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1982

Tertiary geology of the Muddy Creek basin Beaverhead County Montana

Dennis Gordon Dunlap The University of Montana

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i^'iANSFiELD L ib r a r y

U n i v e r s i t y o f Mo n t a n a Date : X 9 8 S

TERTIARY GEOLOGY OF THE MUDDY CREEK BASIN,

BEAVERHEAD COUNTY MONTANA

By

Dennis Gordon Dunlap

B.A., University of Montana, 1968

Presented in partial fulfillment

of the requirements for the degree of

Master of Science

University of Montana

1982

Approved by:

1

Chairman, Board of Examiners

n. Graduate School

Date UMI Number: EP37967

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ProQuest LLC. 789 East Eisenhower Parkway P.O. Box 1346 Ann Arbor, Ml 48106- 1346 ABSTRACT

Dunlap, Dennis Gordon, M.S., Fall 1982 Geology

Tertiary Geology of the Muddy Creek Basin, Beaverhead County, Montana

Director: Robert W. Fields

The Muddy Creek basin contains a well exposed, uninterrupted and structura lly uncomplicated sequence of eastward dipping early Oligocene, or s lig h tly older. Renova Formation sediments. Five lithofacies comprise a stratigraphie thickness of over 1000 meters. Aerial and stratigraphie distribution of these lithofacies indicates a center of lacustrine sediments flanked by fan-delta and alluvial fan deposits overlain at the north end of the basin by extrusive igneous rocks. Transitions between lithofacies are generally uniform and lateral intertonguing is minor.

Muddy Creek basin sediments were f ir s t preserved when the basin was inundated by rh y o litic debris flows, alluvium and ejecta. Lacustrine sediments appear early in the sequence and refle ct perennial, shallow water conditions. Alluvial fan deposits, laterally equivalent to and interbedded with lacustrine sediments, thicken and coarsen to the southeast and rapidly prograde across lacustrine deposits in the final stages of recorded Muddy Creek basin deposition.

Tertiary sediments in the Muddy Creek basin unconformably overlap Precambrian to Cretaceous rocks of the Medicine Lodge and Tendoy thrust plates and are bounded on the east and west by a series of normal faults that strike subparallel to the underlying thrust trends. Eastward t iltin g of the Tertiary beds is complicated by the apparent interrelationship of high and low angle segments of the East Muddy Creek Fault. Contacts between Tertiary and Paleozoic rocks on the west of the basin may reflect normal faulting and buried topography at the leading edge of the Medicine Lodge Thrust plate.

11 ACKNOWLEDGMENTS

Financial support for field work was provided by Gulf Oil Exploration and Production Company.

I thank the following individuals for their interest and participation

in this study:

-- Dr. Robert W. Fields who suggested the study area, served as committee chairman, and c ritic a lly analyzed the manuscript.

-- Dr. Robert M. Weidman, for discussion of structural complexities, serving on the committee, and for helpful comments on the manuscript.

— Dr. John P. Wehrenberg for discussion of various aspects of the project.

— Dr. Charles N. Miller, Jr., for aid in floral identification and interpretation.

— Dr. William J. Perry and Dr. Louis E. Rieg for discussion in the fie ld .

— Edward K. Vukelich for discussion in the field and for preparing drainage distribution maps of the area.

I especially thank:

— Dr. John D. Scott for serving on the committee, and for inspiring and encouraging my graduate work.

-- Alan R. Tabrum for invaluable discussion of all aspects of

Tertiary geology, help in the fie ld , expert guidance in the collection and identification of vertebrate fossils, and for critical analysis of the developing manuscript.

i i i -- My wife, Karen and mother, Irene Sage, for th e ir unfailing support and encouragement.

1 V TABLE OF CONTENTS

Page

ABSTRACT i i

ACKNOWLEDGMENTS ...... i i i

LIST OF TABLES AND PLATES...... v iii

LIST OF ILLUSTRATIONS...... ix

I. INTRODUCTION ...... 1

Muddy Creek Basin ...... 1

Purpose ...... 3

Methods ...... 3

Previous W o r k ...... 5

I I. STRUCTURE...... 7

Laramide Structure ...... 7

Tertiary Structure ...... 9

Intra-Basin Structure ...... 9

Basin Bounding F a u l t s ...... 12

East Muddy Creek Fault ...... 12

West Muddy Creek faults ...... 16

I I I . PALEONTOLOGY AND AGE DETERMINATION...... 19

Vertebrates ...... 19

Localities and Fauna ...... 19

Age Determination ...... 19

P la n ts ...... 19

Invertebrates ...... 20

V Page

IV. STRATIGRAPHY AND DEPOSITIONALENVIRONMENTS ...... 28

Coarse Tuffaceous Facies ...... 29

Description ...... 29

Interpretation ...... 32

Fine Tuffaceous Facies ...... 33

Description ...... 33

Interpretation ...... 34

Shale/Sand Facies ...... 36

Description ...... 36

Interpretation ...... 40

Sand/Conglomerate Facies ...... 43

Description ...... 43

Interpretation ...... 45

Volcanic Facies ...... 47

Description ...... 47

Interpretation ...... 48

Facies Relationships ...... 49

Depositional History ...... 53

V. REGIONAL CORRELATION AND COMPARISON ...... 57

Lithologie Correlation —Renova Formation .... 59

Tectonics, Climate, and Sedimentation ...... 61

REFERENCES...... 64

VI Page

APPENDIX...... 73

INTRODUCTION TO MEASURED SECTIONS ...... 73

KEY TO LITHOLOGY AND SEDIMENTARY STRUCTURE SYMBOLS . . . 75

ROCK CLASSIFICATION DIAGRAMS ...... 76

KEY TO ABBREVIATIONS...... 78

MEASURED SECTIONS - ILLUSTRATION AND DESCRIPTION.... 79

Section 1 79

Section 2 ...... 84

Section 3 ...... 93

Section 4 ...... 102

Section 5 ...... 108

Section 6 ...... 119

Section 7 ...... 121

Section 8 ...... 123

Section 9 ...... 126

Section 1 0 ...... 129

Section 1 1 ...... 132

Section 1 2 ...... 133

VI 1 LIST OF TABLES AMD PLATES

Table Page

1. Floral L is t ...... 21

2. Vertebrate Fauna! L i s t ...... 23

3. Summary of Lithofacies and Environments of Deposition ...... 50

Plate

1. Geologic map of the Muddy Creek basin area .... Pocket

VI 1 1 LIST OF ILLUSTRATIONS

Figure Page

1. Location map of Tertiary basins in southwestern Montana ...... 2

2. Generalized geologic map of the Muddy Creek basin area emphasizing Laramide structure ...... 8

3. Sketch map of the Muddy Creek basin area emphasizing Tertiary structure ...... 10

4. Unconformable contact between Paleozoic limestone and tilted Tertiary be ds ...... 11

5. Low angle fa u lt contact. East Muddy Creek Fault . . 14

6. Block diagram representing apparent high and low angle normal-fault geometry along the East Muddy Creek F a u lt ...... 15

7. Geologic cross section A-A" ...... 17

8. Geologic cross section B-B' ...... 17

9. Sketch map of Muddy Creek basin lithofacies distribution, stratigraphie section locations, and key fossil collecting localities ...... 27

10. Tuffaceous conglomerate with lenses of volcanic pebbles ...... 31

11. Detail of volcanic conglomerate as channel-form lenses within tuffaceous conglomerate ...... 31

12. Marl lenses in fine tuffaceous facies mudstone overlain by ashy mud s h a l e ...... 35

13. Typical shale/sand facies mud shale ...... 37

14. Color banded siltstone, mudstone and shale of the shale/sand facies ...... 37

15. Fine grained sandstone with small-scale cross­ lamination ...... 39

Ix Figure Page

16. Fine grained quartz sandstone of the sand/conglomerate facies with thin lenses and stringers of shale or coarse s a n d ...... 44

17. Isolated channel-form conglomerate of the sand/ conglomerate facies ...... 46

18. Composite channel-form conglomerate of the sand/ conglomerate facies ...... 46

19. North-south stratigraphie correlation of Muddy Creek basin lithofacies ...... 51

20. Stratigraphie framework of selected Tertiary b a s in s ...... 58

21. Sandstone classification diagram ...... 76

22. Clast mixture classification diagram ...... 76

23. Clay, s il t , sand mixtures diagram ...... 77

24. Carbonate, s ilic a , sand, mud mixtures diagram .... 77 I

INTRODUCTION

Tertiary intermontane basins in southwestern Montana are d is trib u ­

ted between the Idaho Batholith on the west, the Snake River Plain on the south and the Absoraka and L ittle Belt mountains on the east.

This area is characterized by numerous elongate, predominantly north­ west to northeast trending, mountain ranges that rise above basins that are partially to nearly completely filled with thick sequences of

Cenozoic continental sediments (Figure 1). Most of the basins have one or more associated range front normal faults which have title d and folded the Tertiary strata (Pardee, 1950; and others). The orientation of these faults is generally subparallel (northwest-southeast and north­ east-southwest) to an underlying structural fabric dominated by late

Cretaceous compressional tectonics.

A general discussion of the geologic history and sedimentation patterns of the Tertiary basins of southwestern Montana is included in the "Regional Correlation and Comparison" section of this report. In that section I also discuss previous work on the basins and stratigraphie nomenclature.

Muddy Creek Basin

The Muddy Creek basin is located in the Tendoy Mountains approxi­ mately ten miles west of Dell, Montana, and covers portions of five U.S. I

T

4 6 ®

Three Forks

Wisdom

^Salmon / j ' V \ / p i Hon

A.

45 '

1 1 2 ® III®

Figure 1. Tertiary basins of southwestern Montana (stippled). Key to basins referred to in the text: 1, Muddy Creek; 2, Jefferson; 3, Three Forks; 4, Beaverhead; 5, Upper Ruby; 6, Canyon Ferry, (modified from Thompson, e_t , 1981) Geological Survey quadrangle sheets (Dixon Mountain, Graphite Mountain,

Deer Canyon, Caboose Canyon, and Kidd). The basin contains a well ex­

posed, uninterrupted and structura lly uncomplicated sequence of east­

ward dipping early Oligocene, or slightly older. Renova Formation

sediments. A stratigraphie thickness of over 1000 meters of tilte d

lacustrine and alluvial sediments is overlain at the north end of the

basin by extrusive igneous rocks. These Tertiary sediments are in un­

conformable and normal fa u lt contact with the Medicine Lodge and Tendoy

thrust sheets (Scholten et , 1955) which contain Precambrian to

Cretaceous rocks (Figure 2).

The Muddy Creek basin is the f ir s t Tertiary basin within the south­

western Montana overthrust belt to be studied in detail. It is also one

of the few basins that contain exposures with sufficient continuity to

allow a comprehensive examination of both vertical and lateral strati­

graphie relationships.

Purpose

This study was undertaken to provide detailed information on the

Tertiary geology of Muddy Creek basin for comparison with other Tertiary

intermontane basins, and as a contribution to the understanding of

regional Tertiary geology.

Methods

Seventy-nine fie ld days were spent during the summer of 1981 locating and collecting fossils, measuring stratigraphie sections, mapping sediments and recording structural data. All major structural features bordering the Muddy Creek basin

Tertiary sequences have been mapped previously (see Scholten, et a l.,

1955, for a compilation). For this study. Tertiary structure and

lithology were mapped in detail. In addition, previously mapped

structure immediately adjacent to the basin-fill beds was reevaluated.

Mapping changes were made where necessary and some structural details

were added. Mapping was done using aerial photographs (Bureau of Land

Management - DAP-Dillon, 1976; 1:32,000) and U.S. Geological Survey

topographic base maps (1:24,000). A reduced scale composite of these

maps is included in this report (Plate 1).

Vertebrate, invertebrate, and plant fossils were collected through­

out the basin. Vertebrate specimens were either surface collected,

quarried, or screen-washed from quarry matrix. Plant impressions and

fish scales were located by parting shale and siltstones along bedding

planes. Most invertebrate specimens were bound in rock samples. All

identified or potentially identifiable specimens were catalogued into the collection of the University of Montana Museum of Paleontology.

Stratigraphie sections (see appendix) were measured at twelve lo­ cations using a jacobs s ta ff and clinometer. Samples taken at each lith o lo g ie change were la te r studied under a binocular microscope, and some mudstone and shale samples were analyzed by X-ray d iffra ctio n methods. Terminology and procedures used in presenting lithologie descriptions are discussed in the appendix. Previous Work

Although a significant amount of geologic work has been done in the general area of Muddy Creek basin, the Tertiary geology has received l i t t l e attention. Early work in the Tendoy Mountains was prim arily concerned with o il shale exploration in the Phosphoria Formation, a l­ though notice was given to the presence of Tertiary shales (Bowen, 1917;

Condit, 1919; Winchester, 1923). Winchester (1923) estimated the o il potential of shales in the Muddy Creek basin and noted that an o il well had been drilled previously in the basin. Apparently thi s dry well was d rille d in the early 1900's in the SE&, Sec 29, T13S, RlOW (oral communi­ cation with area residents).

In the late 1940's the University of Michigan in itia te d a mapping project in the Lima region under the direction of A. J. Eardley.

Several Master's theses, and Ph.D. dissertations by Keenmon (1950),

Kupsch (1950), and Scholten (1950) resulted from this work. Some of the theses include portions of the Muddy Creek basin (Becker, 1948;

Krusekopf, 1948; Lipp, 1948; Smith, 1948; Wallace, 1948; and Kupsch,

1950).

A synthesis of the University of Michigan thesis work resulted in the recognition of the Montana thrust belt by Eardley (1951) and the publication of a comprehensive interpretation of the geology of the Lima region by Scholten, Keenmon, and Kupsch (1955). Further interpretations of the regional tectonics have been discussed by Scholten (1961, 1967),

McMannis (1965), Skipp and Hait (1977), Ruppel (1978), Perry et a l.,

(1981), Ruppel ^ , (1981), and others. The evolution and distribution of the syntectonic Beaverhead

Formation has been studied by Lowell and Klepper (1953), Ryder (1967,

1968), Ryder and Ames (1970), Wilson (1967, 1970), Ryder and Scholten

(1973), and others.

A number of studies have concentrated on specific aspects of

Paleozoic and Mesozoic stratigraphy in the area. These include Sloss and Moritz (1951), Scholten (1957), Cressman (1955), Cressman and

Swanson (1964), Maughn and Roberts (1967), Huh (1967), Klecker (1981b), and others.

Very recently, several areas in the Tendoy Mountains have undergone réévaluation in thesis work by Klecker (1981a), Sadler (1981) and others. Additional work is presently in progress. II

STRUCTURE

Laramide Structure

Muddy Creek basin straddles the leading edge of the Medicine Lodge

thrust plate, a system of tight folds and imbricate thrusts that ex­

tends across southwestern Montana and east-central Idaho (Ruppel, 1978,

1981). In the study area, exposures of the Medicine Lodge allochthon,

consisting exclusively of Mississippian carbonates, overlie younger

rocks of the Tendoy thrust plate (Figure 2).

The most prominent Laramide structure in the study area is in the

Tendoy thrust plate along the eastern edge of the Muddy Creek basin.

Here, southwest plunging folds (L ittle Water Syhcline, Timber Butte

Anticline and minor folds) are cut by a series of northwest trending

imbricate thrusts, reverse faults and normal faults (Figure 2). Several small thrust slices that cross the L ittle Water Syncline and abut Muddy

Creek basin Tertiary beds are of particular interest because they have been variously interpreted as a refolded extension of Mesizoic rocks in the syncline or as Mississippian rocks related to the Medicine Lodge thrust (Scholten, ejt a/[., 1955; Ryder and Scholten, 1973, and others

(Figure 2). Extreme deformation has obscured the lithologie identity of these rocks. Recently, careful mapping in the Little Water Syncline by

Klecker (1981a) suggested that the deformed rocks are thrust slices of the

Medicine Lodge plate flanked on the east by trapped slices of Mesozoic rocks. Mapping for this study agrees closely with Klecker's work.

7 8

— LITHOLOGIES — Il I II Paleozoic TENDOY Missippion THRUST [//I Jurossic/Thossic Cretaceous I I Cenozoic - STRUCTURE SYMBOLS Thrust Fault Anticline — Syncline

Figure 2. Generalized geologic map of the Muddy Creek basin area emphasizing Laramide structure. Similar thrust contacts are mapped across the Little Water Syncline and an additional reverse fa u lt was noted on the southern limb.

Samples taken for paleontological analysis from the deformed thrust

slices that cross the L ittle Water Syncline, and analyzed by the U.S.

Geological Survey (W. J. Perry, personal communication) indicate,

however, that the rocks in question are upper Thanes Formation (Triassic);

hence they belong to the Tendoy thrust plate. Therefore, the Medicine

Lodge thrust appears to be buried beneath Tertiary sediments where the plate overrides several imbricate thrusts of the Tendoy thrust plate

(Figure 2).

Tertiary Structure

Muddy Creek basin is bounded on the east and west by a series of faults that strike subparallel to underlying thrust trends (Figure 3).

Sediments flanked by these faults consist of relatively undistorted, eastward dipping Tertiary beds.

Intra-basin Structure

Bedding attitudes of Tertiary sediments throughout the basin exhibit an average eastward dip of + 25 degrees. This dip is consistent in all exposures including those that overlap pre-basin rocks (Figure 4). Vir­ tu a lly a ll of the dip appears to be secondary because most b a s in -fill sediments were a product of low energy deposition. Local dip variations of up to ten degrees suggest slight folding, disruption, or initial dip.

