Attempts to trace the Gardiners clay and to identify it in well records or exposures in 

 other parts of Long Island are greatly hampered by the complex and little understood history of 

 this period, and by the inadequacies of the available data. So far we have no evidence of any 

 other interglacial deposit besides the Gardiners clay, so that any fossiliferous material of Pleis- 

 tocene age overlain by later glacial deposits may be called Gardiners. Shells are not always re- 

 ported in the well logs however, even where they are known to be present, and at many localities 

 the only fossils in the Gardiners are microscopic remains the driller could not have seen. The 

 varved clays as well as other records show that there are glacial as well as interglacial clays 

 in the Pleistocene, particularly in eastern Suffolk County, and until much more work has been 

 done the identification of the Gardiners is not possible in most well records and even in some 

 outcrops. 



Along the south shore of western Suffolk, and westward into Kings County, an interglacial 

 clay can be identified in many of the reliable logs of sufficient depth, although the continuity and 

 extent of the deposit is open to question. The best data are for the western end of the Island, 

 where the formation can be mapped with some detail, a peculiar circumstance since this 

 cannot be done in the vicinity of the type locality. 



Although these problems of the true age and proper correlation of the Gardiners clay and 

 related Pleistocene deposits may seem academi c, they are in fact of some importance. In many 

 areas, the Gardiners marks the bottom of the water table aquifer, and is the lower limit of the 

 highly permeable glacial deposits. Below it lie the less permeable sands of the Magothy for- 

 mation which contain artesian water, differing in static head and in composition from the 

 water in the higher levels. 



The Gardiners clay grades upward into the Jacob sand, a formation which is not easy to 

 identity in well logs, and the distribution and history of which are therefore poorly known. 

 The best surface exposures of the formation are in the bluffs and beaches of the north shore, 

 particularly in the eastern half of the island. It appears to mark the transition from the clay 

 of the warm interglacial period which precedes it to the sand and gravel of the glacial outwash 

 which overlies it. It is possible that the source of the material was on the mainland, since some 

 feldspar, biotite, hornblende and other mineral grains are present which could not have been 

 derived from the underlying Cretaceous deposits. The silt and sand in the Jacob could not have 

 been carried across any distance of open water, so that the depression of Long Island Sound 

 must have been largely filled in. There is a suggestion therefore that the Jacob sand extended 

 from the mainland on the north, south to the hills which form the present day backbone of Long 

 Island, perhaps even farther south some distance toward the sea. The Jacob sand in turn grades 

 upward into the Manhasset formation without any marked break. 



Along the peninsulas of the north shore, where it is best developed, the Manhasset forma- 

 tion is 150 to 250 feet thick and is largely composed of beds of sand and gravel. These were 

 undoubtedly deposited as glacial outwash since there is a well developed glacial till, the Mon- 

 tauk till, present in the middle of the formation. How far south on the island the ice reached is 

 not known, but its limits apparently corresponded roughly with those of the later ice advances. 

 The till cannot be traced in well records, although it has been recognized in a few logs, and un- 

 successful attempts have been made to outline its distribution. This till is not thick enough, 

 extensive enough, or impermeable enough to offer any serious obstacle to the downward move- 

 ment of the ground water, although locally it may form some of the perched water tables found 

 along the north shore of Long Island. 



The Manhasset formation forms the great bulk of the material above sea level north of the 

 hilly central strip of the island. In the central hilly strip itself, where the underlying Cretaceous 

 beds rise 200 feet or more above sea level, the Manhasset is much thinner, and its contacts with 



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