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]