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The AAPG/Datapages Combined Publications Database
AAPG Bulletin
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Thick (15 to 35 m) sandstones occur in the upper Mannville (Colony, McLaren, and Waseca Members, collectively about 45 m thick) over a substantial area (T35 to 65, R1 to 20W4) of east-central Alberta. The sandstones can occur in belts flanked by zones dominated by siltstones and shales. The upper Mannville is a continental sequence in this area and the thick sandstones have previously been interpreted as (1) deposits of a network of vertically aggrading, laterally stable channels, and (2) valley-fill deposits. Investigation of a densely drilled area in the Wainwright field (T45, R6W4) shows that the absence of two 2-m thick shales that separate three correlatable sandstones, 9 m, 4 m, and 5 m thick, results in a 20-m thick sandstone in one location. This suggests that the "thick" sandstones may be the result of the amalgamation of several sandstone sequences.
Trace-fossil evidence and lateral continuity of the uppermost
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(^sime 10 m) lithologic units of the upper Mannville in the Wainwright area indicate that these beds were deposited in a marine depositional environment. The same interval in a nearby well (11-21-47-2W4) has been confirmed as marine (contains dinoflagellates) and also contains dicotyledonous tricolpate pollen grains. The presence of this type of pollen grain means that, at least locally, the disconformity that is supposed to occur at the base of the overlying Joli Fou Formation occurs instead within the sandstones at the top of the Mannville, as suggested by Stelck.
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