Formation Pressure Patterns in Cretaceous Viking Formation, Alberta

850 Association Round Table beds within correlative uppermost Devonian rocks HARPER, J. D., Shell Development Co., Exploration along the Cordilleran miogeosyncline. They are present and Production Research Center, Houston, Tex. in the Exshaw Formation of southwestern Alberta, Sappington Member of Three Forks Formation TRENDS OF FAUNAI. MoRPHoroGic VARIATION AND throughout western Montana, lower part of Leatham, THEIR ENVIRONMENTAL SIGNIFICANCH; KEY TO PAI- Formation of northern Utah, and middle part of Pilot EOECOLOGic ANALYSIS Shale of west-central Utah and southeastern Nevada. Analysis of trends of morphologic variation within These phyllopod bivalve crustaceans or clam shrimp faunai assemblages is significant for paleoecologic in are found most commonly in greenish-gray and gray terpretation, and complements paleoenvironment in ish-black shales. The shales directly overlie extremely terpretations based on analogy with Holocene sedimen thin discontinuous fish- and conodont-bone beds and tary environments. The Rondout Formation (Late Silu are overlain by carbonate beds that generally contain rian), Hudson Valley, New York, demonstrates the im numerous algal nodules (oncolites). Conchostracans portance of such analysis. also are present in Umestone and in channel siltstone. The Glasco Limestone Member (12 ft) records The associated biota generally comprises inarticulate offshore subtidal deposition. It is overlain and under brachiopods, principally Lingula and Orbiculoidea, or- lain by supratidal mudflats—the Whiteport Dolomite thocone, nautiloid, and goniatite cephalopods, Tasman- (1-7 ft) atid Rosendale Dolomite Members, re iles, and fish fragments, but locally includes abundant spectively. to rare ophiuroids, blastoids, and other pelmatozoans, Within the Glasco, 5 units in vertical sequence from articulate brachiopods, ostracods, conodonts, trilobites, base to top show morphologic variation of halysitids, horn corals, and sponge spicules. The conchostracans coenitids, stromatoporoids, and various algae, coinci are small and thin valved in noncalcareous shale but dent with shallowing: Unit I (1 ft), "amoeboid" stro their size and valve thickness increase relative to higher matoporoids in wackestone matrix; Unit 11 (4 ft), thin, carbonate content of enclosing rocks. The bivalves are laminar stromatoporoids, "head-shaped" halysitids, en flattened in shale but undistorted in carbonate beds; crusting algae, and smafl-diameter branching coenitids open articulated valves are commonly preserved. in packstone and grainstone matrix; Unit 111 (1 ft), A brackish-water environment is suggested for these halysitids change to '"blade" morphology; Unit IV (4 latest Devonian conchostracans. Optimum conditions ft), no halysitids, bloom of larger diameter branching apparently were a muddy bottom, restricted circula coenitids, branching and encrusting algae, and laminar tion, shallow and quiet water, and slow deposition. and "amoeboid" stromatoporoids in packstone and grainstone matrix (rare wackestone); Unit V (2 ft), massive domal stromatoporoids in calcareous shale. HADLEY, DONALD G., U.S. Geol. Survey, Washing Transitions from "heads" (o branches, from "heads" ton, D.C. to "blades," from smaller to larger diameter coenitids, and from encrusting to branching algae arc interpreted PALEOCURRENTS AND ORIGIN OF HURONIAN I.ORRAIN as adaptation to incieased turbulence. Halysitid estab FORMATION, ONTARIO AND QUEBEC lishment and laminar stromatoporoid morphology cor TTie Lorrain Formation crops out in 3 areas between relate with "firm" substrate. A "soft" substrate sup Sault Ste. Marie, Ontario, and Ville-Marie, Quebec— ported "amoeboid" stromatoporoids. A decrease of tur Bruce Mines, Whitefish Falls, and Cobalt. It conform bulence permitted verlica) expansion of stromatopo ably overlies the Gowganda Formation in each area; in roids to domal morphology. the Cobalt area it also locally overlies Archean granite. Paleoecologic interpretations based on single mor The Lorrain is overlain by the Gordon Lake Forma phologic occurrences, as contrasted with trends, must tion. be made with reservation In ascending order, the Lorrain Formation consists of arkose, subarkose, jasper-bearing orthoconglomer- HARRIS, D. G., and A. YOUNG, Esso Production ate, and orthoquartzite. In the Bruce Mines area the Research, Houston, Tex., and H. HAY-ROE, Belco Lorrain is 8,300 ft thick and is divided into 5 members Petroleum Corp., Lima, Pcni (A-E); in the eastern areas the Lorrain is only 5,000 ft thick and is divided into 3 members (lower, middle, FORMATION PRESSURI; PAirrKNS IN CRETACEOUS VIKING and upper). In each area, mineralogic and texlural ma FORMATION, ALBEIMA turity increases upward; grains in immature arkose at Regional