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Build-and-Fill Stratigraphic Sequences in Carbonates


Build-and-fill sequences are a particular class of carbonate sequences formed during a full cycle of sea-level rise and fall and are characterized by the following: thin (typically 10's of m thick) compared to amplitude of sea-level change; drape paleotopography; maintain similar thickness throughout wide geographic areas; have a complex internal architecture of building and filling relief. Build-and-fill sequences occur in icehouse, greenhouse, and transitional systems throughout the geologic record. Less-than-optimal carbonate production is the primary control that leads to underfilled accommodation. The build-and-fill zone typically occurs in middle portions of ramps, and interior lagoons of rimmed platforms located at intermediate positions between sea-level highstand and lowstand position. Relatively gentle substrate slopes are a common theme in build-and-fill examples; they result in rapid lateral migration of areas of shallow-water production when combined with relatively high rates of sea-level rise and fall, and may promote underfilled accommodation. The predominant constructional building phase occurs during transgressions (e.g. coral reefs, microbial buildups, algal facies, and grainstone facies). The filling phase (commonly packstones/grainstones; siliciclastics in mixed systems) predominates during forced regressions, likely as a result of limited accommodation. Topography-draping deeper water facies, hiatal surfaces, and hardgrounds can form during maximum flooding. During sea-level fall, deposition may result in building constructional relief as well, but these geobodies are typically more tabular (biostromal) than those formed during rises, stillstands, or minor rises during an overall fall. Where shallow-water conditions intersect complex topography, currents may be focused, depositing grainy carbonate and siliciclastic facies in lows. If energies are too high along topographic highs, boundstone, wackestone, and packstone facies may accumulate in adjacent topographic lows where current energies are weaker. Examples from the Pleistocene, Pliocene, Miocene, Cretaceous, Triassic, Jurassic, Permian, Pennsylvanian, Mississippian Devonian, and Proterozoic illustrate build-and-fill sequences from various settings and systems. Examples include reservoir systems, such as the Upper Jurassic Arab D, Pennsylvanian Midcontinent and Paradox Basin, and Miocene-Pliocene in Indonesia.