CHAPTER IX.

CLAY DEPOSITS IN SYSTEMS OLDER

THAN THE CRETACEOUS.

CONTENTS.

Triassic.

Devonian.

Silurian.

Cambrian and Ordovician.
Pre-Cambrian.

TRIASSIC.

The Triassic or Newark series in New Jersey consists chiefly of red shales and sandstones with some masses of trap rock. It has been described in detail in the Annual Reports of the State Geologist for 1896 and 1897. It forms a belt across the State between the Highlands on the northwest and the Cretaceous strata on the southeast, extending from the New York State line between Suffern and the Hudson river, to the Delaware river between Trenton and Holland. The red shale where disintegrated forms a sandy, clayey soil of shallow depth. Locally this may accumulate in hollows as the result of wash from surrounding slopes and form clay beds of no great depth and limited extent, but so far as known beds of this description are nowhere used. The shale itself is for the most part rather gritty and not favorable for use in clay products, but locally it is fine grained and suitable for brick. It is so utilized at Kingsland, Bergen county, with apparent success. A few experiments on shale from other localities were made in the course of these studies, and although unfavorable and decisive so far as they went, they were not sufficiently numerous to test the formation thoroughly. Beds suitable for

brick or draintile are more likely to occur in the Brunswick shales, rather than in the Lockatong or Stockton subdivisions,1 and in the Brunswick shales rather to the south of a line from Passaic to Morristown than to the north of it, but there may be local exceptions to this rule.

At Pedrick's brickyard, Flemington, the basal portion of the clay used has been formed by the disintegration of the red shale beneath, and it is expected to use the less disintegrated material as soon as suitable machinery for crushing it can be installed.

The trap rock, where deeply weathered, gives rise to a yellow, more or less stony clay, usually containing many fragments of the less disintegrated portions of the rock. South of the drift-covered area, i. e., southwest of a line from Morristown to Perth Amboy, this residuary deposit often attains a thickness of several feet. Locally, it has been utilized for clay, as at Daniel's brickyard, on Sourland mountain, southeast of Lambertville (277), but it is full of bowlders, which are left in the pit (Pl. XXIV, Fig. 1).

DEVONIAN.

The Devonian formations of New Jersey are limestones, shales, sandstones and conglomerates. They occur in Sussex county along the Delaware river from Wallpack bend northward to the State line, and also in the Green Pond-Bearfort mountain region. In the former region they are chiefly limestones with some shales; in the latter, gritty shales, sandstones and conglomerates. In some states the Devonian shales are a source of valuable materials for paving brick, sewer pipe, drain and roofing tile, terra cotta, etc. In New Jersey, however, they are nowhere used, and in view of the unfavorable nature of most of the Devonian rocks, as well as the present inaccessibility by railroad transportation of much of the region covered by them, it is doubtful whether they will prove of any immediate importance.

SILURIAN.

The Silurian formations in New Jersey consist chiefly of sandstones, with a few limestone and shale strata. They occur in

E. Farry's yard, Matawan.