Untitled

Abstract

The fl uviodeltaic Colton Formation (Late Paleocene-Early Eocene) forms a lobate depositional system that prograded from the south into the Laramide Uinta Basin of northeastern Utah (United States) with a preserved sediment volume of ~3000 km 3 and a maximum thickness of ~1000 m. Joint consideration of detrital zircon ages, paleocurrent trends, and sandstone petrofacies permits an assessment of Colton provenance relations in the context of evolving Cretaceous-Paleogene sedimentation in the Utah foreland. Grains with U-Pb ages younger than 285 Ma derived from the Cordilleran magmatic arc form ~50% of the detrital zircons in arkosic Colton sand, and were transported ~750 km to the Uinta Basin from the Mojave segment of the arc by the California paleoriver. Colton sedimentation was the Paleogene culmination of a persistent pattern of Cretaceous sediment transport northward, subparallel to the Sevier thrust front, to supplement east-directed sediment delivery to the retroarc foreland from the Sevier thrust belt. The ratio of longitudinally to transversely derived sediment was enhanced in foreland strata after Laramide deformation produced intraforeland uplifts that screened the foreland belt from Sevier sources. The relative abundance of arc-derived detrital zircons that were contributed to strata of the Utah foreland increased in late Campanian time and remained high into Eocene time. Detrital zircon populations in Paleogene forearc strata of southern California are compatible with coeval derivation of arc-derived detritus in the forearc sands and the Colton backarc sand from a common paleodrainage divide crossing the Mojave region to connect hinterland Nevadaplano and Mexicoplano uplands to the north and south.

Detrital zircon U–Pb reconnaissance of the Franciscan subduction complex in northwestern California

“…The Franciscan Coastal Belt may have been translated north a moderate distance after accretion. Based mainly on Dickinson et al (1979Dickinson et al ( , 1988Dickinson et al ( , 2012, Heller et al (1985Heller et al ( , 1987, Underwood and Bachman (1986), Renne et al (1990), Wells et al (2000Wells et al ( , 2014, Wyld (2000), Stewart et al (2003), Reed (2004) Figure 6H shows the distinctive data pattern exhibited by mid-Maastrichtian to Palaeocene strata from one specific portion of the unnamed forearc basin of southernmost California (Jacobson et al 2011; see also Sharman et al 2014). Key populations are ca.…”

“…The relative amounts of Idaho and Sierra Nevada zircon reaching the Franciscan probably fluctuated over time, tracking fluctuations in erosion rates in the two source areas (cf. Dickinson et al 2012). In the Great Valley forearc basin, Markley Formation sandstones as young as 37 Ma contain significant detrital muscovite, suggesting that a continuous Princeton River-Princeton Canyon system persisted until about that time.…”

“…An aeolian sand sea covered much of the present-day Colorado Plateau during Jurassic time. Redeposition of these sands was a major source for Cretaceous and Palaeocene strata in the foreland basin of the Cordilleran orogen to the east of the Sierra Nevada arc and the Sevier foreland thrust belt Gehrels 2008, 2009a;Dickinson et al 2012). The erg sands were originally sourced mainly from the eastern USA via transcontinental rivers and contain prominent age peaks ( Figure 6I Nevada back arc region.…”

“…More details on these types are shown in Figure 6J-N. this basement in Arizona and southwestern California were exposed to erosion over the interval 95-14 Ma (e.g. Dickinson and Gehrels 2008;Jacobson et al 2011;Dickinson et al 2012;Sharman et al 2014). Some of our samples contain limited numbers of zircons with such ages.…”

Rejection of the lake spillover model for initial incision of the Grand Canyon, and discussion of alternatives

“…(4) The Wernicke (2011) model of a Cretaceous California paleoriver fl owing northeast through a paleo-Grand Canyon, supplanted by a Paleogene Arizona paleoriver fl owing to the southwest through the same canyon after drainage reversal, is diffi cult to reconcile with sedimentological and detrital zircon data for foreland stratigraphic units in Utah (Davis et al, 2010;Dickinson et al, , 2012. Detrital zircons from the Mesozoic Cordilleran magmatic arc in the Mojave region were transported in variable proportions longitudinally from southwest to northeast along the keel of the Sevier foredeep beginning with the onset of Cretaceous marine sedimentation near the Early-Late Cretaceous time boundary, and continuing into Paleoon April 3, 2013 geosphere.gsapubs.org Downloaded from Of uncertain signifi cance for the speculative development of a paleo-Grand Canyon is a gravel deposit associated with nonmarine limestone displaying columnar internal structure suggestive of lacustrine travertine or tufa exposed at an elevation of 1795 m near Cape Solitude (Scarborough, 2001, p. 209), the topographic point on the south rim of the Grand Canyon south of the junction of the Colorado and Little Colorado Rivers (Fig.…”