Late Cretaceous extension in the hinterland of the Sevier thrust belt, northwestern Utah and southern Idaho

Journal Article · Mon Oct 01 04:00:00 EDT 1990 · Geology; (USA)

DOI:https://doi.org/10.1130/0091-7613(1990)018<0929:LCEITH>2.3.CO;2· OSTI ID:6140142

Wells, M L; Allmendinger, R W ^[1]; Dallmeyer, R D ^[2]

---

1. Cornell Univ., Ithaca, NY (USA)
2. Univ. of Georgia, Athens (USA)

Cover rocks of the Raft River metamorphic core complex, located in the Sevier belt hinterland, preserve a structural and metamorphic history that predates the middle Tertiary extension of the region. In the eastern Raft River Mountains, Cambrian( )-Permian rocks form two allochthons that occur in the hanging wall of the mid-Miocene Raft River detachment fault. Dramatically attenuated, metamorphosed Cambrian( )-Pennsylvanian strata of the lower allochthon yield Late Cretaceous muscovite {sup 40}Ar/{sup 39}Ar plateau ages (ca. 82-90 Ma) that are interpreted to date cooling during final stages of layer parallel extension. Devonian-Permian rocks exposed in the Black Pine Mountains underwent east-west extension ({approximately} 160%) associated with syntectonic growth of white mica along cleavage. {sup 40}Ar/{sup 39}Ar whole-rock spectra of associated slates also indicate a Late Cretaceous metamorphism. Together, field and {sup 40}Ar/{sup 39}Ar results suggest that Late Cretaceous extension occurred in the Sevier belt hinterland at the same time as shortening in the eastern foreland and at depth in the hinterland. Sufficient topography must have been present to drive upper-crustal extension in the eastern hinterland.

• OSTI ID: 6140142
• Journal Information: Geology; (USA), Journal Name: Geology; (USA) Vol. 18:10; ISSN GLGYB; ISSN 0091-7613
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580000* -- Geosciences
AGE ESTIMATION
ARGON 39
ARGON 40
ARGON ISOTOPES
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
CAMBRIAN PERIOD
CARBONIFEROUS PERIOD
CRETACEOUS PERIOD
DEVONIAN PERIOD
EVEN-EVEN NUCLEI
EVEN-ODD NUCLEI
FEDERAL REGION VIII
FEDERAL REGION X
GEOLOGIC AGES
GEOLOGIC DEPOSITS
GEOLOGIC FAULTS
GEOLOGIC FORMATIONS
GEOLOGIC FRACTURES
GEOLOGIC HISTORY
GEOLOGIC STRUCTURES
IDAHO
ISOTOPE DATING
ISOTOPE RATIO
ISOTOPES
LIGHT NUCLEI
MESOZOIC ERA
METAMORPHIC ROCKS
METAMORPHISM
MICA
MOUNTAINS
NORTH AMERICA
NUCLEI
PALEOZOIC ERA
PERMIAN PERIOD
RADIOISOTOPES
RIVERS
ROCKS
STABLE ISOTOPES
STREAMS
SURFACE WATERS
TECTONICS
USA
UTAH
WESTERN US OVERTHRUST BELT
YEARS LIVING RADIOISOTOPES