Romeo M. Flores

Short-Headed Stream Delta: Model for Pennsylvania Haymond Formation, West Texas

The most commonly applied deltaic model in lithogenetic analysis of ancient deposits has been that constructed by major river systems. Perhaps an equally important model is the short-headed stream delta model exemplified by the Pennsylvanian Haymond Formation in the Marathon basin. This model consists of clay, silt-sand couplets in the lower part, and bouldery conglomeratic sand in the upper part. The lower fine-grained deposits represent prodelta and delta front, the upper coarse-grained deposits are the delta plain. The difference between short-headed stream-delta deposits and their large river-delta equivalents arises in the nature of the delta front--delta plain deposits. In the Haymond Formation, the flysch-like delta-front interval probably indicates proximity to the source terrane in the southeast and sediment influxes in amounts greater than the organisms can rework. The gravelly sand delta-plain deposits indicate that most of the clay and silt common on other delta plains was flushed farther offshore. The small proportion of current-bedded shale and siltstone suggests a largely subaqueous delta plain; however, some subaerial sedimentation is indicated by bleached, root-marked sandstone. In addition, the delta plain was traversed by braided distributaries as evidenced by multiple-channel sa dstones. That the channels were choked by a vast assortment of large particles probably transported during periods of greatest runoff is indicated by the basal conglomerates and boulder beds. However, some large boulders may have been reworked from nearby coastal scree detritus and steep cliffs during intense storms.

Fluvial Facies Associations--Guide to Tertiary Coal Development and Exploration in Powder River Basin, Wyoming and Montana: ABSTRACT

The Paleocene Tongue River Member of the Fort Union Formation supports widespread coal-mining activity and contains most of the recoverable coals in the Powder River basin. Coals are well-developed in eastern and northern Powder River basin, but the best exposures are in the northern part. Most mining is from the very thick (as much as 125 ft or 38 m) coals; however, as these coal reserves are depleted, future exploration will focus on moderately thick coals. Exploration guides for the moderately thick coals may be their facies associations. In the northern Powder River basin, 175 mi (280 km) of cross sections, constructed from closely spaced outcrop sections and drill holes, provide detailed facies associations of the coals. One facies association is dominated by thick fluvial-channel sandstones and coals as much as 40 ft (12 m) thick and 12 mi (19 km) in extent. The coals formed in poorly drained backswamps in which uniformly thick peat bogs accumulated, subparallel to meandering channels and opposite their migration and avulsion directions. A second facies association is characterized by abundant crevasse sandstones, subordinate thin channel sandstones, and lacustrine limestones, shales, and siltstones. Facies-associated coals, as much as 8.5 ft (17 m) thick and 5 mi (8 km) in extent, formed in well-drained backswamps frequently interrupted by crevasse splays that debouched into flood-plain lakes. The best development of economic coals of the fluvial-channel dominated facies is in the lower part of the ongue River Member, and that of the flood-plain-lacustrine coal-facies association is in the upper part. End_of_Article - Last_Page 926------------

Facies Control of Upper Cretaceous Cleary and Gibson Coal Members near Gallup, New Mexico: ABSTRACT

End_Page 556------------------------------The Upper Cretaceous Point Lookout Sandstone separates the Cleary Coal Member of the Menefee Formation from the Gibson Coal Member of the Crevasse Canyon Formation in much of the Chaco slope and southwest San Juan basin. These coal-bearing members merge as the intervening Point Lookout Sandstone pinches out to the southwest in the direction of the Nutria monocline and Gallup coal field. The deposits of the merged coal interval supported widespread mining activity northwest and north of Gallup, New Mexico, near the turn of the century; however, renewed mining of these coals for the past few years has concentrated northwest of the town. Closely spaced outcrop sections provided data from which to infer the depositional settings of the merged coals. Northwest of Gallup (Enterprise mine area), an alluvial facies of channel sandstones, deposited by northward-flowing streams is complexly interspersed with interfluvial siltstones and with laterally discontinuous coal deposits. North of Gallup (Gibson and Heaton mine areas), better integrated sandstones deposited in north-to-northeast flowing distributary channels, subordinate crevasse-splay sandstones, more widespread coal zones, and common bioturbations in laminated carbonaceous siltstones suggest coal accumulation in a deltaic to lagoonal transition environment. Further northeast of Gallup, where the Nutria monocline changes to an easterly strike toward the Chaco slope, well-developed coals remain associated with the deltaic and lagoonal environments. However, these coal-forming en ironments grade northeastward into the Point Lookout back-barrier to lagoonal transition environments, where coal deposits are poorly developed. End_of_Article - Last_Page 557------------

