Abstract: Reconnaissance for Uranium in Appalachian Basin--Some Initial Results

Arthur F. Jacob

Anomalous radioactivity occurs in several Paleozoic sedimentary rock units in the Appalachian basin.

Cambrian sandstone beds show radioactivity 20 times background in places. Detrital monazite is 10 to 50 percent of some samples, so most of the radioactive deposits probably are fossil placers. However, some thin sections and radiographs show radioactive secondary hematite and unidentified radioactive clay-size materials; these radioactive minerals suggest that local postdepositional mobilization and concentration of uranium or thorium have occurred. Limited exposures make depositional environments difficult to interpret.

Uranium deposits (maximum 0.3 percent U) near Jim Thorpe, Pennsylvania, are below and in the Spechty Kopf Member of the Catskill Formation (Devonian-Mississippian). They are in fine to coarse-grained sandstone deposited by meandering and braided rivers on the landward part of a deltaic plain. Here, uranium-bearing, oxidizing ground water that was moving basinward locally may have encountered reductants and precipitated the deposits in this area. Small, lower grade uranium deposits in north-central Pennsylvania and south-central New York are in darker rocks deposited in distributary channels on the seaward part of a deltaic plain. Here, reducing solutions may have been responsible for precipitating the uranium.

Small deposits of uranium (maximum 1.8 percent U) are in beds of braided-stream(?) conglomerate interbedded with red beds in the upper part of the Mauch Chunk Formation (Mississippian and Pennsylvanian) near Jim Thorpe, Pennsylvania. A sandstone sample of the Mauch Chunk from Webster Springs, West Virginia, showed 0.04 percent U.

Radioactive anomalies (maximum 45 times background) in the Pocono Formation (Mississippian) near Marlinton, West Virginia, are in rocks formed in distributary channels on the seaward part of a deltaic plain in a belt at least 47 km long. One sample has 0.016 percent U and 0.11 percent Th; semiquantitative spectrographic analysis of three samples show 1.5 to 2 percent Ti, 2 to > 2 percent Zr, and 0.3 to 0.6 percent rare earths. These data and abundant zircon and ilmenite in thin sections indicate that the deposits are fossil placers.

The Dunkard Group (Upper Pennsylvanian and Lower Permian) in Ohio, Pennsylvania, and West Virginia consists of a southern, red, sandy facies, an intermediate transitional facies, and a northern, gray, shaly facies. Part of the sand grains in the Dunkard are first-cycle grains derived from radioactive crystalline rocks farther south and east in the Blue Ridge and Piedmont provinces. Oxidizing ground water moving north and west down the depositional dip could have caused the red color of the red facies and transported diagenetically released uranium to depositional sites in the red or transitional facies. Sandstone beds in the red facies show radioactivity about two times background. A fluvial-channel sandstone bed near the southern edge of the transitional facies has radioactivity abou 12 times background and maximum 0.009 percent U. The Monongahela Formation (Upper Pennsylvanian), which underlies the Dunkard, shows similar relations.

AAPG Search and Discovery Article #90971©1976 AAPG-SEPM Rocky Mountain Sections 25th Annual Meeting, Billings, Montana