Understanding a critical basinal link in Cretaceous Cordilleran paleogeography: Detailed provenance of the Hornbrook Formation, Oregon and California

Abstract

ABSTRACT

Geochemistry of the Great Valley Group: an integrated provenance record

“…Furthermore, the shift in the Precambrian age signature from abundant Grenville-age zircon in Lower Cretaceous strata to a larger proportion of >1800 Ma zircon in Upper Cretaceous strata may reflect derivation of zircon from different meta-sedimentary terranes in the Sierran foothills (Figure 10), such as the Shoo Fly Complex (Harding et al 2000) and overlap sequence (Spurlin et al 2000), rather than from Klamath Mountains sources. This shift to Sierran sources for the Upper Cretaceous GVG is consistent with a change from southto west-directed palaeocurrent indicators and may be related to Late Cretaceous subsidence of the eastern Klamath Mountains and deposition of the middle to Upper Cretaceous Hornbrook Formation on eastern Klamath terranes (Haggart 1986;Nilsen 1993;Surpless and Beverly 2013 Eastern Hayfork Terrane; n = 162 Scherer et al (2010) G r e n v i l l e o r o g e n Y a v a p a i -M a t z a t z a l A n o r o g e n i c g r a n i t e s northwestern Laurentia…”

“…98 Ma) detrital zircon peak also characterizes much of the Albian(?) and younger strata in the Ochoco basin of central Oregon (Kochelek 2009), suggesting that N-directed axial drainage within the Sierran arc transported arc-derived sediment to regions north and northwest of the arc during much of the Late Cretaceous (Kochelek 2009;Surpless and Beverly 2013). Because these Ochoco basin strata are also rich in volcanic lithic grains, both the <100 Ma volcanic carapace and its plutonic roots probably shed abundant zircon during the entire Late Cretaceous, but this central and eastern arc detritus was partitioned from the Sacramento basin to the west until eastward migration of westward-flowing drainage systems reached the arc axis during the latest Cretaceous.…”

East-derived strata in the Methow basin record rapid mid-Cretaceous uplift of the southern Coast Mountains batholith

“…The complete lack of the 120-105 Ma zircon grains in the mid-Cretaceous Hornbrook Formation that are so prominent in the Methow basin, and similarly, the lack of 140-120 Ma grains in the Methow basin that are so common in the Hornbrook basin suggests that these were separate systems during the mid-Cretaceous. These two basins also experienced very different tectonic histories, as the mid-Cretaceous history of the Hornbrook basin is one of subsidence rather than compression or transpression, as sedimentation in the Hornbrook basin shifted from alluvial systems in Albian time to shelf and deep basin deposition during Cenomanian through Maastrichtian time (Nilsen 1993;Surpless and Beverly 2013).…”

“…However, it seems unlikely that there would be no record of mixing of sediment within the larger basin system, particularly in the deeper marine turbidite systems that characterized the mid-Cretaceous Methow, Hornbrook, and Ochoco basins. Mid-Cretaceous strata of the Hornbrook Formation have Early Jurassic and Late Jurassic through Early Cretaceous detrital zircon age peaks, with abundant grains between 150 and 125 Ma and only a handful of grains younger than 130 Ma (Surpless and Beverly 2013). The complete lack of the 120-105 Ma zircon grains in the mid-Cretaceous Hornbrook Formation that are so prominent in the Methow basin, and similarly, the lack of 140-120 Ma grains in the Methow basin that are so common in the Hornbrook basin suggests that these were separate systems during the mid-Cretaceous.…”

Evolution of the Jura-Cretaceous North American Cordilleran margin: Insights from detrital-zircon U-Pb and Hf isotopes of sedimentary units of the North Cascades Range, Washington

“…9 and 11). The bimodal signature is present in coeval strata in the Great Valley sequence of central California (DeGraaff-Surpless et al, 2002;Sharman et al, 2014), the Hornbrook Basin of northern California and southern Oregon (Surpless and Beverly, 2013;Surpless, 2015), and the Mitchell Inlier of the Blue Mountains in central-eastern Oregon (B. Housen in LaMaskin, 2012). Methow strata in Washington are more similar to rocks currently in Oregon and northern California than Methow units in southern British Columbia, which have a larger proportion of ca.…”