C. E. Brown
T. P. Thayer
1964
<p>Pre<span>-</span>Tertiary<span> rocks of the Blue Mountain region of </span>central<span> and </span>northeastern<span> </span>Oregon<span> comprise three major sedimentary and volcanic sequences and two distinct </span>intrusive<span> magma series. The ages of the sedimentary-volcanic sequences are Paleozoic, Late Triassic-Late Jurassic, and middle Cretaceous (Albian to Cenomanian), respectively. The earlier </span>intrusive<span> magma series ranges </span>in<span> composition from peridotite to albite granite and was emplaced during the major orogeny </span>in<span> the Blue Mountain region between earlier Permian and Late Triassic time. The later </span>intrusive<span> magma series is related to the Idaho batholith proper, ranges from gabbro to granodiorite, and probably was emplaced during the earlier half of Cretaceous time. The emplacement of a major </span>intrusive<span> magma series during Permian and Triassic time suggests a much closer relationship to the northern part of the Cordillera, </span>in<span> Canada and Alaska, than to the southern part </span>in<span> southwestern </span>Oregon<span> and California. </span></p>
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10.1130/0016-7606(1964)75[1255:POAPIA]2.0.CO;2
en
Geological Society of America
Pre-tertiary orogenic and plutonic intrusive activity in central and northeastern Oregon
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