Manhasset gravels here referred to as Manhasset formation. Formation consists of glacial deposits, 150 to 250 ft thick, and is correlated with Illinoian stage of Mississippi Valley. Divided into ascending Herod gravel member, Montauk till member, and Hempstead gravel member. Contacts between members are unconformable. Hempstead and Herod are similar lithologically. Both consist of sandy gravels with good proportion of pebbles, mainly of granitic rocks. In some places members are prevailingly sandy, and in others chiefly gravel. Locally, the lithologic change is abrupt vertically and horizontally. Generally, members contain more sand toward base and more gravel toward top. In the more normal phases the deposits consist of an alternating thin layers of sand and gravel, the whole having a gravelly aspect. Hempstead is 0 to 75 ft thick and occurs on Long Island and on Plum, Gardiners, and Robins Islands. Hempstead underlies glacial deposits of Wisconsin age. Time of deposition called Hempstead substage.

Source: GNU records (USGS DDS-6; Reston GNULEX).

Authors review usage of Fuller (1914) who applied the name Manhasset with its three members (Hempstead, Montauk, and Herod) to the Columbia formation of Woodworth. Fuller classified this formation as being older than the Vineyard erosion interval and assigned the Manhasset to the Illinoian. This report assigns the Manhasset of Fuller (including debris flows) to the Kansan(?), and interprets its origin as deltaic, deposited in Lake Long Island dammed on the south in part by pre-Ronkonkoma terminal-moraine ridge. Manhasset is older than Gardiners Clay (Yarmouthian).

Source: GNU records (USGS DDS-6; Reston GNULEX).