PLEISTOCENE GEOLOGY OF NASSAU CO. AND BOKOUGH OF QUEENS 631 



Fig. 7 A fold-fault in clays at southern end of Center 

 island in Oyster Bay harbor 



overlain by at least 20 feet of clayey sands passing above into 

 cleaner sand. These beds dip gently east. 



The second cut west shows more of tlie w^liite sands, dip uncer- 

 tain, overlain by glacial gravel with small boulders. Tlie third cut 

 west exhibits cross-bedded, white clayey sands, presumably Creta- 

 ceous, overlain by 10 or 12 feet of glacial gravels and sands with 

 small boulders. The section shows no dislocation. 



In the first of these sections the measured exposure is evidently a 

 part of the Columbia ; in the second cut, the glacial gravels mantle 

 the eroded surface of the pre-Pleistocene series, having been 

 deposited subsequently to the deformation and gullying of the beds. 

 These top beds, by their 

 boulders and lack of strat- 

 ification, as well as their 

 relation to the eroded 

 clays, evidently pertain 

 to the last drift. The 

 sections show, ho'wever, 

 that the Columbia man- 

 tles over and is wrapped about masses of the pre-Pleistocene series, 

 as previously stated on p. 622. Similar partial sections occur on 

 Great Neck near Manliasset. 



In the sand pits northwest of Port Washington, the pre-Pleisto- 

 cene clays are also involved in folds, giving rise to a structure, the 

 upper member of which is a gravel and sand bed of the Columbia 

 formation, itself clearly older than the sands of the Port Washing- 

 ton delta yet to be described (p. 64:Q). In this instance the axis of 

 the anticlinal structure lies north and south, and the dislocation 

 may be of a relatively late date, even so late as the time of forma- 

 tion of the delta named, when the ice lay deeply embayed along 

 the north shore of Manliasset neck and w^hen an easterly movement 

 in the mass might be expected, since the ice at this locality was on 

 the eastern margin of a glacial lobe at the mouth of the Hudson 

 valley. 



The deposit of sands and fine gravels forming the tabular hillock 

 whose frontage on Manhasset bay near Port Washington is known 

 as Tom point is a unique example of the deformation and erosion of 



