shoal the relatively flat bottom is approximately 40 feet MLW. Connection of Shoal A to 

 Chester Shoal by tliis slight high, and the general configuration and orientation of Shoal A, 

 indicates a morphological and perhaps genetic similarity between Shoal A, and Shoals B, C, 

 and D. (See Figure 5.) 



Isolated shoals and the cape shoals are actively changing in configuration by modern 

 nearshore processes. Direct evidence of active reworking of shoals is from sediment 

 characteristics and bathy metric profile data. Sediments collected from 10 feet subbottom 

 indicate recent abrasion and transport (discussed later in Section III, a). Comparison of 

 bottom profiles made in 1878, 1928, 1958, and 1965 by the Jacksonville District, Corps of 

 Engineers, show an historical change in shoal shape and location. Corps of Engineers, (1966) 

 maps of the 6-, 12-, and 18-foot depth contours show that all the shoals-have changed in 

 shape and are becoming shoaler. Cape shoals have broadened and thickened and, within the 

 18-foot contour, the isolated shoals have shifted slightly in a southeast direction. These 

 historical profile data indicate that since 1898 accretion has occurred on the south or 

 downdrift side of the cape shoals and erosion has occurred between the two shoals and west 

 of Southeast Shoal in Canaveral Bight. 

 2. Shallow Subbottom Structure, Cape Canaveral Grid. 



a. General. Dehneation of thicknesses of major units, and sonic penetration to 500 feet 

 subbottom by seismic reflection show that all strata have a consistent seaward dip. Units in 

 the column dip gently eastward and southeastward and are mostly conformable. However, 

 several hiatuses are evident, and result from planation and truncation of strata by a 

 transgressing sea. Deeper subbottom units generally dip more steeply than upper subbottom 

 strata; lower units have slopes of nearly 1 on 45 and upper units have slopes of less than 

 1 on 400. Internal reflectors between major seismic horizons are recognizable at times in the 

 upper subbottom, and they generally dip steeply seaward relative to the dip of the confining 

 reflectors. (See Figure 6.) 



Deep structure of the Florida Atlantic Inner Continental Shelf reported by Meisburger 

 and Duane (1969), showed the presence of two deep regional reflectors, both in the survey 

 area of this report. The higher of the two deep, major acoustic reflectors, (referred to as the 

 red horizon) dips gently from 130 feet in the center of the grid to —160 feet at the seaward 

 edge. The louver reflector, called the green horizon, drops from —120 feet near the shoreface 

 to nearly —500 feet in the grid center. (See Figure 6.) Horizons immediately beneath the red 

 reflector dip more steeply and are truncated by the red. Erosional nature of the horizon and 

 its depth and lateral extent suggests a probable age of early or mid-Pleistocene. Acoustic 

 horizons underlying the red horizon dip eastward at slopes up to 140 feet per mile (1 on 40) 

 and exhibit occasional broad undulatory folding. The green reflector shows signs of folding 

 and probable faulting. (See Figure 7.) Based on correlation of seismics with onshore well 

 data the green horizon is equivalent with the top of the Floridian artesian aquifer near the 

 pre-Miocene— Miocene contact. 



Above the red horizon and traceable over the grid area are two major shallow reflectors. 

 The lower of the two reflectors, called tlie yellow horizon, lies about 20 to 50 feet below 

 the sea floor; the upper one is termed the blue horizon, and lies 10 to 30 feet below the sea 

 floor. 



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