However, many 1ith o lo g ica lly d istin ct bedding sequences can be traced la te ra lly along the length of the basin without apparent interruption. \0

^ Form Lines , parallel to strike

^ Normal Poult

► Anticline

I Syncline

\ \\ East Muddy \ '\ A O Creek Poult

Figure 3. Sketch map of the Muddy Creek basin area emphasizing Tertiary structure. Circled numbers refer to features discussed in the text. Lithologies correspond to Figure 2. 11

Figure 4. Unconformable contact between Paleozoic limestone and tilte d Tertiary beds. Jacobs s ta ff (1.5m) marks area of underlying Paleozoic limestone (Section 10). 12

Form line contours assembled from bedding surfaces and strike and dip measurements indicate that the b a s in -fill sediments tend to conform to

the western basin margin and curve gently toward the southeast and

northeast ends of the basin (Figure 3). This curved pattern of strikes

is suggestive of a gentle eastward plunging syncline or monocline in which the sediment package bends and thickens into the southcentral part

of the basin (Figure 3, Plate 1). Alignment of stream drainages suggest

cross faulting in several areas, but direct evidence for any offset is

lacking. Aside from very minor localized offsets, the only demonstrable

intra-basin structure is a small southwest trending anticline in the

area of Johnson Creek that has possibly been affected by minor faulting

across its hinge (Figure 3, Plate 1).

Basin Bounding Faults

East Muddy Creek Fault. Along much of the eastern edge of the Muddy

Creek basin, eastward dipping Tertiary sediments are truncated by the

East Muddy Creek Fault (Scholten, et , 1955) (Figure 3). A prominent fa u lt scarp across the L ittle Water Syncline suggests an apparent high angle normal fa u lt. To the north of this area, the scarp disappears and the fa u lt trace either terminates or is covered by sediments. The fa u lt scarp also disappears to the south where i t intersects a short east-west trending fault that offsets the main fault trace slightly to the east. The East Muddy Creek Fault can then be traced southward along the flared southern limb of the L ittle Water Syncline as a low angle normal fault parallel to bedding in the footwall to where it nearly intersects the Medicine Lodge Thrust (Figure 2,3). The curving, narrowing, and 13

shallowing of the southern part of the basin is attributable to this

low angle fa u lt. Fault dip measurements are unavailable because of extensive cover except in the southern part of the basin where a series of cross canyons expose the fa u lt geometry. Here, eastward dipping

Tertiary beds abut the westward dipping bedding planes of the Permian

Phosphoria Formation (Figure 5). Basin beds dip from 34 to 14 degrees, with variation for drag, and Phosphoria Formation beds dip about 22 degrees (Plate 1).

The apparent combination of high and low angle faulting (Figure 6) poses complications regarding Tertiary bed rotation along the fault. For example, cross section A-A' (Figure 3,7) is in accord with a 25 degree rotation of uniform Tertiary beds by assuming the presence of a lis t r ic normal fault that curves, at depth, into a thrust fault. It is difficult, however to model fa u lt geometry in such a way that beds w ill also rotate with consistent strike and dip into a low angle fa u lt (cross section

B-B‘ , Figure 3,8). This low angle fa u lt does not appear to represent the basal extension of a listric fault, as the fault plane is in­ compatible in elevation with a listric fault to the north.

To interpret fault geometry and bed rotation with any certainty, geophysical studies not undertaken for this project would be required.

Possible relationships that would allow bed rotation might include:

(1) the presence of a concealed high angle fa u lt to the east of the low angle fa u lt, or (2) a complex combination of rotation and spreading along a shallowing fa u lt trace. Another p o ssib ility is that the eastward t ilt in g of basin beds occurred independent of basin faulting. In that 14

Figure 5. Low angle fa u lt contact. East Muddy Creek Fault. Eastward dipping Tertiary beds (uppermost sequence) intersect westward dipping Permian Phosphoria Formation beds (lower, lighter colored rocks). SEi, RlOW, T14S. \5

«»'* 'Z rw « 16 case, beds tilte d by broad scale tectonics could be offset, with l i t t l e or no rotation, along a low angle fa u lt extending the length of the basin. Such a configuration is supported by: (1) continuity of dip where basin beds overlap pre-basin rocks (Figure 4), (2) sim ilar east­ ward dip of Tertiary sediments in areas adjacent to the basin, and

(3) basin width to depth ratios indicated for bed rotation (Figure 7).

Any t ilt in g of basin beds not related to basin normal faulting would, however, change the original structural attitude of underlying Laramide structures and involve aspects of regional tectonics that are beyond the scope of this study.

West Muddy Creek Faults. A series of contacts interpreted as dis­ continuous normal faults have been mapped along the western edge of the

Muddy Creek basin Tertiary sediments (see Scholten, and others, 1955 for a compilation), (Figure 3). These "faults" are expressed primarily as linear contacts (locally exhibiting up to several hundred feet of re lie f) between basin beds and Paleozoic rocks. With the exception of one small cross-fault, however, direct evidence for faulting can not be demonstrated.

The southernmost of these "faults" trends northwest for approximately three kilometers and disappears into undisturbed Tertiary sediments

(Figure 3, no. 1). Farther to the west, another segment extends north- northwest approximately six kilometers to the area where the Medicine

Lodge Thrust cuts into the basin (Figure 3, No. 2). At that point, the fault appears to die out or is buried by Tertiary sediments. A small cross fault in that area (Figure 3, No. 3), indicated by slickensides Geologic Cross Sections of the Muddy Creek basin. (For section loca­ tions see Figures 2, 3, or Plate 1).

Figure Possible high angle Figure 8. Low angle normal listric normal fault fault at (2).

to CMCMI

CL o>

H-

_ o

m o w o o o t- Hi 8 o 111 18 and brecciated rocks, offsets Tertiary sediments and connects a short distance to the east with a segment (Figure 3, No. 4) that extends to the northern end of the basin.

It is not clear that all of the "fault" segments represent normal faults. Northern segments (Figure 3, Nos. 3,4) cut across the strike of basin beds and are, therefore, mapped as normal faults. The two southern segments (Figure 3, Nos. 1,2), however, involve l i t t l e or no truncation of basin bed strikes and are subparallel with the Paleozoic bedding fabric.

The relationship of these "faults" to basin tectonics is not clear.

Their origin may be related to faulting on the east side of the basin.

Speculation as to their significance might include: (1) low offset normal faults formed in response to arcing tension when Tertiary beds were tilte d to the east; (2) simple extensional fau lts; or (3) a combination of the above. I t also seems possible that the southern segments express buried topography at the leading edge of the Medicine Lodge Thrust plate. Ill PALEONTOLOGY AND AGE DETERMINATION

Vertebrates

Localities and Fauna

Although vertebrate bone scrap was found in many areas of the basin, only seven localities produced identifiable fossils (Figure 9, Plate 1).

Several hundred specimens were collected from these lo calities repre­ senting twenty-four mammalian species plus undetermined reptiles and fish (Table 2). Unidentified fish scales and skeletal fragments were collected outside of designated vertebrate collecting sites.

Age Determination

All localities indicate an early Chadronian (approximately late

Eocene to early Oligocene) age for the b a s in -fill beds. (Epoch and

North American land mammal ages follows Lilligraven, e;t. , 1981.)

Dated lo c a litie s (MV-7630,7631,8106,8107) are situated only in s tra ti- graphically higher sediments and it seems possible that slightly older sediments may also be present in the basin.

PI ants

Plant impressions and fragments of fossil wood were collected from a ll Muddy Creek basin sedimentary lithofacies (see Fig. 9). Three specific plant lo ca litie s (Mp-8101,8102,8103) offered consistently good preservation

19 20

(Figure 9, Plate 1). The seventeen species represented in this collection

(Table 1) are consistent with mid-Tertiary floras described by MacGinitie

(1953) and Becker (1960, 1961, 1965 and other papers). Most specimens collected have the greatest affinity to the Florissant flora (MacGinitie,

1953), which is considered to be e a rlier in age than the floras described by Becker, Leaf size and species variety appear to indicate an environ­ mentally stressed, cool-moist temperature micro-paleoenvironment

(C. N. M ille r, personal communication).

Invertebrates

Pelecypods, ostracods and freshwater gastropods were collected from limestones, marls and a few shales. Gastropods were found, to some extent, in all sediment types including conglomerates. Although no attempt has been made to identify invertebrate species, a large number of species appear to be present in the sample and further work may provide useful age and ecological information. 21

Tab!e 1. Floral List

SPHENOPHYTES

Equisetum sp.

GYMNOSPERMS

Family: Taxodiaceae

Glyptostrobus sp. ^

Taxodiurn sp.

Metasequoia occidentalis Chaney,

Family: Pinaceae

Pinus sp.

Pinus cf. £. Monticolensis Berry

ANGIOSPERMS

Family: Sparanaceae

cf. Sparganiurn sp.

Family: Ulmaceae

cf. Ulmus sp.

Family: Fagaceae

Quercus sp.

Family: Oleaceae

Fraxinus sp.

Family: Aceraceae

Acer sp.

Family: Rosaceae

Amelanchier sp.

cf. Crataegus sp. 22

Table 1. (Continued) ______

Family: Saxifragaceae

Hydrangea sp.

Family: Myricaceae

Myrica sp.

Family: Vitaceae

cf. Vitus sp.

Family: Anacardiaceae

Rhus sp. Table 2. Vertebrate Faunal List

Localities

MV7630 MV7631 MV8106 MV8107

Class REPTILÎA

Order TESTUDINATA

Order SQUAMATA

Family Sauria

Class TELEOSTOMI

Gen. and spp. indet. (scales)

Order CYPRINIFORMES ?

Class MAMMALIA

Order MARSUPIALIA

Family Didelphidae

Herpetotherium sp. cf. H^. fugax Cope

Order INSECTIVORA

Family Leptictidae

Leptictus acutidens (Douglass) ro CO Table 2. (Continued)

Localities

MV7630 MV7631 MV8106 MV8107

Order LAGOMORPHA

Family Leporidae

?Mytonolagus sp,

Gen. and spp. indet.

Order RODENTIA

Family Cylindrodontidae

Cylindrodon sp.

Family Ischyromyidae

Ischyromys sp. ?

Titanotheriomys douglassi (Black)

Family Eutypomyidae

Eutypomys sp. aff. E. parvus Lambe

Family Eomyidae

Adjidaumo sp. cf. A. minimus (Matthew) ro - P i Paradjidaumo trilophus (Cope) Table 2. (Continued)

Localities

MV7630 MV7631 MV8106 MV8107

Family Eomyidae, continued

Namatomys sp. X

Yoderimys stewarti (Russel) X

Gen. and spp. indet. X X

Order CREODONTA

Family Hyaenodontidae

Hyaenodon (Protohyaenodon) n. sp. ? X

Order CARNIVORA

Gen. and spp. indet. X X

Order PERISSODACTYLA

Family Brontotheriidae X

Family Equidae

Mesohippus sp. X

PO tn Table 2. (Continued)

Localities

MV7630 MV7631 MV8106 MV8107

Order ARTIODACTYLA

Family Entelodontidae

Archaeotheriurn sp.

Family Merycoidodontidae or Agriochoeridae

Gen. and spp. indet.

Family Camelidae ?

Family Leptomerycidae

Leptomeryx n. sp.

Leptomeryx sp. cf. I, blacki Stock

Leptomeryx sp. cf. L speciosus Lamb

Leptomeryx sp. cf. L mammifer Cope

?Hendryomeryx sp.

Family Protoceratidae

cf. "Leptotragulus" profectus (Matthew) ro cr> 27

Coorse Tuffaceous Facies Fine Tuffaceous Facies Shale/Sand Facies

Sand/Conglomerate Facies Volcanic Facies

Pre-basin Rocks

MV Vertebrate Lacality MP Plant Locality

JV

# 7 A

• 40

.48 • 4A

MV

• 10 3A #38

JIB MA

Figure 9. Sketch map of Muddy Creek basin lithofacies distribution, stratigraphie section locations, and key fossil collecting lo c a litie s . Numbers lA through 12 refer to measured sections described in the appendix. IV

STRATIGRAPHY AND DEPOSITIONAL ENVIRONMENTS

The eastward t ilt in g of Tertiary sediments in the Muddy Creek

basin has exposed d is tin c t, la te ra lly extensive bedding sequences.

Vertical and lateral facies relationships within these sequences

were examined in stratigraphie sections measured at twelve locations

(Figure 9, Plate 1). Complete descriptions of the lithology and

sedimentary structure of these stratigraphie sections are contained

in the appendix.

Many 1ith o lo g ica lly d is tin c t bedding sequences can be traced

la te ra lly for several kilometers without apparent disruption but

individual lith o lo g ie units are broadly lenticular and most pinch out / within a few meters (see illustration of section no. 1, appendix).

D istinctive marker beds are not present within the bedding sequences

and it is difficult to accurately correlate individual units from one

section to the next. Because rock sequences dominated by a particular

sedimentary texture and gross mineralogy are well defined, the lith o ­

facies constitute practical units for mapping and correlation. Further­ more, the combined characteristics of each lithofacies reflect inter­

related modes of deposition useful in the interpretation of depositional environments. For the purpose of mapping and correlation, Muddy Creek basin sediments are divided into five lithofacies: (1) coarse tuffaceous, (2) fine tuffaceous, (3) shale/sand, (4) sand/conglomerate,

28 29

and (5) volcanic (Figure 9, Plate 1). These lithofacies are described

and interpreted below in ascending stratigraphie order. Illustrated

stratigraphie sections in the appendix are subdivided and labeled as

to lithofacies type. All Muddy Creek basin lithofacies are assigned

to the Renova Formation (Kuenzi and Fields, 1971), but further sub­

divisions are not proposed (see Regional Correlation and Comparison

section).

Coarse Tuffaceous Facies

Description

This facies is characterized by tuffaceous sediments that retain

most of their original pyroclastic character. Rock types include

tuffaceous conglomerates, very crudely bedded v itr ic rhyolite tu ffs ,

minor amounts of porphyritic rhyolite, moderately well-bedded

tuffaceous siltstone and sandstone, and rare gastropod-bearing lime­

stones and marls. This lithofacies is distributed along the western

and northwestern edge of the Tertiary sequence (Figure 9, Plate 1)

and is detailed in stratigraphie sections 5, 8, 7A, 78, and 10 (see

appendix). Limited outcrops of sim ilar composition and texture also

overlie Paleozoic and Mesozoic rocks adjacent to the tilte d Muddy

Creek basin sediments (Plate 1).

Conglomeratic units consist principally of an unsorted mixture of s ilt, sand, and pebble to small boulder size volcanic clasts.

Basalt pebbles and cobbles plus rounded intraformational tuffaceous siltstone cobbles are suspended throughout the fin e r rh y o litic 30 material (Figure 10). Indistinct lenses containing poorly graded, matrix-supported basaltic pebbles are common. One large channel-form lens fille d with rounded, grain-supported basaltic cobbles and boulders was also noted (Figure 11).

Conglomerate units grade into, or are abruptly capped by, evenly bedded, moderately well-sorted tuffaceous sandstones or siltstones.

The only sedimentary structures apparent in these units are thin con­ cretionary horizons and localized accumulations of small isolated lenses of siltstone. Contacts between siltstone and sandstone beds are often d is tin c t and marked by pronounced color changes.

Vitric tuff units are mostly composed of ash and angular, fresh- looking quartz, feldspar, and mica crystals. A small percentage (5% or less) of the material, however, consists of subrounded lith ic fragments and crystals. Tuff units are generally interbedded with siltstones and sandstones and lack obvious sedimentary structure.

Sandstone, siltstone and tu ff beds a ll contain rare isolated concen­ trations of plant debris.

Porphyritic rhyolites are characterized by a pink to lig h t gray groundmass containing coarse sand-sized feldspar phenocrysts. Outcrops of porphyritic rhyolite are largely limited to the northern tip of the

Muddy Creek basin along Sourdough Creek. However, minor amounts of porphyritic rhyolite are also interbedded with vitric tuff deposits at the northernmost lim it of the coarse tuffaceous facies.

Although Kupsch (1950) suggests that the porphyritic rhyolite may represent a shallow intrusive, such a relationship could not be demon­ strated in the field. Rhyolite interbedded with tuffs apparently 31

$

Figure 10. Tuffaceous conglomerate, with lense of volcanic pebbles. (Section 8, Unit 1) Lens cap is 6 cm in diameter.

Figure 11. Detail of volcanic conglomerate as channel- form lense within tuffaceous conglomerate. (Section 8, Unit 1). Note hammer for scale 32 represents, in part, subaerial flows related to the deposition of rhyolite tuffs.

Limestone and marl beds are rare except where the coarse tuffaceous facies is transitional with other facies. These units are thin (to 2.3 meters), crudely laminated, and contain abundant gastro­ pod fossils. They are always interbedded with sandstones and siltstones

Interpretation

The interbedding of coarse tuffaceous material with limestones and marls that are clearly lacustrine in origin suggests deposition in a marginal lacustrine environment. Because of the pyroclastic origin of most of the sediments in the coarse tuffaceous facies, however, depositional processes are not always clear. There are, for instance, few reliable distinctions between airfall and waterlain deposition

(see Lajoie, 1979 for a discussion).

