Examination of drill cores and cuttings from water wells and test borings in southern Suffolk County, N.Y., has disclosed the presence of a marine fossiliferous greensand unit in the upper part of a thick sequence of deposits formerly referred to as the Magothy (?) Formation of Late Cretaceous age. The microfauna, mineralogy, and general stratigraphic position, however, indicate that the greensand beds are correlative with the Monmouth Group of New Jersey; hence, the same name should be applied to the Long Island beds. The greensand beds contain moderate to large amounts of glauconite, are about 50-200 feet thick, and dip southeast about 30 feet per mile. Seventy-two different species of Foraminifera and a few Ostraeoda were identified and most of them are illustrated in the report. Underlying transitional beds of post-Raritan Cretaceous age are thought to be part of the Matawan Group and Magothy Formation undifferentiated. The report is a byproduct of cooperative groundwater investigations in Long Island.

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In 1962 it was decided to reevaluate the effect of groundwater flow on the concentration of hexavalent chromium and cadmium heavy‐metal contaminants. U.S. Geologic Survey (USGS) joined Nassau County, New York, as an active participant in this study. Test wells were located on the streets where previous investigations had taken place. These streets, at right angles to the direction of groundwater flow, are just south of the recharge basins from which the contamination originated. The data accumulated were therefore comparable with those obtained in previous studies. Ninety test wells were constructed in and near the contaminated slug. The wells were driven by guiding a 200‐lb weight on top of a 5‐ft. coupled section of 1 1/4 in.‐diameter drive pipe with a standard point. The wel1s ranged in depth from 8‐75 ft; the final depths of the drive points were sufficient to determine the thickness of the contaminated slug at each location. Water samples were collected at 5‐ft. intervals below the water table. These samples and others periodically collected from the recharge basin and Massapequa Creek were analyzed for hexavalent chromium and cadmium.

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Clay member-Suffolk County Magothy (?) formation Magothy (?) formation-Kings County Magothy (?) formation^Queens County Magothy (?) formation-Nassau County Magothy (?) formation-Suffolk County _ 20 Jameco gravels Jameco gravel-Kings County Jameco gravel -Queens County Jameco gravel-Nassau County Jameco gravel-Suffolk County Gardiners Clay Gardiners clay-Kings County Gardiners clay -Queens County Gardiners clay-Nassau County Gardiners clay-Suffolk County Upper Pleistocene deposits