UNIVERSITY of NEVADA RENO PERMIAN-TRIASSIC SOURCE BED ANALYSIS at QUINN RIVER CROSSING, HUMBOLDT COUNTY, NEVADA a Thesis Submitt
UNIVERSITY OF NEVADA
RENO
PERMIAN-TRIASSIC SOURCE BED ANALYSIS AT QUINN RIVER CROSSING, HUMBOLDT COUNTY, NEVADA
A thesis submitted in partial fulfillment of the
requirements for the degree of Master of Science
in Geology
by
Scott Byron McDaniel III
January 1982 MINES LIBRARY
I ( * 2 .3
© 1982
SCOTT BYRON McDANIEL
All Rights Reserved The thesis of Scott Byron McDaniel is approved:
University of Nevada
Reno
January, 1982 11
ACKNOWLEDGMENTS
The writer wishes to take this opportunity of expressing his appreciation to the many people who have contributed of their time and energy in the furtherance of this investigation. I wish to acknowledge the help ful discussions with N. J. Silberling, R. C. Speed, B. R.
Wardlaw and L. T. Larson. Special appreciation is ex pressed to J. Lintz, Jr. for his continuing advice throughout the project. Advice and assistance in sur veying, mapping and rock sampling were given by T. De
Rocher. Special gratitude is also extended to the Reynosa family and Jim Reid of the Ivory Ranch at Quinn River
Crossing, Nevada.
I wish to thank Sun Exploration Company, Denver,
Colorado, who partially financed this project and also gave me great support. Appreciation is expressed for thin section analyses prepared by Michael Wilson of AGAT
Consultants, Inc., of Denver, Colorado, under contract to
Sun Exploration Company. Ill
ABSTRACT
The Quinn River Crossing area is located in north west Humboldt County, Nevada„ Measured sections are lo cated at the southeast margin of the Pine Forest Range and southwest area of the Bilk Creek Range. The Permian Lime stone and Triassic units in both areas have yielded faunules.
Structural relations in the area suggests a system of imbricate thrust sheets of Permian-Triassic age. The remnants displayed in the ranges are allochthonous blocks which have been post-depositionally transported over many kilometers distance, and subsequently tilted and uplifted by Tertiary Basin and Range tectonic processes.
The age dating, mapping and laboratory analysis of the Quinn River Crossing area have identified a region which is structurally complex. The Pine Forest area ex hibits extensive structural deformation and recrystalliza tion. The Bilk Creek section does not exhibit extensive recrystallization of sediments, and lacks the deformation and metamorphism displayed in the nearby Pine Forest Range and Jackson Mountains. iv
TABLE OF CONTENTS Page
ACKNOWLEDGEMENTS ii
ABSTRACT iii
LIST OF FIGURES, TABLES, AND PLATES vi
CHAPTER
I. INTRODUCTION 1 Purpose 2 Methods and Materials 3 Geographic Setting 5
II. GEOLOGY OF THE SOUTH BILK CREEK RANGE
Stratigraphy 9 Structure 19
III. GEOLOGY OF THE SOUTHEAST PINE FOREST RANGE Stratigraphy 22 Structure 29 IV. CORRELATION
Biostratigraphical Description of the Permian 32 The Bilk Creek Section 35 The Southeastern Pine Forest Range (Permian or Older) Limestone Formation 38 The Black Rock Section 38 The Klamath Mountain Section 39 The Coyote Butte Section 41 Biostratigraphical Description of the Late Middle and Upper Triassic 43 The Quinn River Formation 45 The Southeast Pine Forest (Triassic) Limestone Formation 46
V. LABORATORY ANALYSIS
Introduction 49 Thin Section Analysis: South Bilk Creek Range 53 Southeast Pine Forest Range 55 Total Organic Carbon Analysis 58 Vitrinite Reflectance Analysis 58 Thermal Alteration Analysis 59 Laboratory Analysis Discussion 63 V
VI. SUMMARY AND CONCLUSIONS 70 REFERENCES 72 APPENDIX I 88
APPENDIX II 93
APPENDIX III 99 vi
LIST OF FIGURES, TABLES, AND PLATES Page Figures Figure 1 - Location of Pine Forest and Bilk
Creek Study Areas 6
Figure 2 - Generalized Geologic Map of Pine Forest
Valley, Humboldt County, Nevada 7
Figure 3 - Cross-Section B-B', S„ W„ Bilk Creek
Range, Humboldt County, Nevada 10
Figure 4 - Geologic Map of the South Bilk Creek
Range, Humboldt County, Nevada 11
Figure 5 - Stratigraphic Column of the South Bilk
Creek Range, Near Quinn River Crossing,
Humboldt County, Nevada 12
Figure 6 - Section Traverse, South Bilk Creek
Range, Humboldt County, Nevada 13
Figure 7 - Geologic Map of the Dyke Hot Springs
Area, S. E. Pine Forest Range, Humboldt
County, Nevada, with Traverse P-P' 23
Figure 8 - Stratigraphic Column of the South Pine
Forest Range Near Quinn River Crossing,
Humboldt County, Nevada 24
Figure 9 - Cross-Section P-P', S. E. Pine Forest
Range, Humboldt County, Nevada 25
Figure 10 - Correlation of Permian Units in Western
North America 33 vii
Figure 11 - Correlation of Permian and Triassic Stratigraphic Units in the South Bilk
Creek Range and Southeastern Pine Forest
Range 48
Figure 12 - Rock Sampling Program, South Bilk Creek
Range, Humboldt County, Nevada 50
Figure 13 - Rock Sampling Program and Traverse,
S. E„ Pine Forest Range, Humboldt
County, Nevada 51
Figure 14 - Geothermal Diagenetic Criteria
(After Geochem Laboratories,1980) 60
Tables Table 1 - Summary of Laboratory Analysis Results,
South Bilk Creek Range, Humboldt County,
Nevada 61
Table 2 - Summary of Laboratory Analysis Results, Southeast Pine Forest Range, Humboldt
County, Nevada 62
Plates
Plate A - View of the South Bilk Creek Range
Plate B - View of the Southeast Pine Forest Range
Plate C - Arcestes (Proarcestes) carnenteri Smith
Plate D - Epigondolella primitia Mosher 1
INTRODUCTION
The present topography of Pine Forest Valley and the surrounding mountain ranges developed during the later part of the Tertiary period. In this structurally complex exposure of eugeosynclinal sediments large scale thrusting is exhibited. Previously, the area was very active tec tonically with the major blocks of Permian and Triassic age seen in the surrounding ranges being thrust upon each other. The thrusting was followed by the blocks being broken and tilted from extensive block faulting which con tinued into the Pleistocene epoch. In contrast to the mio- geosyncline to the east, the eugeosyncline area has also undergone regional metamorphism.
The rock units of interest exposed in the Pine
Forest Range and Bilk Creek Range represent Permian and
Triassic ages. They are separated by faults and breccia
zones created during different periods of faulting and
thrusting. The Pine Forest Range rock units strike to the northwest and dip to the southwest whereas the units in
the Bilk Creek Range strike predominately northeast and
dip southeast. The rock units in the Bilk Creek Range
also show strong evidence of drag folding associated with
the thrusting events. These blocks could have been trans
ported from various locales, thus providing one explanation
to their present difference in orientation. The major 2
thrusting of the Triassic over the Permian units took place from early Triassic to late Cretaceous time0 The thrusting events extended over partly correlative rocks of the con tinental shelf along an accretionary belt of indeterminate length„ Originally, the Bilk Creek limestone was shown to be an allocthonous plate (Willden, 1964) . This conclusion has been recently reviewed as correlating strongly with the Mc
Cloud limestone sequence at Shasta Lake, northern California
(Stevens, 1977 and Ketner, 1981), There is now evidence that the Pine Forest Range could also be an allochthonous plate„
Skinner and Wilde (1965) also found that the fauna and lith ology of the limestone near Quinn River Crossing had strong similarities to the McCloud Limestone of the eastern Klamath
Mountains 0
Purpose
The rock units of the Quinn River Crossing area have been mapped previously by R. Willden (Preliminary Geologic
Map of Humboldt County, Nevada, NBMG, 1963), J. G. Smith
(Geology of the Duffer Peak Quadrangle, USGS 1-606, 1973), and Branch Russell (Ph„D. dissertation, Northwestern Univer sity, 1981)o These maps reflect attempts to study in detail the units exposed in this representative eugeosynclinal area of Northwestern Nevada„ The author has also studied the area in detail by field mapping, laboratory analysis of 3
thin sections and literature investigation. The purpose of this thesis is to accurately determine
the ages of the rock units exposed in the southeastern Pine
Forest Range and the southwestern Bilk Creek Range. Tech niques utilized included comparing lithologic descriptions
and micro and macro-fauna analyses derived from present work
and previous literature. Also, the potential for petroleum
source beds was studied by examination of the stratigraphic
and structural control throughout the area. This analysis was supported by an extensive rock sampling program funded
partially by Sun Exploration, Division of Sun Oil Company,
Denver, Colorado.
Method and Materials A total of six weeks was spent at the Quinn River
Crossing locale during May through September, 1981. The Permian limestones and Triassic shales present
are primarily secondarily cemented rocks. Sampling of the
units was difficult at depth. Rock samples collected were
taken mainly from the surface to .5 meter in depth. An
attempt was also made to obtain samples which were the least
disturbed by surface weathering with sledge hammer and cold
chisel. The samples were collected along traverse surveyed by tape and Brunton compass. Horizontal control was plotted
from known USGS section corners and end comers of existing
mining claims. A total of 45 samples were collected in the
study area. From the southeast Pine Forest Range 23 of the 4
samples were obtained and 22 samples were collected at the southwest Bilk Creek Range. Samples were analyzed for source bed, thermal alteration, organic carbon and vitrinite reflec tance parameters. Procedures were based upon Geochem Laboratories' manual,
'Source Rock Evaluation Reference Manual, 1980.' The main purpose of the manual is to present the basic use of geo chemical data in the exploration for oil and gas. Thin-
section and stratigraphic rock color designations were cata
logued according to the Geological Society of America's Rock-
Color Chart, 1970 (Boulder, Colorado). The faunule represented by each section was also corre
lated. Due to the high degree of cementation on rock surfaces,
the majority of specimens were collected in float material
where the weathering process had removed fossiliferous ma
terial. Skinner and Wilde's report on 'Permian Fusulinids
from Northwestern Nevada, in Permian Fusulinid from Pacific
Northwest and Alaska' (Paleontological Contributions of the
University of Kansas, Paper 4) was an invaluable reference in
assigning age dates to the Bilk Creek Section.
Sun Exploration Company, Denver, Colorado was very
helpful in granting the writer permission to use available
laboratory data in this report. All laboratory analyses
data are indexed in the designated section of this text. 5
Geographic Setting The Quinn River Crossing area lies in the Pine Forest
Valley of Northwest Humboldt County, Nevada, and is bounded by the Pine Forest Range to the west, by the Jackson Moun tains to the south, and by the Bilk Creek Range to the east as it appears in Figure 1. The Bilk Creek Range is also referred to as the King's River Range. This high desert basin and range country of northwestern Nevada is charac terized by sparse vegetation and limited surface water.
Summer temperatures range in the high 90's with very little humidity, while winter thermometer readings can be as low o as 30 below zero with strong winds. Annual precipitation in the valley floor is less than six inches, mostly occur ring in the winter months as snow. An annual rate of 38 to
50 cm. (15 to 20 in.) along the mountain crests is reported
(Sinclair, 1920).
Pine Forest Valley has an area of about 1,300 sq. km.
(500 sq. mi.). The valley is about 40 kilometers (25 mi.)
long and 10 kilometers (6 mi.) wide towards the north to approximately 21 kilometers (13 mi.) wide in the south as
shown by Figure 2. Pine Forest Valley is in the Great Basin
section of the Basin and Range physiographic province. The
mountain ranges generally trend north and are commonly 80
to 113 kilometers (50 to 70 mi.) long and 8 to 24 kilometers
(5 to 15 mi.) wide. The crests of the mountain ranges are
2,134 to 3,048 meters (7,000 to 10,000 ft.) above sea level
and range from 915 to 1,525 meters (3,000 to 5,000 ft.) 6
Figure I. Location of Pine Forest and Bilk Creek Study Areas 7
Figure 2 . Generalized Geologic Map of Pine Forest Valley, Humboldt County, Nevada 8
above the valley floors. The Pine Forest Valley differs from a typical valley of the Great Basin since it is not closed and does not con tain an internally closed alluvium-filled basin with a playa
(dry lake) being present. Instead, runoff from the ranges into the valley floor discharges into the Quinn River which in turn flows southwestward to the playas of the Black Rock
Desert where it evaporates a The subsurface hydrologic grad ient of the Pine Forest Valley also drains into the Black
Rock Desert to the southwest where the depth to bedrock ap proaches 3,660 meters (12,000 ft.)j according to recent seismic data obtained by Sun Exploration Company (August,
1981). The ranges have also been shown by recent seismic profiles to be bordered by bajadas consisting of coalescing alluvial fans which merge into the valley floor sediments. 9
GEOLOGY OF THE SOUTH BILK CREEK RANGE
Stratigraphy The Bilk Creek section is approximately 1,579 meters
(5,179 feet) thick. One section was measured in a north- south direction along the crest of the Quinn River locale
and appears as Figure 3 (Section B-B'). A reconnaisance
geologic map appears as Figure 4, the stratigraphic column
as Figure 5, and traverse for measuring section as Figure 6.
The rocks in the section are subdivided into blocks (1),
(2), (3) and (4) as described in the section under struc
ture . Block (1) is identified as Triassic-Jurassic? volcanic
block. It is comprised of an igneous and sedimentary se
quence of rock that includes, in decreasing order of abun dance; (a) detrital sedimentary rocks, (ranging from chert-
arenite and quartz-arenite to graywacke), (b) extrusive
and intrusive basic to ultrabasic igneous rocks (ranging from andesite to basalt), (c) bedded chert, and (d) lime
stone. The bedded chert contains phosphatic pellets and
fillings in the axial canals of radiolaria and spicules.
