Paleoecological and Floristic Heterogeneity in the 

Plant-Fossil Record An Analysis Based on the 

Eocene of Washington

OGY LIB'n&v

U.S. GEOLOGICAL SURVEY BULLETIN 2085-B

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Cover. Steeply dipping beds (fluvial channel deposits) of the Eocene Puget Group in the 

upper part of the Green River Gorge near Kanaskat, southeastern King County, Washington. Photograph by Samuel Y. Johnson, July 1992.
Paleoecological and Floristic Heterogeneity in the 

Plant-Fossil Record An Analysis Based on the 

Eocene of Washington

By Robyn J. Burnham

EVOLUTION OF SEDIMENTARY BASINS CENOZOIC SEDIMENTARY BASINS 

IN SOUTHWEST WASHINGTON AND NORTHWEST OREGON

Samuel Y. Johnson, Project Coordinator

U.S. GEOLOGICAL SURVEY BULLETIN 2085-B

A multidiscipUnary approach to research studies of 

sedimentary rocks and their constituents and the 

evolution of sedimentary basins, both ancient and modern

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1994
U.S. DEPARTMENT OF THE INTERIOR 

BRUCE BABBITT, Secretary

U.S. GEOLOGICAL SURVEY «'

Gordon P. Eaton, Director

For sale by U.S. Geological Survey, Map Distribution

Box 25286, MS 306, Federal Center

Denver, CO 80225

Any use of trade, product, or firm names in this publication is for descriptive purposes only and 

does not imply endorsement by the U.S. Government

Library of Congress Cataloging-in-Publication Data

Burnham, Robyn J.

Paleoecological and floristic heterogeneity in the plant-fossil record : an analysis based 

on the Eocene of Washington / by Robyn J. Burnham.

p. cm. (U.S. Geological Survey bulletin ; 2085)

Evolution of sedimentary basins Cenozoic sedimentary basins in southwest 

Washington and northwest Oregon ; B)

Includes bibliographical references.

Supt.ofDocs.no.: I 19.3:2085-8

1. Paleobotany Eocene. 2. Plants, Fossil Washington (State)-King 

County. 3. Paleoecology Washington (State) King

County. I. Title. II. Series. III. Series: Evolution of sedimentary basins 

Cenozoic sedimentary basins in southwest Washington and northwest Oregon : B. 

QE75.B9 no. 2085-B 

[QE927.2]

557.3 s dc20 94-1627 

[560.178] CIP
CONTENTS

Abstract.......................................................................................................................... Bl

Introduction.................................................................................................................... 1

Stratigraphy of the Puget Group..................................................................................... 2

Description of the Field Area......................................................................................... 4

Data Collection............................................................................................................... 5

Stratigraphic Sections........................................................................................... 5

Plant-Fossil Collections........................................................................................ 6

Adjustments to the Data Set................................................................................. 6

General Characteristicsof the Upper Ravenian Flora..................................................... 8

Analysis of Plant Distribution Presence-Absence Data.............................................. 9

Species Richness.................................................................................................. 10

Species Diversity.................................................................................................. 10

Leaf Margins of AngiospermTaxa...................................................................... 10

Leaf Size of AngiospermTaxa............................................................................. 12

Conifers, Pteridophytes, and Sphenopsids........................................................... 12

Comparison of Floristic Assemblages.................................................................. 13

Summary of Data on Presence-Absence of Species............................................. 13

Analysis of Plant Data Taxon Abundance .................................................................. 15

Ordination of Localities ....................................................................................... 15

Methods.......................................................................................................... 15

Results and Discussion................................................................................... 15

Cluster Analysis................................................................................................... 16

Methods.......................................................................................................... 16

Results and Discussion................................................................................... 16

Environmental Heterogeneity in the Puget Group......................................................... 17

Discussion...................................................................................................................... 17

Species Distribution in the Upper Ravenian Puget Group................................... 17

Anomalous Localities and their Use in Interpreting Paleoecology...................... 20

Conclusions.................................................................................................................... 20

Depositional Environments Implications for their Use in Paleobotany...................... 21

Biostratigraphy..................................................................................................... 21

Paleoclimatology.................................................................................................. 21

Paleoecology........................................................................................................ 21

Recommendations for Cenozoic Paleobotanical Investigations ...........................:........ 22

References Cited............................................................................................................ 22

Appendix 1. Matrix of Abundance Data for 20 Plant-Fossil Localities from the

Puget Group................................................................................................................ 28

Appendix 2. Matrix of Sorenson's Index of Similarity for Comparisons Between 20

Plant-Fossil Localities from the Puget Group............................................................ 30

Appendix 3. Matrix of Spearman's Rank-Order Correlation Coefficients for 20

Plant-Fossil Localities from the Puget Group............................................................ 30

Appendix 4. Abbreviations and Taxonomic Citations for Plant-Fossil Taxa from

the 20 Localities Examined in the Puget Group......................................................... 31

III
IV CONTENTS

FIGURES

1. Map showing outcrop area of the Eocene Puget Group, Washington...................................................................... B2

2. Stratigraphic type section of the Eocene Puget Group............................................................................................. 3

3. Diagram showing discrepancies between radiometric and paleobotanical ages of rock units from the

Eocene Puget Group ................................................................................................................................................. 4

4. Map showing location of study area and plant localities.......................................................................................... 5

5. Stratigraphic sections of the Eocene Puget Group, L-Bar silica quarry................................................................... 7

6. Diagram showing relationships of depositional environments of the Eocene Puget Group..................................... 8

7-15. Graphs showing:

7. Numbers of specimens and taxa by locality..................................................................................................... 8

8. Species richness by locality ............................................................................................................................. 10

9. Shannon-Weiner diversity index by locality.................................................................................................... 11

10. Percentage of species having entire-margined leaves by locality.................................................................... 11

11. Leaf-size index by locality............................................................................................................................... 12

12. Species richness of selected plant groups by locality...................................................................................... 13

13. Sorenson's Index of Similarity of localities..................................................................................................... 14

14. Detrended Correspondence Analysis of localities........................................................................................... 15

15. Cluster Analysis of localities ........................................................................................................................... 16

16. Drawing showing plan view of hypothetical landscape heterogeneity..................................................................... 19

TABLES

1. Depositional environment, species richness, and height above base of section for plant-fossil localities used in

paleoecological analysis, Eocene Puget Group, Washington................................................................................... B6

2. Comparison of flora of the Ravenian Puget Group with other Oligocene and Eocene floras from the Pacific

Northwest and Alaska............................................................................................................................................... 9

3. Leaf-size classes........................................................................................................................................................ 12

4. Dominant taxa (5 percent or greater relative abundance) at 20 plant-fossil localities from the Eocene

Puget Group...........................................................................^ 18
Paleoecological and Floristic Heterogeneity in the

Plant-Fossil Record An Analysis Based on the

Eocene of Washington

By Robyn J. Burnham1

ABSTRACT

The late Ravenian (Eocene) flora from the Puget Group 

of Washington State is characterized by a wide variety of 

deltaic depositional environments. The flora is strongly controlled by the facies in which the plants are preserved. Lacustrine-fill assemblages are extremely variable from site to site 

and can only be used as a group to reconstruct paleoclimate 

and floristics. Channel-margin assemblages are depauperate 

relative to the regional flora and consistently underestimate 

paleotemperature. Floodbasin assemblages tend to contain a 

larger proportion of the whole flora and give a much more 

consistent estimate of the paleotemperature. Combining 

these floras from distinct depositional environments allows 

reconstruction of heterogeneity on the floodplain. Floras 

contributing to channel margins are similar because of the 

conduit nature of the channel itself. Lacustrine-fill assemblages are derived from lakeside floras, which vary from site 

to site because of the random colonization of lake margins 

from the surrounding floodplain habitats. Floodbasin floras 

are species rich and are composed of a greater cross section 

of the floodplain plant dominants than any of the other floristic assemblages. When used to reconstruct the floodplain 

landscape, floras distinguished by depositional environments become a powerful tool in paleoecology.

INTRODUCTION

The plant species composition at any particular site on 

a floodplain is dependent on the topography, substrate, and 

frequency and depth of flooding (Shelford, 1954; Bedinger, 

1971; Bell and del Moral, 1977; Nixon and others, 1977;

'Museum of Paleontology, University of Michigan, Ann Arbor, Michigan 48109-1079

Frye and Quinn, 1979; Hupp, 1982, 1983; Yanosky, 1982; 

Hupp and Osterkamp, 1985; Johnson and others 1985). The 

differential response of species to physical heterogeneity 

creates a mosaic of partly distinct vegetation zones within 

the floodplain of a river. Plant litter (leaves, fruits, flowers, 

branches) is likely to reflect the patchiness or zonation of the 

source vegetation. Differences in floristic composition, richness, biomass, diversity, and foliar physiognomy are 

reflected in the forest litter (Whitten, 1982; Proctor and others, 1983; Burnham, 1989; Greenwood, 1991).

Forest litter serves as the basis for reconstruction of the 

characteristics of fossil forests. Detailed knowledge of the 

spatial patterns in fossil vegetation can be gained by study of 

plant assemblages from different sedimentary facies deposited during a short time interval. In addition, the ecological 

preferences of extinct plants can be inferred from the restriction of plant organs to specific depositional environments 

(DiMichele and Phillips, 1985; Wnuk, 1985; Gastaldo, 

1987; Wnuk and Pfefferkorn, 1987). Plant-based biostratigraphic correlation can be hampered, however, by ecologically mediated, nonuniform distribution of plant species and 

litter among deltaic or floodplain sites. Compositional differences between stratigraphically superposed floras may be 

ecologically controlled, the result of evolutionary change, or 

due to climatic change. Independent data on the depositional 

environments represented can greatly improve the separation of ecological signals from evolutionary or climatic 

signals.

Recent developments in plant taphonomy (the study of 

the conditions under which paleontological records are preserved; Efremov, 1940) have focused attention on the depositional and degradative processes that can distort leaf and 

propagule assemblages in the fossil record (Spicer, 1980, 

1981; Collinson, 1983; Scheihing and Pfefferkorn, 1984; 

Ferguson, 1985; Greenwood 1992). The goal of taphonomic 

investigation is to provide a means to infer source vegetation 

from fossil deposits in spite of the distortion caused by preretrieval processes. From the insights provided by

Bl
B2 EVOLUTION OF SEDIMENTARY BASINS SOUTHWEST WASHINGTON AND NORTHWEST OREGON

taphonomic investigations, it is possible to use the patterns 

in the fossil record to provide clues about the biology of 

extinct organisms. It is this paleoecological application of 

taphonomy that has pervaded paleontology and that will persist, long after the practical questions in taphonomy have 

been resolved.

Plant-assemblage data from the Cenozoic fossil record 

have been used in two fundamental ways: (1) for paleoenvironmental reconstructions, including details of forest structure, climate, and species distribution, and (2) for 

biostratigraphy, in which taxa, scored as present or absent, 

are used to define concurrent range zones. A few well-collected plant-fossil assemblages commonly form the basis for 

Tertiary paleoecological reconstructions, and these are routinely augmented by smaller assemblages (MacGinitie, 

1969; Hickey, 1977; Axelrod, 1985). The effect of sourcevegetation heterogeneity (patchiness or zonation) on the 

resulting interpretation of micro- and mega-fossil assemblages rarely has been investigated in the ancient or the modern record of plant litter (however, see Parker, 1976; Wing, 

1981; Gastaldo, 1987; Spicer and Wolfe, 1987; Burnham, 

1989).

The research presented here has four major objectives. 

The first objective is to provide an updated characterization 

of the upper Ravenian (Eocene) flora of the Puget Group of 

Washington State. This characterization is based on 18 

plant-fossil assemblages from a limited geographic area 

encompassing a variety of deltaic depositional environments. The second objective is to determine the relative 

importance of (1) stratigraphic position and (2) environment 

of deposition on the floristic composition, abundance, and 

dominance of each of the Ravenian assemblages. The floristic composition and environmental implications of each 

assemblage are compared with those of the whole flora to 

determine the deviation from the regional vegetation represented by each subset. The third objective is to summarize 

the paleoecology of the upper Ravenian plant communities 

in terms of spatial relationships and presumed environment 

of deposition, and the fourth objective is to make recommendations about methodologies for Cenozoic paleoecological 

analyses of more limited exposures.

Acknowledgments. I would like to thank the following individuals for their comments on the manuscript in various forms: William A. DiMichele, Estella B. Leopold, 

Joanne Bourgeois, Alan Kohn, Melinda Denton, Jack A. 

Wolfe, Samuel Y. Johnson, and Richard G. Olmstead. For 

access to private land I thank Glenda McLucas and the 

Palmer Coking Coal Company. For guidance throughout the 

project I am grateful to William A. DiMichele. For financial 

support I thank the Geological Society of America, the 

Achievement Awards for College Scientist Foundation, and 

the National Science Foundation Pre-doctoral Fellowship 

Program.

122°15' 122°00' 121°45'

OUTCROP AREA OF 

THE PUGETGROUP

47°15' -

20 KltOMETERS

Figure 1. Generalized outcrop area of the Eocene Puget Group 

(dark shaded area), King and Pierce Counties, Washington. Modified from descriptions by Wolfe (1968), Vine (1969), and Mullineaux(1970).

STRATIGRAPHY OF THE 

PUGET GROUP

Outcrops of the Eocene Puget Group are exposed west 

of the Cascade Mountains in Washington State in a roughly 

rectangular area extending from near Morton on the south to 

the Newcastle Hills on the north, covering an area of about 

40 by 90 km (fig. 1). The Puget Group comprises arkosic 

sandstone, shale, and coal and locally abundant volcanic 

debris (Vine, 1969). The northern section of the Puget Group 

(in the area of Renton) has been divided into three formations that include (from bottom to top) sedimentary rocks of 

the Tiger Mountain Formation, dominantly volcanic rocks of 

the Tukwila Formation, and sedimentary rocks of the Renton 

Formation. The formational names have not been extended 

to the southern part of the basin, near the Green River, where 

the entire exposed sequence is sedimentary in character and 

the Tukwila Formation is missing. Six quadrangles comprising the major outcrops of the Puget Group were mapped and 

described by Vine (1969), Mullineaux (1970), and Yount 

and Gower (1991). Correlation between rocks from the two 

areas was made on the basis of plant fossils (Wolfe, 1968; 

Vine, 1969) and refined by Armentrout and others (1983).
HETEROGENEITY IN THE PLANT-FOSSIL RECORD B3

METERS FLORAL STAGES

Kummer 

Sandstone"

Section 

Studied

Gem and 

Harris Coals J

McKay -! 

Coal

-1,800

J ,200

-600

Lower

Upper

Middle

Lower

Upper

Lower

c 

o>

CO

QC

Fultonian

3Z

c 

CO

EXPLANATION

E3 Silt and clay g| Sandstone 

 Coal Es3 Igneous sill

Figure 2. Stratigraphic type section of the Eocene Puget Group 

from the Green River area, west-central Washington. Location of 

type section is shown in figure 4 as locality PG09. Type section 

modified from Vine (1969); floral stages from Wolfe (1968, 1977).

Paleobotanical analysis of the Puget Group, including a 

zonation based on the 1,890-meter-thick type section 

exposed in the southern Green River area and more scattered 

exposures to the north, was provided by Wolfe (1968), who 

named four formal paleobotanical stages (fig. 2) based on 

restricted and overlapping ranges of plant fossils. The stages 

subsequently were revised slightly to incorporate more complete data on Eocene plant-fossil assemblages from Alaska 

(Wolfe, 1977).

