Caliche Soil Horizons on Oolitic Shoals and Carbonate Mud Mounds in Carboniferous (Newman Limestone) of Eastern Kentucky: ABSTRACT

A sequence of oolitic calcareous grainstone shoals and calcareous wackestone and packstone-bank and interbank deposits is exposed near Olive Hill, Kentucky. The shoals and banks underwent periods of exposure, as they are capped by beds that represent stages of deposition or caliche weathering in the supratidal zone. The caliche weathering zones are similar to those found on Caribbean Islands and in the southwestern United States. The first type of caliche zone is analogous to the subaerial crusts of the Caribbean area. These crusts are brecciated, often silicified, laminated calcareous mudstones which formed on and within the shoals and mud mounds. They are present as beds or coat fractures which transect bedding planes. Petrographic characteristics include microbrecciation, grains coated with laminated or dense micrite, extensive micritization, pelletoid fabrics, root tubules, and micrite and yellowish-brown spar cements. The second caliche type, similar to those of the southwestern United States, is a nodular, brecciated calcareous mudstone that developed from supratidal and intertidal calcareous muds. The basal part of this caliche unit is a fossiliferous, but intensely brecciated, parent rock; this zone grades upward into a nodular sequence which may be capped by a thin-brecciated, laminated crust. Original depositional fabrics have been obliterated in the nodular section; the nodules are composed of microspar containing breccia clasts and root tubules, and are disrupted by subhorizontal fractures. Both caliche types display End_Page 785------------------------------ desiccation-expansion "teepee" structures. Caliche clasts are reworked into overlying intertidal-supratidal deposits, indicating that weathering occurred near sea level and contemporaneous with offshore deposition. End_of_Article - Last_Page 786------------