Structural data from the Joyita uplift: Implications for Ancestral Rocky Mountain deformation within central and southern New Mexico
William C. Beck and Charles E. Chapin
Structural analysis of the modern-day Joyita Hills defines two brittle-fault trends that were active during ancestral Rocky Mountain (late Paleozoic) deformation. North-striking, west-dipping normal faults and northwest-striking, southwest-dipping normal faults bound the late Paleozoic Joyita uplift to the west and south, respectively, and define the uplift as a north-trending structural high. Kinematic indicators define brittle-fault displacement as dominantly dip slip, with north-striking normal faults showing a significant component of left slip. The Proterozoic core of the Joyita Hills contains three preferred orientations of gneissic to mylonitic foliations, two of which are comparably oriented to the late Paleozoic brittle faults. Direct field observation shows that north-striking mylonites and foliations have been reactivated by the younger, north-striking brittle faults. Northwest-striking brittle faults are also thought to represent reactivation of northwest-striking foliations, although this correlation has not yet been verified. Drill-core data indicate that the San Mateo and Lucero basins were one continuous, north-trending basin. The modified basin connects with the Orogrande basin via a southeasttrending channel. Geometrical and kinematic analyses, when combined with basin trends and available paleocurrent data, suggest that a north-trending, divergent, left-lateral wrench zone was active within central and southern New Mexico during the late Paleozoic.
- Beck, William C.; Chapin, Charles E., 1991, Structural data from the Joyita uplift: Implications for Ancestral Rocky Mountain deformation within central and southern New Mexico, in: Geology of the Sierra Blanca, Sacramento and Capitan Ranges, New Mexico, Barker, James M.; Kues, Barry S.; Austin, George S.; Lucas, Spencer, G., New Mexico Geological Society, Guidebook, 42nd Field Conference, pp. 183-190.