Mountain Geologist最新文献

{"title":"The Mount Watson Formation, an Interpreted Braided-Fluvial Deposit in the Uinta Mountain Group (Upper Precambrian), Utah","authors":"Ivan D. Sanderson","doi":"10.31582/rmag.mg.21.4.157","DOIUrl":"https://doi.org/10.31582/rmag.mg.21.4.157","url":null,"abstract":"The Mount Watson Formation, a member of the upper Precambrian Uinta Mountain Group, is here proposed as a formal lithostratigraphic unit. It consists of predominantly very light gray or almost white interbedded quartz arenite and subarkose with minor pale red or grayish-red arkosic arenite and grayish-green shale. This name was initially proposed by Wallace (1972) but not established formally. Type area and type section are at Mount Watson, Utah, a major peak in the western part of the Uinta Range. The depositional environment is interpreted as braided-fluvial based on several characteristics. Evidence for a braided-fluvial environment includes: (1) the paucity of fine-grained elastic material either as matrix or as mudrocks, (2) range of sand grain size from very line to very coarse with frequently-associated granules and pebbles, (3) predominance of omicron (planar) and pi (trough) cross-stratification in sets ranging from 4 in (10 cm) to 16.5 ft (5 m) thick, (4) presence of desiccation cracks and terraced ripples indicating subaerial exposure, (5) unimodal character of paleocurrent indicators within cosets of strata, and (6) recognition of a vertical facies sequence that closely matches the Platts Type depositional model of Maill (1977, 1978, 1982) for braided-stream deposits. A major river flowed westward through the Precambrian basin of the Uinta Mountain Group and deposited multicyclic quartzose sediment derived from the craton to produce arenite. Tributary streams carrying feldspathic sediment entered the basin from the north. This sediment was deposited and lithified to arkosic arenite or was intermixed with multicyclic quartzose sand in the trunk stream to produce subarkose. This paleoenvironmental interpretation contrasts fundamentally with that of Wallace (1972), who completed his interpretation before workable process-response facies models were developed for the braided-stream environment.","PeriodicalId":101513,"journal":{"name":"Mountain Geologist","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1984-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129985198","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Stratigraphy and Palynology of the Upper Lewis Shale, Picture Cliffs Sandstone, and the Lower Fruitland Formation (Upper Cretaceous) near Durango, Colorado","authors":"C. Manfrino","doi":"10.31582/rmag.mg.21.4.115","DOIUrl":"https://doi.org/10.31582/rmag.mg.21.4.115","url":null,"abstract":"The stratigraphy and palynology of Upper Cretaceous units (upper Lewis Shale, Pictured Cliffs Sandstone, and lower Fruitland Formation) were investigated near Durango, Colorado, on the northern rim of the San Juan basin. This investigation: (1) confirms an interdeltaic depositional setting for these formations in the study area, (2) provides new biostratigraphic data for the Upper Cretaceous rocks on the northern rim of the San Juan basin, and (3) indicates a mostly freshwater origin for the Carbonero coal bed at the base of the Fruitland Formation. The upper Lewis Shale was deposited in lower offshore to upper offshore marine environments. The Pictured Cliffs Sandstone records a major regression on the western margin of the Late Cretaceous sea. The northeastward regression was not one steady event but a series of superimposed transgressive pulses. The depositional environments identified in the Pictured Cliffs Sandstone are upper offshore, shoreface, foreshore, and backshore. The lower part of the Fruitland Formation represents a coastal swamp deposit which developed just landward of the Pictured Cliffs Sandstones. The Carbonero coal bed lies at the base of the Fruitland Formation. At one location, a small tidal channel developed and inundated the local swamp environment. Ten Late Cretaceous palynomorph guide fossils were identified in the Lewis Shale, Pictured Cliffs Sandstone, and Fruitland Formation. The palynomorphs of the Lewis Shale and Pictured Cliffs Sandstone are a marine assemblage. The Fruitland Formation contains a terrestrial assemblage of pollen and spores. Trudopollis meekeri, Kuylisporites scutatus, and cf. Myrtaceoipollenites are a late Campanian Stage palynomorph assemblage in the Fruitland Formation. These findings refute the recent interpretation of a late Maestrichtian age for the Fruitland Formation. The palynological results obtained in this research can be used for correlation and mapping of interbasin and intrabasin sedimentary facies.","PeriodicalId":101513,"journal":{"name":"Mountain Geologist","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1984-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130395764","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Origin and Significance of the Wasatch and Valley Mountains Monoclines, Sanpete-Sevier Valley Area, Central Utah","authors":"I. J. Witkind, W. R. Page","doi":"10.31582/rmag.mg.21.4.143","DOIUrl":"https://doi.org/10.31582/rmag.mg.21.4.143","url":null,"abstract":"Two major opposing monoclines trend northward through the Sanpete-Sevier Valley area, central Utah. The Wasatch monocline, along the eastern edge of the area, faces west and forms the west flank of the Wasatch Plateau. Some 20 km (12 mi) to the west is the Valley Mountains monocline which faces east and forms the east flank of the Valley Mountains. Canyons cut in each monocline expose similar Cretaceous and Tertiary units that focally are complexly deformed. In both monoclines the same structural pattern has been impressed on these Cretaceous and Tertiary rocks, implying that both monoclines were formed approximately