Distribution of the Middle Ordovician Copenhagen Formation and its Trilobites in Nevada GEOLOGICAL SURVEY PROFESSIONAL PAPER 749 Distribution of the Middle Ordovician Copenhagen Formation and its Trilobites in Nevada By REUBEN JAMES ROSS, JR., and FREDERICK C. SHAW GEOLOGICAL SURVEY PROFESSIONAL PAPER 749 Descriptions of Middle Ordovician trilobites belonging to 21 genera contribute to correlations between similar strata in Nevada) California) and 0 klahoma UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON 1972 UNITED STATES DEPARTMENT OF THE INTERIOR ROGERS C. B. lVIOR TON, Secretary GEOLOGICAL SURVEY V. E. McKelvey, Director Library of Congress catalog-card No. 78-190301 For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20402 - Price 70 cents (paper cover) Stock Number 2401-2109 CONTENTS Page Page Abstract ______________________________ -------------------------------------------------- 1 Descriptions of trilobites __________________________________________________ _ 14 Introduction ________________________________________________________________________ _ 1 Genus T1·iarth1·us Green, 1832 .... ------------------------------ 14 Previous investigations _____________________________________________ _ 1 Genus Carrickia Tripp, 1965 ____________________________________ _ 14 Acknowledgments-------------------------------------------------------· 1 Genus Hypodicranotus Whittington, 1952 _____________ _ 15 Geographic occurrences of the Copenhagen Genus Robergia Wiman, 1905·---------------------------------- 15 Formation and its equivalents _____________________________ _ 3 Genus Remoplewrides Portlock, 1843 ______________________ _ 17 Stratigraphie sections _______________________________________________________ _ 3 Genus Robergiella Whittington, 1959 .... -----------------­ 17 Antelope Valley, N ev ________________________________________________ _ 3 Genus Isotelus Dekay, 1824·-------------------------------------­ 18 Fossils from hill 8308·---------------------------------------- 3 Genus Anataphrus Whittington, 1954.-------------------- 19 Fossils from east side Martin Ridge _______________ , 5 Genus Nileus Dalman, 1827 _____________________________________ _ 21 Clear Creek Canyon, Nev _________________________________________ _ 6 Illaenid genus, indeterminate __________________________________ _ 21 Correlation of fossils at Clear Creek Canyon __ 7 Genus Toemquistia Reed, 1896.. ------------------------------· 22 Harpid genus, indeterminate ___________________________________ _ Hot Creek Canyon, N ev ____________________________________________ _ 7 22 Genus C1·yptolithoides Whittington, 1941 ______________ _ 22 Rawhide Mountain, N ev ____________________________________________ , 8 25 Belted Peak area, Nevada ________________________________________ _ 8 Genus Lonchodomas Angelin, 1854-------------------------­ 25 Meiklejohn Peak, N ev _____________________ --------------------------- 9 Genus Ampyxina Ulrich, 1922---------------------------------­ Genus Raynwndella Reed, 1935.------------------------------­ 25 Northern Inyo Mountains, Calif _____________________________ _ 9 Toquima Range, Nev _________________________________________________ _ Genus Ceraurinella Cooper, 1953 .. --------------------------- 26 9 Genus Ceraurus Green, 1832 ____________________________________ _ 26 Independence Mountains, N ev _________________________________ _ 9 Cheirurinid genus, indeterminate ___________________________ _ 27 Age of trilobite faunas of the Copenhagen Genus Sphaerocoryphe Angelin, 1854 ____________________ _ 27 Formation and its equivalents _____________________________ _ 10 Genus Cybeloides Slocum, 1913.------------------------------- 27 Member A of Merriam ( 1963) --------------------------------­ 10 Calymenid genus, indeterminate _____________________________ _ 27 Member B of Merriam (1963) ---------------------------------· 10 Genus Calyptaulax G. A. Cooper, 1930 __________________ _ 27 Member C of Merriam (1963) ---------------------------------- 10 Genus A'mphilichas Raymond, 1905 ________________________ _ 28 Caesar Canyon Limestone ________________________________________ _ 10 Genus Miraspis R. and E. Richter, 1917 ________________ _ 28 Age of the Copenhagen Formation and its Genus Primaspis R. and E. Richter, 1917--------------· 29 equivalents _______________________________________________________________ _ 11 References cited _________________________________________________________________ __ 29 Collections and localities ___________________________________________________ _ 12 Index·------------------------------------------------------------------------------------- 31 ILLUSTRATIONS [Plates follow index] PLATE 1. Tr·iarthnts, Carrickia?, Hypodicranotus, Robergia, and Remo]Jleurides. 