ABSTRACT
The Bay of Islands Ophiolite Complex forms a discontinuous belt of
highly allochthonous mafic and ultramafic massifs in southwestern
Newfoundland. The North Arm Mountain Massif contains the only
significant exposures of sedimentary rocks overlying the ophiolite
and also contains the most extensive exposures of plutonic rocks
in the Bay of Islands Complex. Mapping has shown that sedimentary
rocks, here named the Crabb Brook Group, rest with a pronounced
erosional unconformity on ophiolitic rocks.
Lithologic,paleontologic, facies, structural, and tectonic
relationships indicate that this Group was deposited on the back
of the ophiolite allochthon as it was being obducted onto the
early Paleozoic Continental Margin. These sedimentary rocks may
correlate with others associated with ophiolites in the Northern
Appalachians which, as yet, are of unknown age and affinity.
Regional tectonic and paleogeographic relationships in Western
Newfoundland allow evaluation of the obducticn process and models
are developed to explain features which are common to many
obducted ophiolite bodies. Many features observed in the plutonic
complex of the North Arm Massif are inconsistent with models of
ophiolite generation which involve small multiple magma chambers
and in many cases are contrary to the notion that the majority of
layered plutonic rocks were formed by differential settling and
accumulation. A combination of field, structural, and petrographic
relationships indicate that the bulk of the North Arm Plutonic
section formed as a result of in situ nucleation and crystal
growth on the bounding surfaces of a continuously evolving,
chemically zoned, steady state magma chamber.
Casey, J.F., 1980. The geology of the southern part of the North
Arm Mountain Massif, Bay Of Islands Ophiolite Complex, Western
Newfoundland with application to ophiolite obduction and the
genesis of the plutonic portions of oceanic crust and upper
mantle. Unpublished PhD dissertation, State University of
New York at Albany. 620pp.(2 vol.), +xxii; 1 folded plate (map)
University at Albany Science Library call number: SCIENCE
MIC Film QE 40 Z899 1980 C37
Copies of this PhD dissertation can be ordered
from Proquest UMI
Front matter (title,
table of contents, abstract, acknowledgements) - 1MB pdf
file
Photo pages in dissertation
(colour photos with captions): Vol
1 photos - 22.8MB pdf file; Vol
2 photos - 19.8MB pdf file
Plate 1 - Geological
map of the North Arm Massif, southern half, Bay of Islands
Ophiolite Complex, Newfoundland, Canada
(uncoloured geological outcrop map; scale
~1:15,840) 7.4MB pdf file
see also: Casey, J.F., and Rosencrantz, E.J., 1981. Geological
map of the North Arm Massif, Bay of Islands Ophiolite Complex,
Newfoundland, Canada
(uncoloured geological map; scale 1:28,800)
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