The Sevier Fold and Thrust Belt in Utah

When considered together, available age constraints suggest the Central Nevada Thrust Belt, Eastern Nevada Fold Belt, and the Western Utah Thrust Belt are intimately related to the Canyon Range thrust in time. The similar timing suggests that these structural elements are together connected to the Luning-Fencemaker fold thrust belt (LFTB) via a shared decollement. If this correlation is correct, the initiation of the LFTB began the first eastward propagation of the Sevier orogeny at 165 Ma. Then, about 150 Ma, eastward propagation was transferred on the decollement and rapidly progressed to create several moderate displacement fold and thrust systems (CNTB, ENFB, WUTB) that moved with the large displacement Canyon Range thrust (146 Ma initiation of the western system of the Sevier frontal thrust belt). Propagation was transferred to the Pavant thrust of the western system around 110 Ma, and from the Pavant thrust to the eastern system frontal thrusts about 98 to 90 Ma. Regional thrusting was terminated by 50 Ma when movement of the system ceased.

Chapter 1 describes the Western Utah Thrust Belt and its geologic history. Chapter 2 describes the type Sevier orogenic belt and its structural setting including the Canyon Range conglomerate and history of Sevier thrusting. Chapter 3 discusses the Sevier fold and thrust belt deformation along its leading edge. Chapter 4 presents evidence of exhumation of the Willard Thrust. Chapter 5 describes the eastward translation of the Sevier thrust in northwestern Utah and southwestern Wyoming. Chapter 6 presents the depositional stratigraphy encountered during the road log portion presented in Chapter 7. Chapter 7 presents a road log of the Sevier thrust with many photographs.