Dominant Geological Processes Research Articles

Evaluating the depositional environment, lithofacies variation, and diagenetic processes of the Wolfcamp B and lower Spraberry intervals in the Midland Basin: Implications for reservoir quality and distribution

Detailed facies characterization in the Wolfcamp B and lower Spraberry intervals of two drill cores in the Midland Basin has yielded five main lithofacies with distinctive physical, chemical, and biologic attributes. The main attributes for facies identification include lithology and/or mineralogy, texture and/or fabric, porosity, hydrogen index, and total organic carbon content. The methodologies are focused on detailed core description, thin-section petrography, quantitative x-ray diffraction, and field emission scanning electron microscopy (SEM). Porosity data are primarily based on Gas Research Institute (Core Laboratories) measurements and field emission SEM assessment. Moreover, the depositional and diagenetic controls on facies development are addressed to assess the dominant geological processes that govern reservoir quality and distribution. A model of five end-member facies is proposed to characterize source and reservoir elements through delineating facies tracts. The five end-member facies are as follows: facies 1: silty mudstone, optimal source, and optimal to fair reservoir; facies 2: muddy siltstone (optimal source and optimal reservoir); facies 3: silty calcareous mudstone (good source and good reservoir); facies 4: bioclastic wackestone–floatstone (fair source and fair reservoir); and facies 5: packstone–grainstone (poor source and poor to excellent reservoir). The proposed facies scheme aims to provide a more comprehensive approach to capture the high vertical and lateral variability in this mixed carbonate and fine-grained clastic succession. Through this detailed textural, compositional, sedimentologic, and diagenetic approach, this facies model can be used to better understand reservoir quality and distribution throughout the Midland Basin.

Geologic drivers of late ordovician faunal change in laurentia: investigating links between tectonics, speciation, and biotic invasions.

Geologic process, including tectonics and global climate change, profoundly impact the evolution of life because they have the propensity to facilitate episodes of biogeographic differentiation and influence patterns of speciation. We investigate causal links between a dramatic faunal turnover and two dominant geologic processes operating within Laurentia during the Late Ordovician: the Taconian Orogeny and GICE related global cooling. We utilize a novel approach for elucidating the relationship between biotic and geologic changes using a time-stratigraphic, species-level evolutionary framework for articulated brachiopods from North America. Phylogenetic biogeographic analyses indicate a fundamental shift in speciation mode—from a vicariance to dispersal dominated macroevolutionary regime—across the boundary between the Sandbian to Katian Stages. This boundary also corresponds to the onset of renewed intensification of tectonic activity and mountain building, the development of an upwelling zone that introduced cool, nutrient-rich waters into the epieric seas of eastern Laurentia, and the GICE isotopic excursion. The synchronicity of these dramatic geologic, oceanographic, and macroevolutionary changes supports the influence of geologic events on biological evolution. Together, the renewed tectonic activity and oceanographic changes facilitated fundamental changes in habitat structure in eastern North America that reduced opportunities for isolation and vicariance. They also facilitated regional biotic dispersal of taxa that led to the subsequent establishment of extrabasinal (=invasive) species and may have led to a suppression of speciation within Laurentian faunas. Phylogenetic biogeographic analysis further indicates that the Richmondian Invasion was a multidirectional regional invasion event that involved taxa immigrating into the Cincinnati region from basins located near the continental margins and within the continental interior.

Fractal properties of isolines at varying altitude revealing different dominant geological processes on Earth

Geometrical properties of landscapes result from the geological processes that have acted through time. The quantitative analysis of natural relief represents an objective form of aiding in the visual interpretation of landscapes, as studies on coastlines, river networks, and global topography, have shown. Still, an open question is whether a clear relationship between the quantitative properties of landscapes and the dominant geomorphologic processes that originate them can be established. In this contribution, we show that the geometry of topographic isolines is an appropriate observable to help disentangle such a relationship. A fractal analysis of terrestrial isolines yields a clear identification of trenches and abyssal plains, differentiates oceanic ridges from continental slopes and platforms, localizes coastlines and river systems, and isolates areas at high elevation (or latitude) subjected to the erosive action of ice. The study of the geometrical properties of the lunar landscape supports the existence of a correspondence between principal geomorphic processes and landforms. Our analysis can be easily applied to other planetary bodies.

