NO. 7 SILICIFIED ORDOVICIAN BRACHIOPODS ROSS AND DUTRO 3 



by J. B. Mertie, Jr. (1932, pp. 401-415), who collected fossils from 

 about the same places. 



The brachiopods here described are included in USGS collection 

 D1072-CO : altitude approximately 2,000 feet, located 2,000 feet east 

 and 2,000 feet north of SW cor., sec. 9, T. 3 N., R. 33 E., Charley 

 River (A-l) quadrangle, Alaska; from a thin cherty bed approxi- 

 mately 250 feet above the base of Ordovician limestone, south end of 

 Jones Ridge. 



Paleozoic strata in Jones Ridge are nearly vertical, dipping south- 

 eastward. Thin- to thick-bedded limestones along Hard Luck Creek 

 range in age from Cambrian on the northwest to Devonian on the 

 southeast. Overlying the limestones are highly contorted Devonian 

 black argillites and cherts which form much of the valley between 

 Jones Ridge on the north and Squaw Mountain 3 miles to the south. 

 Structural complications in this broad area remain to be worked out as 

 a part of Brabb's mapping program. 



The Jones Ridge locality is significant because essentially correla- 

 tive Ordovician strata along the Tatonduk River, 7 miles to the south- 

 west (sec. 10, T. 2 N., R. 32 E.), are black graptolitic shales, an 

 entirely different facies. The Tatonduk River region seems to straddle 

 the boundary between miogeosynclinal and eugeosynclinal deposition 

 during the early Paleozoic (Ross, 1961, p. 335) . 



This collection of Ordovician silicified brachiopods and corals 

 closely resembles an assemblage from Perce at the eastern end of the 

 Gaspe Peninsula in eastern Canada (Schuchert and Cooper, 1930; 

 Cooper and Kindle, 1936). The assemblage also includes genera and 

 species found previously in the Caradoc of the Girvan District of 

 Scotland (Williams, 1962). Strangely, the nearby Ordovician rocks 

 of Anticosti Island in the Gulf of St. Lawrence, supposedly of the 

 same age, have little in common with those from Perce. 



The fossil assemblage is limited because of logistic problems in- 

 volved in getting large samples out of the area by helicopter. Several 

 species are represented only by immature specimens and others by 

 single specimens. At least 9 species cannot be identified because of 

 inadequate material and 6 of these cannot be assigned to genera with 

 certainty. 



CORRELATION 



Correlation of this small assemblage is difficult and must be con- 

 sidered preliminary. It shares a problem common to the Ordovician 

 in many parts of western North America. The assemblage includes, 

 from a limited stratigraphic interval, genera and species which are 



