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R. M. Flores

Publications and source records attributed to R. M. Flores.

34 records · Page 2Linked to original sources
USGS1989

Rocky Mountain Tertiary coal-basin models and their applicability to some world basins

Tertiary intermontane basins in the Rocky Mountain region of the United States contain large amounts of coal resources. The first major type of Tertiary coal basin is closed and lake-dominated, either mud-rich (e.g., North Park Basin, Colorado) or mud plus carbonate (e.g., Medicine Lodge Basin, Montana), which are both infilled by deltas. The second major type of Tertiary coal basin is open and characterized by a preponderance of sediments that were deposited by flow-through fluvial systems (e.g., Raton Basin, Colorado and New Mexico, and Powder River Basin, Wyoming and Montana). The setting for the formation of these coals varies with the type of basin sedimentation, paleotectonism, and paleoclimate. The mud-rich lake-dominated closed basin (transpressional paleotectonism and warm, humid paleoclimate), where infilled by sandy “Gilbert-type” deltas, contains thick coals (low ash and low sulfur) formed in swamps of the prograding fluvial systems. The mud- and carbonate-rich lake-dominated closed basin is infilled by carbonate precipitates plus coarse-grained fan deltas and fine-grained deltas. Here, thin coals (high ash and high sulfur) formed in swamps of the fine-grained deltas. The coarse-clastic, open basins (compressional paleotectonism and warm, paratropical paleoclimate) associated with flow-through fluvial systems contain moderately to anomalously thick coals (high to low ash and low sulfur) formed in swamps developed in intermittently abandoned portions of the fluvial systems. These coal development patterns from the Tertiary Rocky Mountain basins, although occurring in completely different paleotectonic settings, are similar to that found in the Tertiary, Cretaceous, and Permian intermontane coal basins in China, New Zealand, and India.

International Journal of Coal Geology↗
USGS1987

Sedimentologic and stratigraphic framework of the upper part of the Fort Union Formation, western Powder River basin, Wyoming

The purpose of this study is to describe the stratigraphy and interpret the environments of deposition in the upper part of the Paleocene Fort Union Formation. Of all the lithofacies present within the study area, sandstone is the most dominant and makes up most of the upper part of the Fort Union Formation along the western edge of the Powder River basin, Wyoming. This sandstone lithofacies occurs in three forms: 1) pink conglomeratic sandstone, 2) coarse-grained sandstone, and 3) fine-grained sandstone. The pink conglomeratic sandstone lithofacies forms a series of Stacked channel bodies in which the clasts are as much as 1 3/4 in. in diameter. The coarse-grained sandstone lithofacies is laterally equivalent to the pink conglomeratic sandstone sequence, but contains smaller clasts; it is arranged en echelon (offset) to the north. The fine-grained sandstone lithofacies, limited to the northern part of the study area, is not as laterally continuous as the pink conglomeratic sandstone lithofacies to the south. Basal lag conglomerate underlies both the conglomeratic sandstone and coarse-grained sandstone lithofacies, but not the fine-grained sandstone. The presence of a fine-grained sandstone lithofacies lateral to the conglomeratic sandstone and coarse-grained sandstone lithofacies suggests the presence of a coarse-grained braided and meandering fluvial system coeval with a fine-grained meandering fluvial system.. The meandering fluvial systems drained the alluvial plain flanking the Bighorn Mountains on the west and the Casper arch on the southwest, and flowed north-northeastward within the Powder River basin.

Wyoming↗
USGS1984

Paleogeographic controls of coal accumulation, Cretaceous Blackhawk Formation and Star Point Sandstone, Wasatch Plateau, Utah

