The Arumbera Sandstone consists of mappable informal units which are repeated in a vertical, cyclic succession. Sandstones of fluvial origin form resistant strike ridges separated by strike valleys, which consist of recessive sandstones and mudrocks of marine origin. Lithofacies 1a, 2b, and 3a are probably of marine origin in intertidal environments. Trace fossil assemblages in lithofacies 3a suggest Skolithos and Cruziana inchnofacies were present. Lithofacies 1e, 2a, 2c, 3b, and 4a are probably of fluvial origin, as the result of coalescing braided stream deposits. The Arumbera Sandstone probably was deposited in a deltaic environment characterized by low wave energy, a micro tidal range, and high input of sand-sized sediment br braided streams. In the western MacDonnell Ranges, the Arumbera overlies the Julie or Pertatataka formations along a sharp but conformable contact. The present upper contact is a low-angle regional unconformity which contains paleotopographic elements that resemble pediments, stripped structural plains, and steep erosional scarps. These paleotopographic surfaces are overlain from east to west by the Chandler, hugh River, and Cleland formations in an onlap relationship. The Arumbera Sandstone is considered part of a molasse sequence associated with the Late Proterozoic and Early Cambrian Petermann Ranges orogeny, which occurred along the present southern and southwestern margin of the Amadeus Basin. The uplifted Petermann Ranges shed detritus from metamorphic, sedimentary, and minor amounts of plutonic rocks. Paleocurrents suggest most terrigenous material was derived from the southwestern margin of the basin. The composition of detrital grains and lack of weathering features in labile detrital grains suggest a hot, semiarid to arid climate in the source area and in the basin of deposition. Sandstone samples examined petrographically primarily are subphyllarenites, subarkoses, arkoses, feldspathic litharenites, and lithic arkoses. The inferred paragenetic sequence is: Eogenetic: (1) mechanical compaction, (2) "dust rims" of hematite, illite, and chlorite, and (3) hematite cement; Mesogenetic: (4) syntaxial feldspar overgrowths, (5) syntaxial quartz overgrowths, (6) hematite cement, (7) carbonate cement, (8) kaolinite replacement, (9) formation of secondary porosity; Telogenetic: (10) chert cement and (11) gibbsite or hematite cement.

Within the thesis study area Spencer Formation arkosic/arkosic lithic sandstone lithofacies of Narizian age crop out in a sinuous north-northwesterly band from the Corvallis area into the Henry Hagg Lake vicinity ten kilometers southwest of Forest Grove, Oregon.

Seven distinctly different museum-quality concretionary morphotypes of elongate, spheroidal, banded, botryoidal, columnar, rosette, and speleothem in regolith at two small sites at the base of the Meski Plateau near Erfoud, Morocco are described. Although most are isolated hand samples, the largest concretions are meter-sized blocks. Not one sample resembles any surrounding outcrop or bedrock. The barite rosettes formed first via periodic mixing of Ba2+/SO42- saturated solutions. They provided nuclei for cyclical precipitation-based concentric concretion development. The speleothem formed via precipitation from a carbonate-saturated solution in a large void within porous sandstone. The sand concretions formed when calcite precipitated around grains in unconsolidated quartz sands with cyclic fluctuation of Ca2+/CO32- saturated ground water. Petrographic analyses, stable isotope data, sample morphology, coupled with light and scanning electron microscopy indicate that microbial processes induced the periodic cement precipitation that produced the unique concretions.

No description available.

No description available.

