Fossils From the Ordovician Bioherm at Meiklejohn Peak, Nevada PDF
Preview Fossils From the Ordovician Bioherm at Meiklejohn Peak, Nevada
Fossils From the Ordovician Bioherm at Meiklejohn Peak, Nevada GEOLOGICAL SURVEY PROFESSIONAL PAPER 685 Fossils From the Ordovician Bioherm at Meiklejohn Peak, Nevada By REUBEN JAMES ROSS, JR. GEOLOGICAL SURVEY PROFESSIONAL PAPER 685 Distribution off ossils in the bio her m and in flanking beds is documented. Species of 12 genera of brachiopods and 2O genera of trilobites are described. They compare closely with contemporary forms in Quebec and western Newfoundland UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1972 UNITED STATES DEPARTMENT OF THE INTERIOR ROGERS G. B. MORTON, Secretary GEOLOGICAL SURVEY V. E. McKelvey, Director Library of Congress catalog-card No. 78-188321 For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20402 - Price $1.25 (paper cover) Stock Number 2401-2048 CONTENTS Page Page Abstract.._ __________________________________ 1 Phylum Arthropoda_______________ 28 Introduction. ________________________________ 1 Class Trilobita_______---__---_ 28 Previous work____________________________ 1 Genus Trinodus___________ 28 Acknowledgments ____.___--__-_____.______ 2 Genus Shumardia-_________ 29 Stratigraphic setting._________________________ 2 Genus Carrickia,__________ 29 Petrology of bioherm, preliminary statement. 6 Genus Carolinites-_________ 29 Fossil collections.--_________.---_---__________ 8 Genus Glaphurus__________ 30 Collections from flanking beds__________________ 12 Genus Nileus-_____________ 31 Stratigraphic anomalies ________________________ 15 Genus Peraspis-___.---___- 31 Summary of fossil distribution______ ____________ 16 Genus Illaenus____________ 32 Descriptions of fossils.________________________ 17 Genus Harpillaenus- _______ 34 Phylum Brachiopoda_.__-__-----_______-__ 17 Genus Bathyurellus- _______ 34 Class Articulata._____________________ 17 Genus Rayrnondites?________ 35 Genus Orithidiuni-________________ 17 Genus Selenoharpes- _______ 36 Genus Trematorthis_______________ 20 Genus Endymionia.________ 37 Genus Pleurorthis---___-__.____-__ 20 Genus Lehua.-____________ 37 Genus Cyrtonotellct-_.__-_.________ 21 Genus Pliomerops_ _______ 37 Genus Phragmorthis-______________ 22 Genus Kawina-___________ 38 Genus Camerella.-________________ 22 Genus Xystocrania--------- 39 Genus Idiostrophia________________ 23 Genus Heliomera----------- 39 Genus Ingria-__.__-_-______.___-_ 26 Genus Miracybele-_________ 40 Genus Isophragma._______________ 27 Genus Apatolichas.________ 41 Genus Petroria-__________________ 27 Pygidia of uncertain affinity. 41 Genus Paucicostella-______________ 28 References cited___________-_--_---___- 42 Genus Cuparius._________________ 28 Index_ __________________----------__- 45 ILLUSTRATIONS [Plates 1-18 follow index] PLATE 1. Orthidium, Orthidium?, Trematorthis, and Pleurorthis. 2. Pleurorthis?, Cyrtonotella?, and Phragmorthis. 3. Camerella. 4. Camerella and Idiostrophia. 5. Idiostrophia. 6. Idiostrophia. 7. Idiostrophia. 8. Idiostrophia. 9. Idiostrophia and Ingria. 10. Ingria, Ingria?, Leptellina? or Taphrodonta?, Isophragma?, and Carrickia. 11. Petroria?, Cuparius, Shumardia, Carolinites, and Trinodus. 12. Carolinites, Glaphurus, Nileus, Peraspis?, and Illaenus. 13. Illaenus. 14. Illaenus and Illaenus?. 15. Harpillaenus and Bathyurellus. 16. Raymonditesl, Selenoharpes, Endymionia, proetid, Lehua, and Pliomerops. 17. Kawina, Xystocrania, Heliomera, and Miracybele. 18. Apatolichas, undetermined pygidia, Eopteria, undetermined edrioasteroid and Idiostrophia. in IV CONTENTS Page FIGURE 1. Index map showing relative locations of bioherms at Meiklejohn Peak and Aysees Peak, Nev_______________________________________________ 2 2 -6. Photographs: 2. Meiklejohn Peak showing the Eureka Quartzite and large bioherm_ 3 3. Scarp face of the main mass of the great bioherm below Meiklejohn Peak___________------------_-_-----------_______________ 3 4. Exposed northwest end of bioherm_____.._____________________ 4 5. Showing sparry calcite encrustations of fossil skeletons and filling of chambers of cephalopods-__-__-_---------_______________ 5 6. Showing thin laminae of fine lime wackestone separated by sparry calcite __________________________________________________ 5 7. Photomicrographs of thin sections of wackestone and laminoid fenestrae__ 7 8. Photomicrographs of fossiliferous pocket in massive part of bioherm_____ 8 9. Photomicrographs of well-stratified limestone flanking bioherm sections cut nearly parallel and perpendicular to layering.