. ••• L 





-1 ■ 1 



30" Ti' 



5/. Clair River ) 

 MICHIGAN y~xj 



ONTARIO ^ 



'^^ ^ J^^' 



^ LAKE ERIE A 



SJUDY AREA ^^^[^^^^^^^--'^nneauf 

 ■^' V y/^ Foirport Harbor 



• — ' ^^ ) Buffalo 



Long Pf. ,^ / 

 ^--^ y^Ounkirk 

 y^ rjEW YORK 



Erie i «°- 



PENNSYLVANIA 



if 



Toledo \^/^;^\. 



-^^ ^^F^ ' 1 J 



II'' 



M r 1 e h e d -^C^^^^-^\[^ 

 SondusKy *"■ 



■^;;iy^ F^«l|'cieveland 1 q 



i 1 



50 Stotute Miles 

 1 1 1 1 





QI^IQ 20 40 60 80100 Kilometers 1 



Si' 



82« 8I» 



1 1 



80" 79" 



1 1 



Figure 1. Lake Erie study area, from Conneaut to Marblehead, Ohio. 



in Figures 2 to 7 . Data collected for this study consist of 576 kilometers of 

 seismic reflection trackline profiles, taken in August 1977, and 58 vibracores 

 ranging from 0.7 to 6.1 meters long, taken in August 1978. About 23 percent 

 of Ohio's open lake part of Lake Erie (7481 square kilometers) was covered by 

 the seismic reflection survey between Conneaut and Marblehead. 



The survey data in this report were supplemented in places by previous DCS 

 work. Vertical control was obtained from National Ocean Survey (NOS) water 

 level gage data for Lake Erie; water depths are referenced to low water datum 

 (LWD) , which is 173.3 meters above mean water level at Father Point, Quebec 

 (International Great Lakes Datum (IGLD) , 1955). Mean lake level in both 

 August 1977 and August 1978 was about 1 meter above LWD. This study is basi- 

 cally reconnaissance in nature, as seismic line spacing and orientation and 

 core spacing density preclude a detailed evaluation of the bottom and subbottom 

 deposits. However, because of the relatively flat-lying nature of the deposits, 

 extrapolation between tracklines can be made with a fair degree of confidence. 



2. Field Procedures. 



a. Geographic Positioning System . A radar-type electronic positioning 

 system, the Motorola Mini-Ranger III, was used to determine position of the 

 research survey vessel during the seismic survey (phase I) and the vibracoring 

 (phase II). The system determines the position of the survey vessel with 

 respect to tv/o known reference points on shore and is restricted to line-of- 

 sight operation. The basic system consists of a master mobile unit mounted 

 onboard the vessel and two shore-based transponders. The master unit triggers 

 reply pulses from the transponders; each transponder pulse is received sepa- 

 rately and the elapsed time between the transmitted pulse and the individual 

 transponder reply pulse is converted to a measurement of distance. Each 

 distance (range) from the two transponders at the known shore stations is dis- 

 played in turn on the range console. This range information, together with 

 the known locations of the shore stations, is then trilaterated and plotted 

 on hydrographic charts to obtain the position (fix) of the survey vessel. 



