PALEOMAGNETISM AND MAGNETIC FABRICS OF THE GLEN MOUNTAINS LAYERED COMPLEX, WICHITA MOUNTAINS, OKLAHOMA

This work presents new paleomagnetic, rock magnetic and magnetic fabric data from the western portions of the 532.49 Ma Glen Mountains Layered Complex (GMLC) and associated mafic-intermediate rocks in southwestern Oklahoma. Results from most sites suggest the presence of a primary, early Cambrian magnetization which is similar to earlier paleomagnetic studies of the GMLC as well as results from contemporaneous rocks in Quebec. Several other site results show substantial divergence (up to 90°) from this apparent pole position, inconsistent with the apparent polar wander path but similar to previous results from other Cambrian igneous rocks in Southern Oklahoma. Two sites in the Roosevelt Gabbros yield apparent pole positions congruent with the late Pennsylvanian to early Permian part of the apparent polar wander path, indicating a late Paleozoic remagnetization, and two sites in anorthosite show evidence of partial overprints at this time as well. Rock magnetic data suggests all magnetizations are carried in magnetite. Anisotropy of magnetic susceptibility (AMS) data show well-developed fabrics in the GMLC which are typically oblate with near-horizontal planes of magnetic foliation. As magnetic foliation planes in layered mafic intrusions usually correspond to the orientation of layering, these data are inconsistent with previous reports of 10-20° northerly or northeasterly regional dip. The average pole to magnetic foliation instead indicates a gentler northeasterly to easterly dip, with a confidence interval that includes no dip at all. Using published estimates of GMLC dip or AMS as a proxy for tilt corrections does not significantly change the location of the apparent primary VGP (21.4 °S, 205.4 °E, α95 = 13°). The GMLC results indicate general preservation of a primary Cambrian magnetization and a lack of significant tilting. The divergent results may be due to previously unrecognized remagnetization event, or possibly Cambrian geomagnetic instability.