Mountain Geologist最新文献

{"title":"Appendix III: High-Sensitivity Aeromagnetic Analysis","authors":"W. Pearson","doi":"10.31582/rmag.mg.52.1.72","DOIUrl":"https://doi.org/10.31582/rmag.mg.52.1.72","url":null,"abstract":"","PeriodicalId":101513,"journal":{"name":"Mountain Geologist","volume":"36 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127711826","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":"Appendix II: Geochemistry of Paleozoic Oils - Denver Basin","authors":"R. Kettler","doi":"10.31582/rmag.mg.52.1.64","DOIUrl":"https://doi.org/10.31582/rmag.mg.52.1.64","url":null,"abstract":"","PeriodicalId":101513,"journal":{"name":"Mountain Geologist","volume":"69 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133407251","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":"Dinosaur Footprints from the Dakota Group of Eastern Colorado","authors":"M. Lockley","doi":"10.31582/rmag.mg.24.4.107","DOIUrl":"https://doi.org/10.31582/rmag.mg.24.4.107","url":null,"abstract":"Dinosaur footprints from the Dakota Group In eastern Colorado are known from at least eight different locations but are essentially undocumented, and unprotected. Detailed analysis reveals that trackways from two sites include front foot (manus) impressions of ornithopods, which are probably the most distinctive yet described The tracks shed light on the morphology and gait of large ornithopods, which were probably of iguanodontid affinity The tracks can be assigned to the ichnogenus Caririchnium which also occurs in South America The lack of skeletal remains in the Dakota Group and the good quality of many tracks suggests that footprints should be examined more care- fully for the useful paleoecologic census information they provide in some cases they may be used for local stratigraphic correlation.","PeriodicalId":101513,"journal":{"name":"Mountain Geologist","volume":"56 30","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1988-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"113957445","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 Wrench Fault/Thrust-Fold Clay Model Study and Comparison with the Bonanza-Zeisman Area of the Eastern Big Horn Basin","authors":"D. Stone","doi":"10.31582/rmag.mg.24.4.87","DOIUrl":"https://doi.org/10.31582/rmag.mg.24.4.87","url":null,"abstract":"The kinernatics and geometry of some of the basement-involved structures observed in the central Rocky Mountain foreland province have been investigated by means of a series of simple clay models. In these models, a relatively rigid Precambrian crystalline basement is simulated with plasticine oil-base clay (OBC) and the overlying, relatively ductile sedimentary section IS simulated with colored layers of a salt, cornstarch, and water mixture (SCW). In the model described here, a vertical cut and two perpendicular cuts dipping 30\" were made in a block of OBC and lubricated. Horizontal layers of uncut SCW were laid over the cut block of OBC Horizontal compression was applied parallel to the vertical cut so that shortening along one side was greater than along the other side. Shortening was manifest in the differential development of perpendicular thrust-folds which accompanied left-lateral s11p along the buried vertical fault plane. In the overlying, unfaulted SCW layers, a plunge was created on both fold trends, and the anticlinal hinges above OBC thrust locations were deflected sinistrally across the buried wrench fault zone. There are some basic similantries, but also important differences, in the geometry of the deformed clay model and the structure observed in the Bonanza-Zeisman area of the eastern Big Horn basin of Wyoming. A significant component of left slip along a postulated northeast-trending wrench fault zone buried in the basement of the Bonanza-Zeisinan area 1s inferred from the northeastern alignment of sinistral deflections and abrupt terminations of thrust-fold structures which trend perpendicular to the zone Although the numbers of thrust-fold structures developed along either side of the postulated Bonanza-Zeisman wrench fault zone are not equal as in the clay model, the total horizontal shortening measured along either side of the fault line approximately balances. The inferred left-lateral slip on the postulated wrench fault zone 1s thought to be the result of Laramide reactivation of a pre-existing Pre-Cambrian fracture or shear zone","PeriodicalId":101513,"journal":{"name":"Mountain Geologist","volume":"36 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1988-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123984641","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":"Geology of the Precambrian Metamorphic Rocks Along South Hardscrabble Creek, Wet Mountains, Colorado","authors":"J. Noblett","doi":"10.31582/rmag.mg.24.3.67","DOIUrl":"https://doi.org/10.31582/rmag.mg.24.3.67","url":null,"abstract":"Proterozoic metamorphic