Stratigraphic and Depositional Architecture of a Slope Channel System: Isaac Channel 5, Castle Creek South, Isaac Formation, Windermere Supergroup, British Columbia, Canada

SCHWARZ, E. Y ARNOTT, R.W.C

Atlas of Deep-Water Outcrops, American Association of Petroleum Geologists, Studies in Gelogy # 56

Co-Published by AAPG and Shell Exploration & Production

Lugar: Tulsa; Año: 2007;

AbstractA detailed architectural analysis was conducted in Isaac Channel 5 of the Isaac Formation in the Castle Creek area (east-central B.C., Canada, Figure 1). Isaac Channel 5 developed within a slope turbidite system in the Neoproterozoic passive margin of western North America where debris flows and mass movements were common (see Arnott & Ross, this volume). Isaac Channel 5 crops out over a 3.5 km (2.1 mi)-long section oriented oblique to mean paleoflow (toward NW) and represents a long-lived depositional pathway that accumulated ~100 m (~330 ft) of mostly sand sediment (Figures 2, 3). It consists of three stacked, high net/gross channel-complex fills (each 8-30 m, 25-100 feet thick) that correspond to shorter-term flow conduits (C1, C2, C3, Figures 2, 3). Channel complexes are multi-storey units that consist mainly of thick-bedded, Bouma Ta and Tab divisions, mudstone-clast breccia, and medium-bedded, dune cross-stratified sandstone. Granule conglomerate to medium sandstone is the most common grain-size range. Five different channel-fill elements were identified within the channel complexes. Each consists of a different assemblage of facies, stratal patterns, and/or lateral dimensions, and as a consequence, unique reservoir  characteristics (Figure 4). The development of channel-fill elements is linked to specific combinations of flow and sediment flux conditions that in turn controlled aggradation and erosion within channels. Channel complexes are capped by siltstone-rich, thin-bedded units (T2, T3 and T4, Figures 2, 3) that represent intervening episodes of overbank/levee sedimentation. Additionally, debrite deposits (D1 & D2) that occur typically at the base of channels and channel complexes, are the result of cohesive sediment-gravity flows during channel/channel complex initiation. These siltstone- and mudstone-rich units, which separate channel complexes and extend across the full outcrop (> 3 km long, > 2 mi) represent the most important potential impediments to intrastratal fluid flow.Strata of Channel 5 document the stratigraphic complexity, in terms of evolution and reservoir characterization, that can be expected in slope turbidite channel systems, and make it a potential analogue for similar systems developed in continent-margin basins that are mostly known from subsurface data (e.g. offshore Brazil, Egypt, Gulf of Mexico, West Africa).