No abstract

ABSTRACT. A multi-disciplinary, multi-institutional research team evaluated a broad range of physi

Side scan sonar and 3.5 kHz subbottom data were collected along 1,570 km of tracklines from 1993 to 1995. Interpretations of the data were used to map the distribution of nearshore surficial sediments between 500 meters and 3.5 kilometers from shore. Sediment distribution mapping was extended to shore using interpretations of surficial sediments from bathymetric profiles that were run in the 1970's from the shore out to 600 m. Interpretation of the side scan sonar and 3.5 kHz subbottom records delineated five acoustic backscatter classes that generally correlate with five different sediment types. From the Ohio-Pennsylvania state line to Fairport Harbor and from the west side of the Cleveland harbor complex to Ceylon, rock dominates the lake bed of the inner half of the mapped area and mud or sandy mud dominates the outer half of the mapped area. The inner half of the mapped area from Fairport Harbor to Euclid is dominated by till and lake clays and the offshore half is dominated by sand. Because of the nature of side scan sonar to "see" only the surface, some of the sand and sandy mud areas may be thin veneers over till and lake clays deposits. Data interpretations of the 3.5 kHz reflection record re-enforce the veneer interpretation. From Euclid to the west side of the Cleveland harbor complex, the bottom is mostly sand and sandy mud exposed in about equal distribution. The inner quarter of the mapped area from Ceylon to Marblehead is dominated by mud, sandy mud, and sand; there are only small outcrops of till and lake clays or rock. Mud predominates in the outer three quarters of the mapped area. The short section of coast from Marblehead to the west side of Catawba Island is a complex of all bottom types with none dominant. The reach from the west side of Catawba Island to Little Cedar Point (near Toledo) is dominated by sandy mud and mud in the outer three quarters of the mapped area and till and lake clays along the inner quarter. Here again, the sediment cover over the till and lake clays is probably a thin lag deposit as suggested by interpretation of the 3.5 kHz data. The nearshore profiles show that narrow deposits of sand exist along most of the shore edge of the mapped area and in some areas, are exposed as beaches. Some general correlations seem to exist between the nearshore sediment distribution and the bluff recession. Where the bluff is rock recession rates are low and there was little correlation with the nearshore sediments. Where the bluff is till or till related deposits that are erodible, the recession rates seem to be lower where rock dominates the inner half of the mapped area.