Wednesday, 8 October 2008
George R. Brown Convention Center, Exhibit Hall E
Jurassic boundary lies within conformable, non-marine strata of the Dinosaur Canyon tectonosequence (DCt) of the southern Colorado Plateau. The DCt is bounded below by an unconformity, U-Crp, at the base of the Dinosaur Canyon Member of the Moenave Formation or the base of the Rock Point Member of the Chinle Formation. The upper sequence boundary, U-Mwp, lies within the upper Whitmore Point Member or the basal Springdale Sandstone Member of the Moenave Formation. The late Triassic to Early Jurassic westward excursion of North America interpreted from the low-latitude North American apparent polar wander, NA APW, path is interpreted from pole positions obtained from the DCt. New magnetostratigraphic data indicate that the J-1 cusp of the low-latitude NA APW path lies within the U-Mwp hiatus. Based on revised interpretations of pollen ages in the Whitmore Point Member of the Moenave Formation, the J-1 cusp is no older than late Hettangian.
Identification of the Triassic – Jurassic boundary near the base of the DCt: (1) invalidates J-0 of previous workers as the base of the Jurassic System; (2) establishes correlation of the DCt with the unconformity-bounded marine sequence at New York Canyon, Nevada, the proposed basal Jurassic GSSP; and (3) establishes correlation of the DCt with strata of the New Haven and Passaic formations of the Newark Supergroup and emplacement of the Central Atlantic Magmatic Province, CAMP. Correlation of the DCt with CAMP emplacement poses the possibility of a cause and effect relation between CAMP emplacement and coeval westward excursion of North America.