--> ABSTRACT: Facies and Diagenesis of Hartford Limestone Member (Topeka Limestone Formation, Upper Pennsylvanian Series) in East-Central Kansas, by Jeffery A. Silfer and Daniel F. Merriam; #91039 (2010)

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Facies and Diagenesis of Hartford Limestone Member (Topeka Limestone Formation, Upper Pennsylvanian Series) in East-Central Kansas

Jeffery A. Silfer, Daniel F. Merriam

The Hartford Limestone Member (Topeka Formation, Upper Pennsylvanian Series) thickens along strike in east-central Kansas. A distinct vertical lithologic succession consisting of a basal skeletal lithology, an intermediate algal facies, an oncolite facies, and an upper fusulinid lithology characterizes the Hartford Member on outcrop. Similar sequences of rock types historically have been termed "algal-mound complexes" in the Mid-Continent region.

The skeletal facies consists of diversely fossiliferous, medium to thick-bedded skeletal wackestone. An increase in phylloid algae (probably mostly the genus Eugonophyllum) and an associated decrease in other biotic constituents distinguish the algal lithology from the basal rock type. Grain-supported oncoidal packstone with abundant Osagia comprises the oncolite facies. The fusulinid lithology, which caps the mound complex, consists of fusulinid wackestone. Stratigraphic relationships and depositional interpretations suggest that a minor transgressive-regressive episode of the Late Pennsylvanian epeiric sea generated the observed lithologic succession.

Petrographic observations reflect a complex diagenetic history for the Hartford Limestone Member. Specifically, a paragenetic sequence of drusy high-magnesium calcite cement, gypsum, dolomite, chert, low-magnesium nonferroan calcite cement, low-magnesium ferroan calcite cement, and pyrite seems consistent with the available evidence. Exposure of the Hartford Limestone Member to a series of near-surface and deeper burial diagenetic environments best explains the authigenic sequence.

Comparison of three exposed Shawnee Group algal mounds yields three general time-transgressive trends. Successive buildups display (1) a distinctive sequence of nonmound, mound, and mound-associated rock types, (2) a reduction in lateral extent and vertical thickness, and (3) a decrease in algal abundance through time.

AAPG Search and Discovery Article #91039©1987 AAPG Mid-Continent Section Meeting, Tulsa, Oklahoma, September 27-29, 1987.