County. Crosby (1910) considered the Mannetto to be o£ probable Pliocene 

 age, whereas Fuller (1914) thought the deposits were remnants of an early 

 Pleistocene outwash sheet. Suter, De Laguna, and Perlmutter (1949), 

 Swarzenski (1963), and Lubke (1964), either rejected the idea that the 

 Mannetto is of Tertiary age or failed to support either interpretation 

 of the age for this unit because of a lack of definitive evidence. 



Tlie Jameco Gravel (Table 1) is considered by many Long Island stra- 

 tigraphers to be an early Pleistocene deposit. The Jameco underlies the 

 Mannetto Gravel in parts of western Long Island but in other areas where 

 it occurs as stream channel fill the Jameco unconformably overlies the 

 Magothy Formation or older strata. In extreme northwestern Long Island, 

 the Jameco directly overlies metamorphic bedrock. The lithologic char- 

 acter of the Jameco varies considerably over wide areas; its composition 

 is apparently dependent on the nature of its source rock. In western 

 long Island the Jameco is composed of fresh well-rounded fragments of 

 various igneous and metamorphic rocks with varying amounts of shale and 

 sandstone. However, farther east the principal parent rocks were appar- 

 ently Cretaceous formations, resulting in less compositional variety 

 (Swarzenski, 1963). Fuller (1914) felt the Jameco Gravel was an outwash 

 deposit resulting from melt-water discharge which accompanied a pre- 

 Wisconsin continental ice sheet which had its ice front north of the Long 

 Island mainland. The Jameco, usually between 100 to 200 feet (30.5 to 61 

 meters) thick, is found along the northern edge of Long Island or buried 

 in the deep channels which underlie the reentrant bays on the northwestern 

 coast of Long Island (Swarzenski, 1963). Age of the Jameco is still un- 

 known, and the only certainty is that it is pre-Sangamon; however, it is 

 thought to be of Illinois an age. 



There is a sharp lithologic break between both the Upper Cretaceous 

 formations and Jameco Gravel and the overlying Gardiners Clay. Present 

 data suggest the Gardiners Clay is of Sangamon age, deposited under a 

 low-energy lagoonal-estuarine environment, possibly similar to present 

 conditions in Great South Bay, Long Island (Weiss, 1954). The Gardiners 

 Clay is characterized by dark gray or green-gray glauconitic silty clay 

 with lenses of sand and gravel. Some of the silt layers contain rich 

 assemblages of foraminifera which may be correlated over a significant 

 area by the microfossil content (Donner, 1964). According to Fuller 

 (1914), the maximum elevation of occurrence for Gardiners Clay, excluding 

 elevation due to ice-pressure deformation, is 50 feet (15.2 meters) below 

 present sea level, which may indicate that sea level was at least 50 feet 

 lower than present in the immediate area before the commencement of 

 Wisconsin glaciation. The thickness and areal continuity of the Gardiners 

 Formation vary greatly; Athearn (1957) identified Gardiners -type material 

 from a deep boring sample, retrieved in connection with site foundation 

 studies for a proposed Air Force Texas Tower, 60 miles (96.5 kilometers) 

 south of Moriches Bay, Long Island. The sample was retrieved 70 feet 

 (21.3 meters) below sea floor (overlain by coarse sand and fine gravel) 

 under a water depth of 185 feet (56.4 meters). Recent studies by 

 Gustavson (1976) suggest that the environment of deposition for the 

 Gardiners Clay was considerably more complex than previously thought. 



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