Rex Cole - Academia.edu (original) (raw)

Papers by Rex Cole

A detailed geochemical analysis (calibrated x-ray fluorescence) of the Late Cretaceous Mancos Sha... more A detailed geochemical analysis (calibrated x-ray fluorescence) of the Late Cretaceous Mancos Shale was conducted on 176 cuttings samples (total interval = 4,730 ft.) collected from the Fees Federal 2-6-8-101 well (API 05-045-07432). Major elements (>2% on an oxide basis)evaluated included Si, Al, Ca, Mg, Fe, and K and minor elements (<2% on an oxide basis) examined include Ti, Mn, Na, S, and P. Trace elements (ppm concentration) investigated include Se, Ni, Co, V, Cr, and Mo. The samples were also analyzed by calcimeter for total carbonate and by ignition loss at 400 °C for total organic carbon and water. Numerous vertical trends and discontinuities are present in the data. Some significant observations are: silicon (as SiO2 is about 65% in the lower Mancos (Mowry through Monument Valley members), drops to 40.6% at the base of the Niobrara (Ft. Hays), then generally increases to about 75% through the Niobrara, Prairie Canyon, Sharon Springs, Castlegate, and Buck Tongue member...

Western Slope (Western Colorado)

Every fall since 1950, the New Mexico Geological Society (NMGS) has held an annual Fall Field Con... more Every fall since 1950, the New Mexico Geological Society (NMGS) has held an annual Fall Field Conference that explores some region of New Mexico (or surrounding states). Always well attended, these conferences provide a guidebook to participants. Besides detailed road logs, the guidebooks contain many well written, edited, and peer-reviewed geoscience papers. These books have set the national standard for geologic guidebooks and are an essential geologic reference for anyone working in or around New Mexico. Free Downloads NMGS has decided to make peer-reviewed papers from our Fall Field Conference guidebooks available for free download. Non-members will have access to guidebook papers two years after publication. Members have access to all papers. This is in keeping with our mission of promoting interest, research, and cooperation regarding geology in New Mexico. However, guidebook sales represent a significant proportion of our operating budget. Therefore, only research papers are available for download. Road logs, mini-papers, maps, stratigraphic charts, and other selected content are available only in the printed guidebooks. Copyright Information Publications of the New Mexico Geological Society, printed and electronic, are protected by the copyright laws of the United States. No material from the NMGS website, or printed and electronic publications, may be reprinted or redistributed without NMGS permission. Contact us for permission to reprint portions of any of our publications. One printed copy of any materials from the NMGS website or our print and electronic publications may be made for individual use without our permission. Teachers and students may make unlimited copies for educational use. Any other use of these materials requires explicit permission. This page is intentionally left blank to maintain order of facing pages.

Mesozoic Geology and Paleontology of the Four Corners Area

Geological Society of America Abstracts with Programs, 2021

GSA Field Guide 10: Roaming the Rocky Mountains and Environs: Geological Field Trips, 2008

The Black Canyon of the Gunnison and Unaweep Canyon in western Colorado have long been viewed as ... more The Black Canyon of the Gunnison and Unaweep Canyon in western Colorado have long been viewed as classic examples of post-Laramide Plio-Pleistocene uplift, which in the case of Unaweep, is thought to have forced the Gunnison River to abandon the canyon. Ongoing fi eld studies of the incision histories of these canyons and their surrounding regions, however, suggest that post-Laramide rock uplift has been regional, rather than local in nature. River incision rates calculated using ca. 10 Ma basaltic lava fl ows as a late Miocene datum suggest that long-term incision rates range from 61 to 142 m/m.y. with rates decreasing eastward towards the central Rocky Mountains. Incision rates calculated using the ca. 640 ka Lava Creek B ash range from 95 to 162 m/m.y., decrease eastward towards the mountains, and are broadly similar in magnitude to the longer-term incision rates. Locally, incision rates are as high as 500-600 m/m.y. along the lower reaches of the Black Canyon of the Gunnison, and these anomalously high values refl ect transient knickpoint migration upvalley. Knickpoint migration was controlled, in part, by downvalley base-level changes related to stream piracy. For example, abandonment of Unaweep Canyon by the Gunnison River could have led to rapid incision through erodible Mancos Shale as the Gunnison River joined the Colorado River on its course around the northern end of the Uncompahgre Plateau. Geophysical data show that abandonment of Unaweep Canyon was not caused by differential uplift of the crest of Unaweep Canyon relative to the surrounding basins. Instead, the ancestral (Plio-Pleistocene?) Gunnison River fl owed through Cactus Park, a major paleovalley that feeds into Unaweep Canyon, and continued downvalley to its juncture with the Dolores River near present-day Gateway, Colorado. The average gradient of the ancestral Gunnison River through the canyon prior to abandonment was ~7.5-7.6 m/km. Lithological and mineralogical considerations suggest that the Colorado River also fl owed through and helped to carve Unaweep Canyon, although the Colorado River probably exited Unaweep Canyon prior to abandonment by the Gunnison River. The ancestral Gunnison River remained in its course and incised through bedrock for a long enough period of time to produce terrace remnants in the Cactus Park region that range in elevation from 2000 to 1880 m. Abandonment of the canyon by the Gunnison River was followed by formation of a natural dam that probably led to deposition upvalley of ~50 m of lacustrine sediments in Cactus Park. Recent mapping in the lower reaches of Unaweep Canyon indicate that a landslide could have led to damming of Unaweep Canyon, perhaps while it was occupied by underfi t streams.

