ABSTRACT A laterally discontinuous sandstone at the south end of the Tellico-Sevier syncline in Blount County, Tennessee, was mapped in 1955 by Robert Neuman and in 1965 by Neuman and Willis Nelson of the U.S. Geological Survey as a “quartzite” that they considered to be the uppermost bed of the Bays Formation (Ordovician). On the basis of new mapping and conodont biostratigraphy, lithostratigraphy, and regional K-bentonite correlations, this sandstone, a distinctive quartz arenite, is reassigned to and correlated with the Clinch Sandstone (Silurian). At the Harrison Branch section (HBRA) in Blount County, in an exposure near the confluence of Harrison Branch and the Little Tennessee River, this sandstone underlies the Devonian Chattanooga Shale, and it overlies ~43 m of gray limestones and shales that are themselves above the red clastic and minor carbonate rocks of the Bays Formation. The limestones and shales between the Bays Formation and this sandstone crop out on a wooded hillside and were apparently not observed by Neuman and Nelson during their mapping of the region. We measured the HBRA section, collected 20 samples from the limestone interval, and processed them for conodonts. These limestones contain a definitive Late Ordovician (Katian) conodont fauna that includes Drepanoistodus suberectus , Plectodina tenuis , Panderodus gracilis , and Phragmodus undatus . On the basis of this fauna, the 40+ m of limestone between the youngest red beds of unequivocal Bays Formation (below) and the quartz arenite (above) can be assigned to the Ordovician P. tenuis zone or younger, making them correlative regionally with limestones of the Trenton Group. Using these new biostratigraphic data combined with existing tephrostratigraphic relations of Ordovician K-bentonites, we identify the overlying sandstone at the HBRA section as an erosional outlier of the Silurian Clinch Sandstone, and we correlate the Ordovician-Silurian-Devonian unconformities at these two localities, which are now better constrained, with unconformities A through F in the Silurian and Devonian of this region, as identified and described in detail at several exposures north and northwest of the Tellico-Sevier syncline, most prominently at outcrops near Wytheville, Seven Mile Ford, and Max Meadows in southwest Virginia, where Devonian strata unconformably overlie Ordovician strata.

Abstract Regional contour maps are shown on the surface of the Trenton in the western half of Ohio, and on the Berea and Clinton in eastern Ohio. The major structural features are the Cincinnati arch, as expressed by the Trenton, and less conspicuously, the syncline (Parkersburg) and adjacent Cambridge anticline as shown by the Berea in eastern Ohio. Structure contour maps are given for four areas in eastern Ohio. These are for the Berea in southeastern Meigs County and northeastern Muskingum County, for the Berea and shallow sands in the junction of Guernsey, Noble, Belmont, and Monroe counties, and for the Clinton sand in the Homer field of Knox and Licking counties. The majority of the producing fields of eastern Ohio display some relationship to structure, although the relationship is ideal in but few cases. Structural highs are generally barren, the production lying on the flanks of anticlines or even in the upper ends of synclinal embayments. There is, then, a structural relationship, though not in the stricter sense in which the anticlinal theory was once applied. Most of the oil and gas accumulations are associated with some kind of structural irregularity. As a rule, there is a definite parallelism between the trend of production and the strike of the rocks. In a few places accumulation appears to be entirely a matter of lithology, notably in the Cow Run sand of the Chester Hill field, in Athens, Morgan, and Washington counties. In general, three factors appear to govern accumulation: local structure, water content and energy of movement in the sand, and the porosity of the sand. Since local structure exerts some influence on both water content and artesian conditions in a given sand, structure is regarded by the writer as the dominant factor. These remarks as to accumulation apply to the Berea and higher sands. The Clinton has long been known as a sand practically devoid of water, although this classification can be accepted only as relative. Because of the lack of reliable key beds, the rapid divergence from surface beds, and the lenticularity of the Clinton, one cannot be sure of structure as mapped for the Clinton. Clinton production appears to be along a transition zone where the sand thins and is replaced on the west by shales.