--> Abstract: Clearwater Formation, Cold Lake Oil Sands Deposit: Estuarine Incised Valley Complex?, by Carolyn Currie and Murray Gingras; #90124 (2011)

Datapages, Inc.Print this page

AAPG ANNUAL CONFERENCE AND EXHIBITION
Making the Next Giant Leap in Geosciences
April 10-13, 2011, Houston, Texas, USA

Clearwater Formation, Cold Lake Oil Sands Deposit: Estuarine Incised Valley Complex?

Carolyn Currie1; Murray Gingras1

(1) Earth and Atmospheric Sciences, University of Alberta, Edmonton, AB, Canada.

The proposed depositional model for the Cold Lake oil sands deposit is an estuarine incised valley fill comprising of fluvial deposits through tidal bar sediments. Thereby much of the Clearwater Formation in the area display low-diversity brackish-water trace-fossil suites that are dominated by Planolites, Teichichnus, Cylindrichnus, Terebellina, Skolithos, Palaeophycus, and in some settings Gyrolithes. However, detailed core analysis — including documentation of physical and biogenic sedimentary structures — reveals comparably diverse ichnofaunal assemblages are identified in the medial sequence of the Clearwater Formation in the Cold Lake area. The trace-fossil assemblage observed includes Planolites, Teichnichnus, Thalassinoides, Skolithos, Cylindrichnus, Asterosoma, and Arenicolites. Also seen in many of the core were traces such as Rhizocorallium, Siphonichnus, Scolicia, and Asterosoma. Most of the observed trace fossils are sporadically distributed throughout the interval, however Asterosoma and Rhizocorralium are most abundant in the lower part of the sequence. The reported trace assemblage is more consistent with sedimentation and animal colonization in fully marine conditions. Thus, the presence of these traces in the majority of core examined suggest that the proposed depositional model—i.e. tidal estuary—is questionable at the studied interval. We assert that the depositional setting occupied an embayed area that received sediment from the Clearwater hinterland, but generally maintained a marine salinity. This hypothesis leads to stratigraphic implications including that the medial strata may represent high-stand sedimentation rather than the transgressive sediment accumulation associated with incised valley fill.