Upper Triassic strata that lie between the Chinle Formation and Nugget Sandstone along the south flank of the Uinta Mountains in northeastern Utah are distinctive. In the past, these rocks have been lumped together with the overlying or underlying units. These strata are equivalent to the Bell Springs Member of the Nugget Sandstone as defined in Wyoming and perhaps to the Rock Point Formation of the Chinle Formation near the Four Corners region. In this study, these rocks will be called the Bell Springs Formation following the usage of Lucas (1993) in Wyoming. The unit is regionally mappable in northeastern Utah, and is the sedimentologic transition from the fluvial-lacustrine environment of the Chinle Formation to the eolian depositional environment of the Nugget Sandstone. The Bell Springs Formation is comprised of interbedded fine- to medium-grained sandstone and siltstone, as well as planar laminated mudstone. The unit varies from planar laminated sandstone with abundant ripple marks, to cross-bedded sandstone that contains scoured channels filled with mudstone or sandstone. The mudstone beds are commonly mottled and contain desiccation cracks while both the mudstone and sandstone beds have rip-up clasts, occasional bioturbation, and small salt crystal casts. The thinly bedded mudstone and siltstone beds are purple to red to brown, and the sandstone beds vary in color from red to brown to orange or tan with green and gray mottling. The ripple structures with mud drapes indicate fluctuating deposition in low energy water. The presence of desiccation cracks, plant root traces, small eolian sand dunes, gypsum casts, crinkly algal mat beds, and bioturbation indicate intermittent subaerial exposure. Fluvial deposits by meandering streams, including point bar, levee, and splay deposits comprise a large part of this formation. Rocks of the Bell Springs Formation have previously been interpreted as either tidal flat or fluvial/lacustrine deposits. A tidal flat environment certainly may produce some of the features found in these deposits, such as, alternating erosion and deposition of interfingering channels and scours with rip-up clasts, ripples, flaser bedding, desiccation cracks, and bioturbation; however, these rocks lack some of the most important characteristics of tidal flat deposits such as herringbone-cross-stratification, general fining upward successions, and regionally associated sediments that would typically be found in shallow marine environments. We conclude that the sedimentary characteristics and regional setting of these rocks fit best with a fluvial environment interpreted as a meandering system being deposited on a broad floodplain in an arid to semi-arid climate. This depositional environment existed between the expanding Nugget Sandstone erg and the shrinking Chinle Formation as desertification increased during the Late Triassic and Early Jurassic in what is now the western United States. This study not only helps solidify the understanding of the depositional history of these strata, it also clarifies the nomenclature of these formations for future mapping and research.

Sedimentological analyses, including detailed facies characterization and lateral profiling, demonstrate deposition in a bedload-dominated fluvial system for the quartzose sandstones of Lee Formation. Internal (architectural) elements of the sandstones consist primarily of truncated channel-fIll sequences. Individual channel elements, up to 20 meters thick, contain a complex hierarchy of bedform deposits. The principal internal component of channels were downstream-accreting (mid-channel?) macroforms; channel elements frequently contain deposits of more than one macroform. Reconstruction of the macroforms reveals accretion primarily by superposed bedforms that migrated down a low-angle front. Steeper, giant foresets, transitional along flow with the low-angle facies, indicate that the macroform episodically developed a steep slipface. Uppermost channels within the Rockcastle Member contain macroform elements with components of lateral accretion, interpreted as deposits of alternate bank-attached macroforms. Also recognized within channel-fill deposits are minor-channel, sandy-bedform, gravity-flow (attributed to bank slumping), and channel-bottom elements. The latter element is contained within a facies sequence that suggests rising- to flood- to waning-stage deposition. In general, deposition was probably during relatively high stage; little evidence of low-stage flow was recognized. Subordinate fine-grained facies are interpreted as levee and overbank deposits. Strongly unimodal paleocurrents, lack of facies that suggest low-stage reworking and paucity of lateral-accretion features indicate deposition in a single-channel, low-sinuousity, system (i.e., a low braiding index). Fluvial architecture similar to that found in the Lee Formation has been previously explained by deposition in multi-channel, braided-river systems. However, the internal architecture of sandstone members is also consistent with a single-channel origin. Individual channels were temporarily confined, during which time the passage of several macroforms aggraded the channel. Position of the channel in the alluvial plain was largely controlled by avulsion of the river from fully aggraded channel belts to other areas of the plain. Calculations reveal that avulsion of a single-channel system across a wide alluvial plain is a plausible mechanism for building the sheet-like sandstone bodies of the Lee Formation. Spatial arrangement of individual sandstone members of the Lee Formation was probably controlled by tectonic processes. Episodic thrust-loading in the orogenic belt to the east and subsequent flexure of the crust in the foreland basin caused a step-wise progression of the river system towards the west. Petrographic, sedimentologic and stratigraphic data indicate that source area and climate functioned as the primary controls on the mature composition of sandstones in the Lee Formation. Source areas were composed primarily of quartz-rich sedimentary rocks and were located chiefly to the northeast/north. A east/southeast source area supplied subordinate and low-grade metamorphic rock fragments. Intense weathering, associated with humid tropical climates, acted upon the detritus throughout the sedimentation cycle. Less important controls on composition were tectonics and transport/depositional processes that extended exposure of the sediments to the severe climatic conditions. Quartzose sandstones of the Lee Formation reflect lower rates of tectonic subsidence and greater recycling of sand-sized grains during transportation and temporary deposition on the alluvial plain, relative to lithic time equivalents to the east. / Ph. D.

