Palynostratigraphy of the 

Tullock Member (lower Paleocene) of the 

Fort Union Formation in the 

Powder River Basin, Montana and Wyoming 

U.S. GEOLOG·ICAL SURVEY BULLETIN 1917-F 

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Chapter F 

Palynostratigraphy of the 

Tullock Member (lower Paleocene) of the 

Fort Union Formation in the 

Powder River Basin, Montana and Wyoming 

By DOUGLAS J. NICHOLS and JANET L. BROWN 

A multidisciplinary approach to research studies of sedimentary 

rocks and their constituents and the evolution of sedimentary 

basins, both ancient and modern 

U.S. GEOLOGICAL SURVEY BULLETIN 1917 

EVOLUTION OF SEDIMENTARY BASINS-POWDER RIVER BASIN 
U.S. DEPARTMENT OF THE INTERIOR 

MANUEL LUJAN, JR., Secretary 

U.S. GEOLOGICAL SURVEY 

Dallas ,L. Peck, Director 

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 

UNITED STATES GOVERNMENT PRINTING OFFICE: 1992 

For sale by the 

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Library of Congress Cataloging-in-Publication Data 

Nichols,. Douglas j. 

Palynostratigraphy of the Tullock Member (lower Paleocene) of the Fort Union 

Forlllation in the Powder River Basin, Montana and Wyoming I by Douglas j. 

Nichols and janet L. Brown. 

p. em. - (Evolution of sedimentary basins-Powder River Basin ; ch. F) 

(U.S. Geological Survey bulletin ; 1917-F) · 

"A multidisciplinary approach to research studies of sedimentary rocks and their 

constituents and the evolution of sedimentary basins, both ancient and modern." 

Includes bibliographical references. 

Supt. of Docs. no.: I 19.3: 1917F 

1. Geology, Stratigraphic-Paleocene. 2. Palynology-Rocky Mountains 

Region. 3. Palynology-Powder River Basin (Wyo. and Mont.) 

4. Geology-Rocky Mountains Region. 5. Geology-Powder River Basin (Wyo. 

and Mont.) 6. Fort Union Formation. I. Brown, Janet L. II. Title. Ill. Series. 

IV. Series: U.S. Geological Survey bulletin; 1917-F. 

QE75.B9 no. 1917-F 

[QE692] 

557.3s-dc20 91-11674 

[551.7'83] CIP 
CONTENTS 

Abstract Fl 

Introduction Fl 

Previous work Fl 

Materials and method F2 

Lithostratigraphy and sedimentology F3 

Localities and samples F3 

Tullock samples F3 

Stratigraphic control samples F6 

Palynology F6 

General characteristics of the Tullock palynoflora F6 

Stratigraphically restricted taxa F7 

Geographically restricted taxa F7 

Lithofacies associations F7 

Paleocene plant communities F7 

Palynostratigraphy and age F8 

Descriptions of palynomorph taxa FlO 

Algal cysts FlO 

Alete spores Fl3 

Monolete spores Fl3 

Trilete- spores Fl4 

Gymnosperm pollen Fl7 

Angiosperm pollen-Monosulcate · Fl8 

Angiosperm pollen-Tricolpate Fl9 

Angiosperm pollen-Tricolporate F21 

Angiosperm pollen-Syncolporate F22 

Angiosperm pollen-Monoporate F22 

Angiosperm pollen-Triporate F23 

Angiosperm pollen-Multiporate F27 

Angiosperm pollen-Jugate F29 

Angiosperm pollen-Triprojectate F30 

Conclusions F30 

References cited F32 

PLATES 

[Plates follow text] 

l. 

2. 

3, 4. 

5. 

6. 

Algal cysts and monolete spores. 

Monolete and trilete spores. 

Trilete spores. 

Gymnosperm pollen. 

Gymnosperm pollen and monosulcate and tricolpate angiosperm pollen. 

7. Tricolpate and tricolporate angiosperm pollen. 

8. Tricolporate, syncolporate, monoporate, and triporate angiosperm pollen. 

9. Triporate, multiporate, and dyad angiosperm pollen. 

10. Jugate, triprojectate, and multiporate (oculate) angiosperm pollen. 

Contents Ill 
FIGURES 

I. Generalized map showing Powder River Basin in Montana and Wyoming F2 

2. Chart showing stratigraphic nomenclature for uppermost Cretaceous and 

lowermost Tertiary rocks in Powder River Basin F2 

3-4. Maps showing sample localities in the Tullock Member: 

3. Northern Powder River Basin, Montana F4 

4. Southern Powder: River Basin, Wyoming FS 

5. Diagram showing relationship between Cretaceous-Tertiary boundary and 

formation contacts at three sections in Powder River Basin F31 

6. Map showing paleogeography of area of Powder River Basin in earliest 

Paleocene time F32 

TABLE 

I. Alphabetical list of palynomorph taxa from the Tuiiock Member discussed in this 

report, with fuii nomenclatural citations FlO 

IV Contents 
EVOLUTION OF SEDIMENTARY BASINS-POWDER RIVER BASIN 

Palynostratigraphy of the 

Tullock Member (lower Paleocene) of the 

Fort Union Formation in the 

·Powder River B~sin, Montana and Wyoming 

By Douglas J. Nichols and Janet L. Brown 

Abstract 

The palynostratigraphy of the Tullock Member of the Fort 

Union Formation in the Powder River Basin, southeastern 

Montana and northeastern Wyoming, was investigated in 

support of basin analysis research and as a contribution to 

Tertiary palynology of the Rocky Mountain region. Thirty 

samples collected from coal, carbonaceous shale, shale, and 

mudstone at 11 localities were analyzed in detail. Most of 

these samples represent the lower part of the Tullock Member; 

samples from the middle and upper parts of the Tullock also 

were analyzed, and stratigraphic control was provided by 

samples from the overlying Lebo Member of the Fort Union 

and the underlying Lance and Hell Creek Formations. 

The Tullock Member is early Paleocene in age. Tullock 

palynomorph assemblages include species characteristic of 

lower Paleocene palynostratigraphic zones P1 and P2 and 

show resemblance to contemporaneous assemblages 

elsewhere in Montana and Wyoming and in North and South 

Dakota, Colorado, New Mexico, and Alberta, Canada. Basal 

Paleocene zone P1 in the Powder River Basin is charaE:terized 

by presence of the pollen species Momipites inaequalis and M. 

tenuipolus and (in Montana) Wodehouseia fimbriata. The 

overlying zone P2 in the Powder River Basin includes M. 

inaequalis and M. tenuipolus, as well as other species of 

Momipites that characterize this biozone elsewhere. The most 

commonly occurring palynomorphs in the Tullock palynoflora 

are the fern spores Cyathidites diaphana and Laevigatosporites 

spp., conifer pollen assigned to Pityosporites spp., and the 

angiosperm pollen taxa Arecipites tenuiexinous, Tricolpites 

spp., and Ulmipollenites krempii. These species and the 

bryophyte spores Stereisporites spp., fern spores Reticuloidosporites pseudomurii, Toroisporis mafor, and Cleicheniidites 

Manuscript approved for publication January 31, 1991. 

sp., and angiosperm pollen species Pandaniidites typicus, 

Kurtzipites spp., and Triporopollenites spp. are numerically 

abundant in some samples. 

In the taxonomic discussions, 67 taxa are treated, of 

which 41 are pollen of angiosperms, 6 are pollen of 

gymnosperms, 1 2 are spores of bryophytes or pteridophytes 

(principally ferns), and 8 are cysts of algae (principally chlorophytes). Two species are redescribed on the basis of Tullock 

specimens, and 5 new nomenclatural combinations are 

proposed. 

INTRODUCTION 

This study was undertaken in support of a basin 

analysis study (Brown, in press) of the Tullock Member of 

the Fort Union Formation in the Powder River Basin. The 

objective of the palynological research was to provide 

biostratigraphic control for determination of timing of 

Tullock depositional events and to contribute to an 

understanding of Tullock depositional environments. In 

addition, there were two independent objectives: to describe 

the palynoflora of the Tu11ock Member as a contribution to 

Tertiary palynology of the Rocky Mountain region and to 

refine the palynostratigraphy of the lower Paleocene, in the 

Powder River Basin in particular and in the Rocky 

Mountain region in general. Figure 1 is a generalized map of 

the study area; figure 2 shows the stratigraphic 

nomenclature for the study interval. 

Previous Work 

The most important previously published work on the 

palynology of the Tullock Member is that of Leffingwell 

Palynostratigraphy, Tullock Member of Fort Union Formation, Montana and Wyoming Fl 
MONTANA 

41°00'L ____________ _ 

Figure 1. Location of the Powder River Basin in Montana and 

Wyoming. Outline of the basin drawn at the base of the Fox 

Hills Sandstone (Upper Cretaceous). Modified from Lewis and 

Hotchkiss (1981 ). 

MONTANA WYOMING 

Tongue River Member 

c: c: .Q 0 c: ·.;: Lebo Member ::><'0 

t: E 0 0 u.LL 

Tullock Member 

Hell Creek Formation Lance Formation 

Figure· 2. Stratigraphic nomenclature for uppermost 

Cretaceous and lowermost Tertiary rocks in the Powder River 

Basin. 

( 1970), who studied the Tullock and overlying Lebo and 

Tongue River Members of the Fort Union Formation, as 

well as the underlying Lance Formation (Upper 

Cretaceous). Leffingwell's study areas were the type area of 

the Lance Formation and the Gillette coal field, both of 

which are in the southeastern part of the Powder River 

Basin, and the Spotted Horse coal field in the central part of 

the basin, just south of the· Montana-Wyoming State line. 

Leffingwell documented the occurrences of 35 spore and 

pollen taxa in his Assemblage B, which includes the Tullock 

Member and lower part of the Lebo Member. He also 

closely bracketed the position of the Cretaceous-Tertiary 

(K-T) boundary in the type Lance area on the basis of 

palynostratigraphy and found it to be well below the top of 

F2 Evolution of Sedimentary Basins-Pow~er River Basin 

the Lance Formation. In addition to his palynostratigraphic 

results, Leffingwell conducted a careful taxonomic 

investigation of Lance and Fort Union palynomorphs, 

including the description of several new species, which 

provided a sound basis for later studies, including the 

present one. 

Prior to Leffingwell's work, the palynology of the 

lower Paleocene in Montana, Wyoming, and adjacent areas 

had been the subject of studies by Stanley (1965), who 

described palynomorphs from the Ludlow Member of the 

Fort Union in northwestern South Dakota, and Norton and 

Hall (1969), who described palynomorphs from the Tullock 

in the Hell Creek area, Montana. Although Stanley's work 

suffers somewhat from now being some 25 years out of date 

and consequently in need of revision, both of these reports 

proved useful in the present study. 

Nichols and Ott (1978) described some new species 

of pollen from the Fort Union in the Wind River basin, 

Wyoming, and proposed a palynostratigraphic zonation of 

the Paleocene. Their lower Paleocene zones Pl and P2 are 

relevant to the Tullock Member, but the present study 

reveals some interbasinal variations in lower Paleocene 

palynofloras. Recent work by Demchuk ( 1990) in Alberta 

and by Fleming (1990) in New Mexico documents other 

regional variations in lower Paleocene palynostratigraphy. 

Other recent work specifically on the Tullock 

Member includes that of Bohor and others (1987), who 

precisely located the K-T boundary in the type Lance area 

on the basis of palynostratigraphy, trace-element geochemistry, and the presence of shock-metamorphosed 

minerals. Nichols and oth~rs (in press) described in detail 

another K-T boundary locality in the western part of the 

basin. That locality was discovered in the course of the 

present study, ahd some samples from that locality are 

discussed in this report. 

Materials and Methods 

More than 100 samples for palynologic analysis were 

collected from the Tullock Member at 14 outcrop localities 

in the Powder River Basin in the course of this study. 

Among these, 30 samples from 11 localities were selected 

for detailed analysis and discussion in this report. In 

addition to the samples from the Tullock Member, about 50 

samples were collected from the underlying Hell Creek and 

Lance Formations and a few from the overlying Lebo 

Member of the Fort Union Formation. Selected samples 

from this suite were studied to provide biostratigraphic 

(palynostratigraphic) control. Some of the palynomorphs 

recovered from these control samples are discussed here, 

but none are described or illustrated. All samples were 

processed following standard techniques for Tertiary coal 

and clastic sedimentary rocks as described by Doher (1980). 
LITIHOSTRATIGRAPHY AND 

SEDIMENTOLOGY 

Detailed descriptions and interpretations of the lithostratigraphy and sedimentology of the Tullock Member 

have been prepared by Brown (in press); major aspects of 

the unit are summarized here. The Tullock Member is the 

basal unit of the Paleocene Fort Union Formation in the 

Powder River Basin. It consists of fine-grained sandstone, 

sandy siltstone, mudstone, shale, rare thin limestone, and 

coal. In the field the Tullock is distinguished from the 

underlying Hell Creek Formation (in Montana) or Lance 

Formation (in Wyoming) by a sometimes subtle change in 

color from drab or gray-green beds (Hell Creek and Lance) 

to yellow or buff beds that contain coal (Tullock). The base 

of the Tullock is placed at the base of the first coal bed or 

coal zone above the Hell Creek or Lance. The contact of the 

Tullock with the overlying Lebo Member of the Fort Union 

Formation tends to be gradational but is marked by a change 

from buff sandstone and shale to generally drab (dark gray 

to olive gray) shale. The Tullock Member ranges in 

thickness from 113 m in the northwestern part of the basin 

to 439 m in the southeast (Brown, in press). 

The geometry of Tullock sandstone bodies as 

determined from integration of subsurface and outcrop data 

(Brown, unpublished data) indicates a dominantly finegrained fluvial system consisting of small isolated stream 

courses incised into mudstones of floodplain origin. Floodplain sediments comprise more than 70 percent of the 

Tullock Member. The vertical succession of sedimentary 

structures is typical of fining-upward sequences that 

characterize fluvial systems. Isolated channel-form 

sandstones, as wide as 300 m, contain rare lateral accretion 

deposits and are indicative of low-sinuosity channels that 

had limited sweep or migration over the floodplain. Paleocurrent directions determined from measurements on trough 

cross-sets show that stream flowed to the east and northeast. 