AAPG Bulletin, 2015

Lithofacies, architectural-element abundance, and estimates of dune-bedform height and channel si... more Lithofacies, architectural-element abundance, and estimates of dune-bedform height and channel sinuosity from borehole images (BHIs) and well-exposed outcrops allow for an expanded interpretation of the fluvial stratigraphic architecture of the Upper Cretaceous Williams Fork Formation. Sedimentologic and stratigraphic data from outcrops and detailed core descriptions of the Williams Fork Formation, Piceance Basin, Colorado, were used to compare attributes of fluvial architectural elements to BHI characteristics and spectral-gamma-ray (SGR) log motifs. Results show a distinct set of criteria based on BHIs that aid in the interpretation of lithofacies and fluvial reservoir architecture. In contrast, a practical correlation does not exist between outcrop-and core-derived SGR log motifs or thorium and potassium abundances and fluvial lithofacies or architectural elements. Four electrofacies based on BHI characteristics (e.g., dip type, dip pattern, and color scheme) represent the most common fluvial lithofacies and are identified through comparison of paired, calibrated BHIs and core. Cross-bed-set thickness values from BHIs are used to calculate dune height as a proxy for flow energy. The lower and middle Williams Fork Formation represent low-energy meandering and higher energy braided systems, respectively, as evident by changes in channel sinuosity and architectural-element type. The upper Williams Fork Formation is divided into two intervals based on lithofacies, architectural elements, channel sinuosity, and net-to-gross ratio. The subdivision for the upper Williams Fork Formation represents a change from a lower energy, meandering

Geological Society of America Abstracts with Programs

Through the Generations: Geologic and Anthropogenic Field Excursions in the Rocky Mountains from Modern to Ancient, 2010

... Laura J. Crossey Department of Earth and Planetary Sciences, University of New Mexico, Albuqu... more ... Laura J. Crossey Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, New Mexico 87131, USA Shari Kelley Department of Earth and Environmental Science, New Mexico Tech, Socorro, New Mexico 87801, USA Rex Cole Department of ...

The McCracken Sandstone Member of the Upper Devonian Elbert Formation, an important oil and natur... more The McCracken Sandstone Member of the Upper Devonian Elbert Formation, an important oil and natural-gas producer at Lisbon field, Utah, ranges in thickness from 81 to 114 ft (25-35 m), and has a complicated depositional history and stratigraphic architecture. Sedimentologic evaluation of drill core, 841 ft (256 m) from 8 wells, indicates that the McCracken is mainly dolomitic sandstone (55 percent), sandy dolomite (38 percent), and dolomitic mudrock (5 percent). Cyclical fluctuations in relative sea level during McCracken time produced three coarsening- and thickening-upward intervals (parasequence sets) in the Lisbon area, which correspond to the main reservoir units. Within these three packages, 18 lithofacies units are recognized that were deposited in at least 10 subenvironments, ranging from intertidal-supratidal carbonate flat to siliciclastic prodelta and delta front. Reservoir flow units are strongly dominated by siliciclastic lithofacies, whereas carbonate lithofacies compo...