Page:The Journal of geology (IA journalofgeology21894univers).pdf/186

altogether satisfactorily explained, although the deposits indicate that they were largely derived from crystalline rocks.

That the red sandstones and shales of the Jura-Trias (Newark Formation) which adjoin the coastal series upon the landward side have not been the source of the materials is a striking fact, and one which has been largely commented on in the past. By some it has been supposed that an area of crystallines must have existed to the eastward to afford the materials for the deposits under consideration. A study of the drainage of the Jura-Trias belt which separates the coastal formations from the area of crystalline rocks beyond, is of interest, however, in showing the probable extension of the coastal deposits quite over the red sandstones and shales of the Jura-Trias to the border of the crystalline region and at the same time affords a sufficient explanation for the absence of sediments derived from the Jura-Trias itself. The evidence for this has been recently presented by Davis^[1] in the National Geological Magazine, and the reader is referred to the article for a fuller explanation of the subject.

Accepting the explanation of Davis as highly probable we may look for the source of the land-derived materials out of which the greensand deposits are formed, in northwestern New Jersey, eastern Pennsylvania and southeastern New York, in a portion of that tract of crystalline rocks which stretches along the eastern side of the continent. A separation of the mineral constituents of the greensand deposits shows a preponderance of both the constituent and accessory minerals which characterize those rocks. It seems conclusive, therefore, that the area mentioned was the source of the materials for the greensand deposits of eastern New Jersey.

The geological formations of New Jersey early attracted the attention of geologists, and Professor Peter Kalm^[2] of Sweden,