A lack of alluvial ridges in channels indicates little 

difference between elevation of river beds and the floodplain surface. Lack of prominent alluvial ridges is due to the 

dominance of clay, silt, and fine sand in overbank deposits 

and the presence of bank vegetation that prevented coarsegrained bedload sediment from washing onto the floodplain 

surface. Successive sediment pulses were responsible for 

zones of convolute bedding and destruction of some primary structures by liquefaction. 

In total, these features suggest a small-scale fluvial 

system that traversed a stable floodplain of low relief in 

which small lakes were present and peat-forming mire 

environments were common. Palynomorphs produced by 

the local and regional vegetation tended to be deposited in 

fine-grained facies, including mudstone, shale, carbonaceous shale, and coal. Where those facies were not 

subjected to penecontemporaneous or postdepositional 

oxidation, palynomorphs were preserved. 

It has been common practice among field geologists 

working in the Powder River Basin and elsewhere in the 

Rocky Mountain region to equate the Cretaceous-Tertiary 

(K-T) boundary with the contact between the Tullock 

Member and the underlying formations. Brown (1962) 

extensively reviewed the history of this practice and 

concluded that the "formula" (attributed to Calvert, 1912) 

for locating the K-T boundary at the first persistent coal 

zone above the stratigraphically highest dinosaur is valid. 

This approximation may serve as a mapping criterion, but 

the lithostratigraphic contact and the chronostratigraphic 

time-line are not necessarily coincident. As discussed in 

more detail later, our palynostratigraphic study shows that 

the K-T boundary is indeed at the base of the Tullock in 

some places in the basin but is below it in others. 

LOCALITIES AND SAMPLES 

Tullock Samples 

Localities and samples from the Tullock Member are 

described below. The locations of sampling sites in 

Montana are shown in figure 3; those in Wyoming are 

shown in figure 4. 

East Burnt Creek.-USGS paleobotany locality 

D6936; SE1

/4SW1t4SW1/4 sec. 36, T. 4 N., R. 35 E., Treasure 

County, Mont., Hope Ranch 7.5' quadrangle; basal Tullock 

Member on north side of road along East Burnt Creek 

(tributary to Tullock Creek); K-T transition interval 

reported by Brown and Nichols (1988). Sample D6936-I: 

coal, lowest bed in Tullock, thin bed about 3 m above K-T 

boundary and about 0.6 m below prominent thicker coal bed 

assumed to be coal bed A of Rogers and Lee (1923). 

Jacobs Coulee.-USGS paleobotany locality D6940; 

NW1/4NW1/4NW1/4 sec. 15, T. 5 N., R. 35 E., Treasure 

County, Mont., Eldering Ranch 7.5' quadrangle; lower part 

of Tullock Member along abandoned road in Jacobs Coulee 

(tributary of Unknown Creek): in the extreme northwestern 

part of the basin. Sample 06940-BB: mudstone (gray, 

slightly silty), 12 em below thin coal that is about 3m below 

coal bed A of Rogers and Lee (1923). Sample D6940-AA: 

coal, from thin bed about 3m below lowest prominent coal 

bed. Sample D6940-F: upper part of prominent, 90-cmthick coal (assumed to be coal bed A of Rogers and Lee, 

1923). 

East Beaver Creek.-USGS paleobotany locality 

D6937; near center NE1

/4NE1/4 sec. 34, T. 4 N., R. 37 E., 

Treasure County, Mont., Minnehaha Creek North 7 .5' 

quadrangle; lower part of Tullock Member on East Beaver 

Creek road, near where Rogers and Lee ( 1923) measured 

Palynostratigraphy, Tullock Member 'of Fort Union Formation, Montana and Wyoming F3 
__ ___l_~ONTAN~- __________ L _________ _ 

WYOMING 0 50 KILOMETERS 

Figure 3. Sample localities in the Tullock Member of the Fort Union Formation (patterned areas), northern 

Powder River Basin, Montana. Outline of the basin drawn at the base of the Fox Hills Sandstone (Upper 

Cretaceous); location of basin shown in figure 1. 

about 90 m of "typical" Tullock. Sample D6937-D: coal, 

from lowermost prominent bed exposed in area, which is 46 

em thick (assumed to be coal bed A of Rogers and Lee). 

Sample D6937-H: coal, from bed about 7.5 em thick that is 

about 3.7 m above coal bed A (coal bed B of Rogers and 

Lee?). Sample D6937-K: carbonaceous shale (black, fissile), just below probable coal bed C. Sample D6937-L: 

coal, from lower part of 56-em-thick bed about 13.4 m 

above bed A (assumed to be coal bed C of Rogers and Lee). 

Reno Creek.-USGS paleobotany locality D7411; 

SW1/4 sec. 12, T. 4 S., R. 36 E., Big Hom County, Mont., 

Thompson Creek NW 7 .5' quadrangle; lower part of Tullock Member in bluffs north of Reno Creek on Crow Indian 

Reservation. Sample D7411-C: shale (tan, with plant 

fragments), just below 18-cm-thick coal bed that marks base 

of Tullock Member. Sample D7411-E: coal, lowermost part 

F4 Evolution of Sedimentary Basins-Powder River Basin 

of 1-m-thick bed about 8 m above base of Tullock. Sample 

D7411-F: coal, uppermost part of 1-m-thick bed, about 9 m 

above base of Tullock. Sample D7411-I: shale (light gray to 

tan, with plant fragments), 23.8 m above base of Tullock 

Member. Sample D7411-J: mudstone (gray, coaly, slightly 

silty), 25.3 m above base of Tullock. Sample D7411-K: 

shale (tan to brown), about 30 m above base of Tullock. 

Dry Creek.-USGS paleobotany locality D7000; 

NWlf4NW1

/4NE1/4 sec. 6, T. 56 N., R. 69 W., Campbell 

County. Wyo., Bowman Hill 7.5' quadrangle; lower part of 

Tullock Member in bluff on qlt bank of Dry Creek, south of 

the Montana-Wyoming Stat~' line and near the east-central 

margin of the basin. Sample D7000-B: carbonaceous shale 

(black, fissile), 4.6 m below base of prominent 1.4-m-thick 

coal bed. 
107° MONTANA 106° --~------------------l----------- WYOMING Dry Cree 

50 KILOMETERS 

Figure 4. Sample localities in the Tullock Member of the Fort Union Formation (patterned areas), southern Powder River Basin, 

Wyoming. Outline of the ·basin drawn at the base of the Fox Hills Sandstone (Upper Cretaceous); location of basin shown in 

figure 1. 

Sussex.-USGS paleobotany locality D7299; 

SWV4SE1/4 sec. 3, T. 42 N., R. 79 W., Johnson County, 

Wyo., Sussex 7.5' quadrangle; basal Tullock Member at 

K-T boundary locality of Nichols and others (in press), 

along the southwestern edge of the basin. Sample D7299-J: 

coal, lowermost 1 em of basal Tullock coal, just above K-T 

boundary. Sample D7299-0: coal, 24 em above K-T 

boundary. Sample 07299-R: carbonaceous shale (brown), 

3.3 m above K-T boundary. 

Lance Creek I.-USGS paleobotany locality D71 00; 

SEV4SWV4SE 1.4 sec. 5, T. 38 N., R. 65 W., Niobrara 

County, Wyo., Dixon Ranch 7.5' quadrangle; basal Tullock 

Palynostratigraphy, Tullock Member of Fort Union Formation, Montana and Wyoming F5 
Member near K-T boundary locality of Bohor and others 

(1987), in the southeastern part of the basin. Sample 

D7100-B: mudsrone (brown, slightly silty, with plant 

fragmems), about 3.5 m above K-T boundary. Sample 

D7100-C: carbonaceous shale (black), 5.2 m above K-T 

boundary. 

Lance Creek 2.-VSGS paleobotany locality D7137; 

SW1/4SW1/4SE1/4 sec. 5, T. 38 N., R. 65 W., Niobrara 

Coumy, Wyo., Dixon Ranch 7.5' quadrangle; ourcrop of 

K-T boundary claystone in gully west of K-T boundary 

locality ofBohor and others (1987). Sample D7137-E: K-T 

boundary claystone. Sample D7137-G: coal, lower pan of 

4.5-cm-thick bed above K-T boundary (separated from 

boundary claysrone layer by 3.5 em of gray shale). Sample 

D7137-I: carbonaceous shale (brown, with plant 

fragments), 20 em above K-T boundary. 

South Snyder Creek.-VSGS paleobotany locality 

D7422; SW1

/4NW1/4NEV4 sec. 8, T. 39 N., R. 65 W., 

Niobrara Coumy, Wyo., Garland Draw 7.5' quadrangle; 

basal pan of Tullock Member exposed in gully on north side 

of road. Sample D7422-E: shale (tan, with jarosite and plant 

fragments), lower parting in coal bed marking base of 

Tullock Member. Sample 07422-F: shale (tan, with jarosite 

and plant fragments), upper paning in basal Tullock coal. 

Leverett Butte.-VSGS paleobotany locality D7421; 

center to SW1

/4SW1/4 sec. 27, T. 39 N., R. 66 W., Niobrara 

County, Wyo., Calf Draw 7.5' quadrangle; middle part of 

Tullock Member (based on mapping by Dobbin and others, 

1957) exposed in prominent butte and adjacent gully near 

abandoned Leverett post oftice. Sample 07421-A: coal, 

from 13-cm-thick bed that is lowest coal exposed in gully 

on southwest side of road. Sample 07421-D: carbonaceous 

shale (black, fissile), at head of gully and about 21.6 m 

above 07421-A. Sample 07421-E: shale (brown, with 

jarosite and plant fragments), just above 20-cm-thick coal 

bed at base of butte on northeast side of road. Sample 

07421-F: mudsrone (gray, silty), abour 8.5 m above base of 

butte and about 30m above sample 07421-A. 

Cow Creek.-VSGS paleobotany locality D7419; 

NW1/4SW1/4 sec. 35, T. 39 N., R. 67 W., Niobrara County, 

Wyo., Pinnacle Rocks 7 .5' quadrangle; upper Tullock 

Member exposed in knob on northwest side of Cow Creek 

Road, near Tullock-Lebo contact as mapped by Dobbin and 

others (1957), in the southeastern part of the basin. Sample 

07419: shale (tan, with plant fragments). 

Stratigraphic Control Samples 

The Hell Creek Formation was sampled at the East 

Burnt Creek locality, and the Lance Formation was sampled 

at the Sussex, Lance Creek, and South· Snyder Creek 

localities. The palynomorph assemblages recovered from 

these samples are typical of the upper Maastrichtian W odehouseia spinata Assemblage Zone (Nichols and others, 

1982) and differ markedly in composition from the Tullock 

F6 Evolution of Sedimentary Basins-Powder River Basin 

palynoflora. The striking change in palynoflora!' 

assemblages marks the Cretaceous-Tertiary boundary in the 

Powder River Basin. 

The Lebo Member was sampled at USGS paleobotany locality D7418 (SW1

/4NW1/4 sec. 3, T. 38 N., R. 67 W., 

Niobrara County, Wyo., Pinnacle Rocks 7.5' quadrangle), in 

the southeastern pan of the basin. Here the lowermost part 

of Lebo is exposed in a cut bank on the sourh side of Cow 

Creek, near the Tullock-Lebo contact as mapped by Dobbin 

and others (1957). A sample collected by Susan Foster of 

the Montana Bureau of Mines and Geology provided 

stratigraphic control in our study. That locality is USGS 

paleobotany locality D7591 (SW1/4SEV4SW1/4 sec. 11, T. 9 

S., R. 51 E., Powder River County, Mont., Wild Bill Creek 

7 .5' quadrangle) and is in the Lebo Member as mapped by 

Robinson and others (1964). Assemblages from these 

localities differ in composition from Tullock assemblages 

and help to determine the distinguishing characteristics of 

lower versus middle Paleocene palynofloras in the basin. 

PALYNOLOGY 

General Characteristics of the 

Tullock Palynoflora 

The Tullock palynoflora includes at least 67 palynomorph taxa, among which 8 are listed here as "spp." 

(meaning that more than one species is included in the 

taxon); thus 75 or more different species actually are 

identifiable. Among the taxa discussed here, 12 are spores 

of bryophytes or pteridophytes (principally ferns), 6 are 

pollen of gymnosperms, 41 are pollen of angiosperms, and 

8 are cysts of various groups of algae (principally chlorophytes). 

The most commonly occurring taxa are the fern 

spores Cyathidites diaphana and two species of Laevigatosporires, pollen of coniferous gymnosperms assigned to 

Pityosporites spp., and the angiosperm pollen taxa Arecipites tenuiexinous, Tricolpites spp., and Ulmipollenites krempii, which were present in 80 percent or more of the samples 

examined in detail in this study. The fern spore Rericuloidosporites pseudomurii was present in 70 percent of the 

samples and also may be considered a characteristic species 

of the Tullock palynoflora. The taxa listed above are not 

only present at least in low number in most samples of the 

Tullock Member but also may be locally abundant and tend 

to dominate assemblages in some samples. Other taxa that 

are locally abundant are the fern spores Gleicheniidites sp. 

and Toroisporis major and the angiosperm pollen species 

Fraxinoipol/enites variabilis, K urtzipites circular is, and K. 

trispissatus. 
Local vananons in abundance aside, the Tullock 

palynoflora is essentially uniform in aspect throughout the 

Powder River Basin. There are minor but imponant 

differences, however, in both stratigraphic and geographic 

distribution of individual species. 

Stratigraphically Restricted Taxa 

Kurtzipites circularis and K. trispissarus range into 

the Tullock from the underlying Cretaceous units but do not 

range above the Tullock and thus may be considered 

characteristic of the Tullock palynoflora, serving to 

distinguish it from the palynofloras of the Lebo and Tongue 

River Members. The lower pan of the Tullock Member both 

in Montana and Wyoming contains rare occurrences of the 

typically Upper Cretaceous pollen species Aquilapollenites 

rericularus, which has been reponed previously in the 

lowemJost Paleocene in Albena (Jerzykiewicz and Sweet, 

1986). Three biostratigraphically imponant species of the 

angiospe1m pollen genus Momipites (M. lefjingwellii, M. 

waltmanensis, and M. wyomingensis) are present only in the 

middle and upper pans of the Tullock. These species 

indicate that the middle and upper pans of the Tullock 

Member are within palynostratigraphic zone P2 of Nichols 

and Ott (1978) and are of late early Paleocene age. The 

absence of Momipites lefjingwellii from the lower part of 

the Tullock in the Powder River Basin indicates a 

significant difference between the palynostratigraphic 

definition of zone PI in this basin and that for the Wind 

River Basin, where the zone was originally defined (Nichols 

and Ott, 1978). The absence from the Tullock Member of 

other biostratigraphically imponant palynomorphs is also 

significant. Momipites anellus, M. triorbicu/aris, M. ventifluminis, and Aquilapollenites spinulosus, which are 

characteristic of lower middle Paleocene zone P3 of Nichols 

and Ott ( 1978), were not found in any of the Tullock 

samples but were found in the lower pan of the overlying 

Lebo Member of the Fon Union Formation in the eastern 

and southern pans of the basin. 

