Detrital zircon U-Pb geochronology of Paleozoic strata in the Grand Canyon, Arizona

Abstract

We determined U-Pb ages for detrital zircons from 26 samples of Paleozoic sandstone from the Grand Canyon. Cambrian strata yield mainly ca. 1.44 and 1.7-1.8 Ga ages that indicate derivation from nearby basement rocks of the Yavapai Province. Devonian strata contain zircons of 1.6-1.8 Ga, 1.34-1.40 Ga, and ca. 520 Ma, suggesting derivation from the Mazatzal and Yavapai Provinces, midcontinent region, and the Amarillo-Wichita uplift, respectively. Mississippian strata record a major change in provenance, with predominantly 415-475 Ma and 1030-1190 Ma grains interpreted to have been shed from the central Appalachian orogen. Pennsylvanian strata contain subequal proportions of 1.4-1.8 Ga grains derived from basement rocks exposed in the Ancestral Rocky Mountains and 409-464 and ca. 1070 Ma grains derived from the Appalachians. Permian strata contain abundant Appalachian zircons, including 270-380 Ma grains, and a lesser proportion of grains derived from the Ancestral Rocky Mountains. Transcontinental transport during Mississippian through Permian time is interpreted to have occurred in large river systems, facilitated by northeasterly trade winds during low sea level and by coastal currents. A compilation of young ages from all Upper Paleozoic strata yields age peaks of Ma, an excellent match for Alleghanian, Acadian, Taconic, and Neoproterozoic (peri-Gondwanan) episodes of magmatism along the Appalachian margin. Lag times of the youngest grains in these Upper Paleozoic strata average ~25 m.y., suggesting relatively rapid exhumation and erosion of Appalachian source regions.

Generation and preservation of continental crust in the Grenville Orogeny

“…Rainbird et al (2012) showed that the Grenvillian zircon age peak is also present throughout the western margin of Laurentia from the Grand Canyon in the south to the Mackenzie Mountains in the north. These far-flung regions with a dominant Grenvillian age signature imply detritus initially shed from the Grenville orogenic belt was transported w4000 km across Laurentia (see also Rainbird et al, 1992;Rainbird et al, 1997;Dehler et al, 2010;Gehrels et al, 2011;Spencer et al, 2012). The key observation from the data summarized on Fig.…”

Variations in the Illite to Muscovite Transition Related to Metamorphic Conditions and Detrital Muscovite Content: Insight from the Paleozoic Passive Margin of the Southwestern United States

“…A recent detrital zircon U-Pb geochronology study of the Paleozoic stratigraphy of the Grand Canyon (Gehrels et al 2011) is useful for comparison with our IC results. Cambrian and Devonian strata of the Grand Canyon contain detrital zircon populations with age peaks at 1.4 and 1.7 Ga.…”

“…Starting at the Mississippian Surprise Canyon Formation (relatively thin, locally preserved paleochannels cut into the underlying Mississippian Redwall Limestone), there is a major shift in detrital zircon population that continues through the remainder of the Paleozoic section (see fig. 5 in Gehrels et al 2011). The primary difference is the appearance of detrital zircons with ages in the range of both ∼300-700 Ma and 1-1.2 Ga in Late Mississippian to Permian sediments, that is, considerably younger ages than in Cambrian and Devonian strata.…”

“…The change in detrital ages is interpreted as a change in provenance, from the derivation of zircons nearly exclusively from the crystalline basement of the southwestern United States during the Cambrian and Devonian, to significant derivation of zircons from the Appalachian orogen, beginning no later than the Late Mississippian. Basement uplifts of the Ancestral Rocky Mountains are also a significant source of zircons in Pennsylvanian and perhaps also Late Mississippian strata of the Grand Canyon (Gehrels et al 2011).…”

“…6) signals a large flux of clay-size detrital muscovite. Unfortunately, we have no data from the Surprise Canyon Formation to compare with detrital zircon data from Gehrels et al (2011). Since IC data have no age component, they cannot be used to distinguish between different possible sources (e.g., Appalachian or Ancestral Rocky mountains) on the basis of age differences.…”