Stratigraphy of Gartra Formation (Triassic), Uinta Mountain Area, Utah and Colorado
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Abstract In the Uinta Mountain area, the Gartra Formation (Middle? Triassic) unconformably overlies the Moenkopi Formation on the east and the Ankareh Formation on the west, and interfingers with the overlying purple unit of the Popo Agie Formation (Late Triassic). Based on lithology, sedimentary structures, and weathering characteristics, the Gartra is informally divided into three subunits. The lower subunit is characteristically conglomeratic, poorly sorted, massive, and poorly bedded sandstone. The middle subunit is characterized by finer-grained sandstone and by dominant planar and trough cross-stratification. The upper subunit is finer grained than either of the subjacent subunits, consisting of claystone, siltstone, and very fine to medium sandstone. Horizontal and small-scale cross-stratification are characteristic of the upper subunit. The Gartra probably was deposited by a series of west-northwest flowing streams on a broad alluvial plain. Detritus was derived from plutonic, sedimentary, and gneiss-schist terranes on the east and southeast (Ancestral Rockies and Uncompahgre uplift). Gradually decreasing velocity and turbulence of stream currents were responsible for the fining-upward sequences.Keywords:
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Alphebian sedimentary rocks of the Tamarack River Formation rest unconformably on the Knob Lake Group in the south-central portion of the Labrador Trough. The formation appears to consist of two transgressive-regressive cycles. The first cycle, present in Member A, consists of subtidal siltstone, which grades upward into a mixed siliciclastic-carbonate unit of shallow subtidal and intertidal origin. The second cycle, recorded by members B and C, is composed of subtidal siltstone which passes upward into the intertidal and fluvial sandstone. Detritus of member A was derived from the north, whereas the provenance of member C was the Superior Province to the west. The formation may be part of the third Aphebian miogeoclinal sequence which developed in the Labrador Trough. The first and second sequences are recorded by the Knob Lake Group. The northern Labrador Trough may contain third sequence strata correlative to the Tamarack River Formation. -- The Paleohelikian Sims Formation rests unconformably on deformed Aphebian strata and consists of a lower unit of terrestrial redbeds and an upper unit of fluvial to shallow-marine quartzarenite. The relatively thin terrestrial redbed unit is composed of three facies, a talus-slope breccia, a pebbly braided-river conglomerate and a sandy braided-river deposit. These facies grade upward into a thick, tabular quartzarenite unit composed of fluvial sandstone, beach conglomerate, and nearshore to shallow-marine sandstone. Throughout its deposition the formation progressively onlapped from west to east and derived its detritus from an uplifted area to the east. The formation may represent post-Hudsonian molasse, and is possibly correlative with the lithologically similar but undated Sakami Formation of northern Quebec. -- Both the Tamarack River and Sims Formations were intruded by tholeiitic dikes and sills of the Elsonian (1.4Ga) Shabogamo Intrusive Suite. Paleomagnetic samples from the suite yield a virtual paleopole position at 3.97°E, 3.4°S with dp = 5.8° and dm = 11.0°, which is similar to the antipole of the nearby Elsonian Michikamau Intrusion.