The wide distribution (Figure 9, Plate 1), lenticular inter­ bedding and general depositional character of this facies resembles both debris flow dominated fans (Gloppen and Steel, 1981) and modern distal volcanic fan facies (Vessel 1 and Davies, 1981; Kuenzi et a l.,

1979, and others). The generally high matrix to clast ratio and lack of any pervasive structure in the conglomeratic units is typical of flu id debris flows. Likewise, isolated, channel-form conglomerates are consistent with the braid-channel component of these fans. Debris flow units similar to those in the coarse tuffaceous facies that grade into, or are abruptly overlain by finer grained, more uniform 33 deposits have been described for both subaerial and subaqueous portions of fans. Gloppen and Steel (1981), Larsen and Steel (1978),

Johnson (1970), and Schmincke (1966), interpret the transition to finer material as the result of sediment winnowing by water-flow or turbidity currents. Sandstone units in the coarse tuffaceous facies that contain small lenses of s ilt are consistent with such an in te r­ pretation; the lenses probably represent scour runnels associated with sediment winnowing.

Massive, crudely bedded v itr ic tuffs and some bedded sandstones and siltstones probably represent fan-blanketing surges of airfall material (Vessel and Davies, 1981; and others). These may be either subaerial or subaqueous deposits.

Typical sedimentary structures associated with deltaic deposits are not present, despite the intimate association of fan deposits with both interbedded and la te ra lly equivalent lacustrine sediments.

Nevertheless, the coarse tuffaceous facies sediments are interpreted as a fan-delta. The cyclic inundation of shallow water by volcanic debris flow and a irfa ll material appears to have prograded over lacustrine deposits as a broad front of sedimentation that lacked su fficie n t channeling to produce deltaic lobes.

Fine Tuffaceous Facies

Description

Interbedded limestones, marls, siltstones, mudstones, and shales characterize the fine tuffaceous facies. Porcellanite and lithic 34 sandstone beds are also present, but uncommon. Siltstone, mudstone, and shale, which are the most abundant sediment types, are composed principally of tuffaceous material. Limestones and marls also contain a significant amount of ash. Lithologie sequences in this facies are described in stratigraphie sections 5, 6 and 7B (appendix).

Shale units are thinly laminated. Plant debris is rare, and unfragmented mol lusk shells are locally abundant along the laminae.

Siltstones and mudstones are massive or crudely laminated, evenly bedded, and re la tive ly unfossiliferous. Some of the mudstones contain broad, thin lenses (averaging 10 cm. thick by 5 m. wide) of marl

(Figure 12).

Marl beds are either massive or contain wavey internal laminae with thin tubular structures and irregular bedding contacts. Unbroken mollusk or ostracod shells, a major component of most marls, are con­ centrated as packstones or along bedding laminations. Mollusk and ostracod shells are generally not found together in the same bed.

Most limestones are silty, crudely laminated, and contain lenticular concentrations of lith ic sandstone or gastropods, and thin tubular structures.

Interpretation

The even bedding, vertical repetition of shales and marls, and ubiquitous presence of fresh water mollusks in this facies clearly represent lacustrine deposition. Interbedded massive or crudely laminated mudstones and siltstones could indicate fluctuations in lake 35

Figure 12. Marl lenses in fine tuffaceous facies mudstone overlain by ashy mud shale. (Section 5, Unit 14.) 36 level or sediment input, or periodic bioturbation. Transitions from calcareous rocks to mudstones, siltstones and shales probably re fle ct fluctuations in lake level, although they could indicate a cyclic disruption in carbonate production (Dean, 1981; Picard and High, 1981).

In either case, the combined presence of thin, broad limestone and marl units with near shore mollusk and ostracod shells that lack any indication of transport are considered reliable indicators of a low- energy nearshore environment (Picard and High, 1981; Bradley, 1925).

Because these nearshore indicators are persistent throughout the facies and desiccation features are absent, this facies is interpreted to represent shallow water deposition in a perennial freshwater lake.

Shale/Sand Facies

Description

The shale/sand facies is composed of mudstones, siltstones and shales with discontinuous beds of sandstone, conglomerate and, very rarely, limestone or marl. Clast composition is similar to that described below in the sand/conglomerate facies. This is one of the most widely distributed and thickest lithofacies mapped in the Muddy

Creek basin (Figure 9, Plate 1). It forms part or a ll of stratigraphie sections 1 A,B; 2 A,B,C; 3 A,B; 4 A,B,C; 5; 7B and 9 (appendix).

Shales are characterized by markedly parallel laminae with plant fragments and occasional fish scales concentrated along the partings

(Figure 13). The fissility and color of shales directly corresponds to plant debris content; shales with abundant plant debris (to 37

Figure 13. Typical shale/sand facies mud shale containing plant debris and fish scales along bedding laminae (Section 2A, Unit 2 ). Laminae average 3 cm thick.

Figure 14. Color banded siltstone, mudstone and shale of the shale/sand facies. (Section IB). 38

lignite) are darker and more fissile. Dark colored clayey paper shales

are an exception, however, and generally contain few plant fragments.

Most shale units grade v e rtic a lly into subtly color-banded siltstones

or mudstones (Figure 14). Although gypsum is locally abundant along

laminae or as a jo in t f illin g , sedimentary structures such as

desiccation features are not apparent.

Mudstones and siltstones are distinguished primarily by grain

size. Both are locally bentonitic, clay content is dominantly smectite,

and they contain a wide range of suspended clastic grains and primary

sedimentary structures. Common mudstone/siltstone variations are:

(1) massive; (2) crudely bedded, sandy, with rare gastropods, plant

debris, and fish scales; (3) slightly pebbly, with crude horizontal

laminae, rare iron-stained gypsum and siderite nodules, and calcareous

concretions; (4) sand, massive, with up to 15% suspended small pebbles

to large cobbles; and (5) sandy, crudely laminated, with small lenses

and stringers throughout of well sorted sandstone, shale and small

graded lenses of lith ic sandstone and pebble conglomerate. Isolated

gastropods occur in a ll of these types. Disarticulated vertebrate

bone scrap is primarily concentrated in type 3 mudstones and siltstones.

Sandstones are principally well-sorted litharenites that vary

considerably as to rounding and grain size. These units all have even to s lig h tly irregular bedding contacts and form thin (20 cm. to

1.5 m), sheet-like, lenticular beds. Most units are massive, although a number of units contain crude horizontal laminae; small-scale, low- angle cross-laminae in tabular sets (Figure 15); or small lenses of coarser sand. 39

1

Figure 15. Fine grained sandstone, with small scale cross-lamination. Note both planar and trough-shaped sets are present (Section 3, Unit 15). Lense cap is 6 cm in diameter. 40

Conglomerates are rare in the shale/sand facies. Where present,

they usually occur as isolated channel-form lenses (up to 1.5 m. thick

by 5 m. wide) that cut deeply into underlying units. The principal

sedimentary structures in conglomerate lenses include trough cross­

beds, crude horizontal s tra tific a tio n , and graded bedding. Local

lenses of si 1tstone and sandstone are also present. Subrounded to

subangular clasts vary from small pebbles to boulders. A few con­

glomerates are, however, massive, loosely packed, p a rtia lly matrix-

supported, and sheet-like with even bedding contacts.

Limestone and marl beds are extremely rare in the shale/sand

facies. Marls are sim ilar to those described for the fine tuffaceous

facies and contain abundant gastropods. Limestones are dense, massive,

cherty, and contain thin, irregular, caliche or algal-like laminations.

Most of the limestone and marl units are limited in lateral extent

to a few hundred meters. One thick (to 5 m.) limestone unit, however,

forms a "boudin-1ike" horizon that can be traced laterally for several

kilometers.

Interpretation

Laminated limestones; marls containing gastropods; and mudstones, siltstones, and shales containing fish scales are clearly lacustrine in origin. The even parallel lamination of the shales and concen­ tratio n of plant fragments along bedding planes indicate tranquil deposition and a lack of bioturbation.

Channel-form clast-supported conglomerates and sheet-like, cross­ laminated, non-graded, sandstones interbedded with lacustrine sediments 41 suggest a braided-stream environment (M iall, 1977; Rust, 1977; Smith,

1970).

The pebbly siltstones and mudstones, and massive, sheet-like, sandstones and conglomerates are consistent with fluvio-lacustrine environments (Flores, 1981; Heward, 1978a; Monroe, 1981; and others).

A vertical repetition of lacustrine and fluvial deposits is present in the shale/sand facies, but upward-coarsening sequences and steep cross-bedding usually associated with delta progradation are absent. Indeed, there is no apparent c y c lic ity to these deposits and a ll possible combinations of interbedded fine and coarse sediments are common. Similar, but apparently less variable, fluvio-lacustrine sequences have been described from the upper Ruby River basin as shoreline fluctuations responding to changes in lake level (Monroe,

1981), and from the Fort Union Formation as the interaction between flood basin crevasse-splays and shallow lake deposits (Flores, 1981).

Because the shale/sand facies intertongues with alluvial-fan deposits of the sand/conglomerate facies (Figure 10, Plate 1) and because of the sheet-like geometry of the sandstones, absence of sedimentary structures associated with deltas, and the persistent lateral and vertical repetition of fluvial and lacustrine deposits, this facies is interpreted to represent the progradation of distal allu via l fan sediments over lake margin and shallow lake deposits.

Similar fan-delta relationships in Carboniferous coal field deposits have been interpreted by Heward (1978a) as the interbedding of distal a llu via l fan deposits with marginal lacustrine sediments. 42

Anastamosing stream flow over broad, distal allu vial-fa n lobes

and a very low offshore slope account for the absence of deltaic

structures and the presence of sheet-like sand bodies (Coleman, 1976;

Monroe, 1981). Channel-form conglomerates, wide variations in grain

size and bedding scour, and a lack of cyclic bedding sequences

all indicate irregular surges of sedimentation consistent with

a llu via l-fa n environments (Bull, 1972; Rust, 1979). Pebbly mudstone

and si 1tstone containing disarticulated vertebrate fossils, scour

runnels, nodules and concretions probably represent subaerial overbank

and sheetwash deposits modified by pedogenic processes (Flores, 1981).

The well-bedded, but poorly-sorted, pebbly mudstones and siltstones,

and sheet-like conglomerates could result from subaerial and/or

subaqueous debris flows (Gloppen and Steel, 1981).

Although the alternation of flu via l and lacustrine sediments

suggests fluctuation in lake level, nearshore conditions appear to

dominate. Indicators of shallow water deposition including well-

preserved plant debris, nearshore mollusks, and algal laminated

limestones are ubiquitous (Allen, 1959; Picard and High, 1981).

Massive lacustrine mudstones and siltstones may indicate deeper water

but could equally well refle ct bioturbation, surges of fine sediment, or fluctuations in the amount of plant debris entering the lake.

Localized gypsum may indicate drying conditions; however, the absence of desiccation features, such as mudcracks or a suite of evaporite minerals, rules out playa-like conditions. Also, gypsum crystal types and bedding relationships appear most consistent with subaqueous or 43 secondary deposition (Kendall, 1979).

Sand/Conglomerate Facies

Description

The sand/conglomerate facies is characterized by interbedded sandstones, siltstones and conglomerates. A few mudstone beds are also present. These sediments are principally composed of lith ic material derived from Paleozoic and Mesozoic rocks that border the

Muddy Creek basin. This facies intertongues with the shale/sand facies and becomes thicker and re la tive ly more coarse to the south (Figure 9).

The sand/conglomerate facies is present in stratigraphie sections

3 A,B,C; 4C, IIB; and 12 (appendix).

Sandstones are predominantly fine-grained, poorly indurated, and contain in d istin ct horizontal laminae. Two basic types of sandstone are present: 1) pebbly sandstones of variable gravel content (up to

15%) in which isolated clasts of coarse subangular sand to small cobbles are suspended in a fine sand matrix, and 2) slig h tly pebbly lit h ic sandstones and pure quartz sandstones in which coarse sand to medium pebbles are principally concentrated in small (up to 10 cm. wide by .5 m. thick) lenses and irregular pockets. Lenses and stringers of shale are present in some of these sandstones (Figure 16).

Siltstones and mudstones are massive or crudely bedded and contain variable amounts (up to 10%) of coarse, subangular, lith ic sand and small pebbles suspended in the fine matrix. Some of these beds contain sand and pebble lenses sim ilar to those described above for the sandstone units. 44

Figure 16. Fine grained quartz sandstone of the sand/ conglomerate facies with thin lenses and stringers of shale or coarse sand. (Section 3, Unit 6). 45

Conglomerates occur as both isolated and composite channel-form lenses. These vary considerably in size (from .5 m. thick by 1 m. wide to 5 m. thick by 8 m. wide) and scour deeply into underlying sediments. Isolated lenses cut sandstones and siltstone beds

(Figure 17). Composite lenses are interconnected or closely spaced and form bedding units that often extend la te ra lly for tens of meters

(Figure 18). Channel-form lenses contain trough cross-beds, crude horizontal s tra tific a tio n , and poorly developed graded bedding.

Local lenses of pebbly siltstone to coarse sandstone are also present in the channel-form units. Clasts are subangular to subrounded, grain supported, and range in size from small pebbles to boulders up to three meters in diameter. Rare pebble imbrication indicates flow from the south and east. A few isolated conglomerates are sheet-like, evenly bedded, crudely s tra tifie d , and p a rtia lly matrix supported.

Interpretation

The distribution and abundance of coarse elastics and the range of sedimentary structures in the sand/conglomerate facies is typical of allu vial fan deposits (Bull, 1972; Rust, 1979; and others).

Trough cross-bedded, crudely s tra tifie d , isolated and composite channel-form conglomerates are interpreted as braided-stream sediments

(Rust, 1977; M iall, 1978). Because braid-channel abundance and grain coarseness increases towards the southeast (the source direction inferred from sedimentary structures), the conglomerates probably represent anastamosing stream flow over proximal to distal portions of an allu via l fan (Heward, 1978a, 1978b; Rust, 1979). Differences in grain 46

Figure 17. Isolated channel-form conglomerate of the sand/conglomerate facies. (Section 3, Unit 3) Jacobs s ta ff is divided in decimeters.

Figure 18. Composite channel-form conglomerate of the sand/conglomerate facies. (Section 12). Black spots are swallow nests that average 10 cm in diameter. 47

size and scour depth, and the presence of lenses of finer material within the conglomerates reflect variable surges of sedimentation.

Similar sequences in the upper Ruby River basin (Monroe, 1981) and

the Uinta basin (Ryder and others, 1976), that contain both isolated

and complex channel-form conglomerates, have also been interpreted

as allu vial fan deposits.

Poorly sorted pebbly sandstones, siltstones, and mudstones, and

crudely stratified, partially matrix-supported conglomerates are con­

sistant with fan-related debris flows and turbulent stream flow

deposits described by Heward (1978b), Gloppen and Steel (1981) and

others.

Beds of laminated sandstone, siltstone and mudstone that contain

lenses of coarse sand and small pebbles are located principally in

areas where the sand/conglomerate facies and the shale/sand facies

merge. Because the sandstones, siltstones and mudstones are often

interbedded with lacustrine sediments, they lik e ly represent a coarser-

grained equivalent of the distal-fan deposits described for the shale/

sand facies.

Volcanic Facies

Description

This facies consists of massive basalt and andésite, basaltic agglomerate, and minor amounts of rhyolite tu ft. These volcanics are prim arily distributed across the northern end of the Muddy Creek basin where they unconformably overlie the tilte d Tertiary sequences. 48

Basalts also overlie Tertiary and Paleozoic sediments at the basin margin near McNinch Creek on the west side of the basin, and ag­

glomerates overlie bedded tuffs and Mesozoic rocks in the L ittle

Water Syncline (Figure 9, Plate 1). Because of locally extensive

soil cover, the exact distribution and interrelationships of the various volcanic types is not clear. Mapping distinctions are not made between the volcanic types, and areas mapped as volcanic facies

lo cally also include small areas belonging to other facies. No stratigraphie sections were measured across these deposits. The distribution and correlation of these and similar volcanics in the

Lima region has been discussed by Scholten, Keenmon, and Kupsch (1955),

Basalts and andésites are dense, dark gray to black rocks that weather reddish brown and cannot be differentiated in the fie ld .

However, Kupsch (1950), based on thin-section studies, noted a variation in composition from basalt to andésite. The basalts and andésites are interspersed with, and grade into, basaltic agglomerates.

Agglomerates are principally composed of pebble to boulder sized angular to subangular basaltic clasts. Subrounded lith ic clasts, clearly derived from nearby pre-basin rocks, are present in small amounts.

Interpretation

The generally unstructured appearance and intimate intermixing of dense basaltic material and agglomerate suggests that these deposits are autoclastic breccias (Lajoie, 1979). I t is not clear whether the 49 extrusives represent a single volcanic episode or multiple flows that may differ significantly in age.

Facies Relationships

The aerial distribution of Muddy Creek basin lithofacies reveals a center of lacustrine sediments flanked by fan-delta and alluvial fan deposits and overlain at the north end of the basin by extrusive igneous rocks (Figure 9, Plate 1). Lithofacies concealed by igneous extrusives are assumed to be continuous with trends developed further to the south. Table 3 summarizes the relationships between lithofacies and depositional environments.

