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Recognition Criteria and Facies Models
Lower Paleocene Drowned Valley and Barred Estuaries, Canadian Arctic Islands: Aspects of Their Geomorphological and Sedimentological Evolution
Barred, coastal plain estuaries and drowned valley estuaries comprise paralic, basal Paleocene strata in the eastern Arctic Islands of Canada. The estuarine deposits accumulated during initial transgression over a regional, sub-Paleocene unconformity, a surface corresponding to a third-order sequence boundary.
Fundamental differences exist between valley types containing the estuarine facies, depending on the nature of the bedrock. Shallow, broad valleys were eroded into nondeformed, moderately to weakly indurated rocks only slightly greater in age; these consequent drainage patterns are relatively young. Deep, narrower valleys are underlain by highly deformed, highly indurated, lower Paleozoic strata; drainage patterns here are very old. These geomorphic differences are reflected in the different estuarine facies and valley-fill stratigraphies. Shallow valleys were filled with barrier-inlet and washover sands, and finer grained lagoonal, marsh, tidal flat and estuarine channel deposits. The deeper, higher relief bedrock valleys are characterized by lower estuary spits and bars, middle estuary channels and tidal flats, and upper estuary-fluvial channels; coastline configuration was initially embayed, but became ‘straighter’ as bedrock relief was subdued. Both valley types existed at the same time in the basin.
It is maintained throughout the analysis that the geomorphic aspects of the antecedent valleys must be included in facies models that attempt to make the distinction between different types of estuary in the rock record, and even the more basic distinction between estuarine and other paralic deposits.
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