Southeastern Alaska tectonostratigraphic terranes revisited
The presence of only three major tectonostratigraphic terranes (TSTs) in southeastern Alaska and northwestern British Columbia (Chugach, Wrangell, and Alexander) is indicated by critical analysis of available age, stratigraphic, and structural data. A possible fourth TST (Stikine) is probably an equivalent of part or all of the Alexander. The Yakutat block belongs to the Chugach TST, and both are closely linked to the Wrangell and Alexander(-Stikine) TSTs; the Gravina TST is an overlap assemblage. THe Alexander(-Stikine) TSTs is subdivided on the basis of age and facies. The subterranes within it share common substrates and represent large-scale facies changes in a long-lived island-arc environment. The Taku TSTs is the metamorphic equivalent of the upper part (Permian and Upper Triassic) of the Alexander(-Stikine) TSTs with some fossil evidence preserved that indicates the age of protoliths. Similarly, the Tracy Arm TST is the metamorphic equivalent of (1) the lower (Ordovician to Carboniferous) Alexander TST without any such fossil evidence and (2) the upper (Permian to Triassic) Alexander(-Stikine) with some newly discovered fossil evidence. Evidence for the ages of juxtaposition of the TSTs is limited. The Chugach TST deformed against the Wrangell and Alexander TSTs in late Cretaceous. Gravina rocks were deformed at the time and also earlier. The Wrangell TST was stitched to the Alexander(-Stikine) by middle Cretaceous plutons but may have arrived before its Late Jurassic plutons were emplaced. The Alexander(-Stikine) and Cache Creek TSTs were juxtaposed before Late Triassic.
- Research Organization:
- Geological Survey, Menlo Park, CA
- OSTI ID:
- 6461377
- Report Number(s):
- CONF-8505215-
- Journal Information:
- Am. Assoc. Pet. Geol., Bull.; (United States), Journal Name: Am. Assoc. Pet. Geol., Bull.; (United States) Vol. 69:4; ISSN AAPGB
- Country of Publication:
- United States
- Language:
- English
Similar Records
Magmatic and metamorphic belts and plutonic-metamorphic complexes of southeastern Alaska
U/Pb geochronologic and petrologic studies in the Blue Mountains terrane, northwestern Oregon and westernmost central Idaho: implications for pre-Tertiary tectonic evolution
Related Subjects
020200* -- Petroleum-- Reserves
Geology
& Exploration
ALASKA
BRITISH COLUMBIA
CANADA
CRETACEOUS PERIOD
FEDERAL REGION X
FOSSILS
GEOLOGIC AGES
GEOLOGIC FORMATIONS
GEOLOGIC HISTORY
GEOLOGY
IGNEOUS ROCKS
MESOZOIC ERA
METAMORPHIC ROCKS
NORTH AMERICA
ORDOVICIAN PERIOD
PALEOZOIC ERA
PERMIAN PERIOD
ROCKS
SEDIMENTARY ROCKS
STRATIGRAPHY
TECTONICS
TRIASSIC PERIOD
USA