The cherts range from green to dark gray and often have
noticeable iron staining along fracture planes. At location 0+00 on section B-B', rugosa horn coral
was found. These colonial rugose corals have been previ
ously identified as Fomichevella sp. by C 0 H. Stevens,
1977o The Triassic-Jurassic? volcanic sequence of rocks B 4800 >463 4600 >402
v.. >>rx -4 4 0 0 >341
-4 2 0 0 I2B0
-4 0 0 0 1220
-3800 1159
-3 6 0 0 1098
-3 4 0 0 1037
-3 2 0 0 976
-3 0 0 0 915
- 2 8 0 0 854
N EXPLANATION DESCRIPTION m SYMBOL
Colluvium.May contain Tertiary volcanics Quaternary
Triassic- Jurassic (?) Volcanics, intrusives and graywacke m
Middle Triassic Tuffoceous shale
Chert and dolomite Middle Triassic-Upper Permian
Chert, argillite and graywacke Upper Permian
Cherty limestone M iddle-Low er Permian Vertical Scale = Contact Horizontal Scale n 1/4 1/2 1-0 Thrust fault
Disconformity 2.5 cm = 200meters 1.0 in =660 feet Figure 3. Cross-Section B-B1, S.W. Bilk Creek Range, Humboldt County, Nevodq U8°2cf R.3 2 E. R.3 3 E. 11
EXPLANATION
SYMBOL DESCRIPTION
ASuvtai ton V. " a O O O ° S * * . , t o . . . » ° o a o a * m itj r r f ® ' v - V . Beach deposits ' 0 b r ' : s PJ1M ° e * a o. ° . o a > Colluvium! May contain
Tertiary volcanics
.*■ V >/£ | •'V-'.',';'- V: V* * /
Undetermined S^bx^jJ breccia
Volcanics, intrusives and graywacke
Middle Triassic Tuffaceous shale
Chert and dolomite
Upper Chert, argillite Permian and graywacke
Middle to Cherty limestone #m Q° 1 0 m ° o 9 o Lower Permian *“o Thrust fault: Teeth on upper plate
1-J • - «',• Osconfarmity / » „o* « « . , ■ , .**£>• » O < Contact
* V <7 ,70° Strike and dip of beds * • * o . o . ; s o'o*• • * • • 7 ;° . . • o • u O o o o f ■ ^ 0 • ot „ * o • 9 c Geologic Cross-Section B- .o • <9. *3 •«<»<»"•••• ‘
o o. “ o + ' •> o • 0 1/4 1/2 10 • •.0O°o.o. » • . . . a ° *•*#»*• ° ° * o . ° ‘o. • ° * « ,*,** O 3 • • a O « •, • ’ °
LOWER TO MIDDLE PERMIAN © TRIASSIC ublt ony Nevada County, Humboldt J L r1" r i T r 1— r<$£ L _ F A t ^ T ^ . feet 8 2 3 = n ? l.0 -y - - A - - ~ ~ I I iS: r r ■ 1 ■1-i 1 -r IHLG (METERS) LITHOLOGY I I I I ® <5 I I 0 0 4 1 - H
900 0 9 — —1200 500 0 5 — 1578.91 — 800 0 8 — 0 0 6 - 100— — 400 0 4 — 0 0 3 - "00 “ THICKNESS -1000 0 0 7 0 200 ~Z_ -Lim estone-buff colored (N6toN5), very thin bedded, bedded, thin very (N6toN5), colored estone-buff -Lim (N2 reddish-brown to gray-green arenite-dark and -Chert fine very gray-buff,undivided; light argillite and -Chert ),highly /6 brown(5R2 reddish interval-dark -Brecciated fer and argillaceous brown 7/4).weathered, (IOYR -Dolomite- -Limestone-dark gray (N5 toN7), becoming thinly bedded, bedded, thinly becoming toN7), gray (N5 -Limestone-dark to due 4/1) (5YR brown interval-reddish slide -Brecciated finely very 7), 5toN (N gray medium-medium ■Limestone-light bed thin 2/1), 5VR to (N2 black to gray limestone- -Silicified -Limestone-medium to dark gray (N 5toN 7), massive bedded, bedded, massive 7), 5toN (N gray dark to -Limestone-medium hut Fault Thrust Shale-Light to very dark gray (N2 to N7), friable to very very to friable N7), to gray (N2 dark very to Shale-Light utray alluvium Quaternary Disconformity ocnc rocks Volcanic thick bedding with interbedded calcareous siltstone, siltstone, calcareous interbedded with bedding thick 25cm undivided,blocky, 3/4)', IOR to Y3/2 5G and rn xd sann aog rcue, ih volcanic with fractures, along staining oxide iron clasts. calcite quartz, with fractures solution along banding, iron cut concentric with grained fragments. chert and staining oxide iron with silicified vdn 541 o5B5/l). 5 B 5 to (564/1 evident and copper Abundant units. shale and sandstone, (Co- fixota Ctenalosia brachiopod containing ruginous Silberling,l95€j fragments,NJ throughout.(pelecypod aceous lized to strongly recrystallized. Iron oxide staining staining oxide Iron recrystallized. strongly to lized material (arenite) and elastics (graywacke) (graywacke) elastics and (arenite) material Jones,1978). L (D radiolaria Permian Late with sand-mud interbedded orange trace Slight staining.iron n cet iln wt I-0mdr boncet bands. chert brown dark IO-20cm with filling chert and chert beddedsiliceous gray dark with oper,1957) 1979) Silberling, molds(N.J. ammonite containing stone abundant with grained fine very beds, chert with ded oc fissile, Rarely interface. iron bedding phyllitic on dendritic, patterns occasional thick, m m 5 bedding 2 to 3 hematite)shale as banding extensive and with staining thick), iron 25mm to m brown bands(!3m reddish to chert gray dark interbedded with hard oua cet cainl apr adn wt hr Iron chert with and banding jasper banded with occasional interval, chert) nodular brecciated of top at tures, fracturing extensive with grained fine very silty, uff" T throughout; folding of Evidence teds. of ation lc cet rget 6t 2m diameter. 12mm to 6 fragments chert black Hindeodussp of top.Conodonts near parafusulinids omnals, limonite. and hematite as fractures along filling oxide frac along fillings calcite numerous with crystalline; iron oxide (limonite, hematite) staining. Abundant Abundant staining. hematite) (limonite, oxide iron col- crinoid coral, horn rugose brachiopods, 25cm to diameter crystals calcite rhombohedral of Evidence color brown reddish light-medium to buff casional etclr l ol cet ad fo 530" 5 4 "5 0 3 5 from bands chert ) m c l8 to (l3 lenticular to brown diameter, with 3 25mm to fragments calcite dark calcite filling with light to dark gray zone of of zone gray dark to light with filling calcite to light dark by chacterized fracturing extensive with with numerous calcite stringers along fractures, fractures, along calcareous, stringers % 0 calcite 7 numerous to 0 6 with approximately xtyline, medium meters minor solution cavities. Rugose coral mounds formed formed mounds coral Rugose cavities. solution minor s eaie cainly en ln fatrs and fractures along seen occasionally hematite as unrecrystal- from ranges which gray) dark to light ( oaouuia osa t ae f section. of base at soissa Eoparofusulina t ae f eto, oihvla sp Fomiqhevella section, of base at chert rounded poorly to angular containing often Crinoid columnals and pelecypod fragments at 100 meters. 100 at fragments pelecypod and columnals Crinoid Pseudofusulinella dunbori at 4 5 7 meters. 7 5 4 at Pseudofusulinelladunbori suouuiel psla t 2 meters. 128 at pusilla Pseudofusulinella Schwoaerina ieffordsi at 366 meters. 366 at ieffordsi Schwoaerina DESCRIPTION
H8^2Cf R .3 2 E . ( R .33E. 13 .0^1-0 ■•r.o-.o '
m m EXPLANATION
SYMBOL DESCRIPTION
Alluvial fan
Beach deposits
Colluvium! Moy contain Tertiary volcanics
Oune deposits
Lake deposits
Fault breccia
Volcanics, intrusives and graywacKe
Tuffaceous shale
Chert and dolomite
Chert, argillite and graywack*
Cherty limestone
T h ru st fault'. Teeth on upper plate
Disconformity
Contact
Strike and dip o f beds
Traverse fuming point
0 1/4 1/2 10
Scale! 2.5 cm=200meters 1.0 in = 6 6 0 feet
Figure 6 Section Traverse > South Bilk Creek Range, Humboldt County, Nevada 14 is immediately adjacent to the rugosa coral community found at location 0+00.
None of the rocks in the Permian limestone (Block 2) above this sequence appear to be metamorphosed, as evidenced by the unrecrystallized cherts which contain outlines of radiolarians and spicules. Fossil specimens identified by
Skinner and Wilde (1965-1966), Ketner and Wardlaw (1978-
1981), contain brachiopods, corals and fusulinids. These fossils are only slightly recrystallized, which is indica tive of a nonmetamorphosed limestone terrain.
The lack of metamorphism of these rocks sets them apart from the metamorphosed volcanic and sedimentary se quences of the neighboring Jackson Mountains and Pine
Forest Range. The thickness of the rocks is indeterminate, since neither the base nor top of the sequence is exposed
(being overlain and underlain by thrust faults).
Block (2) is represented by approximately 1,020 meters (3,350 feet) of Permian limestone. An extensive index of fusulinids from this section was published by Skinner and
Wilde in May, 1966. The limestone is characterized by massive bedding with thin bedding occurring near brecciated zones and fault planes. The limestone is commonly medium gray, very fine to medium crystalline, and approximately 60 to 70 percent calcareous. When thin bedded, it is ac companied by dark gray chert bands which contain secondary cementation (Si02) throughout. Abundant calcite is found along both primary and secondary fractures within the lime 15
stone. This secondary cementation occurrence is often accompanied by iron oxide staining as hematite, especially where solution cavities were formed by the weathering pro cess along fractures within the rock. Calcite crystals also fill vugs and solution cavities within the limestone. Occa sionally, clasts of subangular to subrounded light to dark gray chert are evident within the fracture surfaces. The clasts range from non-recrystallized to strongly recrystallized.
At station 555 meters, numerous clasts of calcite crys tals (app„ .3 cm, diameter) were located in situ. This speci men underlies a breccia zone and could possibly represent a facies change within the limestone unit. The sample is des cribed as a gravel conglomerate and reveals evidence of minor surface porosity (less than TL). Although surface expression of porosity is misleading due to the effects of chemical and physical weathering (as well as the lack of confining pressure), the specimen definitely represents a marked change in textural structure (in contrast to the majority of the exposed Permian limestone within Block 2).
A thick sequence of talus breccia material occurs from
557 meters to 680 meters (123 meters = 403 feet thick). The breccia zone contains abundant white calcite fragments from
.3 cm. to 2.5 cm. diameter with black chert fragments from .6 cm, to 1.3 cm. diameter. Both minerals are subangular, suggesting the occurrence of thrusting activity. Iron oxides, both as limonite and hematite staining, coat fracture sur faces and clasts within the breccia zone with a yellow to 16
reddish brown coloration.
The principal bedding units of the Permian limestone
range from only a few centimeters in thickness near thrust
contacts to a massive and blacky two meters in thickness near the base and middle of the sequence. Often the bedding
units are separated by discontinuous lenses of chert nodules
and partly silicified limestone. Fusulinids, horn corals
and crinoid columnals are abundant throughout the Permian
limestone sequence with brachiopods abundant at the top,
(where the limestone increases in silt content). They are described in the correlation section of the text. This as
semblage has been designated as Wolfcampian to Late Leonard- ian in age on the basis of fusulinids (Skinner and Wilde,
1966) and brachiopods (Ketner, 1981). One community of brachiopods, conodonts and crinoid columnals were located within 50 meters of the top of the limestone sequence. The brachiopods are diverse and are often coated with a hematite staining. The conodonts are identified as belonging to the
Hindeodus sp., commonly indicative of shallow water deposi tion (Wardlaw and Collinson, 1979). The thermal alteration index of the conodonts was studied by Epstein et al.,1977, and assigned a value of 3.0 (indicating an unmetamorphosed petrographic aspect to the rocks with a maximum host-rock o o temperature range of 110 to 200 C.). Fusulinid faunas dominate this sequence and have been correlated with the
McCloud Limestone in northern California (Skinner and Wilde,
1965) and the Coyote Butte Limestone of Coyote Butte, Oregon 17
(Cooper, 1957, Ketner and Wardlaw, 1981).
The top of the Permian limestone sequence is depicted
by dark black chert bands which extend into a steeply dip- o o ping canyon (45 -50 slope), along which a sharp lithologic
change begins at the base. The contact along the canyon
base may be inferred as a reverse fault lineation, and it
is the base of a sequence of chert and arenite, undivided, which comprises Block (3).
Block (3) is described as Permian-Triassic in age and
is intersected by a major breccia thrust zone which reclines o o at a 25 -35 angle (Cross-section B-B'). The chert and are nite sequence are interbedded with thin lenses of sandstone and graywacke. The chert is typically dark gray to greenish- gray with reddish-brown iron oxide coating along fracture surfaces. The bedding units are commonly .5 meter thick and the areas directly above and below the thrust are evidenced by drag folding. The breccia thrust interval lies within a zone of calcareous argillite which is commonly with concentric iron banding, chert and calcite clasts. The breccia thrust zone is depicted as dark-reddish brown, highly silicified, with iron-oxide staining and subangular light to dark gray chert fragments. Oxide deposits commonly fill solution fractures and cavities within the thrusted material. Joint fractures within the breccia zone are commonly oriented o o S.80 W.65 .
Above the thrusted interval in Block (3) lies a se quence of nonmetamorphosed rocks. The lowest bed is under- 18 lain by the thrust fault and is composed of brecciated chert and dark gray silicified limestone. The next bed is thinly interbedded chert and brown-weathering ferrugi nous dolomite which contain the brachiopods Ctenalosia fixata and Stenocisma sp., which are identified as Upper
Permian (Cooper, 1957). The overlying bed consists of a radiolarian and spiculitic light to dark gray chert. The radiolaria within the chert have been identified as Permian by D. L. Jones, 1978.
Silberling (oral comm. August, 1981) has described a disconformity within the uppermost chert sequence of Block
(3). This disconformity is the boundary between the Upper
Permian and Middle Triassic. The concordant overlying rocks are predominately phosphatic mudstone, tuffaceous chert, shale and argillite. As presented by the literature, sand stone beds within Block (3) several meters above the dis- conformable contact with the Permian chert contain a fauna of
Ladinian ammonites of late Middle Triassic age (Silberling,
1979, 1981). Ketner (1981) has stated that the unfossili- ferous beds of chert between the two dated units possibly represent a disconformity or condensed section.
Several high angle faults are seen to intersect the
Triassic tuffaceous shale and phosphatic mudstone sequence of Block (4)„ The sequence is interbedded with four hori zons of dark gray to very dark gray tuffaceous shale and phosphatic mudstone. As well as the Permian limestone, these sediments were extensively sampled and analyzed for 19 vitrinite reflectance, total organic carbon and thermal alteration index,, The rock sampling program and test re
sults are outlined in the laboratory analysis section of
this text. The Triassic shale-phosphatic mudstone sequence
is classified as light to very dark gray with interbedded reddish brown to buff colored chert and argillite bands
(1.3 cm. to 2.5 cm. thick). These beds are coated with extensive dendritic iron staining and are banded with hema
tite. The bedding units are commonly thin (.3 cm. to 2.5 cm.
thick) with occasional calcite along bedding surfaces. The beds are rarely fissile and appear somewhat resistant to
surface weathering. There is evidence of minor drag folds throughout the sequence in Block (4) often noticeable above and below a series of minor faults. The beds are approxi mately 248 meters (813 feet) thick and dip at angles ranging o o from 30 at the base to 45 at the top. Above Block (4)
lies a narrow (approximately 100 meters) sequence of Quater nary colluvium which contains some Tertiary volcanic material.
The alluvial material is overlain to the south by a sequence of Tertiary volcanics (Cross-section B-B').
Structure
The southwest corner of the Bilk Creek Range is often referred to as the Quinn River Crossing locale. It has been studied in detail by Willden (1961-1963), Skinner and Wilde
(1965-1966), Thomas (1972) and Ketner and Wardlaw (1978-1981).
The Permian and Triassic rock sequence described can be stratigraphically subdivided into four major structural 20
blocks: (1) a Triassic-Jurassic? volcanic block, (2) a Permian limestone block, (3) a Permian-Triassic inter-
bedded chert and arenite block, and (4) a Triassic shale
block. The contacts between Blocks (1) and (2), and (2)
and (3) are represented by thrust faults, whereas the con
tact between the Upper Permian and Middle Triassic within
Block (3) is a disconformity. All blocks represented are
possibly allocthonous with respect to rock units exposed
in the surrounding mountain ranges. The ages of thrusting
of the blocks most likely occurred from early Triassic to
late Cretaceous time. Surrounding the locale are Quatern
ary alluvial fan, dune and lake bed deposits. The western
limit of the Quinn River locale section is bounded by a
typical basin and range fault. Thus the section exhibits post-depositional tilting and uplifting. o The beds strike predominately northeast (N. 15 E. o o to N. 60 E.) and dip to the southeast (S. 75 E. to S. o o 30 E.), respectively. The beds dip at an angle from 12 o to 75 depending on the location within the section. The change of dip in beds within the Bilk Creek limestone unit varies slightly and could be a representation of a bioher- mal facies change within the unit. The limestone unit has previously been unnamed, and its base has been cut by the
Quinn River thrust fault which overlies Permian volcanics.
The top of the unit is exposed and is overlain by inter- bedded chert, graywacke, sandstone and intrusives. This unit has been described as Middle to Upper Permian in age 21 and is again cut by a major thrust before intersecting a ferruginous dolomite and silicified limestone-chert se quence of Upper Permian-Lower Trias sic age. This thrust is characterized by evidence of drag folds above and be low its occurrence. A disconformity within the chert has recently been described by Silberling (1981), and is overlain by a sequence of interbedded tuffaceous shale and phosphatic mudstone.
The rocks exposed at the Quinn River Crossing locale are highly fractured. The major fractures predominately run parallel to bedding surfaces and are filled by secon dary cementation with calcite. Minor fractures run through the rock oftentimes in an irregular matrix, also secon darily cemented with calcite. Occasionally, lenticular
®bringers of light to dark gray chert are evidenced in the
Permian limestone indicating a silica rich secondary cemen tation process.
Some rock units in the locale have been subjected to drag folding associated with thrust zones. Due to the thrust- ing, cross-section B-B' depicts the four major blocks repre sented in the South Bilk Creek range as a system of imbricate structures„ 22
GEOLOGY OF THE SOUTHEAST PINE FOREST RANGE
Stratigraphy
The southeast Pine Forest Range section is approxi mately 308 meters (1,010 feet) thick. The section was mea- o sured in a S, 40 W. traverse direction across the strike
of the sequence. A reconnaissance geologic map with tra
verse P-P appears as Figure 7 and the stratigraphic col
umn appears as Figure 8. The cross-section P-P' appears
as Figure 9. The section is divided into units which are
characterized by distinctive lithologic types. The major
ity of the rocks in the section are sedimentary in origin.
