The most recent models for the Mesoproterozoic (ca. 1.5−1.35 Ga) Picuris-Baraboo-Pinware orogeny call on transpression resulting from oblique, diachronous convergence at the southern margin of Laurentia to explain the patterns of deformation and magmatism along this transcontinental belt. The Marqueñas Formation metaconglomerate provides a rare opportunity to directly study the strain and kinematics of deformation within the intraplate Picuris segment of the orogen. Statistical analysis of deformed quartzite pebble and boulder dimensions shows flattening strain at the outcrop to map scale (kilometers to meters). Quartz crystallographic preferred orientation (CPO) records a combination of flattening and non-coaxial shear at the intraclast scale (millimeters to micrometers). Kinematic vorticity axes, determined by crystallographic vorticity analysis on quartzite clasts, are well preserved despite widespread static recrystallization and align with principal strain axes determined from quartz CPO. The compatibility of strain and kinematic vorticity data indicates that flattening was produced in progressive, 3-D general shear. Outcrop-scale and map-scale structural relations link Marqueñas Formation flattening strain to oblique slip, with components of north-directed thrusting and dextral shear, on the Plomo-Pecos shear zone. Quartz flattening CPO yields predominantly crossed-girdle c-axis figures with opening angles of 69°−92° and a mean of 80°. Quartz c-axis opening angle thermometry yields deformation temperatures of 601 ± 50 °C, suggesting that flattening was synchronous with prograde to peak metamorphism during the second phase of deformation (D2) in the Picuris Mountains. We conclude that flattening of the Marqueñas Formation records inclined transpression within the Picuris orogen, consistent with oblique convergence along the Mesoproterozoic Laurentian plate margin.

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