Geographically Restricted Taxa 

Species of the morphologically unique and biostratigraphically imponant pollen genus Wodehouseia (W. fimbriara and W. spinata) were found only in the Montana part 

of the Powder River Basin in this study. Wodehouseia 

fimbriata is a characteristic species of palynostratigraphic 

zone P2 in Albena (Demchuk, 1990) but is near the 

southern limit of its paleogeographic range in the Pow.der 

River Basin and is rarely found in the Paleocene of the 

United States. Wodehouseia spinata is another typically 

Upper Cretaceous species that, like Aquilapollenites reticu/arus, persists into the lowermost Paleocene in southern 

Canada (Jerzykiewicz and Sweet, 1986). Two pollen 

species, Liliacidites leei and Retitrescolpites angulolumino- · 

sus, were found only in samples from the Wyoming part of 

the basin. Both were originally described from the Paleocene of New Mexico (Anderson, 1960) and probably 

represent elements of a southern flora that were near the 

northern limits of their paleogeographic ranges in 

Wyoming. 

Lithofacies Associations 

The general uniformity of the Tullock palynoflora 

with respect to occurrences of most taxa extends to the 

lithofacies associations of the palynomorphs. That is, most 

taxa can be found in all fine-grained, non-oxidized 

sedimentary rocks within the Tullock, including mudstone, 

shale, carbonaceous shale, and coal. There are a few 

exceptions, but they most likely are of little importance. 

Within the limits of this study, some of these occurrence 

patterns may be artifacts of sampling. The probable 

bryophtye spore Zlivisporis novomexicanum and the 

palynomorph designated algal cyst type 3 were found in all 

rock types named above except coal; spores of the aquatic 

fern Ghoshispora bella and algal palynomorphs designated 

Tetraporina sp. and algal cyst type 2 were not found in 

samples of shale (except carbonaceous shale). The general 

unifonnity of distribution of the Tullock palynoflora on a 

presence/absence basis is a fortunate circumstance for 

biostratigraphy because if local plant communities had too 

strong an influence on composition of palynomorph 

assemblages, those assemblages would be of limited use in 

age determination. All Tullock palynomorph assemblages 

are not alike, however, and, especially when relative 

abundances of taxa such as those mentioned previously are 

considered, it is possible to derive information about the 

kinds of plant communities that inhabited the Powder River 

Basin in early Paleocene time. 

Paleocene Plant Communities 

The peat-forming mires that eventually formed the 

coal deposits of the Tullock Member were not forested 

swamps dominated by taxodiaceous trees (relatives of living 

Taxodium or Glyptostrobus), as were those that formed 

coals of the Tongue River Member of the Fort Union 

Formation (described by Pocknall and Flores, 1987). Tullock mires were inhabited mostly by ferns. In this study nine 

Tullock coal beds were studied in detail, beds from a few 

centimeters to 1 m thick. Fern spores are the most numerous 

palynomorphs in all of them, especially the species of 

Laevigatosporites, Reticuloidosporites, and Cyathidites, 

although all have fairly diverse palynomorph assemblages 

reflecting fairly diverse plant communities. Spores of 

Palynostratigraphy, Tullock Member of Fort Union Formation, Montana and Wyoming F7 
species of Stereisporites, which were produced by bryophytes closely related to living sphagnum moss, are 

prominent in some assemblages from Tullock coals. Tullock coal assemblages thereby contrast markedly with most 

Tongue River coal assemblages, which tend to be low in 

diversity and dominated by pollen of taxodiaceous conifers 

(Pocknall and Flores, 1987). Taxodiaceous pollen (here 

ascribed to Taxodiaceaepollenites hiatus) is present in many 

Tullock samples but always as a relatively minor 

component of assemblages. Smaller amounts of biomass 

presumably produced by fern-dominated mires rather than 

by swamps dominated by coniferous trees may account in 

part for Tullock coals being generally thinner and less 

laterally extensive than Tongue River coals. 

All Tullock sediments and their contained palynomorphs were deposited in periodically wet to subaquatic 

environments, but some show clearer evidence of the 

presence of wetland plant communities than do others. 

Sample 07000:-B, a fissile carbonaceous shale from the Dry 

Creek locality, yielded an unusually diverse assemblage 

including the angiosperm pollen Pandaniidites typicus, 

which is probably related to living Pandanus, most species 

of which inhabit marshy areas; Penetetrapites inconspicuus, which has morphological resemblance to pollen 

of living sedges; and Sparganiaceaepollenites sp., which 

probably is related to living marsh grass (Sparganium) or 

cattail (Typha). Also present in this assemblage are massulae and microspores of Azolla cretacea, an aquatic fern; 

spores of Stereisporites (Sphagnaceae, mosses); and cysts of 

aquatic algae, including Schizophacus sp., which is related 

to the living chlorophyte alga Spirogyra; Tetraporina sp., 

which is related to the living chlorophyte alga Mougeotia; 

and algal cyst type 3. Sample p71 00-C, a carbonaceous 

shale from locality Lance Creek 1, yielded an assemblage 

that includes Pandaniidites typicus, Penetetrapites 

inconspicuus, Azolla cretacea, algal cyst type 3, and 

unusual numbers of spores of the aquatic fern Ghoshispora 

bella. Sample 06937-K, a fissile carbonaceous shale from 

beneath a coal bed at the East Beaver Creek locality, yielded 

an unusual abundance and variety of freshwater algal cysts, 

including Schizophacus laevigatus, which is related to 

living Spirogyra; Sigmopollis hispidus; Tetraporina sp.; and 

forms of uncertain affinity designated algal cyst types 1 and 

2. Open, standing freshwater is indicated by these species of 

algal cysts. Also present in the assemblage from this sample 

is Sparganiaceaepollenites sp. The assemblages of all three 

samples suggest the presence of wetland environments. 

Samples that have unusual concentrations of palynomorphs of one or a very few species may reflect local plant 

communities. The angiosperm pollen species Kurtzipites 

circularis dominates the assemblage from sample 07419, 

shale from the upper part of the Tullock at the Cow Creek 

locality. Using multivariate analysis, Fleming (1990) 

determined that lower Paleocene assemblages from the 

F8 Evolution of Sedimentary Basins-Powder River Basin 

Raton basin of Colorado and New Mexico that were 

dominated by this species are indicative of marsh 

environments. Presence of a similar marsh plant assemblage 

in sample 07 419 is further supported by occurrences of 

pollen of Sparganiaceaepol/enites and the algal cysts 

Schizophacus laevigatus and Schizophacus sp. Sample 

07137-I, carbonaceous shale from locality Lance Creek 2, 

is dominated by the angiosperm pollen species Fraxinoipollenites variabilis, but the ecological significance of this 

species is not known. The only other noteworthy feature of 

the assemblage from 07137-I is the presence ·of some 

reworked Cretaceous marine and nonmarine palynomorphs. 

Assemblages from coal samples that are dominated by fern 

spores or have concentrations of sphagnaceous spores were 

discussed above. They indicate the composition of plant 

communities of peat-forming mires. 

In contrast with plant communities of local 

environments, the most commonly occurring palynomorph 

taxa provide insight into the nature of the regional flora of 

the Powder River Basin in early Paleocene time. As 

mentioned, these taxa include fern spores assigned to the 

genera Cyathidites, Laevigatosporites, and Reticuloidosporites; conifer pollen assigned to Pityosporites; and three 

angiosperm pollen taxa, Arecipites tenuiexinous, Tricolpites 

spp., and Ulmipollenites krempii. The ferns probably were 

most common in the wet lowland environments that 

included peat-forming mires. The conifer pollen, which is 

persistent in occurrence but nowhere dominant in the 

Tullock, probably was transported to the depositional area 

from adjacent upland areas to the west. The abundance of 

Arecipites tenuiexinous, pollen most likely produced by 

palms, attests to the presence of thermophilic vegetation and 

suggests that palms were included among the forests in 

Tullock time. Species of Tricolpites and Ulmipollenites 

krempii probably were produced by deciduous trees such as 

ancestral members of the modem families Platanaceae and 

Ulmaceae, respectively, which evidently were prevalent in 

the Powder River Basin in the early Paleocene. 

Palynostratigraphy and Age 

The K-T boundary is a precise chronostratigraphic 

datum in the Powder River Basin. It has been defined within 

centimeters at two sites that were also sample localities in 

the present study, Lance Creek in the southeastern part of 

the basin (Bohor and others, 1987) and Sussex in the 

southwestern part of the basin (Nichols and others, in press). 

At both localities an abrupt change in palynologic 

assemblages coincides with an anomalous concentration of 

iridium and the presence of shock-metamorphosed quartz 

grains. The K-T boundary also was bracketed within 

several meters at the East Burnt Creek locality in the 

northwestern part of the basin during this study (Brown and 

Nichols, 1988). The iridium anomaly was not located at 

East Burnt Creek, presumably because the higher energy 
depositional environment prevented deposition of the 

typical K-T boundary claystone. Rocks of the Lance and 

Hell Creek Formations at all three K-T boundary localities 

in the Powder River Basin yield palynomorphs 

characteristic of the Wodehouseia spinata Assemblage 

Zone, a palynologic biozone known throughout the central 

and northern Rocky Mountain region (Nichols and others, 

1982). Palynologic assemblages from rocks of the Tullock 

Member above the K-T boundary lack this assemblage. The 

Tullock Member assemblages include the palynomorphs 

discussed in this report. There are important implications for 

the age of the Lance and Hell Creek Formations and the 

Tullock Member of the Fort Union Formation that follow 

from detailed analysis of the K-T boundary. 

In the Lance Creek area Clemens ( I964) placed the 

Lance-Fort Union contact at the base of the lowest 

persistent coal bed above the stratigraphically highest 

dinosaur remains, using the "formula" of Calvert (19I2) as 

espoused by B'rown ( 1962). In the Lance Creek area the 

lowest persistent coal is a bed about 0.6 m thick. Leffingwell (1970) noted that the palynologically defined K-T 

boundary is about 9.5 m below the formation contact as 

designated by Clemens. Leffingwell recommended 

lowering the position of the formation contact to the base of 

a thin (about 18 em) coal bed from which his lowest 

Tertiary sample was collected. Bohor and others (1987), 

who precisely located the K-T boundary within the 

equivalent interval near the section studied by Clemens and 

Leffingwell, placed the formation contact at the base of a 

coal bed 3-4 em thick. Neither Leffingwell nor Bohor 

selected coal beds that meet Brown's criterion of being 

"persistent." It is not even clear that the thin bed selected in 

each case was the same one. Leffingwell's diagram (1971, 

fig. 4) shows a second thin (about 2.5 em) coal below the 

one he selected as the base of the Fort Union and above his 

highest Cretaceous sample. That coal could be Cretaceous, 

or, if it is Tertiary, it could be equivalent to the one 

illustrated by Bohor and others (1987, fig. 3 ). More likely, 

none qf these thin beds persists laterally for any significant 

distance. The formation contact is best recognized where 

Clemens placed it, at the thicker, persistent bed, which is a 

mappable horizon. In any event, as much as 9 or 10 m of the 

upper part of the Lance Formation in the Lance Creek area 

is earliest Paleocene in age. 

At the East Burnt Creek locality it is evident that the 

uppermost part of the Hell Creek Formation is earliest 

Paleocene·in age. This assumes that the base of the Tullock 

Member of the Fort Union in this area is taken to be the base 

of the lowest persistent coal bed in that area, coal bed A of 

Rogers and Lee (1923). In our study of the area (Brown and 

Nichols, I988), we found the highest Cretaceous palynomorph assemblage to be 4.3 m below coal bed A. A sample 

having poor recovery but probably Paleocene in age was 

collected 2.4 m above the highest Cretaceous sample and 

about 1.3 m below coal bed A. The situation is potentially 

complicated by a color change, from greenish gray below to 

buff above, which also has been used as a field criterion to 

distinguish the Hell Creek and Fort Union Formations and 

which occurs 7.6 m below coal bed A along East Burnt 

Creek. If the base of the Tullock was placed at the color 

change instead of at the base of the coal, as much as 3 m or 

more of the basal Tullock would be Cretaceous in age. We 

place the formation contact at the base of the lowest coal 

(coal bed A) at East Burnt Creek, which leaves the Tullock 

entirely Paleocene. 

At the Sussex K-T boundary locality there are no 

such problems because the formation contact and the K-T 

boundary coincide. Samples just below the lowest coal 

above the highest dinosaur remains yield palynomorphs of 

the Wodehouseia spinata zone and the coal yields typical 

Tullock palynomorphs (Nichols and others, I992). 

The basal part of the Tullock Member is early 

Paleocene in age and presumably equivalent to palynostratigraphic zone PI of Nichols and Ott (1978). The age 

determination is based on the stratigraphic relations of the 

basal Tullock and the K-T boundary. The composition of 

basal Tullock palynomorph assemblages does not 

completely match that of zone PI assemblages from the 

Wind River Basin, however. Differences may be attributed 

to interbasinal variation in floras in earliest Paleocene time, 

but, because the K-T boundary was not precisely located in 

the Wind River Basin, it is possible that zone Pl does not 

actually represent the basal Paleocene there. The present 

study is a more extensive and more complete analysis of the 

nature of the lower Paleocene palynoflora of the Rocky 

Mountain region than was that of Nichols and Ott (1978), 

which concentrated on definition of palynostratigraphic 

zones based on a few biostratigraphically important species. 

The middle and upper parts of the Tullock Member 

are within palynostratigraphic zone P2 of Nichols and Ott 

( I978) and are of late early Paleocene age. This age 

determination is based on comparison of assemblages from 

the Wind River and Powder River Basins and on the 

composition of assemblages from our stratigraphic control 

samples from the lower part of the Lebo Member of the Fort 

Union Formation in the Powder River Basin. The Lebo 

samples yielded assemblages characteristic of lower middle 

Paleocene zone P3 of Nichols and Ott (1978). 