potentiometiic maps of the Lower Creta the base are subrounded and 44% feldspar, and grains ceous Viking Formation in central Alberta indicate a in supermature orthoquartzite at the top are well low-pressure area or "sink" centered on the Joftre- rounded and 95-100% quartz. Chronologically, the de- Bentley-Gilby trend of oil fields, with formation waters positional environments suggested are shallow-water in central Alberta flowing into the trend. According to marine, lacustrine, delta fringe, overshelved beach, and integrated geologic and pressure studies, the "sink" ac high-energy beach. tually consists of 6 separate, nearly static, pressure sys Currents flowing south and southeast deposited most tems controlled by the environiriental facies and subse of the sediments; however, in jasper-bearing conglom quent structural deformation. erate of the Bruce Mines area, cross-bedding and peb The Viking reservoirs are interpreted to be lenticular ble composition indicate a 90° variance in transport sandstone bodies deposited as en echelon offshore bars direction, and an additional source on the east. Abun with a NW-SF trend. Postdepositional uplift and subse dant potash feldspar and lack of metamorphic and sed quent erosion have exposed the Viking sandstones at imentary rock fragments in the lower members suggest their lateral extremities; in places, these extremities are a plutonic provenance. Subsequent deposition of jas covered by a thin veneer of permeable glacial deposits. per, chert, and quartz-rich detritus indicates erosion Five of the 6 pressuic systems in the Viking appear to and reworking of Precambrian jaspilites and igneous be controlled by the distribution of these bars and by source rocks similar to those now exposed in the Cana the elevations of outcrops. The sixth system is charac dian shield. terized by pressures 1,200 psi helow hydrostatic pres- Association Round Table 851 sure and by as much as 1,900 psi below the outcrop- sin, and Fort Union lake deposits in the Big Horn ba controlled systems. This system is interpreted to be a sin. The lobate configuration of Fort Union coarse sandstone lens completely enclosed in shale; its pres elastics on the west Hank of the Big Horn basin is very sures were developed by geo-osmosis, as indicated by suggestive of deltaic deposits facies relations, shale analyses, and salinity maps. The osmotic cell in this system consists of the low- HAYES, MILES O., JON C. HOOTHROYD, and AL salinity Viking sandstone and the deeper, high-salinity, BERT C. HINE. Ill, Coastal Research Group, Dept. Mannville sandstone and shale; the semipermeable Geology, Univ. Massachusetts, Amherst, Mass. membrane of the system is the intervening Joli Fou DiAGNOsric PRIMARY SIRI ( I UKES OE F.SIUARINI; SAND shale. Because the Viking sandstone system is isolated BODIES from the outcrop by shale and shaly rocks of very low permeability, the osmotic process produced a marked Estuarine sand bodies assume complex morphologic pressure anomaly. characteristics in response to multidirectional tidal currents and wave action. Studies in 8 New England HAUN, JOHN D., Colorado School of Mines, Golden, estuaries show, however, that the major forms are Colo., and JAMES A. BARLOW, JR., Barlow and repetitive from estuary to estuary and that Ihey display Haun, Casper, Wyo. diagnostic suites of primary structures. Sand accumulation around the seaward margin of LOWER TERIIARY DELIAS AND PETROEEIM, RCHK-I the major inlets takes the foim of ridge-and-runnel sys MOUNTAIN REGION tems and recurved spits attached to the barrier Paleocene and Eocene lacustrine deltas are present beaches, large swash bars ollshore, and submerged ebb- in several Rocky Mountain intermontane basins. Del dominated sand sheets. Wave-generated flow over the taic deposits of the Eocene Green River Formation in intertidal bars creates an abundance of large-scale (up the Red Wash-Raven Ridge area, northeastern Utah, to 20 ft thick) planar cross-beds oriented landward. have been studied intensively. Recognition of the Red Tidal deltiis inside the inlets consist inainly of sand Wash delta is based on distribution of (1) fluviatile flats covered with tlood-oriciited sand waves—>20-ft red and green shale facies (Wasatch Formation), dis wave lengths (A). Margins of the deltas (ebb shields tributary and nearshore sandstone facies, and lacust and ebb spits) contain piedominantly ebb-oriented rine oolitic, ostracodal hmestone facies (Green River niegaripples (\ ;: 2 20 ft) which produce festoon Formation); (2) geographic orientation and spatial di cross-bedding. In places, the deltas are cut by spillover mensions of thick sandstone bodies projecting into the lobes formed by ebb currents. Thus, zones of flood lake beds, indicating positions

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