Structural evolution of the northern Blackfoot Mountains, southeastern Idaho
The Blackfoot Mountains, located on the southeast margin of the Snake River Plain near Idaho Falls, Idaho, contain an extensive record of Late Mesozoic deformation, generated during the formation of the Idaho-Wyoming fold-thrust belt. Pre-Late Cenozoic rocks have been divided into four tectonic units consisting of three major imbricate slices of the Meade allochthon and the lower plate. The basal decollement for the Meade thrust is at the base of the Mississippian System. The data suggest the following structural history: (1) initial layer parallel compressions by regional east-northeast trending, sub-horizontal maximum compressive stress; (2) buckle folding with limb shortening by bedding plane slip; (3) early development of fold asymmetry; (4) locking of folds when the steep limb was 50 to 70/sup 0/ to maximum compressive stress; (5) continued shortening and rotation of overturned limbs by cataclasis ad minor thrusting; (6) propagation of the imbricated thrust faults and translation of allochthons with little additional internal strain; and (7) locking of thrusts due to reorientation of local stress fields. Four sets of Late Cenozoic high angle faults offset all thrust belt structures. Typical Basin and Range style uplift occurred along the oldest north-northwest trending range front faults on the west side of the mountains, and secondarily on cross-cutting east trending hinge faults. The third set of faults parallels the Snake River Plain, while the youngest northwest trending faults are perpendicular to the Plain. These relations suggest that Basin and Range structures are older than the Snake River Plain west of the Blackfoot Mountains.
- Research Organization:
- Stanford Univ., CA (USA)
- OSTI ID:
- 5376576
- Country of Publication:
- United States
- Language:
- English
Similar Records
Structure and geologic history of late Cenozoic Eel River basin, California
Impact of late Cenozoic extension on Laramide overthrust belt and Diablo Platform margins, northwestern Trans-Pecos Texas
Related Subjects
580100* -- Geology & Hydrology-- (-1989)
BIOLOGICAL EVOLUTION
CENOZOIC ERA
DEFORMATION
FEDERAL REGION X
GEOLOGIC AGES
GEOLOGIC FAULTS
GEOLOGIC FRACTURES
GEOLOGIC HISTORY
GEOLOGIC STRUCTURES
IDAHO
LAYERS
MISSISSIPPIAN PERIOD
MOUNTAINS
NORTH AMERICA
PALEONTOLOGY
PALEOZOIC ERA
SNAKE RIVER PLAIN
TECTONICS
USA