Analysis of sequences, associations, and relationships of facies in the Upper Cretaceous Blackhawk Formation and Star Point Sandstone in the Wasatch Plateau, Utah, leads to inferences regarding the paleogeographic controls affecting the accumulation of coals in delta–barrier-island complexes. Progradation, lateral shifting, and abandonment of these complexes created four major landward-thinning tongues of the upper sandstone bed of the Star Point Sandstone that extend into the lowermost Blackhawk Formation. Each tongue of the Star Point Sandstone trends northwest to southeast, subparallel to the general orientation of the Late Cretaceous paleoshoreline, and represents accretion-ridge, distributary-channel, and mouth-bar sandstones. The accretion-ridge or barrier-island sandstones grade landward into coastwise lagoonal and back-barrier swamp deposits, which, in turn, merge with bayhead deposits of short-headed streams. These deposits grade laterally into delta-plain deposits that consist of major distributary channels which crosscut the coastwise lagoons. Two coal populations were formed in this paleogeographic setting: delta-plain and back-barrier coals. Delta-plain coals formed as thin to thick, discontinuous bodies. Back-barrier coals are thicker and more laterally continuous. They parallel depositional strike and accumulated in swamps on surfaces of infilled lagoons. Here, the swamps were sites of accumulation of thick coals and were influenced by abandonment of associated deltaic barrier-island complexes. Successive offlap events resulted in accumulation of the Hiawatha coal, not as a single continuous bed, but as a series of discontinuous, related coal bodies.

Utah↗
USGS1983

Environmental-stratigraphic cross sections of the Cretaceous Fox Hills Sandstone and Hell Creek Formation and Paleocene Fort Union Formation, Richland and Roosevelt Counties, Montana

This study was conducted to determine the stratigraphic, lithofacies, and deopsitional relationships of the Cretaceous Fox Hills Sandstone and Hell Creek Formation and The Paleocene Fort Union Formation. These relationships, shown in sections A-A', B-B', C-C', and D-D', we established form nearly continuous exposures in the Missouri River valley in Richland and Roosevelt Counties, Mont. The river valley topography is characterized by badlands, which permitted detailed description and construction of the stratigraphic framework of the formations within a 30-mi-long belt of exposures paralleling the Missouri River. This area of study is on the western flank of the Williston Basin and east of the Poplar Dome. The latter structure imparted a northeasterly regional dip to the rocks, which averages 25 ft per mi and is as much as 100 ft per mi according to Spencer (1980). The regional dip resulted in exposure of older rocks (Cretaceous) in the west to younger rocks (Tertiary) in the east.

Montana↗
USGS1982

Use of geophysical logs in recognizing depositional environments in the Tongue River Member of the Fort Union Formation, Powder River area, Wyoming and Montana

The environmental conditions under which rocks in the Paleocene Tongue River Member of the Fort Union Formation were deposited in the Powder River area, Wyoming and Montana, can be determined using geophysical logs with some limitations. It is widely recognized that gamma ray and density logs are useful in identifying thickness and stratigraphic position of coal beds. In addition, gamma ray and electrical resistivity logs can be used to infer conditions of transportation and deposition of sandstones, siltstones, and other rock types. In particular, intensity responses of the gamma ray and resistance logs provide a clue to variations of grain size such as fining-upward and coarsening-upward characteristics of fluvial channel and crevasse splay deposits, respectively. These signatures in the geophysical logs are readily observed for some beds; for other beds however, the depositional conditions are difficult to determine because the beds do not produce clear-cut log-response patterns. Thus,. analysis of the environments of deposition of detrital rocks in drill holes can be made more accurate by a study of stratigraphically equivalent intervals in outcrops near drill-hole sites.

Open-File Report↗
USGS1982

Characteristics of deltaic deposits in the Cretaceous Pierre Shale, Trinidad Sandstone, and Vermejo Formation, Raton Basin, Colorado.

Detailed facies analyses of closely spaced measured surface sections in the Trinidad and adjacent areas of Colorado reflect deposition in the river-influenced delta. That this deltaic system was accompanied by abandonment of subdeltas is indicated by a destructional-deltaic facies of heavily bioturbated, carbonaceous sandstones, siltstones, and shales best recorded in the delta front deposits of the Trinidad Sandstone. Coal accumulation of the Vermejo deposits nevertheless remained primarily controlled by persistent organic sedimentation in interdistributary backswamps. These backswamps, which accumulated thick, lenticular coals, were formed during the normal constructional phase of the delta plain. -from Authors

Mountain Geologist↗
USGS1981

Differentiation of delta-front and barrier lithofacies of the Upper Cretaceous Pictured Cliffs Sandstone, southwest San Juan Basin, New Mexico.

