plant and animal fossils which suggests deposition in a climate about as warm as that found on 

 Long Island today. In fact by far the greater part of the fossils are identical with those living in 

 this area today, a fact which makes the deduction concerning the climate relatively certain but 

 makes it impossible to date the Gardiners clay as belonging to any particular subdivision of the 

 Pleistocene. However the general similarity of the flora and fauna of the Gardiners in the very 

 few but widely scattered localities where they have been studied suggests that all the samples 

 believed to be Gardiners clay came from the same interglacial period, even if it is impossible to 

 say which one. 



In Western Long Island, and probably over the rest of the island as well, the upper surface 

 of the Gardiners clay is 50 feet or more below sea level, except locally where it has been folded 

 by the push of later icesheets and stands higher. The obvious explanation for its origin is then 

 as follows. With the retreat of the ice which directly or indirectly deposited the Jameco gravel, 

 the volume and force of the streams from the mainland decreased and they either were deprived 

 of the coarse sand and gravel which the ice had supplied to them, or lacked the ability to trans- 

 port it. At the same time the melting ice cap supplied water to the ocean, raising its level, an ef- 

 fect which is widely recognized from studies in many parts of the world. 



It is not possible to say with assurance if the Jameco gravel was deposited above or below 

 sea level but its general composition and distribution suggests that it was deposited above. The 

 Gardiners clay however contains marine and brackish water fossils and it was deposited prob- 

 ably in shallow bays so that sea level, when it was formed, must have been something less than 

 50 feet lower than at present, and in all probability more than 50 feet higher than it had been 

 in Jameco time. This inferred rise could of itself account for the quiet water in which the Gar- 

 diners clay was deposited for any change in sea level, up or down, which brings the sea in 

 contact with a gently sloping shore line results in the formation of off shore bars and barrier 

 beaches. Such a barrier beach, formed after the most recent post glacial rise in sea level, fringes 

 the southern shore of Long Island today, where it encloses a series of large bays. 



Similar bays, at a lower level and quite possibly larger, may well have existed along the 

 south shore of Long Island, in Gardiners time. The source of the clay itself is something of a 

 question. With sea level lowered 50 feet, an appreciably larger area of Long Island would be ex- 

 posed to erosion than is the case today, but it is difficult to see how this area could have supplied 

 the 50 foot thick clay blanket of the Gardiners, since so much of the core of the Island is sand. A 

 possible additional source of clay was the Hudson River, which need not have emptied directly 

 into the bays in order to have furnished them with sediment. All that would be required would 

 be a connection between the lower Hudson and the bays or quiet water where the Gardiners 

 was accumulating. Tidal action then would suffice to sweep in mud, and possibly, in time, dis- 

 tribute it as far east as the Nassau-Suffolk County line. Sources for the material of the Gardin- 

 ers clay farther east in Suffolk County are harder to find. A red color of some of the clay here is 

 responsible for the suggestion (15) that it came from the Connecticut Valley where the Triassic 

 bedrock is red. Recent brief studies of the Gardiners however suggest that the red clay associ- 

 ated with it is not part of the Gardiners clay itself. These studies also suggest that the Gardin- 

 ers clay in the vicinity of the Brookhaven National Laboratory has a thickness of only about ten 

 feet, indicating a volume of material whose origin is less difficult to account for. 



In several places the Gardiners clay contains the green mineral glauconite, the character- 

 istic constituent of the Cretaceous green sand beds of New Jersey. This mineral is believed to 

 form commonly in quiet deep ocean water, at many times greater depth than was the Gardiners 

 clay. Pleistocene glauconite is uncommon in any case. It is no easier to imagine how the mineral 

 could have been derived by reworking from the Cretaceous beds, since on Long Island the Cre- 

 taceous contains very little glauconite. This however is the preferred explanation and suggests 

 the Cretaceous beds as also the source for much of the other material in the Gardiners. 



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