Structure of northeastern New Mexico from deep seismic reflection profiles: Implications for the Proterozoic tectonic evolution of southwestern North America.

摘要

Previous geologic, geochronologic, structural, isotope, and xenolith studies have shown that the Precambrian rocks of northern New Mexico belong to the Yavapai and Mazatzal provinces. The boundary between the provinces is a wide zone defined on its northern edge by the northern extent of 1.65 Ga deformation and southern edge by the southern most extent of Yavapai crust (pre-1.7 Ga). However, the nature of the Precambrian province boundary at depth, its evolution through time, and the tectonic processes that affected the interior of these provinces, are not well understood. In order to obtain new information concerning these problems, processing and interpretation of reflection seismic data was conducted on data collected during the 1999 Continental Dynamics-Rocky Mountain (CD-ROM) project and data obtained from industry.; In this study I present new information on the crustal structure of northern New Mexico provided by processing and interpretation of three seismic reflection profiles (NM-1, TB-1 and TB-2).The seismic data present evidence for Precambrian crustal growth and amalgamation, followed by subsequent reactivation of Precambrian structures.; A seismic profile and gravity modeling across the NM-1 show a strongly reflective high-density (2850 kg-m−3) dome-shaped body in the middle to lower crust. On the basis of the absence of a hanging-wall antiform, the occurrence of normal sense of deflection of reflectors in the footwall, possibly Moho pullup, and geological information such as an exposed Proterozoic extensional shear zone in the Sandia Mountains, this feature is interpreted to represent a 1.4 Ga? extensional shear zone which resulted in rotation of ∼1.65 Ga imbricate thrust zones.; Layered reflectivity directly below the top of Precambrian basement on profiles TB-1 and the eastern part of TB-2, based on geophysical and geological information from nearby areas is interpreted as a sequence of ∼1.4 Ga volcanic and sedimentary rocks within the Proterozoic Granite Rhyolite terrane.; Most of the interpreted structures and lithologies on profile NM-1 are related to ∼1.65 Ga and ∼1.4 Ga tectonic events, whereas the geologic features on TB-1 and TB-2 are interpreted to be mainly related to ∼1.1, 1.26, and 1.3 Ga extensional event. (Abstract shortened by UMI.)