The Spirit Rover's Athena Science Investigation at Gusev Crater, Mars

The Mars Exploration Rover Spirit and its Athena science payload have been used to investigate a landing site in Gusev crater. Gusev is hypothesized to be the site of a former lake, but no clear evidence for lacustrine sedimentation has been found to date. Instead, the dominant lithology is basalt, and the dominant geologic processes are impact events and eolian transport. Many rocks exhibit coatings and other characteristics that may be evidence for minor aqueous alteration. Any lacustrine sediments that may exist at this location within Gusev apparently have been buried by lavas that have undergone subsequent impact disruption.

The Spirit Rover's Athena science investigation at Gusev Crater, Mars.

The Mars Exploration Rover Spirit and its Athena science payload have been used to investigate a landing site in Gusev crater. Gusev is hypothesized to be the site of a former lake, but no clear evidence for lacustrine sedimentation has been found to date. Instead, the dominant lithology is basalt, and the dominant geologic processes are impact events and eolian transport. Many rocks exhibit coatings and other characteristics that may be evidence for minor aqueous alteration. Any lacustrine sediments that may exist at this location within Gusev apparently have been buried by lavas that have undergone subsequent impact disruption.

GEOLOGICAL CONTROLS ON SONIC VELOCITY IN THE CENOZOIC CARBONATES OF THE NORTHERN CARNARVON BASIN, NORTH WEST SHELF, WESTERN AUSTRALIA

The Cenozoic carbonates of the Bounty-Talisman region can be divided into five major facies. From oldest to youngest, these are: Paleocene to Eocene basinal facies, Oligocene to Miocene slope-canyon facies, Oligocene to Miocene shelf facies, Oligocene to Miocene near-shore facies, and Pliocene-Quaternary shelf facies. This represents a shallowing-upwards cycle up to the late Miocene, followed by a significant transgression and a return to more open marine conditions in the Pliocene- Quaternary. The dominant geological processes controlling sonic velocity in the Cenozoic carbonates are physical compaction, burial calcite cementation, dolomitisation, and anhydrite/gypsum cementation. In the more open marine facies of the Cenozoic carbonates, compaction and burial calcite cementation have been the dominant geological processes that have controlled sonic velocity. Large-scale carbonate content variations associated with submarine canyon-fill sediments have also produced lateral sonic velocity variations. Dolomitisation and anhydrite cementation have produced localised high velocity zones within the near-shore facies of the carbonates.

How Volcanoes Work

Volcanism and associated plutonism have been dominant geologic processes from the earliest beginnings of our planet. Indeed, more than 80% of the Earth's surface is now, or originally was, of magmatic origin, and the distribution of volcanoes, past and present, reflects mantle and crustal dynamics within a context of plate tectonics. In recent decades, increasing attention has been paid to the study of the role of volcanism in global climate change. It is hardly surprising that since the flowering of the natural sciences in the 19th century, the question of how volcanoes work has been and remains one of the most fascinating and fundamental questions to challenge Earth scientists.

Cheniers of Southwestern Louisiana

SEVERAL long, narrow, sandy ridges run roughly parallel to the coast of southwestern Louisiana. Rising slightly above surrounding marshes, lakes, and watercourses, all essentially at sea level, these low ridges form the most conspicuous topographic features of the region. Sharply localized, well drained, and fertile, they support naturally a luxuriant vegetational cover in which large evergreen oaks form so striking a part that, quite deservedly, the ridges have been called cheniers' by their Creole inhabitants. Many of the cheniers have been cleared. Cotton fields cover large parts of the highest and most accessible; those lower and more distant form bases for grazing, trapping, hunting, and fishing. Where they are served by roads or navigable waters, the population is relatively dense and prosperous. It is not the purpose of this paper, however, to consider cheniers in their cultural aspects. We are here concerned with their origin, a history involving several of the dominant geologic processes affecting the Gulf Coast during Quaternary time. The entire Gulf Coast of the United States is a splendid exhibit of the consequences of active submergence. The mouth of practically every river is estuarine. From the Caloosahatchee, of southern Florida, to Baffins Bay, of southern Texas, the coast is marked by a dozen or more large bays and a much larger number of less conspicuous drowned river mouths. The subsidence causing this condition is so rapid that in the entire distance only two rivers, the Mississippi and the Appalachicola, have been able to build deltas protruding into the Gulf. The Mississippi has done so because of its enormous size and load, the Appalachicola because it drains an anticlinal region undergoing active uplift. The absence of deltas along the Gulf Coast might not be particularly significant were the streams clear and their burdens small, but the opposite is the case. Any comparatively short period of crustal stability would witness not only the rapid filling of their estuarine mouths but the growth of deltas into the Gulf as well.2 The effects of submergence extend well inland. Practically every stream immediately inland from the coastal marsh zone flows down