Invertebrate remains are less ubiquitous than plant fossils in the Puget Group but are locally abundant, particularly 

in the marine-influenced Tukwila Formation of the northern 

section (Durham, 1942; Mullineaux, 1970; McWilliams, 

1971). A few species of fresh- to brackish-water bivalves are

present in plant-bearing strata throughout the sequence. 

Marine bivalves and gastropods are present at localities lacking identifiable plant fossils (White, 1889; Durham, 1942; 

McWilliams, 1971). The rocks from which these marine 

organisms were derived were presumed by McWilliams 

(1971) to be stratigraphically equivalent to the lower Ravenian Tukwila Formation. Although geologic mapping by 

Waldron (1967), Waldron and others (1962), and Mullineaux (1970) indicates an older age for these marine, fossilbearing strata, newer mapping (Yount and Gower, 1991) 

indicates that correlation with the Tukwila Formation is 

correct.

Buckovic (1979) described the Paleogene depositional 

setting of western Washington in terms of Mississippi Deltastyle sedimentation. The Puget Group was designated as the 

delta plain deposits of the deltaic system, landward of the 

delta front and prodelta facies. Included within the delta 

plain deposits are distributary and interdistributary facies. I 

have interpreted the Ravenian-stage rocks of the Puget 

Group to represent facies within the upper delta plain (Burnham 1990). Recent field investigations by S.Y. Johnson 

(U.S. Geological Survey, written commun., October 1992) 

reveal numerous indications of marine influence in the deltaic sediments of the Puget Group that may constrain the 

depositional environments to the lower delta plain.

Absolute ages for the Puget Group were presented by 

Turner and others (1983), who proposed that the maximum 

duration of deposition of the Puget Group was 7.7 m.y. 

(41.2±1.8 to 45.0±2.1 Ma). The oldest possible age (47.1 

Ma) according to these determinations for the rocks referable 

to the Franklinian stage (fig. 2) would place the base of the 

Puget Group in the early middle Eocene subepoch or the 

early Lutetian age using the scales of Armentrout (1981), 

Berggren and others (1978, 1985), Haq and others (1987), 

and Cande and Kent (1992). Although the youngest radiometric age reported as acceptable by Turner and others 

(1983) is 41.2±1.8 Ma, this date was determined on the basis 

of ash partings approximately 1,100 m below the top of the 

type section. A minimum age of 35.2 Ma, which constrains 

the age of the top of the section, was derived from a volcanic 

flow overlying the Puget Group. These relationships are 

shown in figure 3. Only two radiometric ages are known 

from the intervening Ravenian and lower Kummerian part of 

the type section: a maximum age of 43.2±1.8 Ma from the 

rocks assigned to the lower Kummerian stage (Turner and 

others, 1983) and an age of 39.4±2.8 based on detrital zircons from a sandstone body within the upper third of the section studied for this report (Brandon and Vance, 1992). 

Because detrital zircons provide a maximum age of the 

source area (the age indicates the time that the source terrain 

was uplifted and cooled through the ~200±30°C isotherm), 

the date is consistent with both the K/Ar ages and the paleobotanical zonation. These ages constrain the top of the Puget 

Group to the upper Eocene, slightly older than the EoceneOligocene boundary (~34 Ma) as defined by Cande and Kent
B4 EVOLUTION OF SEDIMENTARY BASINS SOUTHWEST WASHINGTON AND NORTHWEST OREGON

RADIOMETRIC AGES 

Turner and others (1983)

29 ,

33 

36 

39 

42 

45 

48 

51 

54 ' 

MEGA-ANNUM

PALEOBOTANICAL STAGES, 

GREEN RIVER AREA

PALEOBOTANICAL AGES 

Wolfe (1981a, written commun., January 1993)

. 29

 33

 36

 39

 42

 45

 48

 51

54 

MEGA-ANNUM

Figure 3. Discrepancies between radiometric (K/Ar) and paleobotanical ages of rock units from the Eocene 

Puget Group, Washington. Diagonal-lined areas indicate the age-duration indicated by the two types of analyses. Shaded areas and dashed correlation lines are inferred from the studies cited. Base of the Puget Group is 

based on paleobotanical evidence and has been revised from written communication with J.A. Wolfe (January 

1993).

(1992) and Berggren and others (1992). The age estimates 

are in partial conflict with those of Wolfe (1978, 1981a), 

whose zonation puts the base of the Puget Group in the middle Eocene and the top of the group in the early Oligocene. 

Even the minimum estimate of the duration of the Puget 

Group based on the paleobotanical evidence (about 12 m.y.) 

does not allow concordance with the radiometric ages. Additional radiometric ages based on Ar-Ar analysis may help to 

resolve the age.

DESCRIPTION OF THE FIELD AREA

A section within the southern Puget Group was chosen 

to determine whether stratigraphic position or depositional 

environment had a stronger influence on the taxonomic composition of plant-fossil assemblages. The section is 40 km 

southeast of Seattle in the L-Bar Products silica quarry (fig. 

4). In this area, postdepositional folding and faulting has

produced a series of north- and east-trending anticlines and 

synclines. Beds dip 30°-80° W. along the axes of these 

structures; long stratigraphic sections can be measured easily 

along west-flowing rivers, quarries, and surface mines. The 

quarry section exposes more than 200 m stratigraphically 

(see fig. 2) in about 1 km of lateral exposure. The 200-meter 

section represents most of the upper Ravenian floral stage as 

designated by Wolfe (1977) (fig. 2). Based on average sediment accumulation rates for the Green River section, the 

200-meter section may represent as much as 3.5 m.y. (based 

on Wolfe, 198 la) or as little as 0.4 m.y. (based on Turner and 

others, 1983). The average sediment accumulation rates are 

0.06 m/1,000 years and 0.25 m/1,000 years, respectively. 

Both rates fit within the estimates reported by Sadler (1981) 

for fluvial environments, and the later rate is within the rate 

(0.4-0.6 m/1,000 years) recently estimated by S.Y. Johnson 

(written commun., October 1992) based on revisions of ages 

and stratigraphic correlations of the Puget Group. These sediment accumulation rates supersede those proposed for the 

Puget Group by Johnson (1985).
HETEROGENEITY IN THE PLANT-FOSSIL RECORD B5

122°15' 122°

47°30' -

T23N

T22N

T21N

R5E R6E R7E

Figure 4. Location of L-Bar silica quarry (18 plant localities) and two plant-fossil localities (PG04 and PG34) from road-cut exposures, 

west-central Washington. Locality PG09 is location of stratigraphic section shown in figure 2.

Eighteen plant-fossil localities were excavated within 

the quarry, and two additional localities (one early Ravenian 

and one Kummerian) were established at road cuts in the 

northern part of the Puget Group (fig. 4). The exposures, particularly those within the quarry, were chosen for analysis 

because stratigraphic relationships between plant localities 

could be observed directly in the field and because lateral 

facies relationships of individual beds could be traced for as 

much as 800 m.

DATA COLLECTION

STRATIGRAPHIC SECTIONS

Vertical sections were measured in the quarry and at 

both of the northern localities (localities 04 and 34, table 1). 

The lateral relationships between localities and the general

facies relationships within the quarry are shown in figure 5. 

Sedimentological features such as dominant grain size, variation in grain size, sedimentary structures, bioturbation 

(including rooting by plants), density of organic layering, 

and position in a local stratigraphic section were noted at 

each plant locality and were used to group localities into depositional facies (Burnham, 1990). The designation of facies 

types for each locality was thus independent of the taxonomic composition of the plant assemblages. The independence of the two data sets allows hypotheses about plant 

habitat preference and about depositional setting to be tested 

using the alternate data set.

Three major plant-bearing facies are present in the 

localities from the L-Bar quarry: lacustrine cutoff, floodbasin, and channel margin. Both floodbasin and lacustrine-cutoff facies can be subdivided further into what probably are 

higher- and lower-energy subenvironments. These subenvironments are distal crevasse splay (floodbasin), overbank 

floodbasin, low-energy lacustrine cutoff, and intermittently
B6 EVOLUTION OF SEDIMENTARY BASINS SOUTHWEST WASHINGTON AND NORTHWEST OREGON

Table 1. Depositional environment, species richness, and 

height above base of section for plant-fossil localities used in 

paleoecological analysis, Eocene Puget Group, Washington. 

[Localities are listed in stratigraphic sequence, from oldest to youngest]

Locality Depositional Meters above base 

no. environment of section

34

21

19

18

22

17

07

32

29

36

30

27

24

33

31

26

25

35

23

04

Distal splay (floodbasin

Distal splay (floodbasin)

Distal splay (floodbasin)

Channel margin

Intermittent lacustrine cutoff

Channel margin

Overbank floodbasin

Overbank floodbasin

Overbank floodbasin

Channel margin

Channel margin

Intermittent lacustrine cutoff

Channel margin

Low-energy lacustrine cutoff

Intermittent lacustrine cutoff

Distal splay (floodbasin)

Distal splay (floodbasin)

Low-energy lacustrine cutoff

Low-energy lacustrine cutoff

Overbank floodbasin

Unknown

210

210

195

190

190

144

143

141

110

64

64

64

49

44

30

26

15

15

Unknown

Species* 

richness

22

26

20

13

16

3

48

16

21

17

14

14

15

15

35

23

10

28

15

33

*Excluding all species for which there are fewer than two specimens.

active lacustrine cutoff. The five plant-bearing facies types 

(shown diagrammatically in fig. 6) have distinctive sedimentological attributes and have been described in detail (Burnham, 1990).

Lacustrine-cutoff deposits are of two types: low-energy 

and intermittently active. Both types of deposits are characterized by fine grain size, flat-lying laminations, and relatively thick layers of leaf material. In addition, laminae in the 

intermittently active deposits include coarser grain sizes 

transported by the occasional flooding of the subenvironment. This type of depositional setting is interpreted to represent abandoned (or partly abandoned) cutoff lakes.

Floodbasin deposits are divided into two types: overbank flood and distal crevasse splay (Burnham 1990). Both 

types of deposits are characterized by generally coarsening 

upward sequences of silt, sand, and clay commonly associated with plant-bearing layers. Lamination is not common, 

and bioturbation is abundant. The crevasse-splay deposits 

incorporate larger grain sizes and bear some ripple lamination. Both types of deposits are interpreted to represent 

floodbasin environments; the overbank flood deposits generally preserve litter from forest floor in finer sediments, and 

the crevasse-splay deposits preserve plants in the coarser 

sediment from the toe of a crevasse splay.

Channel-margin deposits generally contain larger grain 

sizes and more abundant ripple lamination than either of the 

other two main deposition types. Plant material is less abundant, and leaves are incorporated generally as isolated 

individuals. The deposits represent a range of environments

including proximal parts of crevasse splays, levees, upper 

point bars, and bar tops (Burnham, 1990).

PLANT-FOSSIL COLLECTIONS

Plant-fossil localities were designated as areas extending no more than 0.5 m vertically and 2 m laterally. At each 

locality, orientation of leaves on the bedding planes, presence of cuticle, density of leaves, and quality of preservation 

were noted. An average of 680 individual fossil leaf, fruit, 

and flower specimens were collected from each locality 

(table 1) and taken to the laboratory for analysis. All specimens were coated with acrylic spray coating to reduce desiccation of carbon films. Each specimen was assigned an 

individual locality and specimen number so that all specimens of each taxon could be referenced for taxonomic purposes. The number of specimens and number of taxa up to 

800 specimens per locality are summarized in figure 7 for all 

localities. The leveling of the curves indicates that, for most 

localities, the number of specimens collected represents an 

adequate sample of the taxonomic composition of the 

locality.

Specimens were assigned to morphological groups; in 

almost all cases, each group comprises a single species. Features of leaves such as size, shape, thickness, tooth type and 

size, major and minor vein patterns, presence or absence of 

drip tip, and arrangement of leaves and other organs on an 

axis were used to characterize each morphotype (taxon). 

Specimens of taxa previously reported from the Puget Group 

(Wolfe, 1968) were assigned to the previously named genus 

and species, but I give many previously unnamed taxa informal names related to some aspect of their morphology 

(abbreviations in appendix 1). An explanation of the morphotype abbreviations, formal names, and references for 

each of the taxa previously described, as well as brief informal descriptions for all taxa bearing morphotype names, is 

presented in appendix 4.

ADJUSTMENTS TO THE DATA SET

Taxa represented by only one specimen at a given locality were eliminated from all analyses presented here because 

the probability of misidentification of single leaves is high in 

angiosperm floras. Although some specimens that are 

clearly distinct were eliminated by this adjustment, the effect 

on the data set is minor. Only 95 specimens were eliminated. 

Of these 95, 22 were present as a single specimen at a single 

locality. For most analyses described here, only leaf taxa are 

included because of the marked variability in preservation of 

more fragile fruits, flowers, and seeds. All organ taxa were 

included in statistics on species richness, but only leaf taxa 

were included in statistics on diversity, leaf margins, and leaf 

size and in all multivariate analyses.
^ Leaves 

() Bivales

Bioturbation 

Coal bed

EXPLANATIO

|"^=^

[ **

^^^ -i2Sx( 

*<tv «* ^ ?

I I ' ' I

clay silt sand

I I ' ' i 

clay silt sand

600 meters 100 meters

SOUTH

Figure 5. Stratigraphic sections of the Eocene Puget Group, L-Bar silica quarry, west-central Washington, showing location of plant-bearing 

lationships of facies. Coal beds are labelled a through h on left side of column A. Location of L-Bar silica quarry is shown in figure 4.
B8 EVOLUTION OF SEDIMENTARY BASINS SOUTHWEST WASHINGTON AND NORTHWEST OREGON

LACUSTRINE 

CUTOFF

WELL-DRAINED 

LEVEE

SWAMP

FLOODBASIN

DISTAL 

SPLAY

Figure 6. Relationships of depositional environments in the upper delta plain, Eocene Puget Group, west-central Washington.

70

js

60 

50 

40- 

30

PQ

10-1

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0 100 200 300 400 500 600 700 800 

NUMBER OF SPECIMENS IDENTIFIED

Figure 7. Numbers of specimens and taxa for 20 plant-fossil localities from the Eocene Puget Group, west-central Washington. 

Locality is identified by two-digit number. Mean number of specimens censused per locality is 680; census data for as many as 800 

specimens are shown.

GENERAL CHARACTERISTICS OF 

THE UPPER RAVENIAN FLORA

Vegetational characteristics of the late Ravenian substage may be inferred best by grouping all localities together. 

This grouping provides a general framework against which 

environmental data derived from single localities or from 

different types of depositional environments may be compared. Localities 04 and 34 were eliminated from the analyses described in the following three paragraphs because they 

both clearly represent strata assigned by Wolfe (1968) to different substages of the Eocene than that represented by the 

18 L-Bar quarry localities.

A total of 10,199 specimens was evaluated for the characterization of the upper Ravenian leaf flora. The 92 taxa 

present include 74 dicotyledonous angiosperms, 8 monocotyledonous angiosperms, 7 ferns, 2 conifers, and 1 sphenopsid. Fifty percent of the dicots are entire-margined. The 

dicotyledonous leaf-size index (Wolfe, 1978) of 51 indicates 

a flora dominated by notophyllous-leaved (2,025-4,500 

mm2, after Webb, 1959) species. The proportion of the flora 

represented by evergreen species is difficult to determine 

from the data because many of the leaves cannot be assigned 

to an extant family (for which leaf abscission cycle would be
HETEROGENEITY IN THE PLANT-FOSSIL RECORD B9

known). Even some leaves assignable to an extant family 

cannot be designated as evergreen or deciduous because the 

extant family includes both evergreen and deciduous genera 

(Oleaceae, Fagaceae, Rosaceae, Euphorbiaceae, Tiliaceae), 

and the fossil is not clearly chartaceous (thin textured, typical of deciduous leaves) or sclerophyllous (thick textured, 

more typical of evergreen leaves). A rough estimate of 50 

percent evergreen taxa can be made, based on the thickness 

of the carbonaceous film or the thickness of the impression 

of the fossils. These foliar physiognomic parameters indicate that the 18 localities from the quarry section represent a 

Notophyllous Broad-Leaved Evergreen Forest (oak-laurel 

type forest) whose modern analog in Japan and China today 

grows under mesic conditions having mean annual temperatures of greater than 13°C and equable temperatures on a 

yearly basis (Wolfe, 1979). The relatively large leaf size 

indicates that summer mean temperatures may have been 

greater than 20°C.

