Proterozoic banded metasiltstones in the Manzano Mountains of central New Mexico are a distinctive structural marker in the Capilla Peak Quadrangle. These rocks are important because they preserve a record of early history of the Manzano thrust belt. The rocks are newly interpreted as mylonitized metasiltstones with a volcanic source based on bulk composition (~70% SiO2, ~15% Al2O3). The orientation of the rocks and the map pattern suggest refolded folds that produced "mushroom-style" interference patterms (van der Pluijm and Marshak, 1997). Mylonitic stretching lineations (L1) from an earlier deformation were later folded by F2. The shear sense during S1 mylonitization of metasiltstones was top to the west-northwest. Petrologic analysis shows grain size reduction via crystal plastic deformation (mylonitization). This rock is interpreted to be part of a wide zone of shearing related to the Monte Largo thrust zone, where amphibolite-grade rocks to the southeast were thrust west and north on top of greenschist-grade rocks to the north (top to the northwest). Thrusting probably took place between 1.656 billion years and 1.427 billion years ago, as shown by available geochronology in the Monte Largo thrust zone. This thesis involves field and analytical work.
Earth and Planetary Sciences
Level of Degree
Department of Earth and Planetary Sciences
First Committee Member (Chair)
Proterozoic Deformational History, Proterozoic, Manzano Mountains, Banded Metasiltstones, Trigo Canyon
Doran, Linda. "Banded metasiltstones in Trigo Canyon : the story they tell about the Proterozoic deformational history of the Manzano Mountains." (2002). http://digitalrepository.unm.edu/eps_etds/19