Modern point bar deposits analogous to the Athabasca oil sands, Alberta, Canada
Smith, D.G. (1988). Modern point bar deposits analogous to the Athabasca oil sands, Alberta, Canada, in: de Boer, P.L. et al. (Ed.) Tide-influenced sedimentary environments and facies. Extended versions of papers presented at the Symposium on Classic Tidal Deposits, held August 1985 in Utrecht, Netherlands. pp. 417-432
In: de Boer, P.L. et al. (Ed.) (1988). Tide-influenced sedimentary environments and facies. Extended versions of papers presented at the Symposium on Classic Tidal Deposits, held August 1985 in Utrecht, Netherlands. D. Reidel Publishing: Dordrecht. ISBN 90-277-2622-1. ix, 530 pp., meer
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| Abstract |
The sedimentology of modern point bar deposits in several tidallyinfluenced meandering rivers, located in upper and middle estuarine settings of the Willapa River in southwest Washington State, U.S.A., and the Daule and Babahovo Rivers in Ecuador, South America, and a complete stratigraphic section of a Late Pleistocene Willapa River point bar deposit exposed in a sea cliff outcrop are compared to the so-called epsilon cross stratified channel deposits of the Athabasca Oil Sands. The following sedimentary features are present in all four study areas: (1) epsilon cross stratification (ECS) of sand and mud beds (couplets); (2) inclination of the ECS deposits and point bar surfaces averages 12 degrees, but ranges from 7 to 18 degrees; (3) the base of each sand unit is commonly in erosional contact with the underlying mud; (4) the top of each sand unit is normally gradational from sand to mud; (5) mud beds in the ECS normally contain either very thin sand interlaminae one sand grain thick, or sand grains are scattered throughout the mud; (6) sand beds contain ripple structures and mud beds are laminated; (7) a fining trend of sand grains size occurs in point bars both upward and downstream ,(proximal to distal); (8) sand beds contain mud balls and chips, and occasionally slide blocks of tidal marsh mud; (9) the occurrence of bioturbation, organic litter and organic-rich mud increases upward and is common in the upper point bar. All of the above characteristics are found in the meandering river-estuarine reaches influenced by tidal flow reversals with a range of stage varying from 3 to 4,5 m (spring tide). In Ecuador, the tidally-influenced reaches of the Daule and Babahovo Rivers are located between 70 and 95 km upchannel from the river mouth at the Gulf of Guayaquil; the lower 70 km of river channel/estuary is straight and wide (2,5 km) with several large islands and sand bars. All of the sedimentary characteristics found in the modern tidally-influenced river-estuaries can be observed in outcrop and drill core of the interpreted channel deposits in the Athabasca Oil Sand deposits of the Lower Cretaceous McMurray Formation in northeast Alberta. |
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