Lithologic changes between the underlying Lance and 

Hell Creek Formations and the Tullock Member or between 

the Tullock and the overlying Lebo Member cannot account 

for the changes in palynomorph assemblages on which our 

palynostratigraphy is based. Local depositional environment can affect the kinds of plants that are present and 

therefore the kinds of palynomorphs that tend to be 

preserved in sediments, but the differences in assemblages 

discussed above are regional in extent and independent of 

lithology. The changes that mark the K-T boundary are now 

known throughout western North America (references in 

Nichols and others, in press). The changes in assemblages 

Palynostratigraphy, Tullock Member of Fort Union Formation, Montana and Wyoming F9 
Table 1. Alphabetical list of palynomorph taxa from the Tullock Member discussed in this 

report, with full nomenclatural citations 

[Page numbers in brackets refer to location of discussion of the taxa in this report) 

Algal cyst type 1 [p. F13] 

Algal cyst type 2 [p. F13] 

Aquilapollenites reticulatus (Mtchedlishvili 1961) Tschudy & Leopold 1971 [p. F30] 

Araucariacites sp. [p. F17] 

Arecipites tenuiexinous Leffingwell1971 [p. F18] 

Azolla cretacea Stanley 1965 [p. F14] 

Brevicolporites co/pella Anderson 1960 [p. F21] 

Chenopodipollis spp. [p. F27] 

Cicatricosisporites spp. [p. F14] 

Corollina sp. [p. F17] 

Cupanieidites inaequalis Leffingwell 1971 [p. F22] 

Cyathidites diaphana (Wilson & Webster 1946) n. comb. [p. F14] 

Cycadopites scabratus Stanley 1965 [p. F17] 

Discoidites p(liVistriatus (Norton in Norton & Ha111967) n. comb. [p. F19] 

Dyadonapites reticu/atus Tschudy 1973 [p. F29] 

Erdtmanipollis cretaceus (Stanley 1965) Norton in Norton & Ha111969 [p. F28] 

Fraxinoipollenites variabilis Stanley 1965 [p. F20] 

Ghoshispora bella (Kondinskaya 1966) Srivastava 1978 [p. F15] 

Gleicheniidites sp. cf. Gleichenia triangula Stanley 1965 [p. F16] 

Inaperturotetradites scabratusTschudy 1973 ·[p. F29] 

Incertae sedis type 1 [p. F13] 

Kurtzipites cirr:ularis (Norton in Norton & Hall1969) Srivastava 1981 [p. F21] 

Kurtzipites trispissatus Anderson 1960 [p. F21] 

Laevigatosporites sp. L [p. F13] 

Laevigatosporites sp. S [p. F14] 

Li/iacidites /eei Anderson 1960 [p. F19] 

Momipites inaequalis Anderson 1960 [p. F23] 

Momipites leffingwellii Nichols & Ott 1978 [p. F24] 

Momipites tenuipolus Anderson 1960 [p. F24] 

Momipites wa/tmanensis Nichols & Ott 1978 [p. F24] 

Momipites wyomingensis Nichols & Ott 1978 [p. F24] 

Nyssapollenites spp. [p. F22] 

Osmundacidites sp. [p. F16] 

Pandaniidites typicus (Norton in Norton and Hall1969) Sweet 1986 [p. F22] 

from zone P2 to P3 that coincide with the Tullock-Lebo 

transition in the Powder River Basin were defined within a 

single lithostratigraphic unit in the Wind River Basin, the 

lower unnamed member of the Fort Union Formation. 

Finally, the most commonly occurring taxa of the Tullock 

palynoflora were recovered from all fine-grained rock types 

sampled in our study. 

Descriptions of Palynomorph Taxa 

Palynomorpd taxa in the Tullock palynoflora are 

discussed in the following sections, in which they are 

grouped according to their presumed botanical affinity and 

then in major morphologic categories. Within each morphoFl 0 Evolution of Sedimentary Basins-Powder River Basin 

logic category, the sequence is alphabetical. Table 1 is a list 

of all taxa discussed, arranged alphabetically and with full 

nomenclatural citations and page-number references to the 

following section. 

Algal Cysts 

Schizophacus /aevigatus (Stanley) n. comb. 

Plate 1, figure 1 

Basionym: Schizosporis laevigatus Stanley, 1965, p. 268-269, pl. 23, figs. 

6, 7; pl. 37, figs. 4, 5 (non Schizosporis laevigatus Venkatachala, 1969, p. 

216, pl. 6, figs. 13-15). 

Schizophacus laevigatus (Stanley) n. comb. includes 

elongate, biconvex bodies, ovoid in outline, that tend to split 

into two equal halves along a simple line of dehiscence that 
Table 1. Alphabetical list of palynomorph taxa from the Tullock Member discussed in this 

report, with full nomenclatural citations-Continued 

·[Page numbers in brackets refer to location of discussion of the taxa in this report] 

Penetetropites inconspicuus Sweet 1986 [p. F28] 

Pityosporites spp. [p. F17] 

Podocwpidites maximus (Stanley 1965) Norton in Norton & Hall 1969 [p. F18] 

Quercoidites spissus Leffingwell1971 [p. F20] 

Reticuloidosporites pseudomurii Elsik 1968 [p. F14] 

Retitrescolpites anguloluminosus (Anderson 1960) Frederiksen 1979 [p. F20] 

Rhoipites spp. [p. F22] 

Rousea spp. [p. F20] 

Schizophacus /aevigatus (Stanley 1965) n. comb. [p. FlO] 

Schizophacus sp. [p. F12] 

Sigmopollis hispidus Hedlund 1965 [p. F12] 

Sigmopollis sp. [p. F12] 

Simplicepollis rollus (Stanley 1965) n. comb. [p. F29] 

Sparganiaceaepollenites sp. cf. Sparganium globites Wilson & Webster 1946 [p. F23] 

Stereisporites spp. [p. F16] 

Striatopollis tectatus Leffingwell 1971 [p. F20] 

Syncolporites minimus Leffingwell 1971 [p. F22] 

Taxodiaceaepollenites hiatus (Potonie 1931) Kremp 1949 [p. F18] 

Tetroporina sp. [p. F12] 

Thomsonipollis magnijicus (Pflug & Thomson in Thomson & Pflug 1953) Krutzsch 1960 [p. F25] 

Tilia vescipites Wodehouse 1933 [p. F22] 

Toroisporis major (Pflug in Thomson & Pflug 1953) Stanley 1965 [p. F16] 

Triatriopollenites granulatus (Simpson 1961) Leffingwell1971 [p. F25] 

Triatriopollenites subtriangulus (Stanley 1965} Frederiksen 1979 [p. F25] 

Tricolpites hians Stanley 1965 [p. F20] 

Tricolpites spp. [p. F21] 

Triporopollenites granilabrotus (Stanley 1965) n. comb. [p. F26] 

Triporopollenites infrequens (Stanley 1965) Frederiksen 1988 [p. F26] 

Triporopollenites plektosus Anderson 1960 [p. F27] 

Ulmipollenites krempii (Anderso·n 1960) Frederiksen 1979 [p. F27] 

Wodehouseia fimbriata Stanley 1965 [p. F28] 

Wodehouseia spinata Stanley 1965 [p. F28] 

Zlivispon"s novomexicanum (Anderson 1960) Leffingwell1971 [p. F17] 

encircles the body lengthwise. The wall is single-layered 

and psilate. Ten Tullock specimens measured were from 57 

to 98 flm in maximum dimension. Specimens described by 

Venkatachala ( 1969) as Schizosporis /aevigatus are similar 

but are larger and have thicker walls; if that species is not 

synonymous with Schizophacus laevigatus n. comb., the 

name Schizosporis /aevigatus Venkatachala is a homonym 

of Schizosporis /aevigatus Stanley and should be replaced. 

Van Geel (1976) identified Holocene specimens that 

are morphologically identical with the Tullock fossils as 

algal cysts, more precisely as zygospores or aplanospores of 

the modem zygnemataceous chlorophyte alga Spirogyra. 

Rich and others (1982) assigned identical forms from 

Holocene peats to Ovoidites Potonie ex Krutzsch and 

elucidated their paleoecological significance. On the basis 

of their observations and the identification by Van Geel, 

Rich and others concluded that these fossils are indicators of 

freshwater marshes. They noted that identical forms have 

been reported from rocks as old as Cretaceous. Despite their 

value in paleoecological interpretation, considerable 

taxonomic and nomenclatural confusion centers on these 

fossils and similar forms that have been classified with 

them. These problems are briefly reviewed here to clarify 

the nomenclature applied to the Tullock specimens. 

The name Ovoidite s was proposed by Potonie (1951) 

for specimens from the Eocene of Germany; the genus was 

validated by Krutzsch (1959), who redescribed it and 

designated a type species, Ovoidites ligneolus (Potonie). In 

their descriptions, both Potonie and Krutzsch emphasized 

the general form of the fossils and their tendency to split 

into two equal halves. Neither author specified the structure 

or sculpture of the cyst wall. Cookson and Dettmann ( 1959) 

described the genus Schizosporis for certain fossils from the 

Upper Cretaceous of Australia that also tend to split into 

Palynostratigraphy, Tullock Member of Fort Union Formation, Montana and Wyoming Fll 
equal or subequal, discoidal halves but that have complexly 

structured, multilayered walls. The type species of Schizosporis is especially distinctive in having a robustly reticulate 

wall, and it differs markedly from the fossils we discuss 

here. Their species Schizosporis parvus and S. spriggi bear 

a general resemblance to the Tullock specimens and those 

from the Holocene deposits mentioned above, in form and 

in having a psilate wall, but they were described as having 

thick, multilayered walls. Potonie (1966) redescribed both 

Ovoidites and Schizosporis and reillustrated them using line 

drawings that make them appear more different from one 

another than is apparent from his redescriptions, both of 

which again emphasize reticulate walls. 

A resolution of the confusion was provided by Pierce 

(1976), who redescribed Schizosporis reticulatus and 

emended the genus Schizosporis to include forms with 

complex, reticulate walls that are almost multicellular in 

appearance, and who proposed the genus Schi:ophacus. 

Schizophacus includes lenticular forms that split along an 

equatorial suture and that have psilate walls or walls 

sculptured with patterns in low relief. The Tullock 

specimens illustrated here fall within the circumscription of 

Schizophacus. The specimens illustrated and discussed by 

Rich and others (1982) also are clearly referable to 

Schizophacus; the genus Ovoidites has uncertain 

nomenclatural status. 

Schizophacus laevigatus (Stanley) n. comb. closely 

resembles "spore type C" of Van Geel (1976, pl. 1, figs. 

5-8), which was identified as a cyst produced by a species 

of the modem genus Spirogyra. In the Tullock Member, S. 

laevigatus was present in 13 samples studied. Its occurrence 

is not restricted by lithology. It was most abundant in 

sample D6937-K, a carbonaceous shale just below a coal 

bed at the East Beav~r Creek locality, where it is part of an 

assemblage notable for its abundance of algal cysts and 

interpreted to represent a freshwater marsh environment that 

preceded development of a peat-forming mire. 

Schizophacus sp. 

Plate I, figure 2 

Samples from the Tullock Member yielded a second 

species referable to Schizophacus, which we designate 

Schizophacus sp. These specimens resemble S. laevigatus 

(Stanley) n. comb. in all respects except that the wall is 

characterized by subtle sculpture consisting of low ridges 

that form a pattern suggestive of a weakly developed 

reticulum. Van Geel (1976, pl. 1, fig. 11) illustrated a 

closely similar specimen he designated "spore type D" and 

identified as a zygospore or aplanospore of a species of the 

modern genus Spirogyra. Rich and others (1982, pl. 1, figs. 

6, 7) illustrated closely similar specimens from Holocene 

freshwater peats deposits in the Okefenokee Swamp, 

Georgia. They interpreted the sculpture pattern to be a 

wrinkled perispore. Tullock specimens have a single wall 

F12 Evolution of Sedimentary Basins-Powder River Basin 

layer and no evidence of a separate perispore. Rich and 

others assigned their specimens to the genus Ovoidites; refer 

to the nomenclatural history of Schizophacus and Ovoidites 

discussed above. 

Schizophacus sp. was present in nine Tullock samples 

studied; its occurrence is not restricted by lithology. It was 

present in two samples in which Schizophacus laevigatus 

was not present; thus in both morphology and occurrence 

these two species are distinct. Evidently both are cysts of 

algae related to the modem genus Spirogyra. In the Tullock, 

Schizophacus sp. is associated with cysts of other aquatic 

algae and pollen of marsh plants, as in sample D7000-B 

from the Dry Creek locality. 

Sigmopollis hispidus Hedlund 

Plate I, figure 3 

The algal cyst Sigmopollis hispidus was first reported 

by Hedlund (1965) and later by Wingate (1983) from the 

lacustrine Elko Shale (Eocene and Oligocene) in Nevada. It 

is spheroidal and has a unique sigmoidal line of dehiscence 

on one side. Specimens reported from lacustrine shales of 

the Green River Formation (Eocene) as Sigmopollis sp. by 

Nichols (1987) probably are conspecific. Close morphologic similarity between these Tertiary fossils and Holocene 

specimens illustrated by Pals and others (1980, pl. 2, figs. 

128a-e) is evident. The evidence from ancient and submodem environments suggests that Sigmopollis hispidus is an 

indicator of freshwater aquatic environments. 

In the Tullock Member samples we studied, Sigmopollis hispidus was present only in D6937-K, the 

carbonaceous shale below coal bed C at the East Beaver 

Creek locality. This deposit is also characterized by other 

algal cysts in abundance. It evidently represented a local 

lacustrin~ environment that was succeeded by a peat mire. 

Sigmopollis sp. 

Plate I, figure 4 

Sigmopollis sp. closely resembles S. hispidus in 

morphology but lacks the spines that characterize the latter 

species. The close morphologic resemblance of the two 

palynomorphs, which differs from that known in spores or 

pollen of terrestrial plants, suggests that Sigmopollis sp., 

like S. hispidus, is the cyst of an aquatic alga. Both forms 

were recorded only from sample D6937-K in this study. 

Tetraporina spp. 