contemporaneously by the same geologic processes. We attribute the structural complexity of the Cretaceous-Tertiary sequence to the repeated growth and collapse of compound salt diapirs. We postulate at least three such diapiric episodes. The linearity, trend, and some of the height that mark each monocline are due partly to widespread fate Tertiary and Quaternary basin and range block faulting and partly to the dissolution of salt from individually distinct diapirs. This dissolution of salt removed the support for the overlying beds which then progressively sank. The sinking of discrete compound salt diapirs (one underlies Sanpete Valley and another underlies part of Sevier Valley) resulted in the full-scale formation of the Wasatch and Valley Mountains monoclines, respectively.","PeriodicalId":101513,"journal":{"name":"Mountain Geologist","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1984-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122691317","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Quealy Dome, Albany County, Wyoming: A Rocky Mountain Foreland Structural Trap Oil Field","authors":"D. L. Blackstone","doi":"10.31582/rmag.mg.21.3.85","DOIUrl":"https://doi.org/10.31582/rmag.mg.21.3.85","url":null,"abstract":"Quealy Dome, Albany County, Wyoming, is an asymmetric Rocky Mountain foreland fold on the west flank of the Laramie basin. Production is from the Lower Cretaceous Muddy Sandstone and Dakota Sandstone and from the Jurassic Sundance Formation and Permian-Pennsylvanian Casper Formation. Accumulation is structurally controlled. Internal structure of the fold involves \"out-of-the-syncline\" thrusting and post-folding normal faulting.","PeriodicalId":101513,"journal":{"name":"Mountain Geologist","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1984-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121112303","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Structure Along the Arlington Fault Zone, Pass Creek Area, Southern Hanna Basin, Wyoming","authors":"D. Stone","doi":"10.31582/rmag.mg.21.3.77","DOIUrl":"https://doi.org/10.31582/rmag.mg.21.3.77","url":null,"abstract":"Seismic and well data along the Arlington fault trend in the Pass Creek area of the southern Hanna Basin define a sharp, basin-edge flexure. Evidence for deeper faulting is equivocal. No faulting can be recognized on the logs or dipmeter in a well drilled through the steep dip zone, nor can the fault or no-fault situation be differentiated based on seismic evidence alone. However, it seems likely that thrust faulting exists at the deeper Precambrian basement level. The envisioned genetic sequence is one which, in response to regional compression, begins with development of an intra-basement thrust fault. The fault zone propagates upward under continued stress and attenuates into a sharp fold at shallower Cretaceous levels. The observed field structure has been easily duplicated in a corn starch-\"Play-doh\", thrust-fold model experiment under laterally directed stress.","PeriodicalId":101513,"journal":{"name":"Mountain Geologist","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1984-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132920186","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Depositional Environment and Diagenesis of the Teapot Sandstone, Southern Powder River Basin, Wyoming","authors":"P. Coughlan, J. Steidtmann","doi":"10.31582/rmag.mg.21.3.91","DOIUrl":"https://doi.org/10.31582/rmag.mg.21.3.91","url":null,"abstract":"The Teapot Sandstone is interpreted as a regressive, wave/fluvial dominated deltaic sequence, which prograded eastward into the Cretaceous Seaway. Marine lithofacies coarsen upward from bioturbated offshore siltstone to nearshore sandstone with large, pellet-lined Ophiomorpha. The overlying well-sorted, horizontally-laminated, foreshore sandstone exhibits ridge and runnel topography. Marine foreshore sandstone is overlain by complexly interbedded sandstone and carbonaceous shale in stacked, lining-upward sequences of the delta plain. Rootlets and contorted beds are common. Fining-upward units are interpreted as abandoned channels. Coarsening-upward sequences are interpreted as interdistributary bay or lagoonal deposits. Capping the sequence is a thick, crossbedded, fluvial section consisting of levee, point bar, and channel sand deposits. Slumped beds, intraformational basal conglomerates, and minor eolian ripple laminations are present in fluvial sandstone. The Teapot Sandstone has a complex diagenetic history. Siderite and framboidal pyrite formed early in the diagenetic sequence at shallow depths of burial under anaerobic conditions. Pore-filling kaolinite, chlorite, and quartz overgrowths formed coevally following dissolution of relatively unstable framework grains. Poikilotopic calcite is locally abundant and extensively replaces framework grains. Depositional facies exert strong control of diagenetic patterns. Kaolinite occurs predominantly in fluvial sandstone. Chlorite is restricted to marine facies and calcite is further restricted to well-sorted foreshore marine sandstone. Quartz overgrowths occur only in relatively well-sorted sandstone, whereas pyrite and siderite are common in shaly sandstone and siltstone. Nearshore marine and fluvial sandstones are potential hydrocarbon reservoirs, although authigenic clays have significantly reduced permeability. Reservoir potential of we/I-sorted foreshore marine sandstone was destroyed by pore-filling calcite cement. Delta plain deposits are too thin, discontinuous, and poorly-sorted to form significant reservoirs.","PeriodicalId":101513,"journal":{"name":"Mountain Geologist","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1984-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114582357","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Hydrodynamic Control on an Oil Entrapment