___________________ 9 10. Diagram showing relative positions of fossil collections from bioherm and flanking beds of Meiklejohn Peak_ ________________________________ 10 11. Chart showing ranges of genera of trilobites and brachiopods in flanking beds, in bioherm, and in both_____________________________________ 19 12. Diagram showing length of shell of Idiostrophia valdari Ross, n. sp. versus apical angle, contoured according to number of specimens___ _________ 25 13. Diagram showing length of shell of Idiostrophia valdari Ross, n. sp. versus number of costae, contoured according to number of specimens______ 25 FOSSILS FROM THE ORDOVICIAN BIOHERM AT MEIKLEJOHN PEAK, NEVADA By REUBEN JAMES Ross, JR. ABSTRACT the thin-bedded silty limestone that flanks it. Al A great limestone bioherm, 270 feet thick, lies within the though our knowledge of the fauna is far from com thin-bedded silty limestone of the lower member of the Ante plete, the trilobites and brachiopods obviously are lope Valley Limestone (Pogonip Group) at Meiklejohn Peak, very similar to those from Table Head and Lower Nev. Fossils from the flanking beds show that the bioherm lies mostly within the Orthidiella zone, but the base of the Head, western Newfoundland (Whittington, 1963, bioherm may rest as low as the Pseudocybele nasuta zone of 1965; Cooper, 1965, p. 11-12), as well as to brachiopods the upper Canadian. Fossils from both the bioherm and the listed from boulders in the Mystic Conglomerate and flanking beds include trilobites, brachiopods, cephalopods, con- Levis Shale of Quebec (Cooper, 1956, p. 15, 31; Ross odonts, gastropods, and a few pelecypods, ostracodes, bryozoans, and Ingham, 1970, p. 400). and algae. However, the greatest volume of fossil debris is derived from the pelmatozoans. PREVIOUS WORK Fossils from within the bioherm resemble those from similar limestone bodies in lower Middle Ordovician formations in During the stratigraphic work in southern Nevada Quebec and western Newfoundland. All shelly fossils in the in 1960, three small biohermal masses were discovered bioherm are encrusted with sparry calcite, which may be on the Nevada Test Site and adjacent Bombing and algal in origin. Gunnery Range in the lower part of the Antelope Valley The 12 genera of brachiopods and 20 genera of trilobites of Limestone. Subsequently, a similar but much larger which species are described constitute only a part of the total fossile assemblage. They include Cyrtonotella, PhragmortMs, bioherm was called to my attention by Cornwall in the Raymondiiesl, and Plwmerops all genera that are expected Bare Mountain quadrangle, and both these occurrences in Chazy or younger strata. Petroria is described for the first were reported shortly thereafter (Ross and Cornwall, time south of the United States-Canadian border. It is sug 1961; Ross, 1964, p. C25-C26, pi. 1; Ross, 1967, pi. 11). gested that Paitcicostella of Quebec and Newfoundland is a synonym of Ingria of Nevada. Unfortunately, the bioherms on the gunnery range in the vicinity of Aysees Peak, east of Frenchman Flat, have INTRODUCTION not been comfortably accessible in recent years; but, repeated short visits have been made to the reef at This report deals with the fossils found from 1960 Meiklejohn Peak in the Bare Mountain quadrangle through 1969 in the great early Middle Ordovician (% 1). bioherm at Meiklejohn Peak, Nev., and in the silty In 1966, R. H. Flower assisted in the work at the flanking limestone. The bioherm is exposed on the Meiklejohn Peak bioherm and collected a considerable southwest side of Meiklejohn Peak in the SW^NE^ number of cephalopods. sec. 21, T. 12 S., R. 47 E., Bare Mountain 15-minute Several of the trilobites reported by Holliday (1942, quadrangle, Nevada (Ross, 1964, p. C25-C26). The base p. 472) wrere obtained from the silty limestones that of this biohermal structure rests on silty limestones flank the bioherm at Meiklejohn Peak. These were iden that are gradational from the Ninemile Formation into tified by Holliday as Ectenonotus connemaricus the lower member of the Antelope Valley Limestone. (Reed), Ectenonotus marginatus n. sp.; Parapilekia These beds include brachiopods and trilobites of the beattyana n. sp., Pseudomera sp., and Niobe? feitleri Pseudocyl>ele nasuta zone. Beds that lie above the bio n. sp. herm and flank its higher sides carry brachiopods of The Bare Mountain quadrangle was mapped geo the Orthidiella zone. logically by Cornwall and Kleinhampl (1960, 1961). A considerably diverse fossil assemblage has been Their map indicates the presence of a fault that cuts taken from the limestone of the bioherm as well as from across the Ordovician section on the southwest side of FOSSILS FROM THE ORDOVICIAN BIOHERM AT MEIKLEJOHN PEAK, NEVADA each of whom I am indebted for important comments and corrections. John L. Wray, Dr. Jaanusson, and Richard Rezak were particularly helpful in advising me on interpretation of carbonate petrology of the bioherm. During my visit to Sweden in 1968, Dr. Valdar Jaanusson called attention to Idiostrophia in the Asa- phus shale in the district of