surface of the water in the Magothy and of the water table, except in areas where there is 

 appreciable pumpage. Not enough detail is available however to define the chief areas of re- 

 charge, although much of it seems to take place in west-central Nassau and eastern Suffolk 

 Counties. 



The thickness of. the clay member of the Raritan formation increases as the formation 

 is traced down its dip to the southeast, but this thickening is very irregular. Part of this irreg- 

 ularity may be due to the difficulty of determining the contact between the clay and the Lloyd 

 sand. As reported in most wells this contact is gradational but covers a very short vertical 

 distance. In certain areas, however, there appear to be beds of sandy clay along the contact 

 which are described as clay in some logs and as sand in others. Since the contact between 

 the clay and the Lloyd is placed either above or below these sandy clays, depending on the 

 emphasis given in their description, an artificial irregularity may be given to this contact, 

 where perhaps none actually exists in nature. 



Irregular or random variations in the position of the upper surface of the clay member 

 of the Raritan formation occur where it is in contact with the so-called Magothy formation. 

 On Long Island the contact may not be everywhere gradational and it is quite possible that 

 there was a brief period of erosion following the deposition of the clay member of the Raritan. 

 In New Jersey it is known that there was such an erosional interval, which suggests that 

 following the deposition of the Raritan clay there was an uplift of the land. How great this 

 uplift may have been, how long it lasted, and how deeply the underlying clay was eroded are 

 so far matters of speculation. It is possible that during the erosional period streams locally 

 cut completely through the clay member of the Raritan formation and that these old channels 

 are now filled with Magothy sands which are directly in contact with the Lloyd sand. Permeable 

 channels such as these would permit downward percolation of water into the Lloyd sand, and 

 their existence has therefore an important bearing on the rate of recharge to the Lloyd sand, 

 and also the shape of its piezometric surface. 



The few logs which in the past have been interpreted as showing the Magothy formation 

 in contact with the Lloyd are however now held subject to other interpretations. There is in 

 fact not enough information at present to say how deeply the clay member of the Raritan 

 formation was eroded, if at all. The greatest single difficulty is in placing the contact between 

 the top of the clay and the Magothy beds. Not enough is known of the manner of the formation 

 of the clay to indicate whether it might be expected to locally contain sandy beds in appreciable 

 Bumber, particularly in its upper part, or whether the Raritan-Magothy contact should properly 

 always be placed on the upper surface of a considerable thickness of solid clay. In other words 

 it is possible that in those places where the clay member of the Raritan formation is believed 

 to be unusually thin or even lacking, that some of the overlying sandy clay belongs more 

 properly to the Raritan formation, and not to the Magothy as has usually been assumed. In 

 New Jersey, where the Raritan formation is extensively exposed at the land surface, the upper 

 part is commonly sandy and it shows abrupt changes in composition, from layer to layer. 



If the clay member of the Raritan formation was indeed formed in shallow fresh water 

 or on flood plains, then abrupt variations from its normal composition of pure clay might be 

 expected. The broad flats in which the clay was formed must have been crossed in places by 

 the streams and rivers which supplied the clay and along these channels sandy clay and sand 

 might well have been laid down. In fact, if the Raritan clay was indeed formed above sea 

 level, as its content of fossil leaves seems to suggest, it is remarkable that it does not show 

 even more variation in content than has been observed. 



This uncertainty as to the history of the Raritan formation means that there are three 

 possibilities, not mutually exclusive, by which water from the overlying formations could find 

 its way into the Lloyd sand. The simplest perhaps would be by seeping directly through the 



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