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Research Article| November 01, 1972 Depositional History of the Coal-Bearing Upper Jurassic-Lower Cretaceous Kootenay Formation, Southern Rocky Mountains, Canada LUBOMIR JANSA LUBOMIR JANSA Eastern Petroleum Geology Section, Geological Survey of Canada, Bedford Oceanographic Institute, Dartmouth, Nova Scotia Search for other works by this author on: GSW Google Scholar Author and Article Information LUBOMIR JANSA Eastern Petroleum Geology Section, Geological Survey of Canada, Bedford Oceanographic Institute, Dartmouth, Nova Scotia Publisher: Geological Society of America Received: 06 Aug 1971 Revision Received: 31 Mar 1972 First Online: 02 Mar 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Copyright © 1972, The Geological Society of America, Inc. Copyright is not claimed on any material prepared by U.S. government employees within the scope of their employment. GSA Bulletin (1972) 83 (11): 3199–3222. https://doi.org/10.1130/0016-7606(1972)83[3199:DHOTCU]2.0.CO;2 Article history Received: 06 Aug 1971 Revision Received: 31 Mar 1972 First Online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation LUBOMIR JANSA; Depositional History of the Coal-Bearing Upper Jurassic-Lower Cretaceous Kootenay Formation, Southern Rocky Mountains, Canada. GSA Bulletin 1972;; 83 (11): 3199–3222. doi: https://doi.org/10.1130/0016-7606(1972)83[3199:DHOTCU]2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract The coal-bearing Kootenay Formation of Late Jurassic-Early Cretaceous age in Alberta and British Columbia is a classic example of sedimentary sequences built by delta progradation. The formation is composed of 3,500 ft of cyclicly alternating sandstone, shale, and coal, with a few conglomerate beds. The sandstone beds are poorly to moderately sorted, fine- to medium-grained lithic graywacke and proto-quarzite. Shale is of illitic composition with minor amounts of kaolinite. These Upper Jurassic-Lower Cretaceous sediments were derived mainly from the sedimentary-rock terrains located in the Purcell Mountains and the Shuswap Complex. Direction of transportation was to the northeast.Deposition of the Kootenay Formation was initiated by epeirogenic uplift of the source area in Late Jurassic time. Terrigenous sediments were initially deposited on a low-lying coastal plain, which advanced seaward by accretion processes into the shallow sea of the eastern Canadian Cordillera miogeosyncline. In the vertical section, the siltstone and mudstone beds of the open marine environment grade upward into transitional prodelta facies of the Fernie Formation composed of sandstones and siltstones containing the trace fossil Thalassinoides. The prodelta deposits in turn grade upward into delta front sheet sand containing the trace fossil Rhizocorallium. The overlying well-sorted and highly burrowed sandstone of a barrier bar and "misch" tidal flats contains the trace fossil Arenicolites, and grades upward into lower delta plain deposits. These are composed of sandstone beds ranging up to 50 ft in thickness and represent channel fill and point bars of meandering distributaries, laterally interfingered into interdistributary sequences. Coal, as much as 30 ft thick formed as peat in coastal marshes and in fresh-water swamps of interdistributary basins of the lower delta plain. Within the upper delta plain, thick sandstone beds are more common, and coal formed in fresh-water swamps of the flood basins. The delta-plain sediments grade upward into alluvial plain deposits characterized by the occurrence of sheet form beds of conglomerate, lithic sandstone, siltstone and silty shale, and decreased thickness of individual cyclothems. Increased frequency in alternation of rock units is explained by the increase of channel instability and tendency of river channels to form a braided channel system. This system provided unfavorable conditions for coal development.Uplifting of the depositional area in Neo-comian time terminated sedimentation and initiated denudation of the previously deposited sediments. During additional strong uplifting of the inland area, the rejuvenated piedmont-plain deposits represented by conglomerate beds of the Cadomin Formation were spread over the eroded surface of the Kootenay Formation.This study demonstrates the use of sedimentological studies as a tool for exploration and evaluation of coal basins. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.