Tilted Muddy Creek basin bedding sequences are exposed as a two- dimensional north-south trending cross-section. Because the earliest depositional sequences are present only on the west side of the basin and the most recent sequences are present only on the east side of the basin, the east-west distribution of sedimentary facies cannot be seen. The relative stratigraphie position of each measured section within the sequence can be accurately located along form-1ines that parallel bedding plane strike trends (see Figure 3). By bringing form- lines that curve in map view into a parallel alignment, stratigraphie sections located along the contours are horizontally repositioned to better approximate original bedding relationships. In this study, lithofacies correlations are based on repositioned stratigraphie sections (Figure 19). If this cross-sectional alignment were not possible, depositional sequences in the Muddy Creek basin would appear less consistent. Table 3. Summary of Lithofacies and Environments of Deposition DOMINENT LITHOFACIES ENVIRONMENT COMMON SED. FEATURES FOSSILS LITHOLOGY channels, scour/fill rare gastropods trough x-bdg, strat­ Conglomerate and plants Sand/ Alluvial ification Conglomerate Fan even lamination, rare gastropods variable gravel, scour/ Sandstone and plants f i l l massive, even bedding rare vertebrates, Fan-Delta Sandstone ripple x-lam, scour burrows variable gravel, mas­ Oligocene verte­ Mudstone/ Shale/Sand sive, crude bedding, brates, rare gas- Siltstone nodules, small scours tropods, fis c a l,. Shale thin even lamination plants, fish scales Shale thin even lamination rare gastropods and plants Shallow Siltstone/ massive, thick lamina­ rare mollusks Fine Water Mudstone tions, marl lenses and ostracods Tuffaceous Lacustrine Limestone massive, laminated gastropods, burrows massive, irregular ostracods, Marl lamination mollusks

even bedding, Tuffaceous rare plants Silt/Sand small scour/fill

Vi trie Tuff crude bedding rare plants Coarse Debris Flow/ Tuffaceous Fan-Delta Volcanic matrix support, scour/ Conglomerate f i l l LITHOFACIES Sond/Conglomerote

Sand/Shate

Fine Tuffaceous

Coorse TuffoceoüS

4C m 4A,C 3A

78

V V en 7A

Figure 19. North-south stratigraphie correlation of Muddy Creek basin lithofacies Measured sections are identified at the base of each lithology column. 52

In cross-section, the transition between lithofacies is relatively uniform and lateral intertonguing is minor. Such uniformity of deposition suggests a relatively invariable sediment input into the basin. Although minor fluctuations in sediment supply are indicated for all lithofacies, major fluctuations involving broad lateral transgressions and regressions of depositional environments are absent from the sequence except in the highest stratigraphie level. This balance of sediment input with basin subsidence is interpreted to reflect climatic and tectonic uniformity during most of the Muddy Creek basin depositional time span.

Transitions between depositional environments in the Muddy Creek basin are re la tive ly abrupt. Monroe (1981) equates abrupt facies transitions in the upper Ruby River basin with steep regional slopes, and gentle transitions with shallow slopes. This relationship has also been noted in the Uinta basin (Picard and High, 1972; Ryder and others, 1976). Similarly, alluvial fan facies that flank the Muddy

Creek basin have abrupt transitions and steep slopes are indicated, whereas broadly distributed lacustrine and fan-delta deposits in the center of the basin refle ct gentle slopes.

The distribu tion of alluvial fan deposits in the Muddy Creek basin strongly suggests that original basin margins approximated those of the present basin. Alluvial fan sediments apparently flank lacustrine deposits throughout the entire depositional sequence; in itia lly along the western basin margin, then along the southern, and fin a lly , along the eastern basin margin. Laterally extensive distal-fan sediments 53 in the shale/sand facies also suggest a broad north-south d is tri­ bution of alluvial fans that coarsen to the east. Because tilted basin sequences are exposed only in cross-section, however, the potential east-west distribution of lacustrine sediments is only demonstrably limited by alluvial fan deposits during the earliest and latest depositional episodes. Aside from the presence of tuffaceous sediments in areas outside of the present fault-defined basin (see

Figure 9, Plate 1), there is no physical evidence to indicate a wide distribution of lacustrine or alluvial fan sediments.

Depositional History

The timing and geologic processes related to the origin of Muddy

Creek basin are obscure. Original basin margins may have been delineated at any time following Laramide thrusting and prior to the time that early Chadronian (early Oligocene), or slightly older, sediments were deposited in the basin. Possible processes include the erosion of a thrust generated topography and/or the elevation of volcanic highlands. Late Eocene to early Oligocene extensional faulting may also have played a role, since Chadwick (1978) and

Fountain (1981) suggest that Basin-Range style tectonism began in western Montana at that time.

The earliest preserved sediments were deposited when the Muddy

Creek basin was inundated by rh y o litic flows, alluvium, and ejecta

(see Coarse Tuffaceous Facies). Erosive drainage patterns that may have existed prior to that time were lik e ly overwhelmed and closed by 54

the mass of volcanogenic material. The intense volcanic activity

reflected in early Muddy Creek basin sediments appears correlative

with major rh y o litic volcanism in southwestern Montana during latest

Eocene to Oligocene time (Chadwick, 1981). Porphyritic rhyolites

in the Beaverhead Canyon area that are probably sim ilar to those at

the north end of the Muddy Creek basin (Scholten, and others, 1955)

yield a K-Ar date of 38.9 m.y. (Chadwick, 1978).

Lacustrine deposits appear early in the closed Muddy Creek basin;

firs t as rare interbeds within volcanic fan and fan-delta deposits,

and later as thick ash-dominated sequences (see Fine Tuffaceous Facies)

The vertical transition from lake sediments dominated by volcanic

debris to those characterized by clays, sedimentary rock fragments,

abundant plant debris, and vertebrate fossils (see Shale/Sand Facies)

would seem to document the cessation of major volcanic a c tiv ity in

th^m m ediate area. Possible evidence for later volcanism is re­

stricted to rare, localized, ashy shales and thin bentonites. Sedi­

ment input to the basin, which had previously been derived (at least

as far as can be discerned) from volcanic airfall and alluvial

sources to the west, shifted to the southeast and east where alluvial

fans containing Paleozoic and Mesozoic clasts began to prograde onto

lake sediments.

All lacustrine sequences preserved in the Muddy Creek basin re­

flect perennial, shallow water conditions. There is at present no evidence for either deep water or playa-like sedimentation. A lte r­ nating fluvial and lacustrine sediments in the shale/sand facies and 55 variations in bed thickness, color banding and plant debris content suggest some fluctuation in lake level, possible seasonality of sediment and plant debris input, and a rapid, but consistent, develop­ ment of the basin. Basin subsidence and sedimentation were well balanced.

Alluvial facies that are laterally equivalent to, and interbedded with, early Oligocene lacustrine sediments indicate the tectonic and/ or erosional exposure of Paleozoic and Mesozoic rock sources to the east and southeast. The allu vial sequences, which thickened and coarsened to the southeast throughout the time span of lake deposition, rapidly prograded to the north during the final stages of recorded

Muddy Creek basin deposition. The major northward transgression of alluvial fan deposits may reflect tectonic and/or climatic changes.

Although datable fossils are not present, an Oligocene age only s lig h tly later than dated horizons is probable for this alluvial transgression since bedding is gradational with early Oligocene se­ quences in the shale/sand facies.

A few large exotic blocks of Paleozoic and Mesozoic rock, up to several hundred meters wide and f i f t y meters thick, are present within the Tertiary sequence along the east side of the basin (Plate 1). Due to extensive soil cover, however, the precise relationship of these exotic blocks to Muddy Creek basin sedimentary facies is not known.

Apparently, the blocks broke away from the East Muddy Creek fa u lt during the Oligocene to more recent period of normal faulting that defined the present basin margins. 56

The t ilt in g and faulting of Tertiary sequences clearly occurred a fte r the deposition of Oligocene sediments in the basin and prior to the deposition of basaltic flow breccias which overlie tilted

Tertiary beds. The Muddy Creek basin volcanic facies is possibly equivalent to the Medicine Lodge volcanics which underlie Miocene?

Medicine Lodge beds in the Medicine Lodge basin (Scholten, and others,

1955). As radiometric dates are not available, however, the time of extrusion of the volcanics and, therefore, the upper lim it on the timing of basin normal faulting cannot presently be determined. V

REGIONAL CORRELATION AND COMPARISON

A number of intermontane basins in southwestern Montana have been studied in order to document and interpret regional Tertiary history. The stratigraphy, paleontology, structure, and geologic history of individual basin has been discussed by Robinson (1963, 1967,

1961), Dorr and Wheeler (1964), Kuenzi (1966), Rasmussen (1969, 1977),

Hoffman (1971), Kuenzi and Fields (1971), Petkewich (1972), Monroe

(1976, 1981), Hughes (1981), and others.

An overall lithologie similarity between Tertiary sediments of the same age in the separate intermontane basins of southwestern Montana has generally been interpreted to reflect a common geologic history.

As a result, a stratigraphie terminology has gradually been developed fo r southwestern Montana which assigns a ll Tertiary b a s in -fill deposits to the Bozeman Group (Robinson, 1963). Further stratigraphie sub­ division includes the upper Eocene (Uintan) to lower Miocene (Heming- fordian) Renova Formation and its local lithofacies (Kuenzi and Fields,

1971) and the lower middle Miocene (Barstovian) to Pliocene

(HemphiIlian) Sixmile Creek Formation (Robinson, 1967), (Figure 20).

The Renova Formation, a sequence of fine-grained tuffaceous sedi­ ments containing only minor conglomerates, rests unconformably on lower Tertiary to Precambrian rocks (Dorr, 1956; Robinson, 1963;

Dorr and Wheeler, 1964; Robinson, 1967; Kuenzi and Fields, 1971). In

57 58

CO O ü - lO

uf c

^2

a.

u o H- m

Q. _ l — C 3E — O o ijJ z uj 0 _ J — CDOOüJ ZLU UJ O OUJ ZLÜ o O c\i ro lO Figure 20. Stratigraphie framework of selected Tertiary basins. Modi­ fied after a compilation by A.R. Tabrum. Generalized column modified from Thompson, e^ , 1981. Epochs and ages follow Lillegraven, ^ , 1981. Previous studies: 1, Kuenzi and Fields, 1971; 2, Monroe, 1976; 3, Petkewich, 1972; 4, 5, Robinson, 1963, 1967. 59 turn, the overlying Sixmile Creek Formation, characterized by much coarser sediments is, where studied to date, unconformable on the

lower sequence. This erosional and angular unconformity has been documented to extend throughout late early Miocene (Hemingfordian) time (Robinson, 1960, 1961, 1963, 1967; Kuenzi and Richard, 1969;

Kuenzi and Fields, 1971; Rasmussen, 1973). Epoch and North American

land mammal age boundaries follow Lillegraven and others (1981).

Lithologie Correlation — Renova Formation

Early Chadronian (approximately latest Eocene to early Oligocene)

Muddy Creek basin sediments correspond in general lith olog ie character and age to the broadly defined Renova Formation (Kuenzi and Fields,

1971). The correlation and assignment of Muddy Creek basin sediments to a formally named member of the Renova Formation is, however, not warranted.

The Climbing Arrow and Bone Basin members of the Renova Formation are of somewhat sim ilar lithologie type and comparable age to Muddy

Creek basin sediments (Figure 20). Robinson (1963) o rig in a lly defined the Climbing Arrow in the Three Forks basin as the Climbing Arrow

Formation. He described the type sediments as "olive, thick bedded, sandy, bentonitic clay and coarse sand with subordinate light colored siltston e, sandstone, conglomerate, and limestone" (Robinson, 1963: p. 69). Robinson (1967) later extended this terminology into the

Toston quadrangle and the Canyon Ferry basin on the basis of lithologie s im ila rity and approximate age equivalence. He noted, however, that 60 in the Toston quadrangle. Climbing Arrow Formation sediments d iffe r somewhat from those in the Three Forks basin; red and purple colors predominate, lig n ite and paper shale are present, and sandstone is scarce.

Kuenzi and Fields (1971) further extended Climbing Arrow termi­ nology into the Jefferson River basin where they designated mudstones and le nticu la r sandstones of Oligocene age as the Climbing Arrow Member of the Renova Formation. The Climbing Arrow Member was subsequently recognized in the Beaverhead basin (Petkewich, 1972) and the upper

Ruby River basin (Monroe, 1976).

The Bone Basin Member (Kuenzi and Fields, 1971) has been described only in the Jefferson River basin. The type section includes "an alternating sequence of mi critic and oolitic limestone, montmoril- lonite mudstone, v it r ic siltstone, v itr ic arenite, arkose, and minor conglomerate" (Kuenzi and Fields, 1971: p. 3380).

Muddy Creek basin sediments have been subdivided into five lith o ­ facies (see Stratigraphy and Depositional Environments section). None of these lithofacies appear sim ilar to the Bone Basin Member and only the shale/sand lithofacies resembles, in general, sediments assigned to the Climbing Arrow Member in other basins. The shale/sand facies is recognizably d iffe re n t, however, from type Climbing Arrow sediments in the Three Forks basin in overall lith olog ie composition and texture

(personal observations). Furthermore, sediment distribution patterns in the Muddy Creek basin suggest a discrete depositional basin, and the geographic separation of Muddy Creek basin sediments from basins 61 in which the Climbing Arrow member has been recognized (Figure 1) may rule out a direct interrelationship between sediments.

Tectonics, Climate, and Sedimentation

Several studies have suggested that the present distribution of intermontane basins in southwestern Montana represents a middle to late

Tertiary fragmentation of more extensive earlier basins (Mann, 1960;

Myers and Hamilton, 1964; Wolfe, 1964; Hamilton and Myers, 1966;

Rasmussen, 1977; and Reynolds, 1979). Thompson, ^ a%., (1981) have further suggested that southwestern Montana was covered by a semi- continuous sheet of Renova Formation sediments prior to late early

Miocene (Hemingfordian) time when a regionally synchronous tectonic event produced an erosional and angular unconformity and delineated individual basins much as they exist today.

Muddy Creek basin sediments appear to have been deposited in only a re la tive ly short period of the time during which the Renova

Formation (and equivalents) were deposited (see Figure 20). Never­ theless, the geologic history of the Muddy Creek basin suggests that present basin margins approximate those of the original basin of deposition, and that basin development was persistent. Hence, early Oligocene Muddy Creek basin sedimentation does not appear con­ sistent with the regionally extensive sedimentation patterns suggested by Thompson, et al- (1981).

The age of the tectonic episode that tilte d Muddy Creek basin beds cannot be accurately determined; as i t may have occurred as early as 62

Oligocene time, i t could possibly coincide with the early Miocene

event that produced the mid-Tertiary unconformity in other basins.

Evidence for clim atic control over Renova Formation sedimenta­

tion is somewhat equivocal. Kuenzi (1974) and Rasmussen (1969, 1977)

have postulated a relatively humid climate with well developed

drainage patterns for southwestern Montana west of the continental

divide. Thick, non-playa lake sediments have been described in the

upper Ruby River basin (Monroe, 1976, 1981) and Beaverhead basin

(Petkewich, 1972). Becker (1969) interpreted the Christensen Ranch

Florule from the Beaverhead basin as representative of a high a l­

titude, sub-humid micro environment.

A lt and Fields (1971), Fields (1972) and Thompson et aj[., (1981)

have, however, postulated that Renova Formation sediments accumulated

predominantly in an arid to semi-arid environment where sediment

production overburdened drainage systems. Thompson ^ , (1981)

note that regional sediment distribution patterns, clay mineralogy,

vertebrate faunal assemblages, and globally synchronous fluctuations

in Tertiary deep ocean sediments a ll suggest a semi-arid climate from

late Eocene to early Miocene time.

Indications of paleoclimate in the Muddy Creek basin are also

equivocal. Although the flo ra l assemblage indicates an environmen­

ta lly stressed but moist micro-paleoenvironment and the perennial lake

sediments preclude extreme drying conditions, the smectite-dominated

clay mineralogy and presence of allu vial fan sediments are consistent with (but not exclusive to) the semi-arid model proposed by Thompson 63 and others (1981). As l i t t l e is presently known about Oligocene

vertebrate paleoecology, the Muddy Creek basin vertebrate fauna is not

regarded as environmentally specific. Hence, moist conditions may

have been localized in the Muddy Creek lake basin.

In a ll, the conflicting evidence regarding paleoclimate and

sedimentation during the Renova Formation time span suggests the

p o s s ib ility of wide geographic v a ria b ility in climate and patterns

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Vessel 1, R.K., and Davies, O.K., 1981, Nonmarine sedimentation in an active fore arc basin, i_n: F.G. Ethridge and R.M. Flores, eds.. Recent and Ancient Nonmarine Depositional Environments: Models for Exploration: Soc. Econ. Paleontologists Mineralogists Spec. Pub. 31, p. 31-45.

Wallace, S.R., 1948, Geology of part of the Tendoy Mountains, Beaverhead County, Montana: Unpub. M.S. Thesis, Univ. Mich., 56 p.

Wilson, M.D., 1967, The stratigraphy and origin of the Beaverhead Group in the Lima area, southwestern Montana: Ph.D. Thesis, Northwestern Univ., 171 p.

, 1970, Upper Cretaceous-Paleocene synorogenic conglomerates of southwestern Montana: Am. Assoc. Petrol. Geol, B u ll., v. 54, p. 1843-1867.

Winchester, D.E., 1923, Oil shale of the Rocky Mountain region: U.S. Geol. Survey Bull. 729, 202 p.

Wolfe, P.L., 1964, Late Cenozoic u p lift and exhumed Rocky Mountains of central western Montana: Geol. Soc. America B u ll., v. 75, p. 493-502. APPENDIX

Measured Sections

Twenty stratigraphie sections were measured at 12 locations in

the Muddy Creek basin (Figure 10, Plate 1). Sections 1,2,3,4,7,

and 11 are composite sections. Probable correlation points between

these composite sections are noted on the drafted lithology columns.

Drafted lithology columns contain a weathering pro file . Section

thickness is measured in meters above section base. A key to

lithology and structure symbols is on page 75.

Sections 6, 9, 11 and 12 were measured for correlation purposes.

As lith o lo g ie descriptions are redundant, those sections are repre­

sented only in illustrated form.

