| Summary: | Thesis (Ph.D, Geological Sciences & Geological Engineering) -- Queen's University, 2014-09-15 17:47:09.822 The Early Cretaceous Bluesky Formation (Mannville Group) in the Peace River area of west-central Alberta, Canada, is a complexly stratified tide-dominated sediment body composed of monolithic and heterolithic sandstone. The Bluesky Formation is tide-dominated and was deposited during the latter part of a third-order transgressive systems tract. The Bluesky Formation is divisible into two valley-bounded sequences, informally referred to in this study as the “lower Bluesky unit” and the “upper Bluesky unit”. The lower Bluesky unit is composed of tide-dominated deltaic deposits. The upper Bluesky unit is composed of tide-dominated estuarine deposits. The lower Bluesky unit has abundant dynamically deposited mudstone layers (comprising 5-40% of most facies), many of which are interpreted to have been deposited under conditions of moderate to high suspended-sediment concentration (1-1000 g L-1) and appreciable current speeds (> 0.2 ms-1). The upper Bluesky unit, by contrast, has more sparsely distributed mudstone layers (comprising 0-15% of most facies) deposited primarily during slackwater and under conditions of relatively low suspended-sediment concentrations (< 1 g L-1). Both units are composed predominantly of subtidal and lower intertidal channel-bar and tidal-flat deposits. However, the most seaward deposits of the deltaic lower Bluesky unit contain sandstone-dominated heterolithic delta-front and mouth-bar deposits, whereas the most seaward environments of the estuarine upper Bluesky unit contain monolithic tidal sand-ridge deposits. The Bluesky represents deposition in slightly more seaward locations than the underlying Gething Formation, which is composed of lower-energy mudstone-rich facies of a fluvially dominated depositional system. Both the lower and upper Bluesky units are broadly aggradational with several autogenic internal erosional discontinuities, suggesting that high-energy ...
|
|---|