Chepultepec and Copper Ridge Formations

Chepultepec Formation (Ulrich, 1911). Dolostone, argillaceous, sandy, light-gray, light-olive-gray, and grayish-brown,very-fine- to coarse-grained. Contains white to light-gray chert nodules and beds; sandstone and dolomitic sand stone lenses and beds; scattered sand grains; minor intraformational conglomerate beds; greenish-gray clay shale partings; and dark-gray, petroliferous dolostone. The Chepultepec ranges from 300 to 850 feet in thick ness (Brent, 1963). Copper Ridge Formation (Ulrich, 1911). Dolostone, generally divisible into a lower olive-brownish-gray to darkgray, medium- to coarse-grained, thick- to massive-bedded dolostone, some of which emits a petroliferous odor on freshly broken surfaces ("stinkstone"); and an upper olive-brownish- gray to light-gray, very-fine- to medium-grained dolostone with minor silty and sandy zones. Olive-black, oolitic chert beds and light-gray to white, chalcedonic chert nodules are present. Similar divisions were described by several geologists including Miller and Brosgé (1954), Miller and Fuller (1954), and Bridge (1956). The Copper Ridge ranges from 415 to 850 feet in thickness. Maynardville Formation (Oder, 1934). Limestone and dolostone. Limestone, locally dolomitic, locally argillaceous, medium- to dark-gray, very-fine- to fine-grained, medium- to thick-bedded, mottled; with argillaceous to dolomitic bands and partings which give the rock a ribbon-banded or straticulate appearance. Dolostone, very-light-gray to dark-gray, light-olive-gray to olive-gray and locally yel low ish-gray or dark-bluish-gray, very-fine- to coarse-grained, finely laminated to thick-bedded (thin-bedded near top of unit distinguishes it from overlying Copper Ridge Formation); with black chert; minor lenses and beds of fi ne- to medium-grained, locally dolomitic sandstone; very-fine-grained, yellowish-gray, argillaceous sand stone; and rounded-pebble conglomerate; all locally present. Generally the limestone is in the lower one third to one-half of the unit and the dolostone is in the upper two-thirds to one-half of the unit, with a transition zone from one to the other. The Maynardville Formation ranges from 60 to 300 feet in thickness, thinning to the east-northeast from Lee County. Thickness variations may be due in part to grouping of the limestone with the underlying Nolichucky Formation or the dolostone with the overlying Copper Ridge, as noted by Derby (1965).
State Virginia
Name Chepultepec and Copper Ridge Formations
Geologic age Cambrian-Ordovician
Lithologic constituents
Sedimentary > Carbonate > Dolostone
Sedimentary > Chemical > Chert
Sedimentary > Clastic > Sandstone (Calcareous)
Sedimentary > Carbonate > Limestone
Comments Includes Maynardville Formation where present; Appalachian Plateaus and Valley and Ridge

Virginia Division of Mineral Resources, 1993, Geologic Map of Virginia: Virginia Division of Mineral Resources, scale 1:500,000.

Virginia Division of Mineral Resources, 2003, Digital Representation of the 1993 Geologic Map of Virginia, Publication 174, CD ROM (ISO-9660) contains image file, expanded explanation in pdf, and ESRI shapefiles, scale 1:500,000.

NGMDB product
Counties Lee - Scott - Smyth