2444 and 2444a. Yukon River above Circle. (The description is inadequate but almost surely represents the Nation River locality.) Collector, J. E. Spurr. 2AC55. Yukon River, north bank 3 miles above mouth of Seventymile River. Collector, A. J. Collier. (No Permian rocks are known at this locality; either the locality is wrongly recorded, or the faunal and age determinations are incorrect.) 2443. Yukon River, west bank 3 miles above Nation River. Collector, A. J. Collier. 2445. Limestone mountain 11⁄2 miles northeast from mouth of Nation River. Collector, A. J. Collier. Collier 1902. (Ambiguous wording in description of locality. Interpreted by the writer to mean float found along the Yukon at the mouth of Washington Creek.) Collector, A. J. Collier. 2441. Yukon River, west bank 3 miles above Nation River. Collector, Arthur Hollick. Brooks 12. Yukon River, southwest bank 1 mile below Tatonduk River. Collector, A. H. Brooks. (No Permian rocks are known at this locality, and the writer is inclined to believe that this locality also is wrongly recorded.) 2446. Yukon River, south bank 6 miles above Nation. Collector, A. H. Brooks. (This collection probably comes from the Trout Creek locality.) 2447. Yukon River, north limb of anticline opposite station 14. Collector, A. H. Brooks. (This collection is undoubtedly from the north side of the limestone band at Nation River.) 2448. Yukon River three-quarters of a mile below Coal Creek. Collector, A. H. Brooks. 427. Michigan Creek, west side about 6 miles from mouth. Collector, J. B. Mertie, jr. 428. Michigan Creek, west side about 3 miles from mouth. Collector, J. B. Mertie, jr. Martin 82. Yukon River, south bank 2 miles above Nation River. Collector, G. C. Martin. Martin 83. Yukon River, south bank 11⁄2 miles above Nation River. Collector, G. C. Martin. 1799, 1799a, and 1799b. Yukon River, southwest bank 8 miles above Nation River. Collector, Eliot Blackwelder. 1800, 1800a, and 1800b. Yukon River, west bank above Nation River. Collector, Eliot Blackwelder. 1801. Yukon River, south bank just below Coal Creek. Collector, Eliot Blackwelder. 2437, 2437a, and 2437b. Yukon River, west bank opposite mouth of Nation River. Lowest part of middle outcrop of Permian sandstone, with 15 feet of shales, but from several horizons. Collector, G. H. Girty. 2438. Yukon River, west bank opposite mouth of Nation River. Middle outcrop of Permian limestone, above lots 2437, 2437a, and 2437b, but in transition beds below main white limestone. Collector, G. H. Girty. 2439. Same general locality as 2438, but from a more shaly stratum just above 2438. Collector, G. H. Girty. 2440. Same general locality as 2438, but from base of a heavy limestone 10 feet above 2439. Collector, G. H. Girty. 2440a. Same general locality as 2438, but from the very top of the white limestone as exposed. Collector, G. H. Girty. 2442, 2442a, 2442b, 2442c, and 2442d. Yukon River, west bank opposite mouth of Nation River. Talus from several horizons. Collector, G. H. Girty. 2543. Yukon River, south bank three-quarters of a mile below mouth of Coal Creek. Collector, G. H. Girty. 2549. Yukon River, west bank opposite mouth of Nation River. horizons in lowest outcrop of Permian limestone. Collector, G. H. Girty. Various 5839, 5839a, 5839b, and 5839c. Yukon River, southwest bank about 24 miles upstream from Nation. The positions of these four localities in the Permian stratigraphic section were closely determined. Collector, J. B. Mertie, jr. 5840. Southeast side of valley of Nation River about 1 mile northeast of Yukon River. Collector, J. B. Mertie, jr. 5841. Yukon River, southwest bank about three-quarters of a mile downstream from mouth of Coal Creek. Collector, J. B. Mertie, jr. 5842. Southeast side of valley of Nation River about 5 miles northeast of Yukon River. Collector, J. B. Mertie, jr. In addition to the fossils tabulated, at least three of the fossil collections made by Cairnes along the international boundary are also now recognized by Girty as Permian. These are given below. (For explanation of numbers, see p. 48.) XVI K 15: Chonetes aff. C. variolatus. Rhynchopora cf. R. nikitini. Aviculipecten? sp. XVII f 42: Polypora sp. Chonetes sp. Productus cf. P. aagardi. Productus n. sp. Rhynchopora cf. R. nikitini. XVII n 34: Chonetes cf. C. ostiolatus. Rhynchopora cf. R. nikitini. This lower Permian horizon is correlated paleontologically by Girty with the Artinskian of Tschernyschew and is known at many localities in Alaska. In northern Alaska this horizon has been recognized by Maddren along the international boundary in the valley of the Firth River, not far from the Arctic. Farther west in Arctic Alaska rocks