Franseen, Evan K.1, Robert H. Goldstein1
(1) University of Kansas, Lawrence, KS
ABSTRACT: Build-and-Fill Sequences: Predictable Patterns of Creation and Destruction of Paleotopography in Small-Scale Sequences
Carbonate and siliciclastic strata deposited during ice-house periods contain
small-scale sequences resulting from high-amplitude sea-level fluctuations. Many such
sequences maintain similar thickness throughout wide geographic areas despite draping
topography and containing facies that both build and fill relief. This pattern is
predictable given knowledge of the sea-level history, paleotopography, and controls on
Pennsylvanian strata in Kansas were deposited on a low-relief shelf. Paleotopographic relief was produced within sequences by deposition of phylloid algal and carbonate grainstone facies (including oolites), deposition of deltaic wedges, and erosion during lowstands. Relief was filled by siliciclastics and phylloid algal and grainy carbonates.
Upper Miocene sequences drape substrates with highly variable paleotopographic relief. Internally, relief was formed by stromatolites/thrombolites, coral reefs, carbonate grainstones, and erosion. Relief was filled predominantly by grainy carbonates (oolites), siliciclastics and evaporites.
Our examples indicate that given accommodation, topographically high substrates may be favored areas to build relief from boundstone and grainstone. Localized deposition of non-reservoir, delta-like siliciclastics may modify relief in paleo-low areas, given a paleotopographic focus. Where shallow-water conditions intersect complex paleotopography, currents may be focused, depositing grainy carbonate and siliciclastic facies in lows. If energies are too high along topographic highs, quiet-water boundstone/wackestone/packstone facies may accumulate (fill) in the topographic lows where current energies are weaker. Paleotopographic focus of fine-grained siliciclastics or adverse paleoceanographic conditions may inhibit development of carbonate facies dependent on clear-water conditions. Given high-frequency, high-amplitude sea-level fluctuations, alternation of building and filling processes even out topography over wide geographic areas.
AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.