Page:The Journal of geology (IA journalofgeology21894univers).pdf/178
thin and of very narrow geographical extent. The deposits are largely fragmental, with here and there an admixture of carbonate of lime derived from the shells of organisms.
The most extensive section is afforded by the bluffs on the shores of the Raritan Bay, between the mouth of Cheesequake Creek and the Navesink Highlands. From this point the formation extends southwestward across the state, the best exposures being found along the stream channels entering the Delaware River from the east. Both along Crosswicks and Pensauken Creeks the strata are highly fossiliferous, at the latter locality over a hundred species having been identified. In the main the forms are the same as those in the overlying Navesink formation, although some are distinctive.
From the surface outcrops the Matawan formation has been estimated to have a thickness of 275 feet.
The most striking differences both in the character of the materials and the thickness of the beds, are shown by well borings along the line of dip. A recent boring at Asbury Park penetrated the Navesink formation (Lower Marl Bed) at 400 feet, beyond which for a distance of over 400 feet typical Clay Marls were encountered. From 750 to 780 feet glauconitic layers were found, while the deposits in general are finer and more regularly stratified than in the surface outcrops to the westward.
(Lower Marl Bed).—The lower Marl Bed has an extensive development throughout the region of the Navesink Highlands, in the vicinity of the village of Navesink, and along the north bank of the Navesink River, so that the name of Navesink formation may be with propriety employed.
Greensand forms the distinguishing feature of the deposits. The lower portion is frequently quite sandy, in this respect showing the change from the sandy layers of the upper portion of the Matawan formation, upon which it lies conformably, to the typical greensands of the Navesink formation. The upper portion again shows the presence of much land derived material; it is highly argillaceous and just at the top frequently arenaceous. The greensands along the thinned out western edge of the Navesink forma-