Basin formation near the end of the 1.60–1.45 Ga tectonic gap in southern Laurentia: Mesoproterozoic Hess Canyon Group of Arizona and implications for ca. 1.5 Ga supercontinent configurations

Abstract

Detrital zircon data from the upper parts of the Proterozoic Hess Canyon Group of southern Arizona reveal abundant 1600-1488 Ma detrital zircons, which represent ages essentially unknown from southern Laurentia. This basinal succession concordantly overlies a >2-km-thicksection of 1657 ± 3 Ma rhyolite of the Redmond Formation. The rhyolite is intercalated with and hence contemporaneous with the lower parts of the overlying White Ledges Formation, a 300-m-thick orthoquartzite unit at the base of the Hess Canyon Group. These quartzites contain a unimodal detrital zircon age probability distribution with peak ages of 1778, 1767, and 1726 Ma, supporting regional correlation with other ca. 1.65 Ga quartzite exposures in southwestern Laurentia. However, the ~900-m-thick argillaceous Yankee Joe and minimum 600-m-thick quartzite-rich Blackjack Formations contain younger detrital zircons, with peak ages ranging from 1666 to 1494 Ma and a maximum depositional age of 1488 ± 9 Ma. Prominent age peaks at 1582-1515 Ma and 1499-1488 Ma represent detritus that is exotic and not derived from known southern Laurentian sources. The Blackjack Formation is cut by the 1436 ± 2 Ma Ruin Granite, indicating that deposition, deformation, and intrusion occurred between 1488 and 1436 Ma. This basin likely developed before or in the early stages of the 1.45-1.35 Ga intracontinental tectonism in southwestern Laurentia. Our fi ndings necessitate the presence of an ~170 m.y. disconformity within the Hess Canyon Group and document a previously unrecognized episode of Mesoproterozoic basin sedimentation (>1.5 km of section) between 1488 and 1436 Ma in southern Laurentia. This new record helps to fi ll the 1.60-1.45 Ga magmatic gap in southern Laurentia and supports hypotheses for a long-lived Proterozoic tectonic margin along southern Laurentia from 1.8 to 1.0 Ga. The 1.6-1.5 Ga detrital zircon ages offer important new constraints for ca. 1.5 Ga Nuna reconstructions and for the paleogeography of contemporaneous basins such as the Belt Basin in western Laurentia.

A Case for Revising the Timing, Regional Extent, and Significance of the Mazatzal Orogeny in Its Type Area

“…The west central part of Tonto basin features Roosevelt Lake which receives water from Tonto Creek on the north and the upper Salt River on the south. The upper Salt River Canyon contains, in part, the former Hess Canyon Group (Trevena, 1979) now subdivided into the Paleoproterozoic White Ledges Formation and the overlying Yankee Joe Group (Doe et al, 2012). This area holds critical new data supporting revision of the timing of the Mazatzal Mountains (Doe, 2014).…”

“…The Mazatzal Group rests on 1700-1730 Ma age units (Doe, 2014;Cox et al, 2002;Dann, 1997;Doe and Karlstrom, 1991) while both sections at Four Peaks (Mako et al, 2015) and the upper Salt River Canyon rest on 1657 Ma ash flow tuffs (Doe, 2014;Doe et al, 2012;Karlstrom et al, 1990). All of the Mazatzal Group and equivalents are characterized by increasingly mineralogic maturity upsection.…”

“…The White Ledge Formation is disconformably overlain by the Yankee Joe and Blackjack Formations, formerly comprising the Hess Canyon Group (Doe et al, 2012;Trevena, 1979;Cuffney, 1977). The Yankee Joe and Blackjack Formations yield abundant "magmatic-gap" age zircons ranging from around 1600-1470 (Doe et al, 2012;Doe et al, 2014;Doe, 2014).…”

“…The Yankee Joe and Blackjack Formations yield abundant "magmatic-gap" age zircons ranging from around 1600-1470 (Doe et al, 2012;Doe et al, 2014;Doe, 2014). The former Hess Canyon Group is now the Paleoproterozoic White Ledges Formation and the Yankee Joe Group (Doe et al, 2012).…”

“…On the lower right are stratigraphic sections from the northern Mazatzal Mountains (Doe, 1991), Four Peaks (Powicki, 1996), and the upper Salt River Canyon (Doe, 2014;Doe et al, 2012), roughly a straight line distance of 90 km. The photo on the left shows folded sediments of the Hopi Springs Shale exposed beneath the Barnhardt thrust in the northern Mazatzal Mountains.…”