of the same horizon in the Canning River region have been described by Leffingwell 75 under the name Sadlerochit sandstone. This formation, which consists there of 300 feet of sandstone, was described by Leffingwell as Pennsylvanian but is now placed by Girty in the lower Permian. Maddren" found this lower Permian horizon represented by a calcareous tuff lying at the top of a lava 74 Maddren, A. G., unpublished notes. Leffingwell, E. de K., The Canning River region, northern Alaska: U. S. Geol. Survey Prof. Paper 109, pp. 113-115, 1919. formation in the lower Kuskokwim Valley of southwestern Alaska, and Brown" found it represented by a limestone formation in the upper Kuskokwim Valley southwest of Lake Minchumina. In the Alaska Range region Permian rocks are extensively developed. Rocks 6,000 to 7,000 feet thick in the headwater region of the Chistochina River were described by Mendenhall 78 under the name Mankomen formation. This formation consists of limestone, sandstone, and shale. Farther south, in southern Alaska, Artinskian fossils have been found by Capps " in a limestone on Skolai Creek, at the head of the White River, and it is possible that the Permian rocks continue on around the northeast side of the Wrangell Mountains to join with the Mankomen formation farther northwest. In southeastern Alaska Permian rocks were found first on Kuiu Island and are now known to be extensively developed on Kupreanof, Admiralty, and Suemez Islands, as well as at other localities. TRIASSIC SYSTEM UPPER TRIASSIC SERIES DISTRIBUTION In the Yukon Valley, as practically everywhere else in Alaska, the only part of the Triassic system present is the Upper Triassic, and in the Eagle-Circle district Upper Triassic rocks are known only at two localities. At the Nation River Upper Triassic rocks adjoin the Permian limestone on the northwest. In the valley of Trout Creek, about 12 miles farther up the Yukon, the Upper Triassic rocks lie southeast of the Permian limestone. LITHOLOGY At the Nation River locality Upper Triassic rocks crop out on both sides of the Yukon, but are somewhat better exposed, particularly at low stages of the river, on the southwest bank. A tape traverse from the farthest point downstream where such rocks are exposed upstream to the Permian limestone showed the following section. The distances given are horizontal distances along the river beach, but the general structure and thickness are shown graphically in Figure 6. "Brown, J. S., The Nixon Fork country: U. S. Geol. Survey Bull. 783, pp. 105-106, 1926. 78 Mendenhall, W. C., Geology of the central Copper River region, Alaska: U. S. Geol. Survey Prof. Paper 41, pp. 40-51, 1905. Capps, S. R., Mineral resources of the Nabesna-White River district, Alaska: U. S. Geol. Survey Bull. 417, pp. 18-24, 1910. Section of Upper Triassic rocks on Yukon River at the mouth of Nation River Fossiliferous black shale. Strike is N. 70° E. Dip is 70° S. Shaly limestone or calcareous shale. Fossiliferous. Collec- Shale and a 5-foot bed of highly fossiliferous limestone, from Gray fossiliferous thin-bedded limestone. Strike N. 45° E., Feet 150 720 40 18 12 567 17 100 This section, imperfect as it is, shows that these Upper Triassic rocks consist essentially of black bituminous shale, interstratified with thin beds of gray to black limestone. Much of the black shale exposed at this locality is oil shale, but none of these rocks were tested quantitatively for oil. The oil shale at Trout Creek was noted by P. J. Hillard, of Eagle, as early as 1901, and in October, 1915, he sent a sample to the United States Geological Survey. No distillation test of the shale was made at that time, however, the specimen being apparently of more interest on account of its contained fossils than on account of its bituminous nature. The shale from Trout Creek consists of a mat of closely compressed shells of Pseudomonotis and Halobia in a matrix of black shale. The fossil shells are so numerous and so closely compressed that not even the thinnest sliver of shale can be discovered without the impression of a shell upon it. A recent microscopic examination by Miss Taisia Stadnichenko, of the United States Geological Survey, indicates that the bituminous material originated from spores. A sample of this oil shale collected by the writer in 1925 was distilled in the chemical laboratory of the Geological Survey by E. T. Erickson, whose report is given below: The sample as received appeared to have been exposed to weathering, which is likely to influence the character as well as the yield of the oil. For further chemical test the shale deposit should be resampled at a position unaffected by weathering. |