Abstract

We have analyzed 180 oriented samples of the batholithic complex and overlying red beds of the Chiapas Massif in southern Mexico for a paleomagnetic study. Both stepwise alternating-field and thermal demagnetization procedures revealed dual-polarity characteristic magnetizations above 10-30 mT or 200-400 °C in about 60% of the samples demagnetized. Three distinct and ancient paleomagnetic directions have been identified. Late Permian intrusions (256 ± 10 Ma) yield nearly equatorial southern hemisphere paleolatitudes and a paleopole (13.4°S,176.1°E; 12 sites, K = 15.4, A95 = 11.4°) rotated ∼75°, counterclockwise, with respect to the North American reference pole. A selected set of Late Triassic(?)-Jurassic red beds of the Todos Santos Formation yields a paleopole at 22.6°N, 170.6°E (4 sites, K = 56.8, A95 = 12.3°), which implies ∼60° counterclockwise rotation, and a near equatorial northern hemisphere paleolatitude. Middle-Late Jurassic dikes and granites yield a paleopole at 77.4°N, 97.4°E (6 sites, K = 269.2, A95 = 4.1°) near the Mid-Jurassic segment of the North American apparent polar wander path. These data are consistent with a pre-rift configuration in which the Maya Block is rotated to a position off the coast of Texas and Louisiana in the present-day area of the Gulf of Mexico. A further implication is that by Oxfordian times, Chiapas (and by inference the Maya Block) was essentially in its current position with respect to cratonic North America.

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