Earth Sciences Report 2006-06

Earth Sciences Report 2006-06

ESR 2006-06

Subsurface Geology of the Athabasca Wabiskaw-McMurray Succession: Lewis-Fort McMurray Area, Northeastern Alberta (NTS 74D/14)

ERRATUM: The Appendix 4 files are missing.

Most of the bitumen resources in the Athabasca Wabiskaw-McMurray deposit are contained in fluvial, estuarine and marginal marine sediments of the Lower Cretaceous McMurray Formation. The subsurface of the Lewis area is characterized by data from about 1189 wells, including examination of about 50 cores. Cross-section grids were completed within the Lewis area, which were linked on a larger scale with the Regional Geological Study (RGS) main and north study areas, completed by the EUB in 2003.

The informal stratigraphic nomenclature for the Lewis area includes Lower McMurray fluvial; 'Middle'/Upper McMurray estuarine/coastal plain succession; Wabiskaw D valley-fill; Wabiskaw D regional marine shale; and Wabiskaw C succession. Within the 'Middle'/Upper McMurray further subdivision into the A1 and A2 sequences, as was done in the RGS, is maintained. However, the regional grid of cross-sections constructed during the present study show that the Lewis A1 and A2 sequences, although in the identical stratigraphic position as the RGS A1 asnd A2, are younger than the units mapped in the RGS. These younger units are called A1L and A2L for the Lewis area.

The paleogeographic evolution of the Lewis area includes five main phases:

1) Lower/'Middle' McMurray fluvial/fluvio-estuarine channel and point bar complexes, which formed during lowstand and early transgressive conditions;

2) 'Middle'/Upper McMurray A2L relict and reworked bay-fills, crevasse splays, fluvio-estuarine tributaries, and local bay-head deltas that resulted from deposition and reworking during early transgressive phases;

3) 'Middle'/Upper McMurray A1L relict and reworked bay fills, washover deposits, and back-barrier deposits that resulted from deposition and reworking during middle transgressive phases;

4) Wabiskaw D valley-fill and regional marine shale, deposited during maximum flooding of the main McMurray-Wabiskaw transgression; and

5) Wabiskaw C successions, formed during waning transgressive and initial regressive phases.

Hein, F.J., Cotterill, D.K. and Rice, R.J. (2006): Subsurface geology of the Athabasca Wabiskaw-McMurray succession: Lewis-Fort McMurray area, northeastern Alberta (NTS 74D/74E); Alberta Energy and Utilities Board, EUB/AGS Earth Sciences Report 2006-06, 67 p.