In comparison, upper Ravenian assemblages from 

Alaska (Wolfe, 1977) are composed of 20 percent entiremargined species that were predominantly (75 percent) 

deciduous (table 2). These data indicate that late Ravenian 

Alaskan forests represented the warm end of the Mixed Mesophytic zone of Wolfe (1977, 1978). The lower and middle 

Ravenian assemblages from Alaska have entire-margin percentages of 65 percent and 54 percent, respectively, and are 

inferred to represent Paratropical Rainforest and Notophyllous Broad-Leaved Evergreen Forests (table 2) (Wolfe, 

1977). In comparison to the Puget Group, the Alaskan leaf 

assemblages suggest that deterioration of climate during the 

Eocene was more pronounced at high latitudes than at the 

coastal position and paleolatitude of the Puget Sound.

Other upper Ravenian floral localities from North 

America include the Copper Basin flora of Nevada (Axelrod, 

1966), the Middle Clarno assemblage from central Oregon, 

and the Lower Cedarville flora of northern California 

(Wolfe, 198la). All of these floras have low entire-margin 

percentages (25-40 percent); thus the coastal-lowland, upper 

Ravenian Puget Group assemblages are distinctive with 

respect to the more inland and upland floras represented in 

Nevada, Oregon, and California. The upland Fultonian 

Republic flora from eastern Washington (Wolfe and Wehr, 

1987) also shows a lower percentage of entire-margined taxa 

and a smaller leaf size than floras of the upper Ravenian 

Puget Group. The slightly younger Kummerian Comstock 

flora of Oregon represents a more coastal, warm-mesic 

assemblage similar to that from the Puget Group (table 2).

ANALYSIS OF PLANT 

DISTRIBUTION PRESENCEABSENCE DATA

Several types of analysis were performed to determine 

whether depositional environment or stratigraphic position 

had the stronger control on the floristic composition of the

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BIO EVOLUTION OF SEDIMENTARY BASINS SOUTHWEST WASHINGTON AND NORTHWEST OREGON

plant-fossil assemblages. All 20 localities are included in the 

following analyses, and the following facies are included: 

floodbasin, which is divided into overbank floodbasin and 

distal crevasse splay; lacustrine cutoff, which is divided into 

intermittently active lacustrine cutoff and low-energy lacustrine cutoff; and channel margin.

For most analyses, no differences could be detected 

between floras from the two lacustrine-cutoff subenvironments or between floras from the two floodbasin subenvironments. Therefore, in the tabulations of assemblages that 

follow, the floodbasin assemblages are grouped together and 

the cutoff assemblages are grouped together.

SPECIES RICHNESS

For the purposes of this report species richness is 

defined to indicate the number of species present in a given 

area. To assess the importance of spatial and temporal 

changes, the species richness of each of the 20 plant-fossil 

localities was plotted with respect to facies type (fig. 8A) and 

stratigraphic position (fig. 85). The mean species richness 

per locality is 20.2. Assemblages from channel-margin 

localities have significantly lower (a=0.05) mean species 

richness (12.4) than those from floodbasin localities (24.3). 

The intermediately rich lacustrine-cutoff assemblages are 

not statistically differentiable from either floodbasin or 

channel-margin floras in species richness (a=0.5). The middle third of the stratigraphic section (fig. SB) contains localities (33,24,27, 30, 36) that have lower than average species 

richness (not statistically lower than the other localities as a 

group, a=0.05) that may indicate a short interval during 

which species richness was lower. These five localities, 

however, represent channel-margin and lacustrine-cutoff 

facies, both of which tend to contain floral assemblages having lower species richness values than floodbasin assemblages (fig. 8A). Floodbasin assemblages from this interval 

are not available to differentiate between the two explanations for lowered species richness.

SPECIES DIVERSITY

Species diversity is a measure of the number of species 

present in a sample or community weighted by the number 

of individuals of each species in that sample or community 

(Pielou, 1975). A high level of diversity describes a community in which plants are apportioned equally among a large 

number of species. Diversity measures thus take into account 

the probability of encountering a single individual of each 

species in a sample and are not the same as species richness. 

The use of this type of information-theory diversity measure 

has come into question on theoretical grounds (Hurlbert, 

1971; Peet, 1974) and is used herein only to illustrate differences among similarly collected samples rather than 

between different sample sizes and sampling regimes.

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LOCALITY NUMBER BY STRATIGRAPHIC 

B POSITION

Figure 8. Species richness by locality for 20 plant-fossil localities from the Eocene Puget Group, west-central Washington. Average richness (20.2 per locality) for the 20 localities is plotted as 

a horizontal line. A, Localities grouped by facies type and by 

stratigraphic position within facies type. B, Localities grouped by 

stratigraphic position.

Diversity of each of 20 localities from the Puget Group 

is shown in figure 9 using the Shannon-Wiener index, 

designed to estimate the diversity of a community from a 

limited sample (Pielou, 1975). The average diversity of 

channel-margin assemblages is low (0.59), and, even if the 

very low diversity locality 17 is omitted, the average 

diversity of channel-margin assemblages is lower (0.73) 

than that of either floodbasin (0.97) or lacustrine-cutoff 

(0.82) assemblages.

LEAF MARGINS OF ANGIOSPERM TAXA

The positive association between the percentage of 

woody, dicotyledonous species in a flora having entiremargined leaves and mean annual temperature of a floristic
HETEROGENEITY IN THE PLANT-FOSSIL RECORD Bll

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55 LOCALITY NUMBER BY FACIES TYPE

Figure 9. Shannon-Weiner diversity index (Pielou, 1975) for 20 

plant-fossil localities from the Eocene Puget Group, west-central 

Washington, grouped by facies type and, within facies type, by 

stratigraphic position.

region was noted by Bailey and Sinnott (1915, 1916) and 

quantified by Wolfe (1971, 1979). The percentages of species having entire margins are higher in modern floras from 

warm, mesic areas, and lower in floras from areas of lower 

mean annual temperatures. This correlation has allowed 

paleobotanists to suggest mean annual temperature values 

for Tertiary floras without a lengthy taxonomic analysis of 

each locality (Wolfe 1971, 1981b). A stratigraphic succession of floras then can be analyzed for evidence of climatic 

trends.

Low numbers of taxa can adversely affect the accuracy 

of entire-margin percentages from Tertiary floras. Wolfe 

(1971,1981b) suggested using a minimum of 30 taxa for calculating margin percentages. Five of the localities plotted in 

figure 10 have less than 15 dicotyledonous taxa and are 

marked with an asterisk to indicate that the number of species present is probably inadequate for determining paleotemperatures based on the single localities alone.

Percentages of entire-margined species are plotted for 

the 20 plant-fossil localities from the Puget Group, grouped 

by facies (fig. 10A) and by stratigraphic position (fig. 105). 

The average per locality percentage of entire-margined species is 49.3 percent (very close to the 50 percent entire margins recorded for all taxa in the 18 L-Bar quarry localities). 

Assemblages from the floodbasin localities deviate very little from the total mean percentage of entire margins, whereas 

assemblages from lacustrine-cutoff localities are quite variable, from 25 percent to 87 percent entire (fig. IOA). Channel-margin assemblages tend to have lower entire-margin 

percentages (average 41.9 percent), as has been predicted 

(MacGinitie, 1953; Wolfe, 1979). Locality 18 is aberrant 

with respect to other channel-margin localities, having an 

entire-margin percentage of 60. The locality has a low

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LOCALITIES BY STRATIGRAPHIC POSITION

Figure 10. Percentage of species having entire-margined leaves 

for 20 plant-fossil localities, Eocene Puget Group, west-central 

Washington. Average entire-margin percentage for the 20 localities 

is 49.3 percent. A, Localities grouped by facies type (see Burnham, 

1990) and, within facies type, by stratigraphic position. B, Localities grouped by stratigraphic position. Asterisks indicate localities 

having species richness, <15.

number of species, which may contribute to this high percentage, but the taxonomic composition also shows marked 

similarities to floodbasin assemblages, which may indicate 

that the higher entire-margin percentage is valid and not an 

artifact of low species richness. This locality is unusual with 

respect to other channel-margin assemblages, as is discussed 

later in greater detail.

There is no clear relationship between leaf-margin percentage and stratigraphic position (fig. lOfi). A sequence of 

lower entire-margin percentages is present in the middle 

third of the section. Of the eight lower than average percentages recorded from locality 24 through locality 22, the five 

lowest are from assemblages of channel-margin and lacustrine-cutoff facies. This decrease in percentage of taxa having entire-margined leaves in the middle of the section, if 

representative of mean annual temperature, could represent
B12 EVOLUTION OF SEDIMENTARY BASINS SOUTHWEST WASHINGTON AND NORTHWEST OREGON

Table 3. Leaf-size classes.

[Fom Webb (1959), Wolfe (1985), and Wolfe and Upchurch (1987). 

Leaf size (LSI) can be calculated from the percentage of leaves in the 

classes listed using the equation (Wolfe, 1978):

LSI={ [percentage microphyllous + 2(percentage notophyllous)

+ 3(percentage mesophyllous) + 4(percentage macrophyllous)]

- 100} x 0.5

80 -

70 4

FLOODBASIN LACUSTRINE CHANNEL! 

CUTOFF I MARGIN

Class

Microphyll 

Notophyll 

Mesophyll 

Macrophyll

Leaf dimensions 

(centimeters)

<20.25 

20.25^5.00 

45.00-100.00 

> 100.00

Leaf length* 

(centimeters)

<8 

8-12 

12-26 

>26

*Length applies to leaves having basically elliptic shape.

a decrease in temperature of 4°C (Wolfe, 1979), altering the 

forest classification from Notophyllous Broad-Leaved Evergreen to between Notophyllous Broad-Leaved Evergreen 

and Mixed Mesophytic. Of the nine localities in the middle 

of the section that include this possible cooling trend, six 

represent channel-margin and lacustrine-cutoff environments, which have, on average, lower entire-margin percentages. The three floras from floodbasin facies (29, 32, 7) do 

not indicate a lowering of mean annual temperature. Thus, 

paleoenvironment, rather than climatic change, controls the 

distribution of taxa and thus of entire-margin percentages.

LEAF SIZE OF ANGIOSPERM TAXA

Several studies suggest a positive correlation between 

leaf size and climatic parameters (Dolph and Dilcher, 1979, 

1980a, b; Wolfe, 1979, 1990; Greenwood 1992). In mesic 

areas, leaf size tends to increase with an increase in mean 

annual temperature. This relationship may hold only for 

areas in which the cold-month mean temperateure is higher 

than -2°C (Wolfe, 1979). A leaf-size index was proposed by 

Wolfe (1978, fig. 5) to classify both fossil and extant plant 

assemblages. The average size class of each dicotyledonous 

taxon is determined (after Webb, 1959), and the percentage 

of the dicotyledonous flora in each size class is calculated. 

The equation for leaf-size index (LSI) (Wolfe, 1978; Wolfe 

and Upchurch, 1987; Greenwood, 1992) is:

LSI={ [percentage microphyllous + 2(percentage notophyllous) 

+3(percentage mesophyllous) + 4 (percentage macrophyllous)] 

-100} x 0.5 

Dimensions for each leaf-size class are listed in table 3.

Leaf-size indices for the 20 floristic assemblages under 

consideration from the Puget Group are plotted with respect 

to facies (fig. 11A) and stratigraphic position (fig. 1 IB). The 

average leaf-size index for all 79 dicotyledonous leaf taxa is 

51. The average dictyledonous leaf-size index for all localities is 57. This slight difference indicates that the larger 

leaved taxa are more frequently represented in the assemblages than are smaller leaved taxa. Both values (all 

dicotyledonous taxa versus locality averages) indicate a

4 25 26 29 32 7 19 21 34 23 35 31 33 27 22 24 30 36 17 18

LOCALITIES BY FACIES TYPE

80-

70-

4 23 35 25 26 31 33 24 27 30 36 29 32 7 17 22 18 19 21 34

B LOCALITIES BY STRATIGRAPHIC POSITION

Figure 11. Leaf-size index of dicotyledonous taxa for 20 plantfossil localities, Eocene Puget Group, west-central Washington. 

Average leaf-size index is plotted as a horizontal line; leaf-size index as calculated by Wolfe (1978; see text for discussion). A, Localities grouped by facies type (designation in Burnham, 1990), 

and, within facies type, by stratigraphic position. B, Localities 

grouped by stratigraphic position.

forest including taxa having predominantly Notophyllous 

leaves. There is neither a trend nor a substantial difference 

within localities derived from specific depositional settings 

or from a particular stratigraphic position (fig. 11). The lack 

of any trends supports the idea that the mid-section difference in species richness and percentage entire margin is most 

likely due to facies effects. In the assemblages from the 

Puget Group, the leaf-size index does not appear to be sensitive to environmental differences.

CONIFERS, PTERIDOPHYTES, AND 

SPHENOPSIDS

Depositional environments appear to have strong control on the distribution of the sphenopsid, pteridophytes, and 

conifers at the 20 Ravenian localities (fig. 12). Assemblages
HETEROGENEITY IN THE PLANT-FOSSIL RECORD B13

4 25262932 7 1921342335313327222430361718

LOCALITIES ORDERED BY STRATIGRAPHIC 

POSITION WITHIN FACIES TYPE

EXPLANATION

Equisetum [H Conifers Ferns

Figure 12. Species richness of ferns, conifers, and Equisetum in 

20 plant-fossil localities from the Eocene Puget Group, west-central Washington. Localities are grouped by facies type, after designations in Burnham (1990).

from channel-margin facies have none of the 10 nonangiosperm taxa: all are in the floras from floodbasin and 

lacustrine-cutoff facies. The two conifers are present in the 

floras from five floodbasin localities and one lacustrine-cutoff locality. The conifers probably inhabited the stable backswamps or back-levee areas near floodbasins. The seven 

pteridophytes and Equisetum are found in floras from floodbasin and lacustrine-cutoff localities. Pteridophytes normally are present in low frequencies (<5 percent of 

specimens from a single locality), but at two distal-splay 

(floodbasin) localities (25 and 26) ferns make up more than 

20 percent of the specimens. The pteridophyte distribution 

may have two interpretations: (1) channel margins were not 

stable enough to allow fern rhizomes or gametophytes to 

become established, and areas of lush fern growth were 

restricted to floodbasins, levees, backswamps, and the more 

tranquil floodplain areas; or (2) higher energy depositional 

environments destroy finely divided pteridophyte foliage, 

which can be more fragile than that of angiosperms. Burial 

of ferns by sediment may have occurred only during rapid 

sedimentation events, as might be expected in distal splays. 

Both explanations probably account for the distribution 

observed.

COMPARISON OF FLORISTIC 

ASSEMBLAGES

Sorenson's Index of Similarity (also, known as Dice's 

Coefficient; Sneath and Sokal, 1973) was used to calculate

the similarity in paired species lists between all localities: the 

higher the value of the index, the greater the similarity 

between the list of species in the two localities compared. A 

total of 190 pairwise comparisons can be made among the 

localities. Figure 13A shows all floristic comparisons; each 

histogram increment is coded to indicate the depositional 

facies from which the two floras compared were drawn. Similarities between assemblages derived from floodbasin facies 

are much greater than any other single type of comparison. 