Plate I. figures 7, 8 

Tetraporina spp. from the Tullock Member includes 

quadrate to concavely quadrate forms that vary in size and 

have either smooth or lightly sculptured cyst walls. The 

corners have structures suggestive of dehiscence areas but 
no true apertures. The form genus Tetraporina includes 

fossil algal cysts of the kind illustrated by Van Geel (1976, 

pl. 1, figs. 1-3) and identified as zygospores of the modern 

zygnemataceous chlorophyte Mougeotia sp. cf. M. punctata. More than one species probably is represented by fossil 

specimens from the Tullock Member. 

The complicated nomenclatural history of the genus 

Tetraporina was reviewed in detail by Jansonius and Hills 

(1981 ). Authorship and typification finally have been 

established, but unfortunately the genus is still described as 

encompassing tetraporate pollen, although it now seems 

clear that specimens ~ppropriately referred to it actually are 

nonporate algal cysts. The specimens described by Van 

Geel (1976) were from the Holocene of the Netherlands. 

The genus Tetraporina is based on specimens originally 

described from the lower Carboniferous of Russia. Thus, 

these algal cysts, which are characteristic of freshwater 

environments, are from an ancient Jineage. Jarzen (1979) 

illustrated many specimens referable to Tetraporina from 

the Ravenscrag Formation in Saskatchewan, which is in part 

con·elative with the Tullock Member of the Fort Union 

Formation. 

Tullock specimens of Tetraporina spp. were found in 

several samples of coal and carbonaceous shale, and in one 

mudstone sample. In the Tullock, Tetraporina spp. 

generally is present with other algal cysts, especially 

Schizophacus spp. 

Algal cyst type 1 

Plat<: 1, figure 5 

Palynomorphs assigned to the informal taxon "algal 

cyst type 1" in this study are small (diameter about 25 Jlm), 

spheroidal, psilate forms that have a simple dehiscence 

mark along which they split. They differ from specimens 

here assigned to Sigmopollis sp. in slightly larger size and in 

having a straight rather than sigmoidal dehiscence mark. 

They are interpreted to be of algal origin because their 

morphology does not resemble that of spores or pollen of 

any known terrestrial plants. Their exact affinity is 

unknown. 

These cysts were present in only one sample, 

06937-K, a carbonaceous shale from the East Beaver Creek 

locality that was independently interpreted to be of lacustrine origin. They were fairly common in this sample. 

Algal cyst type 2 

Plate I, figure 6 

Palynomorphs assigned to the informal taxon "algal 

cyst type 2" in this study are small (diameter about 20 Jlm), 

spheroidal, echinate forms that have a simple dehiscence 

mark along which they split. They resemble algal cyst type 

1 except in being densely covered with tiny, slender spines, 

and they resemble Sigmopollis hispidus except in having a 

straight rather than sigmoidal dehiscence mark. Like algal 

cyst type 1, they are assumed to be of algal origin because 

their morphology is unlike that of any known pollen or 

spores. 

Specimens of this morphology were present in four 

samples from the Tullock Member, in coal, carbonaceous 

shale, and mudstone. Specimens were most abundant in the 

lacustrine carbonaceous shale sample 06937-K from the 

East Beaver Creek locality. 

Alete Spores 

lncertae sedis type 1 

Plate 1, figures 9,10 

Palynomorphs designated "incertae sedis type 1" in 

this study are small (diameter 20-30 Jlm), inaperturate, 

spheroidal, coarsely reticulate forms. About one-third of the 

diameter is accounted for by the reticulum, which has high, 

thin muri and large, homobrochate lumina. Although 

reticulate sculpture is common among angiosperm pollen 

and also characterizes some kinds of pteridophyte spores, 

we know of no pollen or pteridophyte spores that are both 

inaperturate and reticulate. These fossils may be bryophyte 

spores. Spores of the modem bryophyte genus Fossomhronia illustrated by Erdtman (1957) have similar sculpture and 

obscure apertures, although they differ from the fossils in 

size and shape. 

Incertae sedis type 1 was present in five Tullock 

samples, including all the non-coal rock types studied. The 

possibility that this palynomorph is of freshwater algal 

origin is suggested by the observation that it is present in 

assemblages that include the water fern Azolla cretacea and, 

in some samples, algal cysts of the genera Schizophacus and 

T etraporina. 

Monolete Spores 

Laevigatosporites sp. L 

Plate 1, figures 11-14 

Psilate, monolete spores referable to the form genus 

Laevigatosporites are among the most common fossils in 

the Tullock Member. Spores of this morphology were 

present in all samples studied, and they were especially 

common in some. As a group, they range in size from 25 to 

60 Jlm; they exhibit no other morphologic variation that 

would permit recognition of individual botanical species 

that may be represented. 

Size/frequency distribution counts were made on two 

samples in which these spores were especially common: 

06937-0 and 07411-C, both of which are coals. In 

Palynostratigraphy, Tullock Member of Fort Union Formation, Montana and Wyoming F13 
D6937-D the size range is 25-58 Jlm and the modal size 34 

Jlm, although many are of larger size (225 specimens . 

· measured). In D7411-C, in which these spores are the 

numerical dominants, the range is 37-60 Jlm and the mode 50 

Jlm (100 specimens measured). Thus it is likely that two 

species can be distinguished on the basis of size. 

Laevigatosporites sp. L is the larger of two species of 

the genus distinguishable within the Tullock palynoflora. It 

is one of the most common species in the Tullock. As 

informally defined here, species L includes specimens from 

40 to 60 Jlm long; most are about 50 Jlm long. 

Laevigatosporites sp. L was present in all rock types 

and in almost all samples. It is the numerically dominant 

species in sample D7411-C. Patterns of occurrence and 

relative abundance show that this species is distinct from 

Laevigatosporites sp. S, although these two species differ 

only in size. Laevigatosporites sp. L was produced by 

polypodiaceous ferns that were major components of Tullock plant communities, especially in mire environments. 

Laevigatosporites sp. S 

Plate 2, figures 1-5 

Laevigatosporites sp. S is the smaller of two species 

of the genus present in the Tullock palynoflora. As here 

informally defined, species S includes specimens from 25 to 

40 Jlm long; most are about 35 Jlm long. Wilson and 

Webster (1946) described two species of Laevigatosporites, 

L. ovatus and L. gracilis, that differed in size and 

proportions, the former being larger and more rounded in 

outline than the latter. All of their specimens are within the 

size range of La·evigatosporites sp. S; we observed no 

consistent vanat10n in proportions among Tullock 

specimens of the genus other than those attributable to 

orientation and compression. 

This species was present in all rock types and in 

almost every sample. Laevigatosporites sp. S was produced 

by polypodiaceous ferns that were major components of 

Tullock plant communities, especially in peat-forming 

mires. 

Reticuloidosporites pseudomurii Elsik 

Plate 2, figures 6, 7 

Reticuloidosporites pseudomurii includes monolete 

spores that have low, irregular verrucae that tend form a 

poorly developed reticulate pattern. The distinctive 

sculpture serves to distinguish these spores from the 

otherwise similar Laevigatosporites spp. 

The relative abundance of R. pseudomurii in the 

Tullock is generally less than that of the species of Laevigatosporites, although it was present in 23 of the 30 samples 

studied in detail and it was the dominant species in sample 

D7299-0, one horizon within the coal bed at the Sussex 

locality. Distribution data published by Leffingwell (1971, 

F14 Evolution of Sedimentary Basins-Powder River Basin 

pls. 1, 2) show that Reticuloidosporites pseudomurii is 

relatively more abundant in the Tullock than in the 

underlying Cretaceous or in the overlying members of the 

Fort Union Formation. 

Trilete Spores 

Azolla cretacea Stanley 

Plate 2, figures 8-10 

Azolla cretacea is a species of heterosporous aquatic 

fern represented in the Tullock Member by microspores, 

which are small, circular in outline, and trilete, and by 

massulae, which are large, irregularly shaped bodies 

characterized by distinctive, anchor-shaped glochidia. 

Isolated glochidia may be encountered in preparations. 

This species was first described from the Hell Creek 

Formation and the Ludlow Member 9f the Fort Union 

Formation in South Dakota, on the basis of massulae 

(Stanley, 1965). Leffingwell (1970, pl. 4, fig. 1) identified 

microspores of Azolla cretacea in the Lance Formation and 

Tullock Member of the Fort Union in Wyoming. The 

significance of this species as an indicator of lacustrine 

environments in the Fort Union was first recognized by 

Tschudy (1961). 

In our study, Azolla cretacea was recorded in six 

samples, all from the lower part of the Tullock Member. 

This pattern of occurrence agrees with that shown by 

Leffingwell (1970, pls. 1, 2). A. cretacea tended to be 

present in assemblages that also include the aquatic algae 

Schizophacus and Tetraporina. 

Cicatricosisporites spp. 

Plate 2. figure 12 

This taxon includes one or more species of striate or 

cicatricose trilete spores; no attempt was made to identify 

individual species because so few of these spores were 

encountered. As shown by their distinctive sculpture, they 

were produced by ferns of the family Schizaeaceae. They 

were recorded as relatively rare specimens in six samples 

and were somewhat more common in the northern part of 

the basin than in the southern part. Ferns producing these 

spores probably were components of the regional flora and 

were not associated with any particular plant community. 

Cyathidites diaphana (Wilson & Webster) n. comb. 

Plate 3. figures 3-5 

Basionym: Deltoidospora diaphana Wilson and Webster, 1946, p. 273, 

fig. 3. 

Dettmann (1963) clarified the distinctions between 

the closely similar genera of triangular, psilate trilete spores 

Cyathidites and Deltoidospora. Cyathidites includes those 
having concave sides (and rounded apices); Deltoidospora 

includes those having straight sides (and sharper apices). 

Spores conforming to the morphology of Cyathidites, which 

are among the most abundant and commonly occurring in 

the Tullock palynoflora, were first described by Wilson and 

Webster (1946) from a Fort Union coal in southwestern 

Montana but were assigned to Deltoidospora. Stanley 

(1965, p. 248) transferred Wilson and Webster's species to 

the obscure genus Cardioangulina, which, if it is not 

different in being trilobate in form and much larger, is 

synonymous with Cyathidites. Leffingwell (1970, pis. 1, 2) 

apparently assigned his Tullock specimens of Cyathidites 

diaphana to a group he designated "unornamented trilete 

spores." Norton and Hall (1969) assigned theirs to 

Cyathidites. 

Cyathidites diaphana was present in every sample 

except that from the uppermost part of the Tullock Member 

at the Cow Creek locality. This pattern of stratigraphic 

occurrence is consistent with that shown by Leffingwell 

(1970, pis. 1, 2) for "unornamented trilete spores" and 

indicates that Cyathidites diaphana is a characteristic 

species of the Tullock palynoflora. This species is especially 

abundant just above the Cretaceous-Tertiary boundary at the 

Sussex and Lance Creek 2 localities (see also discussion of 

the fern-spore abundance anomaly in Nichols and others, in 

1992). 

Ghoshispora bella (Kondinskaya) Srivastava 

Plate 2, figures 13, 14; plate 3, figures I, 2 

Ghoshispora bella encompasses ornately ornamented, acrolamellate, trilete spores that may have been 

produced by heterosporous aquatic ferns (see Tschudy, 

1961 ). If they are megaspores in the botanical sense, they 

are unusually small and are recovered in the same 

preparations as· other palynomorphs; Tullock specimens are 

from 45 to 65 j..lm in diameter, excluding acrolamellae. The 

sculpture is coarsely echinate, and the echinae have ribs 

radiating from their bases that tend to form a reticulate 

pattern by connecting adjacent echinae. Specimens are 

common in the Campanian and Maastrichtian of the Rocky 

Mountain region, and the synonymous species Styx minor 

was regarded as characteristic of the Upper Cretaceous of 

Montana by Norton and Hall (1967). Their occurrence, 

however, is controlled by depositional environment as well 

as stratigraphic age. The nomenclatural history of this 

species has be~n complicated by competing taxonomic 

concepts discussed below. 

Srivastava (1967) described similar large, ornate 

spores from the Maastrichtian of Alberta as species of a new 

genus, Ghoshispora. His description emphasizes presence 

of an easily detached perine and makes no mention of the 

acrolamellae, the leaflike extensions of the laesurae. 

Specimens conspecific with ours from the Tullock Member 

were described from the Hell Creek Formation in Montana 

as a new genus and species, Styx minor, by Norton and Hall 

(1967), who also made no mention of acrolamellae. They · 

also described a larger but otherwise similar species, S. 

major, from the same deposits, and mixed up the 

illustrations of the type specimens of the two species 

(Norton and Hall, 1969, p. 24 ); correctly labeled specimens 

were reillustrated by them in their 1969 paper. That same 

year, Srivastava and Binda ( 1969) described similar 

specimens from the Upper Cretaceous of Alberta and 

Saskatchewan as species of Balmeisporites. They did not 

mention species of either Ghoshispora or Styx in that report, 

but they did assign some of their Canadian specimens to 

Balmeisporites bel/us Kondinskaya, a species originally 

described from the Upper Cretaceous and lower Paleocene 

of Siberia. 

Shortly thereafter, Srivastava (1971) decided that 

Norton and Hall's species Styx minor from Montana was 

synonymous with Balmeisporites bel/us from Siberia, but 

that the species did not belong in the genus Balmeisporites. 

He therefore reassigned both Norton and Hall's and Kondinskaya's specimens to a new nomenclatural combination, 

Styx bella (Kondinskaya) Srivastava. He noted that the size 

range within this species was great, the diameter of the 

spores ranging from 50 to 200 j..lm not including acrolamellae. Bergad (1973) analyzed the· taxonomic and 

nomenclatural problems associated with spores of this 

morphology and concluded that Styx minor Norton and Hall 

and Styx bella of Srivastava were distinct from Balmeisporites bel/us Kondinskaya and that Styx minor was instead 

synonymous with B. /ongirimosus Kondinskaya, another 

Siberian species. Bergad also suggested that Srivastava's 

genus Ghoshispora was based on a poorly preserved 

specimen of Balmeisporites similar to B. longirimosus, 

implying synonymy of Balmeisporites and Ghoshispora. 

Despite the confusion that abounded over the correct 

name for these distinctive spores in the early 1970's, 

Leffingwell (1970) assigned specimens that he found in the 

basal part of the Tullock Member and in the Lance 

Formation in Wyoming (which are conspecific with ours 

from the Tullock) to Srivastava's genus Ghoshispora, and 

B.D. Tschudy (1973) assigned similar specimens from the 

Campanian of Montana to Ghoshispora. 