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Nova scotia
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Abstract The Paleocene Dark Canyon sequence of dominantly matrix-supported, quartz-pebble conglomerate, conglomeratic sandstone, and sandstone forms the basal part of the Wasatch Formation in the southeasternmost part of the Uinta Basin. This sequence marks the first Tertiary depositional event after a long period of nondeposition and erosion during Maestrichtian and early to middle(?) Paleocene time and prior to rapid subsidence in late Paleocene through much of Eocene time. The predominance of chert and quartzite pebbles, the Paleozoic silicified limestone pebbles, the sandstone mineralogy, and the dominant northwest paleocurrent directions all indicate that sediment was derived mainly from Paleozoic and Mesozoic sedimentary rocks eroded from rising Laramide uplifts to the south and southeast. Massive to crudely horizontally stratified conglomerate and local thin interbeds of horizontally stratified sandstone compose the lower part of the Dark Canyon sequence. The size and abundance of pebbles decreases upward, and trough cross-stratified and horizontally stratified sandstone and pebbly sandstone are dominant in the upper part. Sedimentary structures in and geometries of the depositional units that compose this sequence indicate formation within relatively shallow, rapidly shifting channels in braided rivers that flowed on a medial to distal braidplain. The decrease in grain size vertically and from west to east in the Dark Canyon sequence indicates decreasing flow strength through time and in that direction. The San Rafael uplift appears to have restricted the western extent of deposition. Over the western flank of the Douglas Creek arch, the rivers flowed to the northeast. Both local erosion of the unit in this area and the time-transgressive, west to east onlapping of overlying beds of the Wasatch Formation over the arch suggests post-Dark Canyon movement of this structure.
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Marine transgression
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Abstract Braided streams within a humid alluvial fan network largely deposited the Cretaceous through early Tertiary Currant Creek Formation in the northwestern Uinta Basin, northeast Utah. These fans extended into the north-central Utah foreland basin from the tectonically active Sevier orogenic belt on the west. The synorogenic conglomerate ranges in type from boulder-sized clast-supported strata to pebble-and granule-sized matrix-supported conglomerate. The interbedded sandstone increases in textural maturity with distance from source areas. The sandstone composition ranges from quartz arenite to lithic arenite. Conglomerate and sandstone that formed as longitudinal bars, channel fills or sieve deposits characterize the proximal fan facies. Distal facies consist principally of sandstone and finer grained clastic strata that were deposited within channels or overbank areas.
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Three major lithogenetic sequences of regional extent are recognized in the Upper Triassic Series of the Colorado Plateau region. The sequences, which correspond only partly with named formations, are useful in describing the gross lithologic character and the origin of the Upper Triassic Series. The lowest of the three, the bentonitic sequence, consists of variegated bentonitic claystone and clayey sandstone and thin widespread sandstone and conglomerate units. The sediment in the sequence was derived predominantly from a volcanic source area south of the Colorado Plateau, the Mogollon highland, and was deposited in streams, on floodplains, and in lakes. The overlying redbed sequence consists of reddish-brown or reddish-orange, horizontally stratified siltstone and minor amounts of limestone and sandstone. The sediments were predominantly quiet-water deposits, probably lacustrine, derived from several source areas, the most important of which may have been the Uncompahgre and Front Range highlands of Colorado. The next overlying sequence consists of light-brown, fine- to medium-grained, conspicuously cross-stratified sandstone. It is considered to be of eolian origin; the sediment probably was derived from reworking of upwind arenaceous sedimentary units on the northwest.
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The Maastrichtian age Brown Mountain Sandstone Member of the Panoche Formation is exposed in the southeastern Diablo Range along the west side of the San Joaquin Valley, California. The Brown Mountain Sandstone is one of many locally named, discontinuous sandstones that are stratigraphically near the top of the Mesozoic Great Valley Group, which crops out nearly continuously along the western edge of the San Joaquin and Sacramento Valleys. Sandstones with correlative foraminiferal assemblages and depositional facies include the gas-bearing upper Tracy submarine fan sandstones of the Sacramento Valley.