The average similarity between floodbasin assemblages 

(mean similarity = 41 percent) is the highest of all comparisons. There is substantial difference between the similarity 

distribution for floodbasin-floodbasin comparisons and that 

for lacustrine cutoff-lacustrine cutoff comparisons. This difference indicates that although lacustrine-cutoff assemblages are similar physiognomically to floodbasin 

assemblages, lacustrine-cutoff assemblages are dissimilar to 

one another with respect to floristic composition. All other 

types of comparisons show distributions that are intermediate between these two endpoint types of distributions, 

including channel margin-channel margin comparisons.

Stratigraphic position of plant-fossil localities in the 

Puget Group sequence would be expected to have some control on the degree of floristic similarity between localities if 

climatic or evolutionary change had occurred during the time 

of deposition. To determine whether Stratigraphic position 

had an effect on the similarity among floras, I plotted the 

same Sorenson's Indices on figure 135 and coded them to 

represent the Stratigraphic distance between the two samples 

compared. If Stratigraphic distance had an effect on floristic 

similarity, the more closely spaced samples would have 

higher similarity values. Conversely, if Stratigraphic position 

had little control on the floristic composition of localities, an 

even distribution of similarity values would be expected. No 

stratigraphically controlled difference can be detected in the 

upper Ravenian sequence, whereas depositional environment (fig. 13/4) appears to have a strong control on species 

composition.

SUMMARY OF DATA ON PRESENCEABSENCE OF SPECIES

Overall, the greatest similarity in floristic composition 

between assemblages from the 20 localities censused is 

between those collected from floodbasin deposits. Assemblages from lacustrine-cutoff and channel-margin localities 

are less similar to one another (lacustrine cutoff-channel 

margin), less similar to themselves (lacustrine cutoff-lacustrine cutoff and channel margin-channel margin), and less 

species rich and, on average, include a lower proportion of 

Pteridophytes and Coniferophytes. Influence of Stratigraphic 

position is not apparent (figs. 6B, SB, 105, 135); floras from 

floodbasin facies have the highest similarity in composition 

to one another, regardless of Stratigraphic position.
EVOLUTION OF SEDIMENTARY BASINS SOUTHWEST WASHINGTON AND NORTHWEST OREGON

10 15 20 25 30 35 40 45 

SORENSON'S INDEX [2C/ (A/1 + A/2)]

55 >60

STRATIGRAPHIC DISTANCE 

(METERS) BETWEEN ASSEMBLAGES

15 20 25 30 35 40 

SORENSON'S INDEX [2C/ (A/1 + A/2)]

50 55 >60

Figure 13. Sorenson's Index of Similarity for all comparisons of 20 plant-fossil localities from 

the Eocene Puget Group, west-central Washington. Each histogram increment represents a single 

comparison. C is number of species in common between two localities; Nl is number of Species in 

locality 1; and N2 is number of species in locality 2. A, Histogram increments coded according to 

sedimentary facies from which the two assemblages compared are derived. Facies: LC, lacustrine 

cutoff; CM, channel margin; FB, flood basin; B, Histogram increments coded according to the 

stratigraphic distance (in meters) between the two assemblages compared.

The patterns may be interpreted in light of the types and 

distribution of facies represented by the deposits. Lacustrine 

cutoffs represent individually isolated points on a fluvialdeltaic plain. Due to vegetational heterogeneity in such lowland plains, the floras surrounding these environments 

potentially will differ from each other in species composition. In contrast, channel-margin assemblages are drawn 

from vegetation zones that parallel the course of the river and 

thus have population continuity through the floodplain, even 

though the channel-margin deposits themselves may not be

continuous. Floodbasin environments best represent a cross 

section of the total local flora. Leaves are derived from overhanging plants, as well as washed into the basin by crevassesplay activity or overbank flooding. Notably absent or infrequent in floodbasin facies are channel-margin dominants 

(for example, Salix). These absences are interpreted to mean 

that some of the streamside taxa were restricted to the channel side of the levee and were less likely to have been transported into the floodbasin. Similar patterns of plantmegafossil deposition have been noted in modern
HETEROGENEITY IN THE PLANT-FOSSIL RECORD

environments (McQueen, 1969; Birks, 1973; Scheihing and 

Pfefferkorn, 1984). Floodbasin deposits preserve what 

appears to be only a partially autochthonous flora, derived 

from the levees and low-lying back-levee areas. The area 

covered by floodbasins may have been extensive, as in modern delta plains (Scheihing and Pfefferkorn 1984), which 

would effectively homogenize a large, diverse flora when 

sampled at several different points.

ANALYSIS OF PLANT DATA 

TAXON ABUNDANCE

The abundance of leaf specimens of each taxon in 

plant-fossil collections depends on proximity of source plant 

to depositional site, ease of fragmentation, cyclicity of 

abscission, and rate of degradation. Presence-absence data 

treat each taxon equally, eliminating the variability in abundances that may be caused by leaves composed of many leaflets or by synchronous leaf abscission of particular species. 

Abundance data, however, do not overemphasize rare species as do presence-absence data. A direct measure of taxon 

abundance can help to differentiate samples derived from 

vegetation having similar taxonomic compositions but different proportions of taxa. Dominant species are most important in analyses using abundance data. Abundance data can 

be analyzed using two general groups of methods: ordination 

and cluster analysis. These techniques reduce multidimensional data to a small number of dimensions so that the major 

variation can be plotted and viewed easily. Both methods are 

used here to illustrate the abundance data from the 20 localities sampled in the Puget Group.

ORDINATION OF LOCALITIES

METHODS

Ordination is a procedure by which complex, multidimensional community data are summarized using a low 

number of axes (1 to 3) on which similar localities are 

grouped close together and dissimilar localities are far apart 

(Gauch, 1982). For these analyses, I used both Reciprocal 

Averaging (also known as Correspondence Analysis) and 

Detrended Correspondence Analysis (Hill and Gauch, 1980; 

Gauch, 1982). Both methods are iterative techniques in 

which sample scores are averages of species scores and chisquared distances are used to maximize the correlation 

between samples and species. In Detrended Correspondence 

Analysis, the axes are rescaled to correct for a tendency for 

the second- and higher-order axes to be correlated with the 

first axis and for the ends of axis 1 to be compressed relative 

to the center as a result of the typical Reciprocal Averaging 

procedure (Hill and Gauch, 1980; Gauch, 1982; Wartenberg 

and others, 1987). Results obtained using the two methods

CM

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250 -

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150 -_

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 Channel margin

(22 X Lacustrine

24 * 23 X 0 36

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19 01

^21 D 29

D 34

n25 * 1 1 1 1 1 1 1 1 ] 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

Figure 14. Axes 1 and 2 from Detrended Correspondence Analysis 

(DECORANA) of 20 plant-fossil localities from the Eocene Puget 

Group of west-central Washington. Data used are log-transformed 

abundance counts of 92 taxa (appendix 1). Eigenvalues: axis 1, 

0.386; axis 2, 0.295.

are very similar for axes 1 and 2, indicating that the first two 

axes are not significantly correlated when using Reciprocal 

Averaging without rescaling.

Localities were ordinated using both Reciprocal Averaging and Detrended Correspondence Analysis based on 

abundance data that were log-transformed prior to analysis. 

Log-transformation was used because of the high abundance 

of certain species, particularly in channel-margin environments (appendix 1). These high abundances, if untransformed, distort the position of the localities along the axes 

such that single localities having abundant, almost unique 

species form endpoints and all other localities lump together 

at some point between the outliers.

RESULTS AND DISCUSSION

Axes 1 and 2 for Detrended Correspondence Analysis 

are plotted in figure 14. Floodbasin localities are grouped in 

the lower left, channel-margin localities in the upper left, and 

lacustrine-cutoff localities in a broad band through the center. Floras derived from floodbasin localities within the 

lower left quadrant of the plot cannot be secondarily subdivided. The lack of distinct separation between floras derived 

from lacustrine-cutoff and channel-margin facies indicates 

that, based on numerical abundance of foliage, the two types 

of facies have substantial overlap in their floras. The assemblages from lacustrine-cutoff deposits generally differ both 

from each other (hence the broad band on axis 1) and from 

those of other facies (especially localities 27 and 33). One 

floodbasin locality, 25, has a low species richness and stratigraphically overlies a prominent coal seam. The flora is an
B16 EVOLUTION OF SEDIMENTARY BASINS SOUTHWEST WASHINGTON AND NORTHWEST OREGON

outlier, low in species richness, but is most closely allied to 

the rest of the floodbasin assemblages and may represent a 

hypoautochthonous assemblage from a clastic swamp. The 

low similarity values of locality 25 compared to other floodbasin assemblages may result from few taxa from levees and 

well-drained floodplain areas being represented in the 

assemblage.

Locality 18 (a channel-margin assemblage) is worthy of 

special mention because of its central position on the ordination plot. The sedimentological features of this locality conform well to a channel-margin facies (planar and ripple 

cross-lamination, isolated leaves, fine-sand grain size); however, its floristic attributes indicate its similarity to floodbasin assemblages. Leaves are taxonomically allied to those of 

floodbasin floras (relatively high Sorenson's Indices; appendix 2). They may represent either plants from an environment that is transitional between channel-margin and 

floodbasin environments or an allochthonous assemblage 

originating in the source area of the floodbasin floras and 

incorporated into a near-channel environment. The strong 

similarity between sedimentary features at locality 18 and 

those of other channel-margin facies suggests that locality 18 

represents a part of a crevasse-splay deposit that incorporated taxa from the floodbasin. The presence of a floodbasinlike assemblage in channel-margin deposits indicates that 

the floodbasin floras represent the dominant regional vegetation and can be incorporated into any type of deposit because 

of their dominance on the floodplain.

METHODS

Spearman's Rank-Order Correlation Coefficient (Nie 

and others, 1975) was calculated for all pairs of sample 

localities, using quantitative data, to produce a matrix of 

similarities (appendix 3). The coefficient is derived by comparing the rank order of species between pairs of localities. 

Localities having similar dominance hierarchies (the rankorder lists) score as more similar to one another than those 

having dissimilar rank orderings of species. This comparison 

of species rankings between pairs of localities produces a 

measure that expresses the similarity based on dominance 

hierarchy rather than on absolute abundances. In contrast, 

Euclidean or normalized-Euclidean distance measures, 

which use quantitative data directly, are strongly biased by 

samples containing species having very high abundance values. Both unweighted and weighted (Sneath and Sokal, 

1973) pair-group methods were used to cluster the similarity 

measures; these produced almost identical results.

RESULTS AND DISCUSSION

Results of the cluster analysis (unweighted-pair group 

method) based on Spearman's Rank-Order Correlation

70- 

60-

1 40-

fcO

UJ P30- 

<2

LU

^ 20-

10-

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4 352 31 73 024 36 2 227 3

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EXPLANATION 

O Floodbasin Lacustrine ^.Channel margin

Figure 15. Cluster Analysis (UPGMA) of Spearman's Rank-Order Correlation Coefficients for 20 plant-fossil localities from the 

Eocene Puget Group, west-central Washington. Taxa are ranked 

according to abundance. Dominance lists form the basis for the 

similarity matrix (appendix 3). Localities are coded according to 

the depositional facies from which they were derived (Burnham, 

1990).

Coefficients are shown in figure 15. Localities cluster into 

two large groups and a small outlier, indicated by the bars in 

figure 15. The large group to the left includes all nine floras 

from floodbasin deposits, one from a channel-margin 

deposit, and two from lacustrine-cutoff deposits. Assemblages from floodbasin facies make up 85 percent of this 

group. The group to the right consists entirely of floras from 

lacustrine-cutoff and channel-margin facies. Localities 27 

and 33 are outlying, as they are in most analyses, underscoring the variability in species composition and dominance 

from lacustrine-cutoff facies. The groupings reflect neither 

stratigraphic position nor species richness and can be 

explained most easily on the basis of their shared depositional environments.

Localities 19 and 21, which are from the same stratigraphic level and represent floodbasin environments (distal 

splay), are most similar to one another (similarity=73), as 

might be expected. Floodbasin localities 7 and 29 are separated by about 10 m of section and cluster at similarity=38. 

Localities 32 and 7, however, are separated by less than 3 m 

of section and both represent overbank-floodbasin subfacies 

of the floodbasin facies, yet locality 31 (lacustrine-cutoff 

facies) clusters more closely to locality 32 (similarity=46) 

than does locality 7 to locality 32 (similarity=38). Overall, 

the floodbasin group holds together, although the average 

similarity for the cluster is fairly low (similarity=22). In contrast, the group of channel-margin and lacustrine cutoff environments generally does not reflect proximity of 

stratigraphic position or depositional environment. It is clear 

that the pattern of dominance is more similar among
HETEROGENEITY IN THE PLANT-FOSSIL RECORD B17

floodbasin localities than among lacustrine-cutoff localities. 

High similarity of dominants among floodbasin localities 

indicates that the assemblages may have been derived from 

a large rich flora dominated by a few (perhaps about 20) species. The assemblages are homogenenous, probably due to 

natural sampling and sedimentary processes responsible for 

the floodbasin deposits. The low level at which the two 

major clusters are linked (12 percent) indicates a general dissimilarity between localities that could be due to floristic 

richness or to the amount of time represented by the 

sequence. The clustering method used for vegetational analyses is effective, particularly for visualizing the dominance 

data, but probably has no real advantages over ordination 

procedures.

ENVIRONMENTAL HETEROGENEITY 

IN THE PUGET GROUP

Species present in the 20 localities of the Puget Group 

are probably controlled primarily by the depositional environment from which they were derived. The frequency with 

which taxa are present at localities, coupled with the large 

number of total taxa recorded for the stratigraphic section, 

indicates that taxa are not distributed uniformly among localities.

The following factors are most likely to have influenced 

this distribution of taxa.

1. Plant-species distribution is patchy. The consequence of differing environmental tolerance among plant 

species in a heterogeneous environment is vegetational heterogeneity. Plant litter reflects the differentiation of species 

preferences for specific environmental sites. This type of differential litter distribution by microhabitat occurs in modern 

environments and has been shown to be due to source-plant 

zonation and patchiness among the subenvironments along 

the Rio San Pedro of southern Mexico (Burnham, 1989).

2. Transport and degradation of plant litter is not 

equal for all species. Plant parts of different taxa degrade differentially following abscission, and the differential hydrodynamic properties of leaves have the potential to sort taxa, 

causing them to be present patchily in a group of samples. 

Within a single sample, the high abundance of rare taxa is 

caused by proximity of the source plant to the fossil locality 

or by similar fluid-dynamic properties of leaves of a single 

species (Spicer and Greer, 1986; Spicer and Wolfe, 1987; 

Burnham and others, 1992).

3. Sampling scale affects our perception of species 

distribution. The small scale of outcrop sampling for paleobotanical specimens can make a group of samples appear 

heterogeneous. Most samples are derived from a limited vertical and lateral extent that may reflect only the plants immediately surrounding the site. Heterogeneity of the standing

vegetation is commonly on a scale large enough that a 

paleobotanical sample cannot reflect the major patterns. A 

limited number of plants can contribute to litter at a small 

site. This factor was observed to affect the reliability of single 0.5-m2 litter samples used for reconstruction of the 

standing vegetation in the modern floodplain of the Rio San 

Pedro (Burnham, 1989). The effective source area for 

autochthonous deposits is only on the order of 0.1 to 0.125 

hectare (Burnham and others, 1992).

