BIOSTRATIGRAPHY OF THE ‘7-11 MINE’ (DESMOINESIAN-MISSOURIAN: PENNSYLVANIAN:CARBONIFEROUS), COLUMBIANA COUNTY, EASTERN OHIO

The biostratigraphic position of 7-11 Mine palynomorphs, conodonts, and ammonoids is consistent with a late Desmoinesian to early Missourian age with a "minor" unconformity (1 million years (My) or less) at the Desmoinesian-Missourian boundary. In contrast, the biostratigraphic position of the 7-11 Mine macroflora suggests a longer unconformity (>4 My) above the end-Desmoinesian extending into the Virgilian/Stephanian C. New biostratigraphic data from 7-11 Mine blattoids supports the occurrence of Missourian/latest Cantabrian to Stephanian A-B age deposits above the end-Desmoinesian unconformity in the northern Appalachian Basin.

Kosanke (1986), Kosanke and Cecil (1996), and Peppers (1996) reported palynomorphs from three 7-11 Mine coal beds corresponding to the Desmoinesian Lycospora granulata-Granasporites medius (GM) to early Missourian Punctatisporites minutus-Cyclogranisporites obliquus (MO) zone interval of Peppers (1984, 1996). Merrill (1974; 2001, personal communication) reported conodonts from both 7-11 Mine marine zones as occurring within the early Missourian Streptognathodus cancellosus-S. oppletus zone of Lane et al. (1970). McComas and Mapes (1988) reported ammonoids from the lower marine zone corresponding to the early Missourian Pennoceras zone of Boardman et al. (1994). McComas (1989) reported macrofloras from the lower and upper non-marine zones as typical of the Virgilian/Stephanian B-C or Permian, but interpreted their 7-11 Mine occurrences as range extensions into the lowermost Conemaugh (i.e., Missourian). Wagner and Lyons (1997) re-examined the 7-11 Mine macrofloras and re-interpreted them as belonging to the Lescuropteris/Danaeites Assemblage (zones 11 and 12) of Read and Mamay (1964), supporting a Stephanian C or younger age above the end-Desmoinesian unconformity. Based on new data, very large blattoids and spiloblattids in the upper non-marine zone are consistant with the Masonian or Aberscreekian zones of Durden (1979), supporting the occurrence of Missourian/latest Cantabrian to Stephanian A-B age deposits above the end-Desmoinesian unconformity.