This Sandstone represents a regressive littoral marine unit deposited during the final retreat of the Cretaceous epeiric sea. Differences in rock type, internal and penecontemporaneous deformation structures, textural sequences, mineral composition and trace fossil content permit recognition of laterally contemporaneous delta-front and barrier lithofacies. The delta-front lithofacies consists of distal bar, distributary mouth bar, and distributary channel deposits. The barrier lithofacies consists of shoreface, beach, washover channel, tidal inlet, tidal channel, and ebb-tidal delta deposits; these lithofacies are coarsening-upward sequences of shale, siltstone and sandstone, locally scoured in the upper part by fining-upward channel deposits.-from Authors

Mountain Geologist↗
USGS1979

Coal depositional models in some Tertiary and Cretaceous coal fields in the U.S. Western Interior

Detailed stratigraphic and sedimentological studies of the Tertiary Tongue River Member of the Fort Union Formation in the Powder River Basin, Wyoming, and the Cretaceous Blackhawk Formation and Star Point Sandstone in the Wasatch Plateau, Utah, indicate that the depositional environments of coal played a major role in controlling coal thickness, lateral continuity, potential minability, and type of floor and roof rocks. The potentially minable, thick coal beds of the Tongue River Member were primarily formed in long-lived floodbasin backswamps of upper alluvial plain environment. Avulsion of meandering fluvial channels contributed to the erratic lateral extent of coals in this environment. Laterally extensive coals formed in floodbasin backswamps of a lower alluvial plain environment; however, interruption by overbank and crevasse-splay sedimentation produced highly split and merging coal beds. Lacustrine sedimentation common to the lower alluvial plain, similar to the lake-covered lower alluvial valley of the Atchafalaya River Basin, is related to a high-constructive delta. In contrast to these alluvial coals are the deltaic coal deposits of the Blackhawk Formation. The formation consists of three coal populations: upper delta plain, lower delta plain, and ‘back-barrier’. Coals of the lower delta plain are thick and laterally extensive, in contrast to those of the upper delta plain and ‘back-barrier’, which contain abundant, very thin and laterally discontinuous carbonaceous shale partings. The reworking of the delta-front sediments of the Star Point Sandstone suggests that the Blackhawk-Star Point delta was a high-destructive system.

Utah, Wyoming↗
USGS1979

Restored stratigraphic cross sections and coal correlations in the Tongue River member of the Fort Union Formation, Powder River area, Montana

Exposures of the lower two thirds of the Tongue River Member of the Paleocene Fort Union Formation were measured along the Powder River valley in southeastern Montana in the Moorhead and Birney-Broadus coalfields. This report documents the stratigraphic variations, lateral continuity of partly eroded coal beds along the line of section, and shows ten sections for the Tongue River Member in this study area. This report is a companion to the report by Flores and Canavello (1979). The study area represents a linear distance of 35 miles along the Powder River valley and extends from the Wyoming-Montana State line to a point 7 miles southeast of Broadus. Mont. (see index map). Within this area are relatively continuous outcrops of the middle and lower parts of the Tongue River Member.

Montana↗
USGS1978

Factors controlling heavy-mineral variations on the South Texas outer continental shelf, Gulf of Mexico

Heavy-mineral distribution on the outer continental shelf off the southern coast of Texas shows regional variability induced by provenance and local variability reflecting genetic differences in sea-floor sediments. Q-mode factor analysis showed that three suites of heavy minerals are present. The southern ancestral Rio Grande delta sediments contain a distinct opaque-pyroxene-garnet suite, whereas the northern ancestral Brazes-Colorado delta sediments contain a tourmaline-green hornblende suite. An interdelta region contains a heavy mineral suite that is mixed owing to contributions from both ancestral deltas. Analysis of variance, correlation, and regression methods indicate that heavy-mineral variations in each sedimentary province have been significantly influenced by hydraulic fractionation by size, shape, and density, and by a selective chemical decomposition of unstable minerals. These factors have operated at varying degrees on the relict, palimpsest, and modern sediment populations of the sedimentary provinces since the end of Pleistocene time. The differential effects of these processes on the sediments have resulted in local variations that contribute to the total mineralogical variability. A comparison of the heavy mineral suites of the modern and relict Rio Grande delta sediments, which are derived from a common provenance, also shows mineral variations resulting from factors other than provenance.

Texas↗