. Middle Triassic fine-grained terrigenous clastic sediments and neritic limestone olistoliths of Lagonegro Unit II record the disintegration of a young carbonate platform under the influence of extensional tectonics. Deposition and redeposition of hemi-pelagic lime-mud washed from the adjacent shallow-water platforms during the Late Triassic is manifested in both Lagonegro units by the cherty limestones of the Sirino Formation; a gradual transition from calcareous to siliceous deposition at the top of the formation reflects the subsidence of the basin-floor beneath the Calcite Compensation Depth. Contrasting patterns of siliceous and calciclastic sedimentation developed during the Jurassic, probably imposed by renewed extensional tectonics; coeval calciclastic deposition in a small, and at times anoxic marginal basin is recorded in the Monte Foraporta Unit. Dolomitisation of basinal carbonate rocks took place during the Jurassic due to mixing of saline pore-fluids with meteoric water recharged from the adjacent carbonate platforms. Deposition of terrigenous shales below the Calcite Compensation Depth occurred during the Lower Cretaceous, but calcareous sedimentation was resumed in the Late Cretaceous and Palaeogene. The progressive deepening of the basin documented by these facies transitions is attributed to regional subsidence, caused by crustal extension and attenuation, and relative accretion of the surrounding platforms; comparable basal stratigraphies in several ophiolitic zones of the Alpine-Mediterranean region suggest that many Tethyan 'oceanic' basins may have initially developed in a similar manner.

This study defines depositional environments and constructs the sequence stratigraphic framework of the lower Miocene Oakville Formation and the basal part of the middle Miocene Lagarto Formation in the Carancahua Bay area. The Early Miocene of the northwestern Gulf of Mexico represents a tectonically stable period with a high sediment influx. The analysis is based on a data set composed of 45 well logs and 200 mile2 area 3D seismic volume. The study interval was divided into five depositional sequences 1-5 that encompass 0.6-2.5 My. LST, TST, and HST systems tracts were recognized by stacking patterns and bounding surfaces. Sequence thickness increases from sequence 1 to 3 and displays reverse thickness trends from sequence 3 to 5, implying changes in accommodation space relative to sediment supply, beginning with high rates of accommodation and evolving into low accommodation rates relative. Besides type-1 depositional sequence which forms during relative sea-level fall below the shoreline break, regressive units of T-R sequence model were also defined and delineated. The interval contains four regressive units, R-Unit1-4. The R-Unit net sandstone maps exhibit the same characteristic of a dip-oriented source of delta-plain origin and a delta-front depocenter basinward. Integration of well log patterns, sandstone dispersal trends from net sandstone maps and seismic stratal slices led to interpretation of depositional environments in each sequence. LST deposits are represented mainly by incised-valley fill facies. TSTs are composed predominantly of retrogradational barrier/tidal-inlet facies, whereas other TSTs contain lagoonal and reworked deltaic systems. HST1 is composed mainly of fluvial-dominated deltaic systems, whereas deltaic systems in other HSTs exhibit wave-influenced deltaic and strandplain depositional systems. The integrated methodology reveals depositional facies variations in contrast to previous work that interpreted these deposits as shorezone systems. During LSTs coarse-grained sediments bypassed shelf through incised valley systems to a downdip depocenter. More sandy sediments were stored on shelf as deltaic and strandplain deposits during HSTs. In contrast to the others, destructive process occurred in TSTs and reworked sandy sediments, for example from delta fronts to barrier bar and lagoonal facies. Submarine fans form by sediments transported through incised-valley systems and delta fronts are commonly good reservoirs. Hence, presence of such depositional facies in the study area might be genetically linked to exploration targets. / text

