2008 Joint Annual Meeting (5-9 Oct. 2008): Magnetostratigraphic Correlation of the Triassic-Jurassic Moenave Formation, Southwest Utah and Northern Arizona, to Strata in the Newark and Hartford Basins

Correlation of lower Mesozoic strata between the American Southwest and eastern North America has been difficult largely because of differences in the character of sedimentary records and conflicting interpretations of the precision of the biostratigraphic data. Paleomagnetic data obtained from four previously unexamined localities in the Moenave Formation, Colorado Plateau (CP) and adjacent areas, are typically of high quality at the bed level, with magnetic directions carried by a high coercivity phase, probably hematite, that unblocks between 660^O and 680^O C. Site (bed) mean directions are north seeking and shallow, consistent with previous studies, and the timing of remanence acquisition is inferred to be close to the time of deposition. Magnetostratigraphic results indicate most of the Moenave Formation was deposited during a normal polarity geomagnetic field with the exception of four short and distinct intervals of reverse polarity. One is in the basal Dinosaur Canyon Member, and three are in the upper Whitmore Point Member. The reverse polarity magnetozome in Dinosaur Canyon strata most likely correlates to E24r from the Rhaetian Newark basin. The three reversals in the Whitmore Point most likely correlate with the reverse polarity magetozone from the Hettangian Hartford basin. If this correlation is valid, then the Triassic-Jurassic transition must lie between the middle to upper Dinosaur Canyon and lower to middle Whitmore Point strata. Our new magnetostratigraphic record obtained from the Moenave Formation thus allow a more precise correlation between strata in the CP area and those in the Newark and Hartford basins.