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Reference
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| Title: |
The Late Triassic Bivalve Monotis in Accreted Terranes of Alaska
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1997
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ABSTRACT--Late Triassic bivalves of the genus Monotis occur in at least 16 of the lithotectonic terranes and subterranes that together comprise narly all of Alaska, and they also occur in the Upper Yukon region of Alaska where Triassic strata are regarded as representing non-accretionary North America. On the basis of collections made thus far, 14 kinds of Monotis that differ at the species or subspecies level can be recognized from Alaska. These are grouped into the subgenera Monotis (Monotis), M. (Pacimonotis), M. (Entomonotis), and M. Eomonotis. In places, Monotis shells of one kind or another occur in rock-forming abundance. On the basis of superpositional data from Alaska, as well as from elsewhere in North America and Far Eastern Russia, at least four distinct biostratigraphical levels can be discriminated utilizing Monotis species. Different species of M. (Eomonotis) characterizes two middle Norian leves, both probably within the upper middle Norian Columbianus Ammonite Zone. |
| Report by: |
Norman J. Silberling
,
J. A. Grant-Mackie
,
K. M. Nichols
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| | Age: | Norian (middle Norian) |
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| Comment: | Stratigraphic relationships of the collections from this area [referring to Port Graham - note by RBB] are not known, but in rocks of teh same character as those in which the late Norian fossils occur, the characteristic middle Norian flat clams Halobia lineata and H. dilitata occur in separate collections (respectively, USGS Mesozoic locs. 6380 and 6382) as does the late middle Norian ammonite Steinmannites (from USGS Mesozoic loc. D13388). |
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