Distribution of surficial sediments in Ohio's nearshore (Lake Erie) as interpreted from sidescan sonar and 3.5 kHz subbottom data

Abstract

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.

Climate-Induced Changes in Rates of Headland-Beach Progradation along the Southern Coast of Lake Erie

“…Regional mapping of the southern Lake Erie nearshore shows that sandy sediments are largely absent or form only thin veneers atop bedrock outcrops along the lake bottom, while the studied headlands represent two of a few areas of significant net deposition (Figure 1; Fuller, 1996;Holcombe et al, 2003). Considering the nature of this sediment supplylimited nearshore, environmental changes (i.e.…”

“…Tillcovered bedrock bluffs that extend up to~20 m in elevation above lake level define much of the southern shoreline; these sedimentary bedrock outcrops consist of friable Upper Devonian siltstones and shales (Holcombe et al, 2005;Pincus, 1953); extending lakeward beneath the water column, these rock units are frequently exposed at the sediment-water interface among isolated pockets of gravel and sand ( Figure 1b). This geologic framework dominates the sediment-deprived nearshore regions along most of the south-central Lake Erie coast and should therefore have no differential influence on headland-beach evolution (Fuller, 1996;Holcombe et al, 2005). Furthermore, post-1900 hard structure-related headland deposition represents a recent continuation of sedimentation onto already existing promontories that sequestered substantial sediment packages throughout the Holocene.…”

“…Given the very low sediment availability within nearshore regions here (Fuller, 1996) and sediment supply largely dependent on bluff-erosion rates (Carter, Benson, and Guy, 1981;Carter and Guy, 1988), the two headland sites should react sensitively to environmental changes involving lake levels, coastal hydrodynamics, winterice cover, and precipitation patterns.…”

“…Fetch across the lake, which is largest for SW winds, helps generate significant wave heights up tõ 2.0 m and current conditions that allow only the coarsest sediments to sequester along the high-energy southern Lake Erie coastline (Kang, Sheng, and Lick, 1982;Khandekar and Swail, 1995). Shoreline and nearshore regions here are extremely sediment deprived, and only thin, patchy veneers of sand and gravel are found covering bedrock exposures (Fuller, 1996;Figure 1b). The absence of substantial nearshore-sediment budgets is attributed largely to low clastic riverine input (Ohio Department of Natural Resources, 2007).…”

Historical Sediment Budget (1860s to Present) for the United States Shoreline of Lake Erie

“…In low-relief areas of western Lake Erie, modern sediments of variable thickness overlie Pleistocene glacial drift (Fuller 1996;Ohio Department of Natural Resources 2007). Beaches are composed of sand, gravel, and shell hash.…”