North American Jurassic Apparent Polar Wander: Implications for plate motion, paleogeography and Cordilleran tectonics

Abstract

Eight paleomagnetic poles are considered to be reliable Jurassic reference poles for cratonic North America. These poles form a consistent chronological progression defining two arcuate tracks of apparent polar wander (APW) from Sinemurian through Tithonian time (203–145 Ma). Combined with reliable Triassic and Cretaceous reference poles, the resulting path is well modeled by paleomagnetic Euler pole (PEP) analysis and is significantly different from previous APW compilations. These differences reflect differences in original data sets, modes of analysis, and geologic time scales and translate into substantial and important differences in paleolatitude estimates for cratonic North America. PEP analysis reveals two cusps, or changes in the direction of APW: one in the Late Triassic to Early Jurassic (Jl) and one in the Late Jurassic (J2). The Jl cusp represents the change in North American absolute plate motion associated with rifting of the central Atlantic and Gulf of Mexico, while the J2 cusp correlates temporally with the marine magnetic anomaly M21 plate reorganization and to various North American intraplate tectonomagmatic events (e.g., Nevadan Orogeny). Analysis of pole progression along the Jl to J2 and J2 to Cretaceous APW tracks indicates constant angular plate velocity of 0.6°–0.7°/m.y. from 203 to 150 Ma followed by significantly higher velocity from 150 to 130? Ma. Late Triassic‐Jurassic reference poles indicate more southerly paleolatitudes for cratonic North America than have previous compilations requiring modification of displacement scenarios for suspect terranes along the western Cordillera.