Anomalous clastic wedge development during the Sevier-Laramide transition, North American Cordilleran foreland basin, USA

Abstract

New, high-resolution, regional correlation and isopach maps provide evidence that (1) Laramide-style deformation began as early as ca. 77 Ma in central Utah, and (2) rapid (208 km m.y. -1 ) and extensive (400 km) progradation of a clastic wedge was facilitated by reduced subsidence during the transition from Sevier-to Laramide-style deformation. This study defines three Campanian, alluvialto-marine clastic wedges that traversed 200-400 km eastward across the Utah-Colorado segment of the Cordilleran foreland basin. Wedges A and C are thicker successions with rising-trajectory shoreline stacking patterns (Blackhawk Formation and Lower Castlegate Sandstone, Bluecastle Tongue and Rollins Sandstone) that reflect relatively slow overall progradation (50-81 km m.y. -1 ) of narrow (10-20 km wide), wave-dominated shorelines. In contrast, wedge B consists of lower-volume successions with a flat to falling shoreline stacking pattern (Middle Castlegate Sandstone, Sego Sandstone, Neslen Formation, Corcoran and Cozzette Members of the Iles Formation) that suggests rapid progradation (~208 km m.y. -1 ) of embayed (60-80 km wide), mixed-energy (wave-and tide-influenced ) shore lines. Wedges A and C prograded 200-250 km in more than ~3 m.y., whereas wedge B prograded 340-400 km in ~2 m.y. (~170 km m.y. -1 ). The anomalously extensive wedge B is unique in the Utah-Colorado segment because of its long extent, rapid progradation rate, dominance of tidally influenced facies, long-transit transgressions/regressions, and low-accommodation, nested sequence architecture. Stratigraphic relationships indicate development of wedge B coeval with both Sevier-and Laramide-style deformation in Utah. Assuming a constant sediment supply, the extensive (>300-400 km) "sheet-like" amalgamated wedge (wedge B) may have been caused by (1) reduced subsidence driven by a flexural interference pattern, whereby two short-wavelength (±200 km) flexural profiles are superimposed during the uplift of both basement-cored and thin-skinned thrust belt, (2) an increase in, or eastward migration of, dynamic subsidence during tectonic transitions associated with slab flattening or rollback (i.e., long-wavelength flexure), or (3) reduced subsidence due to short-wavelength flexural interference augmented by the reduction, or migration, of long-wavelength flexure.

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“…Growth faults along the East Kaibab monocline fl anking the Kaibab uplift bracket the onset of Laramide deformation at 80-76 Ma (Tindall et al, 2010) in middle Campanian time and thinning of Cretaceous strata across the San Rafael Swell farther north document initiation of that uplift as a subsurface growth fold as early as 77 Ma (Aschoff and Steel, 2011) within the same time frame. Initiation of the uplifts as buried subsurface structures did not initially preclude transport of sediment across their evolving crests, but the unconformity between the Kaiparowits Formation and the Canaan Peak Formation in the Table Cliff syncline implies that the Kaibab uplift had attained surfi cial relief by Maastrichtian time.…”

Exhumation of the North American Cordillera revealed by multi-dating of Upper Jurassic–Upper Cretaceous foreland basin deposits

“…However, the North America Cor di lleran foreland was partitioned by Laramide-style basement-cored uplifts by Maastrichtian time (ca. 71 Ma) (Dickinson et al, 1988;DeCelles, 2004), and Aschoff and Steel (2011) proposed that Laramide deformation initiated during the Campanian, as early as ca. 77 Ma.…”

Mass-Balance Constraints On Stratigraphic Interpretation of Linked Alluvial-Coastal-Shelfal Deposits From Source To Sink: Example From Cretaceous Western Interior Basin, Utah and Colorado, U.S.A

“…2A) is either correlated to the top of the lower part of the Castlegate Sandstone at the Castle Gate locality (section numbered 7 in Fig. 2A) (McLaurin and Steel 2000;Aschoff and Steel 2011), or is truncated by a westward-dipping unconformity that is older than the top of the lower part of the Castlegate Sandstone at the Castle Gate locality (Yoshida et al 1996;Willis 2000;Miall and Arush 2001). This latter correlation implies that the lower part of the Castlegate Sandstone to the west of the Castle Gate locality (section numbered 7 in Fig.…”