Variations in Cretaceous Coal-Bearing Strata, Gallup Coal Field, New Mexico: ABSTRACT

Cretaceous coals of the western Gallup field, New Mexico, occur with detrital wedges that interfinger to the northwest with brackish-marine sediments of the San Juan basin. This study documents detailed stratigraphic relations and the relation of coal occurrence to depositional environments of the Gallup, Crevasse Canyon, and Menefee formations. One hundred and fifteen sections form the basis for three-dimensional reconstructions of a 30-sq km area northwest of Gallup. The regressive Gallup Sandstone represents reworking of river-mouth sands into coastal barriers where coals accumulated in back-barrier subfacies. This formation grades upward into the Dilco Coal Member of the Crevasse Canyon Formation characterized by varve-like fine-grained sediments, thin sandstones, and coals, which pass upward into thick, northwesterly transported fluvial sandstones. These merge laterally and upward into northerly oriented, thick paleochannel sandstones of the Bartlett Barren Member of the Crevasse Canyon Formation. The coal-bearing Gibson Coal Member of the Crevasse Canyon Formation, which cannot be differentiated from the Cleary Coal Member of the overlying Menefee Formation, contains finer grained sediments and coals deposited in a broad interfluvial depressio bounded on the west by Bartlett alluvial channel facies. Coal accumulation in this depression was terminated by southeasterly oriented, crevasse-like deposits associated with thick fluvial sandstones (Menefee Formation). Stratigraphic variations of coal beds are directly related to their proximity to contemporaneous channel facies. Uniformly thick coals trend subparallel to channel facies; near the channel facies, coals become erratic and pass into rooted, carbonaceous overbank detritus. Coals are offset locally by faults caused by differential compaction beneath overlying channel sandstones. End_of_Article - Last_Page 689------------

Coal Variations in Fluvial Deposition of Paleocene Tongue River Member of Fort Union Formation, Powder River Area, Wyoming and Montana: ABSTRACT

The coal-bearing Tongue River Member of the Fort Union Formation in the Powder River basin exemplifies fluvial deposits of Tertiary intermontane basins. The Tongue River Member coals are targets of extensive drilling exploration and development. About 200 sections, spaced an average of 0.5 mi (0.8 km) apart, were measured in a 60-mi (96 km) continuous outcrop along the Powder River in Wyoming and Montana to determine the environmental-stratigraphic framework of the coals in the 1,500-ft (450 km) thick Tongue River Member. Coal-bed distribution in this area may be typical of that in many parts of the basin. The coals are distributed in two major facies: a lower (1,100 ft or 330 m thick) fluvial channel dominated facies, and an upper (400 ft or 120 m thick) lake-dominated, interfluvial and fluvial channel facies. Major coals, including the Anderson, Canyon, Cook, Wall, Pawnee, and Cache, were formed in the fluvial channel dominated facies, which contains numerous en echelon channel sandstones that range from 50 to 200 ft (15 to 60 m) thick and from 1 to 9.5 mi (1.6 to 15.2 km) in lateral extent. The offset arrangement of the sandstones suggests shifts of meandering channels among low-lying poorly drained interchannel backswamps which were filled by overbank-crevasse sandstone, siltstone, and shale. These backswamps, as well as poorly drained backswamps developed on abandoned channel ridge , were sites of coal deposition. Coal beds in this facies locally thicken from 1 to 30 ft (0.3 to 9 m) within 3 to 7 mi (4.8 to 11.2 km) and were traced in outcrops for 8 to 12 mi (13 to 19 km) as lenticular bodies. They split laterally, grade into carbonaceous shale, or are truncated by channel sandstones. The lake-dominated interfluvial and fluvial channel facies consist of abundant crevasse-splay sandstone, siltstone, and shale, and lacustrine limestone and shale that contain abundant freshwater mollusks. A few channel sandstones are present; these range from 30 to 80 ft (9 to 24 m) thick and from 0.5 to 3 mi (0.8 to 4.8 km) across. The crevasse and channel deposits developed poorly drained to well-drained backswamp platforms where coals formed. Coal beds, including the Smith and Roland, average about 2.5 ft (0.7 m) thick and are laterally continuous in outcrops for as much as 5 mi (8 km). Crevasse splays dominated the interfluvial-lacustrine sedimentation and commonly interrupted lateral continuity by splitting the coal beds. Thus, of the two major facies, the more coal productive is the fluvial channel dominated facies. The development of thick, lenticular coal beds in this facies was directly influenced by depositional settings of poorly drained backswamps which formed mainly on abandoned channel ridges and overbank areas. End_of_Article - Last_Page 826------------