The presence-absence data and the dominance patterns 

(table 4) indicate that a high level of floodplain heterogeneity existed but that the scale at which the heterogeneity is 

sampled affects our perception of it. Cutoff meanders vary 

greatly in species composition, possibly because they are 

environments that incorporate such a small part of the floodplain vegetation. Floodbasin samples are less heterogeneous 

because they are drawn from a larger and more continuously 

distributed source flora and thus incorporate regionally dominant taxa rather than local dominants. The larger scale represented by the deposits from floodbasins is probably the 

most reliable for reflection of the regional vegetation. Channel-margin floras have a smaller number of dominant taxa 

(2-4) than lacustrine-cutoff and floodbasin assemblages 

(2-6). Two taxa (Salix and Cercidiphyllum-Trochodendron 

Complex) tend to dominate each channel-margin locality. 

Thus, although less diverse than assemblages from other 

facies, channel-margin assemblages are relatively homogeneous. This homogeneity is interpreted to indicate that the 

channel-margin assemblages are derived from a source flora 

that is homogeneous relative to that from which the lacustrine-cutoff floras are derived. Some of the observed homogeneity of channel-margin floras could have been caused by 

transport and mixing in the channel, although this latter 

explanation requires a transport pattern that can mix all taxa 

in a similar manner.

DISCUSSION

SPECIES DISTRIBUTION IN THE 

UPPER RAVENIAN PUGET GROUP

The preceding analysis of vegetational patterns from 

upper Ravenian rocks of Washington State suggests that 

paleoenvironment, as recorded by depositional facies, was 

the major factor influencing the plant-species composition 

and dominance throughout the stratigraphic sequence and 

that, in contrast, the effect of stratigraphic position was 

minimal. Although the stratigraphic sequence is thin (200 

m) relative to the complete section (1,890 m) described 

from the Puget Group, the lack of a stratigraphic trend here 

suggests that depositional environments may have had 

some control on changes in floral assemblages observed in
B18 EVOLUTION OF SEDIMENTARY BASINS SOUTHWEST WASHINGTON AND NORTHWEST OREGON

Table 4. Dominant taxa (5 percent or greater relative abundance) at 20 plant-fossil localities from the Eocene Puget Group,

Washington.

[Taxa and abbreviations for informally named taxa are given in appendix 4]

Floodbasin

Locality 04

"Cocculus" 

Menispermites 

Viburnum 

Glyptostrobus 

Hypserpa

Locality 07

CTCC

Pugetia 

Chaetoptelea 

Alnus 

WPTA

Locality 19

Carya 

Platycarya 

Alnus 

"Artocarpoides " 

Hypserpa

Locality 29

Viburnum 

Pugetia 

Dryophyllum 

"Rhamnites" 

Bursera

Locality 21

Carya 

Pterocarya 

Dryophyllum 

Glyptostrobus 

Hypserpa 

"Artocarpoides

Locality 32

CTCC

Pugetia 

3FHy

Locality 2

Carya 

Metasequoia 

Dryophyllum 

Glyptostrobus 

Hypserpa 

" Cyathea

Locality 34

Metasequoia 

Equisetum

Locality 26

M45m 

M23m 

Viburnum 

Dennstaedtia 

TLWP 

Pugetia

Lacustrine cutoff

Locality 22

Platycarya 

Acer 

CTCC 

Vinea 

Salix 

E2Br

Locality 23

Salix 

M45m 

M23m

Locality 27

Liquidambar 

Alnus 

Zingiberopsis 

Betula

Locality 31 Locality 33 Locality 35

Dryophyllum Zingiberopsis "Rhamnites" 

Lila 31mo Fraxinus 

Meme BrdM Anacardites 

FBEE Salvinia Pterocarya 

Goweria

Channel margin

Locality 17

Salix 

CTCC

Locality 18

Dryophyllum 

CTCC 

CdBs 

Apocynaceae

Locality 24

Salix 

CTCC

Locality 30

Salix 

CTCC 

Liquidambar

Locality 36

Salix 

Goweria 

Pterocarya 

Alnus

other parts of the complete section. For example, the Fultonian stage is represented by less than 115 m in the Green 

River Gorge section, yet interpretation of the section and its 

subdivisions was not made in light of the environments of 

deposition represented.

The pattern of distribution of source plants can be compared by analogy to that along the Rio San Pedro in Tabasco, 

Mexico, where zones of streamside vegetation are flanked 

by more diverse levee and back-levee vegetation (Burnham, 

1989). Subenvironments of the modern floodplain have a 

strong influence on the species composition and thus on the 

litter that might be preserved in the fossil record. Plant-species composition is likely to have been somewhat patchy in 

the Puget Group floodplain; individuals of species probably 

were distributed in clumps or zones across a heterogeneous 

edaphic or topographic area. This type of distribution has 

been documented in temperate and tropical forests (Nixon 

and others, 1977; Hubbell, 1979; Hupp and Osterkamp, 

1985) and has been presumed to be due to patchy dispersal 

and disturbance.

The species composition along the river margins apparently was less rich than that in the area more distal to the

river channel (floodbasin and lacustrine cutoff). Physiognomically, the channel-margin assemblages have a lower 

entire-margin percentage than assemblages derived from 

other facies. Leaf-size index of floras from channel-margin 

facies is not different from that derived from assemblages of 

other facies, and the proportion of deciduous taxa is similar 

to that in the whole flora. Floristically, the channel-margin 

assemblages are dominated by taxa (Cercidiphyllum-Trochodendron Complex and Salix) that are allied either to 

modern forms more characteristic of streamsides than 

mature forests or to forms interpreted from fossil 

assemblages to be open-habitat woody species or colonizers 

(Mickey, 1977; Wing, 1981; Crane, 1984; Crane and 

Stockey, 1985; Crane and others, 1991). The channels may 

have acted as conduits along which species able to live in 

marginal, disturbed environments could be distributed. This 

continuity would effectively homogenize the channel-margin plant assemblages, producing a relatively high level of 

similarity. The presence of several channel-margin deposits 

in the middle of the stratigraphic section gives the false 

impression of a climatic or disturbance event. The principal 

controlling factor is the depositional environment, an effect
HETEROGENEITY IN THE PLANT-FOSSIL RECORD B19

that would not have been detected without the kind of analysis presented here.

In contrast, floodbasin deposits are the product of overbank flooding and distal crevasse-splay activity. Leaf litter 

accumulating in these low-lying back-levee areas was 

derived from a rich, but patchy, source vegetation. The 

floodbasin assemblages, on average, are very similar in 

physiognomic aspects to the whole flora from the Puget 

Group. This reflects the large proportion of the total flora 

that is present in floodbasin assemblages as a whole (73 of 

92), as well as the high species richness of most of the floodbasin assemblages. Floristically, the dominant taxa from 

floodbasin assemblages are Viburnum, Glyptostrobus, two 

leaf taxa that resemble leaflets of the Juglandaceae, and 

Dryophyllum, presumably a member of the Fagaceae. These 

taxa are related to modern taxa whose ecological distributions range from swamps, especially Glyptostrobus, to moderate uplands, especially Viburnum and members of the 

Fagaceae. Regional vegetation is represented best by several 

samples from this back-levee area.

The observed similarity among floodbasin assemblages 

can be attributed to the large and continuous area sampled by 

the floodbasin deposits, which effectively homogenizes the 

species-rich assemblages. Floodbasins are interpreted to represent an area in which species heterogeneity on a small 

scale may be substantial; however, over a large area, heterogeneity is reduced because of the recurrence of particular 

species at moderate to low abundances in many areas. Figure 

16 illustrates this concept. Note that source floras near cutoff 

meanders are unlike each other, whereas source floras for 

near-channel assemblages are very similar. Regional vegetation is best reconstructed from fossil floras using numerous 

samples from paleofloodbasins with representative samples 

(localities) from a variety of subenvironments, as shown in 

figure 16.

Lacustrine-cutoff floras are species rich, although, on 

average they are less species rich than floodbasin assemblages. The average percentage of entire margins is essentially the same for lacustrine-cutoff assemblages as for 

floodbasin floras but shows a wider range of variation 

among samples. Average leaf size of lacustrine-cutoff 

assemblages is the same as for floodbasin assemblages and 

the total flora, but again, is more variable than floodbasin 

assemblages. The notable feature in analysis of lacustrinecutoff assemblages is their lack of similarity to one another. 

They show low site-to-site similarity in terms of presence 

and absence of taxa, as well as abundance and dominance.

The lacustrine cutoffs probably were isolated on the 

floodplain. Their isolated distribution created barriers to 

the continuity of plant populations that colonized lacustrine-cutoff environments and produced the observed high 

site-to-site variation in plant litter. Source floras growing 

alongside different lacustrine cutoffs (and in the cutoff if 

infilling had progressed far enough) may have had different 

compositions, controlled by random colonization from the

CUTOFF MEANDERS

FLOODBASINS CHANNEL

Figure 16. Plan view of hypothetical fluvial-deltaic floristic heterogeneity. Each symbol represents one species and may include 

one to several individuals.

levee and back-levee area. Because of this high degree of 

variability, floristic or vegetational reconstructions based 

on lacustrine cutoff assemblages have the potential to be 

biased in unpredictable ways. A suite of lacustrine-cutoff 

assemblages does not provide a strong basis for prediction 

of the taxa or physiognomy of the vegetation likely to be 

present in another lacustrine-cutoff flora. If the source floras are homogeneous, this potential for bias is reduced.

Criteria that appear to be correlated with accurate 

reflection of regional flora are (1) high species richness 

relative to other localities from the same sequence but 

from apparently different depositional settings, and (2) 

consistency of characteristics from locality to locality 

within depositional environment (for example, richness, 

margin percentages, dominant taxa). Observation of these 

two criteria within samples drawn from a specific type of 

depositional environment probably indicates that regional 

vegetation can be reconstructed using several samples 

from the specified type of depositional environment 

(Burnham, 1993).
B20 EVOLUTION OF SEDIMENTARY BASINS SOUTHWEST WASHINGTON AND NORTHWEST OREGON

ANOMALOUS LOCALITIES AND THEIR USE 

IN INTERPRETING PALEOECOLOGY

physical sedimentary structures (Burnham 1990) do not provide adequate evidence for differentiation.

Certain plant localities are anomalous in the multivariate analyses. These localities are either extremes of a trend 

(localities 25 (floodbasin) and 17 (channel-margin)) or their 

scores are unusual relative to other samples. Localities 27 

and 33 are examples of assemblages that are truly different 

from all others. These two localities form a low-similarity, 

outlying cluster on the dendrogram (fig. 15) and form the 

extremes at the right on axis 1 of the Reciprocal Averaging 

and the Detrended Correspondence Analyses (fig. 14). They 

probably are outliers that deviate from the general trend and 

thus may be of special interest because of their unique position. Both samples are derived from lacustrine-cutoff facies 

and are from the lower-middle part of the section, 49 and 64 

m, respectively, above the base (table 1). Both assemblages 

are dominated by taxa such as Salvinia and Zingiberopsis 

and by two monocotyledonous taxa that rarely are present in 

other assemblages (appendix 1). These dominant taxa probably are indicative of quiet standing water and suggest 

growth during the lacustrine phase of infill of an abandoned 

cutoff. They are not particularly similar floristically (Sorenson's Index=21 percent), yet they are consistently grouped 

together. The presence of these two extreme outliers 

strengthens the impression that lacustrine cutoffs are isolated, vegetationally distinct islands on the floodplain.

As mentioned previously, locality 18, a channel-margin 

assemblage, also is anomalous with respect to the other 

channel-margin localities. It consistently groups with the 

floodbasin and lacustrine-cutoff assemblages (figs. 14, 15), 

even though it has a low number of taxa (n=13). All of the 

taxa recorded from this site are characteristic of floodbasin 

environments, and the sample does not contain Salix, which 

is present in many lacustrine-cutoff samples and all other 

channel-margin samples. Locality 18 was deposited in a 

coarsening-upward sequence of typical channel-margin sediments that overlies a thin, coaly shale. This locality is interpreted to represent deposition in a position distal to the 

channel, even though sedimentation rates were higher (as 

indicated by the presence of ripple-cross-laminated sandstone, isolated leaves, and so on) than in typical cutoff or 

floodbasin deposits. In the facies classification used for this 

analysis (Burnham, 1990), channel-margin facies include 

several types of subfacies that represent minor channels, 

levees, point bars, and proximal crevasse-splay channels. 

Locality 18 is interpreted to represent a deposit from the 

proximal part of a crevasse splay, deposited farther from the 

channel than most proximal parts of crevasse splays. During 

deposition, the crevasse channel extended onto the floodbasin and incorporated typical floodbasin taxa, thus the high 

floristic similarity. In this case, the use of the taxonomic 

composition of plant-bearing deposits provided a means to 

assess the unique characteristics of the deposit even though

CONCLUSIONS

Three types of plant assemblages are present in the 

plant-rich floodplain deposits of the Eocene Puget Group of 

Washington State: relatively homogeneous floodbasin floras 

having high species richness, heterogeneous floras of lacustrine-cutoff sites having moderate, but variable, species richness, and relatively homogeneous channel-margin floras 

having low species richness.

The regional flora is represented best by floodbasin 

localities, which collect taxa from the high-diversity levee 

and back-levee areas, as well as from the swamp floras. The 

conclusions drawn from modern leaf-litter censuses in the 

Rio San Pedro, Mexico (Burnham 1989), support the concept of floodbasin sites as the best indicators of regional 

flora. The correlation between abundance of individual species in litter samples and their abundance in the standing 

vegetation is not clear (but see Burnham and others, 1992). 

The results of the present study of the Puget Group indicate 

that abundance data has the potential to distinguish plants 

common in the immediate area of the sample from those at 

greater distances.

The lacustrine-cutoff environments are interpreted as 

isolated pockets on the floodplain that incorporate the plants 

immediately surrounding them. Because cutoff flow is sluggish and episodic, plant parts from outside the immediate 

area rarely are transported into these cutoff environments. 

Studies on modern lacustrine-cutoff leaf litter versus other 

floodplain litter would be useful in supporting the standing 

vegetation distribution proposed for the Puget Group.

Channel-margin deposits are low in species richness. 

These deposits represent environments in which periodic 

disturbance of plant communities takes place; such environments are the least conducive to preservation and have the 

highest potential for leaf destruction. The floristic assemblages of channel margins may be homogeneous because of 

the conduit nature of the river itself. Plant populations spread 

along the banks or by dispersal in the water and become reestablished downstream. The distribution of plants along the 

banks of the Rio San Pedro bear on these observations 

(Burnham, 1989). The flora is less species rich along the 

channel margins of the Rio San Pedro. The same 5-10 species are present as streamside dominants along most of the 

20 km of river studied. Litter samples from surface 

sediments in the channel-margin environments are less 

diverse than those collected on, and in back of, the levees. 