There are three major horizons of limestone and a thick section of brecciated material.
The basal limestone crops out 75 meters due west of
Dyke Hot Spring, and is also found in a N. 30 W. trend
along strike to the northwest and southwest. The unit is depicted by a highly fractured, plastically deformed lime stone which is greater than 60% calcareous and in remainder, siliceous. The fractures are irregular in nature and are secondarily cemented with calcite. The unit appears typi cally as medium gray and very finely to medium crystalline.
Occasionally, the unit shows evidence of marblization and appears white in color. This suggests metamorphism of the rock unit at depth. The unit is also characterized by abundant crinoid columnal material which appears as dark gray and highly silicified. The fossil material is also greatly fractured and broken. R.30E. 1 | EXPLANATION ML Alluvial Fan Deposit Geologic Contact Quaternary Si. Thrust Fault, Lake Deposit loi Teeth on Upper Plate Undetermined )§ Breccia Normal Fault, dashed where inferred U Breccia Tuff Gravel and Dirt Roads
Andesite Strike and Dip of Beds "To0 N MN Limestone Jfi! 1/4 1/2 1.0 Limestone Scale! 2.5cm= 200meters ttPIC^- Limestone (covered) I Oin = 6 6 0 feet gure 7. Geologic Map of the. Dyke Hot Springs Area,SE. Pine Forest Range,Humboldt County Nevada with Traverse P -P iue . tairpi Clm o te ot Pn Frs Rne er Quinn Near Range Forest Pine South the of Column Stratigraphic 8. Figure AGE PERMIAN or OLDER I UNDETERMINED I TRIASSIC ie Cosn, ublt ony Nevada County, Humboldt Crossing, River Ll i i h z e T I I T D i THOLOGY G O L O H IT L :.: f — i i i ao« l z 11 lu' ------r r i i r Eir — :7 oml fault Normal hut fault Thrust i —i 308. 6 .1 8 0 3 - - 0 0 . 0 5 - .0 0 5 2 - -100.0 0 . 0 5 1 - 300.0 . 0 0 3 - THICKNESS (METERS) 200.0 Qaenr alluvium Quaternary — Limestone-Light medium gray(N5 to N7),massive to to N7),massive to gray(N5 medium Limestone-Light irt-ih ga-re 5G /)ltorpi lime GY6/1),lithographic (5 gray-green Micrite-Light abundant with ) /2 4 5R to 4 (N Interval- Brecciated massive N6); to (N3 gray medium to Limestone-Light rocks sedimentary and Volcanic — Foraminifera, of genus Endothvra,GlobivalvulinaT Endothvra,GlobivalvulinaT genus Foraminifera,of — bed friable,thin gray(N3toN2)j medium Shale-Light ooiel,ad suoetlra rni columnals Crinoid Pseudotextularia. and Nodosinella, marble. of evidence strong with fractures, along 226.74m. to 217.87 from (N6) shale gray bedded brown coloration of beds due to iron oxide oxide staining. iron atite) to due onite,hem beds (lim of coloration brown r as found. also are staining iron and bands, (SiC^) cementation calcite with associated fracturing extensive with |% < allochems. fine-grained; very subcrystalline; stone; inter- with bands iron Also thick thick. cm 30cm 0 3 are - 0 present 2 calcite with black of filling lenses calcite by extensive accompanied fracturing, crystalline,with contacts medium to bottom fine and Very top near bedded thin to rget 3t 0 n imtr Reddish diameter. in m chert 40m to and 3 calcite fragments sub-angular to sub-rounded also with calcite crystals in vugs and solution solution and vugs in crystals 6/1), 5Y calcite to 6/1 with (5GY also gray white-pink-dark filling, crystalline medium to fine very top, at bedded thin section. of top at conodont primitia Epiaondolella and sp. Arcestes Ammonite, cavities, 6 0 to 7 0 % calcareous, with secondary secondary with calcareous, % 0 7 to 0 6 cavities, ded with calcite filling on bedding surfaces. surfaces. bedding on filling calcite with ded ria Sae 2. c 50 meters m 0 5 = cm .5 2 Scale: ertical V PTI N IO T IP R C S E D . i. 164 fet fee 4 6 1 = in. 1.0
2 4
25
Feet pi Meters - 5200 1585
- 5000 1524
- 4800 1463
- 4600 1402 - 4 4 00 1341
— 4200 1280
r p -4 0 0 0 1220
t - 3800 1159
* —3600 1098
/ — 3400 1037
-----3200 976
, — 3000 915
s— 2800 854
' — 2600 793
EXPLANATION
SYMBOL DESCRIPTION
Q uaternary * Alluvial Fan D ep o sit
Undetermined T jjT; Breccia
T riassic m . Breccia Tuff
Trias sic DiS A n d e s ite
Triassic HI L im e s to n e
w , Limestone Permian or Older
Limestone (covered)
Geologic Contact SCALE. 2.5cm=200metere Thrust Fault I .Oin. =660 feet Normal Fault
Figure 9. Cross-Section P-p^ S.E. Pine Forest Range,Humboldt County, Nevada Foraminifera collected from location PFPL#6 were identified from thin-section. The specimens were classi
fied as genera Endothyra, Globivalvulina. Nodosinella and
Pseudotextularia indicating an age date of Devonian
through Permian. The specimens are discussed further in the laboratory analysis section of this text. From sur
face outcrop, the unit appears to be 10 meters (33 feet) in thickness. However, the base is not exposed and inter
sects a high angle dip slip fault (Cross -section P-P').
The limestone unit is overlain by a covered interval of
alluvial material. The terrain slope (15° within the
covered interval) above the basal limestone is eventually intersected by a major limestone bench of Permian age
along traverse P-P*. The thickness of the covered inter val is approximately 27 meters (89 feet).
The Middle to Upper Permian limestone terrace has an o average slope of 29 . The unit is predominately a light to medium gray, very fine to medium crystalline massive limestone. The unit also is greater than 60% calcareous and in remainder, basically siliceous due to secondary ce mentation along fractures and is fractured along bedding surfaces. The fractures are filled extensively with cal- cite crystals and commonly display solution cavities and channels. The solution channels are coated with iron oxide as hematite and rhombohedral calcite which is whitish-pink to dark gray in coloration. The unit is approximately 90 meters (297 feet) thick.
At the top of the limestone sequence lies a shale unit which is approximately 12 meters (39 feet) thick. The shale is light to dark gray and also exhibits extensive fracturing along bedding surfaces. The fractures occur between thin bedding units (2-5 cm. thick) within the shale and are filled with a calcite and iron oxide matrix0 The iron oxide is predominately limonite, which also occurs as nodules.
Above the shale horizon lies a micritic limestone averaging 6 meters (20 feet) in thickness. Bedding units are commonly greenish-gray, very finely to medium crystal line and .5 meter thick. The zone is nonfossiliferous and displays evidence of less than 1% allochem material. The bedding surfaces of this horizon are also coated with cal cite mineralization.
A thick sequence of brecciated material overlies the micritic limestone sequence. This unit averages 65 meters
(213 feet) in thickness. The breccia contains abundant subrounded to subangular calcite and chert fragments which are .3 to 3.8 cm. in diameter. A reddish-brown coloration of the beds is due to iron oxide staining as limonite and hematite. The brecciated zone also contains a 7 meter lens of medium gray shale (from 162 to 169 meters within the section). The shale is friable and contains many calcite 28
stringers within fractures on bedding surfaces. The bedding units are commonly 2 cm. to 5 cm. thick with a reddish-brown iron oxide coating„ All limestone and shale units within the section were sampled for vitrinite reflectance and ther mal alteration index (refer to laboratory analysis section of the text) „ The breccia horizon appears to be sedimentary in nature, however, a high angle thrust fault may intersect this zone due to the subangular nature of clastic fragments within the central portion of the unit (cross-section P-P').
A thin unit (1 meter thick) of light gray shale caps the brecciated sequence intervale
Overlying the brecciated sequence is an Upper Trias- sic (very late Kamian to early Norian) limestone unit 67 meters (220 feet) thick. The limestone has been recently dated on the evidence of the conodont Epigondolella primitia, which has a range of very late Kamian to early Norian
(Silberling and Wardlaw, 1981). The Upper Triassic limestone approaches a subvertical (80°) angle of dip near the top of the sequence. The slope of the bench is also steep, being
45° on the average. The limestone is massive to thin bed ded at the top of the sequence and contains the ammonoid
Arcestes carpenteri of Upper Triassic age which was located and collected. This ammonoid represents the ceratite sub order, and is characterized by a ceratitic suture pattern.
The unit is depicted as light to medium gray, very fine to medium crystalline with extensive fracturing present and accompanied by calcite filling. Often lenses of black 29
calcite are evident (20 cm. to 30 cm. thick) as lenticular
stringers. Also present are bands of hematite 30 cm. in
thickness. A lens of interbedded, medium to dark gray shale
occurs from 218 to 227 meters within the section. The fri
able shale lens also exhibits extensive fracturing along
bedding surfaces with calcite filling. At the crest of the
Upper Triassic limestone sequence deposits of caliche are evident.
An Upper Triassic sequence of volcanics overlies the
Upper Triassic limestone. The intrusives have recently
been studied and dated by Russell and Speed (1980) of
Northwestern University. The first intrusive sequence is
comprised of meta-andesite. It is classified as a porphy-
ritic pyroxene andesite and andesitic-basalt. The unit
displays a gradational contact with overlying tuff breccia
and poorly sorted volcanic breccia. The tuff breccia se
quence is depicted by an interbedded mixture of tuff, mas
sive tuff breccia, andesite, andesitic basalt, porphyritic
pyroxene and hornblende. Within the igneous sequence are
discontinuous lenses of white to dark gray Upper Triassic
limestone from 3 to 60 meters (10 to 200 feet) thick. The
thickness of the entire volcanic sequence is approximately
700 meters (2,296 feet).
Structure
The southeast Pine Forest Range is unique in that no other group of rock units in the Quinn River Crossing area 30
exhibits similar structural or stratigraphic characters. Resting on the top of the Permian and Triassic accretionary
sequence of limestones and shales is a Triassic sequence
of volcanics comprised of tuff breccia, basalt and andesite.
The area was originally mapped by R. Willden in 1963 and re
mapped by J. Smith in 1973. The area was originally thought
of as having a Permian age date assigned to the volcanic se
quence on top, and this sequence was designated the Happy
Creek Volcanic sequence. This resulted in the basal topo
graphic limestone sequence being designated as Triassic age.
Recent field work and laboratory analysis of the sequence by
the author, N. J. Silberling and R. C. Speed (1980-1981) describes a reversal of previous age dates assigned to the proposed northwestward plunging anticline. This recent evi dence suggests a structurally oriented northwestward reclined axis orientation of the beds in which the hade of the thrust fault approaches subvertical.
The Pine Forest Range has a steep eastern front and a relief between 305 to 1,525 meters (1,000 to 5,000 feet).
The highest point, Duffer Peak, rises to 2,883 meters (9,458 feet). The Upper Triassic volcanic sequence and older units are exposed along the southeast front of the range with the older Permian rocks on the east side. A high angle normal dip-slip fault separates the recent Quaternary alluvium from the sequence of interest. The abrupt east front of the range is believed to be due to late Tertiary to Recent dis placement of this frontal fault, and Dyke Hot Spring may be 31
controlled by this fault (Willden, 1964) .
The strikes and dips of the beds remain fairly uni
form within the southeast Pine Forest Section. However,
the dip angles become increasingly steeper towards the Up per Triassic volcanic sequence on top (Cross-section P-P'). o The beds strike N. 30 W. with a variation of 5 degrees in o either direction. The beds dip at angles ranging from 15 o at the base to 80 at the top. The change of apparent dip angle in the beds markedly increases above a zone of brec- ci&tion. The direction of dip remains fairly constant at o S. 60 W. (also with a variation of 5 degrees in either direction, depending on the orientation of strike). The zone of brecciation could be a result of high angle thrust ing associated with this complex exposure of eugeosynclinal sediments. The rocks exposed in the southeastern Pine
Forest range are highly fractured. The dominant joint o o sets within limestone units appear to be S. 40 W. 45 , o o and N. 50 W., 35 . The first set appears to be the pre dominant set and the second set appears to be the minor joint set.
All rock units exposed in this sequence intersect a series of transverse faults of which lineations occur with in the base of canyons trending northwest to Bishop Canyon.
The units converge slightly towards the lineaments and are slightly offset by them. 32
CORRELATION
Biostratigraphical Description of the Permian
The Permian period occurred from 230 to 290 million
years ago. It was called Permian by Sir Roderick Murchison
after the province of Perm in Russia where rocks of this
age are extensively developed. The Permian of the Quinn
River Crossing area can be correlated with other Permian occurrences of the eugeosyncline on the basis of Wrangel-
feuna. A correlation chart of Permian units in west ern North America appears as Figure 10. These units are classified as belonging to a shallow water, volcanic pro vince which is most widespread in northwestern Nevada. In this area included are the Happy Creek volcanics consisting of breccia and lava (mainly pyroxene andesite and minor ba salt and dacite), and an overlying unit of pillow lava and breccia, limestone and volcanogenic clastic rocks. The Un named Limestone unit contains Permian fusulinids (Willden,
1963); rocks correlated with the Quinn River Crossing se quence contain Permian brachiopods (Gianella and Larson,
1960, Howe, 1975). The rocks of the Permian volcanic pro vince are considered to have formed within a magmatic arc
(Willden, 1963, Silberling, 1975, Speed, 1977).
The fauna of the Wrangellian province of the eugeosyn cline represent shallow water reef environments during the
Permian. Howe (1975) has stated that the Permian fauna at iue1. orlto o Prin nt i Wsen ot America North Western in Units Permian of Correlation Figure10. PERMIAN SYSTEM J U o 5 E ( Q UJ Q _l 3 a. J U a. tr O < Q < WOLFCAMPIAN 3 _l < 3 Q. OD Y FM CYN ROAD To Section) (Tvoe LEONARDIAN AMERICAN S SECTION OCHOAN TANDARD CAPITAN WORD
OOE BUTTE COYOTE W RANGELLIA N RANGELLIA W BRACHIOPODS Coe,957) 7 5 (Cooper,19 OREGON FM.
LIMESTONE WRANGELL1AN McCLOUD (Coogan,l960) NOSONI CALIFORNIA DEKKAS NORTHERN FAUNA AND FMS (Modified from Howe, 1975) Howe, from (Modified AGLA FAUNA RANGELUAN W NORTHWESTERN LC ROCK BLACK SECTION (Howe,1975) NEVADA 33
QUINN RIVER CROSSING WRANGELUAN BRACHS 34
the Black Rock section represent a patch reef environment where reef organisnss are settled on a relatively firm founda
tion in shallow waters. These isolated patches usually lack
typical reef features such as forereefs and lagoons. An
other term for this type of reef is a table or platform
reef. They are also characterized as isolated patches of reef smaller than atolls.
An organic reef proper is a solid mass of calcium
carbonate deposited by organisms near the surface of the
ocean where waves beat vigorously upon it. The action of
the waves continually creates sand and rubble, thus pro-
nutrients and aerated water for the marine organ
isms to build faster than the erosional process can pro ceed. As a result, the reef can continue to grow and supply a great deal of fragmental debris which surrounds and half buries the reef. The formation of the reef complex also modifies the action of the waves and other shore processes.
This provides a new and more sheltered environment for other kinds of organisms (such as brachiopods) which then add their contributions to the growing deposit. The whole de posit (which includes the reef proper and the sediments accumulating around it in the environment it creates) is called a reef complex or bioherm.
Reefs usually are formed as mounds or ridges, but they can also grow in irregular, assymetrical forms. The framework of the reef is very strong and can form at very 3 5
steep angles and therefore the reef complex can lack well-
developed stratification, A wide variation exists in the
height and aerial extent of reefs. A series of intercon
necting reefs can be developed by a transgressing and re gressing sequence of the sea.
The prolific oil production of some reefs is a re
sult of excellent porosity and permeability. The porosity
is a function of the total amount of void space in a given
volume of rock and is either initial or induced in a reef
bioherm. The initial porosity is attributed to the space
between the inner and outer walls of the shells in a varied assemblage of organisms.
Major differences between modern reef complexes and those of the late Paleozoic to early Mesozoic are:
1. Modern reefs are very well aerated compared to ^ suggested stagnant basin event during deposition (Newell, et al, 1953).
2. Modern reefs are built principally of corals, whereas Permian reefs (such as those found in West Texas) were constructed mainly by sponges, algae and bryozoa.
