CURRENT PRE-CAMBRIAN LITERATURE S41 
mentary rocks, many of them being completely crystalline schists and 
gneisses, which are of pre-Paleozoic age. Further, in this region is a 
great series of sedimentary rocks known as the Ocoee series, the 
position of which is not determined, but which may include both 
Paleozoic and pre-Paleozoic rocks. Apparently all of the series of 
sedimentary rocks thus far mentioned rest unconformably upon.a still 
older granite-gneiss-schist complex. It therefore appears clear that 
there are at least three series of rocks represented in the Appalachian 
region and the Piedmont Plateau, and there may be more. 
Until the great structural problems of the Appalachian and Pied- 
mont Plateau region are settled, the only safe course is to call pre- 
Paleozoic the rocks which are certainly below the Paleozoic, leaving 
open the question of their further classification as Archean or Algon- 
kian. In the case of the Ocoee, at the present time, the series cannot 
be placed even as closely as pre-Paleozoic. In work in Maryland, 
North Carolina, Tennessee, Alabama, and Georgia, as shown by the 
above summaries, this plan in some cases has not been followed, but 
rocks supposed to be of pre-Paleozoic age have been somewhat arbi- 
trarily assigned to the Archean or Algonkian. The use of these names, 
without definite knowledge of the structural features as a basis for the 
reference, is a hindrance rather than a help to further classificatory 
work. When the age of a series in the region is more definitely 
determined, the rocks can be placed as Algonkian or Archean without 
contradicting previous statements. (Ca IK Tia atist 