Plant assemblages from channel-margin environments can 

be biased both taxonomically and physiognomically due to 

the taxonomic composition and vegetation type likely to 

develop in these more open, disturbed environments.
HETEROGENEITY IN THE PLANT-FOSSIL RECORD B21

DEPOSITIONAL ENVIRONMENTSIMPLICATIONS FOR THEIR USE 

IN PALEOBOTANY

BIOSTRATIGRAPHY

Biostratigraphic zonation usually is based on series of 

vertically superposed samples taken from a reasonably continuous stratigraphic section. In the Puget Group, an analysis 

of this sort would require that the zonation be based on stratigraphically and ecologically similar samples. Species turnover from one stratigraphic level to the next can be due to 

large-scale heterogeneity, migration, or evolutionary 

change. Appearance and disappearance of taxa can be interpreted as biogeographic movement, climatic change, or evolutionary modification of taxa in situ. In a zonation based on 

plant biostratigraphy, the confounding effects of ecology 

and stratigraphy have the potential to inflate estimates of 

evolutionary or climatic change. Assemblages from lacustrine-cutoff deposits have erratic taxonomic changes from 

site to site, as demonstrated by the ordination and cluster 

analyses (figs. 14, 15), and are particularly subject to misinterpretation. Stratigraphic zonations of plant fossils should 

be based on sections in which the potential changes due to 

facies type can be evaluated. The floodbasin deposits of the 

Puget Group L-Bar quarry section are species rich, consistent with respect to physiognomic features, and floristically 

similar. These features indicate that they provide the best 

assemblages on which to base a biostratigraphic zonation, if 

a single environment type is to be used. The strong facies 

effects demonstrated by the several analyses presented here 

indicate that plant biostratigraphic zonations based on a single facies type will be more reliable than those for which 

facies restrictions cannot be demonstrated. Biostratigraphic 

zonations for which facies type is held constant provide a 

way to investigate the effects that spatial and temporal variability have had on plant-fossil data. At the minimum, biostratigraphic zonations based on plants must unequivocally 

demonstrate that the zone boundaries are based on temporal 

changes, not on environmental differences.

PALEOCLIMATOLOGY

The most accurate climatic reconstructions are made 

using a large number of taxa, as recommended by Wolfe 

(1971, 1981b), but the samples should be derived from 

nonchannel facies. The channel-margin assemblages of the 

Puget Group show an average of 10 percent fewer entire 

margins than floodbasin and lacustrine-cutoff assemblages. 

Use of these channel-margin samples alone potentially 

decreases the estimate of mean annual temperature by 3-4°C 

(Wolfe, 1979). Elimination of the five channel-margin 

assemblages from the 20 samples from the Puget Group

increases the average percentage of entire-margined taxa 

from 49.3 to 52 percent. It is recommmended that for paleoclimatic analysis of deposits similar to those of the Puget 

Group, demonstrable channel and channel-margin assemblages should be segregated and not counted for purposes of 

climatic reconstruction.

The lacustrine-cutoff assemblages, as a group, show no 

deviation in physiognomy from that of the total flora (figs. 

8-11). Individually, however, lacustrine-cutoff assemblages 

show marked deviations from the average for all localities. 

Care should be taken to ensure that cutoff floras do not show 

marked compositional variability from locality to locality. 

Variation of this sort would likely bias the climatic signal if 

it were to be inferred from any single cutoff deposit. As a 

group, these assemblages probably represent an adequate 

cross section of the vegetation with which to estimate paleoclimate.

PALEOECOLOGY

Paleoecological reconstructions probably are made 

most accurately using a range of different depositional environments. In the Eocene community investigated here, sharp 

ecological boundaries are not present between adjacent 

facies, and the resulting mix of plant taxa confounds a clear 

statement of taxon by environment specificity. Certain taxa, 

however, clearly show facies preference (for example, Salix 

in channel margins and Viburnum, Glyptostrobus, and 

"Acrodromous Entire" in floodbasins).

The obvious bias of channel-margin assemblages (figs. 

8A, 10A, 12), which represent only a specific kind of streamside vegetation, limits their use. Channel-margin deposits 

are species poor and floristically similar over large geographic distances. Although they are unreliable for climatic 

reconstructions, they add information regarding the ecological distribution of taxa. In the floodplain represented by the 

Puget Group, Cercidiphyllum-Trochodendron Complex 

were streamside associates, possibly present in the standing 

floras on the levee, but at low frequency. With specific reference to the ecological distribution of the CercidiphyllumTrochodendron Complex, this distribution was mentioned 

by Crane (1984), who studied similar taxa from the early 

Tertiary of Britain. Thus, the strongest contribution of channel-margin assemblages may be in clarifying the ecological 

tolerances of extinct taxa.

Lacustrine-cutoff deposits are likely to be species rich 

relative to channel-margin deposits but also include floristic 

components that indicate a standing-water wetland (for 

example, Salvinid). Depending on the regional species richness, lacustrine-cutoff assemblages may be variable from 

site to site (as documented in the Puget Group), or they may 

be pockets of vegetation that are similar to one another in a 

more species poor region. The value of lacustrine-cutoff
B22 EVOLUTION OF SEDIMENTARY BASINS SOUTHWEST WASHINGTON AND NORTHWEST OREGON

assemblages depends on knowledge of the spatial variability 

of the ecosystem being studied.

Floodbasin assemblages are, for the most part, species 

rich. These assemblages reflect regional and local vegetation 

most accurately of all the depositional environments investigated, both modern and ancient. Thus, they are reliable indicators of the forest type and physiognomy from which 

Cenozoic fossil assemblages were derived. To represent adequately spatial vegetation patterns, floodbasin assemblages 

are used most effectively by combining their vegetation 

information with that from other environments. Floodbasin 

facies are presumed to represent low-lying wetland areas 

and, less frequently, well-drained floodplain areas. Their floras are likely to be composed of regionally dominant, mature 

forest trees.

Each facies type contributes information on plants 

restricted to, or most abundant in, specific depositional environments. Autecology of individual taxa can be approached 

by recognition of the restriction of the taxon to a specific 

depositional environment. The longevity and stability of 

streamside communities versus floodbasin (or back-levee) 

communities can be compared through this kind of documentation of spatial community structure.

RECOMMENDATIONS FOR

CENOZOIC PALEOBOTANICAL

INVESTIGATIONS

The following recommendations are made for specific 

applications of Cenozoic plant-fossil data. Approaches to 

the plant-fossil record must vary to suit the goal of the 

research; for example, paleoecology, paleoclimatplogy, biogeography, or phylogenetic reconstruction. /

First, data on megafossil biostratigraphic zonations 

should be restricted, where possible, to deposits derived 

from similar depositional environments. In situations where 

the biostratigraphy must be constructed using different 

facies, care should be taken that the variation observed is 

evolutionary not ecological.

Second, certain types of facies preserve a biased sample 

of the standing vegetation. The observation of high variability in plant-species composition among lithologically similar, contemporaneous deposits is an indication that 

individual samples are biased. Such samples should be used 

only tentatively for paleoecological and paleoclimatological 

purposes.

Third, paleoclimatic reconstructions are best estimated 

from plant assemblages representing environments other 

than channel or channel margin.

Fourth, community paleoecology can be reconstructed 

most accurately using a wide range of paleoenvironments, 

including those environments that may be less favorable 

sites of plant-fossil preservation.

Finally, paleoecology of single species or clades is estimated most accurately by assessing paleoenvironment independently of plant composition.

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Manuscript approved for publication January 10, 1994 

Published in the Central Region, Denver, Colorado 

Edited by Judith Stoeser

Graphics and photocomposition by Shelly Fields 

Tables prepared by Judith Stoeser

APPENDIXES 1-4
Appendix 1. Matrix of abundance data for 20 plant-fossil localities from the Puget Group. 

[Abbreviations for taxa are given in appendix 4]

Taxa

Plre

Vipu

Hyps

Apoc

CdBs

Foth

Calk

AcEn

LREE

Meni

Dryo

Tern

CTCC

CrRi

LRNF

Pers

Pter

FBEE

Arto

Pulo

E2Br

Caca

Clad

Cocc

Liqu

Glyp

Plat

Rham

Alia

M23m

Chae

Maca

Equi

M45m

WPTA

Phac .

Plap

Ainu

Aspl

Vine

MuOE

Aldu

OvsJ

Zelk

Cast

Sail

04

21

59

36

10

7

5

15

24

11

90

3

15

18

8

9

6

7

8

22

3

21

0

4

97

0

52

4

3

8

6

0

10

5

0

0

0

0

0

0

0

0

0

0

0

0

0

18

2

0

5

19

38

0

8

0

4

0

88

0

161

0

0

0

2

0

3

0

0

9

0

0

0

0

0

5

0

0

0

0

0

0

0

17

0

0

0

0

0

0

0

0

0

0

19

0

8

94

0

11

0

0

11

8

0

9

0

0

0

0

0

3

0

37

3

13

143

4

0

0

17

0

0

0

2

6

3

0

0

0

0

47

42

13

2

0

0

0

0

0

0

21

0

7

229

0

5

3

2

2

4

0

105

0

0

0

0

0

97

0

71

7

14

114

12

0

0

82

0

9

6

0

2

2

0

0

0

0

5

26

0

0

3

6

12

3

0

0

22

0

0

3

0

0

0

0

7

0

0

0

0

68

0

3

0

3

8

2

0

25

0

5

0

0

0

0

0

0

0

5

0

0

0

0

0

167

0

0

31

0

0

0

7

0

31

23

10

0

0

0

0

0

0

0

0

0

0

0

13

0

2

2

20

4

0

0

0

0

10

0

0

0

0

0

10

75

0

10

0

81

0

10

0

0

0

0

0

0

0

0

0

348

24

0

0

0

6

0

0

0

0

4 r

0

3

0

32

3

0

0

4

0

0

0

0

2

6

0

0

0

2

5

0

0

2

0

0

0

0

0

0

0

0

0

0

0

0

0

0

95

25

0

0

22

0

0

0

0

2

0

0

17

0

0

0

0

0

16

0

0

0

0

31

2

0

0

20

0

0

0

3

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

Locality number 

26 27 07

0

30

12

3

12

7

0

16

0

0

0

0

6

0

0

4

0

0

3

26

0

7

13

0

0

0

0

0

2

76

5

4

0

41

0

0

0

2

0

0

0

5

0

0

0

0

0

0

0

0

0

10

0

0

0

0

0

0

2

0

0

4

0

0

0

0

0

15

3

0

274

0

0

0

0

0

0

0

0

0

0

0

0

58

0

0

0

0

0

0

0

0

0

55

14

0

0

5

3

6

0

0

18

0

151

0

0

0

0

0

3

138

0

37

8

0

8

0

0

43

5

9

99

19

0

4

58

18

0

70

0

2

0

0

0

0

2

0

29

0

44

0

2

0

0

0

17

0

0

110

0

0

0

0

0

15

3

14

168

0

0

3

0

0

0

0

32

0

0

0

8

0

0

0

0

0

19

0

0

0

0

0

0

0

0

30

10

0

0

0

0

2

4

0

0

0

0

0

278

7

0

0

0

0

0

0

0

0

0

0

30

0

0

0

0

4

0

0

0

0

0

4

0

0

0

0

0

0

0

0

0

112

31

0

23

25

2

0

0

0

0

6

0

144

0

9

7

0

0

0

35

2

4

0

21

9

0

4

2

0

0

15

4

0

0

2

14

0

14

0

5

0

0

0

0

0

0

4

13

32

0

13

19

0

0

0

0

2

0

0

4

0

214

0

0

0

8

0

0

84

0

5

0

0

3

0

0

0

0

0

0

0

0

0

0

12

0

0

0

0

0

0

0

0

6

0

33

0

0

2

5

0

0

0

0

3

0

0

0

0

0

0

6

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

3

0

24

0

0

0

0

0

0

0

0

0

0

0

0
Appendix 1. Matrix of abundance data for 20 plant-fossil localities from the Puget Group Continued.

Taxa

Acne

Hama

Gowe

FCBN

JuHi

Frax

Cyin

TLWP

Meta

Denn

Rhus

Zing

Betu

PeBf

SCA2

Smse

ATRP

Popu

AcEu

Burs

CESB

CCMT

FeMo

ACH

DDCA

NFMe

CTBR

3LMo

C2R3

LTau

Salv

Anam

Sapl

flex

Viti

EmAe

E1B2

CrSp

Lila

Dryp

FiEu

Mace

Meme

Tile

BrdM

3FHy

Anac

04

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

o

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

18

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

19

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

21

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

22

110

3

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

23

0

0

5

12

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

24

0

0

2

0

3

3

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

25

0

0

0

0

0

0

173

0

40

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

Locality number 

26 27 07

0

0

0

20

0

0

0

26

0

111

4

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

73

34

0

2

10

3

3

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

6

13

28

0

0

0

8

0

0

0

49

22

0

0

0

0

0

25

46

20

3

14

16

4

3

3

7

0

5

15

6

3

3

6

0

0

0

0

0

0

0

0

0

0

0

0

29

0

0

9

0

0

0

0

0

0

0

0

0

3

0

0

0

0

0

10

27

0

0

0

7

0

0

0

0

0

0

0

0

0

0

0

8

8

0

0

0

0

0

0

0

0

0

0

30

0

3

0

0

0

0

0

0

0

0

0

0

0

20

0

0

0

0

0

0

0

0

0

0

0

0

0

0

6

0

0

0

0

0

0

0

0

5

4

1

0

0

0

0

0

0

0

31

19

0

21

0

0

0

2

0

0

0

0

0

0

0

2

0

0

0

2

12

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

40

0

5

4

29

7

0

0

0

32

0

0

0

0

0

0

0

11

0

0

0

0

3

0

0

0

0

0

0

3

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

9

0

0

0

10

0

0

0

0

33

0

0

0

0

0

0

0

0

0

0

0

294

5

0

0

0

0

0

0

0

0

0

0

0

0

0

0

32

0

0

28

0

0

0

0

0

0

0

0

4

0

0

0

0

84

0

0
Appendix 2. Matrix of Sorenson's Index of Similarity for comparisons between 20 plant-fossil localities from the Puget Group. 

[Localities are shown in stratigraphic sequence]

34 21 19 18 22 17 07 32 29 36 30 27 24 33 31 26 

34

21

19

18

22

17

07

32

29

36

30

27

24

33

31

26

25

35

23

04

*

0.33

0.33

0.34

0.11

0.08

0.44

0.32

0.42

0.26

0.17

0.17

0.38

0.22

0.42

0.31

0.25

0.52

0.27

0.37

*

0.74

0.46

0.43

0.00

0.29

0.33

0.43

0.28

0.10

0.20

0.24

0.15

0.36

0.57

0.39

0.48

0.20

0.58

*

0.42

0.50

0.00

0.38

0.39

0.44

0.27

0.06

0.18

0.34

0.17

0.40

0.56

0.53

0.46

0.23

0.53

0.28 *

0.25 0.21 *

0.26 0.33 0.08 *

0.41 0.25 0.21 0.53 *

0.29 0.27 0.00 0.52 0.38 *

0.20 0.36 0.20 0.20 0.24 0.32 *

0.30 0.20 0.35 0.30 0.27 0.00 0.19 *

0.15 0.13 0.12 0.34 0.27 0.17 0.32 0.21 *

0.50 0.32 0.22 0.29 0.26 0.33 0.38 0.21 0.21 *

0.21 0.06 0.00 0.25 0.13 0.17 0.13 0.00 0.21 0.13 *

0.33 0.27 0.16 0.53 0.27 0.39 0.31 0.29 0.24 0.36 0.12 *

0.33 0.31 0.08 0.61 0.36 0.36 0.40 0.16 0.32 0.26 0.21 0.41 *

0.35 0.31 0.00 0.28 0.38 0.26 0.15 0.08 0.17 0.32 0.08 0.31 0.30 

0.29 0.27 0.00 0.43 0.41 0.45 0.31 0.19 0.14 0.37 0.19 0.32 0.31 

0.29 0.39 0.33 0.42 0.19 0.28 0.38 0.34 0.21 0.33 0.13 0.36 0.41 

0.48 0.37 0.06 0.35 0.29 0.41 0.24 0.25 0.17 0.38 0.21 0.44 0.50 

Appendix 3. Matrix of Spearman's Rank-Order Correlation Coefficients for 20 plant-fossil localities from the Puget Group.