Oil confined to reef environments is trapped or stored within the complex by an overlying cap of impervious sedi ment. The hydrocarbon source can be either migrant or indi genous to the reef.
The Bilk Creek Section
The limestone section at the Quinn River Crossing locale is also a representation of a shallow water bioherm. 36
The fauna exhibited at the locale contains numerous specimens
of fusulinids, brachiopods, conodonts, corals, pelecypods, crinoids and bryozoa.
Fusulinids are also considered to have lived in warm
marine waters. They are chiefly utilized as index fossils
for dating bioherms within the Permian and other geologic periods. In the standard West Texas Section the genus
Sffky.?.g,er i n a is characteristic of the lower Permian, Parafu- sulina of middle Permain, and Polydiexodina of upper Per mian.
The fusulinids represented at the Permian limestone
section near Quinn River Crossing are defined by seven spe
cies and assigned to four genera. The species Pseudofusuli-
■Iie ^ ^ a dunbari, Schwagerina rotunda. Eoparafusulina spissa.
and Chalaroschwagerina tumentis are described (Skinner and
Wilde, 1965). The first three are characteristic of the
middle part of the McCloud Limestone and the fourth corres
ponds to the Coyote Butte Limestone of east central Oregon
and to the upper McCloud Limestone section. The McCloud
section ranges in age from Middle to Late Wolfcampian. Based on this evidence, Skinner and Wilde have noted that the Mc
Cloud Limestone and the Bilk Creek Unnamed Limestone must have been closely associated at the time of deposition. In addition, the following fusulinids have been reported as representing the Unnamed Permian Limestone within the Bilk
Creek Section by Skinner and Wilde (1965). Their work is 3. detailed continuation of previous studies by Dr0 R. M.
Jeffords of the Esso Production Research Company (1957)
and Dr. J„ Harbaugh of Stanford University (1957). (SI)
Pseudofusulinella rotunda sp. „ ~ ieffordsi spQ pusilla sp. Eoparafusulina concisa sp. bellula sp. Chalaroschwagerina formosa sp. „ ampla sp. M globalaris sp. „ solita sp. M eximia sp. decora sp. Schwagerina munda sp. ieffordsi sp.
Genera of brachiopods which correlate the Black Rock section with the Unnamed Limestone sequence of Quinn
River Crossing are Rhynchopora sp., Derbvia sp., Dielasma
sp., Anidanthus sp., Crurythyris sp. and Meekella sp. (Howe, 1975, Ketner, 1981).
The brachiopod faunas described also correlate strongly with the Coyote Butte Limestone (Cooper, 1957).
The Bilk Creek Limestone sequence designated by Harbaugh and Jeffords almost completely lacks brachiopods and cono- donts throughout the massive lower part. The limestone becomes silty near the top with brachiopods and conodonts becoming abundant. The conodonts are all of Hindeodus sp., indicating a shallow water deposition (Wardlaw and Collinson, 1979). 38
The Southeastern Pine Forest Range (Permian or Older) Limestone Formation:
The basal limestone is dated as Permian or older in
age o It is located immediately west of Dyke Hot Spring
in the southeastern Pine Forest Range. The unit contains
the foraminifera genera Endothyra sp., Globivalvulina sp.,
Nodosinella sp., and Pseudotextularia sp. which range from Devonian to Permian in age.
Ibree kilometers northwest of Dyke Hot Spring, the
lowest limestone exposed on the east Pine Forest Range is
located at Bishop Canyon. N„ J 0 Silberling (written com munication with R. Willden, 1956) has reported on a collec tion (USGS loc.M792) within the limestone as follows:
"Isastraea-like colonial hexacorals. Crinoid columnals. Radially ribbed carditoid pelecypods (Septocardia?). Objective age: early Mesozoic.”
The Permian and Triassic limestone beds described in this text appear to converge and overturn structurally in the Bishop Canyon area. Therefore, the assemblage des cribed by Silberling may be associated with the very late
Karnian to early Norian (Upper Triassic) limestone se quence presented in this text.
The Black Rock Section
The Black Rock section is the westernmost exposure of fossiliferous Permian units in the state of Nevada. Fu- sulinids (the major stratigraphical aid for subdivision of 39
the Permian), are not available at the Black Rock section (Howe, 1975). In addition many of the brachiopods and the
single ammonite genus (Medlicottia-Lower Wolfcampian to Lower
Ochoan age) represented at Black Rock are long ranging forms,
and have virtually no stratigraphic value (in comparing the Permian with the North American type section in West Texas).
However, some of the Spirifer genera: Spiriferella.
Waagenoconcha, Neospirifer, correlate strongly with the
Glass Mountain of West Texas. Howe has stated:
''The fauna at Black Rock is most likely ’Roadian’ (Road Canyon Equivalent) and/or possibly Lower Word in age."
This would represent an equivalent age of Upper Leonardian to Lower Guadalupian in age for the Black Rock section.
The Klamath Mountain Section
The Klamath Mountain section of northern California consists of the McCloud Limestone and the Bollibokka group. The McCloud Limestone represents approximately 488 meters
(1600 feet) of thickness in the Bollibokka area. The Bol
libokka group is represented by the Nosoni and Dekkas for mations. The light to dark gray, medium to thin-bedded
limestone is very resistant to erosion and noted as a cliff
former (Coogan, 1957). The McCloud Limestone conformably overlies the Baird formation which is Mississippian to
Early Permian in agec The fossiliferous beds within the
McCloud Limestone are noted as Wolfcampian to Leonardian in age (Thompson and Wheeler, 1946). Within the McCloud 40
Limestone there is strong evidence of recrystallization and marblization.
The N o s o m formation conformably overlies the McCloud Limestone, and its type locality is at Nosoni Creek. The
Nosoni formation's total thickness is greater than 1890
meters (6200 feet) thick. The Nosoni formation is charac
terized as a gray, medium bedded limestone which contains
black chert at the contact. Also within the Nosoni are
mterbedded tuffs. Thompson and Wheeler (1946) recognized
several species of fusulinids within the Nosoni and McCloud
formationso The most predominant genus is Parafusulina of
Parafusulina nosonensis. Parafusulina virga and
-ara£usul:Lna californica are identified. Brachiopoda fauna exhibiting strong similarities to Permian outcrops in north western Nevada and east central Oregon are Waagenoconcha
SP*J Anidanthus sp., Muirwoodia sp., Rynchopora laylori sp., Crurythyris sp., and Spiriferella sp.
The Dekkas formation conformably overlies the Nosoni formation and is represented by approximately 1,158 meters
(3,800 feet) of tuffaceous sedimentary rocks. Known fossils from the Dekkas formation were collected between Town and
Horse Mountains in Section 8, T.24 N., R.3 W., Bollibokka
Quadrangle, Shasta County, California. The Dekkas forma tion also contains Parafusulina sp. similar to the under lying Nosoni formation. It has been dated as Guadalupian in age and described by Diller (Parafusulina californica). m m m m
41
The productoidbrachiopoda Muirwoodia and Spir ifere 11a sp. are also identified, and bear resemblance to species in northwestern Nevada and Oregon. Other productoid brachi-
opods represented are Chonitella sp. indet. and Liostella sp. indet. (Coogan, 1957).
The Unnamed Permian Limestone at the Bilk Creek section displays a close resemblance to the McCloud Lime stone and Dekkas formation of Bollibokka group. The Shasta
Lake area fauna are currently being studied in detail by N. J. Silberling of the USGS, Denver, Colorado.
The Coyote Butte Section
Cooper (1957) correlated the Coyote Butte section in east central Oregon with the Lower Word formation of the
Glass Mountains of West Texas. The formation is also clas-
the time as Road Canyon equivalent, again assign ing the fauna of this area an Upper Leonardian to Lower Guadalupian age.
The Bilk Creek Limestone and the Oregon section share the following genera: Rynchopora, Derbyia, Anidan- thus, Dielasma, Crurythyris and Meekella. The species are also similar to those of the Black Rock section in that they do not display the characteristics of typical
American species. A Boreal influence may account for this phenomenon. Reexamination of the Coyote Butte Sec tion (Cooper, 1957), the Dekkas Formation (Coogan, 1960), the Cache Creek Formation in British Columbia (Kindle, 42
1926), the Bilk Limestone (Willden, 1964) and the Black Rock section (Howe, 1975) suggests that the sections were subjected to cool water temperatures„ According to Howe:
''The faunas of westernmost North American represent a characteristic taxonomic composition which is not but^also^Boreal f0rmS and Tethyan forms
World wide cooling has been noted by the effect of
Permian glaciation during this period. Melting of the gla
cial ice pack resulted in a marine transgression, and cur rents from the melting ice were markedly cooler. Thus,
more tolerant cold water species migrated to the Coyote
Butte, Black Rock, Bilk, Cache Creek and Klamath locales. The cold water species at these areas were possibly evol
ving at a much slower rate than the warmer, shallower marine environments of the West Texas embayment area.
According to F. G. Stehli (1957), there exists a
sharp boundary between 50° and 60° N. to the apparent ranges of a number of Permian marine invertebrates. The boundary is suggested as being temperature controlled and may represent an interface between the subtropical and temperate marine temperature belts of the Permian. The faunal boundary parallels the earth's present equator and precludes the proposed shifting of the earth's poles with respect to continental drift of the major land masses of the northern hemisphere. Stehli (1973) further states that caution must be exercised when interpreting poles 43
climatic data. The comparison of modern paleoclimatic models is based on present day climates and thus, climatic
models which developed over long ranging periods of time
are difficult to interpret. This is due to the current
lack of adequate paleoclimate statistical data distribu tions in space or time.
Biostratigraphical Description of the Late Middle and Upper Triassic
The Karnian and Norian Stages of the Upper Triassic (195-218 m.y.o.) were named by Mojsisovics (1869). They were described after a variety of limestone rock units which
are representative of the Stages, and located in the Hall-
statt area of the northern Alps of Austria. Bittner (1892) later introduced the Ladinian Stage (218-225 m.y.o.) for
the Buchenstein, Wengen, and St. Cassian beds located in
the southern Alps of Italy. These beds were previously regarded as Norian Stage by Mojsisovics.
N. J. Silberling and E. T. Tozer (1968) have recently subdivided the Karnian, Norian and Ladinian Stages of the
Triassic into zones or beds for western North America.
The Juvavites subzone of the Tropites subbullatus zone described by J. P. Smith (1927) for the very late Karnian to early Norian has been reclassified as the Tropites welleri zone (Silberling, 1951). The Tropites welleri zone corresponds to the fauna collected at the Triassic limestone sequence of the southeastern Pine Forest Range. 44
The Ladinian classification for the late Middle Triassic beds xn the south Bilk Creek Range corresponds to Daonella
^ -mmeli beds ^cognized in the Humboldt Range, Nevada. The flat clams" Daonella sp., Posidonia sp., and Protrachv- ceras sp. are located within the marine Triassic unit of
the south Bilk Creek Range. These thin-shelled pteriacid
and pectinacid bivalves most closely approach the Triassic ammonoids in their stratigraphic utility.
The Triassic rocks exposed in the southern Bilk Creek Range and southeastern Pine Forest Range are possibly alloc-
thonous with respect to other rock unit exposures in the Quinn River Crossing area. The late Middle Triassic shale unit in the southern Bilk Creek Range is the main exposure
of Triassic shale in Humboldt County, Nevada, and has been
designated as the Quinn River Formation by R. Willden, 1961.
The two outcrops do not appear to correlate with each other, and a great deal of research is still needed to extend the degree of correlation of these rock units with units ex
posed in the neighboring Jackson Mountains. Other occur rences of Triassic rocks in Humboldt County are the Dun
Glen Formation, the Grass Valley Formation, the Winnemucca Formation and the Raspberry Formation of Late Triassic
Age, and the Natchez Pass Formation of Middle to Late Triassic Age. 45
The Quinn River Formation
The Quinn River Formation of the south Bilk Creek
Range has been assigned a late Middle Triassic Age on the
basis of pelecypod fossils fromU.S.G.S. loc. M95 identi
fied by N. J. Silberling (written communication with R. Willden, 1956):
Daonella sp. Posidonia sp. Protrachyceras sp.
The formation was further described by Willden (1964)
as being correlative with the Prida Formation, exposed
in the East Range south of Humboldt County in Pershing County, Nevada.
The formation is about 248 meters (813 feet) in
thickness and overlies a non-fossiliferous horizon des cribed as a disconformity. The base consists of about
30 meters of interbedded gray chert and siliceous shale.
these beds also exists a thin horizon (2 meters) of sandstone containing ammonite molds of Ladinian Age
(personal communication with N 0 J. Silberling, 1981).
Above the chert, the formation is principally light gray to buff-colored shale with a few thin beds of dark gray to grayish brown limestone and chert (1 to 1.5 meters thick). Gypsum also occurs within the beds and can attain
2 to 20 cm. in thickness. Within the unit occur 4 hori zons of dark gray to very dark gray shale which are rich in organic carbon content. Values as high as 3.46% organic 46
carbon have been detected. It is within these horizons
that a possible petroleum source bed has been identified.
The.,Southeast Pine Forest (Triassic) Limestone. FnrmaM™
The Upper Triassic (very late Karaian to early Norian) limestone of the Pine Forest Range has been dated recently
on the basis of the ammonoid, Arcestes sp. and the conodont
primitia. Specimens were collected at the top of the stratigraphic section in a thin bedded, silty
limestone matrix. The limestone also contains dark gray
phyllitic shale horizons which are non-fossiliferous„ The
locale appears to be younger than the late Middle Triassic
(Ladiman) Quinn River formation of the Bilk Creek Range. Fossil age dates were confirmed in both locales by the
author and the U.S.G.S. in Denver, Colorado (personal
communication, 1981). The Triassic limestone beds of the
Pine Forest may correlate with the Triassic-Jurassic (?)
limestone beds located in Alaska Canyon of the western
Jackson Mountains (Hobo Canyon Quadrangle, T.39 N., R.30 E.). A correlation may also exist with the Mesozoic (?) limestone
bed of the Bishop Canyon area (faunal assemblage described
by N. J. Silberling, 1956) located 3 kilometers northwest
of Dyke Hot Spring, southeast Pine Forest Range.
The limestone units which are located in the Pine
Forest section are currently believed to be allocthonous blocks which have been transported over an indeterminate length after deposition within the eugeosynclinal trough. 47
The geology of this locale is very complex and has been
mapped recently by Branch Russell of Northwestern Univer
sity, 1980. Lynn Fuller of the Mackay School of Mines is
currently studying the stratigraphic relationships between
the Alaska Canyon and Pine Forest locations. A comparative
correlation chart for the south Bilk Creek Range and the southeast Pine Forest Range appears as Figure 11. CL LxJ c < <1 o h- Q; CO CO c
iue 1 Creain f ema ad rasc tairpi Uis n h Suh ik Creek Bilk South the in Units Triassic Stratigraphic and Permian of Correlation 11.Figure SYSTEM (Muschelkalk) Lower (Bunter) Lower ag ad otesen ie oet Range Forest Pine Southeastern and Range (Keuper) SERIES E Lower Middle Upper Upper RPA UNITS UROPEAN ) Kazanian-Ufimian Sakmarian Kungarian Artinskian Tartarian Scythian Rhaetian STAGE Ladinian Anisian Karnian Norian OT AEIA UNITS AMERICAN NORTH Wolfcampian Leonardian Guadalupian SERIES Ochoan Capitanian Roadian Wordian STAGE Unnamed Chert Arenite UnnamedChert Unnamed Chert Arenite UnnamedChert
Quinn River Formation River Quinn Quinn River Thrust QuinnRiver hut Fault Thrust Upper Plate Plate Upper Limestone SOUTH RANGE Unnamed V-rrACLlrV BILK _____ 1 SOUTHEASTERN Permian or Older Older or Permian T rs Fault hrust Limestone Limestone FOREST RANGE PINE 7 ____ 1 I 49
LABORATORY ANALYSIS
Introduction
This section presents a description of the mineral lithology, composition and fauna obtained by thin section analysis. The thermal alteration index, vitrinite reflec tance, and total organic carbon analysis are also catego
rized and interpreted. The laboratory data was provided by the author and designated testing labs contracted by
Sunmark Exploration Company of Denver, Colorado. For rock sample locations, refer to Figures 12 and 13„
The original source of hydrocarbons within the sub surface is centered in organic rich fine-grained sedimen tary rocks. The hydrocarbons can migrate from the fine grained source facies into more porous intervals where they accumulate in stratigraphic or structural traps. Geothermal diagenetic processes (catagenesis) mobilize the hydrocarbons trapped within the fine-grained source beds and aid in their migration to adjacent reservoir facies of greater porosity.
