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Article Abstract:

The reasons for the objection to the premature use of Pessagno and Blome's paleogeographic model in characterizing terrane motions are presented. Pessagno and Blome claimed that multiple criteria are preferable for paleogeographic analyses but added that 'radiolarian paleobiogeographic reconstructions are useful and can stand alone.' In the case of the Stanley Mountain sequence, multiple criteria cannot be applied for biogeographic analyses since the sequences contain only radiolarians. Thus, the model is not reliable when applied to actual stratigraphic sections.

Models, California, Paleobiogeography, Ophiolites, Chert

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Article Abstract:

The article by William Outerbridge questioned the Fire Clay compendium with regard to recent findings on silica-melt inclusions, age and stratigraphy, and thickness of Fire Clay tonstein. The Lyons et al. study used techniques which resulted in contaminations and altered mineral grains. Webster et al. used geochemistry, which cannot replace physical stratigraphy and careful sampling technique. The findings by these studies do not necessarily make earlier hypotheses obsolete, since the Lyons et al. study does not claim to be absolute.

Volcanic ash, tuff, etc., Volcanic rocks

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Article Abstract:

Hanson argued that the McAfee Creek pluton, which has a U-Pb age of 100 plus or minus 1 Ma, indicates that nearly all of the intrusions in the northern White Mountains, CA, were emplaced approximately 15 m.y. before the Cretaceous Period. However, local geologic relationships, the pattern of regional metamorphism and regional evidence reveal that reset ages generally represent the local heating effects created by intrusion of younger plutons.

Sierra Nevada (United States), Granite, White Mountains (New Hampshire), Intrusions (Geology)

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