Abstract
Northward transport of the Yakutat terrane along the Transition
and Queen Charlotte-Fairweather transform faults led to Neogene
collision of the Yakutat terrane with the southern continental
Alaska margin. Northward translation resulted in a stratigraphy
that records the erosion of thermotectonic terranes along its
path. The strata of the Yakutat terrane includes the Lower
Oligocene to Lower Eocene Kulthieth Formation, the Upper Eocene to
Lower Miocene Poul Creek Formation and the Miocene-Pleistocene
Yakataga Formation. Detrital zircon fission-track (DZFT) ages from
stratigraphically coordinated samples collected in the Northern
Robinson Mountains yield provenance information of the units that
can shed light on their transport history. For all dated samples
50 grains were counted and morphology/color noted and grain ages
were deconvolved into component populations. The Kulthieth
Formation has three primary cooling age populations at ~70-97 Ma,
38-58 Ma and 28-31 Ma. The Poul Creek Formation has three primary
cooling age populations at ~61-67 Ma, 39-42 Ma and 24-33 Ma. The
Yakataga Formation has three primary cooling age populations at
~68-77 Ma, 30-35 Ma and 15-21 Ma. The DZFT grains were then
analyzed by LA-ICPMS to determine U/Pb crystallization ages. For
the Yakataga Formation three crystallization peak age populations
resulted: ~52 Ma, ~71 Ma and ~155 Ma. For the Poul Creek Formation
four crystallization peak ages resulted: ~59 Ma, ~71 Ma, ~94 Ma,
and ~147 Ma. Three grains yielded U/Pb ages of ~318 Ma, ~365 Ma,
~1864.71 Ma. Analysis of the Kulthieth Formation resulted in three
U/Pb crystallization age populations of ~59 Ma, ~94 Ma, and ~159
Ma.
Paleocene to Eocene deposition of the Yakutat terrane stratigraphy
records a long-lived, non-volcanic source terrain that
crystallized from ~50-220 Ma and cooled from ~48-110 Ma. Miocene
cooling episodes in the Kulthieth and the Poul Creek Formations
likely records deposition associated with plutons located in the
northern Coast Plutonic Complex and the Kuiu-Etoilin belt in the
North American Cordillera. Late Miocene deposition of the Yakataga
Formation records a provenance signal of crystallization from
~50-53 Ma and cooled from ~17-20 Ma. Late Miocene deposition is
likely associated with the Chugach accretionary complex and
superimposed Sanak-Baranof Plutonic Belt (~50-58 Ma).
The uniform provenance of the Kulthieth and Poul Creek Formations,
the overall grain-age distribution, and the distinct lack of
volcanic zircons favors northern reconstructions (i. e. Plafker et
al., 1994) for the original position of the Yakutat terrane.
Southern options (i.e. Bruns, 1982), can be ruled out mainly due
to the lack of volcanic grains that would be expected in the
stratigraphy during continuous transport of the terrane along
route.
Perry, Stephanie E., 2006. Thermochronology and provenance
of the Yakutat terrane, southern Alaska based on fission-track and
U/Pb analysis of detrital zircon.
Unpublished MSc. thesis, State University of New York at
Albany. 376 pp., + xiii
University at Albany Science Library call number: SCIENCE
Oversize (*) QE 40 Z899 2006 P47
thesis (scanned
text) - 24.4MB pdf file [p. 1-152, +xii]
Appendix 1 - Zeta Calculations, Fluence
Calculations, Irradiation Order - 0.9MB pdf file [p.
153-187]
Appendix 2 - Fission Track Ages -
2.8MB pdf file [p. 188-266]
Appendix 3 - Detrital Zircon Fission Track
Grain Characteristics - 1.1MB pdf file [p. 267-283]
Appendix 4 - Binomial Peak-fit Ages -
2.0MB pdf file [p. 284-316]
Appendix 5 - Digital photographs taken of
individual zircon grains for the double-dating procedure -
39.3MB pdf file [p. 317-356]