Fossils From the Ordovician Bioherm at Meiklejohn Peak, Nevada

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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
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Exposed Wilson anmal mass
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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