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Tempestites In A Teapot? Condensation-Generated Shell Beds In The Upper Ordovician, Cincinnati Arch, Usa, Benjamin F. Dattilo

Benjamin F. Dattilo

Skeletal concentrations in mudstones may represent local facies produced by storm winnowing in shallow water, or time-specific deposits related to intervals of diminished sediment supply. Upper Ordovician (Katian) of the Cincinnati region is a mixed siliciclastic-carbonate succession including meter-scale cycles containing a shelly limestone-dominated phase and a mudstone-dominated phase.

The “tempestite proximality model” asserts that shell-rich intervals originated by winnowing of mud from undifferentiated fair-weather deposits. Thus shell beds are construed as tempestites, while interbedded mudstones represent either fair-weather or bypassed mud. Meter-scale cycles are attributed to sea-level fluctuation or varying storm intensity.

Alternatively, the “episodic starvation model” argues, on …