coarser core samples; 128 RSA analyses were performed and 20 samples were 

 seived. An additional 23 sediment grab samples from an August 1976 survey of 

 8 lake floor profiles normal to Presque Isle (Fig. 5), obtained from Professor 

 P. Knuth (Edinboro State College), were analyzed. The RSA and sieve results 

 for these are also in Appendix B. 







s, 



Echogram profiles off Presque Isle Peninsula. 

 Grab samples at arrows show general sediment 

 composition: (s) sand, (c) clay. Closely 

 spaced jagged lines are electronic artifacts 

 suggesting a soft mud bottom is present at 

 the base of the lines. Data results are 



an August 19 76 survey by P. Knuth 

 (Edinboro State College). 



Figure 5. Shore-normal profiles off Presque Isle. 



II . RESULTS 



1. Primary Geologic Units . 



Analyses of the seismic profiles and the cores show that four major geo- 

 logic units are present in the study area: (a) Devonian age shale bedrock 

 that comprises the eastern Erie basin and underlies the entire area; (b) 

 Pleistocene age glacial sediments that include a complex assortment of till, 

 stratified glaciof luvial debris, and lacustrine silt and clay from ancestral 

 lakes; (c) beach and dune sand deposits that comprise the offshore ridge and 

 the Presque Isle platform and peninsula; and (d) soft organic muds that cover 

 much of lake floor in deeper areas and mantle the older deposits. 



