Table 1. Generalized stratigraphy of Long Island (from Williams, 1976) 



Era 



Period 



Epoch 



Unit 



Character and origin of deposits 



Cenozoic 



Quaternary 



Holocene 

 (recent) 





Quartzose sand, beach and dune deposits, and fine- 

 grained lagoon sediments 



Pleistocene 



Harbor Hill Moraine 

 Ronkonkoma Moraine 



20-foot clay 



Gardiners Clay 



Jaraeco Gravel 

 Mannetto Gravel 



Ground and terminal moraine; stratified deposits 

 of sand and gravel, cobbles, and silt and clay 



Grayish-green, silty clayey, glauconltic fine sand 

 (marine) 



Grayish-green, silty clay (marine) 



Fine to very coarse-sand and gravel; scattered 

 beds of silt and clay (fluvial or glacial outwash) 



Mesozoic 



Cretaceous 



Upper 

 Cretaceous 



Monmouth Group 

 Matawan Group 

 Magothy Formation 



Raritan Formation 

 Raritan Clay 



Lloyd Sand 



Quartzose sand interbedded with silt and clay 



Silty, sand, brownish-gray clay with thin beds of 

 sand and gravel 



Quartzose fine to coarse sand and gravel; inter- 

 bedded clay and silty sand is common 



Precacbrian 

 or Paleozoic 







Crystalline Bedrock 



Undifferentiated, consolidated, metaaorphic 

 granite 



SEA LEVEL- 



VERTICAL EXAGGERATION X 20 



Figure 3. Geologic cross section from the south shore of Long Island at 

 Fire Island north across Long Island Sound to the Connecticut 

 mainland (modified from De Laguna, 1963). 



15 