A potential source bed for oil or gas is defined as any type fine grained clastic or carbonate mud deposited in envir onments in which the organic matter can be preserved under reducing conditions. Depositions which favor such condi tions are: (1) offshore marine sediments, (2) restricted nearshore sediments, (3) deltaic sediments, (4) lacustrine sediments, and (5) back-reef lagoonal sediments. The type
&.30E. EXPLANATION AGE Rock Sample Location Alluvial Fan Deposit Geologic Contact Quaternary Thrust Fault, Lake Deposit Teeth on Upper Plate Undetermined Breccia Normal Fault, dashed where inferred Triassic Breccia Tuff Gravel and Dirt Roads
Triassic Andesite Strike and Dip of Beds ~170 ° N MN Triassic Limestone JfiL 0 I# 1/2 Permian or Limestone Scale! 2.5 cm = 2 0 0 meters Older Limestone (covered) / 1.0 in = 6 6 0 feet figured. Rock Sampling Program and Traverse,SE. Pine Forest Range, Humboldt County, Nevada 52
of environmental sequence displayed at the Quinn River
Crossing locale is offshore marine sediments. However,
the source bed will only be able to generate oil and gas
under certain geothermal conditions. Thus, the main cri
teria for assessing hydrocarbon source rock quality in
any basin of exploration interest are: (1) organic matter
type, (2) richness or quality of a given organic matter
type, (3) thermal maturation. The thermal maturation of
petroleum is a result of depth of burial of sediments, temperature and geologic age.
The main parameters which define a petroleum explora tion reservoir study are listed:
(1) Source, including organic matter type, abundance of organic matter, areal and stratigraphic distribution.
(2) Generation, defined as organic matter source type, and time-temperature history.
(3) Migration, expressed as hydrocarbon generation, fluid movement and geologic time involved.
(4) Accumulation, defined by trapping and sealing hydrocarbons and geologic time involved.
(5) Reservoir Potential, defined by size, morphol ogy, permeability and porosity.
In petroleum exploration the parameters become better defined with the accumulation of geophysical data derived from gravity, seismic and well log profiles and geochemical analysis of source rock units. 53
Thin Section Analysis
The following thin sections were prepared and described in order to obtain greater lithologic control on the strati graphic sections exposed at the south Bilk Creek Range and
southeast Pine Forest Range. Additional thin sections were
prepared by Agat Consultants of Denver, Colorado, 1981. These
sections are included in Appendix IV of this text. The samples are described by rock sample location designations and by measured distance along traverse B-B' for the south Bilk
Creek Range. The samples in the southeast Pine Forest Range are described by rock sample locations.
South Bilk Creek Range
BCPL-12
Medium gray limestone, very fine to medium crystalline, with
an irregular calcite matrix as stringers, with secondary
cementation as Si02, with very fine grained deformed allochem grains (non-identifiable).
BCTS-15
Medium to dark gray shale, silicified, with irregular frac tures containing light calcite filling; later replaced and coated with Fe203 staining as hematite, occasional irregular dark phosphatic filling accompanied with FeC>3 , 54
BCTS-16
Black shale, slightly phyllitic, with light calcite stringers concordant to bedding planes. Barren of fauna.
BCTS-18 Same as above.
BCTS-19 Same as above.
BCPL-O+O meters
Light to medium gray limestone, very fine to medium crystal
line, with fractures containing calcite replacement and iron
oxide staining as hematite, with Rugosa sp. coral cross- sections to 20 mm. diameter.
BC-1130,5 meters
Light gray-medium green graywacke (turbidite), with irregu
lar fractures with Fe203 staining as hematite, with occa
sional dark chert fillings accompanied by Cu+ staining.
With slump features expressed as sole markings and flute casts.
BC-1157.0 meters
Dark gray shale, with calcite stringers normal to bedding planes, with occasional elongate phosphatic pellets 0.5 mm. in diameter. w m m m HR 55
BC-1255.0 Meters
Medium orange to reddish brown sandy silt stone, very
altered, slightly calcareous, with irregular Fe2C>3 stain
ing along fractures as hematite, with slump features (sub
rounded), poorly sorted, with abundant limonite and hema tite staining on individual grains.
BC-1285.0 Meters
Reddish brown dolostone, v.f.-m.crystalline, highly silici-
fied with Si02, with discordant calcite clasts, fillings
as lenses of dark chert and light calcite stringers, with
very irregular fractures containing hematite staining„
Chert contains clear outlines of radiolaria.
Thin Section Analysis
Southeast Pine Forest Range
PFPL-6
Light to medium gray limestone, very fine medium crystalline, greater than 60/o calcareous, remainder siliceous with irregu
lar fractures containing calcite and dark chert filling, evidence of marblization, with slight trace hematite staining along fractures. The following fauna is identified:
Genus Range
Endothyra L. Carb Permian Globivalvulina Carb o Permian Nodosinella U. Dev. Permian Pseudotextu1aria Carb. Permian 56
PFPL-9
Medium to light gray limestone, very fine to medium gray,
greater than 60% calcareous, with very irregular fractures
containing Si02 (dark chert) filling, strong evidence of
plastic defermation, with slight trace of reddish hematite
staining along deformed fractures plus light calcite fill ing; with abundant limonite staining along fractures. No
visibly identifiable allochem grains (less than 5%).
PFPS-1Q
Medium to dark gray shale, with extensive evidence of ir
regular fracturing and slump features as local deformation, with light calcite and dark chert filling within fractures, with occasional iron oxide staining as limonite (FeOOH) n H 20 along fractures and as coating on grains. No fauna evident.
PFPS-11
Medium to dark gray shale, with calcite stringers (light to dark) concordant to bedding, with evidence of subrounded slump features, with occasional trace of reddish brown hema tite staining as coating on fractures. No fauna evident.
PFPS-13
Breccia, light to medium gray, with subangular light calcite clasts, with extensive fracturing containing dark chert ma terial as matrix, clasts to 12 mm. wide by 8 mm. thick, with extensive hematite and limonite staining along fractures and as a coating on clasts. PffT S.~ 14 (Note: Agat also analyzed)
Medium reddish brown to gray shale, with thinly interbedded
(2 mm. thickness) light calcite stringers normal to bedding
planes and transverse to bedding planes, with abundant dark
chert nite, hematite along fractures. No fauna evident. PFTS-16 Dark Gray shale with extensive slump features and dark and light calcite stringers normal to bedding planes; also with calcite stringers and slump features discordant (cutting across) bedding planes as an extension of calcite minerali zation within slump features, with occasional yellow limo- nite coating along fractures. No fauna evident. PFTL-17 Light to medium gray limestone, very fine to medium grained, with light calcite stringers along irregular fractures both normal and transverse to bedding, with occasional iron oxide stainings as hematite (Fe2C>3 ) along fractures, with exten sive deformation of dark (Si02) allochem material non- identifiable. ■PFPL- 19 (Note: Agat also analyzed) Dark to medium gray limestone, very fine to medium grained, with extensive fracturing containing calcite and Si02 filling (dark chert), extensively deformed, with occasional slight trace of hematite staining along fractures as coating, with 57. allochems (non-identiffable), evidence of marblization. 58 Total Organic Carbon Analysis (TOC) The total organic carbon content of a rock sample is a direct indication of the total organic richness„ Only a small fraction of organic matter which is converted into geochemical bitumen migrates from its original source bed° A sufficient quantity of organic matter must be pres ent in a sedimentary rock unit before it can be rated as a potential source bed. In general, a shale unit must con tain an organic content above 0 .5% and carbonate rock units must have 0 o12%„ Geochem Laboratories describes the geo chemical method for determining total organic carbon con tent in their publication 'Source Rock Evaluation Refer ence Manual, 1981.' Vitrinite Reflectance (%Ro) Vitrinite is a maceral of coal which is derived from the tissue portions of plant material. It is commonly a constituent of coals and can also occur as individual par ticles within the kerogen of sedimentary rocks. The mea surement of vitrinite particles is done with instrumental digitization which is carefully analyzed by a professional petrographer. Many statistical readings (40 or more) must be taken in order to determine the range of values of vi trinite populations and %Ro values. Vitrinite reflectance is a valuable method of assessing thermal maturity and is to determine for carbonate rocks or rocks con taining small values of vitrinite. Therefore, the analyst must be careful in statistically comparing all data avail able before 7.Ro values are assigned. %Ro value must range from .35 to 1.50 to be within the mature liquid hydrocar bon generation window. The discussion of laboratory re sults is included in the interpretation section of this text o Thermal Alteration Index ('TAI') The thermal alteration is the other mode of estab lishing thermal maturity in rock units. It is a measure ment of cuticular kerogen coloration and spore-pollen content- color of plant cuticle fragments and spore- pollen can be used to determine the degree of thermal maturity which a rock unit has undergone during its geo logic history. The index is evaluated on a scale of 1 to 5, primarily based upon cuticle and secondarily on spore- pollen coloration. The range is yellowish-green and yellow (1 ), orange (2), light brown (3), dark brown to gray (4) and black (5). A range between 2 to 3 falls within the liquid hydrocarbon generating window represented by Figure 14. The compiled laboratory results for TOC, °/oRo, and TAI appear as Table I (South Bilk Creek Range) and Table II (Southeast Pine Forest Range). t n T C O figure !4. Geothermal Diagenetic Criteria (after Geochem Loboratoriee, i980 > 61 TABLE I SUMMARY OF LABORATORY ANALYSTS RFSttttc; SOUTH BILK CREEK RANGE, HUMBOLDT COUNTY, NEVADA SAMPLE NUMBER AGE LITHOLOGY TOC 7oRO TAI PPM BCPL-1 Permian Limestone Barren Barren __ BCPL-2 Barren Permian Limestone 0,07 Barren BCPL-3 Contaminated Permian Limestone Barren Barren __ BCPL-4 Permian Barren Limestone Barren Barren Barren BCPL-5 Permian Limestone Barren BCPL Barren Barren -6 Permian Limestone Barren Barren BCPL-7 Barren Permian Limestone Barren Barren BCTS-8 Barren Triassic Shale Barren Barren Barren — —, BCTS-9 Triassic Shale 0.24 Barren 3.2/3.5 BCPL-10 Permian Limestone BCPL-11 0.12 2.57 Barren Permian Limestone 0.04 2.75 BCPL-12 3.5/4.0 Permian Limestone 0.06 Barren 3.7/4.0 BCPL-13 Permian Limestone 0.05 3.17 3.7/4.0 BCPL-14 Permian Limestone Barren Barren Barren BCTS-15 Triassic Shale 0 ,21 4.62 a. «. BCTS-16 3.5/5.0 Triassic Shale 1,52 5.27 3.7/4.0 30 BCTS-17 Triassic Shale 0.27 3.70 BCTS-18 3.5/3.7 Triassic Shale 2 .2 1 4.81 3.7/4.0 BCTS-19 50 Triassic Shale 3.46 4.50 4.0/5.0 30 BCTS-20 Triassic Shale 0.48 3.98 4.0/5.0 30 BCTS-21 Triassic Shale 0.64 1.81 4.0/5.0 BCTS-22 20 Triassic Shale 0.49 Barren Barren m m n n 62 TABLE II SUMMARY OF LABORATORY ANALYSIS RESULTS SOUTHEAST PINE FOREST RANGE, HUMBOLDT COUNTY, NEVADA SAMPLE NUMBER AGE LITHOLOGY TOC %R0 TAI PPM PFPL-1 Permian Limestone 0.05 Barren B arren PFPL-2 Permian Limestone 0.16 4.13 5.0 PFPL-3 Permian Limestone 0.18 Barren 5.0 PFPL-4 Permian Limestone 0.12 Barren 5.0 PFPL-5 Permian Limestone 0.09 Barren 3.7 PFPL-6 Permian Limestone 0.14 Barren 5.0 PFPL-7 Permian Limestone 0.10 Barren 5.0 PFPL- 8 Permian Limestone 0.08 Barren 5.0 PFPL-9 Permian Limestone 0.08 Barren 5.0 PFPS-10 Permian Shale 0.29 5.38 5.0 PFPS-11 Permian Shale 0.31 6.27 5.0 PFPS-12 Permian Shale Barren Barren Barren PFPS-13 Permian Shale 0.05 Barren 5.0 PFTS-14 Triassic Shale 0.03 5.96 Barren PFTS-15 Triassic Shale 0.07 6.82 Barren PFTS-16 Triassic Shale 0.16 6.09 5 .0 PFTL-17 Triassic Limestone 0.12 Barren 5.0 PFPL-18 Permian Limestone Barren Barren B arren __ PFPL-19 Permian Limestone 0.02 Barren Barren PFPL-20 Permian Limestone Barren Barren Barren PFPL-21 Permian Limestone Barren Barren Barren PFPL-22 Permian Limestone 0.09 Barren Barren PFTS-23 Triassic Shale 0 .11 Barren Barren 63 LABORATORY ANALYSIS DISCUSSION The most important factor in the origin of petroleum is the history of the source rock. This is a synthesis of: 1. The original organic content of the source rock. 2. Depth of burialo 3. The degree of thermal maturation of the organic compounds present due to time and temperature. The wide range of organic content of sediments is attributed to three factors (J. M. Hunt, 1979): 1. The rate of organic deposition versus mineral deposition, 2. The level of biologic activity, 3. The availability of oxygen. Organic matter source material is derived from com binations of marine and terrestrial organic compounds. In the southeast Pine Forest Range and south Bilk Creek Range, the limestone and shale units contain marine organic source material. The geochemical interpretation of the carbonate and shale sequences is constrained by the effect of sur face weathering on the sampled outcrops. Leythaeuser (1973) illustrated a maximum loss of 25% total organic carbon from samples tested in the Upper Cretaceous Mancos Shale of Utah. Similarly, Clayton and Swetland (1977) obtained readings from near surface cored samples (0.0 - 1,2 meters in depth) which contained 60% less organic carbon than the remainder of the core (1.2 - 64 7oO meters in depth). The core was obtained from the Permian Phosphoria Formation of northwestern Utah (S. 25, T„ IN., R. 9 W D)= Clayton and Swetland also analyzed the Mitten Member of the Upper Cretaceous Pierre Shale of Colorado (S. 1, T n IN., R. 71 W.), which showed no effect on total organic carbon content due to weathering. Conclusions drawn by Clayton and Swetland were that the magnitude of weathering-induced compositional changes in sedimentary organic matter is variable and depends upon a variety of physical and chemical factors, including: 1. Mineralogy. 2. Type and volume of porosity and permeability of the source rock. 3- Type of organic matter present. 4. The stage of thermal maturation of the organic matter present. 5. The climate of the area. 6 . The amount and character of biological activity in the source rock. 7. The tectonic history of the area. 8 . The attitude of the source bed. The total organic carbon (TOC) content of a source rock is measured experimentally by high-temperature com bustion of pulverized rock samples with oxygen. This process follows the removal of carbonate minerals with HC1. The resultant amount of CO2 formed is measured and compared to the total volume weight of rock oxidized. By ratio of these two measurements, the weight percent of organic carbon is obtained. The quantity of organic matter which becomes incorporated into a sedimentary source rock is defined by a number of variables (Dow, 1976) lo Sedimentary rate. 2. Organic productivity. 3. Depositional environment. 