sources in Figure 2. Core coverage is fairly well distributed along the 

 entire Long Island south shore, around Montauk Point, and in the Gardiners 

 Bay and Block Island region o£ eastern Long Island. Maximum coverage sea- 

 ward varies from 3 miles (4.8 kilometers) to about 12 miles (19.3 kilo- 

 meters) with an average limit of about 4 miles (6.4 kilometers). Based 

 on examination of these sediment data, the sea floor of the inner shelf 

 region can be characterized by five distinct sediment lithologies. 



1. Primary Sediment Classes . 



a. Sediment Type I . This sediment consists of generally clean, fine 

 to mediiim to coarse (0.125 to 1 millimeter; 3 to phi) white, quartz sand 

 (Eig. 18) mixed with rounded pea gravel (2 to 15 millimeters; -1 to -4 phi) 

 and distinctive green or black grains of sand and silt-size glauconite. 

 Sediment type I is restricted to the sea floor corridor which intersects 

 the shoreline near the Fire Island Inlet and extends southwest toward Long 

 Branch, New Jersey. The northwestern (inshore) boundary of the region is 

 clearly defined by cores V-5 and V-17 in Figure 9, and appears to mark an 

 abrupt transition into fine to medium sands containing little or no glau- 

 conite. The southeastern (offshore) boundary is more arbitrary and may be 

 farther southeast than shown in Figure 17. Occurrence of glauconitic sands 

 in the cores appears to coincide on the seismic records with a Coastal 

 Plain erosion surface underlain by highly glauconitic strata (possibly the 

 Monmouth Group) covered by a variable thickness of an admixture of outwash 

 sand and residual detritus from marine erosion of the underlying Coastal 

 Plain substrate. Presence of the shallow Coastal Plain surface is also 

 evident in several of the Suffolk County (sewer outfall) cores (Fig. 9). 

 Williams and Duane (1974) reported that a Coastal Plain cuesta projects 

 southwest from the Long Island shelf, intersects the Hudson Channel, and 

 then projects toward the New Jersey coast on line with Shrewsbury Rocks, 

 which they showed from seismic evidence to be a bathymetric expression of 

 the Coastal Plain cuesta. Presence of this subsurface cuesta of glauco- 

 nitic strata across the inner shelf is matched by the overlying residual 

 shelf sediments which also contain high percentages of glauconite. 



b. Sediment Type II . Type II sediment (>0,5 millimeter; <1 phi) 

 consists of clean coarse sand and rounded pea gravel which is commonly 

 reddish brown (lOYR 7/4; Munsell Soil Color classification, App. A) in 

 surface coloration (Fig. 19). The material occurs primarily on the eastern 

 half of the Long Island shelf in discrete patches and appears related to 

 the proximity of the Ronkonkoma Moraine. This relation of sediment distri- 

 bution with proximity to glacial moraine deposits agrees with similar sedi- 

 ment distributions reported by McMaster and Ashraf (1973) for the southern 

 New England shelf. The westernmost surface occurrence of type II sediment 

 is in cores 34 and 35 (Fig. 2) seaward and east of Shinnecock Inlet (Fig. 

 17). Both cores exhibit clean medium to coarse sand with rounded pebbles 

 for their entire lengths of 10 and 10.5 feet (3 and 3.2 meters), respect- 

 ively. Core 24 (Fig. 2) contains type II sediment for the first foot below 

 the sea floor and then grades into fine to medium quartzose sand (type III 

 sediment). The shoreface region around Montauk Point is primarily type II 



52 



