In the western half of Long Island, where the Lloyd has been explored by many wells and 

 test holes, it has been found to be comparatively uniform. From this evidence alone one might 

 suppose that it extended with little change under the eastern half of the Island as well. The 

 Orient Beach State Park well, (S 189), the one well which has penetrated the Lloyd in eastern 

 Suffolk County, and for which a reliable log is available, shows conditions however which are 

 unique. Bedrock, here deeply weathered, is overlain by only 14 feet of sand and gravel. Above 

 this is 50 feet of nearly solid clay, and above this 50 feet more of clayey sand with but a little 

 gravel. On top of this lies 100 feet or so of clay which, without doubt, belongs to the clay 

 member of the Raritan formation. The Lloyd sand in this well may be represented by the 

 bottom 14 feet and no more. A second interpretation would place the next-overlying 100 feet 

 of clay and clayey sand also in the Lloyd. This seems the more reasonable interpretation of 

 the two, since, along the strike, variations in the type of material present in the deposits seem 

 to be more marked than variations in their thickness. 



The two deep wells drilled at Brookhaven National Laboratory in central Suffolk County 

 penetrated about 250 feet of mixed and interbedded sand, gravel and clay which in this area 

 make up the Lloyd sand. This material resembles that in the type locality more closely than 

 it does that found at Orient Point, but is in a sense intermediate between them. It contains 

 more clay, both as separate beds, and intermixed with the sand and gravel, than is found in 

 western Long Island, but less clay than was found at Orient Beach. The second Brookhaven 

 well, although gravel packed and carefully developed, yielded relatively little water, about one 

 third as much as has been obtained from similar Lloyd wells farther west in Nassau County. 



These are not enough data to give a clear picture of the underground conditions, and so, 

 lacking the facts, no reliable historical interpretation can be made. Speculation however sug- 

 gests that the Lloyd sand was deposited by a river which followed roughly the course of the 

 present Hudson River. The shore line then was some distance to the south and east of its 

 present location, and the Lloyd sand was deposited above sea level on the coastal plains of 

 that time. Such a deposit would be coarser and would contain less clay near the principal 

 channel of the stream. If this were the case then the poor water yielding qualities of the 

 Lloyd observed at Orient Beach and at Brookhaven are not due to local variations in texture, 

 but are representative of the eastern half of Long Island. 



The Lloyd sand grades upward into the Raritan clay. The change may possibly be due 

 to a shift in the relative heights of sea and land, but the plant fossils in the clay, which 

 suggest strongly that this too was deposited on land, — or at least not in the sea itself, — 

 would rule out the actual invasion of the area by the sea. More likely then would be a change 

 in the carrying power of the streams, or a change in the material available to them for trans- 

 portation. Possible causes of the former would be a decrease in average rainfall or in the 

 intensity of storms, a tilting of the land, or a slight down-folding of the broad arch whose 

 formation had initiated this erosion cycle. W. 0. Crosby (11) felt that all, or at least most of 

 the changes in grain size, from clay to sand to gravel, and back again, were the result of 

 changes in relative sea level. To this the present writer does not agree. 



The Raritan clay itself ranges from 50 to 300 feet in thickness and is composed for the 

 most part of tough, compact, banded clay of many colors but predominantly gray and red. It 

 contains some sand layers and very locally, if the well logs are to be believed, a substantial 

 proportion of sand. These variations in thickness and composition are important, since they 

 affect very markedly the extent to which the clay member of the Raritan formation seals the 

 Lloyd sand. This clay seal both tends to prevent water from percolating into the Lloyd from 

 above and traps in it such water as it may contain. But the clay seal is far from perfect for 

 water descends from the Magothy as is clearly shown by the shape of the piezometric surface 

 of the water contained in the Lloyd. This surface follows closely the shape of the piezometric 



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