Lithologie descriptions are based on both field observation

and binocular microscope examination of samples taken at each desig­

nated unit of key sections. Descriptions are generally given in the

following order: rock name, color, grain size, sorting, composition,

angularity, sphericity, cements, induration, sedimentary structures

and other. Rock names are derived from the classification diagrams

illu s tra te d on pages 76 & 77. Rocks colors comply with the "Rock-Color-

Chart" (Goddard and others, 1979). Sorting, angularity, sphericity, and grain size terminology follows Folk (1974). Stratigraphie thick­ ness follows Ingram (1954). Subjective compositions are scaled from rare to common to abundant to vary abundant. A key to abbreciations

73 74 used is included on page 78 . Dimensions given for lenses and bedding structures assume a greater lateral dimension unless otherwise noted. 75

KEY TO LITHOLOGY AND SEDIMENTARY STRUCTURE SYMBOLS

Lithology Structure

Sn tstone Irregular Lamination

Sandstone Lenses

Marl Interbeds

Conglomerate Trough x-bedding

Mudstone Cross-1 ami nation

Mud Shale Horizontal lamination

S ilt Shale Tabular structures

/ '' / Porcellani te Massi ve ^ / X. / __N, / s. Ash Shale laminae

Tuff Discontinuous laminae

Cl aystone Nodules

Limestone

Cherty Limestone

Calcareous Si 1tstone

7777? Gypsum

Pebbly Siltstone/Mudstone . » 76

m . Quartzarenite Subarkose Sublitharenite

Lith ic Subarkose

Arkose Litharenite L ith i c Arkose Feldspathi c Lithareni te

Felds LR£

Figure 21. Sandstone classification. Modified from McBride, 1963

Gravel

conglomerate

muddy cgl sandy cgl muddy, sandy cgl pebbly mudstone pebbly muddy sand pebbly sanditSRi Sand

sandy muddy sandstone mudstone mudstone sandstone

Figure 22. Clast mixture classification. Modified from Folk, 1974. 77

Sand sandstone

s ilty sandstone

sandy siltstone

Tr

claystone mudstone tstone

Figure 23. Clay, s ilt , sand mixtures. Modified from Folk, 1974.

silicio us limestone limestone calc chert Carbonate \ / chert limestone Silica

sandy ^ 1i mestone muddy -V - porcellani te 1imestone

marl

Sand mudstone calc sandstone mudstone mudstone

Figure 24. Carbonate, s ilic a , sand, mud mixtures Modified from Gilbert, 1954. 78

KEY TO ABBREVIATIONS abund abundant med medi urn ang angular Mg magnesi urn app approximately mod moderate (ly) av average MP Montana Plant Locality MV Montana Vertebrate Locality bdg bedding bid bladed pbl pebble bldrs boul ders pel pelecypod brng bearing PD plant debris

cal c calcareous qtz quartz cbl cobble rd round cgl conglomerate comp compact s ilts t siltstone concr concretion sm smal 1 crs coarse srtd sorted subrd subround di am diameter

th rt throughout exp exposure

V very Fe i ron vert vertebrate felds feldspar vole volcani c frags fragments VRF Volcanic Rock Fragment gast gastropod vf very fine gran granules x-beds cross-beds g y p gypsum x-lam cross-laminae i rreg i r regular xtal crystal lam 1 ami nae LRF lith ic rock fragment SECTION 1

8 0

to

Shale/Sand Facies

TV -SO

'Sr

'20

!S

'tO

//? 80

U n it/ SECTION 1-A Interval

21.45- 9 Mud Shale, lig h t brown (SYR 6/4) to lig h t brown gray 28.55 (5YR 6/1), 5% crs LRF sand, rd, comp. PD abund along lam, variable fissility.

21.4- 8 Small Pebble Conglomerate, gray orange (10 YR 7/4), 21.45 poorly srtd, 60% sm LRF pbls, subrd, comp/bld, in matrix of mod well srtd fine to med felds litharenite, subang, comp. S lightly calc cement, mod well indurated, Fe stain thrt.

18.1- _7 Fossiliferous Mudstone, pale green yellow (lOY 8/2), 21.4 mod well srtd, rare LRF gran and med qtz sand th rt, (MV) subrd, comp. Calc cement, mod well indurated, gyp rare along joints, abund vert fossils, gast and pel fossils rare th rt, chalky calc concr 5mm to 3cm diam, rare PD th rt.

18- 6^ Fossil iferous Pebbly Felds Li thareni te, yellow gray 18.1 (5Y 7/2), mod well srtd, 5% LRF pbls th rt, vert bone (MV) scrap common, rare PD thrt. Unit mod well indurated, silica cement. Faint very thin x-lam as channel fill in 5cm X 15cm lenses and as irreg bdg.

10- ^ Fossil and Concretion bearing Granule Siltstone, pale 18 yellow brown (lOYR 6/2), mod well srtd, 5% LRF gran (MV) th rt, subang, comp/bld, concr to 5cm diam of lith a re n ite, poorly srtd, med sand to sm pbls in s ilt matrix. FeO cements, massive, sligh t f is s il it y th rt with rare PD, rare concr, vert foss common, rare gyp xtals thrt, mod poor exp,

9.7- ^ Pebble Conglomerate Marl, yellow gray (5Y 8/1), well 10 srtd in irreg lenses. LRF pbls to 4cm, subang, comp, with marl matrix. Irreg bdg with irreg cgl lenses thrt av 10cm X 15cm. Gran size pel imprints th rt marl. Fe stain weathering in patches.

5.2- 3 Pebbly Sandy Siltstone, similar to Unit 1. 9.7 81

U n it/ SECTION 1-A In te rva l

5- ^ Gastropod bearing Silty Feldspathic Litharenite, 5.2 medium gray (N5) to pale olive (lOY 6/2), mod well srtd, (20% ash th rt), v fine to med sand, subang, bid to comp. Unit mod well indurated, slight calc cement. Lenses th rt ranging from 2cm X 4cm to 4cm X 10cm filled with mod well srtd med litharenite, subang, bid, or sand and to 80% pbl size gastropods.

0- 2 Pebbly Sandy Siltstone, pale olive (lOY 6/2), prly 5 srtd. Pbls LRF, subang, comp. Sand as sublitharenite, subang, comp. Unit poorly indurated, calc cement, massive, poor exposure. 82

U n it/ SECTION 1-B In te rva l

52.05- 92.5 J_3 Mud Shale, sim ilar to Unit 7. Gyp as radial xtals common, thick lam th rt, rare ashy mud shale lam.

51.35- J_2 Ashy Sandy Siltstone, similar to Unit 10. 52.05

41.65- Mud Shale, sim ilar to Unit 7. Variable f is s ilit y 51.35 thrt, rare lenticular siltst to 10cm thick.

41.5- J_0 Ashy Sandy Siltstone, light olive gray (5Y 6/1), mod 41.65 well srtd s i l t to v fine sand, 15% LRF, 20% pumice as med sand, subrd, comp. PD common. Unit mod well indurated, calc cement. Thin lam rare, otherwise massive

34.1- ^ Ashy S ilt Shale, pale brown (5YR 5/2), sim ilar to 41.5 Unit 7 but with crs sand size pumice frags and PD along bdg lam. Radial gyp in jo in ts and organic resin stringers thrt.

33.9- 8 Feldspathic Litharenite, lig h t gray (N7), mod well 34.1 srtd fine-med sand. Qtz and felds subrd, comp. LRF subang, comp/bld. Rare thick lam of sm pbl lith a re n ite; pbls LRF, subang, comp, irreg bases. 5mm th in ly bedded sandy s ilts t layer with abund PD overlain by columnar gyp layer 8cm thick. Unit mod well indurated, silica cement, radial gyp in joints, Fe stain th rt. Broadly lenticular laminae.

28.1- 2 Mud Shale, pale brown (5YR 5/2) to grayish orange 33.9 (lOYR 7/4). Subtle color variations thrt. Variable PD on bdg surfaces becoming lig n itic in 5mm bands th rt. Dusky yellow (5Y 6/4) FeO powder common on laminae.

27.8 6^ Lith ic Subarkose, yellow gray (5Y 7/2), mod well srtd 28.1 fine sand, subrd, comp/bld. To 5% med LRF sand, Subang, comp, and PD. Lenses 4cm X 10cm of sandy pbl cgls, LRF med sand to sm pbl, subang, comp/bld in fine sand matrix. Unit well indurated, silica cement. Lenses with slightly irreg contacts, Fe stain thrt and 5cm diam FeO nodules common th rt. 83

U nit/ SECTION 1-B Interval

19.3- ^ Fossiliferous Siltstone, yellowish gray (5Y 7/2). 27.8 Rare 4mm diam concretions, vert fossils common. (MV) To 15% mica flakes. Unit mod well indurated, thin lam thrt with Fe stain along lam and joints.

18.8- ^ Pebbly Litharenite, pale olive (lOY 6/2), mod well 19.3 srtd fine sand, subrd, comp. To 5% LRF crs sand to sm pbls, subang, bid. To 5% sm pbl size PD. Unit mod well indurated, calc cement, crude bdg thrt with rare concentrations of crs clasts and PD along bdg lam.

15.6- ^ Mudstone Semi-Shale, moderate brown (5YR 4/4). To 5% 18.8 fine LRF sand thrt, rare PD. Unit fissile as flakes, otherwise massive.

15.3- 2 Ashy Feldspathic Litharenite, lig h t gray (N7), mod 15.6 well srtd v fine to fine sand, to 5% med sand and sm pbls. Lenses av 4cm X 15cm and 1cm diam pods th rt of med sand, 60% LRF, mod well srtd, subang, comp. Unit mod well indurated thrt, calc cement, v irreg bdg contacts and tonguing of med sand lenses,

0- J_ Pebbly Sandy Mudstone, pale olive (lOY 6/2), poorly 15.3 srtd, to 10% LRF fine sand to sm pbls, ang to subrd, bid. Unit poorly indurated, patchy calc cements, massive. Rare PD and calc concr, Fe staining th rt. 84

2 .3

L SECTION 2 Z9 z c E3”E 3^ — q O 0 “ :

% 6

_ _*A* y» ------

Shale/Sand faciès

20, 'Teo

3 0

2 ./i 9 \ ------» \ 7 \ s

--- 4! \ ------1 2 C 85

I* IT

ts- SECTION 2

Shale/Sand facies

z c 86

U n it/ SECTION 2-A In te rva l

17.4- ^ Mudstone, sim ilar to Unit 7, yellowish gray 20.4 (5Y 7/2).

16.2- ^ Mud Shale, sim ilar to Unit 6, poor exposure. 17.4

11.7- _7 Mudstone, gradational yellow gray (5Y 7/2) to 16.2 lig h t brown(5YR 6/4). Gradational f is s ilit y becoming siltier and less fissile at top of unit. To 5% med sand size PD thrt, rare 3cm organic clots. Fe stained jo in ts .

10.7- ^ Mud Shale, grayish orange (lOYR 7/4). Massive, to 11.7 3% organics and fish scales, weathers to paper flakes, mod well indurated.

7.4- ^ Interbedded Siltstone and Litharenite, yellowish gray 10.7 (5Y 7/2). Siltst variable to 10% PD. Litharenite as V fine sand, well srtd, subrd, comp. Sand poorly indurated, interbeds irreg and gradational, grades into Unit 6.

5.6- ^ Mud Shale, lig h t brown (5YR 6/4). Massive, grades 7.4 into and out of .4m PD mud shale sim ilar to Unit 2.

3.9- _3 Siltstone, similar to Unit 1. Rare organic concr 5.6 in irreg 5cm clots.

1.9- 2 Mud Shale, pale yellowish brown (lOYR 6/2). 3.9 Slightly irreg thin fissile bdg lam, to 50% PD along lam. Unit mod well indurated.

0- ]_ Siltstone, yellowish gray (TY 7/2). Massive, 1.9 s lig h tly fis s ile , weathers as chips, clay cement, slight Fe staining on joints. 87

U n it/ SECTION 2-B Interva l

103- ^ Mudstone, sim ilar to Unit 16. 109.5

81.5- Nodule bearing Sandy Mudstone, subtle 1.5m color 103 bands from yellowish gray (5Y 7/2) to lig h t brown (5YR 6/4). 15% poorly srtd LRF fine to med sand (qtz rare), subrd, comp, rare vole clasts. Dense subrd calc nodules 4mm to 6cm diam 10% th rt in .5m X 1.5m irreg lenses with top 2m of unit 40% nodules. Mg stain weathering on nodules.

80.3- ^ Cobble Conglomerate, lig h t gray (N7) coating matrix. 81.5 Poorly srtd, 80% grain supported LRF and chert clasts - sm pbl to sm boulder, (cbls most common), rare limestone clasts. Clasts subang to ang, comp to bid. Mud matrix sim ilar to unit below. Massive, very poorly indurated.

63.7- ^ Mudstone, gradational color banding. App 2.5m dark 80.3 yellowish orange (lOYR 6/6), 8.6m dusky yellow (5Y 6/4), 3m pale olive (5Y 7/6), 2.5m grayish orange pink (5YR 7/2). Unit massive within bands.

62.3- _2§. Mud Shale, similar to Unit 20. 63.7

59.1- ^ Siltstone, similar to Unit 19. Top .5m grades to 62.3 pale olive (lOY 6/2).

56- 21 Mudstone, yellowish gray (5Y 7/2), rare med LRF 59.1 sand to sm pbls, rd, comp. Unit massive, Fe stain along jo in ts th rt, rare pbl size PD.

54.2- 22 Mud Shale, sim ilar to Unit 20. 56

52.7- 22. Interbedded Siltstone, sim ilar to Unit 17 and 54.2 Mudstone similar to Unit 20. Interbeds gradational, app .5m thick.

51.7- 21 Mud Shale, pale red (5R 6/2), abund PD but less 52.7 than Unit 18.

49- 21 Siltstone, dark yellowish orange (lOYR 6/6), otherwise 51.7 similar to Unit 17. 88

U n it/ SECTION 2-B In te rva l

48.4- T_8 Mud Shale, grayish red (5R 4/2). Very abund PD 49 becoming lig n itic in 10cm bands th rt.

43.6“ V7 Siltstone, pale olive (lOY 6/2) at base grading to 48.4 dark yellowish orange (lOYR 6/6). To 5% subrd LRF pbls, rare PD th rt. Unit massive, Fe stain th rt with increase in upper unit.

35.8“ %6 Mudstone, very pale orange (lOYR 8/2) to pale olive 43.6 (lOY 6/2). Massive, in d istin ct color banding f ir s t 3m becoming v pale orange above.

33.1“ Interbedded Mudstone and Mud Shale, sim ilar to units 35.8 below. Shale interbeds av .4m thick, mudstone beds .6m thick.

30.2“ J_4 Mud Shale, sim ilar to Unit 6. Abundant PD with 33.1 color and PD variations app every .5m.

26.5- 1_3 Mudstone, sim ilar to Unit 9, subtle color banding 30.2 thrt. .3m lenticular siltstone similar to Unit 2. .5m from top of unit.

26.2- j_2 Nodule bearing Claystone, very pale orange (lOYR 8/2) 26.5 to pale greenish yellow (lOY 8/2). 80% dense, irreg calc clay nodules from 4mm to 10cm diam. Matrix calc claystone. Mg stain weathering on nodules, nodules well indurated, matrix poorly indurated.

21- JJ_ Mudstone, sim ilar to Unit 1. 26.2

20.1- 20 Sandy Claystone, yellowish gray (5Y 7/2). To 10% 21 prly srtd med sand to sm pbls th rt, subrd, bid. Unit massive, carbon stained jo in ts.

17.3“ 2 Mudstone, sim ilar to Unit 5. App 5% small LRF 20.1 pbls th rt.

16.7“ S Siltstone, similar to Unit 2. 17.3

14 . 7- 7_ Mudstone, sim ilar to Unit 5. 16.7 89

U n it/ SECTION 2-B In te rva l

12.2- 6^ Mud Shale, color banded in ,5m beds - grayish yellow 14.7 (5Y 8/4) to grayish red (lOR 4/2). Variable PD from 5% to lignite. Variable fissility from paper shale to 5mm irreg partings. Fe stain on less fissile beds, darker beds = greater fis s ility and PD.

9.5- S_ Mudstone, dusky yellow (5Y 6/4) to pale brown 12.2 (5YR 5/2) otherwise similar to Unit 1.

8.9- ^ Muddy Feldspathic Sublitharenite, dusky yellow 9.5 (5Y 6/4), well srtd fine sand, mod well rd, comp. Rare crs sand and PD. Poorly indurated, massive.

5.2- 2 Mudstone, similar to Unit 1. 8.9

4.5- ^ Siltstone, moderate orange pink (5YR 8/4), rare fine 5.2 to crs sand size PD, very irreg fissile lam app 5mm thick thrt.

0- 1_ Mudstone, grayish orange pink (5YR 7/2) to dark 4.5 yellowish brown (lOYR 4/2). Color banded bdg av Im thick, massive within beds, darker beds with common PD, lig h te r beds with FeO along joints. 90

U n it/ SECTION 2-C Interva l

96.85- Ashy Siltstone, similar to Unit 15. 103

96.55- 96.85 1_6_ Sublitharenite, very pale orange (lOYR 8/2), well srtd fine sand, subrd, comp. Unit massive, mod well indurated, silica cement.

91.85- J_5 Ashy Siltstone, very lig h t gray (N8), rare PD 96.55 th rt. Massive, weathers as 3mm thick chips.

76.35- Ashy Mudstone, light olive gray (5Y 6/1), rare 91.85 PD as impressions, wavy irreg lam. Rare lenses 3cm X 30cm of med litharenite, mod well srtd, subang, comp. 5mm thick abrupt upper surface on lenses of 50% LRF granules, subang, bid; 30% pel and 20% litharenite.

