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Authors: Holmer, Lars E. , Blodgett, Robert B. , Liang, Yue , Zhang, Zhifei
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Date: /2020
Title: The Early Devonian (Emsian) acrotretid microbrachiopod Opsiconidion minor Popov, 1981, from the Alaska/Yukon Territory border and Novaya Zemlya
69 , 3 , 143-153,
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Document Type: Article\Abst.\Chapter\report
Annotation: Abstract. New records of the poorly known acrotretid (Biernatidae) microbrachiopod Opsiconidion minor Popov are described from middle Emsian strata of the Ogilvie Formation in east­-central Alaska and the adjacent Yukon Territory, Canada, and compared with new better ­preserved topotypes from the late Early Devonian (Emsian) of Novaya Zemlya, Russia. In Alaska O. minor occurs together with fragmentary material of Lingulipora sp. and an indeterminate discinid. The only other previous record of O. minor, outside the type area, comes from the Early to ?Middle Devonian (Pragian to ?Givetian) of Australia (Victoria and NSW). Opsiconidion Ludvigsen is a stratigraphically extremely long­-ranging and cosmopolitan acrotretid, which exhibits a remarkable conservatism; the morphology of the ventral valve remains essentially unchanged from the earliest Ordovician (Darriwilian) records to the Devonian.
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none given #11 (University of Alaska Museum loc. A-941) , Section D, Yukon Territory, Long. 140°59'56" W., Lat. 65'05.2' N. Sectlon measured in a small cliff composed of thinly bedded dark gray, fetid, micrite. Cliff located on the south side of Harrington Creek, approximately .05 mile east of the Alaska-Yukon boundary, at point where creek makes a sharp bend to the north upstream. Total height of section is 14 feet. ............. UA Mus. loc. A-941, basal 4 feet of Section D. (description from Blodgett, 1978, M.S. thesis; [Holmer et al., 2020 p. 144 provides the following description: The University of Alaska (UA) Museum locality A941 (Fig. 1) is from the base of Section D of Blodgett (1978). The section is situated in the Yukon Territory (latitude 65º05.2´N, longitude 140º59.56´W) and was measured in a small cliff composed of thinly bedded dark grey, petroliferous, micritic limestone. The cliff is located on the south side of Hard Luck Creek (also known as Harrington Creek), in its upper reaches approximately 0.805 km (0.5 mile) east of the Alaska–Yukon boundary, at the point where the creek makes a sharp bend to the north upstream. The total height of the section is 4.3 m (14 feet). The UA Museum locality A­941 represents the basal 1.22 m (4 feet) of section D. Conodonts from this locality include the age­ diagnostic Polygnathus inversus Klapper & Johnson of middle Emsian age (Blodgett 1978).
Opsiconidion minor Popov, 1981
83RB48 (11920-SD) , Charley River , Micritic to encrinoidal limestone from talus rubble crop from smaller of two prominent talus rubble slides on the south flank of Jones Ridge, elevation about 3,000 ft., NW 1/24 SW 1/4 sec. 10, T. 3 N., R. 33 E. 6.4 kg of rock was process (5 g of +20 mesh insoluble residue). (description of Orndorff and Harris, 1988, E&R report); [Holmer et al., 202, p.148 provide the following description: "A second nearby locality in the Ogilvie Formation is situated in the Charley River A­1 1:63 360 scale quad ­ rangle (latitude 65º06.2´N, longitude 141º01.1´W) in east­central Alaska (Fig. 1). This locality 83RB48 (USGS locality 11920-­SD) consists of micritic to encrinoidal limestone from talus rubble slides on the south flank of Jones Ridge, elevation about 3000 feet (914.4 m), NW1/4, SW1/4 section 10, T. 3 N., R. 33 E. This locality is located approximately 1.29 km (0.8 mile) N10ºW of the first locality. Conodonts from this locality, identified by Audrey L. Orndorff and Anita G. Harris (written commun., 7 October 1988), contain two identifiable polygnathid species, Polygnathus inversus Klapper & Johnson and Polygnathus laticostatus Klapper & Johnson, indicating an Inversus/Laticostatus Zone (middle Emsian) age.]
Opsiconidion minor Popov, 1981
Lingulipora? sp.