Abstract Dolomudstones of the Pekisko Formation in western Canada form small but important oil and gas reservoirs. The reservoirs are irregularly shaped bodies 1 km or so wide and commonly 5–8 m thick. Porosity development within the dolomudstones is a complex function of sedimentation, early facies-selective dolomitization and later telogenetic leaching of calcareous components. The carbonate sediment precursor of the dolomudstone, interpreted from relict textures preserved in chert nodules, was a microwackestone with abundant silt-sized skeletal fragments. Dolomudstone reservoirs are comprised of dolomudstones, calcareous dolomudstones, and subordinate interbedded dolowackestones and dolograinstones. Some dolomudstone reservoirs are contained entirely within grainstones. Others are capped by tight fenestral lime mudstone that has been dolomitized locally. Dolomitization has been most intense within the centres of these reservoirs, and dolomudstones grade laterally into calcareous dolomudstones. The association of facies indicates that microwackestones were deposited in subtidal intershoal and lagoonal environments on an inner ramp. Grainstone shoals provided a broad barrier that absorbed wave energy seaward of the lagoon. Fenestral lime mudstones accumulated in peritidal environments in restricted areas of the inner ramp, landward of the lagoon. Dolomitization is interpreted to have been early and selective to the microwackestone facies because it retained permeability or was reactive during early burial. Dolomitizing fluids were most probably derived from overlying formations and made their way downwards through spatially separated conduits. The Pekisko Formation was exposed and sculptured at several Jurassic-Early Cretaceous unconformities. During these times, sandstones and shales were deposited in solution cavities developed within the dolomudstones. Concomitant leaching of calcite increased porosity of the dolomudstone reservoirs.
Research Article| March 01, 2004 Paleozoic stromatactis and zebra carbonate mud-mounds: Global abundance and paleogeographic distribution Federico F. Krause; Federico F. Krause 1Department of Geology and Geophysics, University of Calgary, Calgary, Alberta T2N 1N4, Canada Search for other works by this author on: GSW Google Scholar Christopher R. Scotese; Christopher R. Scotese 2Department of Geology, University of Texas at Arlington, Arlington, Texas 76019-0049, USA Search for other works by this author on: GSW Google Scholar Carlos Nieto; Carlos Nieto 3Department of Geology and Geophysics, University of Calgary, Calgary, Alberta T2N 1N4, Canada Search for other works by this author on: GSW Google Scholar Selim G. Sayegh; Selim G. Sayegh 4Energy Branch, Saskatchewan Research Council, Regina, Saskatchewan S4S 7J7, Canada Search for other works by this author on: GSW Google Scholar John C. Hopkins; John C. Hopkins 5Department of Geology and Geophysics, University of Calgary, Calgary, Alberta T2N 1N4, Canada Search for other works by this author on: GSW Google Scholar Rudolf O. Meyer Rudolf O. Meyer 6Department of Earth Sciences, Memorial University Newfoundland, St. John's, Newfoundland A1B 3X5, Canada Search for other works by this author on: GSW Google Scholar Author and Article Information Federico F. Krause 1Department of Geology and Geophysics, University of Calgary, Calgary, Alberta T2N 1N4, Canada Christopher R. Scotese 2Department of Geology, University of Texas at Arlington, Arlington, Texas 76019-0049, USA Carlos Nieto 3Department of Geology and Geophysics, University of Calgary, Calgary, Alberta T2N 1N4, Canada Selim G. Sayegh 4Energy Branch, Saskatchewan Research Council, Regina, Saskatchewan S4S 7J7, Canada John C. Hopkins 5Department of Geology and Geophysics, University of Calgary, Calgary, Alberta T2N 1N4, Canada Rudolf O. Meyer 6Department of Earth Sciences, Memorial University Newfoundland, St. John's, Newfoundland A1B 3X5, Canada Publisher: Geological Society of America Received: 30 Jul 2003 Revision Received: 14 Oct 2003 Accepted: 18 Oct 2003 First Online: 09 Mar 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (2004) 32 (3): 181–184. https://doi.org/10.1130/G20077.1 Article history Received: 30 Jul 2003 Revision Received: 14 Oct 2003 Accepted: 18 Oct 2003 First Online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation Federico F. Krause, Christopher R. Scotese, Carlos Nieto, Selim G. Sayegh, John C. Hopkins, Rudolf O. Meyer; Paleozoic stromatactis and zebra carbonate mud-mounds: Global abundance and paleogeographic distribution. Geology 2004;; 32 (3): 181–184. doi: https://doi.org/10.1130/G20077.1 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 SocietyGeology Search Advanced Search Abstract Carbonate mud-mounds with zebra and stromatactis structures are present in every Paleozoic system and series, but are more common in Devonian and Carboniferous deposits, reaching their acme in Mississippian System (lower Carboniferous) rocks. Global distributions illustrate that mud-mounds spanned the planet ranging from tropical to polar circles. Such a wide latitudinal span signifies that they not only grew in and occupied warm depositional environments, but also in settings where oceanic waters were cold and seasonally light limited. Moreover, their proliferation during the Devonian and Carboniferous was at a time when planet-wide climatic ice-house conditions are thought to have prevailed. Mud-mounds, therefore, may also be products of cool and cold-water carbonate sedimentation. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.
