Syncontractional deposition of the Cretaceous Newark Canyon Formation, Diamond Mountains, Nevada: Implications for strain partitioning within the U.S. Cordillera

Abstract

The timing of deformation and deposition within syntectonic basins provides critical information for understanding the evolution of strain in mountain belts. In the U.S. Cordillera, contractional deformation was partitioned between the Sevier thrust belt in Utah and several structural provinces in the hinterland in Nevada. One hinterland province, the Central Nevada thrust belt (CNTB), accommodated up to ∼15 km of shortening; however, in most places, this deformation can only be bracketed between Permian and Eocene. Cretaceous deposits of the Newark Canyon Formation (NCF), which are sparsely exposed along the length of the CNTB, offer the opportunity to constrain deformation timing. Here, we present mapping and U-Pb zircon geochronology from the NCF in the Diamond Mountains, which demonstrate deposition of the NCF during proximal CNTB deformation. Deposition of the basal NCF member was under way no earlier than ca. 114 Ma, a tuff in the middle part of the section was deposited at ca. 103 Ma, and the youngest member was deposited no earlier than ca. 99 Ma. Intraformational angular unconformities and abrupt along- and across-strike thickness changes indicate that NCF deposition was related to growth of an east-vergent fault-propagation fold. Clast compositions define unroofing of upper Paleozoic sedimentary rocks, which we interpret as the progressive erosion of an anticline ∼10 km to the west. CNTB deformation was contemporaneous with shortening in the Sevier thrust belt, which defines middle Cretaceous strain partitioning between frontal and interior components of the Cordillera. Strain partitioning may have been promoted by renewed underthrusting during a period of high-flux magmatism.

How Hot Is Too Hot? Disentangling Mid‐Cretaceous Hothouse Paleoclimate From Diagenesis

“…Di Fiori et al. (2020) divide the NCF type section exposure into five units (Knc1– Knc5). The NCF type section unconformably overlies either the Permian Carbon Ridge Formation, which is composed of marine shelf carbonates, siltstones, conglomerates, or the Mississippian shallow marine Ely Limestone (Druschke et al., 2011; Nolan & Hunt, 1962; Nolan et al., 1956; Strawson, 1981; Vandervoort, 1987).…”

Late Cretaceous upper-crustal thermal structure of the Sevier hinterland: Implications for the geodynamics of the Nevadaplano

“…Sedimentary rocks of interpreted Early Jurassic age are only preserved in one locality in northeastern Nevada, ~60 km north of our Egan and Cherry Creek Ranges cross section (Stewart and Carlson, 1978;Stewart, 1980). Early Cretaceous sedimentary rocks are only preserved at the longitude of the Diamond Mountains and Fish Creek Ranges and are interpreted to have been deposited proximal to active structures of the Central Nevada thrust belt (Long et al, 2014a(Long et al, , 2014bDi Fiori et al, 2020). Therefore, though it is possible that Jurassic and Cretaceous sedimentary rocks were locally deposited in areas of the Sevier hinterland, their lack of preservation, combined with our CAI compilation (Table 2) that shows that Mississippian-Pennsylvanian rocks that were buried as deep as ~3-4 km below the top of the Triassic section often yield CAI values of 1-1.5 (<50-90 °C), precludes deep burial under a thick, regionally continuous Jurassic-Cretaceous sedimentary section (e.g., Long, 2012).…”

“…To the west of the Sevier fold-thrust belt, a broad region of the Cordilleran retroarc in eastern Nevada and westernmost Utah is often referred to as the "Sevier hinterland" (e.g., Armstrong, 1972). Upper-crustal shortening, though likely of a low magnitude (a few tens of km), was diffusely distributed across the Sevier hinterland, and it was accommodated by east-vergent thrust systems in central Nevada and western Utah and a broad region of open folds in eastern Nevada (e.g., Gans and Miller, 1983;Taylor et al, 2000;Long, 2012Long, , 2015Greene, 2014;Long et al, 2014aLong et al, , 2014bDi Fiori et al, 2020) (Fig. 1).…”

“…The timing of construction of the culmination is constrained by syn-contractional deposition of the ca. 114-99 Ma Newark Canyon Formation on its eastern limb (Long et al, 2014a;Di Fiori et al, 2020). The Paleogene unconformity in the Diamond Mountains and Fish Creek Range is subhorizontal and overlies complexly deformed Cambrian to Permian rocks.…”

“…Because the Fish Creek Range experienced a history of Early Cretaceous (ca. 115-100 Ma) uplift and erosion during construction of the Eureka Culmination (Long et al, 2014a;Di Fiori et al, 2020), followed by normal fault-related exhumation between ca. 75-60 Ma , we did not use depth below the Paleogene unconformity to constrain the thermal gradient.…”