Lower Pennsylvanian siliciclastic sedimentary rocks of the central Appalachian Basin consist predominantly of nonmarine, coal-bearing facies that developed within a fluvio-estuarine, trunk-tributary drainage system in a foreland-basin setting. Sheet-like, sandstone-mudstone bodies (up to 100 km wide and 70 m thick) developed in an axial trunk drainage system, whereas channel-like, sandstone-mudstone bodies (up to several km wide and 30 m thick) developed in tributaries oriented transverse to the thrust front. The origin of these strata has been debated largely because the paleogeomorphology and facies architecture of the New River Formation (NRF) are poorly understood. A sequence stratigraphic framework for the NRF, based on a combination of outcrop mapping and subsurface well-log analysis, reveals: 1) regionally significant erosional surfaces along the bases of sheet-like and channel-like sandstone bodies (sequence-boundaries), 2) fluvial- to estuarine-facies transitions (marine flooding surfaces), 3) erosionally based, framework-supported, quartz-pebble conglomerates (ravinement beds), and 4) regionally traceable, coarsening-upward intervals of strata (highstand deposits above maximum flooding surfaces). Using these criteria, both 3rd- and 4th-order sequences have been identified. An idealized 4th-order sequence consists of deeply incised, fluvial channel sandstone separated from overlying tidally modified estuarine sandstone and mudrock by a ravinement bed, and capped by coarsening-upward bayhead delta facies. The relative thickness of fluvial versus estuarine facies within a fourth-order sequence reflects a balance between accommodation and sediment supply within a 3rd-order relative sea level cycle. Lowermost 4th-order sequences are dominated by fluvial facies, whereas the uppermost sequences are dominated by estuarine facies. Therefore, 3rd-order sequence boundaries are interpreted to lie at the bases of the lowermost, fluvial-dominated fourth-order sequences. Coarsening-upward intervals that record the maximum landward extent of marine conditions are interpreted as highstand deposits of the composite third order sequence. Thus, the NRF consists of thick, superimposed fluvial sandstone of the lowstand systems tracts and anomalously thin transgressive and highstand systems tracts. Asymmetrical subsidence within the foreland basin resulted in westward amalgamation of multiple, 4th-order, fluvial valley-fill successions and sequence boundaries. The Early Pennsylvanian time period was characterized by global icehouse conditions and the tectonic assembly of Pangea. These events affected the geometry of the overall stratigraphic package, which can be attributed to high-magnitude, high-frequency, glacioeustatic sea-level fluctuations superimposed on asymmetric tectonic subsidence. / Master of Science