rocks exposed along South Hardscrabble Creakier typical those in the Wet Mountains on the east side of the Ilse fault, lacking the northeast trending, 1-mr (1 6 km) wavelength folds of rocks to the west They are folded isochronally implying that this IS not a stratigraphic succession, but map units can be described and analyzed Three major units were recognized 1) amphibolite, 2) birotate gneiss, and 3) granitic gneiss Manor rock types include metagabbro and sillimanite-bearing quartzite The amphibolite and metagabbro have compositions suggesting that they originated as tholeiitic basalts The birotate gneiss probably had both shale and greywacke protoliths The mineralogy, textures, and chemistry of the granitic gneisses indicate Igneous origin, probably as late tectonic granitic intrusions of crustal derivation","PeriodicalId":101513,"journal":{"name":"Mountain Geologist","volume":"18 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1987-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115392714","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":"Government Draw Bentonite Beds: A Newly Identified Stratigraphic Marker in the Virgin Creek Member of the Pierre Shale, Central South Dakota","authors":"T. C. Nichols, A. F. Chleborad, D. S. Collins","doi":"10.31582/rmag.mg.24.3.77","DOIUrl":"https://doi.org/10.31582/rmag.mg.24.3.77","url":null,"abstract":"A grouping of four bentonite beds, herein named the Government Draw Bentonite Beds, is identified as a stratigraphic marker within the Virgin Creek Member of the Pierre Shale. The beds are found west of Pierre, South Dakota, over an area of at least 130 mi/sup 2/ where no other markers within the Virgin Creek Member have been identified. In this area, the Government Draw is a potential tool needed to determine the stratigraphic and structural relationships within the upper part of the Pierre Shale, heretofore little known. A better understanding of structural elements found in the Pierre Shale is needed to unravel the Late Cretaceous and younger geologic history of the area. This is part of a study to characterize Cretaceous shales for subsurface engineering construction undertaken by the US Government to evaluate the feasibility of using shales as a medium for disposal of toxic waste.","PeriodicalId":101513,"journal":{"name":"Mountain Geologist","volume":"7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1987-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132941740","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":"Reactivation of a Cretaceous Thrust Surface by Basin-and-Range Extension, Southwestern Gunnison Plateau, Central Utah","authors":"S. Mattox, M. Weiss","doi":"10.31582/rmag.mg.24.3.55","DOIUrl":"https://doi.org/10.31582/rmag.mg.24.3.55","url":null,"abstract":"Recent work in central Utah has outlined the broader features of the area's thrust geometry. Although individual interpretations differ, most models indicate the region is similar to better understood segments of the Cordilleran thrust belt. Poor and limited seismic data and the paucity of drill-hole information has hindered the investigation of the south- west quadrant of the Gunnison Plateau. Detailed surface mapping of a centrally located quadrangle has provided strati- graphic evidence for a previously unrecognized Cretaceous-Paleocene thrust fault. The present expression of the thrust surface requires reactivation with a reverse sense of motion during Tertiary extension. Drastic facies changes in the Late Cretaceous-Early Paleocene North Horn Formation occur over a short distance - essentially across a fault. The gray, eastern lithofacies is dominated by massive conglomerate, sandstone, and oncolitic limestone. Maximum thickness is 253 m (830 ft). Clast composition indicates a local source/positive area of Cretaceous lndianola Group. The thinner 38 m (126 ft), red, western lithofacies consists of pebbly sandstone, sandstone, and mudstone. Reddish brown mudstones and intrac lasts suggest red beds, possibly the Cretaceous Cedar Mountain Formation and/or the Jurassic Twist Gulch Formation and Arapien Shale, as a primary source. After careful consideration of several hypotheses, the only valid conclusion seems to be the presence of thrusted Indianola, creating a topo- graphic barrier between the two separate and unique basins. Two major structural features can be traced to the north, an area of better seismic and drill-hole data. The southern terminus of the Wasatch fault zone, has been interpreted by numerous investigators as eithera reactivated Cretaceous thrust (with a reverse sense of motion) or a high-angle planar Tertiary normal fault. The Escarpment fault, the eastern boundary of a Basin and Range graben, has also been presented in both configurations (listric or high-angle planar). No observations were made to support a listric geometry for the Fayette fault. The Escarpment