Most recently, Srivastava ( 1978) redescribed and 

emended Ghoshispora, placing emphasis on the acrolamellae. He also stated that it is indeed a megaspore in the 

botanical sense, despite its being less than 200 j..lm in 

diameter (the arbitrary minimum size of megaspores in the 

morphologic sense). He reversed his earlier position on the 

status of the genus Styx and asserted that it is synonymous 

with Ghoshispora and reasserted that Balmeisporites is a 

separate genus, despite Berg ad's (1973) opinion to the 

contrary. If indeed Balmeisporites is a separate genus, the 

name Ghoshispora has priority for specimens like ours from 

the Powder River Basin. However, it still is not entirely 

clear that the specimens from Montana and Wyoming are 

Palynostratigraphy, Tullock Member of Fort Union Formation, Montana and Wyoming F15 
conspecific with the Siberian species, G. bella. Perhaps the 

name for the Tullock specimens should be Ghoshispora 

minor, which would be a new combination. In the absence 

of Siberian specimens with which to compare whh ours, we 

defer to Srivastava's latest decision and apply the name 

Ghoshispora bella to our specimens from the Tullock 

Member. 

In our study, Ghoshispora bella was found in four 

samples from the lower part of the Tullock Member in the 

southern part of the basin. As mentioned above, Leffingwell 

(1971) found specimens, which he also assigned to Ghoshispora, in the Tullock as well as in the Lance. Our specimens 

were present in assemblages that include freshwater algal 

cysts. They were unusually common in sample D71 00-C, 

carbonaceous shale from locality Lance Creek 1, which also 

yielded massulae of the heterosporous aquatic fern Azolla 

cretacea. 

Gleicheniidites sp. cf. Gleichenia triangula Stanley 

Plate 3, figures 6-8 

Spores assigned to Gleicheniidites sp. in this study 

are trilete, triangular with narrowly rounded apices, psilate, 

and have well-developed thickenings of the sporoderm in 

the interapical areas; they are about 25 J.Lm in diameter. 

They fall within the circumscription of the genus Gleicheniidites. They closely resemble specimens described by 

Stanley (1965) as Gleichenia triangula; however, Stanley's 

species, which he assigned to a modem genus, was recorded 

from a single sample from the Cretaceous Hell Creek 

Formation and not at all from the Fort Union Formation. 

Specimens we compare with his were present in two-thirds 

of the Tullock samples we studied in detail, in all rock 

types. Leffingwell (1970) also reported Gleicheniidites 

from the Fort Union but did not describe or illustrate his 

specimens. Norton and Hall (1969) apparently referred 

similar specimens to the much too broadly circumscribed 

species G. senonicus. 

Osmundacidites sp. 

Plate 2, figure II 

Osmundacidites encompasses circular trilete spores 

that have granulate sculpture and is thus distinguished from 

Baculatisporites and Foraminisporis, both of which are 

characterized by more robust baculate and clavate sculpture. 

Spores referable to Osmundacidites were first reported from 

the Tullock Member by Leffingwell ( 1970). 

Our specimens from the Tullock Member were 

present in low relative abundance in eight samples 

representing all rock types studied. They tended to be more 

common in coal and carbonaceous shale than elsewhere. 

F16 Evolution of Sedimentary Basins-Powder River Basin 

Stereisporites spp. 

Plate 3, figures 12-15: plate 4, figures 1-4 

Stereisporites includes spores referable to the bryophyte family Sphagnaceae-sphagnum moss. All are trilete 

and have thickened walls, especially at the equator. Among 

Tullock specimens, some are simple in form but others 

exhibit various sculpture, especially thickenings of the 

sporoderm at the distal pole, triradiate proximal thickenings, 

proximal interradial thickenings, and small, evenly 

distributed verrucae. Several species could be distinguished 

on the basis of these variations, as was done for European 

species by Krutzsch (1963). No species-level distinctions 

were attempted for Tullock specimens because the paleoecologic significance of these spores, as indicators of bog 

environments, is the same at the genus level. 

Stanley (1965) reported three species of these spores, 

which he assigned to the modem genus Sphagnum. They 

include Sphagnum antiquasporites, the species described by 

Wilson and Wester (1946) from the Fort Union Formation. 

They also include two other species that are fundamentally 

the same at the genus level and belong in Stereisporites, but 

that Stanley assigned to Cingulatisporites and suggested 

were spores of Selaginellaceae, a suggestion unsubstantiated on the basis of morphology. Norton and Hall (1969), 

following Stanley (1965), listed species of both genera. 

Leffingwell (1970), recogmzmg the morphologic 

uniformity of all these species at the level of genus, listed 

them as the "Stereisporites-Cingulatisporites complex." 

In this study, spores of Stereisporites spp. were found 

in 11 samples. They were especially common in some coal 

samples but were nowhere dominant; they were not 

restricted in occurrence by lithology. From these 

observations it is apparent that plants that produced spores 

of Stereisporites spp. were present in many wetland 

depositional environments of the Tullock, but that no 

Tullock coal developed from a sphagnum bog. 

Toroisporis major (Pflug) Stanley 

Plate 3, figures 9-11 

Spores identified as Toroisporis major in this study 

closely resemble those described by Stanley (1965). The 

characteristic tori on the proximal surface are not obvious 

on all specimens, and, except for those features, these spores 

fall within the circumscription of Deltoidospora. They 

differ from Cyathidites diaphana in having straight to 

convex sides and thicker exines. 

Toroisporis major was present in all rock types 

sampled in this study but in fewer than half the samples. It 

shows no clear pattern of association with a particular 

sedimentary facies or plant community. 
Zlivisporis novomexicanum (Anderson) Leffingwell 

Plate 4. figures 5-13 

Zlivisporis novomexicanum was described by 

Anderson (1960) from the uppermost Cretaceous and 

lowermost Tertiary of New Mexico. Anderson referred the 

species to the modern club-moss genus Lycopodium. The 

botanical affinity of these spores is uncertain, but they do 

not closely resemble spores of Lycopodium. They have 

greater resemblance to certain bryophyte spores illustrated 

by Erdtman (1957). Leffingwell (1970) transferred the 

species to Zlivisporis. Specimens from the Tullock Member 

that we assign to Zlivisporis novomexicanum exhibit 

considerable variation in morphology in detail, especially in 

the coarseness of the distal reticulum and presence or 

absence of proximal sculpture, and some are only 

questionably assigned to this species (plate 4, figs. 7, 8, 13). 

B. D. Tschudy (1973) assigned specimens of similar form 

and exhibiting a comparable range of morphologic ·detail to 

individual species of the genus Seductisporis. Zlivisporis 

differs from Seductisporis in having a more prominent 

trilete mark, a distinction that is unclear in some specimens. 

Zlivisporis novomexicanum was present in only five 

Tullock samples studied in detail. It was not present in coal 

samples and thus presumably was not produced by plants 

that inhabited peat-forming mires. 

Gymnosperm Pollen 

Araucariacites sp. 

Plate 5, figure I 

Pollen grains assigned to Araucariacites sp. in this 

study are spheroidal and inaperturate and have thin, scabrate 

to finely granulate exines. They presumably were produced 

by araucariaceous conifers, although the morphology of 

these pollen grains is not definitive. Brown (1962) reported 

distinctive araucarian leaves and cones from the lower part 

of the Fort Union Formation that tend to substantiate the 

identification of the pollen. 

Araucariacites sp. is a rare component of the Tullock 

palynoflora. It was recorded in only three samples, none of 

which were coals. 

Corollina sp. 

Plate 5, figures 2, 3 

A species of the predominantly pre-Tertiary genus 

Corollina(=Classopollis) is present in the Tullock palynoflora. The plants that produced this morphologically 

distinctive type of pollen were coniferopsids of the extinct 

order Voltziales, family Hirmerelliaceae (=Cheiro-

\ 

lepidaceae ), whose megafossil record extends from the 

Pennsylvanian to the Cretaceous (Taylor, 1981). The genus 

has not been reported previously from the Tullock Member, 

but D.T. Pocknall and D.J. Nichols (unpublished data) 

found similar, probably conspecific, specimens to have rare 

but consistent occurrence in the Tongue River Member of 

the Fort Union Formation. They considered their speqimens 

to be indigenous and not reworked from older rocks. 

Frederiksen (1980) reviewed records of Corollina (under 

the name Classopollis) from the Atlantic and Gulf Co11stal 

plains and concluded that the genus ranges at least into the 

Midwayan (lower Paleocene) in that region. 

In this study, we recorded Corollina sp. in rare 

abundance in one-third of the samples, in all rock types. 

These records of Corollina pollen from the Powder River 

Basin are evidence that the Voltziales survived into the 

early Tertiary in the Rocky Mountain region. 

Cycadopites scabratus Stanley 

Plate 5, figure 4 

Cycadopites scabratus is monosulcate, with the sulcus tending to be open at the extremities, and has a scabrate 

exine. Specimens are similar in general appearance to 'pollen 

of Arecipites and may be confused with them. 

Cycadopites scabratus was first described from the 

Cannonball Member of the Fort Union Formation in: South 

Dakota by Stanley (1965) and was recorded from the 

Tullock Member in Montana by Norton and Hall (1969). 

Leffingwell ( 1970) reported Cycadopites follicularis but not 

C. scabratus from the Tullock in Wyoming. The former 

species diffe~s from C. scabratus in being larger and paving 

a psilate exin~. Cycadopites scabratus was present iri about 

half of the Tti,llock samples we studied in detail, in all rock 

types. 

Pityosporite~ spp. 

Plate 5, figures 7-ll; plate 6, fig pres l, 2 

In this study, fossil bisaccate conifer pollen 

resembling that produced by extant species of pine and 

spruce is assigned to the form genus Pityosporites. The 

breadth of the sacci of these specimens is about equal to the 

depth of the corpus (terminology of Erdtman, 1957): More 

than one and perhaps several species are represented and 

might be distinguished by size or other criteria, but no 

attempt was made to distinguish species in this study. 

Stanley (1965) assigned pollen of this morphology to the 

modem genera Picea and Pinus. Norton and Hall (1969) 

assigned them to the form genera Abietineaepollenites, 

Pinuspollenites, and Cedripites. Leffingwell (1970) 

assigned them to his "Podocarpaceae-Pinaceae complex." 

Palynostratigraphy, Tullock Member of Fort Union Formation, Montana and Wyoming F17 
These fossils are among the most commonly 

occurring in the Tullock palynoflora in that they were found 

in all but three samples studied, although their relative 

abundance in individual assemblages is not great. They 

were most abundant in sample 07299-R, a carbonaceous 

shale from the Sussex locality, in which they amounted to 

about 40 percent of the assemblage. In most assemblages 

where they were present, they amounted to only a few 

percent. Modem conifers of the pine family produce 

prodigious numbers of pollen grains that tend to dominate 

palynological assemblages collected from the vicinity of the 

trees. On the basis of their relatively low abundance but 

consistent occurrence, Pityosporites spp. from the Tullock 

are interpreted to represent trees growing some distance 

from the depositional area, probably in highlands to the 

west. This interpretation is· consistent with the observation 

of Brown (1962) that no foliage, seeds, or wood attributable 

to pine is known from Paleocene strata in the Rocky 

Mountain region. We conclude that because of its common 

occurrence in Tullock samples, pollen of Pityosporites spp. 

is characteristic of the Tullock palynoflora, even though the 

plants that produced this pollen were rare or absent in 

Tullock depositional environments. 

Podocarpidites maximus (Stanley) Norton & Hall 

Plate 6, figure 3 

Bisaccate pollen in which the saccus breadth greatly 

exceeds corpus depth are assigned to Podocarpidites. Tullock specimens are virtually identical with those described 

by Stanley ( 1965) from the Cannonball Member of the Fort 

Union Formation as Podocarpus maximus. Norton and Hall 

(1969) transferred Stanley's species to Podocarpidites, 

although they accepted his suggestion that the fossils 

represented a species of the modem genus Podocarpus. 

Leffingwell (1970) included pollen of this morphology in 

his "Podocarpaceae-Pinaceae complex." On the basis of 

critical details of pollen morphology, D.T. Pocknall and 

D.J. Nichols (unpublished data) cast serious doubt on the 

inference that bisaccate pollen having large sacci are 

referable to Podocarpus, living species of which are native 

to the Southern Hemisphere. Brown (1962) reported no 

megafossils of Podocarpus from the Paleocene of the 

Rocky Mountain region. We regard Podocarpidites as a 

form genus having no implication of botanical affinity, and 

the species P. maximus as a fossil pinaceous species. 

Podocarpidites maximus was present as a relatively 

rare component of assemblages in seven Tullock samples. It 

was present in all rock types studied. Plants producing this 

pollen probably inhabited upland areas to the west of the 

Tullock depositional area. 

F18 Evolution of Sedimentary Basins-Powder River Basin 

Taxodiaceaepollenites hiatus (Potonie) Kremp 

Plate 5, figures 5, 6 

Pollen identified as Taxodiaceaepollenites hiatus 

includes specimens that are spheroidal and inaperturate and 

have scabrate exines; they generally are found split open 

and may exhibit poorly developed papillas. Pollen of this 

general morphology is characteristic of three closely related 

modem families of coniferous gymnosperms, the Taxodiaceae, Cupressaceae, and Taxaceae. Stanley (1965) 

tentatively assigned pollen of this morphology to Thuja, a 

modem genus of the Cupressaceae; such an assignment is 

unjustified in view of the lack of definitive morphologic 

characters. Norton and Hall (1970) applied the name Taxodiaceaepo/lenites hiatus but suggested affinity only with 

the Taxodiaceae. Leffingwell (1970) only referred this type 

of pollen to his "Taxodiaceae-Cupressaceae complex." 

Pocknall and Flores (1987), in discussing the role of this 

pollen in fossil plant communities of the Tongue River 

Member of the Fort Union Formation, concluded that it is 

related to the modem genus Glyptostrobus (Taxodiaceae) 

but recognized that pollen of Glyptostrobus may be 

indistinguishable from that of the modem genus Taxodium 

(Taxodiaceae). 

