Browsing by Subject "Ichnology"
Now showing 1 - 2 of 2
Results Per Page
Sort Options
Item Barrier island associated washover fan and flood tidal delta systems: A geomorphologic analysis and proposed classification scheme for modern washover fans and examination of a flood tidal delta complex in the Cretaceous upper McMurray Formation, Alberta, Canada(2013-12) Hudock, Jessica Wager; Wood, Lesli J.; Flaig, Peter PaulA detailed study of modern washover fan (fan) morphologies will clarify common fan geometries, lead to a better model for a “typical” fan, identify the preservation potential and probable geometries of fan facies in subsurface datasets and outcrops, and ultimately improve hydrocarbon recovery in barrier island reservoir systems. This study uses satellite imagery to conduct a spatial analysis of 118 modern fans to quantify geomorphologic attributes of fans. A new classification scheme for fans is proposed that refines the current fan model, dividing fans into channelized and non-channelized fans. Channelized fans are subdivided according to the location of primary deposition: barrier depo-center or lagoonal depo-center. Non-channelized fans are subdivided based on morphology: dissipative, lobate, or apron-sourced. Quantitative cross-plots of morphologic relationships are analyzed to define trends in fan morphologies. The most common type of fan encountered in our study is a non-channelized, line-sourced, lobate washover fan with an area of less than 1 km2 that is fully contained on a barrier and exhibits no subaqueous deposition in back-barrier waters. The Lower Cretaceous McMurray Formation is the primary reservoir of the Athabasca Oil Sands in Alberta, Canada. The upper McMurray is commonly interpreted as deposits of embayed coastal systems. Our location is in an under-studied area located 80 km northwest of Fort McMurray. Lateral and vertical facies changes, sedimentary structures, key surfaces, trace fossils, and bitumen saturation were documented in eight cores located along a 20 km transect situated paleo-landward of a Devonian paleo-high acting as a bedrock-barrier. Our data indicate that a flood tidal delta complex prograded landward into a back-barrier embayment through the stable, bedrock-controlled inlet. This system overlies middle McMurray fluvial sands and Devonian basement and was transgressed by marine waters prior to deposition of the overlying Wabiskaw Formation. Flood tidal delta sandbodies are bitumen saturated and therefore make good reservoirs; however, heavily bioturbated tidal flats can act as a barrier to flow where they encase flood tidal deltas, as encased sands were devoid of bitumen. This complex coastal paleogeography produced back-barrier deposits that contain a slightly more diverse, marine trace fossil assemblage than might otherwise be expected.Item Comparative paleoenvironmental and architectural analyses of the Anchor Mine Tongue to Upper Sego interval along the Book Cliffs of Utah and the Rangely Anticline of Colorado(2016-08) Jones, Rebecca Helen; Fisher, W. L. (William Lawrence), 1932-; Flaig, Peter Paul; Kerans, CharlesA recent, revised regional sequence stratigraphic correlation indicates that outcrop belts along the Rangely Anticline, Colorado contains strata that correlate with the Anchor Mine Tongue and upper Sego of the Book Cliffs, Utah. A detailed sedimentologic and ichnologic investigation of the Anchor Mine Tongue and upper Sego (Campanian) equivalent strata exposed the Rangely Anticline in the Piceance Creek Basin of Colorado revealed that these deposits record the evolution of a mixed fluvio-tidal deltaic system with a delta front significantly modified by tides. This system prograded over lower Sego tidal bars. Predominant structures that support this interpretation include combined flow ripples, trough cross-stratification, low-angle planar-lamination, mud drapes, mud rip-up clasts, mud balls, and trace fossils within sands that are interbedded with finer-grained bioturbated sediments. Ichnology was utilized to refine paleoenvironmental interpretations, and to distinguish between: tidally modified distal and proximal delta fronts and river-dominated deltas; subaqueous tidal channels and distributary channels; interdistributary bays and tidal flats; and marine mudstones and mud-rich paleosols. The Anchor Mine Tongue and upper Sego stratigraphy that is exposed along the Book Cliffs in the Uinta and Piceance Creek was also investigated using a combined sedimentologic and ichnologic approach. Deposits record a marine transgression followed by renewed progradation of tide-dominated deltas with wave-influence along the distal delta front. Paleoenvironments were similar to those of the Rangely area with the addition of marine shelf, wave-modified proximal prodelta, and tidally influenced, wave-modified distal delta front in the Book Cliffs region. The Anchor Mine Tongue and upper Sego in the Book Cliffs preserves the proximal and distal expressions of tide-dominated systems. The Anchor Mine Tongue and the upper Sego both along the Rangely Anticline and along the Book Cliffs are compared-contrasted. Deposits along the Rangely Anticline exhibit more fluvial-flood dominance than deposits along the Book Cliffs. The Rangely stratigraphy represents a mixed fluvio-tidal system whereas the Book Cliffs stratigraphy is tide-dominated. The distribution and variation of paleoenvironments supports a northwest-southwest trending shoreline during the Campanian.