Reconnaissance paleomagnetic investigation of cretaceous limestones from southern México

Abstract

Paleomagnetic data from a total of 174 oriented samples collected from a400 m thick sequence of Cretaceous limestones from Oaxaca State, southern Mexico (-16.6°N, 97.0°W) were reported. The magnetic stability and vectorial composition were investigated by detailed alternating field and thermal demagnetization. A selection procedure based upon directional stability of demagnetized vectors and within-site dispersion restricts the data population to 115 samples. All stable samples are normally magnetized, which is consistent with the geologic age suggested for the sequence of Albian-Cenomanian, within the normal polarity interval. The direction and pole position obtained are 348.7°, 23.0° (k = 27, α95=6.6°) y 78.4°N, 149.8°E (k = 38, A95 = 5.5°). The pole position apparently diverges from the corresponding segment of the North American apparent polar wander path, which may suggest the occurrence of relative tectonic movement between that part of Mexico and North America. The angular divergence is small, and at present, this is just considered as one of the possible tectonic events within the suggested theories for the evolution of Middle America.