[Values are all calculated from data matrix for which absolute abundances are greater than 2 for all taxa. Localities are shown in stratigraphic sequence]

34

21

19

18

22

17

07

32

29

36

30

27

24

33

31

26

25

35

23

04

34

*

0.15

0.18

0.22

-0.08

0.05

0.19

0.16

0.25

0.13

0.01

-0.03

0.27

0.11

0.20

0.13

0.13

0.43

0.08

0.14

21

*

0.73

0.42

0.29

-0.11

0.20

0.22

0.35

0.16

-0.16

0.06

0.22

-0.04

0.19

0.40

0.40

0.34

0.01

0.45

19

*

0.33

0.37

-0.09

0.22

0.25

0.33

0.14

-0.17

0.04

0.18

0.01

0.23

0.42

0.48

0.29

0.03

0.42

18

*

0.12

0.30

0.16

0.34

0.19

0.10

0.18

0.02

0.44

0.10

0.25

0.19

0.26

0.20

0.17

0.44

22

*

0.27

0.00

0.10

0.09

0.30

0.06

-0.02

0.21

-0.10

0.12

0.12

0.17

0.10

0.27

0.24

17

*

0.13

0.27

0.-9

0.29

0.45

0.08

0.30

-0.07

0.27

0.03

-0.06

0.10

0.45

0.02

07

*

0.38

0.38

0.16

-0.01

0.20

0.07

0.11

0.18

0.36

0.09

0.17

0.14

-0.01

32

*

0.29

0.15

0.13

0.14

0.12

-0.01

0.46

0.26

0.28

0.27

0.06

0.14

29

*

0.24

-0.21

0.02

0.22

0.01

0.25

0.20

0.16

0.39

0.11

0.25

36

*

0.11

0.28

0.42

0.00

0.21

0.26

0.05

0.24

0.33

0.08

30

*

0.09

0.10

-0.09

0.13

-0.03

-0.06

0.08

0.25

0.08

27

*

0.07

0.15

0.08

0.17

0.06

-0.05

0.05

-0.05

24

*

0.01

0.26

0.08

0.22

0.28

0.25

0.21

33

*

-0.02

0.13

-0.04

0.02

0.09

0.07

31 26 

*

0.21 *

0.26 0.22 

0.15 0.16 

0.28 0.31 

0.19 0.33 
HETEROGENEITY IN THE PLANT-FOSSIL RECORD B31 

Appendix 4. Abbreviations and taxonomic citations for plant-fossil taxa from the 20 localities examined in the Puget Group.

The four-letter abbreviation for taxa in appendix 1 is given in italics at the left of each citation. Taxa are either (1) referred to 

previously described taxa to which the Puget Group specimens are most similar, citing references to original descriptions or to recent 

emendations of the original descriptions, or (2) briefly described in the case of taxa not previously described and named informally 

(using quotations marks) with morphotype designations. Descriptive terminology is drawn from Hickey (1973). Descriptions of the 

morphotypes presented here are not intended to serve as formal systematic descriptions of taxa nor are the informal names intended to 

serve as formal nomenclature. Until further work can be completed on the taxonomic affinities of the taxa described informally, the 

descriptions and names are intended simply to assist in identifying taxa found in plant-bearing deposits from the Puget Group. 

Examples of taxa identified only as morphotypes are listed by specimen number. All specimens listed are curated at the National 

Musuem of Natural History, Smithsonian Institution, Washington, D.C. Arrangement of taxa is in the same order as in the data matrix 

presented in appendix 1: Equisetum first, followed by Pteridophytes, Coniferophytes, monocotyledonous Angiosperms, and 

dicotyledonous Angiosperms.

Equi Equisetum sp. cf. E. newberryi Knowlton and Cockerell. Knowlton (1919) or E. sp. of Wing (Wing, 1981).

Aspl Asplenium sp. cf. A. delicata (Brown) MacGinitie. MacGinitie (1969).

Dryp Dryopteris sp. cf. D. whatcomensis Pabst. Pabst (1968).

Alia Allantodiopsis sp. cf. A. pugetensis Wolfe. Wolfe (1968).

Cyin Cyathea sp. cf. C. inequilateralis (Hollick) Wolfe. Wolfe (1977).

Derm Dennstaedtia sp. cf. D. delicata Pabst. Pabst (1968).

Salv Salvinia sp. cf. S. preauriculata Berry. Berry (1925), similar to that described in Hickey (1977) and Wing (1981).

Meta Metasequoia sp. cf. M. glyptostroboides Hu and Cheng or M. occidentalis (Newberry) Chancy. Chaney (1951) and Wolfe 

(1968).

Glyp Glyptostrobus sp. Wolfe (1968).

BrdM "Broadly cross-veined monocotyledon." Monocotyledonous foliage fragments, as much as 6 cm in length and 2-3 cm wide. 

Primary and secondary veins paralleodromous, spaced approximately 1 cm apart and similar in size, such that differentiation 

between them is difficult to detect. Cross veins widely spaced, about every 2-4 mm along the length of the foliage fragments.

M23m "Monocotyledon having 2-3 veins per millimeter." Monocotyledonous foliage fragments, > 15 cm long, 1-3 cm wide; 

parallelodromous veins closely spaced, of essentially equal size. Vein density from 2 to 4 per millimeter on the same 

fragment. Texture coriaceous. These fragments bear similarity to segments of dissected palm leaves.

Zing Zingiberopsis sp. cf. Z. isonervosa Hickey. Hickey (1977) and Hickey and Peterson (1978).

TLWP "Thread-like water plant." Leaves(?) 1 mm wide or less, more than 2 cm long, attached to only slightly wider stems. Leaves 

form thin mats as much as 10 cm in width on bedding planes.

3LMo "Three-level monocotyledon." Broad-bladed monocotyledonous leaf similar to general form of Zingiberopsis. Maximum

size unknown, fragments as much as 9 cm in width, as much as 10 cm in length. Neither measurement believed to be close to 

the size of a whole leaf. Three vein orders: coarsest veins spaced 2-4 mm apart, second-order veins evenly spaced at 1 mm, 

third-order veins evenly divide the area between the second-order veins into four areas. Thus, the leaf fragments have five 

veins per millimeter, consisting of three vein size orders.

M45m "Monocotyledon having 4-5 veins per millimeter." Broad-bladed monocotyledonous foliage, similar to Zingiberopsis, but 

having blade segments commonly much narrower than those present in Zingiberopsis. Blade segments commonly 10-17 cm 

wide (believed to be very close to typical total width) but occasionally as narrow as 2 cm wide. Central broad midrib present, 

as much as 8 mm wide. One subsidiary vein order present, density 4-5 per mm, diverging from midvein at very low angles
B32 EVOLUTION OF SEDIMENTARY BASINS SOUTHWEST WASHINGTON AND NORTHWEST OREGON

FeMo "Featureless monocot." Heavily cutinized leaves(?), as much as 12 cm in width, 5-30 mm long, (obviously only a part of the 

total length). Largest specimens have a thin, longitudinal vein centrally, but in the similar, smaller specimens this vein is not 

visible. Faint transverse ridges are present sporadically along axes, spaced at distances greater than 1 cm, possibly 

representing nodes; however, no axillary appendages are seen emerging at this point. Fragments bear resemblance to the 

largest axes of WPTA but are much larger. Their lack of distinctive features precludes even a definitive statement that they 

certainly represent monocotyledonous angiosperms.

Plre Plafkeria sp. cf. P. rentonensis (Wolfe) Wolfe; Wolfe (1977).

Vipu Viburnum sp. cf. V. pugetensis Wolfe. Wolfe (1968).

Hyps Hypserpa sp. cf. H. cashmanensis Wolfe. Wolfe (1968).

Apoc "Apocynaceous leaf." Simple, dicotyledonous leaf, 10-15 cm long, 4 5 cm wide; margin entire; base cuneate, forming 45°

angle; apex acute. Secondary veins eucamptodromous, divergence angle 70°-85°, forming an almost perpendicular secondary 

network. Intersecondary veins common, between almost every pair of secondary veins and extending to three-fourths the 

distance to the margin before bifurcating and joining supra- and sub-jacent secondary veins. Finer venation rarely preserved, 

apparently forming orthogonal-reticulate pattern.

CdBs "Cordate base, even alternate secondaries." Simple, dicotyledonous leaf, 8-15 cm long, 4-8 cm wide; margin entire; base 

cordate; apex acute having short (0.5 cm) drip tip. Secondary veins eucamptodromous to acrodromous near apex, evenly 

spaced, divergence angle 45°, commonly bifurcating near margin. Intersecondary veins rare and thin, losing identity by onequarter the distance to the margin. Tertiary, veins thin, oblique to primary veins, forming random-reticulate pattern.

Foth Fothergilla sp. cf. F. durhamensis Wolfe. Wolfe (1968). 

Calk Calkinsia sp. cf. C. plafkeri Wolfe. Wolfe (1977).

AcEn "Acrodromous entire." Simple, dicotyledonous leaf, 10-12 cm long, 2.5-3.5 cm wide; margin entire; base cuneate, forming 

45°-90° angle; apex acuminate having 1.0 cm drip tip. Secondary veins eucamptodromous, divergence angle 30°. 

Intersecondary veins absent. Tertiary veins oblique to midrib, forming orthogonal-reticulate pattern. Finest veins intruding 

areoles, branching once.

LREE "Low-rank entire elliptic." Simple, dicotyledonous leaf, 8-12 cm long, 4 5 cm wide; margin entire; base cuneate, forming

40°-60° angle; apex rounded to acute. Secondary veins eucamptodromous, bifurcating two to three times at three-fourths the 

distance to margin. Intersecondary veins absent. Tertiary veins orthogonal to primary vein, sinuous, forming widely spaced 

reticulum.

Meni Menispermites sp. cf. M. parvareolatus Hickey. Hickey (1977).

Dryo Dryophyllum sp. cf. D. pugetensis Wolfe. Wolfe (1968).

Tern Ternstroemites sp. cf. T. ravenensis Wolfe. Wolfe (1968).

CTCC "Cercidiphyllum-Trochodendron Complex." Simple, dicotyledonous leaf, 7-15 cm long, 4-7 cm wide; margin non-entire; 

base cordate to rounded; apex acuminate to acute. Teeth having convex basal margin and concave apical margin (C-l type). 

Secondary veins actinodromous, two to four (usually three) pairs originating at base of the lamina: central pair strongest, 

extending to apex and curving toward midvein, external pair(s) ending in teeth two-thirds the distance to apex. In some 

leaves the point of origin of the central pair of secondary veins is suprabasal. Tertiary veins forming weak loops at margin 

and bifurcating near teeth, the branch entering the tooth. This complex has a wide range of morphologies included, among all 

of which gradations can be found. The resolution of the limits to this taxon (these taxa?) will be aided by reference to the 

Puget Group specimens.

CrRi "Crenate cf. Rinorea." Simple, dicotyledonous leaf, 7-13 cm long, 2.5-5.0 cm wide; margin non-entire; base rounded to 

acute; apex not fully preserved, apparently at least short acuminate. Teeth having basal and apical margins convex (A-l 

type), rounded. Secondary veins eucamptodromous, bifurcating three-fourths of the distance to margin, both branches 

branching again. Intersecondary veins common, often more than one between adjacent secondary veins. Tertiary and finer 

veins are not easily distinguishable, forming a very fine orthogonal reticulate pattern. Resembles the leaves of the modern 

genus Rinorea (Violaceae).
HETEROGENEITY IN THE PLANT-FOSSIL RECORD B33

LRNF "Low-rank narrow with fimbrial." Simple, dicotyledonous leaf, as much as 7 cm in length, 3-4 cm wide; margin entire; base 

only partially preserved: probably cuneate; apex narrowing, blunt, not acuminate. Secondary veins brochidodromous, 

divergence angle 75°-85°, arching just inside margin, looping apically to fuse with suprajacent secondary vein. 

Intersecondary veins common, one or two between adjacent secondary veins. Tertiary veins oblique to primary vein, forming 

a random-reticulate pattern. This morphotype is similar to Apoc but the secondary veins fuse at the margin to form a 

prominent fimbrial vein, which is not pronounced in Apoc.

Pers Persea sp. cf. P. pseudocarolinensis Lesquereux. As described in MacGinitie (1941). 

Pier Pterocarya sp. cf. P. pugetensis Wolfe. Wolfe (1968).

FBEE "Festooned brochidodromous entire elongate." Simple, dicotyledonous leaf, 10-20 cm long, 4-10 cm wide; margin entire; 

base rounded; apex rounded. Secondary veins brochidodromous, looping apically to merge with suprajacent secondary, 

divergence angle 45°. Subsidiary loops formed by tertiary veins outside the secondary loops create festooned 

brochidodromous appearance. Intersecondary veins common, two or three between adjacent secondaries. Tertiary veins 

oblique to primary, unbranched. Quaternary and high-order venation forming quadrangular-reticulate pattern.

Arto "Artocarpoides"=Dicotylophyllum kummerensis Wolfe. Wolfe (1977). 

Pulo Pugetia sp. cf. P. longifolia Wolfe. Wolfe (1968).

E2Br "Entire, twice-brochidodromous, square intercostals." Simple, dicotyledonous leaf, 6-8 cm long, 3-5 cm wide; margin entire; 

base rounded; apex acute. Secondary veins brochidodromous, branching and looping upward at about three-fourths the 

distance to margin to merge with suprajacent secondary vein. Branches of secondary veins looping outside the secondary 

veins to form festooned brochidodromous appearance. Intersecondary veins uncommon, perpendicular to primary vein. 

Tertiary veins very faint, even in clay matrix, oblique to primary veins, forming square intercostal areas.

Caca Carya sp. cf. C. cashmanensis Wolfe. Wolfe (1968).

Clad Cladrastis sp. cf. C. pugetensis Wolfe. Wolfe (1968).

Cocc "Cocculus" sp. cf. "C. "flabella Wolfe. Hickey (1977).

Liqu Liquidambar sp. cf. L. californica Lesq. MacGinitie (1941), Wolfe (1968).

Plat "Platanaceae" cf. Macginitea angustiloba (Lesq) Manchester. Manchester (1986).

Rham "Rhamnites" cf. Dipterocarpaceae after "Rhamnites" cashmanensis of Wolfe (1968, 1977).

Chae Chaetoptelea morphotype A Burnham. Burnham (1986).

Maca Macaranga sp. cf. M. pugetensis Wolfe. Wolfe (1968)

WPTA "Water plant thick axis (cf. Myriophyllum)." Stems 0.3-4.0 mm wide, in fragments as much as 10 cm in length. Leaves (?) 

approximately 0.1 mm wide, as much as 2 cm in length, having a single midvein, apparently borne in a dense spiral 

arrangement on the stem axis. Multiple branching hierarchies present, having finer branches borne similarly to the leaves, in 

a dense spiral. Possibly a dicotyledonous angiosperm similar to the modern genus Myriophyllum, but the lack of attachment 

of the ultimate segments (leaves?) to each other does not support a dicotyledonous affinity.

Phac Phytocrene sp. cf. P. acutissima Wolfe. Wolfe (1977).

Plap Platycarya sp. cf. P. pseudobrauni (Hollick) Wolfe. Wolfe (1977).

Ainu Alnus sp. cf. A. operia MacGinitie. MacGinitie (1941)

Vine "Vinea"sp. cf. "Vinea"pugetensis Wolfe. Wolfe (1968,1977).

MuOE "Mucronate Oval Entire." Simple, dicotyledonous leaf, 4-5 cm long, 1-2 cm wide; margin entire; base cordate to rounded; 

apex retuse-rounded to mucronate. Leaves very carbonaceous, secondary and higher order veins poorly preserved: obviously 

sunk beneath the thick cuticle. Secondary veins eucamptodromous, divergence angle 45°. Higher order venation too poorly 

preserved to characterize.
B34 EVOLUTION OF SEDIMENTARY BASINS SOUTHWEST WASHINGTON AND NORTHWEST OREGON 

Aldu Allophylussp.cf.A.duktothensisWolfe. Wolfe(1977).

