1989 Articles

A middle Carnian to early Norian (~225 Ma) paleopole from sediments of the Newark Basin, Pennsylvania

Witte, William K.; Kent, Dennis V.

Paleomagnetic study of the middle Carnian Stockton Formation, upper Carnian Lockatong Formation and the lower part of the Norian Passaic Formation from 24 sites along 3 traverses perpendicular to strike in the Newark Basin of eastern Pennsylvania shows that two hematitic magnetizations can be isolated from these rocks. Thermal demagnetization experiments reveal a distributed unblocking temperature (typically 300 to 680°C) magnetization with uniformly downward and northerly directions, and a high unblocking temperature (660°C and above) magnetization with shallow northerly (normal polarity) and southerly (reversed polarity) directions. On the basis of a correlatable magnetic polarity stratigraphy between 3 traverses spanning 40 km along strike, and within-site directional scatter similar to that expected from paleosecular variation, the high temperature magnetization was most probably acquired at or near the time of deposition. The pole calculated from the high unblocking temperature magnetization (53.6°N, 101.6°E, A95 = 4.8°) is consistent with other Late Triassic poles and indicates a paleolatitude of 3.8°N ± 3.0°. The lower unblocking temperature magnetization is an overprint acquired at about the same time as the Jurassic Newark trend igneous N2 pole magnetization.