Within the middle McMurray exposures along the Steepbank River (Steepbank River Outcrops 3 and 4), nine recognized facies can be divided into three genetically related groups: sand-dominated facies, inclined heterolithic stratification (IHS) facies and mixed heterolithic facies. Together, these facies are interpreted to represent a fluvially dominated, tidally influenced point bar that experienced strong seasonal variation in river discharge. Annual fluctuations between river-flood stage and low-flow stage are responsible for the deposition of fluvially dominated sand beds alternating with brackish, tidally influenced mud beds that cover the point-bar surface as members of the various IHS facies. The dichotomy of fluvially dominated sand deposition and brackish-water ichnology of the mud beds represents the annual migration in position of the tidal and salinity nodes caused by fluctuations in fluvial discharge.
Recognition of metre-scale cycles (MSCs) of alternating sandier and muddier intervals within the IHS facies imply that decadal climate cycles, likely caused by fluctuations in ocean and/or solar dynamics, influenced point-bar deposition. These MSC packages are defined by an upward decrease in sand-bed thickness, an upward increase in mud-bed frequency, and an upward increase in bioturbation intensity, all occurring on a metre scale. MSCs are an important architectural element of these large-scale tidal-fluvial point bars because they are predictable, repeatable and continuous around the point bar.
Analysis of paleocurrents relative to inclined-heterolithic-stratification bedding planes indicates that bend-flow modifications (BFMs) were effective in redistributing flow around the point bar. Furthermore, this suggests that Outcrop 3 is representative of an upstream-to-bend-apex transition within a large-scale point-bar planform.
Recognition of multiple channels at Outcrop 4 was based on large-scale erosional truncation, IHS bed-orientation changes, large cumulative thicknesses of the middle McMurray, thick sand-package thicknesses, changes in relative scale of sedimentary structures, and the occurrence of large mud clasts. Similarities in depositional expression between channels suggest autogenic channel stacking (within-valley stacking), rather than the stacking of separate valleys. Finally, discordant paleocurrents within the basal sand-dominated facies are likely representative of amalgamated channel-bottom facies from several generations of channel. This suggests that only the upper intervals of basal sand-dominated facies are genetically linked to the overlying IHS facies. / Thesis (Master, Geological Sciences & Geological Engineering) -- Queen's University, 2012-01-30 13:25:32.53
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:OKQ.1974/6985 |
| Date | 30 January 2012 |
| Creators | JABLONSKI, BRYCE VINCENT JOHN |
| Contributors | Queen's University (Kingston, Ont.). Theses (Queen's University (Kingston, Ont.)) |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English, English |
| Detected Language | English |
| Type | Thesis |
| Rights | This publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner. |
| Relation | Canadian theses |
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