Has the Eastern End of the Uinta Mountains Been Bent?: Paleomagnetic and Fault Kinematic Assessment

摘要: Abstract Hematite-cemented strata of the Neoproterozoic-age (~ 900 to 750 Ma) Uinta Mountain Group (UMG) provide paleomagnetic data that can be used test hypothesis easternmost Mountains, northwest Colorado and northeast Utah, experienced clockwise sense rotation in response Laramide crustal shortening. In north-central Flaming Gorge area, UMG bedding strikes east-west northwest-southeast has characteristic remanent magnetizations (ChRMs) west declination shallow inclination (as well as an antipodal magnetization). Examples (in stratigraphic coordinates) include Carter Creek locality (Decl.= 266.0°, Incl.= −8.0°, α95 = 5.4°, pole 5.8°S, 160.1°E, N 5 sites); Dowd Springs folded 269.0°, −11.8°, 11.5°, 4.8°S, 156.5°E, 6 unfolded 101.8°, −6.9°, 13.4°, 11.3°S, 155.6°E, dam 272.7°, −6.3°, 9.8°, at 0.0°S, 156.6°E, Sheep Canyon (Decl. 96.2°, −5.6°, 4.7°, 6.6°S, 158.4°E, 23 sites). This magnetization is interpreted a primary, Neoproterozoic magnetization, acquired when Laurentia was low, equatorial latitudes, during early stages breakup Rodinia supercontinent. eastern structural trends have north-south trend two sampling localities ChRM directions with declinations shallow, negative positive inclinations coordinates, Bull yields mean Decl.= 272.0°, 9.0°, α95= 5.9° (pole 4.4°N, 163.3°E, 9 sites) Talamantes - Sparks 87.9°, −9.9°, 8.2° 1.9°S, 166.4°E, 12sites). Many additional carry only north-directed steep remanence, which secondary after end deformation. At other localities, this pervasive remanence unblocked stepwise thermal demagnetization reveals ancient (or its east-directed antipode) higher unblocking temperatures. Comparison ChRMs from central shows no statistically significant vertical axis rocks between areas. Fault kinematic data, collected selected Mesozoic part range, are show evidence for left-lateral transpression and, least locally, horizontal, NW-SE directed maximum shortening direction. The indicate Laramide-age deformation Mountains proceeded without rotation, map-scale curvature observed today likely due reactivation pre-existing, rift-related grain, rather than reflection considerable left-slip adjacent, buttressing parts foreland.