Detrital zircon evidence for derivation of arkosic sand in the eolilan Narbona Pass Member of the Eocene-Oligocene Chuska Sandstone from Precambrian basement rocks in central Arizona

Abstract

The Narbona Pass Member of the Chuska Sandstone, exposed only along the crest of the Chuska Mountains (Arizona–New Mexico), is the central remnant of the Oligocene Chuska erg, which is inferred to have occupied ~125,000 km2 of the southeastern Colorado Plateau within a subcircular area surrounded by Oligocene volcanic fields. The high paleotopography of active volcanic edifices delimited the lateral extent of erg deposition except to the west, which was upwind for eolian sand transport. The dominant arkosic petrofacies of the Narbona Pass Member, as exposed at Narbona Pass near Crystal (NM) and at Buffalo Pass near Lukachukai (AZ), was derived mainly from Precambrian basement in central Arizona. The principal subpopulations of detrital zircons (n=100 grains) by U-Pb age are 1770-1640 Ma (~70% with age peak at 1700 Ma), reflecting derivation from the Yavapai-Mazatzal belt of southwest Laurentia, and 1460-1400 Ma (~15% with age peak at 1425 Ma) derived from anorogenic granite bodies intrusive into Yavapai-Mazatzal basement. Precambrian detritus was apparently carried northward to alluvial plains deposited west of the Chuska erg and deflated to feed sand into the erg interior. Other remnants of the Chuska erg along the northern flank of the Mogollon-Datil volcanic field, in the subsurface of the Albuquerque basin of the Rio Grande rift, and near Whiskey Lake in the southernmost Chuska Mountains are petrographically distinct from the arkosic petrofacies of the erg interior, and were evidently derived from other sources as yet untested by detrital zircons. The areal variability of erg sand implies either different pathways for sand transport across the expanse of an integrated Chuska erg or segmentation of the Chuska erg into multiple subdivisions that were partly separated by inselbergs of the pre-Oligocene erg substratum.