fault, however, appears to have been active during North Horn time, thrusting lndianola conglomerate into a topographic/structural high. The upper plate underwent a reversed sense of motion in the Tertiary to create the present Chriss/Mellor graben.","PeriodicalId":101513,"journal":{"name":"Mountain Geologist","volume":"121 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1987-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122333491","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 Goshen Hole Uplift: A Brief Review of its History and Exploration Potential","authors":"T. Ahlbrandt, W. Groen","doi":"10.31582/rmag.mg.24.2.33","DOIUrl":"https://doi.org/10.31582/rmag.mg.24.2.33","url":null,"abstract":"The Goshen Hole uplift 1s a little recognized and sparsely explored feature in the northern end of the Denver Julesburg basin We believe there is excellent hydrocarbon potential on the uplift principally In Cretaceous (Hygiene, Niobrara, Wall Creek, Muddy, Dakota). Jurassic (Canyon Springs), Permian and Pennsylvanian objectives. There are diverse stratigraphic anomalres observed on seismic data in these horizons as well as numerous paleo structures. Basement tests are approximately in the 10.000 to 11,000 ft (3.048 - 3.353 m) range. The uplift has had recurrent movement since the Pennsylvanian; however a period of uplifting occurred in the Upper Cretaceous beginning by at least early Campanian time with intermit- tent uplift rn the Cenozoic. There are numerous subsurface shows and source beds in Paleozoic and Mesozoic horizons and oil seeps on the uplift which enhance the exploitations potential of this area","PeriodicalId":101513,"journal":{"name":"Mountain Geologist","volume":"166 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1987-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122422126","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":"Alkali Metasomatism and Fossil Geothermal Activity: Wah Wah Springs Tuff, Utah","authors":"R. Nusbaum, S. Gant","doi":"10.31582/rmag.mg.24.1.26","DOIUrl":"https://doi.org/10.31582/rmag.mg.24.1.26","url":null,"abstract":"Variable degrees of widespread alkali metasomatism have been detected within Wah Wah Springs Tuff samples collected in southwestern Utah. Highly altered samples show (1) strong periodic enrichment trends for alkali metals (except Na) at the expense of alkaline earth elements (except Ba), and (2) complete to partial replacement of andesine phenocrysts by K-feldspar: Mildly altered samples show (1) similar but less extreme enrichments and depletions compared to highly altered samples, and (2) no megascopic evidence of alteration. Cs is the most sensitive of the elements enriched by the alteration, followed by Rb and K20. Greater tendency toward fixation of heavy alkalis at low temperatures accompanying the addition of K-feldspar and the reduction of andesine explains. relative alteration trends. The lack of prvximal mineralization and widespread nature of alkali metasomatism associated with minor pmpylitic alteration suggests fossil geothermal activity in this part of Utah.","PeriodicalId":101513,"journal":{"name":"Mountain Geologist","volume":"10 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1987-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115192377","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":"Deltaic Deposits of the Upper Cretaceous Dad Sandstone Member of the Lewis Shale, South-Central Wyoming","authors":"R. Perman","doi":"10.31582/rmag.mg.24.1.10","DOIUrl":"https://doi.org/10.31582/rmag.mg.24.1.10","url":null,"abstract":"The Dad Sandstone Member is a progmding unit of sandstone and minor mudstone that sepamtes upper and lower shale members of the Lewis Shale. Outcrops of this Maestrichtian-age unit have been examined in southcentml W)vming along the eastern margin of the Great Divide basin north of Rawlins, and in the Hanna basin to the east. These outcmps form two groups with very different chamcteristics, including thickness of sendstone and interbedded mudstone units, sedimen- tary structures, and fossils. In the western part of the area studied, the Dad Sandstone is interpreted to represent progmda- tion in the lower delta-fmnt reglon of the Sheridan delta that existed to the northwest. In the eastern portion of the study area the Dad Sandstone probably represents upper shorefece iacies of interdistributary barrier bars. These deposits mey be related to either the Sheridan delta to the north, or a north-trending uplift to the south. The Dad Sendstone in the eastern part of the study area is probably slightly younger than In the western part of the study area.","PeriodicalId":101513,"journal":{"name":"Mountain Geologist","volume":"51 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1987-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134265545","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}