Pictured Cliffs Sandstone--Upper Cretaceous Distributary-Channel, Delta-Front, and Beach-Bar Deposits, Southwestern San Juan Basin, New Mexico: ABSTRACT

The Upper Cretaceous Pictured Cliffs Sandstone in the Bisti-Burnham area in southwestern San Juan basin, New Mexico, contains distributary-channel, delta-front, and beach-bar deposits. The distributary-channel deposit is a basally erosional, festooned, convoluted, and rippled sandstone. The delta-front deposits include distributary-mouth-bar sandstone, distal-bar sandstone, siltstone, shale, and intervening contorted sandstone. The distributary-mouth-bar sandstone is subparallel laminated, rippled, and festooned. The distal-bar sandstone is subparallel laminated and rippled. The intermediate contorted sandstone contains fold and ball-and-pillow structures. The distributary-channel and delta-front sandstones are very fine to fine grained, quartz poor (39%), and sparsely bu rowed by Ophiomorpha. The beach-bar deposits include shoreface-beach sandstone, siltstone, and shale, and tidal-channel and washover sandstones. Lower-shoreface deposits include parallel-laminated, rippled sandstone and bioturbated shale and siltstone. Middle-shoreface sandstone consists of a subparallel-laminated, rippled, and locally burrowed lower part, and a planar-cross-bedded and commonly burrowed upper part. Upper-shoreface-beach deposits consist of planar-cross-bedded, sparsely burrowed sandstone and lenticular, festooned, rippled, burrowed sandstone grading upward into subparallel-laminated, festooned, burrowed sandstone. The shoreface-beach deposits are dissected by bidirectionally End_Page 451------------------------------ festooned and planar-cross-bedded tidal-channel sandstone and festooned, burrowed washover sandstone. The beach-bar sandstones are very fine to medium grained, quartz rich (54%), and commonly burrowed by Ophiomorpha. Differentiation of Pictured Cliffs Sandstone depositional environments led to recognition of deltaic and back-barrier coal deposits of the overlying Fruitland Formation. End_of_Article - Last_Page 452------------

Variations in Heavy Mineral Composition During Transport of Short-Headed Stream Sands: ABSTRACT

