The results of new detrital zircon analyses of 15 (n = 1334) Sevier belt synorogenic (Jurassic–Eocene) conglomerates combined with U-Pb zircon ages from the literature (n = 2638) support the structurally dynamic role of the western Paris thrust sheet as the dominant high-standing, out-of-sequence portion of the Sevier belt. This result requires modification of the traditional structural view of the thin-skinned Sevier fold-and-thrust belt having formed by west-to-east shortening over an ~100-m.y. period (ca. 150–50 Ma) with episodic thrust motions that become younger toward the craton (east), as constrained by numerous synorogenic deposits shed to the east...