2. Robergiella and Isotelus. 3. Isotelus and Anataphrus. 4. Nileus?, illaenid, Toernquistia?, harpid, and Cryptolithoides. 5. Cryptolithoides. 6. Lonchodomas, Arnpyxina, Raymondella, Ceraurinella, cheirurinid, Ceraurus?, and Cybeloides. 7. Sphaerocoryphe, calymenid, Calyptaulax, Amphilichas, and Mi1·aspis. 8. Primaspis, Thaleops, and Enc1·inuroides. Page FIGURE 1. Index map showing location of stratigraphic sections in which the Copenhagen Formation or its equivalents have been recognized in Nevada and California___________________________________________________________________ 2 2. Outline sketches of cranidium and pygidium of Isotelus copenhagenensis.------------------------------------------------------------ 19 3. Line tracings of cryptolithid genera and species from North America·------------------------------------------------------------------ 23 TABLE Page TABLE 1. Characteristics of isoteloid genera, based on type species .. ---------------------------------------------------------------------------------------- 18 III DISTRIBUTION OF THE MIDDLE ORDOVICIAN COPENHAGEN FORMATION AND ITS TRILOBITES IN NEVADA By REUBEN JAMES Ross, JR., and FREDERICK C. SHAW ABSTRACT PREVIOUS INVESTIGATIONS The Copenhagen Formation of central Nevada is composed of a basal sandstone (member A) and two calcareous siltstone The name Copenhagen Formation was first used and silty limestone members (members B and C). by Nolan, Merriam, and Williams (1956, p. 28) with­ In areas north and south of Antelope Valley, member B of out definition. Kirk (1933, p. 32-33) was the first to the formation is recognized, but the overlying member C is recognize the stratigraphic significance of beds later not recognized. To the east and southeast the supposedly older uppermost beds of the Antelope Valley Limestone are actually assigned to the formation and the first to imply that equivalent to the lower beds of member B. To the west in two these strata were the lateral equivalents of the Eu­ thrust sequences of the Toquima Range, the Caesar Canyon reka Quartzite. Cooper (1956, p. 127-128, chart 1) Limestone of Kay and Crawford and an unnamed limestone recognized strata of the formation and was probably are probably equivalent to the uppermost Copenhagen Forma­ responsible for calling attention to its members, the tion. Species of 21 genera of trilobites are described from mem­ upper two of which he believed were separated by a bers B and C. Four additional taxa have not been identified considerable hiatus. Webb (1958, p. 2339-2345) used below familial rank. The most evident change in trilobite the name and discussed the extent and correlation of assemblages takes place about 100 feet below the top of mem­ the Copenhagen Formation; his correlations were ber C in the type locality around Antelope Valley; these basically lithic, with some fossil control. He ques­ highest trilobites suggest correlation with the Viola Limestone tioned the existence of a hiatus within the formation. of Oklahoma. The trilobites from lower in member C indicate a Wilderness-Barneveld age. Ethington and Schumacher (1969, p. 440-443) have given a good review of the definition of the INTRODUCTION Copenhagen Formation, of early interpretations of The Middle Ordovician Copenhagen Formation was the formation, and of the stratigraphic problems the defined by Merriam in 1963 (p. 25-27) for highly unit poses. They discovered that the uppermost beds fossiliferous arenaceous, argillaceous, and calcareous of the underlying Antelope Valley Limestone con­ strata lying above- the Antelope Valley Limestone tained significant elements of the conodont fauna of and below the Eureka Quartzite in central Nevada. members A and B of the Copenhagen. This discovery The formation is best developed on both sides of parallels that of Ross (1964, p. C78; 1970, p. 31) Antelope Valley (in the Monitor Range on the west concerning brachiopods and trilobites and indicates and in the Antelope Range on the east, Horse Heaven that the major unconformity proposed by Cooper Mountain quad.). (1956, chart 1) beneath the basal sandstone of the The formation or its lithologic equivalents can be Copenhagen Formation in its type locality does not recognized over a great distance from the Indepen­ exist. dence Mountains of northern Nevada to the northern Inyo Mountains of southern California (fig. 1). ACKNOWLEDGMENTS It is the purpose of this report to describe the known trilobites of the Copenhagen Formation, to Shaw extends particular thanks to the Faculty summarize the geographic extent of the formation, Grants Committee of Mount Holyoke College, which and to update information on the correlation of the supported his work with Ross in the Eureka area in formation. A few trilobites are described