75.65- Pelecypod bearing Calcareous Siltstone, lig h t 76.35 olive gray (5Y 6/1), 10% pel poorly srtd thrt, to 5% PD thrt. Unit massive, mod well indurated, calc cement. Unit somewhat lenticular with bdg thickness variable to .3m.

33.15- %2 Interbedded S ilt Shale sim ilar to Unit 9 and 75.65 Mudstone sim ilar to Unit 6. Interbeds .2m to 1.5m thick. Rare gyp xtals thrt, rare concentrations of gyp and Fe stain in 5cm thick horizons. Mod poor exposure.

33- JJ_ Litharenite Granule Conglomerate, moderate brown 33.15 (5YR 4/4), poorly srtd, 30% LRF and 20% qtz granules in fine-med sand, subrd, comp/platey. Rare LRF med pbls, 20% mud matrix. Unit massive, s lig h tly- irreg top and bottom contacts, mod well indurated, Fe stain thrt extending 15cm into overting unit. Unit thickness varies by 10cm.

31.7- jO. Sublitharenite, very pale orange (lOYR 8/2), mod 33 well srtd, fine sand, subrd, comp. Rare crs LRF sand concentrated as 10% of 3cm diam subrd patches thrt. PD common as impressions. Thick horizontal lam with thin x-lam in lenses 30cm X 10cm, s lig h tly irreg base. 91

U n it/ SECTION 2-C In te rva l

30.5- 31.7 £ S ilt Shale, pale red (lOR 6/2), sim ilar to Unit 7 but less PD,

29.8- 30.5 S Muddy Pebble Conglomerate, grayish orange (lOYR 7/4), poorly srtd, LRF (80% sandstone, 20% a rg illite ) crs sand to sm cbls (med pbls most common) subrd, comp to bid. Sandy mud matrix. Grain support, prly indurated. Gyp xtals th rt and as pbl coatings. Sharp bdg contact with underlying unit.

28.4- 7_ S ilt Shale, lig h t brown (5YR 6/4) to dusky brown 29.8 (5YR 2/2), PD very abund along lam becoming lig n itic in 4cm thin bdg.

23.9- £ Vertebrate bearing Mudstone. Gradational color banding 28.4 as grayish orange (lOYR 7/4) to pale yellowish green (MV) (lOGY 7/2). Rare LRF and vole sm pbls, subrd, bid. To 5% PD thrt* 1 cm to 10cm diam Fe stained gyp nodules and elongate masses common. Vert fossils very abund, especially in central portion of unit. Unit massive, Fe stain along jo in ts.

14.4- 5_ Siltstone, pale olive (lOY 6/2), rare LRF and vole crs 23.9 sand to sm pbls, subrd, bid. Very rare crs sand size PD. Mica flakes common th rt s ilt . Massive.

12.9- £ Sublitharenite, grayish yellow (5Y 8/4), well srtd med 14.4 sand, subrd, comp. To 15% lig h t Fe stain th rt. Unit massive, clay cement, poorly indurated.

12.5- 3 Pebbly Siltstone, yellowish gray (5Y 7/2), wavy irreg 12.9 bdg, 3cm X 10cm irreg lenses along bdg of LRF and chert fine sand to sm pbls, subrd, comp. To 50% gast and well rd intraclasts of fine to med sand, well srtd, subrd, comp. Rare pel th rt. Calc cement, unit well indurated. 92

U n it/ SECTION 2-C Interva l

5- 2 Siltstone, yellowish gray {5Y 7/2), PD very common 12.5 and poorly srtd. Fe stain weathering on joints. Irreg 1.5m bed near top of unit with calc cement and rare lenses 4cm X 15cm of Pebbly Mudstone to 15% LRF and vole crs sand to sm pbls, subrd, comp. Unit massive overal1.

0 - Mudstone, grayish green (5G 5/2), rare LRF crs sand to 5 sm pbls, subrd, comp. Dense subrd calc nodules 2mm to 5cm th rt. Mg stain on nudules. Unit massive, mod poor exposure. 94 SECTION 3

"60 60 Sand/ Conglomerate Facies 20

70

23 \ Shale/Sand Faciès

/ \ 'SO

2 7

'lo

Jt

. 3 3 I 94

U n it/ SECTION 3-A Interval

76.6- ^ Mudstone, lig h t gray (N7), thin lam and fine sand 82.6 size PD common th rt. 5cm diam Fe stain patches. Unit weathers as 1mm flakes.

76.4- ^ Pebbly L ith ic Subarkose and Pebble Conglomerate, lig h t 76.6 brown (5YR 5/6), sandstone poorly sorted, subrd, to subang, comp to bid, fine sand, to 20% granules and pbls, normally graded. Cgl as graded, 20% gran and pbls of LRF, mud chips and ash. PD common th rt. Cgl as steep scour .2m wide Fe stained, grain support, massive.

73.8- ^ Interbedded Mudstone and Sandstone, sim ilar to Unit 19, 76.4 as irreg 5cm, thin massive beds in mudstone. Poor exposure.

73.6- T9 Pebbly L ith ic Subarkose, sim ilar to Unit 15, poor 73.8 exposure.

69.4- J[8 S ilt Shale, pale brown (5YR 5/2), variable f is s ilit y , 73.6 abund PD, grades to sandy siltstone in central Im of unit with to 40% v fine qtz sand, subrd, comp, mod poor exp

69.1- 1_7 Sublitharenite, yellowish gray (5Y 7/2), mod well srtd, 69.4 fine to med sand, subrd, comp. To 5% crs sand size PD. Crude lenses 5cm X 20 cm with 50% crs sand and PD. Mod well indurated, calc cement, poor exposure.

51.6- J_6 Interbedded Mudstone, very pale orange (lOYR 8/2) and Mud 69.4 Shale, pale yellowish brown (lOYR 6/2). Mudstone with rare PD and thin lam. Mud Shale with abund PD and rare 5cm thick Fe stain bands. Mod poor exposure.

47.6- 25 Pebbly L ith ic Subarkose, yellowish gray (5Y 7/2), mod 51.6 well srtd, fine sand, rd, comp, to 7% sm LRF pbls th rt, subang, comp/bld. Med bdg, thin x-lam, PD along bdg planes and as branching 1mm dia X 5 cm tubules. 2cm thick Fe stained band at top of unit. Unit mod well indurated, pinches out as 100m lense. 95

U n it/ SECTION 3-A Interva l

42.2- J4 Mud Shale, grayish orange pink (5YR 7/2) grading 47.6 upwards to dark yellowish brown (lOYR 4/2). Rare PD increasing upwards to semi-1 ignite, yellow Fe stain common along lam, gyp common as clusters tangential to bdg or as 3cm diam masses.

41.8- J_3 L ith ic Subarkose, very pale orange (lOYR 8/2), poorly 42.4 srtd fine to crs sand. Fine to med sand subrd, comp. Crs sand 80% LRF, subang, bid. Rare PD as sand size to 2cm X 5cm frags, silica cement, well indurated, massive.

39.6- 12 Mud Shale, pale brown (5YR 5/2) grading up to very pale 41.8 orange (lOYR 8/2). Thin lam in thin beds becoming less fis s ile upwards. Rare PD and to 5% fine sand th rt.

38.8- 21 Sublitharenite, pinkish gray (5YR 8/1), well srtd 39.6 fine-med sand, subrd, comp. Silica cement, very well indurated. Fe stain mottling and wavy med horizontal beds 10-25cm thick th rt.

37.4- 21 Granule Sublitharenite, yellowish gray (5Y 8/1), mod 38.8 well srtd, fine-med sand subrd, comp to bid. To 20% LRF and chert th rt, to 10% LRF granules to 5mm, subang, bid. Crude lenses 5cm X 30cm of crs sand to sm pbls. S ilica cement, mod well indurated, Fe stained wavy 2mm, thin lam, crude low angle x-lam in 5cm X 30cm sets th rt.

30.5- 2 Muddy Sublitharenite, yellowish gray (5Y 7/2) to dark 37.4 yellowish orange (5YR 6/6). Well srtd, 60% v fine sand, subrd, comp, 40% mud matrix. Gyp common th rt as crs sand size xtals or stringers and 10mm diam concretions. Unit poorly indurated, Fe stain 15cm thin lam and pbl size patches, and crude thin lam thrt. Broad gradational color bands app. 1.5m thick. 96

U n it/ SECTION 3-A In te rva l

24.8- 8 Quartzarenite, yellowish gray (5Y 7/2), mod well srtd, 30.8 V. fine to fine sand, subrd, comp. To 5% LRF and qtz crs sand. Calc cement, poorly indurated; thin, grain size sorted, laminae th rt. Rare .5m concr masses in 15cm horizon Im from top of unit. Concretions 80% qtz, 20% LRF gran and sm pbls, calc cement. Rare Fe stain as pbl size spots.

24.4- 2_ BoulderConglomerate, sim ilar to Unit 6 with 50% bldrs 24.8 to .4m, 40% med to large cbls, 10% pbls to v crs sand.

Cover - Im

22.4- 6 Cobble Conglomerate, yellowish gray (5Y 7/2), poorly 23.4 srtd, 60% cbls, 30% pbls, 10% bldrs to 5m. Clasts 90% qtz sandstone, 10% limestone, comp/bld. Matrix pebbly lith ic subarkose with chert, subrd, comp. Unit mod well indurated, calc cement, Fe stain on matrix thrt, grain support. Unit thickness varies by .2m, slightly irreg basal contact at times grading into underlying unit.

21.6- ^ Pebbly L ith ic Subarkose, yellow gray (5Y 8/1), mod well 22.4 srtd fine sand, rd, comp. To 10% LRF gran to med pbls th rt, subang, comp/bld. Unit massive, pbl size Fe stain thrt, pbls poorly concentrated in indistinct lenses. Unit mod well indurated, calc cement.

8.6- ^ Subarkose, pale greenish yellow (lOY 8/2), well srtd fine 21.6 sand, rd, comp. Rare lenses th rt .2m X 1.2m of Pebbly Arkose, grayish orange (lOYR 7/4), mod well srtd, fine- med sand, subrd, comp with to 10% LRF gran and sm pbls, subrd, bid, thrt. Subarkose mod well indurated, mud cement. Arkose well indurated, calc and Fe cement.

7.6- _3 Cobble Conglomerate, grayish orange (10 YR 7/4), grain 8.6 supported lenses of fine sand sim ilar to units 1 and 2, and sandy pbl cgl. Clasts LRF (80% sandstone, 20% lime­ stone), ang to rd, comp. Unit 90% cbls in silty sub­ arkose matrix. Base of unit scours to .5m deep X .8m wide into unit 2. 97

U n it/ SECTION 3-A In te rva l

7- ^ Pebbly Quartzarenite, yellowish gray (5Y 7/2), mod 7.6 well srtd fine sand, to 10% LRF and qtz granules to sm cbls th rt, subang, bid. 4cm X 30cm lenses common of 60% LRF sm pbls to sm cbls, subang, bid to platey in sand matrix. Unit mod well indurated, calc mud cement, occasional pbl imbrication to SE.

Cover - 3.7m

0- 2 Pebbly Subarkose, grayish yellow (5Y 8/4), mod well 3.3 srtd V fine sand. To 5% sm LRF pbls, subrd, comp, th rt. Unit with v thin lam, calc mud matrix, poorly indurated 98

U n it/ SECTION 3-B Interva l

78.7- Interbedded Quartzarenite and Mud Shale with Cobble 134.7 Conglomerate. Quartzarenite, very pale orange (lOYR 8/2), well srtd, well rd, comp. Rare 3cm wavy thin lam with heavy mineral concentrations, rare lenses thrt 3cm X .5m of pebbly litharenite. Mud Shale similar to Unit 23, as 10% of unit total in 3cm X 2m lenses. Cgl as 30% of u n it, in lenses av 1.5m X 3m staggered thrt unit and as irreg horizons. Variable clast size in channel-form lenses - LRF sand to sm pbls, subrd, comp to bid in s ilt matrix, matrix support - or small boulder cgl with 20% bldrs, subrd, comp in matrix of inner lenses .3m X .5m with crs sand to med cbls, grain supported in s ilt. Clasts thrt 90% quartzite, 10% other LRF. Calc cement in cgl only.

68.2- ^ Interbedded Litharenite, very pale orange (lOYR 8/2) 78.7 and Mud Shale sim ilar to Unit 23. Litharenite as mod well srtd fine sand, subrd, comp, 15% LRF med sand to sm pbls, subang, comp to bid. Unit 80% sands and 20% Mud Shale as 6cm beds and lenses 3cm X .8m. Also rare lenses of crs sand to sm pbls 5cm X 30cm. Crude thin lam thrt unit, poorly indurated.

65.4- ^ Mud Shale, similar to Unit 23, grading up to Mudstone 68.2 sim ilar to Unit 18. Unit interbedded with 5cm X 30cm lenses to Mud Shale and rare lenses of Litharenite similar to Unit 24.

64.8- ^ Litharenite, yellowish gray (5Y 7/2), poorly sorted fine 65.4 to V crs sand, subang to rd, comp to bid. Abund PD suspended th rt, massive.

60.2- ^ Mud Shale, grayish red (lOR 4/2), variable resistance 64.8 and f is s ilit y , abund PD.

57.2- ^ Interbedded Mud Shale sim ilar to Unit 16 and Litharenite 60.2 sim ilar to Unit 15. Av .4m irreg beds. Base of unit 80% sands grading up to 80% shale.

46.6- ^ Mud Shale, sim ilar to Unit 14. 57.2

46.3- ^ Litharenite, similar to Unit 15. Top 3cm of unit 46.6 orange Fe stained band. 99

U n it/ SECTION 3-B INterval

45.3- 22 Interbedded Mud Shale sim ilar to Unit 16 and Siltstone 46.6 sim ilar to Unit 13; as .2m irreg beds.

42.3- %8 Mudstone, pale red brown (lOR 5/4) grading to pale olive 45.3 (lOY 6/2).To 5% sm LRF pbls, subrd, comp to bid. Massive

41.9- 17 Litharenite, similar to Unit 15. 42.3

41.5- 22 Mud Shale, grayish red (lOR 4/2), abund PD on thin lam, 41.9 variable fissility and resistance.

41.3- 22 Litharenite, very pale orange (IGYR 8/2), mod well srtd 41.5 fine sand, rd, comp. Fine to med LRF grains, subang, comp. Rare PD thrt. Fe stain on joints, silica cement, well indurated. Unit massive.

33.4- 21 Mud Shale, similar to Unit 10. Rare horizons of 41.3 lenticular (4cm X 10cm) limonite and gyp concentrations; some with siltst in centers.

32 7- 33 4 12 Siltstone, grayish orange pink (5YR 7/2), poorly developed irreg thin lam th rt. PD common as impressions along lam. (MP) Plant collecting locality. Irreg Mg stain, gradational contact with bounding units.

26- 22 S ilt Shale, grayish red (lOR 4/2), abund PD. Gyp common 32.7 as jo in t f i l l f ir s t 1.5m, and as 5cm diam Fe stained nodules in top Im. Rounded f la t concretions of massive s ilts t , med dark gray (N4) av 30cm X 20cm, spaced as horizon .5m from base of unit. Concr with rare small LRF pbls and rare PD, coated with 3cm crust of radial gyp .3m X .6m pbly sandstone channel-form lense on concr horizon, sandstone as poorly sorted crs litharenite, subang, comp, with 15% med pbls, LRF, ang, bladed.

25.7- 21 Quartzarenite, very pale orange (lOYR 8/2), well srtd, v 26 fine sand, well rd, comp. 3% LRF crs sand to granules, subang, bid. Rare PD as sand size frags, s ilica cement. Unit very well indurated, massive, gyp common as jo in t f illin g , even bounding surfaces. 100

U n it/ SECTION 3-B Interva l

24.6- TO Mud Shale, sim ilar to Unit 7. Gyp common as irreg 25.7 sheets along bdg laminae.

22.3- _9 Sandy Siltstone, very pale orange (lOYR 8/2), well 24.6 srtd, silt to fine quartzarenite, well rd, comp. 3cm PD stringers along thin lam thrt, occas distorted 5cm lenses with abund PD. Gyp common as jo in t fillin g s and radial laminated concretions to 2cm diam along lam. Rare 1cm X 10cm lenses of crs lith a re n ite , subang, comp. Unit poorly indurated with resistant lenses.

16.5- 8 Quartzarenite, sim ilar to Unit 6, with rare lenses 10cm 22.3 X Im of sandy pbl cgl, 60% fine to crs litharenite matrix, subang, comp/bld, 40% gran to med LRF pbls, subang, bid. Fossil wood th rt. .5m X 1.4m channel-form lense with 10cm diam fossil wood frags. Unit mod well indurated, rare radial gyp along cgl lenses.

14.6- 7_ Mud Shale, moderate red brown (lOR 4/6). Abundant PD, 16.5 rare 10cm X 50cm lenses of v fine sand sim ilar to Unit 6.

10.1- 6^ Quartzarenite, grayish orange (lOYR 7/4), well srtd, 14.6 V fine sand, well rd, comp. Common 3cm thin laminar PD lenses th rt, rare 5cm X 30cm lenses of fine to crs litharenite. Fe stain and crude thin laminae throughout unit.

9.9- ^ Quartzarenite, very lig h t gray (N8), well srtd fine to 10.1 med sand, well rd, comp. Rare PD, planar bounding surfaces Unit mod well indurated, Fe stained, massive.