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Abstract The Death Valley area of eastern California and southern Nevada has been highly influential in the development of ideas about extreme crustal extension. One of the tightest constraints on Death Valley extension is apparently provided by clasts in inferred alluvial-fan deposits of the Eagle Mountain Formation (~ 15–11 Ma) and their source in the Hunter Mountain batholith, now located > 100 km from some of the deposits. Because alluvial fans are usually less than 10–20 km in radius, the remaining separation has been interpreted as tectonic. New research reported here suggests that the Eagle Mountain Formation at its type location was deposited in a fluvial–lacustrine setting, and provides no constraint on either the magnitude or the direction of tectonic transport and/or crustal extension. Confidence in palinspastic reconstruction thus depends on resolving ambiguities in the correlation of pre-extensional markers or on the recognition of demonstrably proximal facies tectonically distributed across the region. The succession at Eagle Mountain comprises (1) diffusely stratified monolithologic carbonate breccia and sandstone (~ 140 m) onlapping Cambrian carbonate rocks at an unconformity with ~ 110–140 m of relief (fluvial or fluvially influenced); (2) ~ 10 m of tabular-bedded siltstone, diamictite, and sandstone (lacustrine); (3) cross-stratified and channelized sandstone and polymict conglomerate bearing Hunter Mountain clasts, with minor siltstone and carbonate (~ 110 m; mostly fluvial); and (4) tabular-bedded sandstone, siltstone, and minor carbonate (~ 140 m; mostly lacustrine). Eight prominent stratigraphic discontinuities mapped within the third interval are characterized by up to 15 m of local erosional relief, and by abrupt upward coarsening from siltstone or carbonate to conglomerate or sandstone. A fluvial interpretation for the same critical part of the succession is based upon the existence of the mapped surfaces; the ubiquitous development of channels, trough cross-stratification, and upward fining trends (particularly between the mapped surfaces); and the abundance of well rounded clasts in conglomerate. Paleocurrents are generally directed between southward and eastward, although with considerable dispersion, and they shift from approximately southward or southeastward in the mostly fluvial deposits to approximately eastward in the upper lacustrine interval. An unusual feature of the Eagle Mountain Formation at Eagle Mountain is the presence of five crosscutting conglomerate bodies, interpreted as vertically infilled fissures of tectonic origin. Numerous normal, reversed normal, and oblique-slip faults with up to 34 m of stratigraphic separation are thought to postdate sedimentation and tilting of the Eagle Mountain Formation after ~ 11 Ma.
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ABSTRACT Sedimentologic study of the Simmler Formation and the transition to the conformably overlying Vaqueros Formation was undertaken in order to reconstruct the Oligocene history and paleogeography of this part of the southern Coast Ranges of California. The Simmler, of Oligocene and possible latest Eocene age, consists of a sandstone facies in the Caliente Range, and a conglomerate facies to the west, southwest, and southeast around the margins of the basin. The sandstone facies is composed of greenish-gray sandstone and red and green claystone or mudstone in fining-upward cycles that average 2.5 m thick. The conglomerate facies consists of reddish muddy conglomerate to pebbly mudstone and interbedded sandstone. Transgressive marine strata overlying the Simmler, and laterally equivalent t its uppermost part, are included in the Vaqueros Formation of late Oligocene to early Miocene age. The lowest Vaqueros sediments are nearshore or strandline sandstones that are overlain, in the Caliente Range, by deep basinal siltstones. The sandstone facies of the Simmler is interpreted as an alluvial plain depositional complex formed by through-flowing streams; the conglomerate facies represents alluvial fan deposits rimming the alluvial plain. The streams were probably of low sinuosity and of small to moderate size. Petrographic and paleocurrent data indicate that the Simmler Formation and the overlying Vaqueros Formation were derived from the same source terranes and that the sediments were transported in the same general direction. The conglomerate facies of the Simmler provides evidence of late Oligocene activity on the Nacimiento, Ozena, and Blue Rock faults; the Chimineas-Russell fault was apparently not active at this time. Although this study provides no direct evidence bearing on offsets along the San Andreas fault, sedimentologic evidence from the Simmler tends to support the hypothesis that the San Andreas fault did not come into existence in this area until after the Oligocene. The most significant tectonic event during the late Oligocene in this area was the inception of basin formation evidenced by the foundering of the Caliente Range area in the late Zemorrian that apparently resulted from interaction of the Pacific and North American plates.
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