4. Post-depositional environment, or 5. Diagenetic history (cycle) of the sediments, defined by: * a. Diagenesis, the process of biological, chemical and physical alteration of the organic debris prior to the temperature effect. b 0 Catagenesis, the process by which organic material is altered due to the effect of increasing temperature (50°C to 200°C = 122°F to 392°F),and Co Metamorphism (metagenesis) the process by which all organic material is ultimately converted to methane or graphite due to increased temperature (greater than 200°C) and pressure. According to J. M. Hunt (1979), the largest quantity of petroleum hydrocarbons is formed from organic matter heated m the earth to temperatures between 60°C to 150°C (140°F to 302°F). ^r^^r^nite reflectance values are also altered due to the high degree of oxidation of surface samples (com bined with possible time and temperature diagenetic changes) Oxidized vitrinite reflectance values indicate that the sediments have either been exposed to subsurface meteoric waters in the past, partially eroded by surface exposure, 66 or both. Time and temperature affects vitrinite reflec tance m that the resulting maturation of the sediments is analyzed over the entire diagenetic cycle of hydrocar bons present. Vitrinite reflectance values identify the zone of catagenesis within which the hydrocarbons are found, and are not an indication of the amount (ppm) of hydrocarbons present. The basic structure of vitrinite is clusters of condensed aromatic hydrocarbon rings which are linked into a chain-like structure and stacked upon each other. With an increase in thermal maturation, the clusters fuse into larger, condensed aromatic rangs which form ordered sheet-like structures. The increased develop ment of the sheets orientation and size results in a corresponding increased vitrinite reflectance value. The condensation and ordering of the aromatic rings also re sults in the release of hydrogen, which is utilized to form methane. Vitrinite reflectance values may be pri mary or recycled. Recycled vitrinite depicts more than one diagenetic cycle acting upon hydrocarbon generation (The sediments are subjected to more than one depositional cycle during geologic time). Subsequent erosion, oxida tion and surface weathering processes also contribute to the recycling of existing vitrinite. The southeast Pine Forest Range rock samples all contained 0.31/£ or less total organic carbon with a 67 corresponding vitrinite reflectance and thermal alteration index of 5.0 or greater. A 0.12% TOC reading is the mini mal accepted grade for carbonate rocks which are to be considered of potential hydrocarbon source value. The limestone sequences of the southeast Pine Forest Range have been subject to metamorphism at depths as evidenced by extensive marblization. Extensive fracturing and plas tic deformation of the carbonate sequences has also occured. These processes have been accompanied by subsequent ground- water solutioning of the sediments with noticeable second ary cementation and recrystallization of the rock matrix along fracture surfaces. Although samples PFPS-10, PFPS- 1 1 and PFTS-16 were within the TOC liquid hydrocarbon generating range, the corresponding shale horizons were also apparently subject to high alteration and metamorphism at depth. The ob tained vitrinite reflectance values are therefore indica tive of a recycled rather than primary nature. Other values (TAI, TOC) obtained are also outside of the ac ceptable range of values assigned to diagenetic criteria liquid hydrocarbon generation. The entire strati graphic sequence has apparently been subjected to more than one diagenetic cycle acting upon hydrocarbon gen eration. The south Bilk Creek Range Permian limestone re vealed either barren or low readings of total organic carbono Therefore, the CaCC>3 sediments fell below the minimum acceptable range for assigned geothermal dia- genetic criteria for hydrocarbon generation. The south Bilk Creek Range argillaceous sediment samples revealed a substantial set of total organic carbon values within the dark gray shale horizons (Late Middle Triassic Quinn River Formation). The samples BCTS-16, BCTS-18, BCTS-19 and BCTS-21 revealed TOC values ranging from 0.64% to 3.46%. The TOC minimum diagenetic criteria for liquid hydrocarbon generation within shale is 0,50%. Associated thermal alteration index values were high (3.2 to 5 o0) and were ranging from dark brown to black in color. A range between 2.0 to 3.0 falls within the liquid hydrocarbon generating window on Figure 14. The relatively high TAI readings may suggest the presence of recycled vitrinite. According to Barker (1980): Both physical and chemical characteristics of kerogen reflect the combined effects of time and temperature and indicate thermal maturity. With increasing time and temperature kerogen color intensifies and darkens; vitrinite increases; palynomorph translucency decreases; thermal sta bility (as indicated by pyrolysis) increases; and the elemental composition of kerogen shows a progressive increase in percent carbon," This is evidenced by the extensive primary and secondary fracturing of the south Bilk Creek Range sediments with subsequent migration of ground water solutions along fractured surfaces at depth (resulting in the geochemi cal oxidation of the sediments). Widespread surface exposure and related physical and chemical weathering processes may have also acted upon existing vitrinite populations within the sediments. 70 SUMMARY AND CONCLUSIONS Rock sequences containing limestones, shales, and sandstones comprise a thick Paleozoic section which underlie most of Nevada. The potential for petroleum exploration within these sediments is confined to the discovery of struc tural or stratigraphic traps beneath the valley floors of the Basin and Range physiographic province. During the Paleozoic deposition of the sediments oc curred beneath the ocean which covered most of the state of Nevada, with only temporary periods of withdrawal. The en vironment of deposition transcended with little change from the Paleozoic into the Mesozoic era in Nevada. In the eu- geosynclmal accretionary terrain of western Nevada, the volcanic activity and resulting deposition of pyroclastics exceeded the normal deposition rate of marine sediments. During the middle of the Mesozoic era, the oceans retreated and the land of western Nevada became elevated as volcanic activity increased. The Quinn River Crossing area is covered with volcanic deposits of Tertiary Age and alluvial deposits of Quaternary Age. These deposits occur throughout the basins and ranges of Nevada and cover the older potentially petroliferous beds. The widespread degree of tectonic activity (which resulted in tilting and local deformation of the rocks) may have formed structural and stratigraphic traps in which the hydrocarbons could accumulate. However, as exhibited in the southeast Pine Forest Range, an excessive degree of deformation may 71 shatter a structural trap and destroy the possibility of hydrocarbon accumulation0 The surface expression of the late Middle Triassic Quinn River Formation of the south Bilk Creek Range does not reveal evidence of deformation. Therefore, the potential for hydrocarbon generation may still exist within the for mation. The dark gray shale horizons within the formation contain sufficient amounts of organic carbon to be classi fied as a latent source rock. This is a source bed that exists but is as yet partially concealed or undiscovered. This term usually refers to unexplored basins or deep por tions of developed basins. In order to ascertain the eco nomic significance of the Quinn River Formation as a poten tial source rock, future subsurface stratigraphic test drilling, and related geophysical and geochemical operations are recommended. The operations should be directed at de lineating the areal extent, reservoir properties and pro ductivity of the source bed horizon; as well as investi gating the potential for developing stratigraphic or struc tural traps which may exist at depth within the basin. investigations should focus on extending the degree of correlation of other existing Triassic shale hori zons in northwest Nevada with the Quinn River Formation. A prime target for investigation is the Prida Formation which is exposed in the East Range of Pershing County, Nevada. REFERENCES Albers, J D P., R. J 0 Roberts, N. J 0 Siberling, and J. H. Stewart, 1964, Generalized Stratigraphic Correla- Charts for Nevada, in Mineral and Water Re sources of Nevada: Nevada Bur. Mines Bull. 65 (U. S. 88th Congo, 2nd sess. Senate Document 87), table 1 , p. 14-15. Barker, C„, 1980, Organic Geochemistry in Petroleum Exploration: Tulsa, AAPG Education Series #10, 159 pp0 Beede, J 0 W D, 1924, Species of the Genus Schwagerina and Their Stratigraphic Significance: Texas Bur0 of Econ. Geol., The Univ. of Texas, Austin, 96 pp. Beus, S. S., 1968, Paleozoic Stratigraphy of Samaria Mountain, Idaho-Utah: Amer. Assoc. Petrol. Geol. Bull., vol. 52, no. 5, p. 782-808, illus. Bissell, H. J., 1962, Pennsylvanian and Permian Rocks of Cordilleran Area, in Symposium on the Pennsyl vanian System in the United States: Am. Assoc. Petrol. Geol., Tulsa, p. 188-263. ------H. J., 1973, Permian-Triassic Boundary in the Eastern Great Basin Area, in the Permian and Tri- assic Systems and Their Mutual Boundary: Canadian Soc. of Petrol. Geol., p. 318-344. Cassity, P„ E 0 and R„ L„ Langenheim, Jr0, 1966, Pennsylvanian and Permian Fusulinids of the Bird Spring Group from Arrow Canyon, Clark County, Nevada: Jour0 of Paleo., v o40, p 0931-968. Chilingar, G 0 V., R 0 W 0 Mannon and H„ H 0 Riecke III, 1972, Oil and £as production from carbonate rocks Elsevier, New York, p 0 35-36, 41. Clark, L. D., R. W. Imlay, V. E. McMath, and N. L. Siberling, 1962, Angular Unconformity between Mesozoic and Paleozoic Rocks in the Northern Sierra Nevada, California, in Geol. Surv. Res. 1962: U. S. Geol. Surv. Prof. Paper 450-B, Art. 6 , p. B15-B19. Clayton, J. L. and P. J 0 Swetland, 1978, Subaerial Weathering of Sedimentary Organic Matter: Jour. Geochemica and Cosmochimica, v. 42, Apr., p. 305-311. Collins, A„ G 0, 1975, Geochemistry of oilfield waters: Elsevier, New York, p D 293-305. Collinson, J. W., 1963, Separation of Conodonts by Heavy Liquids in Illinois State Geol. Circular 343, p. 14-15. Connan, J., K. LeTran and B. Van Der Weide, 1975, Alteration of Petroleum in Reservoirs, 9th World Petrol. Cong. Proc. 2 , p. 171-178. Coogan, A. H., 1960, Stratigraphy and Palaeontology of the Permian Nosoni and Dekkas formations (Bolli- bokka Group): Univ. of Calif. Pubis. Geol. Sci0, v. 36, no. 5, p. 243-316. Cooper, G. A., 1957, Permian Brachiopods from Central Oregon: Smithsonian Miscellaneous Collections, v„ 134, no. 12, 79 pp. Cordell, R. J., 1972, Depths of Oil Origin and Primary Migration: A Review and Critique, in Amer. Assoc, of Petrol. Geol. Bull. 56, no. 10 (p. 2029-2067). Crockford, M. B. B., and P. S. Warren, 1935, The Cache Creek Series of British Columbia: Trans. Roy. Soc. Canada, 3rd ser., v. 29, sec. 4 , p. 149-161, 1 fig. De Sitter, L. U., 1956, Structural geology. McGraw-Hill, New York, p. 398-400. Diller, J., 1908, Geology of the Taylorville Region, California: U. S. Geol. Surv. Bull. 353. Dott, R. H., and M. J. Reynolds, 1969, Sourcebook for petroleum geology: Tulsa, Amer. Assoc, of Petrol. Geol., 471 pp. Druce, E. C., 1973, Upper Paleozoic and Triassic Conodont Distribution and the Recognition of Biofacies, in Conodont Paleozoology: Geol. Soc. of America, Special Paper 141, p. 217-219. 75 Dunbar, C„ 0 o, and J. Rogers, 1957, Principles of stratigr-aphy, John Wiley and Sons, Inc., New York, p. 88-890 ------, C. 0 o, et al0, 1960, Correlation of the Permian Formations of North America: Geol. Soco of America Bull., v. 72, p. 1763-1806. Eardley, A. J D, 1947, Paleozoic Cordilleran Geosyn cline and Related Orogeny: Jour, of Geol., v. 55, p. 309-342. ------—» A. J., 1964, Structural geology of North America, Harper Publishing Company, New York, p. 47-49. Easton, W. H., 1960a, Permian Corals from Nevada and California: Jour. Paleo., v. 34, p. 570-583. — ■ 3 1960b, Invertebrate palaeontology. Harper and Row, New York, 701 pp. Epstein, A. G., J. B. Epstein and L. D. Harris, 1977, Conodont Color Alteration - An Index to Organic Metamorphism: U. S. Geol. Surv., Prof. Paper 431, 128 pp. Erdman, J. G., and D. A. Morris, 1974, Geochemical Correlation of Petroleum, in Advances in Petro leum Geochemistry, Amer. Assoc, of Petrol. Geol. Bull. 58, no. 11, Part 1, p. 2326-2337. Fabiano, E. B., and N. W. Peddie, 1974, Aeromagnetic Map of Nevada, Vya Sheet: Nevada Bur. Mines Map 48. 76 Ferguson, H. G., S 0 W. Muller, and R 0 J. Roberts, 1951, Geologic Map of the Winnemucca Quadrangle, Nevada: U 0 S. Geol0 Surv. Geola Quad. Map GQ-1 1 . Fisher, W. L„, and J. E, Sorauf, 1962, Correlation Chart of the Permian Formations of North America - Dis cussion of the Grand Canyon Section: Geol. Soc. Am° Bull., v. 73, no. 5, p. 649-652. Garside, L. J., B, S. Weimer, and I 0 A. Lutsey, 1977, Oil and Gas Developments in Nevada, Nev. Bur. of Mines Report no. 29, 32 p. Geochem Laboratories, Inc., 1980, Source Rock Evaluation Reference Manual: Geochem Graphics and Reproduction Division, Houston, 79 pp. Gianella, V. P OJ and E. R. Larson, 1960, Marine Permian at Black Rock Nevada (abstr.): Geol. Soc. of American Bull., v. 71, p. 2061. Grant, R„ E., and F. G. Stehli, 1969, Brachiopods in the Permian Reef Environment of West Texas: Proceedings of the North American Paleo. Convention, September, 1969, Part J, p. 1444-1481, 22 figs. Hazzard, J. C., 1938, Paleozoic Section in the Providence Mountains, San Bernardino County, California (abstr.), Geol. Soc. of Am., Pr., p. 240-241. Hedberg, H„ D., 1964, Geologic Aspects of Origin of Petroleum, in Amer. Assoc, of Petrol. Geol. Bull. 48, no. 1 1 , p. 1755-1803. Hoare, R 0 D 0, 1963, Permian Fusulinids from the Sunflower Reservoir Area of Northern Nevada: Jour. Paleo., Vo 37, no. 6 , p. 1143-1149. ------R. D., 1964, Permian Corals from Northern Nevada: Jour. Paleo., v. 38, no. 3, p. 496-504. Howe, D, M., 1975, Correlation of the Fauna from the Middle Permian Section at Black Rock, Northwestern Nevada: Masters Thesis, Mackay School of Mines, Univ. of Nevada. Hunt, J. M„, 1979, Petroleum geochemistry and geology: W. H„ Freeman and Company, San Francisco, 617 pp. Irwin, W. P., and S. P. Galanis, Jr., 1976, Map Showing Limestone and Selected Fossil Localities in the Klamath Mountains Province, California and Oregon: U. S. Geolc Surv0 Misc. Field Studies Map MF-749. ------j W. P., 1977, Review of Paleozoic Rocks of the Klamath Mountains, in Stewart, J. H. Stevens, C. H 0, and Fritsche, A. E., eds. Paleozoic Paleogeography of the Western United States: Pacific Section, Soc. Econa Paleontol. and Mineral., p. 441-454. Kay, G. M., 1960, Paleozoic Continental Margin in Central Nevada, Western United States: 21st. Internet. Geol. Cong., Copenhagen 1960, Rept. 12, p. 94-103. ------— , G. M 0, and E, H 0 Colbert, 1965, Stratigraphy and life history, John Wiley and Sons, Inc., New York, Po 292-307, 468. Ketner, K. B,, 1967, West Coast Region, in McKee, E.D., in McKee, E. D., and S. S. Oriel, Paleotectonic Investigations of the Permian System in the United States: U. S„ Geol„ Surv. Prof. Paper 515K, Po 229-238. ------K. B., and B 0 R. Wardlaw, 1981, Permian and Triassic Rocks Near Quinn River Crossing, Humboldt County Nevada, in Geology, v. 9, March, p. 123-126. Kindle, E 0 M„, 1926, The Occurence of the Genus Leptodus in the Anthrocolithic Fauna of British Columbia: Trans. Roy. Soc. Canada, 3d ser., v, 20, sec. 4. 