8.4- ^ Interbedded S ilt Shale and Mud Shale, grayish orange 9.9 (lOYR 7/4). .5m thick fis s ile S ilt Shale with PD common, and .3m beds of Mud Shale with very abundant PD.

7.1- ^ Granule Litharenite, very pale orange (lOYR 8/2), mod 8.4 well srtd, silt to fine sand, subrd, comp. 10% LRF gran, subrd, bid. 3mm PD 1 am and stringers thrt. Crude horizontal lam common with lags of med LRF sand, subrd, comp. Unit poorly indurated. 101

U nit/ SECTION 3-B Interval

5.5- 2 Interbedded Muddy Sublitharenite and Mud Shale, pale 7.1 yellowish brown (lOYR 6/4). 30cm bands of Mud Shale with abund PD in fine muddy sand matrix. Unit app 60% sand, very poorly indurated.

Cover - 4.5m

0- 2 Boulder Conglomerate, lig h t brown (5YR 6/4), 20% LRF 1 (90% quartzite, 10% limestone and other), boulders to 6m, matrix supported, clasts subrd, comp. Matrix of pbl litharenite. Crude wavy stratification thrt with clast size sorting and upward fining. Lenses 10cm X 30cm of crs sand to pbls near top of unit. 102

SECTION 4

%?o \ \ 7 -^5' 60 \ \ \

Vo \ Shale/Sand Faciès s

2 / \ z:^ \ \

\ \ 30 \ \ \ \ H 20 \

f/7 103

SECTION 4

90 'J90

/T

Sand/ Conglomerate Facies

'so

'30

Shale/Sand Facies 104

U n it/ SECTION 4-B Interval

69.6- JJ_ Mudstone, grayish orange (lOYR 7/4), rare PD and LRF 73.1 sand to small pbls. Unit massive.

53.5- JjO Interbedded Mudstone and Sandy Mudstone, very pale 69.6 orange (lOYR 8/2) to moderate yellowish brown (lOYR 5/4). Mudstone massive with trace of crs sand to sm LRF pbls. Sandy Mudstone as .3m beds comprising app 60% of lower 12m of unit and 20% of upper 4m. Clasts app 40% fine qtz sand, subrd, comp, unsorted th rt 60% mud matrix. Unit poorly indurated.

51.8- 2 Sandy Siltstone, grayish orange (lOYR 7/4), sand as 53.3 fine to medium qtz, well rd, comp. Unit massive, poorly indurated.

51.2- S Cobble Conglomerate, lig h t brown (5YR 6/4), 60% matrix 51.8 supported large LRF pbls to cbls, subrd, bid to platey in matrix of poorly srtd, fine to crs litharenite, subrd, bid. 3cm X 10cm lenses thrt of med to crs litharenite. Unit pinches out 10m laterally, very poorly indurated.

41.7- _7 Interbedded Mudstone, yellowish gray (5Y 7/2) and Mud 51.2 Shale, sim ilar to Unit 6. Shale as .3m beds, mudstone as 1.5m beds with common .2m X Im lenses of muddy l i t h ­ arenite, well srtd, med to very crs sand, subrd, comp. Variable induration thrt unit, sand lenses very poorly indurated.

41- §_ Mud Shale, grayish red (lOR 4/2), abund PD along thin 41.7 laminae. Poorly indurated 5cm band at top of unit of s i l t ­ stone with abundant flakes of gypsum.

22.6- 2 Vertebrate bearing Mudstone, pale olive (lOY 6/2), 41 to light brown (5YR 6/4), subtle gradational color (MV) banding av 2m. Rare med sand to sm pbls th rt. Unit weathers in flakes, massive, vertebrate fossils on surface. 105

U n it/ SECTION 4-B Interva l

22.4- ^ Gastropod rich Muddy Limestone, pale yellowish 22.6 brown (lOYR 6/2), 80% pbl size gast shells poorly srtd th rt. Crude wavy thick laminae. Unit lenticular over app 100m, mod well indurated, rare vert fossils.

20.1- 2 Mud Shale, grayish red (5R 4/2), PD very abund along 22.4 thin lam, becomes lig n itic near top of unit. Gyp common along lam at base of unit.

17.1- 2 Sandy Mudstone, very pale orange (lOYR 8/2), other- 20.1 wise sim ilar to Unit 1.

0- 1_ Sandy Mudstone, pale olive (lOY 6/2). To 5% med to 17.7 crs lith a re n ite , subrd, comp, suspended th rt. Subtle color variations in 1.5m bands. Common gyp xtals, rare 3cm diam gyp nodules and gastropods suspended in matrix. Unit poorly indurated, massive. 106

U n it/ SECTION 4-C In te rva l

118.8- J_7 Boulder Conglomerate, lig h t red. Cgl as av 5m X 8m 145.5 channel-form lenses in pbly siltstone. Cgl 50% grain supported cbls and to 3m diam bldrs in s il t matrix. Inner lenses in cgl of poorly srtd sand to pebbly siltstone. Clasts 90% LRF, 10% VRF. Cgl with crude stratification, Fe stain thrt.

90.3- J_6 Mudstone, lig h t brown. Unit massive with 30cm X 118.8 40cm lenses th rt of mod well srtd fine qtz sand to small LRF pbls. Unit coarsens in upper 1.5m and grades into overlying unit.

90- %5 Quartzarenite, white, well srtd fine sand, well rd, 90.3 comp. 3cm X 10cm lenses th rt of lith are nite with heavy metal lag along lense bases. Wavy thin 1 am and indistinct thin x-lam in lenses. Even bdg contacts.

81.7- %4 Siltstone, light gray, massive with concr similar to 90 Unit 3. Lenses 10cm X 50cm of pbl mudstone, 30% crs sand to sm LRF pbls, subrd, compact.

78.7- 1_3 Cobble Conglomerate, medium gray. Composite channel- 81.7 form lenses with inner lenses, in matrix of siltstone. Cgl clasts 70% LRF, 30% VRF sm pbls to large cobbles, subrd, comp. S tra tific a tio n , inner lenses and trough x-lam sort clasts from pbl s ilts t to grain supported cbls, to matrix supported pbls. Pebbles well imbricated in places.

75.4- 12 Interbedded Mudstone and Mud Shale, lig h t red. Mudstone 78.7 massive with to 5% med sand to sm LRF pbls. Mud Shale as .5m irreg beds with abund PD and 5cm lig n itic stringers

72.2- j_l_ Pebbly Mudstone, lig h t tan, poorly srtd 20% med sand 75.4 to sm pbls, LRF, subrd, comp. 20cm X 60cm stringers of fine sand common, rare PD suspended th rt unit.

71.1- Mud Shale, red brown, abundant PD. 72.2 70.8- ^ Litharenite, medium gray. Poorly srtd, fine to crs 71.1 sand, subang, comp/bld. Unit massive, even bdg contacts, well indurated, Fe stained weathering. 107

U n it/ SECTION 4-C In te rva l

67.2- 8 Pebbly Siltstone, light gray. 15% crs sand to sm pbls, 70.8 LRF and qtz, subrd, comp. 5cm X 30cm lenses of s ilty crs sand to large pbls, subang, bladed. Unit massive with 10% lenses, mod well indurated.

56.7- 1_ Siltstone and Cobble Conglomerate, tan. 20% massive 67.2 s i l t , 80% cgl as channel-form lenses with inner lenses and x-beds sorting clasts from pbl mudstone to boulders. Cgl clasts 80% quartzite, 10% limestone, 10% VRF in litharenite matrix. Stratification with crude fining upward. Also, isolated 3cm X 10cm lenses of med to crs LRF sand thrt unit. Unit pinches out 200m laterally.

19.5- 6^ Interbedded Siltstone and Pebbly Mudstone. Siltstone 56.7 massive with irreg 1.5m beds of Pebbly Mudstone with 15% crs LRF sand to sm pbls, subrd, comp. Poor exposure.

15- ^ Siltstone, similar to Unit 3. 19.5

12.9- 4 Siltstone, lig h t red, massive. Rare lenses and pockets 15 av 10cm X 40cm of Sandy Mudstone, with 20% crs sand to 1 g pbls, LRF, subrd, comp. Also rare ash fille d lenses. Unit mod well indurated.

9.2- _3 Siltstone, lig h t tan, massive. 5cm concr horizons near 12.9 base and top of unit. Concretions and nodules of mud pbl s ilt s t with x ta l- fille d vugs app 2cm diam.

7- ^ Sandy Mudstone, red orange. 5% fine to med LRF sand, 9.2 subrd, comp. Unit massive.

0- 1_ Siltstone, tan, and Cobble Conglomerate. S ilt mod well 7 srtd, 10% sm LRF pbls th rt, massive. Cgl as channel- form lenses av .4m X Im with smaller lenses, trough x-beds, and crude s tra tific a tio n . Cgl both clast and matrix supported, unsorted LRF sm pbl to cbls (80%), subrd, comp. Mud to crs sand matrix. Unit poorly indurated. 108

SECTION 5

/r

/3

Coarse Tuffaceous Facies /

Fine Tuffaceous Facies

Fine Tuffaceous Facies m m 109

SECTION 5

94

\ ¥3 Shale/Sand Facies w

3 o Fine Tuffaceous Facies

IT

Fi ne Tuffaceous Facies / &

2.1 no SECTION 5

73

7z \

# Shale/Sand Faciès

c

Si-

7o

S9

64,

'S Z < i h 42

Si 67 P

:1 2 2

4..

3T_ —

44 60, # i n

U n it/ SECTION 5 Inte rva l

684.9- _7§. Ashy Mud Shale, very pale orange, rare PD becoming 713 locally abundant. Plant collecting locality, with (MP) well preserved impressions along laminae.

665- 21 Ashy Siltstone, bluish white, thick lam thrt with PD 684.9 rare along partings. Unit weathers as chips, moderately resistant, resistant ledges form where unit becomes less fis s ile .

Cover - 11m

648- 73 Interbedded Mud Shale, sim ilar to Unit 62 and Mudstone, 654 similar to Unit 61.

641.4- 22. Siltstone, light olive, with mudstone and mud shale. 648 Unit 80% massive siltstone^5% PD, 10% mudstone as 5cm X 30cm stringers th rt, 10% mud shale with abund PH' as stringers and wavy lenticular beds 3 to 10cm X .2 to .5m. Abund mud shale at base of unit. Rare Fe stained 5cm diam nodules of mudstone or fine sandstone. 3cm cap on unit of poorly srtd med to crs muddy litharenite, subang, comp.

639.9- 2 1 Mud Shale, sim ilar to Unit 62. Poor exposure. 641.4 Cover - 16.5m

617.9- 21 Mudstone, sim ilar to Unit 61. 623.4

616.6- ^ Mud Shale, sim ilar to Unit 62. 617.9

616.2- 6 S Quartzarenite, similar to Unit 63. 616.6

614.8- 67^ Siltstone, lig h t olive, massive, Fe stained joints th rt, 616.2 weathers as dust.

613.1- §6^ Mud Shale, sim ilar to Unit 62. 614.8

612.5- ^ Quartzarenite, similar to Unit 63. 613.1 112

U n it/ SECTION 5 Interva l

610.8- 64 Mud Shale, sim ilar to Unit 62. 612.5 “ ■

609.6- 6 ^ Quartzarenite, pale orange, well sorted, fine sand, 610.8 subrd, comp. 2cm X 10cm lenses of crs lith a re n ite , subang, comp. Crude fine x-lam th rt unit. Unit very poorly indurated.

607.8- 62 Mud Shale, grayish orange, abund PD, gyp xtals common 609.6 and 1cm irreg lam of radial gyp at top of unit.

603.8- ^ Mudstone, olive yellow, massive, yellow Fe stain stringers 607.8 th rt, very bentonitic weathering.

580.8“ 582.3 6 ^ Mudstone, lig h t olive, massive, rare vert bone scrap th rt.

579.3- Pebbly Arkose, pale orange, grades upwards from sm pbls 580.8 to med sand, subrd, comp. Mud matrix, poorly indurated, poor exposure.

Cover - 24m

555- 5 8 Subarkose, very pale orange (lOYR 8/2), mod well srtd, 555.3 med sand, subrd, comp. Silica cement, very well indurated, massive, s lig h tly wavy bedding surfaces.

552.4- ^ Muddy Pebble Conglomerate, pale yellowish orange 555 {lOYR 8/6), unsorted med sand to med pbls in mud matrix. Clasts 80% LRF, 20% VRF, subang to rd, comp to bid. Both grain and matrix support local. Unit poorly indurated, mod poor exposure.

548.4- ^ Cobble Conglomerate, dark yellowish orange (lOYR 6/6), 552.4 grain supported, unsorted crs sand to large cbls, 30% pbls, 40% sand. Clasts 10% quartzite, 50% VRF, 40% other LRF, mod well rd, bid to comp. Mud cement, poorly indurated. Lenses 1.5m X 2m, more resistant, with med pbls and cbls. Wavy lenses 10cm X 30cm of crs pbl sandstone. Fe stain weathering.

544.3- ^ Mud Shale, sim ilar to Unit 51, poor exposure. 548.4 Cover - 9m 113

U n it/ SECTION 5 In te rva l

533.8- ^ Lithic Subarkose, grayish yellow (5Y 8/4), poorly 535.3 srtd med sand to granules, subang to subrd, comp. Mud cement, 10% pumice granules th rt. Unit poorly indurated, massive, irregular bdg contacts.

519.1- ^ Mud Shale, sim ilar to Unit 51. Grades to Ashy Mudstone 533.8 in top 2m of unit.

518-6- ^ Arkose, grayish orange (lOYR 7/4), mod well srtd crs 519.1 sand, subang, comp, 10% mud shale chips to 1 cm X 5cm th rt. Base of unit wavy and irreg by .2m, scours into underlying unit .5m X 6m in places.

513.3- ^ Mud Shale, grayish orange (lOYR 7/4) to nearly black, 518.6 variable PD from rare to lig n itic . Unit weathers as paper shale. Rare .2m white ash mudstone beds th rt.

513- ^ Lith ic Arkose, very pale orange (lOYR 8/2), grades 513.3 evenly upward from crs to fine grained sand, well rd, comp. Wavy bedding contacts, s ilic a cement, very well indurated, massive.

Cover - 12.2m - local ashstone with chert nodules.

478.3- 4^ Ashy Siltstone, very pale orange (lOYR 8/2), crude 500.8 3m beds, lenses th rt av .2m X 5m fille d with massive, gast brng calc mudstone or; massive, v fine grained lith a re n ite , well srtd, subrd, comp, or; massive crs lith ic arkose sim ilar to Unit 27 or; fis s ile gast brng marl.

478- ^ Ash Mudstone, bluish white (5B 9/1). Dark brown PD 478.3 common along 3cm thick lam. Rare crs sand to Ig pbl size chert nodules throughout unit.

476.6- 478 ^ T u ffite S ilt Shale, sim ilar to Unit 45.

475.9- ^ L ith ic Arkose, lig h t gray (N7), well srtd, crs sand, 476.6 subang to subrd, comp. Ash matrix with pumice grains th rt. Crude lenses av 10cm X 40cm fille d with thin x-lam that concentrate LRF's and pumice along lam. Bdg contact irreg, thins laterally as much as .5m, mod well indurated. 114

U n it/ SECTION 5 Interva l

472.7“ ^ Tuffaceous S ilt Shale, lig h t brown (5YR 6/4), variable 475.9 fissility, PD in .5m horizons, gradations from common PD to lig n itic . S ilt shows mica flakes and ash th rt.

472.3- ^ Silicious Limestone, yellowish gray (5Y 7/2), 50% 1mm X 472.7 5mm stringers of s ilic a th rt. Unit massive, irregular lenticular horizon.

460.7“ ^ Mud Shale, grayish red (lOR 4/2), abund PD, 5% gastropods, 472.3 rare 5cm beds of ash s il t shale. Unit grades upward to Ashy Siltstone in top Im, pale yellowish brown (lOYR 6/2) with common PD, rare gast, blocky weathering.

Cover - 19.5m

440.5- ^ Silicious Ash Marl, similar to Unit 40. 441.2

427“ ^ Ashy Mudstone and Marl, sim ilar to Unit 39. 440.5

425.4- ^ Silicious Ash Marl, light gray, large pbl size chert 427 nodules common th rt. Unit weathers in blocks, massive.

404.2- ^ Interbedded Ashy Mudstone and Ashy Marl, sim ilar to 425.4 Unit 36. Marl as 10cm beds app every 1.5m with thin inner lam. 20% gast frags in Marl. Poor exposure.

402.7- 38 Pumice Litharenite, light gray, and Pumice Siltstone, 404.2 dark brown. Sandstone as well srtd, crs sand, subrd, comp, in 20cm diam concretions and as .2m X 1.5m irreg lenses. 30% pumice grains thrt. Siltstone with 20% crs sand size pumice and crude 5cm 1 am with abund PD. Unit mod well indurated, mud cement.

Cover 3m

399.2- 37 Ostracod bearing Ashy Marl, sim ilar to Unit 26. Rare 399.7 chert stringers av 5mm X 3cm near base.

377.7- ^ Interbedded Ashy Mudstone, sim ilar to Unit 21 with 399.2 .5m X 3m le nticu la r Ashy Marl bands, very poor exposure. 115

U n it/ SECTION 5 In te rva l

365.2- ^ Interbedded Ashy Mud Shale and Ashy Marl sim ilar to 377.7 Unit 27.

364.8- ^ Silicious Limestone, sim ilar to Unit 32. 365.2

361.2- 21 Interbedded Ashy Mud Shale and Ashy Marl, sim ilar 364.8 to Unit 27.

