SEISMIC IMAGING OF THE YAVAPAI-MAZATZAL PROVINCE BOUNDARY IN NORTHEASTERN NEW MEXICO: RESULTS FROM CD-ROM AND INDUSTRY PROFILES

The CD-ROM project is an integrated effort to study the evolution of the lithosphere of the Rocky Mountains. Here we present results from seismic reflection studies in the Yavapai-Mazatzal province boundary zone of northern New Mexico for which the goals are to understand the nature of Precambrian boundary at depth, and to extend our understanding of the exposed boundary eastward beneath the Phanerozoic cover in the Great Plains. The data include two re-correlated industry profiles and data collected during the 1999 Continental Dynamics-Rocky Mountain project (NM line 1). All show reflectors at a variety of crustal levels. Our industry data come from the Tucumcari basin and include a north-south profile that is ~77 km long and ties an E-W profile that is ~110 km length. CD-ROM NM line 1 images strong reflections from 5 to 15 s over a horizontal distance ~52 km. This domal structure may be related to a north-dipping ductile shear zone with north-side-down (normal) displacement that meay be associated with 1.4 Ga extension. The Moho, which is manifested as a disappearance in reflectivity, is at a depth of ~45 km. Correlation with well data suggests that reflectivity just below ~ 1 s on the industry profiles represent intercalated metavolcanic and metasedimentary rocks and mafic intrusions related to Proterozoic extension at either ~1.3 Ga or 1.1 Ga. These data also exhibit strong reflectivity between 5 and 8 s. Gravity models are currently being constructed, using the interpreted seismic profiles as constraints.