1931, The Geology of the Glass Mountains, Texas, Part X: Descriptive Geology: Univ. of Texas Bull. 3038, 167 pp0, 15 pi., map. Knight, R. L., 1956, Permian Fusulinids from Nevada: Jour. Paleo., v. 30, p. 773-792, pis. 83-88. \ Krumbein, W. C., and L. L. Sloss, 1963, Stratigraphy and sedimentation, W. H. Freeman and Company, San Francisco, p. 119-125, 580. Landes, K. K. , 1951, Petroleum geology, John Wiley and Sons, Inc., New York, p. 90, 205, 286-290. Langenheim, R., and E. R. Larson, 1973, Correlation of Great Basin-Stratigraphic Units: Nevada Bur. of Mines Bull. 72, 36 pp. Leythaeuser, D., 1973, Effects of Weathering on Organic Matter in Shales, Geochemica et Cosmochemica, Acta 37, p. 113-120. » E. R., 1928, The geology of petroleum and natural £as, V. Dan Nostrand Company, New York, p 0 103. Link, T. A., 1950, Theory of Transgressive and Regressive Reef (Bioherm) Development and Origin of Oil: Bull. Am. Assoc. Petrol. Geol., v. 34, p„ 263-294. Lintz, J., Jr., 1957a, What Does Nevada's Oil Promise for the Future? Oil and Gas Jour., v. 55, n. 13, pp. 243-251. ------, J., Jr., 1957b, Nevada Oil and Gas Drilling Data, 1906-1953, Nev. Bur. Mines Bull. 52, 80 p. Longwell, C. R., and C. 0. Dunbar, 1936, Problems of Pennsylvanian-Permian Boundary in Southern Nevada: Bull. Amer. Assoc. Petrol. Geol., v. 20, no. 9, p. 1198-1207, 6 figs. MacMillan, J. R., 1972, Late Paleozoic and Mesozoic Tectonic Events in West Central Nevada: Unpub. Ph.D. Dissertation, Northwestern Univ., 146 pp. Matthews, R. K., Dynamic Stratigraphy: An introduction to sedimentation and stratigraphy. Prentice-Hall, Englewood Cliffs, N. J., p 0 182. McCaslin, J. C., 1979, Operators Continue to Stake Nevada Wildcats: Oil and Gas Jour., v. 77, no. 4, p. 79. McGugan, A., H. Roessingh and W. Danner, 1964, Permian in Geol. History of Western Canada: Alberta Soc. of Petrol. Geol., p. 103-111. McKee, E 0 D„, et al., 1959, Paleotectonic Maps of the Triassic System: U. S. Geol. Surv. Misc. Geol0 Investo, Map 1-300. ------, Eo D 0, and S. S„ Oriel, 1967, Paleotectonic Maps of the Permian System: U. S. Geol0 Surv. Misc. Geol. Inv. Map 1-450, 164 pp0 Meek, F. B., 1877, Paleontology: U. S. Geol. Expl. 40th Par. Rept., v. 4, p. 121-123, pi. 10. Muller, S. W . , 1949, Sedimentary Facies and Geologic Structures in the Basin and Range Province, in Longwell, C. R., chm., Sedimentary Facies in Geo logic History (Symposium): Geol. Soc. America Mem. 39, 171 pp. Murchison, R. I., E. de Verneuil, and A. von Keyserling, 1845, The Geology of Russia in Europe and the Ural Mountains: London, John Murray, 2 volumes. Newman, W. J., 1978, Nevada: in Oil and Gas Activity Reports of States and Official Observers for 1977: Oil and Gas Compact Bull., v. 37, no. 1, p. 33. Nicholson, A. H„, 1897, The ancient life-history of the earth, D, Appleton and Company, New York, p. 193, 203-204. Nolan, T. B., 1943, The Basin and Range Province in Utah, Nevada, and California, U. S. Geol. Surv. Prof. Paper 197-D. Pettijohn, F. J„, 1975, Sedimentary rocks. Harper and Row, San Francisco, 628 pp. Pirson, S. J., 1950, Elements of oil reservoir engineering, McGraw-Hill: New York, p. 76-79. Rasetti, F., 1965, Photography of Fossils in Handbook of paleontological techniques: W. H. Freeman, San Francisco, pp. 423-4290 Reineck, H. E., and I. B. Singh, 1973, Depositional sedimentary environments. Springer-Verlag, New York, 439 pp., 579 fig. Reside, J. B., Jr., et al., 1957, Correlation of the Triassic Formations of North America Exclusive of Canada: Geol. Soc. Am. Bull., v. 68, no. 11, p. 1451-1514. Rich, M., 1961, Stratigraphic Section and Fusulinids of the Bird Spring Formation Near Lee Canyon, Clark County, Nevada: Jour, of Paleo., v. 35, no. 6 , p. 1159-1180. Roberts, R. J., P. E. Hotz, J. Gilluly and H. G. Ferguson, 1958, Paleozoic Rocks of North-Central Nevada: Am. Assoc. Petrol. Geol. Bull., v. 42, no. 12, p. 2813- 2857. ------_, R. J., M. D. Crittenden, Jr., E. W. Tooker, H. T. Morris, R. K. Hose, and T. M. Cheney, 1965, Pennsylvanian and Permian Basins in Northwestern Utah, Northeastern Nevada, and South-Central Idaho: Am. Assoc. Petrol. Geol. Bull., v. 49, no. 11, p. 1926-1956. 82 Rogers, J. J. W., B 0 C. Burchfiel, E 0 W. Abbott, Jo K. Anepohl, A. H 0 Ewing, P 0 J 0 Hoehnken, Jo M. Novitsky-Evans, and S. C. Talukdar, 1974, Paleozoic and Lower Mesozoic Volcanism and Continental Growth in the Western United States: Geol, Soc. America Bull,, v 0 85, p. 1913-1924, Ross, C 0 A OJ 1963, Standard Wolfcampian Series (Permian), Glass Mountains, Texas: Geol. Soc. of Amer. Memoir, v. 88, 205 pp., 1 1 figs., 29 pi. Rountree, R e, 1978, Nevada Developing Its Own Robust Oil Industry: Western Oil Reporter, v 0 35, no. 4, p. 76-77. Sherlock, R 0 L., 1948, The Permo-Triassic Formations, A World Review: Hutchinson's Sci. and Tech. Pub., 367 pp. Silberling, N. J., 1962, Stratigraphic Distribution of Middle Triassic Ammonites at Fossil Hill, Humboldt Range, Nevada, in Jour, of Paleontology, v. 36, no. 1, p. 153-160. ______» N. J., and R. J. Roberts, 1962, Pre-Tertiary Stratigraphy and Structure of Northwestern Nevada: Geol. Soc. Am. Spec. Paper 72. ______> N. J., and E„ T. Tozer, 1968, Biostratigraphic Classification of the Marine Triassic in North America, Geol. Soc. Am. Spec. Paper 110, 63 p. ------3 N. J„, 1973, Geologic Events During Permian- Triassic Time Along the Pacific Margin of the United States, in the Permian and Triassic Systems and Their Mutual Boundary: Canadian Soc„ of Petrol. Geol., p. 345-362, 1 pi. Sinclair, W. C., 1962, Ground-Water Resources of Pine Forest Valley, Humboldt County, Nevada: Nev. Dept, of Conso and Nat. Res., Ground-Water Resources Reconnaissances Series Rept. 4, January, 23 pp0 Skinner, J. W., and G 0 L. Wilde, 1965, Permian Biostrati graphy and Fusulinid Faunas of the Shasta Lake Area, Northern California: Paleon. Contr. Univ„ Kanso, Protozoa, art. t, p. 1-98. ------J. W. and G. L. Wilde, 1966, Permian Fusulinids from Northwestern Nevada, in Permian Fusulinids from Pacific Northwest and Alaska: Paleo. Contr. Univ. Kans., Paper 4, p. 1-10, 8 pl0 Smith, J„ G., 1966, Petrology of the Southern Pine Forest Range, Humboldt County, Nevada: PhD Dissertation, Stanford University. ------J. G., 1973, Geologic Map of the Duffer Peak Quadrangle, U. S. Geol. Surv0 Misc. Geol. Investiga tions Map 1-606. Smith, J. P., 1914, The Middle Triassic Marine Inverte brate Faunas of North America: U. S. Geol. Surv. Prof. Paper 83, 254 pp. 84 ------J. P., 1927, Upper Triassic Marine Invertebrate Faunas of North America: U. S. Geol. Surv. Prof. Paper 141, Po 67-70. Speed, R. C., 1971, Permo-Triassic Margin Tectonics in Western Nevada: Geol. Soc. Am., Abstr. v. 3, no. 2 , p. 199. ------» Ro C., 1977, Paleozoic Paleogeography of the Western United States: Pacific Coast Paleogeography Symposium, Bakersfield, p. 325-336. ------, R. C., 1978, Paleogeographic and Plate Tectonic Evolution of the Early Mesozoic Marine Province of the Western Great Basin, in Mesozoic Paleogeography of the Western United States: Pacific Coast Paleo geography Symposium 2 , p. 253-270. ------,} Ro C., 1979, Collided Paleozoic Microplate in the Western United States: Jour.‘of Geology, v. 87, no. 3, p. 279-292. Steele, G., 1959, Basin and Range Structure Reflects Paleo zoic Tectonics and Sedimentation (abs.): Am. Assoc. Petrol. Geol. Bull., v. 43, no. 5, p. 1105. Stehli, F. G., 1957, Possible Permian Climatic Zonation and Its Implications, Amer. Jour, of Science, v. 255, Po 607-618. ------, F. G., 1973, Review of Paleoclimate and Continen tal Drift: Earth Science Review, v. 9, n o 0 1, p. 1-18. anrfwfmuWfr 85 Stevens, C. H., 1977, Permian Depositional Provinces and Tectonics, Western United States, in Paleozoic Paleogeography of the Western United States (Pacific Coast Paleogeography Symposium I), Los Angeles, California, p. 113-135. Tasch, P., 1973, Paleobiology of the invertebrates. John Wiley and Sons, Inc., New York, p 0 763-768. Thomas, E 0, 1972, Biostratigraphy of the Bilk Limestone (Permian), Northwestern Nevada: Masters Thesis, Western Washington State. Thompson, M. L„, and J. C. Hazzard, 1946, Permian Fusu- linids of Southern California, in Thompson, M 0 L., H° Eo Wheeler and J. C. Hazzard, Permian Fusulinids of California: Geol. Soc. Amer. Memoir 17, p. 37-53. ------M. L., and H„ E. Wheeler, 1946, Permian Fusu linids of Northern California, in Thompson, M. L., H. E, Wheeler and J. C. Hazzard, Permian Fusulinids of California: Geol. Soc. Amer. Memoir 17, p. 21-36. Tissot, B. P 0, et al, 1974, Influence of Nature and Diagenesis of Organic Matter in Formation of Petro leum, in Amer. Assoc, of Petrol. Geol. Bull. 58, no. 3, p. 499-506. ------.3 B. P., and D. H. Welte, 1978, Petroleum forma tion and occurrence: Springer-Verlag, New York, 538 pp. 86 Wardlaw, B 0 R 0, and J. W. Collinson, 1979, Youngest Permian Conodont Faunas from the Great Basin and Rocky Moun tain Regions: Brigham Young Univ. Geol. Studies, v 0 26, pi. 3, p. 151-164o Warner, M. M., 1980, Southern Idaho, Northern Nevada, Southeastern Oregon - Prime Exploration Target: Oil and Gas Jour., May, p. 325-341. Welte, D. H., 1965, Relation Between Petroleum and Source Rock, in Amer. Assoc, of Petrol. Geol. Bull. 49, no. 12, p. 2246-2268. Willden, R., 1958, Cretaceous and Tertiary Orogeny in Jackson Mountains, Humboldt County, Nevada: Amer. i Assoc. Petrol. Geol. Bull., v. 42, p. 2378-2398. ______3 R o, 1961a, Major Westward Thrusting of Post- Middle Triassic Age In Northwestern Nevada: U. S. Geol. Surv. Prof. Paper 424-C, p. C-116-119. ______3 R «» 1961b, Preliminary Geologic Map of Humboldt County, Nevada: U. S. Geol. Surv. Mineral Inv. Map MF-236. ______3 R » 3 1963, General Geology of the Jackson Moun tains, Humboldt County, Nevada: U. S. Geol. Surv. Bull. 1141-D. ______, R ., 1964, Geology and Mineral Deposits of Humboldt County, Nevada: Nevada Bur. of Mines Bull. 59, 159 pp. 87 Wilson, E. C., 1967, Corals and Other Significant Fossils from the Upper Paleozoic McCloud Limestone, Northern California: California Univ. Berkeley, PhD0 Thesis, Wilson, J„ L„, 1975, Carbonate facies in geologic history, Springer-Verlag: New York, 471 pp., 183 fig, Wilson, M. D., 1981a, Petrographic Analysis of Samples from the East Pine Forest Range, Humboldt County, Nevada (for Sunmark Exploration Company): Denver, Colorado, Agat Consultants, Inc., 8 pp., 10 figs, ------.) M. D., 1981b, Petrographic Analysis of Samples from the South Bilk Creek Range, Humboldt County, Nevada (for Sunmark Exploration Company): Denver, Colorado, Agat Consultants, Inc., 8 pp., 12 figs, Yole, R., 1963, An Early Permian Fauna from Vancouver Island, British Columbia: Bull. Canadian Petrol. Geol., v. 1 1 , no. 2 , p. 138-149. APPENDIX I View of the South Bilk Creek Range View of the Southeast Pine Forest Range PLATE A View from the west of the South Bilk Creek Range. The limestone and shale units represented are believed to be allocthonous blocks with respect to the surround ing mountain ranges of the Quinn River Crossing area. A contact is drawn between the Permian and Triassic sequences of interest, which have been exposed as a result of tectonic processes during the Tertiary period. The contact on the left side of the picture depicts a canyon which is the division between the Permian lime stone sequence and the Triassic-Jurassic? sequence of volcanics. The measured section appears to be a system of structurally oriented imbricate thrust sheets. The strike of the beds is predominantly northeast, with a corresponding southeast direction of dip. PLATE A | ...... JiU.i-l.ULH., . -U,.l....J II IU IU U IJ.IJL IJ.JJJllllU W W i» M ^ ^ 91 PLATE B View from the east of the Southeast Pine Forest Range. The major contact between the Permian and Triassic units of interest occurs in a thrust breccia interval. The sequence is believed to be allocthon- ous with respect to other rock units exposed in the surrounding mountain ranges of the Quinn River Cross ing area. The strike of the* section is oriented basically parallel to the thrust fault contact. The strike direction is predominately to the northwest, with a corresponding direction of dip to the south west. The hade of the thrust fault approaches vert ical and the dip of the beds increases above the fault. As a result of the thrusting activity of indeterminate age, the beds are structurally oriented in a reclined axis position. gucttM » a< PLATE B * n n r r i t n r r r r ^ n m r t i nrn'iftrg APPENDIX II Fauna of the Upper Triassic Limestone Sequence of the Southeast Pine Forest Range -i lnirrf itirfTrrwi 94 PLATE C Arcestes (Proarcestes) carpenteri Smith after J. P„ Smith, 1927 Description. Form laterally compressed, with gently convex flanks and narrowly rounded venter, without shoulders; umbilicus narrow but not closed, with very gentle slope of the umbilical walls. Surface with four or five labiae per revolution. Septa moderately digitate. Arcestes_ carpenteri is considerably more com pressed than Arcestes pacificus (Hyatt and Smith) and Arcestes shastensis (Smith), it has a much greater resemblance to Arcestes antonii (Mojsisovics) but c^ ^ ers -*-n ^ts distinct labiae, not obsolete on the mature shell. Occurrence: Common in the Upper Triassic Hosselkus Limestone, at the upper horizon of the Tropites weHeri zone (Silberling, 1956), at the North Fork of Squaw Creek, 3 miles north of Kelly's ranch, Shasta County, California; also in the same horizon on Brock Mountain, between Squaw Creek and Pit River, Shasta County, California. First recorded occurrence in the Basin and Range physiographic province. 95 PLATE C (1) Side view of Arcestes (Proarcestes) carpenteri Smith. The diameter of this specimen is 65 mm. (2) Lateral view. (3) Suture pattern. UNMSM P-6217. PLATE C 97 PLATE D Epigondolella primitia Mosher An Upper Triassic conodont which ranges from late Karnian to early Norian in age. This species is located in the Upper Triassic limestone unit of the southeast Pine Forest Range. It occurs in the same horizon as the ammonoid Arcestes carpenteri. The scale shown is X 60. Electron microscope photograph courtesy of USGS, Denver, Colorado. APPENDIX III Analysis of Thin Sections Obtained from the South Bilk Creek Range and the Southeast Pine Forest Range Prepared by Agat Consultants of Denver, Colorado PETROGRAPHIC ANALYSIS OF SAMPLES FROM EAST PINE FOREST RANGE HUMBOLDT COUNTY, NEVADA FOR SUNMARK EXPLORATION COMPANY by AGAT Consultants, Inc. 1215-18th Street 260 Cable Building Denver, Colorado 80202 Telephone: (303) 825-4256 Michael D. Wilson Project Geologist September 1981 flQflT Consultants^ 101 DESCRIPTION OF SAMPI f <; PFPL-12 are\onded^by°ducth ^deformation " o e t H u f 5*0 '6 (°r ‘-ff?) whose 3rains micaceous argillite, finely crystalline m* grains consist dominantly of schist, along with esser L S c U m caceous schist, and dolomitic monocrystall?nrquartz echS te schisrenT Cr^ alline Quartzite, dolomite or dolomitic marble, and si iJic and'haltr6’ i°arsely crystalline quartz grain, with rounded euhedral n t i n f c V a - lc+ Yolcanics- One large has a deep embayment filled bv dninmif 1n®s lndlcating a volcanic source, difficult to determine whether I *h In ma?y fra9"*nts, it is different origin or represents 9ni1" of a ductile^deformation of Mo?t Por°sity has been destroyed by amounts of porosity may haJe beer^ost^^dn'l^-? roc^.fi:a9merits- Minor dolomite probably represents detrital g^i^'oT'JlpUc^t^oVdllita, and PFPL-18 textures o^strucLres^re^apilarent lmert0r't’ ]0r n,arbllr‘ No Primary S !S £ *Ir^ S :S !s s S s r!