Abstract

Oolitic calcarenites of this formation were deposited in shallow water along the southwestern margin of the Illinois Basin northeast of the Ozark Shoal. Considerable divergence in shelf current patterns is indicated by the large variance for azimuths of cross-bed sets of oolitic calcarenites and by outcrop polymodal windrose diagrams. Tidal currents are also identifiable. During early diagenesis, aragonite was dissolved by the low-Mg water to form extensive moldic porosity within insoluble micrite envelopes. The porosity was later filled with mosaic calcite cement. Ooids with calcite spar interiors and off-center nuclei are thought to reflect the sequence: (1) solution of aragonitic ooid laminae within an insoluble micritic envelope; (2) gravitative settling of the nucleus to the bottom of the mold; and (3) filling of the mold by calcite cement that displaced the nucleus to a nongeopetal position.

First Page Preview

First page PDF preview
You do not currently have access to this article.