Toyen, where it had been called RhynchoneUa digitata by Brogger. Dr. Gunnar Henningsm0en of the Paleontological Museum in Oslo kindly permitted me to illustrate and describe Brog- ger's specimen for comparison with the myriad speci mens of Idiostrophia found in the Meiklejohn bioherm. Dr. Jaanusson also showed me the somewhat younger but very similar Ordovician bioherms near Lake Sil- jan, Dalarna, in Sweden. Part of grant GA-4020 from the National Science Foundation made possible the visit to areas of Swedish Ordovician exposure under the guidance of Dr. Jaanusson. Through the efforts of colleagues, a more complete coverage of fossils in and around the bioherm has been possible. Ellis Yochelson identified the gastropods, Jean Berclan the ostracodes, Olgarts Karklins the bry- ozoans, and John Huddle the conodonts. A. J. Rowell of the University of Kansas has made a brief examina FIGURE 1. Index map showing relative locations of bio- tion of inarticulate brachiopods with unusual results. herms at Meiklejohn Peak (M) and Aysees Peak (A), Parablastoids were identified by James Sprinkle. John Nev. Pojeta, Jr., identified the pelecypods and Rousseau H. Flower the cephalopods. Meiklejohn Peak. This fault passes west of the main mass of the bioherm, cutting its coarsely calcarenitic STRATIGRAPHIC SETTING apron (figs. 3, 10). Although two small bioherms were found east of The biohermal limestone at Meiklejohn Peak (fig. Frenchman Flat in 1960, their regional importance 2) has been recorded as 163 feet thick and 68 feet above was not fully appreciated; their stratigraphic position the base of the Antelope Valley Limestone (Ross, is in the Ranger Mountains Member (Byers and others, 1964, p. C26). The original measurement of the section 1961, p. C108). The bioherm at Meiklejohn Peak is in was taken across the bioherm on its thinned north the same stratigraphic position but a more generalized side. It is actually about 270 feet thick in its thickest stratigraphic terminology has been used and the reef part (figs. 3, 4). About 20 collections of fossils have is considered to be high in the lower member of the been made subsequently to those previously published Antelope Valley Limestone. by Ross (1964, p. C27-C28). Positions of these col lections are shown diagrammatically in figure 10. The ACKNOWLEDGMENTS constituent fossils of each collection are listed below. H. R. Cornwall and F. G. Kleinhampl first called my The bioherm is about 1,000 feet wide along the face attention to the bioherm at Meiklejohn Peak in 1960. of outcrop. Its other lateral dimension is not known. Since then several paleontologists have visited this The main mass is devoid of clearly defined bedding. feature with me and have contributed much counsel Locally, the limestone is a coarse bioclastic calcarenite and assistance; they include A. R. Palmer in 1960- composed of a wealth of megafossils brachiopods, 61; G. A. Cooper, J. T. Dutro, Jr., R, S. Boardman, trilobites, and gastropods, among others. Shells and B. S. Nbrford, F. C. Shaw, and H. B. Whittington in carapaces are encrusted with thin calcitic deposits of 1965; R. H. Flower in 1966 and N. F. Sohl in 1969. a sparry nature. This sparry calcite seems to be the The manuscript was read critically by Dr. Valdar binder in the bioherm (fig. 5). It is seen to separate Jaanusson, William T. Dean, and Michael Taylor, to thin laminae of finer grained limestone (fig. 6) in STRATIGRAPHIC SETTING FIGURE 2. Meiklejohn Peak, as seen from the west-northwest at a distance of about 2 miles. The peak is composed of light- colored Eureka Quartzite. The larger bioherm is in the lower slopes to the right. FIGURE 3. Scarp face of the main mass of the great bioherm below Meiklejohn Peak, as seen from hill 4966 on the west side of Secret Pass (sec. 24, T. 12 S., 47 E., Bare Mountain quadrangle, Nevada). Bioherm is 270 feet thick; exposed lateral dimension approximates 1,000 feet. View looking northeast. Approximate position of fault indicated by dotted line. are ned ng. cave Thinsheari to left of small overlap its top. postdepositional Standing mass and cured by ne. al obs diella zobiohermbeds is rthiof ng Ok ki e anan thflfl of nst nd pods agairm a hioutt ohe acbbi brd n r unee aow eds beforegrct bet ying bn left Conta erls ier. Thin ovhin bedof cent oherm. cled). Ter right nd of biwer (cirath view eoe west H. Fls ben rthR. sse nod pa Exposed Wilson anmal mass 4.A. her RE L. bio U G FI STRATIGRAPHIC SETTING FIGURE 5. Sparry calcite encrusts all kinds of fossil skeletons and fills chamber of cephalopods. Butt end of %-inch chisel lies above sectioned nautiloid. FIGURE 6. Thin laminae of fine lime wackestone separated by sparry calcite (laminoid fenestrae). This lithology is of great ex tent on northwest side in lower part of bioherm. 446-051 O - 72 - 2
Description:The list of books you might like