Quaternary magnetic studies have provided the conceptual framework to bridge magnetic studies into ancient systems. In cases where environmental materials have been subjected to diagenetic alteration two questions come to mind: 1) What part of the magnetic signal is preserved in the rocks; and 2) can the preserved signal be used to infer/identify magnetic patterns that are characteristic of the depositional, post-depositional, and/or diagenetic environment. Analyses of multi-parameter magnetic experiments conducted on upper Mississippian and lower Pennsylvanian continental successions reveal that distinct depositional, pedogenic, and diagenetic magnetic patterns can be separated and identified. Evidence for a primary depositional signal in several of the upper Mississippian lithofacies is identified by a detrital remanence component attributed to source-area-derived magnetite/titanomagnetite. Red and gray vertisols preserve a Mississippian pedogenic signal characterized by magnetic enrichment, depletion, and amalgamation patterns that are associated with the removal and transport of Fe-rich clays as well as vertical mixing by shrink-swell mechanisms. These well-developed vertisols are interpreted to reflect significant hiatuses in sedimentation associated with prolonged exposure on interfluve/floodplain surfaces that may correlative with incised valleys (lowstand surface of erosion). Similarly, in lower Pennsylvanian quartz arenite facies, early siderite cementation zones as well as conglomerate lags with distinctive magnetic characteristics are thought to reflect periods of prolonged exposure and to define unconformities within compound valley fills. / Master of Science

<p> Four measured sections of the Whirlpool Sandstone were prepared from outcrops in the Niagara Gorge and Hamilton areas. Sedimentary structures and constituents present in the lower two-thirds of the unit are consistent with the sandy braided fluvial depositional model. proposed by Salas [1983]. The upper one-third of the unit has been deposited in a near shore, shallow marine environment. All samples have been classified as Quartzarenites, or Sublitharenites after Folk [1974] and the source of the Whirlpool lies to the southeast in primarily pre-existing sediments, with some input from low grade metamorphic and hydrothermally veined terrains. </p> <p> Cathodoluminescent microscopy has proven to be a safe, relatively inexpensive, easy to use method, that offers a great deal of new information. The technique's only drawback is the gradual destruction of thin sections by the electron beam. The CL study demonstrated that pressure solution was not the source of the massive, pore occluding, mesodiagenetic quartz cement. Since very low diagenetic temperatures have been calculated for the Whirlpool in the study area [360C]; the local generation of silica would be impossible. Instead, it has been suggested that silica was carried in by saturated pore fluids that had migrated up-dip from source areas deep within the depositional basin to the southeast. Similarly, pyrite was precipitated as H2S bearing fluids migrated through the unit. These reducing fluids also produced the reduced zone at the top of the Queenston Formation. The H2S was produced during the maturation of hydrocarbons. Calcite cement is more abundant in the upper marine units of the Whirlpool. This suggests that the source of the calcite was local detrital carbonate in the upper marine units. Quartz cementation ceased when the porosity had been reduced sufficiently to inhibit the passage of the migrating pore fluids. Thus, the calcite cement precipitated from static pore fluids. The local detrital carbonate was dissolved by the acidic fluids that carried in the silica. This Ca+2 rich fluid was prevented from mixing with the bulk porewater and calcite precipitation occurred due to an increase in C02 by the decay of organic detritus in the upper marine units. The major proportion of secondary porosity was formed during mesodiagenesis by the dissolution of calcite. The pore fluids became undersaturated with respect to calcite when local intershale water was released into the porewater. The formation of dolomite cement was in response to a decrease in the amount of available iron relative to magnesium due to the precipitation of ferroan calcite. The zonation of the dolomite reflects rapid changes in porewater composition. Four morphologies of illite have been identified: two represent direct precipitation from alkaline, K+ rich solution; one may be detrital in origin, or it could represent illite that has been mechanically infiltrated down into the sand after deposition; and the fourth is a mixed layer assemblage that has been formed by the replacement of earlier clays by illite. The oil and gas found in the Whirlpool Sandstone in the Lake Erie area have probably migrated up-dip from source areas deep within the depositional basin to the southeast. </p> / Thesis / Bachelor of Science (BSc)