Late Cretaceous time-transgressive onset of Laramide arch exhumation and basin subsidence across northern Arizona–New Mexico, USA, and the role of a dehydrating Farallon flat slab

Abstract

Spatiotemporal constraints for Late Cretaceous tectonism across the Colorado Plateau and southern Rocky Mountains (northern Arizona−New Mexico, USA) are interpreted in regards to Laramide orogenic mechanisms. Onset of Laramide arch development is estimated from cooling recorded in representative thermochronologic samples in a three-step process of initial forward models, secondary HeFTy inverse models with informed constraint boxes, and a custom script to statistically estimate timing of rapid cooling from inverse model results. Onset of Laramide basin development is interpreted from increased rates of tectonic subsidence. Onset estimates are compared to published estimates for Laramide timing, and together suggest tectonism commenced ca. 90 Ma in northwestern Arizona and progressed eastward with later onset in north-central New Mexico by ca. 75−70 Ma. The interpreted sweep of onset progressed at a rate of ∼50 km/m.y. and was approximately half the 100−150 km/m.y. rate estimated for Late Cretaceous Farallon-North America convergence during the same timeframe. Previous suggestions that the Laramide tectonic front progressed at a rate similar to convergence via basal traction are not supported by our results. We thereby suggest that (1) a plate margin end load established far field compression and that (2) sequential Laramide-style strain was facilitated by progressive weakening of North American lithosphere from the dehydrating Farallon flat slab. Results are compared to models of sweeping tectonism and magmatism in other parts of the Laramide foreland. Discussions of the utility of the custom script and the potential for stratigraphic constraints to represent only minimum onset estimates are also presented.

Orogens of Big Sky Country: Reconstructing the Deep‐Time Tectonothermal History of the Beartooth Mountains, Montana and Wyoming, USA

“…Other models more consistent with ≥90 Ma basement uplift include the propagation of basement deformation ahead of the developing flat slab (e.g., Kulik & Schmidt, 1988), potentially as a result of plate margin end loading driving far‐field compression (e.g., Axen et al., 2018; Behr & Smith, 2016; Erslev et al., 2022; Jackson et al., 2019; Livaccari & Perry, 1993; Thacker et al., 2022). Alternatively, early basement deformation in southwest Montana may be largely unrelated to flat‐slab subduction.…”

Spatiotemporally heterogeneous deformation, indirect tectonomagmatic links, and lithospheric evolution during orogenic activity coeval with an arc flare-up

“…2,10). Meanwhile, shortening continued in other across-strike segments of the southwestern U.S. Cordilleran orogen throughout the Late Cretaceous (e.g., Yonkee and Weil, 2015;Thacker et al, 2022). Counterintuitively, the whole orogen-scale partitioning of shortening out of the arc and into across-strike domains (Fig.…”