OvsJ "Oval, sparsely-veined Juglandaceae." Compound(?) dicotyledonous leaf, presumed leaflets 3.5-5.0 cm long, 1.7-2.5 cm

wide; margin non-entire; base rounded; apex acuminate. Teeth are merely sharp protuberances occurring irregularly along the 

margin, frequently coinciding with a secondary vein ending. Secondary veins craspedodromous, widely spaced, divergence 

angle 45°, looping smoothly apically. Intersecondary veins uncommon. Tertiary veins rarely well preserved, forming a fine 

reticulate pattern where preserved. Lamina asymmetric, particularly basally.

Zelk Zelkova morphotype C Burnham. Burnham (1986).

Cast Castanopsis sp. cf. C.franklinensis Wolfe. Wolfe(1968).

Sail Salix sp. cf. S. heartensis Hickey. Hickey (1977).

Acne Acer sp. cf. A. negundo-type. Similar to Acer eonegundo Wolfe et Tanai. Wolfe and Tanai (1987).

Hama Hamamelites sp. cf. H. voyana (Lesq) MacGinitie. MacGinitie(1941).

Gowe Goweria sp. cf. G. dilleri (Knowlton) Wolfe. Wolfe (1968,1977).

FCBN "Finely crenate margins, brochidodromous secondaries, wide lamina." Simple, dicotyledonous leaf, 4-7 cm long, 2.0-3.5 cm 

wide; margin non-entire; base cuneate; apex acuminate. Teeth small, basal margin convex, apical margin concave (C-1 type), 

secondary branch extending into apex of tooth. Secondary veins brochidodromous, looping and branching just inside the 

margin, one branch extending to a tooth, the other branch merging with the suprajacent secondary. Tertiary veins oblique to 

primary vein, branching halfway between secondary veins. Finer veins forming orthogonal-reticulate pattern.

JuHi "Juglandaceae" cf. Carya pugetensis Wolfe. Wolfe (1968).

Frax Fraxinus sp. cf. F. yubaensis MacGinitie. MacGinitie (1941).

Rhus Rhus sp. cf. R. typhina Torner (modern).

Betu Betula sp. cf. B. papyrifera Marsh, (modern).

PeBf "Perpendicular secondaries, brochidodromous, fimbrial vein." Simple, dicotyledonous leaf, 7-9 cm long, 1.0-3.0 cm wide; 

margin entire; base cuneate; apex acute. Secondary veins brochidodromous, divergence angle 65°-80°, meeting just inside 

the margin, forming a prominent fimbrial vein. Tertiary veins sinuous, turning toward margin after diverging from secondary 

vein, finally becoming perpendicular to primary vein. Finer veins form disorganized-reticulate pattern.

SCA2 "Semi-craspedodromous, arching secondaries, elliptic shape." Simple, dicotyledonous leaf, 3.5-7.0 cm long, 1.5-3.0 cm

wide; margin non-entire; base cuneate, forming 60° angle; apex not preserved. Teeth having convex apical and basal margins 

(A-l type), blunt. Secondary veins semicraspedodromous, apical branches looping up to meet suprajacent secondary, basal 

branch entering tooth. Tertiary veins subperpendicular to midvein. Finer venation forming clear quadrangular and 

pentagonal areoles.

Smse "Small, craspedodromous secondaries, elliptic." Simple (?) dicotyledonous leaf, 1.5-3.0 cm long, 1.1-1.5 cm wide; margin 

non-entire, base acute, apex acute. Teeth having convex basal and concave apical margins (C-1 type), having dark round 

gland at tip. Secondary veins craspedodromous, straight, ending in a tooth. Intersecondary veins absent. Tertiary veins 

oblique to secondary veins, branching before crossing between secondary veins. High-order venation mostly indistinct, 

apparently a random reticulate pattern.

ATRP "Apiculate teeth, reflexed secondaries, percurrent tertiaries." Simple, dicotyledonous leaf, 7-8 cm long; 3.2-4.0 cm wide;

margin non-entire; base rounded-acute; apex acute. Teeth having straight apical margin and convex basal margin (B-l type), 

intruded below the center by a secondary or tertiary vein. Tertiary veins straight or branching as they cross the secondarysecondary intercostal. Finer veins poorly preserved, apparently forming a random-reticulate pattern.

Popu Populus sp. cf. P. tremuloides Michaux (modern). Simple, dicotyledonous leaf, more than 5 cm long, 5 cm wide; margin 

non-entire; base broadly rounded; apex not preserved. Teeth convex on basal and apical margins (A-l type), rounded, 

without gland. Secondary veins actinodromous, three pairs arising at the base of the lamina, ending in teeth approximately 

one-third to two-thirds the distance to apex. Tertiary veins perpendicular to primary vein near the primary veins and oblique 

to the primary vein close to the margin. Finer venation forming a random-reticulate pattern.
HETEROGENEITY IN THE PLANT-FOSSIL RECORD B35

AcEu "Acalyphoid euphorb." Simple, dicotyledonous leaf, 8-12 cm long, 5-7 cm wide; margin non-entire; base shallowly cordate; 

apex acute. Teeth having convex basal and apical margins (A-l type), prominent secondary vein-ending protruding from 

tooth. Secondary veins craspedodromous, evenly spaced, opposite, branching at margin rare. Basal secondary branches 

common from basal pair of secondary veins. Tertiary veins commonly oblique to midrib and unbranched.

Burs Bursera sp. similar to the modern genus Bursera. Pinnately compound, dicotyledonous leaf, leaflets 3.5-4.0 cm long, 1.5 cm 

wide; margin entire; base rounded; apex mucronate to rounded. Secondary veins eucamptodromous, divergence angle 45°, 

branching one or two times near margin. Tertiary veins oblique to midrib, branched.

CESB "Craspedodromous elongate shallow base." Simple, dicotyledonous leaf, 12-15 cm long, 6-7 cm wide; margin non-entire; 

base shallowly cordate to rounded; apex acuminate, 1-2 cm drip tip. Teeth having concave basal and apical margins (C-3 

type), flat. Secondary veins craspedodromous, opposite, entering teeth medially, divergence angle 30°-45° (greater apically). 

Tertiary veins oblique to midrib, branching or slightly sinuous between secondary veins. Texture chartaceous.

CCMT "Cordate craspedodromous multiple teeth." Simple, dicotyledonous leaf, 5 cm long, 3 cm wide; margin non-entire; base 

cordate; apex acute. Teeth small, several per secondary, having convex basal and apical margins (A-l type). Secondary 

veins craspedodromous, branching one or two times near margin, each branch going to a tooth. Tertiary veins oblique to 

midrib, sinuous and unbranched. Finer veins form orthogonal-reticulate pattern.

ACII "Acalyphoid Euphorb Type II." Simple, dicotyledonous leaf, 15 cm long, 7.5 cm wide; margin entire; base cordate; apex not 

fully preserved, but at least short acuminate. Secondary veins actinodromous to acrodromous, three pairs of secondary veins 

arising at the base of lamina. Centralmost pair of secondary veins converges on margin approximately half the distance to the 

apex, second pair of secondary veins converges on margin in basal one-quarter of the lamina, basalmost pair of secondary 

veins follow margin, fusing with secondary branches of suprajacent secondary. Suprabasal secondary veins widely spaced, 

divergence angle 35°-45°. Tertiary veins percurrent, sinuous, oblique to primary vein, closely spaced. Texture chartaceous.

DDCA "Densely disorganized conical apex." Simple, dicotyledonous leaf, margin entire, more than 9 cm long, 5 cm wide; base not 

preserved; apex acute. Secondary veins brochidodromous, branching near margin, the branches fusing with supra- and 

subjacent secondary veins. Intersecondary veins present, two or three between adjacent secondary veins. Tertiary and 

higherorder veins disorganized, having veins forking and changing direction frequently. Ultimate areoles very small, intruded 

by unbranched veinlet.

NFMe "Narrow lamina fine mesh." Simple, dicotyledonous leaf, 9-10 cm long, 4-5 cm wide; margin entire; base rounded; apex 

short acuminate. Secondary veins eucamptodromous, rarely fusing with other secondary veins. Tertiary veins 

indistinguishable from finer veins. All finer veins forming an orthogonal-reticulate pattern.

CTBR "Cercidiphyllum-\\\x, teeth, Festooned Brochidodromous." Simple, dicotyledonous leaf, 9-10 cm long, 4-5 cm wide; margin 

non-entire; base rounded; apex short acuminate. Teeth having convex basal margin and concave apical margin (C-l type), 

and a tertiary vein extending to sinus, not to tooth. Secondary veins brochidodromous, arching upward to fuse with 

suprajacent secondary vein. Tertiary branches forming external loops on secondary veins and between secondaries; 

intercostal tertiary veins sinuous, widely spaced. Finer veins forming random-reticulate pattern.

C2R3 "Secondary veins craspedodromous, tertiary veins reticulate." Pinnately-compound, dicotyledonous leaf, leaflets 9-10 cm 

long, 2.7-3.0 cm wide; margin entire; base cuneate and asymmetric; apex short acuminate. Teeth having concave apical and 

basal margins (C-3 type), intruded by a secondary vein. Secondary veins craspedodromous, divergence angle 55°-60°, 

ending in the prominent teeth. Intersecondary veins common, two to four between adjacent secondary veins. Tertiary veins 

thin, only slightly thicker than finer veins, crossing between secondary veins without branching. Finer veins forming 

orthogonal-reticulate pattern.

LTau "Linear cf. Tauche' or Manilkara." Simple, dicotyledonous leaf, 10-11 cm long, 3-4 cm wide; margin entire; base rounded 

acute; apex acute. Secondary veins eucamptodromous, divergence angle 70°-80°, smoothly looping upward and decreasing 

in size. Intersecondary veins absent. Tertiary veins branching irregularly in crossing between secondaries. Finer venation 

poorly preserved, probably forming a random-reticulate pattern. Resembles the modern genus Manilkara (Sapotaceae).

Anam Anamirta sp. cf. A. milleri Wolfe. Wolfe (1977).

Sapl "Sapindaceous-Anacardiaceous leaflet." Similar to Melanorrhoea alaskana (Hollick) Wolfe. Wolfe (1977).
B36 EVOLUTION OF SEDIMENTARY BASINS SOUTHWEST WASHINGTON AND NORTHWEST OREGON

Ilex Ilex sp. cf. /. opaca Ait. (modern). Simple, dicotyledonous leaf, 6-8 cm long, 3.5-5.0 cm wide; margin non-entire; base

rounded and asymmetric; apex acute. Teeth having concave apical and basal margins (C-3 type), intruded by tertiary vein, 

spinose. Secondary veins semicraspedodromous to brochidodromous, divergence angle 45°, forking two or three times before 

reaching margin, having only one small branch reaching tooth. Tertiary veins sinuous, crossing between secondary veins 

without branching. Finer veins forming random-reticulate pattern.

Viti Vitis sp. cf. Vitis sp. of Wolfe (1977).

EmAe "Emarginate apex, entire margin." Simple(?), dicotyledonous leaf, 6-9 cm long, 2-2.5 cm wide; margin entire; base rounded; 

apex emarginate. Secondary veins eucamptodromous, divergence angle 75°-85°, turning toward apex only slightly at margin. 

Intersecondary veins present, one or two between adjacent secondary veins. Tertiary veins very thin, sinuous, only faintly 

visible between secondary veins. Basal venation slightly asymmetric, indicating that these could be leaflets; however, they 

also possess short (3 mm) petioles, relatively uncommon for leaflets.

EIB2 "Elliptic shape, brochidodromous intersecondary veins." Simple(?), dicotyledonous leaf, 6-9 cm long, 2-2.5 cm wide;

margin entire; base rounded; apex emarginate. Secondary veins brochidodromous, arching apically to fuse with superjacent 

secondary vein. Intersecondary veins common, two or three between adjacent secondary veins. Tertiary veins forming loops 

on margin side of secondary loops, creating festooned brochidodromous appearance. Intercostal tertiary veins branching two 

or three times between secondary veins, forming random-reticulate pattern.

CrSp "Craspedodromous Spined Margin." Simple, dicotyledonous leaf, 7-8 cm long, 2.2-3.0 cm wide; margin non-entire; base 

rounded-acute; apex not preserved, apparently short acuminate. Teeth abundant, very small, having straight apical margin 

and convex basal margin (B-l type), rarely having a small oblong gland at tip. Secondary veins brochidodromous, looping 

apically to fuse with suprajacent secondary vein. Intersecondary veins absent. Tertiary veins forming loops on the marginside of secondary loops. Intercostal tertiary veins oblique to primary vein and straight.

Lila "Entire campylodromous lauraceous." Simple, dicotyledonous leaf, 9-12 cm long, 2.5-5.0 cm wide; margin entire; base

cuneate; apex not entirely preserved, probably long acuminate. Secondary veins eucamptodromous, smoothly arching toward 

margin, evenly spaced. Intersecondary veins uncommon to absent. Tertiary veins perpendicular to primary vein, 

uncommonly branching. Finer veins forming a loosely organized, orthogonal pattern. Texture coriaceous.

FiEu "Fimbrial veined, eucalyptoid." Simple, dicotyledonous leaf, 8-10 cm long, 3.0-3.5 cm wide; margin entire; base narrowly 

rounded; apex short acuminate. Secondary veins eucamptodromous, thin, divergence angle 70°-85°, remaining almost 

perpendicular to primary vein until reaching margin. Strong marginal vein present, almost coincident with the margin. 

Texture coriaceous.

Mace Macclintockia sp. cf. M. pugetensis Wolfe. Wolfe (1968).

Meme "Menispermaceous-Piperaceous." Simple, dicotyledonous leaf, 6-8 cm long, 5-6 cm wide; margin entire; base cordate; apex 

long acuminate. Secondary veins acrodromous, three pairs arising at base of lamina, two pairs converging on apex, the other 

pair reaching margin in basal third of lamina. Tertiary veins forming tight loops outside the secondary veins, Intercostal 

tertiary veins perpendicular to secondary veins, unbranched. Finer venation paralleling tertiary veins, forming elongated, 

rectangular areoles. Texture coriaceous. Similar to species of the Menispermaceae or Piperaceae.

Tile "Small leaf, brochidodromous." Simple, dicotyledonous leaf, 2-4 cm long, 1-2 cm wide; margin entire; base acute; apex 

acute. Secondary veins brochidodromous, without extensive looping, simply joining suprajacent secondary vein. 

Intersecondary veins present, rare. Tertiary veins oblique to primary vein, sinuous, branching present. Petiole as long as 5 

mm. Texture coriaceous.

3FHy Trifoliate "Hypserpa." Simple(?), dicotyledonous leaf, 5-8 cm long, 2-3.5 cm wide; margin non-entire; base cuneate; apex 

short acuminate. Teeth small, numerous in apical half of leaflet, absent in basal half, straight apical and basal margins (B-2 

type). Secondary veins thin, acrodromous divergence angle 3Q°-4Q°. Tertiary veins not preserved. Frequently found in 

groups of three, attached at their petiole bases, which are short (<5 mm). They may represent leaflets of a trifoliately 

compound leaf.

Anac Anacardites sp. cf. A. franklinensis Wolfe. Wolfe (1968).

U.S. GOVERNMENT PRINTING OFFICE: 1994-673-046/86052
Burnham HETEROGENEITY IN THE PLANT-FOSSIL RECORD ANALYSIS BASEL) ON THE EOCENE OF WASHINGTON U.S