in Channel Sandstones of the Dakota Sandstone, South Cole Creek Field, Converse County, Wyoming","authors":"W. R. Moore","doi":"10.31582/rmag.mg.21.3.105","DOIUrl":"https://doi.org/10.31582/rmag.mg.21.3.105","url":null,"abstract":"South Cole Creek field, located in the southwest Powder River Basin of Wyoming has produced 11 million barrels of oil from the Dakota Sandstone. Detailed mapping of rock and reservoir properties including sandstone isopachs, initial potentials, cumulative production, and porosity-permeability data, reveals the existence of channel sandstones with excellent reservoir properties which are surrounded by marine rocks of poorer reservoir properties. The areal extent of the accumulation is controlled by factors other than structure and stratigraphy, as water-bearing channel sandstones exist lateral to and up-dip of producing channel sandstones. By comparing the known accumulation to the theoretical model for fluid flow, it can be shown that hydrodynamics has played an important role in modifying the accumulation at South Cole Creek field.","PeriodicalId":101513,"journal":{"name":"Mountain Geologist","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1984-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116455449","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The Rattlesnake Mountain, Wyoming, Debate: A Review and Critique of Models","authors":"D. Stone","doi":"10.31582/rmag.mg.21.2.37","DOIUrl":"https://doi.org/10.31582/rmag.mg.21.2.37","url":null,"abstract":"Structural interpretation of Rattlesnake Mountain, located on the west flank of the Big Horn Basin, Wyoming, at Buffalo Bill Reservoir, has been the subject of lively debate since at least 1930. Six structural \"models\" of this feature published previously, representing both the verticalists' \"drape fold\" and the horizontal compressionists' thrust-fold interpretations, are shown and dis­ cussed. It is concluded that the \"drape fold\" model for Rattlesnake Mountain or for any other intrabasin fault-fold structure in the Rocky Mountain fore/and is fundamentally untenable, and that the developmental sequence proposed by Blackstone in 1940 is essentially correct as indicated by data from deep wells and modern seismic profiling. However, a number of questions still need answers.","PeriodicalId":101513,"journal":{"name":"Mountain Geologist","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1984-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129583682","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Haybarn Field, Fremont County, Wyoming: An Upper Fort Union (Paleocene) Stratigraphic Trap","authors":"R. Robertson","doi":"10.1306/03B5B970-16D1-11D7-8645000102C1865D","DOIUrl":"https://doi.org/10.1306/03B5B970-16D1-11D7-8645000102C1865D","url":null,"abstract":"Haybarn field was discovered in the fall of 1981 and produces stratigraphically trapped 43.7° API gravity oil from shallow reservoir sandstones in the upper member of the Fort Union Formation. The sandstones were deposited in a marginal lacustrine delta front setting in the Wind River Basin, Wyoming. The interfingering lacustrine Waltman Shale has provided the trapping mechanism for the field. The Waltman Shale also appears to be the petroleum source; this primary source, however, was probably deposited in deeper portions of the basin north of the field rather than immediately adjacent to the reservoir. The reservoir sandstones are arkosic and have excellent porosity averaging about 20%. Clays in the reservoir appear to be entirely secondary suggesting that the sandstones were deposited in a high energy, wave-dominated depositional system. Electrical log evaluation of the Upper Fort Union reservoirs is complicated by variations in formation water resistivities between and within the sandstone tongues. The uppermost section of the Upper Fort Union member tends to be fresh water-bearing, while the producing zones in the lower portion of the member have much lower, more saline Rw's.","PeriodicalId":101513,"journal":{"name":"Mountain Geologist","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1984-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121244013","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A Colorado-Wyoming Border Diatreme and a Possible Potential Kimberlite Indicator Plant","authors":"D. B. Collins, D. S. Collins","doi":"10.31582/rmag.mg.21.2.68","DOIUrl":"https://doi.org/10.31582/rmag.mg.21.2.68","url":null,"abstract":"Small breccia pipes (diatremes) composed of kimberlite and other rare mantle rocks which contain potentially economic deposits of diamonds are scattered near the Colorado-Wyoming border in the northern Front Range of the southern Rocky Mountains. The Schaffer 13 diatreme study area, located on the Colorado-Wyoming border northwest of Virginia Dale, Colorado, is the focus of this report. During initial fieldwork there, samples of garnet, ilmenite, and various ultramafic nodules were collected. Several previously undiscovered protections of the diatreme were mapped. A small, apparently separate diatreme was also discovered west of the Schaffer 13. The gold aster (Chrysopsis foliosa) grew around the edges of the diatreme on the surrounding granite surface, but did not grow on the weathered kimberlite surface. The asters bloom from June to early August, forming a definitive, colorful boundary in areas of low relief, poor drainage, and good residual soils. Use of the plants to determine the boundaries is difficult in areas of active drainage and relatively high relief where the actively transported soil is well diluted by both kimberlite and granite .","PeriodicalId":101513,"journal":{"name":"Mountain Geologist","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1984-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128948077","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}