-‘’ "iinor amounts of ragged broSlsl ?X s , ’^ ! ^ h ^ f S e ^ ^ S ^ f ^ i byHfntense^eformationf''6 tW,nned’ ind,cati"9 tba sample has been affected PFJL-19 generations o^te^sectin^ca^ varies widely over short distance r ’ he f e of the calcite grains Twinning is common, especially in the coarser grains/6 UP t0 1,3 m Wlde* 102 produced by dissolution along fJactu?es in out^op? ar6 probab,y PFTS-14 quartz1 and^plagioclas^f 30t^s£?se ra?tase<^ ment• Fine sand-sized grains of quartz-chloMtf-mS covitf"wh^ch Crysfta^lne of potash feldspars finelv c r e t i n „r,L?h h WaS a wavy fabric* A few fragments VXZ& AtfS?''" Fn“e? rcr^ ? ,°:;r;« d0 ^@55a*SSf5u visible porosity ^present?* 6Xhlblt only a weak Preferred alignment. No PFTS-15 limestone!^ T?e Sandy or recrystallized angned!ansi?q^lynwatendtJ° 56 ^^ife^onga^ed I^ver^stangly11 t0 clay?) cut throunh tho^ca^]0* subPara1lel» hematitic streaks (stained represent impurities anri/I^ch^3 !el t0 the 9rain ali9nment and may calcite are cannon and n a y ^ d S c e T b ^ s b ^ n T ' 9rai"S °f c°ar5pr polyc^sJln^rgSaVL' an^^SUIl^icacloul^v^rHnefrcrystalline re aZfew'large'clusters ^ ^ o n ^ r o f h ^ f e 5^ weatheHng9I*a'nS> Wh1Ch pr0babl* rep?psent P^-te aUe^ed £ ™ S a c e D-187 TABLE 1 PETROGRAPHIC DATA FOR SAMPLES FROM OUTCROPS IN EAST PINE FOREST RANGE HUMBOLDT COUNTY. NEVADA Grain/Crystal Size Pore Size Cement Sample (in mm) Pore (in mm) Est Qtz Dolo Hem Cal Number Rock Type Sort Rnd Max Mean 1m . Max Mean _± - PFPL-12 alt. tuff VP A 3.5 0.14 ------A - - - - - VA PFPL-18 mar b . ? - - 0.36 0.12 - - - VA PFJL-19 marb.? - - 0.60 0.05 D 0.90 0.20 3-5 - - - P FT S -14 (1 ) schist? - - 0.30 0.03 - - - C VR PFTS-15 mar b . ? - - 0.30 0.02? - - - - - R VA Legend: grain - grainstone, Rock Type: sand - sandstone, dol - dolomite, wacke - wackestone, pack - packstone, marb - marble, mudst - mudstone, skel - skeletal, pel - peloid, intra ■• intraclast Sorting: VW - very well, W - well, M - moderate, P - poor, VP - very poor Rounding: W - well rounded, SR - subrounded, SA - subangular, A - angular Pore Type: D - dissolution , . „„ , Cement: VA - very abundant (>25%), A - abundant (10-25%), C - common (5-10%), R - rare (l-5«), VR - very rare (<1 ») PHOTOMICROGRAPHS FIGURE 1 Sample PFPL-12 a Volcanic auartz arain (white) surrounded by swirled masses of chlorite (dark), calcite, smectitic clays(?) Ind ragged Setriial grains in what may be a highly altered vitric tuff. Note the complete lack of visible porosity and very poor sorting. Plane light, 24X. B Finely crystalline quartzite and dolomite clasts in altered tuffaceous matrix and ductilely deformed schist fragments. The pink grains probably represent altered volcanic glass shards. Crossed polarizers, 24X. Sample PFPL-18 C. Finely crystalline recrystalized calcite or marble cut by a thin fracture along which minor granulation has occurred. Plane light, 24X. D. Close-up showing the alignment of elongate calcite grains and a f r a c ^ coarse calcite and exhibiting some granulation (right center oriented vertically). Plane light, 94X. m e PHOTOMICROGRAPHS FIGURE 2 Sample PFPL-19 A. Very finely crystalline marble, cut by several generations of calcite-fi1 led fractures or veins and a hematite fracture (oriented subvertically). The minor porosity is probably created by dissolution related to surface weathering. Plane light, 24X. B. A close-up showing the lack of strong grain orientation compared to Sample PFPL-18. Plane light, 94X. Sample PFTS-14 C. Finely crystalline, very low grade metasediment with grains of quartz and plagioclase floating in a very finely crystalline quartz-chlorite-muscovite schistose matrix. No visible porosity is present. Plane light, 24X. D. Close-up showing the alignment of muscovite in the schistose matrix surrounding the coarser silt. Crossed polarizers, 94X. [ a ] d ] 0 0.1 02 o 005 o i 0 05 1.0 f I ZEISS 1 1 Imm 1 I l"1m m m 94 X Mognification 375X Magnification 24 X Magnification AGAT CarauttanU 1U/ h X ' J t V J J jjJ s n 1 wt‘* | f e r jS l L - * < L jv^S VtA , jp l f j L lM M . ' i[iWn / f i l l I z v m W PHOTOMICROGRAPHS FIGURE 3 ■ J Sample PFTS-15 A. Slightly silty and sandy, very finely crystalline marble or extensively recrystallized limestone with an elongate cluster of hematitized pyrite(?) crystals. The lenticular shape of the grains is probably produced by shearing. Plane light, 24X. B. Close-up showing the lenticular shape of the coarser grains surrounded by much more finely crystalline calcite. These lenticular shapes are probably created by granulation and shearing. Plane light, 94X. 108 0 003 o i 0 0 3 10 o oi 02 ZEISS 1 I I"1"1 f » I1"" f I I"1* 375X Magnification 24 X Magnification 94 X Magnification flGRT CorauitanUJ luy D— 187-3 PETROGRAPHIC ANALYSIS OF SAMPLES FROM SOUTHERN BILK CREEK MOUNTAINS HUMBOLDT COUNTY, NEVADA FOR SUNMARK EXPLORATION COMPANY by AGAT Consultants, Inc. 1215-18th Street 260 Cable Building Denver, Colorado 80202 Telephone: (303) 825-4256 Michael D. Wilson Project Geologist September 1981 Ill DESCRIPTION OF SAMPLES BCPL-3 Skeletal grainstone completely cemented by finely crystalline calcite. Fossils are predominantly crinoid fragments, forams and pelecypod fragments. All shell material has been micritized except for the crinoid columnals which occur as single crystals. Ovoid and irregular-shaped micritic clasts of unknown origin also are common. Some may be peloids. All interparticle pores and shell chambers have been completely filled by finely crystalline calcite. Very minor porosity occurs along thin irregular fractures or is immediately adjacent to these fractures and both are almost certainly produced by surface weathering. The coarser calcite in the crinoid columnals and that which occurs as cement exhibit twinning, suggesting this sample was affected by intense physical deformation. Traces of fine silt-sized hematite are scattered throughout the sample. Several thin (0.04-0.07 mm) intersecting calcite-filied fractures are present. BCPL-7 Skeletal intraclast grainstone cemented completely by finely crystalline calcite. The major fossil types present are micritized forams, crinoid fragments and partially silicified pelecypod fragments. Rounded ovoid to irregular micritic intraclasts are the most common grain type. The latter are up to 2 mm in length and commonly a few contain small calcite-filied chambers and one contains a chamosite ooid. Some of these intraclasts may be micritized oolites. Present in very minor amounts are brachiopod(?) fragments and brachiopod spines. A few chamositic(?) oolites are present. The fossil debris is poorly sorted. No visible porosity is present. All interparticle and chamber pores have been filled by finely to coarsely crystalline calcite which exhibits twinning. The chalcedony which has replaced portions of pelecypods commonly projects overgrowths with micrite inclusions out into the adjacent fossils or cement. Intersecting calcite-filied fractures cut irregularly across the sample. Twinning occurs in the calcite, filling the fractures and making up the crinoid columnals. The pervasive twinning indicates this rock has been affected by extensive physical deformation. Traces of hematite stain are scattered irregularly through the sample and probably represent pyrite altered by surface weathering. BCPL-10 Silicified peloid packstone(?). Microcrystalline chert has very extensively replaced both grains and matrix. The only grains which seem to consistently resist replacement are single crystal crinoid columnals. Where replacement is minimal peloids are common and it is, thus, suspected that the micritic peloids and matrix were especially susceptable to silicification. One large pelecypod fragment occurs isolated in chert. Scattered fine silt-sized patches of micrite are scattered throughout the chert. 112 iHr'the'fSrSaofhrLo»rftfe Cher exh’bit m1nor ‘o abundant (10-30*) porosity gagged irregular pores up to 0.35 ms across. These pores represent dissolved carbonate remnants and very likely were removed bv dissolution due to outcrop weathering. The sample is cut by several ca 6 nf2 T S ?ith a" outer ?i"™9 of chert anS an Inner biing of H k ^ p o re s up ?o U S ™^ng. “ ,ClU b“ n dl' SS° ’ Ved leav1ng Sheet‘ BCPL-12 T h ^ o c ^ i 3!76^ Silicified fora'T>iniferal grainstone(?) or packstone(?). In?hfi!«I fragme"ts o^ginally present were dominantly forams along with uch lesser amounts of crinoids and pelecypod fragments. All the fossils have been micritized with the exception of the crinoid and pelecypod fragments. The outlines of the forams are delineated by the presence of "l?"'tlg,reT nts 1n bbe chert- A small amount of fine silt-to fine sand- sized dolomite is scattered irregularly through the sample. It is not possible to determine whether this sample was originally a packstone or grainstone. The presence of micritic calcite, within the chert between tossil remnants, suggests it may have been a packstone. Except for pores created by dissolution of calcite remnants at one edge of the sample, no visible porosity is present. These pores are almost certainly created by outcrop weathering. A few of these pores contain mud which is stained by iron oxides and was introduced by surface infiltration. BCPl-13 Fusulinid grainstone completely cemented by very fine crystalline calcite. Recognizable fossil fragments are dominantly whole fusulinids (up to 4 tim across) along with much lesser amounts of single-crystal crinoid fragments and pelecypod fragments. Small micritic fragments of unknown origin are common between the large fusulinid grains. They may represent broken fusulinid fragments. All the fusulinids are completely micritized. Sorting is very poor. A thin, clay-lined stylolite with an amplitude of 0.70 mm occurs at one edge of the slide.. Except for minor porosity present along fractures or in close association with fractures, no visible porosity is present. The pores which are present have probably been created by dissolution related to surface weathering. Numerous intersecting calcite-filied fractures up to 0.3 mm thick cut across the sample at diverse angles. Small amounts (about 1%) of coarse silt- to medium sand-sized dolomite rhombs are scattered irregularly throughout the sample. Twinning of the calcite in the fractures and crinoid fragments indicates the rock has been affected by physical deformation subsequent to implacement of the fracture fills. 113 BCTS-21 Sandy mudstone, rich in plagioclase and biotite. The coarse silt- and Mn+TflZerh9rr nS^C^"S1?t primarily of P^gioclase, quartz, altered 55ert and crystalline quartz-mica schist. Traces of S^acf^fe ?uscovlte and altered volcanic rock fragments are also hafo ^ a».Tiefbl0^!te ?aS 3 dlstinct yellow or olive color and may have been altered to chlorite. A few of the yellowish grains appear to be volcanic glass or mafic minerals altered to microcrystalline clay. The coarse grains are angular and have low sphericity'and float in a mass of highly micaceous mudstone containing numerous scattered ragged silt-sized patches of leucoxene. Ragged patches and streaks of silt- to sand-sized fragments of organic material are common throughout the sample. Wavy Tensing laminations are defined by variations in the content of silt, sand and organic fragments. In a few laminae,very fine sand-sized grains are abundant-and the clay matrix relatively uncomnon and, in these zones, the grains are welded tightly together by suturing and ductile grain deformation. No visible porosity is present. D-187 TABLE 1 PETROGRAPHIC DATA FOR SAMPLES FROM OUTCROPS IN SOUTHERN BILK CREEK MOUNTAINS HUMBOLDT COUNTY, NEVADA Graln/Crystal Size Pore Size Sample (In mm) Pore (In mm) Est Cement Number Rock Type Sort Rnd Max Mean Type Max Mean _L_ Qtz Oolo Hen} Cal BCPL-3 Intra.grain. M U 1.5 0.40 - - - - VR VA BCPL-7 skel. grain. P U 7.0 0.80 - - - - R - VR VA BCPL-10 slllc.pel.pack. M U 3.5 0.10 0 0.35 0.10 5 VA - - - BCPL-12 slllc.skel.pack. M W 3.0 0.40 0 0.90 0.15 1 VA R - - BCPL-13 skel.grain. VP W 4.0 0.30? 0? 0.90 0.07 1 - R VR VA BCTS-21 mudst. VP A 0.20 0.02? ------ L e g e n d : Rock Type: sand - sandstone, dol - dolomite, wacke - wackestone, pack - packstone, grain - grainstone, marb - marble, mudst - mudstone, skel - skeletal, pel - peloid, intra - Intraclast Sorting: VW - very well, U - well, M - moderate, P - poor, VP - very poor Rounding: U - well rounded, SR - subrounded, SA - subangular, A - angular Pore Type: D - dissolution Cement: VA - very abundant (>25 0, A - abundant (10-25%), C - common (5-10%), R - rare (1-5%), VR - very rare (<1%) PHOTOMICROGRAPHS FIGURE 1 Sample BCPL-3 A. Skeletal limestone with the interparticle pores completely filled by finely crystalline calcite. A vertically oriented calcite-filled fracture (0.07 mm thick) cuts across the sample (left). Fossil fragments include crinoid columnals and forams. Note the moderate sorting and variety of foram types. Plane light, 10X. B. A close-up showing a foram whose shell has been micritized and which is filled and surrounded by finely crystalline calcite cement. Plane light, 94X. Sample BCPL-7 C. Skeletal/intraclast grainstone completely cemented by finely crystalline calcite. The dominant fossil types include forams, crinoid columnals, partially silicified pelecypods and ovoid to irregular shaped micritic intraclasts, many of which are plugged by calcite. A silicified pelecypod fragment with overgrowths on the replacement chalcedony occurs at the bottom of the photo. Plane light, 10X. D. Micritized foram (center) along with crinoid fragments, and chamosite(?) oolites surrounded by finely crystalline calcite cement. Plane light, 24X. 115 LaJ CD 0 OS 10 o o i o z 0 o o s o i f I I""» | 1 jmn. 1 I ---U, ZEISS m m 375X Magnification 24 X Magnification 94 X Magnification ------flOflT Consult anti PHOTOMICROGRAPHS FIGURE 2 Sample BCPL-10 A. Highly silicified peloid packstone cut by a thin fracture whose central calcite fill has been partially removed. Plane light, 24X. B. A portion of the sample in which unreplaced calcite has been dissolved, probably by outcrop weathering. Plane light, 24X. Sample BCPL-12 C. An extensively silicified foraminiferal packstone. A variety of sizes and types of forams are present and a probable fusulinid occurs in the center of the photo. Plane light, 24X. D. Pores created by dissolution of calcite remnants and authigenic dolomite which probably are produced by dissolution related to surface weathering. Plane light, 24X. 117 E l EX] 0 01 02 0 _oos_____ 01 0 0 3 10 ZEISS 1 i : :i" 1 I l"m 1 i !">■» DO DlI 375 X Magnification 24 X Magnification 94 X Magnification v. ftGflT ComuManti ^ PHOTOMICROGRAPHS FIGURE 3 Sample BCPL-13 A. Poorly sorted, fusilinid grainstone with all interparticle pores plugged by finely crystalline calcite 2a cite m t ! f ± J yPOd f^ 9™ent and a ,ar9e si"9,e echinoid fragment aho ^ f p r e ^ t A alcite-filled fracture cuts across the sample from upper left to lower right. Plane light, loi. B' i2t“ s«t1n21«l2lt2am i i d !“7 ? unded b> much f,ner skeletal grainstone. Numerous intersecting calcite-filled fractures are present. Planegained light, 24X. Sample BCPL-21 c- ^ 1;{s!2unpa2;^ ? tfn nPe?e^n“ ripai r si? ^ :'j4 x :and and or9anic raatter content ,n a sandy ”udstdne- D- ? J ! drSr “PaSh0Wi?9 -I16 P?or sort'h9. abundant micaceous material, minor organic and opaque content (black) and angularity of grains. The yellow grain is probably an altered mafic mineral PUnTlight, B VI oa to Ql 02 oos 01 u c m m _J mm nr I mm HZ □ mm Z E IS S V. 24 X Magnification 94 X Magnification 375 X Magnification fKWT Consultants ^