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The Tibetan plateau is arguably the most important geological feature on Earth, yet its formation and evolution are poorly understood. This investigation utilizes Cretaceous sedimentary strata exposed in the Lhasa terrane of southern Tibet in order to constrain the paleogeography and tectonic setting of the region prior to the Indo-Asian collision. Lower Cretaceous strata consist of clastic sedimentary units that were deposited in shallow marine and fluvial environments. In northern Lhasa these sediments were deposited in a peripheral foreland basin that formed in response to the Lhasa-Qiangtang collision. The lower Cretaceous sediments in southern Lhasa are quartzose and were derived from cover strata exposed by local uplifts. A marine limestone of Aptian-Albian age overlies the lower Cretaceous clastic strata and was deposited in a shallow continental seaway. The paleogeography of the Lhasa terrane during deposition of the carbonate units was dominated by the effects of the Lhasa-Qiangtang collision, although other conditions, such as a high eustatic sea-level, influenced sedimentation as well. The Upper Cretaceous Takena Formation is composed of a basal member of marine limestone and an overlying member of fluvial red beds. The arkosic strata of the Takena Formation were deposited in a retro-arc foreland basin that formed to the north of the Gangdese magmatic arc. Collectively, the Cretaceous sedimentary strata indicate significant tectonic activity occurred in southern Tibet prior to the Indo-Asian collision. Moreover, the data suggest the crust of southern Tibet was thickened and possibly at high elevations before the Cenozoic.

The Campbellton Formation, ~1 km thick, has long been recognized for early plants, arthropods, and fishes. The sedimentology of two basins is described with six facies associations to provide a framework for the fossil assemblages. The western basin contains aquatic fauna and coastal flora within a basal rhyolite breccia and coastal deltaic strata, and a braided river facies association is also present. Lower eastern basin strata primarily comprise lacustrine facies, where a thick marginal association deposited by sediment-laden underflows contains a lake-side plant assemblage. Other lacustrine associations include a fine-grained association in areas with restricted circulation, and a near-shore association. Upwards, a plant-rich fluvial landscape had wide sandstone and conglomerate channels and high-diversity wetlands containing terrestrial arthropods. A proximal alluvial facies association with hyperconcentrated flows contains plants and Prototaxites, possibly from adjoining uplands. All plants groups were well-established throughout the formation, with no apparent landscape partitioning between groups.

High Arctic meromictic lakes are frequently used to generate detailed records of past environmental variability within their sedimentary profiles. However, without detailed analyses of sedimentation influences over time, their paleoclimate records cannot be accurately interpreted. This thesis presents a comprehensive examination of the sedimentology and paleoenvironmental records of meromictic Lake A, Ellesmere Island (83°00’N, 75°30’W), including detailed analysis of the sedimentary history, development and evaluation of several paleoclimate records. The sedimentary record was primarily composed of clastic material but varying inputs of authigenic components from biological and chemical processes in the water column resulted in a complex history of lake sedimentation. Under chemically stratified conditions during the past millennium, annual laminae (varves) formed and were used to develop a sedimentary chronology. Sedimentary pellets were most likely formed by ice-rafting processes and were deposited during high melt years in this perennially ice-covered lake. The pellet frequency record indicated that the twentieth century contained the most frequent reduced ice cover summers during the past millennium, although the 1500s and 1600s were also inferred warm periods. Comparison with instrumental climate data indicated that varve thickness was primarily related to late summer and autumn snowfall in the previous year, which highlighted the importance of snow availability in spring rather than melt energy in sediment transfer to the lake in this non-glacial catchment. The varve thickness and grain size records suggested increased flow competency and autumn snowfall particularly during the late-1000s to early-1100s and first half of the 1900s. Paleoenvironmental records from Lake A corresponded well with many regional proxy records and provided a long-term framework within which to examine observed environmental change along the northern Ellesmere Island coast during the past century. Finally, these analyses would not have been possible without obtaining high quality sediment cores. This research also investigated the effectiveness of a gel seal method for preserving the fragile sediment-water interface during transport and its results could be useful for other sediment core studies. / Thesis (Ph.D, Geography) -- Queen's University, 2008-05-08 13:34:14.044