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Reference
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| Title: |
Report on Referred Fossils
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1978
(10/23)
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| Report by: |
Norman J. Silberling
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| Referred by: |
George Plafker
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| | Age: | Carnian |
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| Comment: | These fossils are better preserved than the much qualified identifications as listed would indicate. Although the Halobias and kinds of ammonites represented dictate a Karnian age, the ammonites especially are unusual forms not like those from well known North American faunas of the this age. Their closest look-alikes are Alpine species described from occurrences in the Hallstatt-facies limestones. Unfortunately, these occurrences are known to be stratigraphic mixtures owing to the effects of diagenetic dissolution and condensation, so their age significance is muddled. In North America the genus HOPLOTROPITES is restricted to rocks of late Karnian age, and the other kinds of ammonites and bivalves in the present collection could also be of this age. Given the inprecision in dating this collection, the greenstones from which it was obtained could be as old as the uppermost part of the Nikolai Greenstone or as young as the oldest parts of the Hound Island Volcanics. They are, however, definitely older than the upper Norian pillow basalts such as those in the so-called Susitna terrane of the Alaska Range. After unpacking this collection and mixing the specimens, I realized that one bag was labelled 78APr131 plus the word "Ammonites." Was this a separate collection different from the remainder of 78APr136?, Collection - 136 is the only one mentioned on the transmittal sheet? [Note by R.B. Blodgett, this last comment was followed by handwritten comment "136 should be 131" which was initialled by GP.]
[Additional note by R.B. Blodgett, Norm Silberling's - The USGS "Triassic Collection" index shows that USGS Mesozoic loc. D10560 corresponds to field localities 78APr130 and 131] |
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