Past studies on variation in heavy minerals along large streams have shown that progressive change, or lack of it, during transport is due to abrasion, dilution, hydraulic conditions, and sorting on the basis of size, density, and shape. In the light of these studies assessment of the variation in heavy minerals was made along the short-headed Canadaway and Cattaraugus Creeks in western New York. In that area the glacial drift and moraine deposits are ready sources of heavy minerals. Major annual erosion and transportation of these materials occur during peak streamflow in March-April and deposition during decreased flow in the succeeding months. Thus, during the summer of 1968, efforts were made to collect part of the bedload deposited during the interim period of optimu and minimum streamflow. Analyses of samples of similar size distributions show that variation in heavy minerals during transit occurs along these creeks and the relation is best developed in the coarse fractions. Results show a decrease in garnet and complementary increase in hypersthene, hornblende, and tourmaline downstream. Comparison of variation in heavy minerals reveals that although overall difference in weight percent exists, the relation of these minerals and the transport direction do not differ significantly between the two creeks. Consideration of the possible causes of heavy mineral variation indicates that it is not due to dilution and abrasion. This modification may result from progressive sorting on the basis of size, density, and shape as produced by the annual current-flow fluctuations. End_of_Article - Last_Page 338------------

Shallow-Water Facies of Upper Pennsylvanian Haymond Formation in Marathon Basin, Texas: ABSTRACT

The Upper Pennsylvanian Haymond Formation crops out along the southeast, east, and northeast parts of the Marathon basin, Texas, and consists of two major units of thin- to thick-bedded, fine- to medium-grained sandstone separated by boulder beds. These rock types overlie and grade into the underlying deep-water turbidite sequence which is composed of interbedded fine- and very fine-grained sandstone and dark-gray shale. The sandstones occur as en echelon, lenticular bodies which have partly erosional bases, and laterally interfingering, gradational upper boundaries. The sandstone beds are massive at the base, grading upward into a End_Page 717------------------------------ trough cross-bedded and ripple-bedded top. The lower sandstone unit is interbedded with black to dark-gray, carbonaceous shale and siltstone, whereas the upper sandstone unit is recognized by associated basal conglomerate or interbedded lenticular conglomeratic beds, and poorly bedded, plant-disturbed sandstones. The boulder beds, between the sandstone units are composed of novaculite, limestone, sandstone, and conglomerate, and are interstratified with black, carbonaceous shale and gray siltstone. The boulders are considered to be of tectonic origin, probably derived as a result of faulting and/or uplift of the source area. The environment of deposition of this facies is shown by features associated with the sandstone units. The erosion channels, occurrence of conglomeratic beds with the sandstones, poorly bedded and plant-disturbed sandstones, interstratification with carbonaceous shale, lack of marine fossils, and development of large-scale cross-bedded sandstones in general suggest a very restricted shallow-water to transitional deep-water depositional environment for these strata. End_of_Article - Last_Page 718------------

Genetic Types of Some Sandstones in the Allegheny Formation of Ohio: ABSTRACT

Sandstones between the Middle Kittanning and Lower Freeport coal beds in the Allegheny Formation of southeastern Ohio are divisible into three genetic categories based on gross external morphology of the sand body, proportion of major mineral components, grain size, and homogeneity of cross-bed orientation. The following types are continuously arrayed in eastwest trending bands along a northeast-southwest outcrop: 1) Thin, lenticular, discontinuous sand bodies with quartz content about 58 per cent. Among all other constituents, feldspar averages 15 per cent, muscovite 25 per cent, chlorite-biotite 60 per cent. Sands are predominantly fine to medium grained and cross-bedding is randomly oriented. 2) Thick, less widespread, partly continuous, elongate sand bodies in which quartz averages 54 per cent. Among all other constituents, feldspar, averages 25 per cent, muscovite 30 per cent, chlorite-biotite 45 per cent. Sand is medium grained and cross-bedding is weakly oriented. 3) Thick, widespread apron or sheet sands in which quartz averages 62 per cent. Among all other constituents, feldspar averages 35 per cent, muscovite 30 per cent, chlorite-biotite 35 per cent. Sands are predominantly medium to coarse grained and cross-bedding is oriented in a northwest-southeast direction. Type 1, found in the southern part of the area, is believed to represent a meandering, relatively nearshore portion of a fluvial system. In contrast, Type 3, found in the northern part of the area, probably represents sand distribution beyond the area of well-developed channels, perhaps near distributary mouths. Type 2, found between areas of Types 1 and 3, presumably reflects an intermediate situation. End_of_Article - Last_Page 340------------