360.8- 21 S ilicious Limestone, gray. Massive, cherty 5cm 361.2 stringers thrt, smooth bdg surfaces.

353.5- 21 Interbedded Ashy Mud Shale and Ashy Marl, sim ilar 360.8 to Unit 27.

352.3- 21 Ashy Marl, grayish orange (lOYR 7/4). Unit massive 353.5 with 3mm X 5cm tubules common along base. Top .2m as 70% angular crs sand to sm pbl and silicious mud chips. Blocky weathering. Unit forms resistant ledge.

349.5- 21 Ashy Mud Shale, sim ilar to Unit 15, poor exposure. 352.3

347- 2 1 Ash Mudstone, bluish white (58 9/1), massive, weathers 349.5 as 3cm flags. Unit capped by 10cm ostracod/gast mudstone - 90% ostracods, 10% gast. Unit silicified thrt, very well indurated.

322.9- 2 Z Interbedded Mud Shale and Ashy Marl sim ilar to Unit 19. 347 Marl as resistant .5m beds app every 1.5m. Shale recessive, occasional thin lam of ostracod brng Marl similar to Unit 22.

322.4- 21 Ostracod bearing Ashy Marl, sim ilar to Unit 22, shell 322.9 concentration increases towards top of unit.

319.4- 21 Ashy Mudstone, sim ilar to Unit 21. Poor exposure. 322.4

319- 2 1 Tuffaceous Calcareous Siltstone, sim ilar to Unit 20. 319.4

315.4- 21 Ashy Mudstone, sim ilar to Unit 21. 319 116

U n it/ SECTION 5 In te rva l

314.9- ^ Ostracod bearing Ashy Marl, very pale orange 3115.4 (lOYR 8/2), massive, 80% ostracod shells.

308.9- ^ Ashy Mudstone, dark yellowish orange (lOYR 6/6), 314.9 massive, blocky weathering, to 5% PD and rare gast shells thrt. Unit Fe stained, silica cement, well indurated.

308.1- ^ Tuffaceous Calcareous Siltstone, grayish orange 308.9 (lOYR 7/4), crude irreg 10cm beds with rare 5mm lam. To 3% LRF crs sand, well rd, comp. Unit with calc cement, well indurated.

300.7- J_9 Interbedded Mud Shale, sim ilar to Unit 15, and Marl, 308.1 sim ilar to Unit 16. Marl as .3m beds app every 1.5m th rt unit.

300.1- J8 Ashy Marl, sim ilar to Unit 16. 300.7

297.9- V7 Ashy Mud Shale, sim ilar to Unit 15. 300.1

297- J6^ Ashy Marl, very pale orange (lOYR 8/2), in d istin ct v 297.9 thin lam in 3cm bed sets. 20% gast shells concentrated along beds Carbonized PD common along beds. Unit with even, smooth bedding surfaces, well indurated.

288.5- T5 Ashy Mud Shale, grayish orange (lOYR 7/4), thin lam 297 th rt with 3% PD as impressions along lam, 5% gast along lam. Central 2m of unit massive, unit s lig h tly calcareous

287.9- 24 Gastropod bearing Silicious Marl, pale olive (lOYR 6/2) 288.5 to very pale orange (lOYR 8/2). Lower .4m massive, 20% mollusk shells. Chert stringers common near base of unit. Upper .2m 80% gast shells. Irreg wavy thin lam thrt unit, smooth bedding surfaces, very resistant.

283.7- 1_3 Silicious Mudstone, pale yellowish brown (lOYR 6/2), 287.9 crude irreg 3cm lam th rt, with concentration every 10cm of mollusk shells. Fe stained thin 1 am thrt. Top .2m of unit grades to Tuffaceous S ilts t. Unit resistant as chips, becomes slightly calc in top Im. 117

U n it/ SECTION 5 Interva l

283.5- 1_2 Gastropod bearing Tuffaceous Marl, very pale orange 283.7 (lOYR 8/2), massive, to 60% gast in upper .2m of unit, app 20% gast below. S lightly irreg, wavy bedding surfaces.

280.5- 21 Tuffaceous Siltstone, sim ilar to Unit 9. Poor 283.2 exposure.

279.9- 21 Gastropod bearing S ilty Limestone, pale yellowish 280.5 brown (lOYR 6/2). Large pbl size patches th rt of altered Tuffaceous S ilts t, otherwise dense and massive with s il t grains 10% suspended th rt. Bottom .4m of unit with common 2mm X 10cm tubules. Upper .2m of unit 60% gast and common .Im X .3m lenses with 80% subrd pbl size pumice, and 5% gast. Unit with irreg bedding surfaces.

274.4- £ Tuffaceous Siltstone, yellowish gray (5Y 7/2), 5% subrd 279.9 qtz and LRF crs sand, 30% sand size well rd pumice. Unit massive, poorly indurated, mod poor exposure.

257.9- £ Tuffaceous Siltstone, sim ilar to Unit 6, and rare .2m 274.4 thick stringers of Porcellanite similar to Unit 7.

257.2- 2 Tuffaceous Porcellanite, pale yellowish green (lOGY 7/2), 257.9 10% med sand size qtz and mica xtals in fine groundmass. Unit massive, highly resistant, conchoidal fracture.

229.9- £ Tuffaceous Siltstone, grayish yellow (5Y 8/4). To 10% 257.2 silt to fine sand size qtz, felds, and mica xtals thrt. To 20% olive, med sand to sm pbl size, rd pumice. Unit massive, weathers as chips or bladed blocks.

219.9- £ Interbedded Tuffaceous Mudstone and Sandstone sim ilar 229.9 to Unit 3.

219- 2 Tuffaceous Silicious Limestone, grayish orange pink 219.9 (5YR 7/2). Pbl size patches and 2cm X 5cm lenses th rt of highly altered Tuffaceous Sandstone. 3mm stringers and Ig pbl size silicified/cherty patches. Unit with irreg thick lam, wavy bdg surfaces, very well indurated. 118

U n it/ SECTION 5 Interva l

210.5- 3^ Interbedded Tuffaceous Mudstone, very pale orange 219 (lOYR 8/2) and Tuffaceous Sandstone, yellowish gray (5Y 7/2). Mudstone as massive bdg, very well indurated, with mollusks common. Sandstone as 80% fine to med, subrd, to subang, qtz, felds and biotite xtals in ash. Rare gastropods, bdg irreg .2m to .4m. Mod poor exposure.

141- ^ Crystal Tuff, white (N9). 20% crs sand size qtz xtals 210.5 th rt. Unit massive, with crude partings and weathers as blocks or .2m thick flags. Fe stain bands on weathered surfaces.

0- J_ Undifferentiated volcanogenic debris, fine grained 144 tuffaceous siltstones, massive cliff-forming rhyolite tuff. Localized thin bedded tuffaceous siltstone with abund gast, resistant beds to .5m thick of calc s ilt­ stones. Generally poor exposures. y 6 119 - i — i , _ Ü . S' a y —*— d SECTION 6

'ts

££.

\ Fi ne Tuffaceous Facies

30 120 T 7 ^ SECTION 7

f

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Coarse Tuffaceous Facies /

7f? 121 SECTION 7

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70 \ Fine Tuffaceous Facies /

'So

"VO \ Fi ne Tuffaceous Facies io

\

Coarse 1>0 Tuffaceous Facies

/

-,

■90 73 122

SECTION 7

\ M / 15 Shale/Sand :a@g < Z Z 5 «S» if Facies \ /

It

Fine Tuffaceous Facies / 123 SECTION 8

Coarse Tuffaceous Faciès

3 .0 124

U n it/ SECTION 8 Interva l

61- 12 Vi trie Tuff, similar to Unit 10. 65 ■“

60.4- J2 Tuffaceous Sandy Siltstone, sim ilar to Unit 2. 61 Slightly irreg but distinct bdg contacts.

51.4- TO Vitric Tuff, similar to Unit 6, crude 1.5m beds with 60.4 less resistant ,5m recessive beds sim ilar to Unit 8. Occasional pale green, 20cm diam, patches and stringers of Tuffaceous Siltstone sim ilar to Unit 9.

50.6- ^ Tuffaceous Pebbly Sandstone, pale greenish yellow 51.4 (lOY 8/2), unsorted, 30% matrix supported med VRF pbls, subrd and as lenses av 15cm X 40cm wide, with poorly defined low angle x-lam.

43.6- 8 Vitric Tuff, similar to Unit 6, with .3m diam patches 50.6 and thin laminated stringers of Tuffaceous Siltstone, similar to Unit 2.

41.8- 2 Tuffaceous Siltstone, sim ilar to Unit 3, but recessive, 43.6 weathers as small pebbles.

38.2- 6^ Vitric Tuff, very pale orange (lOYR 8/2), 70% fine sand 41.8 size xtals thrt - 90% qtz, 10% mafics. Unit very well indurated, massive, conchoidal weathering.

31.2- 2 Tuffaceous Siltstone, sim ilar to Unit 3. 38.2

28.2- 2 Tuffaceous Sandy Siltstone, sim ilar to Unit 2. 31.2

22.7- 2 Tuffaceous Siltstone, pale greenish yellow (lOY 8/2), 28.2 massive, fine mafic flakes th rt, poor exposure.

17.2- 2 Tuffaceous Sandy Siltstone, pale green (5G 7/2), unsorted, 22.7 10% fine to med sand as biotite and mafic minerals, silt as ash and pumice. Variable resistance th rt as .6m to 1.5m crude bdg, also rounded more resistant patches .2m X .6m. 125

U n it/ SECTION 8 Interval

0- J_ Tuffaceous Pebble Conglomerate, very lig h t gray (N8) 17.2 to pale olive (lOY 6/2). Crudely bedded interlayering of xtal tuff, tuffaceous pbl cgl, and tuffaceous cbl cgl. Vitric tuff rhyolitic, 40% ash, 30% qtz xtals, 20% pbl size pumice, 10% mafics and rare LRF's. Pbl and cbl cgl with 30% VRF, 5% LRF, subrd to angular in tuffaceous sandstone matrix. Small lenses av. .2m X ,7m with med pbls, 80% VRF th rt. Rare channel-form lenses av .6m X 5m with interlayered smaller lenses of sm pbl to cbls, and 10cm thick stringers of tuffaceous siltstone. Unit with common intraformational clasts .2m av diam suspended in matrix - clasts rounded, pale green tuffaceous s ilt­ stone similar to overlying unit, and with 5% med pbl size vesicular, basalt. Unit mod well indurated. 126 SECTION 9

Shale/Sand Facies

tz.

?

as.

i6

17

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tsr

/Y % _ A T :

90 / 3 127

U n it/ SECTION 9 Inte rva l

211- 19 Mudstone, lig h t brown, massive, weathers as flakes. 219 —

204.8- 28 Interbedded Ashy Sandy Siltstone and Pebbly Mudstone, 211 color banded light olive to light brown. Siltstone with 40% med to fine sand size pumice. Mudstone with 20% fine sand to sm pbls, LRF, subang, comp. Unit massive within crude beds.

201.4- y j_ Ashy Siltstone and Cobble Conglomerate, lig h t brown. 204.8 Siltstone with 40% fine sand size pumice and mica, 3cm X 10cm lenses th rt of pebbly litharenite. Irreg lenses 1.5m X 3m of poorly indurated cgl. Cgl clasts 80% LRF, 20% VRF, pbl to Ig cbls, poorly sorted, subrd, bid to comp, suspended in s i l t matrix. 10cm X 30cm lenses in the cgl of clast supported crs sand to large pebbles.

198.4- J_6 Mudstone, lig h t olive, 5cm pockets common th rt of 201.4 fine qtz sand, well rd, comp, unit otherwise massive.

184.9- 22 Siltstone, light gray. 5% crs sand to pbls, LRF, subrd, 198.4 suspended in s i l t matrix. Unit coarsens upwards. Rare 20cm X Im lenses of pebbly sublitharenite, subrd, comp. Unit poorly indurated.

183.4- 21 Mudstone, similar to Unit 3. 184.9

158.2- 21 Interbedded Mudstone, sim ilar to Unit 3 and Ashy Mud 183.4 Shale, white, with abund PD in .6m thick beds.

141.7- 21 Ashy Mudstone, lig h t gray. Thin lam th rt in Im beds. 158.2 PD variable to abundant. Resistant, massive bands throughout.

135.7- 21 Interbedded Mudstone and Mud Shale, lig h t red. Mudstone 141.7 massive. Shale with PD common. Poor exposure.

135.4- 21 Mudstone, lig h t gray, thick lam th rt, abundant fish 135.7 scales and rare PD along laminae.

133.9- 2 Mudstone, lig h t gray. Very thin horizontal laminae, 135.4 rare PD. Unit weathers as fine flakes. 128

U n it/ SECTION 9 Interva l

133.2- 8 Boulder Mudstone, tan. Poorly sorted 30% LRF crs sand 133.9 to small boulders, matrix supported, fining upward, 20% crs sand size pumice in muds. Rare PD suspended in muds

131.9- 1_ Silty Subl i thareni te, light gray. Poorly sorted fine to 133.2 crs sand, subang, bid. 30% pumice frags. Unit massive, poorly indurated.

131.8- Pebbly Litharenite, med gray. 20% sm pbls to cbls in 131.9 poorly srtd fine to crs sand, subang, bid. Mud matrix, Fe stained cement.

131.3- _5 Siltstone, similar to Unit 2. 131.8

130.8- ^ Siltstone, light gray. Thickhorizontal lam thrt, PD 131.3 common along laminae, rare 15cm diam nodules of pbl mudstone.

126.5- 3 Mudstone, lig h t olive, massive. 130.8 Cover - 95m

25.5- _2 Siltstone, lig h t brown. Common 10cm X 12cm lenses 31.5 fille d with pebbly coarse lith a re n ite , subang, comp.

0- J_ Interbedded Mudstone and Mud Shale, lig h t olive to lig h t 25.5 red. Shale with abund PD in .8m beds with 5cm lig n itic bands. Mudstone with irreg thick laminations. 129 SECTION 10

10 I

\

Coarse Tuffaceous Facies

10 130

U n it/ SECTION 10 Interva l

41.6- J_5 V itric Tuff, medium lig h t gray (N6), unsorted, 60% 55.1 ash, 40% fresh crs sand size xtals of qtz and felds, V fine sand size mafics th rt. Small pbl size rounded pumice. Rare med pbl size pumice fragments. Unit very resistant, massive.

35.9- J4 Tuffaceous Siltstone in thin beds sim ilar in color to 41.6 Units 1 and 2.

35- T3 Interbedded Tuffaceous Siltstone, medium lig h t gray 35.9 (N6) and vitric Tuff similar to Unit 4. Vitric Tuff as 5cm thick irreg beds. Minorjo in t offset on beds th rt. Sharp top contact.

32.7- 2^ Tuffaceous Siltstone, sim ilar to Unit 1, grades into 35 overlying unit.

32.2- 21 Tuffaceous Siltstone, grayish yellow (5Y 8/4), unsorted, 32.7 80% ash, 20% v fine to fine sand size qtz, felds, biotite and mafics. Unit highly resistant, massive.

31.2- 20. Tuffaceous Sandstone, yellowish gray (5Y 7/2), poorly 32.2 srtd, 30% ash, 70% med to crs sand size xtals, angular to subrd. Xtals 60% qtz, 30% felds, 10% b io tite flakes plus trace of mafics, LRF's. VRF and LRF common in 10cm X Im rounded lenses of taffaceous s il t sim ilar to Unit 1, in broken horizons. Unit otherwise massive, mod well indurated.

28.2- 9^ Tuffaceous Siltstone, lig h t gray (N8) grading to pale 31.2 olive (lOY 6/2). 10% fine sand size xtals of qtz, felds, biotite, subang. Unit with very thin lam in 3cm beds, resistant.

28- S V itric Tuff, pale reddish brown (lOR 5/4), unsorted 60% 28.2 ash and pumice, 40% crs sand size xtals of qtz, felds, and biotite. Unit highly resistant.

24.7- 7 Tuffaceous Siltstone, sim ilar to Unit 1. 28

24.3- 6 Tuffaceous Siltstone, sim ilar to Unit 3. 24.7

21.6- _5 Tuffaceous Siltstone, sim ilar to Unit 1. 24.3 131

U n it/ SECTION 10 Inte rva l

21.3- 4 Interbedded Tuffaceous Siltstone and V itric Tuff, very 21.6 pale orange (lOYR 8/2). Siltstone as 6cm bands sim ilar to Unit 2. V itric Tuff as massive, unsorted, 60% ash and pumice, 40% crs sand size xtals of qtz, felds, and biotite. Unit Fe stained thrt, calc cement, very well i ndurated.

18.1- Tuffaceous Siltstone, pale olive (lOYR 6/2), similar to 21.3 Unit 2 but less resistant.

17.3- Tuffaceous Siltstone, very pale orange (lOYR 8/2). 18.1 10% fine sand size xtals of qtz, felds, biotote in ashy matrix. Unit highly resistant, silica cement, massive.

0 - Tuffaceous Siltstone, very lig h t gray (N8), unsorted, 17.3 80% ash, 20% v fine sand size xtals of qtz (60%), felds (20%), b io tite (20%) and trace of mafics and LRF's. Concretions common of sim ilar composition as rounded lenses .2m X Im. Joints in concr filled with calcite. Unit mod resistant, calc cement, weathers as bentonitic slope at base, crudely bedded, av Im sligh t color variations. 132 SECTION 11

Sand/ Conglomerate Faciès -TV

30

7o Shale/Sand Faciès 133 SECTION 12

73

\ Sand/ Conglomerate Faciès

/

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