Sedimentological, Ichnological, and Architectural Characteristics of Geobodies in a Fluvial to Estuary Setting: the McMurray Formation in the Christina River area, NE Alberta, Canada
Creators: Chen, Qi
Publisher: name: University of Alberta Library
Year: 2023

<p>The Lower Cretaceous McMurray Formation is the primary host of the crude bitumen reserves in the Athabasca Oils Sand Region. The regionally extensive meander belts associated with estuary point bars have been recognized as the primary reservoir facies in the McMurray Formation. It is widely accepted that dune sands of the cross-bedded sandstone (CB) and point bar heterolithic stratified sandstone and mudstone bedsets (IHS) are the two main facies constituents in the estuary meander belts. Previous studies on the McMurray Formation have emphasized subsurface datasets, which apply regional scale stratigraphic relationships and facies characteristics. These studies commonly generalize the interpretation of the two major facies as a continuous point bar succession: CB represents thalweg-associated sand dunes or the lower part of estuary point bars, and IHS represents the middle to the upper part of the point bars. A detailed investigation of variable geobodies in different parts of a fluvial-estuary setting is generally lacking in the McMurray Formation.<br>
This project provides variable solutions to fill the gap in the above questions. In addition to conventional facies analyses through core and outcrop logging of the McMurray Formation, bedding orientational characteristics of geobodies are analyzed using photogrammetric 3D models of the studied outcrops. The objects of this dissertation are: 1) establish a local stratigraphic framework that can be compared to regional stratigraphy of the McMurray Formation; 2) establish a correlation between lithofacies and dipmeter tadpole log characteristics of estuary point bars; 3) integrate sedimentological, ichnological, and bedding orientational characteristics of depositional units to produce solutions of paleoenvironment reconstruction; and 4) investigate architectural stacking pattern of geobodies in fluvial to estuary settings.<br>
The key results of this dissertation are: 1) the established local stratigraphic framework reveals estuary channel filles developed from progradation of inner estuary channels during regression, and the internal stacking pattern of point bars can be resolved through the interpretation of dipmeter tadpole plots; 2) the CB facies of sand dunes is not always associated with estuarine channel thalweg or lower point bars, middle estuary sand dunes have been efficiently differentiated from point bars from their forward-accretion bedding configuration; 3) four types of deposits are identified in the McMurray Formation progressing from fluvial to the estuary (fluvial deposits, tidally influenced fluvial deposits, inner estuary point bars, and middle estuary compound dunes) through detailed comparison in the sedimentological, ichnological, and architectural characteristics of geobodies. The recognition and investigation of variable geobodies of the McMurray Formation are crucial for establishing stratigraphic models and paleogeographic reconstructions in sedimentologically complex fluvial to estuary settings. </p>