overlain in places bv type L sediment of early Pliocene age and underlain by probable 

 middle Miocene strata of the purple and white units it seems likely that this unit is of late 

 Miocene age. The foraminifera in some respects suggest relationship to late Miocene 

 Choctawhatchee Stage fauna but more detailed study is needed to establish any possible 

 relationship. 



Sediments *in tlie blue unit overlying the red reflectors are believed to include thin strata 

 of Pliocene, Pleistocene and Holocene age. The entire unit is quite thin, especially in the 

 northern part of the study area where it rarely exceeds 15 feet in thickness; in the south the 

 unit is up to 40 feet thick. Since the surveyed area is displaced eastward toward the south 

 the apparent thickening of this unit may indicate a general downdip increase in thickness 

 rather tlian "onstrike" southward thickening. JOIDES Hole No. 1 at 81°00'W. off 

 Jacksonville contains about 65 feet of post-Miocene sediment indicating an eastward 

 thickening of the post-Miocene deposits. This post-Miocene section is about 20 feet thicker 

 than the blue reflection unit at a comparable longitude in the southern part of the study 

 area. 



A structure contour map on the surface of the Ingles Formation of the Ocala Group 

 (Vernon, 1951) shows that under east Florida, Ocala Group strata rise southward from the 

 Georgia border to a broad truncated high situated westward of Daytona Beach. At the 

 summit of the liigh Vernon found a closed fold truncated on the west by a fault. He called 

 this feature the Sanford high and hypothesized that before disruption by faulting and 

 erosion the liigh may once have extended westward across the peninsula. Puri and Vernon 

 (1964) believe that the structural movement which formed the Sanford high took place in 

 early Miocene time. 



A comparison between Vernon's (1951) map on the Ingles Formation and the green 

 reflector (Fig. 15) shows similar structural trends with both surfaces rising southward to a 

 broad high near Daytona Beach. This suggests that strata involved in the stmctural 

 development shown by Vernon's map and by the green reflector are continuous and that tiie 

 liigh off Daytona Beach is possibly an eastward prolongation of the Sanford high. 



A second prominent feature of the subbottom strata is the abrupt steepening in eastward 

 dip of the green reflector from a slope of about 1 on 400 to 1 on 50 occurring south of the 

 Volusia-Brevard County line (28°37'N.). Presumably this feature is more extensive but lies 

 too far offshore elsewhere in the study area to be intersected by survey Hues. However, 

 south of Cape Canaveral the slope appears to extend as far as Fort Pierce (Meisburger and 

 Duane, 1971). Total depth of the steep slope in the green reflector is unknown but it 

 extends from about -180 to -200 feet MLW to at least -450 feet MLW, the maximum 

 depth of coverage of available seismic reflection profiles. Whether this slope is of structural 

 or erosional origin cannot be ascertained from available data. 

 2. Sources of Inner Shelf Sediments. 



a. Surface and Near-Surface Tertiary Deposits. The relative occurrence and abundance 

 of surface and near-surface deposits of Tertiary age on the north Florida inner shelf are of 



72 



