SOME CONSTRAINS ON THE DENUDATION RATE OF THE APPALACHIAN PLATEAU

Three little petrologic and geomorphologic studies were done in two years. In addition to their separate content, they all add some constrains to the thickness of overburden strata and the rate of denudation of the Appalachian Plateau.

Samples of Carboniferous age limestone along I-70 from Wheeling, WV to Columbus, OH were collected to examine the occurrence of stylolite. In all samples except the Columbus Limestone, only a few minute serrated stylolite were noticed. The lack of stylolite caused by pressure solution indicates the overburden strata in the west flank of the Appalachian Basin were limited in thickness. An earlier study (White and Law, 2000) on siderite concretion in the Pennsylvanian Mahoning Sandstone, suggested the maximum burial depth of the sandstone could be approximately around 1000 meters.

A simple study of creek erosion in a very small but well-confined drainage basin at New Concord, Ohio during August and December of 2001suggests that: 1) erosion rate estimated by the suspension load is in the order of 0.1 m/Ma; 2) Dissolved load estimated by the [Ca+2] is 150 ppm in a 15 liter/min creek flow. Assume the calcium in the water is mostly contributed by the dissolution of the approximately 1 meter thick Ames Limestone in the drainage area, the limestone bed would be totally dissolved in less than one million years. This result suggests the rate of denudation in the current Appalachian Plateau is not controlled by limestone strata but by other exposed clastic sedimentary rocks. The estimated denudation rate is likely lower than the true value due to the lack of data during the flood stage. But the rate is still low even it is increased by a whole order of magnitude (1 m/Ma).

Above studies point to a possibility that the denudation rate in the west flank of the Appalachian Basin was low. An implication of this result is that the age of current landscape in this area could be older than the Cenozoic era.