资源环境科技发展态势分析平台

Slab rollback processes alter the intraplate force balance and buoyancy of the overriding plate, driving surface uplift or extension. From ca. 55-24 Ma, Farallon slab rollback produced migrating volcanism and sedimentation across the western United States as stress on the North American plate transitioned from subduction-driven compression to widespread extension. Hypotheses regarding rollback-driven surface deformation differ widely in timing and magnitude. Here we combine hydrogen isotope ratios with high-resolution geochronology to show that a high-elevation plateau extended westward from the Sevier-Laramide fold-thrust belt across Utah and eastern Nevada prior to slab rollback. Quantitative paleoelevation estimates show that this plateau had obtained over 80% of peak paleoelevations by middle Eocene. Slab rollback, heating, and lithospheric delamination generated 400-600 m of Oligocene surface uplift. Concurrent extension limited overall uplift and rollback-induced mantle flow likely contributed to the propagation of upper crustal extension that formed the Basin and Range province.

Plain Language Summary Changes in surface elevations are critical to understanding the formation and evolution of mountains and basins across ancient landscapes. Slab rollback-retreat and steepening of the downgoing tectonic plate during subduction-can transform Earth's surface by altering the stresses on the overriding plate. By measuring the ratios of hydrogen isotopes in ancient rainwater, preserved for millions of years in volcanic ash, we can estimate past elevations. Here we measure past elevations across the Basin and Range province of Utah and Nevada to reconstruct topography before and during slab rollback. Results show that a high elevation plateau extended westward from the western edge of the Rocky Mountains across Utah and eastern Nevada prior to slab rollback. Slab rollback generated a short-lived interval of 400-600 m of surface uplift, much less than has been previously estimated. Instead, subsequent processes resulting from rollback likely contributed to collapse of the high plateau and the widespread extensional faulting that created the characteristic topography of the modern Basin and Range province.