The Glauconitic member in Badger, Little Bow, Retlaw, and Turin fields is an unconformity bounded sequence that formed on an ancient coastal plain in response to relative sea level fluctuations. The member consists of valley-fill and inter-valley strata. Valley-fill sandstone bodies are thick elongate pods that formed from inner estuarine bars when sedimentation was laterally confined between valley margins. Inter-valley sandstone bodies are thin discontinuous sheets that accumulated during highstands when outer estuarine embayments covered interfluvial areas adjacent to associated valleys. Numerous oil pools are stratigraphically trapped within quartzose sandstones in valley-fill and inter-valley strata of the Glauconitic member in the study area. Common updip seals for these reservoirs are (1) intra-sequence facies changes from sandstone to shale, and (2) low-permeability lithic sandstones that fill the cross-cutting paleovalleys of a younger sequence. Traps associated with many valley-fill pools are enhanced by differential-compaction anticlines. Several oil pools in the study area are hosted by discrete quartzose sandstone bodies that lie beneath a valley filled with low-permeability lithic sandstone. These quartzose sandstone bodies are interpreted to be remnants of older Glauconitic deposits that escaped erosion when a younger valley incised into, and followed the trend of, one or more older Glauconitic valleys.
ABSTRACT Three large channels of the lower Kootenai Formation are exposed in the walls of the Missouri River valley east of Great Falls, Montana. Although the channels occur in two different stratigraphic units, they have several features in common. Each channel is contained within crevasse and bay-fill sequences, but the contacts between channel-fill deposits and laterally adjacent strata are erosional. The channels have a broad U-shape, range up to 300 m wide and 35 m deep, and exhibit a distinctive style of fill. Channel-filling occurred in increments by accretion from the bottom up and sides in, to form a concave layering which is more or less symmetrical about the axis of each channel. Lithology of the fill of each channel is quite different, however, and ranges from mudstone, to interbed ed sandstone and mudstone, to sandstone. The channels are interpreted as superimposed distributaries formed by avulsion when the locus of sedimentation shifted from one lobe to another. The lithology of the channel-fill deposits appears to be a function of the abandonment rate. A mudstone-filled channel results where abandonment is rapid, as is the case with upstream diversion of a trunk river system. Sandstone and mixed sandstone-mudstone fills predominate where a distributary is progressively abandoned, for example, where the discharge is diverted into an alternately favored distributary. Superimposed channels are difficult to map in the subsurface by geologic means. They cut across the trend of adjacent facies, and so their presence cannot be predicted from analysis of the containing strata.
Research Article| June 01, 1994 Tectonic wedging beneath the Rocky Mountain foreland basin, Alberta, Canada Donald C. Lawton; Donald C. Lawton 1Department of Geology and Geophysics, University of Calgary, Calgary, Alberta T2N 1N4, Canada Search for other works by this author on: GSW Google Scholar Deborah A. Spratt; Deborah A. Spratt 1Department of Geology and Geophysics, University of Calgary, Calgary, Alberta T2N 1N4, Canada Search for other works by this author on: GSW Google Scholar John C. Hopkins John C. Hopkins 1Department of Geology and Geophysics, University of Calgary, Calgary, Alberta T2N 1N4, Canada Search for other works by this author on: GSW Google Scholar Author and Article Information Donald C. Lawton 1Department of Geology and Geophysics, University of Calgary, Calgary, Alberta T2N 1N4, Canada Deborah A. Spratt 1Department of Geology and Geophysics, University of Calgary, Calgary, Alberta T2N 1N4, Canada John C. Hopkins 1Department of Geology and Geophysics, University of Calgary, Calgary, Alberta T2N 1N4, Canada Publisher: Geological Society of America First Online: 02 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (1994) 22 (6): 519–522. https://doi.org/10.1130/0091-7613(1994)022<0519:TWBTRM>2.3.CO;2 Article history First Online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Donald C. Lawton, Deborah A. Spratt, John C. Hopkins; Tectonic wedging beneath the Rocky Mountain foreland basin, Alberta, Canada. Geology 1994;; 22 (6): 519–522. doi: https://doi.org/10.1130/0091-7613(1994)022<0519:TWBTRM>2.3.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 SocietyGeology Search Advanced Search Abstract High-quality seismic reflection data reveal the geometry of a blind, thinly tapered wedge of allochthonous rocks inserted into autochthonous foreland basin strata for >8 km east of the previously recognized deformation front (triangle zone) of the Canadian Rocky Mountain foothills west of Calgary, Alberta. Upper and lower detachment surfaces have been identified as boundaries between continuous and discontinuous reflection patterns over the length of the wedge. Coherent reflections above the upper and below the lower detachment show that strata outside the wedge are essentially undeformed. The upper detachment is parallel to bedding for at least 7 km, with a dip that decreases gradually from west to east. At its distal limit, the upper detachment lies 350 m above the lower detachment and does not merge with it. The internal reflection geometry of the wedge changes with position. We interpret the thickest part of the wedge to be dominated by thrust slices up to 500 m thick, whereas the toe of the wedge is folded and faulted internally. 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.
Breccia deposited seaward of the margins of Miette and Ancient Wall buildups Upper Devonian of Alberta records synsedimentary submarine cementation of carbonate sands The size shape and composition of breccia clasts indicates that their source rocks were differentially cemented nodular thinly bedded carbonate sands deposited high on the foreslopes close to the margins of the buildups Downslope movement of differentially cemented carbonate sand sequences mixed nodules with uncemented carbonate sands and resulted in deposition of breccia beds The breccia was transported downslope by hybrid sediment gravity flows in which upward movement of fluids grain grain interactions and possibly fluid turbulence supported the clasts Increased pore pressures necessary for initiating such flows on low slopes were the result of metastable packing of sand grains in thinly bedded sequences and or overriding currents carrying material from the buildups Rapid dissipation of excess pore pressures coupled with low slopes did not allow sustained flow and as a consequence deposition of the breccias occurred within a few kilometers of the buildups Carbonate breccia formed by differential submarine cementation and downslope displacement of carbonate sands has not previously been described One important facet of its origin is that it does not record periods of abrasional erosion of the buildups but formed at times when rate of sediment supply to the foreslope was relatively high