At present, both Glyptostrobus and Taxodium are 

inhabitants of swamps, and the abundance of this kind of 

pollen in Paleocene coals in the Rocky Mountain region 

suggests that fossil species of the Taxodiaceae were major 

contributors to the plant matter that formed the coals. This 

is true for coals of the Tongue River Member, but Taxodiaceaepo/lenites hiatus is relatively rare in Tullock coals; it 

follows that the Taxodiaceae contributed little to 

accumulation of coals of the Tullock Member. This species 

is more common in our samples of the Lebo Member of the 

Fort Union than in the Tullock. Relative abundance data of 

Leffingwell (1970, pl. 3) show that taxodiaceous pollen is 

rare in the lower part of the Tullock Member, more 

abundant upward toward the Lebo, and dominant in the 

'tongue River Member. In this study, T. hiatus pollen was 

present in little more than half the samples and, in most 

cases, is a rare component of assemblages. It was somewhat 

less common in coals than in clastic rocks. 

Angiosperm Pollen-Monosulcate 

Arecipites tenuiexinous Leffingwell 

Plate 6, figures 4-7 

Arecipites tenuiexinous includes monosulcate pollen 

having a thiri exine and finely reticulate sculpture. As in all 

species of Arecipites, the sulcus extends to the ends of the 

grain and is tapered at its extremities. As originally 

described by Leffingwell (1970), the lumina of the reticulum are about 0.5 j..lm in diameter. Some specimens we 
assign to this species have a finer reticulum and tend toward 

a sculpture pattern better described as microfoveolate. 

Leffingwell measured 10 specimens and determined their 

length to be from 25 to 30 f..Lm; the size range of 10 of our 

specimens is 30-33 f..Lm. Arecipites tenuiexinous differs 

from Arecipites reticulatus Anderson only in size; 

Anderson's species, which is from the Upper Cretaceous 

and lower Tertiary of New Mexico, was described as having 

a fine reticulum (lumina 0.5 f..Lm in diameter) and ranging 

from 18 to 23 f..Lm in length. The pollen morphology of these 

species indicates that they were produced by palms. Brown 

(1962) attributed leaves from the lower part of the Fort 

Union Formation to species of -the modem palm genus 

Saba/. 

Arecipites tenuiexinous originally was described from 

the Powder River Basin by Leffingwell (1970). It is present 

in both the Lance Formation and the Tullock Member, 

although Leffingwell did not report it from the upper part of 

the Tullock. It was absent from our samples of the upper 

part of the Tullock at the Cow Creek locality, but it was 

present in samples from the lower part of the Lebo Member 

collected about 2 km to the southwest. It is one of the most 

commonly occurring species in the Tullock palynoflora and 

was present in more than 80 percent of the samples we 

analyzed in detail. 

Liliacidites leei Anderson 

Plate 6, figure 8 

Liliacidites /eei is monosulcate and reticulate, but, as 

is characteristic of the genus Liliacidites, the reticulum 

varies in coarseness and generally is finer toward the ends 

of the grain. The diameter of lumina is from 1 to 1.5 f..Lm. 

The coarser and variable sculpture serves to distinguish this 

species from Arecipites tenuiexinous. Liliacidites leei 

differs from other species of the genus described by 

Leffingwell (1970) from the Upper Cretaceous of the 

Powder River Basin in having low, simplibaculate muri. 

Botanical affinity is with the Monocotyledonae and 

probably with the Liliaceae. 

This species was originally described from uppermost 

Cretaceous and lower Tertiary rocks in New Mexico 

(Anderson, 1960) and has not been reported previously in 

the Powder River Basin. We recorded it only in the basal 

pa1t of Tullock Member at the Sussex locality. 

Angiosperm Pollen-Tricolpate 

Discoidites parvistriatus (Norton) n. comb. 

Plate 6. figures 9-11 

Basionym: Tricolpites parvistriatus Norton in Norton and Hall, 1967. p. 

105, pl. 1, fig. E. 

Norton (in Norton and Hall, 1967) described "Tricolpites" parvistriatus as being circular in polar view, having 

very short colpi, and having an ektexine composed of 

closely spaced baculae that present a vague striate sculpture. 

The striate pattern of ·sculpture he referred to is not evident 

in the holotype specimen (Norton and Hall, 1967, pl. 1, fig. 

E, reillustrated in Norton and Hall, 1969, pl. 7, fig. 2) nor in 

specimens we found in our samples from the Powder River 

Basin. More important, the sculpture of none of these 

specimens is reticulate; thus the assignment of this species 

to the genus Tricolpites is inappropriate. The apertures, 

which extend no more than one-third of the distance toward 

the poles, are best described as brevicolpate, and brevicolpate apertures are not characteristic of Tricolpites. Thus, 

this species requires redescription and reassignment. 

Redescription.-Triaperturate pollen, brevi col pate; 

colpi simple and lacking margines, equatorial, extending 

about one-third of distance to poles; amb circular to broadly 

rounded interangular; form oblate to peroblate, 20-25 f..Lm in 

diameter; exine tectate, columellate, 1-1.5 f..Lm thick, ektexine thicker than endexine, endexine tending to thicken at the 

colpi; columellae generally evenly arranged, not tending to 

form reticulate or striate patterns beneath the tectum; tectum 

nonperforate, ends of baculae protruding through tectum to 

form supratectal scabrate to granulate sculpture. 

The genus Discoidites was proposed by Muller 

(1968). It encompasses tricolpate, disc-shaped pollen 

having short col pi and tectate exines in which the tops of the 

columellae project through the tectum to form a finely 

verrucate pattern. This genus differs from Tiliaepollenites 

Potonie & Venitz in having colpate apertures and in lacking 

vestibulate pores. Discoidites borneensis Muller, type 

species of the genus, shows darkened (presumably 

thickened) areas of exine surrounding the apertures, but 

these features (costae pori?) are not mentioned in the 

generic description and may be considered species-level 

characters. Discoidites parvistriatus differs from D. borneensis in smaller size, narrower col pi, endexinal thickenings 

near the apertures that are only weakly developed to absent, 

and finer sculpture. Muller (1968) suggested tiliaceous 

affinity for D. borneensis; we regard Discoidites as a form 

genus and do not necessarily imply such botanical affinity 

for D. parvistriatus. Two aspects of the morphology of D. 

parvistriatus, however, are suggestive of pollen of modem 

Tiliaceae: exine structure (including a weak tendency to 

development of costae pori) and tendency to have an 

interangular amb. Possibly this Late Cretaceous and early 

Tertiary species is an early ancestral member of the lineage 

of the Tiliaceae. 

Norton and Hall (1967, 1969) reported "Tricolpites" 

parvistriatus as being restricted to the Hell Creek 

Formation. The species is more common in the uppermost 

Cretaceous (Hell Creek and Lance Formations and 

equivalents) than in the lowermost Tertiary in the region, 

but it is present in the lower part of the Fort Union 

Formation and equivalents (Leffingwell, 1970; Jerzykiewicz and Sweet, 1986; Lerbekmo and others, 1987; 

Palynostratigraphy, Tullock Member of Fort Union Formation, Montana and Wyoming F19 
Johnson and others, 1989). In our study, we found 

Discoidites parvistriatus in samples of the lower part of the 

· Tullock Member from a few localities in Montana and 

Wyoming. It was present but rare in Tullock coal, carbonaceous shale, and mudstone. 

Fraxinoipollenites variabilis Stanley 

Plate 6, figures 12-16 

The taxonomic history of this species is confused 

because Stanley (1965)apparently included more than one 

morphotype when he described it. Specimens assigned to 

this species by Leffingwell (1970) resemble Stanley's 

paratypes but depart somewhat from the morphology of the 

holotype. Specimens from the Tullock Member that we 

assign to Fraxinoipollenites variabilis are finely reticulate 

and have long colpi that closely approach the poles. The 

long colpi serve to distinguish this species from other 

reticulate tricolpate pollen. Specimens of F. variabilis were 

present in low numbers in all rock types sampled. They 

were unusually common in sample D7137-I, mudstone 

from the basal Tullock at the Lance Creek locality. 

Quercoidites spissus Leffingwell 

Plate 6, figures 17, 18 

Quercoidites spissus includes tricolpate pollen having 

granulate sculpture. Leffingwell (1970), who described the 

species, reported it from both the Lance and Fort Union 

Formations in the Powder River Basin. In our samples, 

specimens were found only in Tullock coal samples from 

the Montana part of the basin. 

Retitrescolpites anguloluminosus (Anderson) Frederiksen 

Plate 6, figures 19-21 

Retitrescolpites anguloluminosus is distinguished 

from other species of reticulate tricolpate pollen in the 

Tullock palynoflora by its coarsely reticulate sculpture. The 

lumina of the reticulum are 2-3 Jlm in diameter. It was 

originally described as a species of the genus Tricolpites by 

Anderson (1960), but Frederiksen (1979) transferred it to 

Retitrescolpites, which encompasses tricolpate pollen 

having coarsely reticulate rather than finely reticulate tricolpate sculpture. Norton and Hall (1969) and Leffingwell 

(1970) considered coarsely reticulate tricolpate pollen 

described by Stanley (1965) as Tricolpites bathyreticulatus 

to be a separate species, but we consider Stanley's species 

to be synonymous with R. anguloluminosus. 

This species was present in about one-third of our 

Tullock samples from Wyoming localities, but we did not 

observe it in any sample from Montana. Norton and Hall's 

(1969) records of this species from the Tullock and Lebo in 

F20 Evolution of Sedimentary Basins-Powder River Basin 

Montana indicate, however, that it is not geographically 

restricted. It was present in coal and all fine-grained clastic 

rock types sampled in the southern part of the Powder River 

Basin. The previously published records of occurrence of 

this species cited here are all from lower Tertiary rocks, but 

the species may be present also in the uppermost Cretaceous 

of the region and not restricted to the Tullock and 

equivalents. 

Rousea spp. 

Plate 7, figures 1, 2 

Rousea includes reticulate tricolpate pollen in which 

the reticulum varies in coarseness, becoming finer toward 

the poles and the margins of the col pi. Individual specimens 

from 25 to 45 Jlm in size were recorded in four samples in 

this study. These species, grouped here in a single genuslevel taxon, are extremely rare components of the Tullock 

palynoflora. 

Striatopollis tectatus Leffingwell 

Plate 7, figures 3, 4 

Striatopollis tectatus is distinctive in having finely 

striate sculpture. Striate tricolpate pollen is produced by 

some modem species of the family Aceraceae (maples), 

suggesting this affinity for the Tullock fossils. Striatopollis 

tectatus was present in about half of our samples. This 

species is present also in underlying Cretaceous rocks in the 

Powder River Basin. 

Tricolpites hians Stanley 

Plate 7, figures 5-7 

In this study, small (about 25 Jlm in greatest 

dimension), finely reticulate (lumina 1 !J.m or less in 

diameter), tricolpate pollen was assigned to Tricolpites 

hians. Included are specimens that Leffingwell ( 1970) 

assigned to T. parvus Stanley. Specimens assigned to 

Tricolpites hians differ from those assigned here to the 

broader taxon Tricolpites spp. in having a very fine reticulum, although the distinction is difficult to make in some 

specimens. All specimens assigned to the genus Tricolpites 

in this study differ from those assigned to Retitrescolpites 

anguloluminosus in having much finer sculpture. Species 

assigned to Tricolpites differ from species of the genus 

Rousea in having evenly developed sculpture. Fraxinoipollenites variahilis has fine, evenly developed sculpture but 

longer colpi. 

Pollen referable to either Tricolpites hians or Tricolpites spp. is present in almost all Tullock samples examined 

in detail in our study. Similar or identical specimens are 

known to occur commonly in Upper Cretaceous and lower 

Tertiary rocks throughout the Rocky Mountain region. The 

botanical affinity of T. hians may be with the Platanaceae 
(sycamore family), but the morphology of the pollen is not 

distinctive enough for this to be certain. 

Tricolpites spp. 

Plate 7, figures 8-12 

Specimens assigned to Tricolpites spp. in this study 

probably include more than one species. All are tricolpate 

and reticulate and have a fine to medium reticulum (lumina 

about 1-2 jlm in diameter). Some are quite close to 

Tricolpites hians in morphology, but they form an apparent 

morphologic continuum with specimens that are more 

coarsely sculptured than T. hians. The specimens illustrated 

here exhibit the range in morphology. 

Pollen referable to Tricolpites spp. is present in 

almost ~ll Tullock samples. Their botanical affinity could be 

with the Platanaceae (sycamore family), but this is uncertain 

because the modern families Haloragaceae, Hamamelidaceae, Ranunculaceae, Salicaceae; and Trochodendraceae 

also include species that produce pollen having similar 

morphology. 

Angiosperm Pollen-Tricolporate 

Brevicolporites co/pella Anderson 

Plate 7, figures 13, 14 

Brevicolporites co/pella includes circular, oblate, 

brevitricolporate pollen having broad arci between apertures 

and scabrate exines. The species was originally described by 

Anderson (1960) from the lowermost Paleocene in the San 

Juan Basin of New Mexico. Subsequently it was reported by 

Jerzykiewicz and Sweet (1986) from the lower Paleocene of 

Alberta. It has not been reported previously from the 

Powder River Basin. It is a rare component of the Tullock 

palynoflora, but in this study it was recorded in coal, shale, 

and mudstone samples from the lower and middle parts of 

the Tullock Member. 

Kurtzipites circularis (Norton) Srivastava 

Plate 7, figures 15-17 

Kurtzipites circularis is tricolporate (brevicolpate) 

and has apertures located in distinctive projections at the 

equator. This species was originally described by Norton (in 

Norton and Hall, 1969) as a species of the genus Momipites, 

but clearly it has no relationship with or close resemblance 

to that genus. Norton's specimens were from the Hell Creek 

Formation and lower Fort Union equivalent in the Hell 

Creek area of Montana. Leffingwell (1970) described 

specimens that are identical with Norton's as a new species, 

K. simplex. Leffingwell's specimens were from the Lance 

Formation and Tullock Member of the Fort Union in the 

Lance Creek area of Wyoming. All these specimens are 

conspecific, and Kurtzipites circularis is their correct name. 

Srivastava (1981) transferred Norton's species to Kurtzipites and placed Leffingwell's species in synonymy with it. 

Kurtzipites circularis differs from K. trispissatus Anderson 

in lacking endexinal thickenings at the apertures. 

Leffingwell (1970) found specimens of Kurtzipites 

spp. to occur no higher stratigraphically than the lower part 

of the Tullock Member, but we found K. circular is to be the 

dominant species in the upper part of the Tullock at the Cow 

Creek locality. Kurt:ipites circularis was present in about 

two-thirds of the samples we examined in detail in our 

study. 

