| Sample: |
Sample No. 60ABa732 -- USGS No. USGS Mesozoic locality M1020
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| Locality: |
Field No. 60ABa732
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| Description: |
About 7 miles south of mouth of Nation River, along west bank of Trout Creek opposite mouth of tributary from east. Coordinates (8.9, 6.2). (description from Silberling E&R report); Upper Yukon, east-central Alaska; Charley River A-2 1:63,360 quadrangle; about 7 miles south of mouth of Nation River; west banks of Trout Creek opposite mouth of tributary from east; lat 65°05.3' N., long 141°41.7' W. Coll.: E.E. Brabb, 1960, field No. 60ABa732. [In rocks not included among the Phanerozoic accretionary terranes] (description from Silberling et al., 1997, p. 19-20); Grant-Mackie and Silberling, 1990, p. 254, provides the following: " USGS Mesozoic loc. M1020. Upper Yukon, east-central Alaska; Charley River A-2 1:63,360 quadrangle; about 7 miles (11.3 km) south of mouth of Nation River; west bank of Trout Creek opposite mouth of tributary from east; lat. 65°05.3'N., long. 141°41.7'W. Coll.: E. E. Brabb, 1960, field no. 60ABa732. Ancestral North America (i.e., rocks not regarded as an accreted terrane).' |
| Location: |
Alaska Quadrangle: Charley River A-2 Township&Range: T3N R30E Section: NW 1/4 sec. 17
Lat.: 65o05.3 ' Long.: 141o41.7 ' |
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Reference
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| Title: |
Report on Referred Fossils
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1960
(10/10)
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| Report by: |
Norman J. Silberling
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| Referred by: |
Earl E. Brabb
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| | Age: | Carnian-Norian (late Carnian - early Norian) |
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| Comment: | Age (excluding the Monotis): late Karnian or early Norian on the basis of the Halobia present and the species of Rhynchonella in common with the collection from M1019. The slab with Monotis salinaria, as I understand it, is from a short distance stratigraphically above the rest of this collection and is indicative of a somewhat younger Norian age. Some paleontologists claim that in Alaska and Canada there are several stratigraphically successive species of Monotis, of which forms like M. salinaria are the oldest. This suggestion, however, has not yet been documented. |
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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
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J. A. Grant-Mackie
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K. M. Nichols
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| | Age: | Norian (late middle Norian) |
| Formation: | Glenn Shale |
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| Comment: | Plate 6 explanation: Monotis (Eomonotis) daonelliformis. …… 5. Left valve from USGS Mesozoic loc. M1020 (approximately same locality as M1714). --- "In east-central Alaskan strata, Monotis shells are so abundantly stacked together that the compression has impressed one shell into another forming a confused patter of interfering ribbing and incomplete shell outlines (pl. 6, fig. 13; pl 7, figs. 1-2). The abundance of shells themselves makes it difficult to obtain positively identifiable specimens. Species of Eomonotis, such M. (Eo.) daonellaeformis (listed by Silberling as M. "scutiformis typica" in Brabb, 1968, p. 112) and probably M. (Eo.) pinenensis, are particularly well represented. In younger beds, specimens that belong to M. (P.) subcircularis are well represented, although invariably poorly preserved. Other late Norian species are not known, most lackly because of lack of exposure." (Silberling et al., 1997, p. 9). ----- "In the Upper Yukon, M. (Eo. daonellaeformis (loc. M1714; pl. 6, figs. 1-5) occurs 3-10 m below M. (Eo.) ?pinensis (loc. M1715; pl. 6, figs. 6-16). This is the only unquestioned occurrence of M. (Eo.) daonelliformis in Alaska, but in northeastern Asia, Dagys and others (1979) define a M. daonellaeformis subzone of the "M. scutiformis zone,", overlain by a M. pinensis subzone." (Silberling et al., 1997, p. 12-13) |
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