A source‐to‐sink analysis incorporating geochronometric and thermochronometric data from the Sevier fold‐thrust belt (SFTB) and proximal synorogenic strata of the Canyon Range Conglomerate (CRC) and Indianola Group (IG) provides new insights into orogenic exhumation, erosional unroofing, and the interplay between thrusting and coarse clastic deposition in the Cretaceous Cordilleran foreland basin of western North America. Zircon (U‐Th)/He ages from the Pavant and Nebo thrust sheets record significant Cenomanian cooling indicative of synchronous exhumation and thrusting along a large segment of the SFTB in central and northern Utah. Detrital zircon (U‐Th)/He (DZHe) ages indistinguishable from depositional ages from the Cenomanian Dakota Formation and lower CRC also record rapid unroofing of the SFTB and synchronous deposition. DZHe data from wedge‐top deposits of the CRC record two significant unroofing episodes: Albo‐Cenomanian exhumation of the Pavant thrust and progressive unroofing of the Canyon Range culmination. For the IG, the presence of Paleozoic DZHe ages along with Paleozoic‐Mesozoic DZ U‐Pb ages in the Cenomanian Sanpete Formation suggests derivation from Paleozoic to Jurassic strata exhumed in the frontal Pavant and Nebo thrust sheets. After the Cenomanian episode of rapid exhumation, proximal foredeep strata recorded a widespread DZ provenance shift in the Turonian. Short DZHe lag time values from Campanian CRC and IG deposits reveal rapid exhumation of the SFTB during the Campanian. The synchroneity of major shortening and Campanian and Cenomanian changes in foreland basin architecture and provenance supports models proposing that active shortening in the fold‐thrust belt coincides with coarse clastic influx in foreland basins.
Puerto Rico and the northern Virgin Islands together preserve a unique archive of island arc construction and plate margin deformation along the northeastern edge of the Caribbean plate. In Eocene times, arc-continent collision of the Caribbean plate and the North American plate led to transpressional deformation along two major fault systems in Puerto Rico, resulting in an island-wide depositional hiatus. Although styles and kinematics of this deformational event are seemingly well understood, the lack of chronologic constraints have left uncertainties related to the timing of inception and activity, the magnitude of crustal exhumation, and the character of deformation (i.e., progressive or polyphase). New zircon and apatite (U-Th)/He ages reveal that deformation associated with arc-continent collision started in the early Eocene (ca. 52 Ma) and ended in the early Oligocene (ca. 29 Ma). Over this 23 m.y. time frame, deformation was not restricted to major faults, instead it propagated gradually eastward, with punctuated episodes of vertical exhumation in the early Eocene (ca. 52−34 Ma) and late Eocene (ca. 36−29 Ma). In contrast, the northern Virgin Islands experienced rapid cooling and exhumation in the early Miocene (ca. 24−21 Ma) associated with the extensional opening of the Anegada Passage. The modeled thermal histories for the central and northeastern part of Puerto Rico indicate collision-related peak transpressional deformation between 36 and 29 Ma and an average exhumation rate 0.9 ± 0.6 km/m.y. These results represent the first direct constraints on the timing and magnitude of collisional exhumation and offer insights into the deformational evolution of the northeastern edge of the Caribbean plate.
Previous studies on the Lower‐Middle Jurassic Cuyo Group in the southern Neuquén Basin, Argentina, have discussed evidence for pre‐ and syn‐depositional structural inversion during pre‐Andean shortening. While the Cuyo Group sequence stratigraphic and facies framework are well understood, the effects of structural inversion and progressive postrift thermal subsidence on sediment provenance and dispersal, as well as the timing and magnitude of deformation during and after Cuyo Group deposition, remain poorly constrained. The Cuyo Group comprises both reservoir‐quality fluvial to deep‐marine siliciclastic deposits and a petroleum source‐rock. Thus, the temporal relationship between the onset of deformation and sediment dispersal are crucial aspects for an improved understanding of both the basin evolution and petroleum system. This study presents new detrital zircon (U‐Th)/(He‐Pb) double dating from the Los Molles and Lajas Formations of the Cuyo Group in the southern area of SW Zapala to evaluate the influence of early rift inversion on sediment routing, provenance, and palaeogeography, and to provide crucial chronostratigraphic constraints. The youngest concordant Jurassic detrital zircon (DZ) U‐Pb and He ages from the Lajas and Los Molles Formations in Lohan Mahuida and La Jardinera areas suggest a late Middle Jurassic depositional age. The DZ U‐Pb provenance analysis confirms that both formations are part of the same Middle Jurassic shelf margin and were both sourced from the Choiyoi basement, Late Triassic to Middle Jurassic Andean magmatic arc and pre‐Cuyo Group strata. The detrital He (DZHe) ages provide additional provenance constraints by recording three discrete cooling events, (1) early‐Late Triassic, (2) early‐Early Jurassic, and (3) Middle‐Late Jurassic, documenting tectonically driven exhumation during rifting and contractional stages prior to and during early Neuquén basin evolution. Triassic‐Jurassic He cooling ages of zircons derived from the Choiyoi Group document the existence of pre‐Cuyo Pangean extensional structures and basins in the source area. Furthermore, the abundance of rapidly cool DZHe ages requires rapid exhumation of both Choiyoi and Carboniferous basement. All of this evidence suggests that structural inversion in the Huincul ridge region started in the Middle Jurassic, earlier than previously proposed. Hence, this challenges conventional Cuyo Group tectono‐depositional models that advocated postrift thermal sagging as the primary control on subsidence and deposition. The occurrence of first‐cycle volcanic (U‐Th)/(He‐Pb) ages implies that the Cuyo Group burial never reached depths >4–5 kilometres. Exhumation to shallower crustal depths was spatially partitioned and driven by Cenozoic Andean shortening as constrained by AHe ages.
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