Detrital zircon ages from quartzite and metaconglomerate in the Tusas and Picuris Mountains in northern New Mexico reveal new information about age and provenance trends within a >1000 km² Proterozoic sedimentary basin and provide a critical test of regional correlations. Samples from the Paleoproterozoic Vadito and Hondo groups are dominated by a single detrital zircon population with age probability peaks that range from 1765 to 1704 Ma. Minor Archean and ca. 1850 Ma age probability peaks were also recognized in some samples. Close correspondence between detrital zircon ages and the age of surrounding basement rocks indicates predominately local sources, and we interpret systematic shifts in peak ages with stratigraphic position to represent changes in local sources through time. Similarities of age spectra support previous correlation of stratigraphic units between discontinuous exposures of the Hondo Group. We interpret that these supracrustal rocks were deposited in a single basin that we refer to as the Pilar basin.
Two samples of the Marqueñas Formation, a pebble to boulder conglomerate previously correlated with the ca. 1700 Ma Vadito Group, are dominated by Paleoproterozoic detrital zircon with age probability peaks at 1707 and 1715 Ma in the middle and upper units, respectively. Unlike the Vadito and Hondo group samples, the Marqueñas Formation also contains abundant ca. 1700–1600 Ma zircon derived from Mazatzal-aged sources to the south and Mesoproterozoic zircon with age probability peaks at 1479 and 1457 Ma. Weighted averages of 1477 ± 13 Ma and 1453 ± 10 Ma for the youngest detrital zircon in the middle and upper Marqueñas Formation provide new maximum depositional age constraints, indicating that it is not part of the Vadito Group. The minimum age is not well constrained but is interpreted to be ca. 1435 Ma on the basis of the timing of regional metamorphism and deformation previously documented in the Picuris Mountains. These data represent the first evidence of sedimentation directly associated with ca. 1.4 Ga regional metamorphism, plutonism, and deformation in the southwestern United States and provide an important new constraint on the tectonic evolution of southern Laurentia during this time.
- Received 16 May 2010.
- Revision received 23 February 2011.
- Accepted 16 March 2011.
- © Geological Society of America