--> Approaches to Source-To-Sink Reconstruction of Ancient, Outcropping Clastic Basin-Fill Successions: Examples From the Shannon Basin (Western Ireland) and the Western Interior Basin, USA

AAPG Annual Convention and Exhibition

Datapages, Inc.Print this page

Approaches to Source-To-Sink Reconstruction of Ancient, Outcropping Clastic Basin-Fill Successions: Examples From the Shannon Basin (Western Ireland) and the Western Interior Basin, USA

Abstract

Source-to-Sink analyses (S2S) are normally applied to ancient subsurface or Modern-Recent near-surface successions adjacent to onshore catchments. The method is equally applicable to outcropping clastic basin-fill successions, even where the rocks in the basin-fill succession occur in vertical sequence. S2S analysis here requires calculation of key S2S parameters from the data and conversion to uncompacted values. Global S2S statistics then provide direct lead-in to interpretation of quantitative characteristics of systems that formed the ancient basin-fill successions. The 2200 m thick basin-fill succession of the Carboniferous Shannon Basin in Western Ireland is upward-shallowing from basinal mudstones and submarine fan deposits through slope to deltaic and incised valley-fill sediments. The slope succession is 700 m thick (vertical thickness), which transforms to an approximately 900 m uncompacted succession. Conventional trigonometry yields a slope length of approximately 52 km for a slope with 1o inclination. This slope length then provides a direct lead-in to comparison with similar, yet Modern-Recent S2S systems from the global statistics. The Shannon Basin shelf width is assessed to be 20–30 km and the catchment providing the sediment 40–50000 km2. Moreover, the areal extent of the Ross submarine fan system fed from the slope succession, is interpreted to be around 8–10000 km2, in accordance with the mapped extent of the Ross Formation from outcrop and well data. Despite the uncertainty in the calculations, the S2S analysis provides a powerful method of reconstructing unseen parts of the S2S system related to the outcropping succession, which in turn must be checked against available field data or concepts for such systems. The Campanian Mesaverde Group of the Western Interior Basin, United States provides a different challenge in that most of the dip dimension of the coastal plain-shelf-offshore segments of the S2S system is preserved. The Mesaverde antecedent catchment is not preserved, and now included in the Sevier thrust system. Structural reconstruction has provided a valid interpretation of the catchment segment of the S2S system back to what was likely a drainage divide in the antecedent Wasatch culmination. S2S analysis provides a reality check on the structural reconstruction in the context of the entire Mesaverde clastic wedge and provides a complete view the S2S system during deposition.