CIG   05423
CENTRO DE INVESTIGACIONES GEOLOGICAS
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Understanding Channel-Overbank Interactions in Deep-Marine Slope Settings: Architectural Analysis of Channel and Levee Elements in the Neoproterozoic Isaac Formation (Windermere Supergroup), Southern Canadian Cordillera
Autor/es:
SCHWARZ, E., KHAN, Z. AND ARNOTT, R.W.C.
Lugar:
Long Beach, USA
Reunión:
Congreso; 2007 AAPG Annual Convention and Exhibition; 2007
Institución organizadora:
AAPG
Resumen:
Abstract
Well-exposed,
periglacial slope deposits in the Neoproterozoic Isaac Formation allow
channel-fill and genetically-related overbank elements to be studied in detail.
The key to genetically linking these stratal elements is the occurrence of
muddy turbidites interbedded with discontinuous thin granule conglomerate and
dune-cross-stratified sandstone within overbank deposits. These strata drape a
low-relief erosion surface (<1.5 m deep) that occurs at a slightly higher
stratigraphic level than the base of the adjacent channel-fill. Both these
surfaces are interpreted to represent erosion and bypass by energetic flows
during channel initiation. Once initiated, most flows bypassed the channel but
also spilled out onto the surrounding overbank area, depositing incomplete and
complete Bouma sequences (levee element). The upward-fining and -thinning trend
observed in many levee elements suggests that levee aggradation progressively increased
channel confinement, restricting overspilling to the uppermost dilute parts of
flows. Changes in flow conditions triggered early filling of the channel by
sand/granule-rich, high-concentration flows (amalgamated Ta divisions) with
minor overspill onto the levee. Latest stage of channel infill is always
characterized by thin-bedded deposits suggesting deposition from low-energy,
dilute flows (abandonment element). This evolution is repeated several times in
Isaac Formation strata producing vertically stacked channel-fill elements
separated by abandonment elements, and surrounded by genetically-related levee
elements. The fact that the abandonment element described here is not traceable
into the adjacent levee element, but onlaps it, differs from previous
outcrop-based examples and resembles more the configuration observed in several
well-imaged, subsurface examples in which inner levee elements onlap
interpreted outer levee elements.