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The AAPG/Datapages Combined Publications Database

AAPG Bulletin

Abstract


Volume: 69 (1985)

Issue: 8. (August)

First Page: 1318

Last Page: 1318

Title: Upper Pennsylvanian Marine Algal Banks of Kansas: Comparison and Implications: ABSTRACT

Author(s): D. F. Merriam, S. B. Lamoreaux, J. A. Silfer, G. V. Wolf

Article Type: Meeting abstract

Abstract:

Marine algal banks (mounds or buildups) present in the Shawnee Group (Upper Pennsylvanian) crop out in eastern Kansas. The youngest of about 20 banks known to occur in the section differ in shape and size but, in general, cause a local increase in thickness that is compensated by a decrease in thickness of the overlying shale. The phylloid algae, Eugonophyllum and Epimastopora, trapped and bound the carbonate mud in a role similar to the modern sea grass, Thalassia, in Florida Bay. The soft mudbanks created barriers to water circulation and fauna distribution. The Shawnee banks decrease in size, contain less algae and more micrite, and are more difficult to define with decreasing age. The Plattsmouth bank formed instantaneously by building on the "normal" lithology over a large area; the Ervine Creek bank started locally and spread laterally so it is funnel shaped; the Hartford bank is diffuse with the algae occurring in small curls instead of larger, flat blades. All three banks are capped with a layer of osagite/pellets/fusulinids. The Plattsmouth bank is topped with a crust of algal(?) material, and the Ervine Creek bank shows evidence of solution features, indicating possible subaerial exposure. Interpretation of the sequence is that the elongated banks were formed in shallow, warm water parallel to shore in a regressive environment until smothered by an influx of fine clastic material. Differences in size, shape, algae type and quantity, and postdepositional alterations result from subtle differences in setting and timing of development.

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