(12) Area Ml. Near tlie southern border of the Fernandina grid is a large 

 triangular-shaped closed depression in whicii cores indicate the top of the type M sediment 

 layer outcrops or is at shallow depth (< 5 feet) and thus accessible to dredges. Type M sand 

 in cores from this area is generally of coarse texture and has a dolomite silt matrix. 



(13) Area M-2. Core 190 is in a small closed depression and contains 11 feet of 

 type M sediment which outcrops at the core site and may be exposed throughout the 

 depression. Tlie core contains an admixture of coarse quartz sand with a dolomite silt 

 matrix. 



(14) Area M-3. An extensive area covering a broad, ridge-Uke feature with subtle 

 topographic expression off Jacksonville appears to be underlain by type M sediment. Cores 

 in this area generally encountered the sediment at —3 feet or less, and outcrops probably 

 occur in many places. An ancient channel bisects the area and along the channel course 

 type M sediment is deeply buried under channel fill. This part of the channel containing the 

 fill may provide suitable sand; the area has been delineated area A-5. 



The type M sediment found in area M-3 is composed mostly of medium to coarse quartz 

 sand in a silty matrix consisting of particulate finely divided organic matter or dolomite silt. 



c. St. Augustine Grid to False Cape. Throughout most of this stretch of coast the 

 shoreface and innermost ramp are mantled by silty fine type F sands (Figs. 41, 42, and 43). 

 Because of the fineness of the characteristic surficial deposits this zone, which extends 

 about 5 nautical miles offshore, is unpromising for potential beach fill material. Farther 

 offshore clean type A quartz sands are common on topographic highs. Elsewhere in the 

 offshore zone the sediment is heterogeneous; fine shelly quartz sand and fine silty sand are 

 particularly common in the surficial layer, and sandy shell hash and clay are common in the 

 shallow subsurface. Near the southern end of the study area surficial sediments are shelly 

 quartz sand and shell hash typical of type A sands in shoals around Cape Canaveral (Field 

 and Duane, 1974). 



There are no known exposures of type M sediment in the St. Augustine— False Cape 

 section. Absence of type M material in cores from this area supports seismic reflection 

 evidence that the top of the type M sediment layer is covered by 15 feet or more of 

 overburden south of St. Augustine. 



(1) A-8. Clean tjpe A sand over 10 feet thick with mean diameters ranging from 

 0.287 to 0.308 millimeters (1.7 to 1.8 phi) was recovered by core 140 in the center of this 

 linear shoal (Fig. 40). Prospects for locating suitable borrow areas in this ridge are judged to 

 be very good. If the entire ridge is of suitable material the estimated reserve is 39 X 10^ 

 cubic yards. 



(2) Area A-9. Core 147 in this irregular low relief shoal area contained over 11 feet 

 of clean uniform medium sand with an average mean diameter ranging from 0.287 to 0.308 

 millimeters (1.7 to 1.8 phi). Suitable borrow areas should exist near core 147 and probably 

 occur throughout the main ridge area; probable reserves of sand are estimated to be 

 61 X 10^ cubic yards. 



96 



