Abstract
This dissertation consists of four independent
yet related projects: 1) the petrology, geochemistry, and original
tectonic setting of the Galice Formation, Klamath Mountains,
Oregon-California; 2) the geochemistry, tectonic setting, and
possible regional correlations of the Iron Mountain and Esmeralda
Peaks units of the Ingalls ophiolite complex, central Cascades,
Washington; 3) the provenance and original tectonic setting
of sedimentary serpentinites and ophiolite breccias within the
sedimentary rocks of the Ingalls ophiolite complex; and 4)
geology, tectonics, and possible regional correlations of
pre-Cenozoic rocks, central Cascades, Washington.
This research indicates that the Galice
Formation represents continuous Late Jurassic deposition
(Oxfordian-Kimmeridgian), within the Josephine backarc
basin. Source areas for the Galice Formation included active
Jurassic arcs, older Klamath terranes, and the North American
craton.
The Early Jurassic Iron Mountain unit of the
Ingalls ophiolite complex originated as a seamount in close
proximity to an oceanic spreading ridge. The Late Jurassic
Esmeralda Peaks unit of the Ingalls ophiolite complex originated
in a backarc basin that included a fracture zone. The Iron
Mountain unit is the rifted basement of the Esmeralda Peaks unit,
and both units correlate to similar rocks within the Klamath
Mountains.
Cr-spinel compositions, geochemistry, and
petrography indicate that sedimentary serpentinites and ophiolite
breccias within the Ingalls sedimentary rocks were locally
derived. These rocks were originally deposited in a Late
Jurassic fracture zone.
The Manastash inlier consists of the Hereford
Meadow amphibolite, Lookout Mountain Formation, Quartz Mountain
stock, and Helena-Haystack mélange. Hereford Meadow
amphibolite is, in part, a dismembered pre-Jurassic ophiolite that
originated in a supra-subduction zone setting. The Lookout
Mountain Formation is Late Jurassic in age, had cratonic sources,
and was originally located in the Klamath Mountains region,
Oregon-California. The Quartz Mountain stock is Late
Jurassic in age, and the remnants of an island arc. The
Helena-Haystack mélange is a major suture between Cascade
terranes, and suggests that ~98 km of right-lateral displacement
has occurred along the Straight Creek fault.
The De Roux unit consists of metaigneous and
metasedimentary rocks. Metaigneous rocks have calc-alkaline,
within-plate, and mid-ocean ridge basalt affinities. The De
Roux unit correlates with other Cascade mélanges.
MacDonald, J. H., 2006. Petrology, Petrogenesis, and Tectonic
setting of Jurassic rocks of the Central Cascades, Washington, and
Western Klamath Mountains, California-Oregon. Unpublished PhD
dissertation, State University of New York at Albany. 415pp.,
+xix; folded map in pocket
University at Albany Science Library call number: SCIENCE
MIC Film QE 40 Z899 2006 M33
Copies of this PhD dissertation can be ordered
from Proquest UMI
Front matter (title,
table of contents, abstract, acknowledgements) - 0.2MB pdf
file
Figure pages in dissertation
(colour
and greyscale photos and figures, with captions): - 3.1MB
pdf file
Plate 1 - Geologic
map
of the southern part of the Manastash Inlier (coloured
geological map and cross-sections; scale 1:12.000)
Map figures from PhD
dissertation - New
Mapping
within the Wenatchee Mountains, central Cascades, Washington
(Ingalls Ophiolite)
(geological maps, various scales from ~1:15,000 to 1:82,000; 3
greyscale, 1 coloured)
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in the Geological Sciences Program, University at Albany