Kurtzipites trispissatus Anderson 

Plate 7, figures 18, 19 

Kurtzipites trispissatus was originally described by 

Anderson (1960) from the uppermost Cretaceous of New 

Mexico. He regarded it as triporate, but Leffingwell (1970) 

correctly redescribed it as tricolporate. Kurtzipites trispissatus closely resembles K. circularis and differs only in 

having pairs of prominent endexinal thickenings at the 

·apertures. Specimens are most commonly preserved in polar 

view. As noted by Srivastava (1981), Stanley (1965) 

described specimens of K. trispissatus preserved in 

equatorial view as Aenigmapollis polyformis; Srivastava 

placed Stanley's species in synonymy with K. trispissatus. 

Stanley (1965) neither described nor illustrated any 

other specimens that resemble species of Kurtzipites in his 

samples from South Dakota, although they are common in 

uppermost Cretaceous and lowermost Tertiary rocks in 

western North America. Norton and Hall (1969) reported K. 

trispissatus from the Hell Creek Formation in Montana, and 

Leffingwell (1970) reported it from the Lance Formation 

and the Tullock Member of the Fort Union in Wyoming. We 

found it to be present in all rock types, although not in all 

samples, in the lower and middle parts of the Tullock. 

Norton (in Norton and Hall, 1969) described another closely 

related species of Kurtzipites from the Hell Creek 

Formation, K. annulatus, in ' which the endexinal 

thickenings at each aperture form a ring instead of being in 

pairs. This same species was reported by Leffingwell (1970) 

from the Lance Formation and Tullock Member of the Fort 

Union as Kurtzipites sp. We did not distinguish K. annulatus from K. trispissatus in our samples, although some 

specimens we identified as the latter species could prove on 

closer inspection to be the former. 

As mentioned, previous records from the Powder 

River Basin indicate the upper limit of the range of 

Kurtzipites spp. to be within the Tullock Member. In our 

study we recorded K. circularis throughout the Tullock, 

including the uppermost part of the member in the southern 

part of the basin, and we recorded K. trispissatus in many 

samples from the lower and middle parts of the member in 

Palynostratigraphy, Tullock Member of Fort Union Formation, Montana and Wyoming F21 
both Wyoming and Montana. We did not find any species of 

Kurtzipites in the Lebo Member. On the basis of this pattern 

. of stratigraphic distribution, species of Kurtzipites can be 

considered as characteristic components of the Tullock 

palynoflora. On the basis of reports cited in the preceding 

discussions, species of this genus are present in lower 

Paleocene rocks from New Mexico to Alberta, Canada, and 

they should prove useful in regional correlation. 

Nyssapollenites spp. 

Plate 7, figures 20, 21 

In this report, all triangular, oblate, tricolporate pollen 

having reduced sculpture (including finely reticulate and 

granulate) was assigned to the taxon Nyssapollenites spp. 

Specimens conforming with this general description were 

recorded in about one-third of the samples studied in detail, 

in coal and fine-grained clastic rock types. No biostratigraphic or paleoenvironmental significance is 

attributed to this heterogeneous group. 

Rhoipites spp. 

Plate 7, figures 22-24 

We assigned all prolate, finely reticulate, tricolporate 

pollen from the Tullock Member to the taxon Rhoipites spp. 

Norton and Hall (1969) assigned similar specimens to 

several different species of the genus Tricolporopollenites. 

Our specimens are from 20 to 40 Jlm in polar diameter. 

They were recorded in about one-fourth of the samples 

studied in detail, in coal, carbonaceous shale, and shale. No 

biostratigraphic or paleoenvironmental significance is 

attributed to this heterogeneous group. 

Tilia vescipites Wodehouse 

Plate 8, figures I, 2 

Tilia vescipites includes oblate, brevicolporate pollen 

having very finely reticulate sculpture. Endexinal 

thickenings characteristic of modem pollen of the genus 

Tilia are present but not well developed, and it is difficult to 

ascertain if the pores are truly vestibulate. This species may 

represent an early ancestor in the lineage of the Tiliaceae 

(basswood family), but assignment of the fossil species to 

the modem genus probably is not supported by detailed 

consideration of pollen morphology. 

In this study a single specimen was recorded in 

carbonaceous shale from the Minnehaha Creek locality in 

Montana. Despite its rarity, it is noteworthy because it may 

be the earliest record of the tiliaceous lineage (but see also 

discussion of Discoidites parvistriatus). Nichols and Ott 

(1978) recorded Tilia vescipites from the middle Paleocene 

in the Wind River basin. The species was originally 

described by Wodehouse (1933) from the lower Eocene. 

f22 Evolution of Sedimentary Basins-Powder River Basin 

Angiosperm Pollen-Syncolporate 

Cupanieidites inaequalis Leffingwell 

Plate 8, figures 5, 6 

Cupanieidites inaequalis includes syncolporate 

pollen having polar islands at one or both poles and 

intectate, very finely reticulate exines. It differs from 

Syncolporites minimus in larger size and in having reticulate 

rather than granulate sculpture. The species was originally 

described by Leffingwell (1970) from the Lance and Fort 

Union Formations in the Powder River Basin. Similar 

specimens from the uppermost Cretaceous and lower Tertiary in New Mexico were assigned to Cupanieidites aff. C. 

major by Anderson (1960), and others from the Hell Creek 

and Tullock in Montana were assigned to C. major by 

Norton and Hall (1969). Leffingwell (1970) noted that C. 

major is larger and has more distinct pores than does C. 

inaequalis. 

In our study C. inaequalis was recorded in about 

one-third of the Tullock Member samples studied in detail. 

It was found in coal and all fine-grained clastic rock types. 

Syncolporites minimus Leffingwell 

Plate 8, figures 3, 4 

Syncolporites minimus includes small, granulate, syncolporate pollen. The species was originally described by 

Leffingwell (1970) from the Lance and Fort Union 

Formations in the Powder River Basin. It was subsequently 

reported by Jerzykiewicz and Sweet (1986) from the 

uppermost Cretaceous and lowermost Tertiary Coal spur 

Formation in Alberta and by Johnson and others (1989) 

from the lowermost Tertiary Ludlow Formation of the Fort 

Union Group in North Dakota. 

Syncolporites minimus (along with Triporopollenites 

plektosus) tends to dominate some assemblages just above 

the K-T boundary in the Coals pur Formation (Jerzykiewicz 

and Sweet, 1986). It is also abundant in samples just above 

the K-T boundary in North Dakota (Johnson and others, 

1989). In the Powder River Basin this species was present in 

about one-third of all samples from the Tullock Member 

examined in detail but never in high relative abundance. It 

was recorded in coal and all fine-grained clastic rock types. 

Angiosperm Pollen-Monoporate 

Pandaniidites typicus (Norton) Sweet 

Plate 8, figures 7-9 

Pandaniidites typicus is spheroidal to elliptical, 

monoporate, and echinate; the pore is annulate in most 

specimens. The exine is thin, and most specimens are 
randomly folded. Although the botanical affinity of this 

species has been questioned by Sweet (1986), who 

suggested it might be with the Lemnaceae (duckweed 

family), we follow Simpson (1961), Elsik (1968), Norton 

and Hall (1969), Leffingwell (1970), Muller (1981), and 

Jarzen (1983), who referred fossil pollen of this morphology 

to the Pandanaceae (pandans or screw-pines). Muller ( 1981) 

suggested that the specimens described by Elsik (1968) and 

Leffingwell (1970) may represent an extinct group of the 

Panclanaceae. 

Pollen ot this morphology was first described by 

Simpson (1961) from lower Tertiary deposits in Scotland, 

the. species Pandaniidites shiabensis (Simpson) Sweet. 

Elsik (1968) described closely similar specimens from the 

Paleocene of Texas. He named a new species, P. texus, 

which he distinguished from Simpson's species by placing 

emphasis on the pore being annulate. Elsik also attempted to 

transfer Simpson's species from the modem genus Pandanus to Pandaniidites, but he failed to clearly identify the 

basionym, as required by the International Code of 

Botanical Nomenclature, and his new combination is 

invalid; Sweet (1986) later made that transfer validly. 

Without reference to the previously described forms, 

Norton (in Norton and Hall, 1969) described closely similar 

specimens from the uppermost Cretaceous and lower Paleocene of Montana as a new genus and species, Spinamonoporites typicus. Leffingwell (1970) described specimens 

from the Lance and Fort Union Formations in the Powder 

River Basin as Pandaniidites radicus. He stated that thinner 

exine distinguished P. radicus from P. texus and P. shiabensis; he did not compare his specimens with Norton's. 

Sweet (1986) noted that differences of opinion had been 

expressed by the previous authors about presence or degree 

of development of an annulus surrounding the pore, wall 

thickness, and exine stratification, but that all of these 

authors had des.cribed closely similar if not conspecific taxa. 

He pointed out that Norton had provided the broadest 

circumscription, which would encompass all previously 

described species, and transferred Norton's species to the 

genus Pandaniidites. We follow Sweet's taxonomy and 

nomenclature, although not his suggested botanical affinity, 

for our Tullock specimens. 

Pandaniidites typicus was present in about half of our 

samples from the Tullock Member and was found in all rock 

types sampled. It was especially common in a sample of 

carbonaceous shale from the Buckskin Butte locality in 

Montana and in a sample of mudstone from the Lance Creek 

1 locality in Wyoming. 

Sparganiaceaepollenites sp. 

cf. Sparganium globites Wilson & Webster 

Plate 8, figures 10-12 

Specimens from the Tullock Member that we assign 

to Sparganiaceaepollenites sp. cf. Sparganium globites are 

spheroidal, monoporate, and reticulate. They resemble 

specimens from the Fort Union Formation in western· 

Montana described by Wilson and Webster (1946) as 

Sparganium globites, except that the pore is much smaller in 

diameter. The botanical affinity of . these specimens 

probably is with the Sparganiaceae (bur-reed family) or 

Typhaceae (cattail family). Modem species of both families 

are marsh plants. 

Specimens resembling Sparganiaceaepollenites sp. 

cf. Sparganium globites have not been reported previously 

frorp the Powder River Basin. They are rare in the Tullock 

Member and were found in only three samples: carbonaceous shale from the lower part of the Tullock at the 

Buckskin Butte and Minnehaha Creek localities in 

Montana, and shale from the upper part of the Tullock at the 

Cow Creek locality in Wyoming. 

Angiosperm Pollen-Triporate 

Momipites inaequalis Anderson 

Plate 8, figure 13 

Momipites inaequalis includes specimens of the 

distinctive and biostratigraphically important genus M omipites that lack modifications of exine structure at one pole. 

Like all species of the genus, M. inaequalis has atriate pores 

and a fine sculpture of widely spaced scabrae. Some 

specimens of this species are slightly unequally triangular. 

This species was originally described by Anderson 

(1960) from the lowermost Paleocene in the San Juan Basin, 

New Mexico, and it is also present in the lowermost 

Paleocene in the Raton Basin, New Mexico (Fleming, 

1990). Stanley (1965) described similar, probably at least in 

part conspecific, pollen from the lower Paleocene of South 

Dakota as Engelhardtia microfoveo/ata, but he 

misinterpreted the fine sculpture pattern as microfoveolate. 

Johnson and others (1989) reported M. inaequalis from the 

lowermost Paleocene in North Dakota. Norton and Hall 

(1969) stated that they found no specimens resembling 

Stanley's in their lower Paleocene material from eastern 

Montana. (They described two species they assigned to the 

genus Momipites, one or perhaps both of which belong in 

the genus Kurtzipites, which they apparently confused with 

Momipites, although the two genera have little in common 

morphologically.) Momipites inaequalis was reported 

previously in the Powder River Basin at the Sussex K-T 

boundary locality (Nichols and others, 1992). The botanical 

affinity of this species is with the Juglandaceae (walnut 

family). 

Momipites inaequalis was present in about one-third· 

of our samples of the Tullock Member, in coal and all 

fine-grained clastic rock types, although never in high 

relative abundance. It is present in the Tullock in Montana 

as well as in Wyoming but may be at the northern edge of 

its paleogeographic range in Montana. This species may be 

Palynostratigraphy, Tullock Member of Fort Union Formation, Montana and Wyoming F23 
regarded as characteristic of the lowermost Paleocene, 

although it also is present rarely in the uppermost 

Cretaceous, just below the K-T boundary (Johnson and 

others, 1989; Fleming, 1990; Nichols and others, 1992). 

Momipites leffingwellii Nichols & Ott 

Plate 8, figure 14 

Momipites /effingwellii is one of the species of 

Momipites that are characterized by modifications of exine 

structure at one pole. In M. leffingwellii the modification is 

a ring-shaped thinning of the exine surrounding the distal 

pole. This species is additionally distinguished by straight to 

concave sides. 

This species was originally described from the 

lowermost Paleocene of the Wind River Basin by Nichols 

and Ott (1978). Leffingwell (1970) described several more 

or less similar species from the Powder River Basin and 

placed them all in a new genus, Maceopolipo/lenites. 

Nichols (1973) placed that genus in synonymy with Momipites and transferred all of Leffingwell's species to Momipites. As noted by Nichols and Ott (1978), specimens 

previously reported from the Powder River Basin as 

Maceopolipollenites tenuipolus (Anderson) actually belong 

to Momipites /effingwellii, However, we also identified 

Anderson's species Momipites tenuipolus from the Tullock 

Member, so only some of the specimens reported by 

Leffingwell (1970) are referable to Momipites leffingwellii. 

The botanical affinity of this species is with the Juglandaceae (walnut family). 

Momipites leffingwellii is rare in the Tullock 

Member. In this study we found it in only four samples, all 

of which were from the middle or upper parts of the unit at 

the southern end of the basin. It was notably abundant in one 

sample of carbonaceous claystone from the Leverett Butte 

locality. We also recorded it from the Lebo Member in 

stratigraphic control samples from Wyoming and Montana; 

it was absent from our control samples from the Lance and 

Hell Creek Formations. 

Momipites tenuipolus Anderson 

Plate 8, figures 15, 16 

Momipites tenuipolus is similar toM. leffingwellii in 

having a circumpolar ring (or in some specimens, a circular 

spot) of thin exine at one pole, and it differs primarily in 

having convex sides. It differs from the characteristically 

middle Paleocene species M. anellus Nichols and Ott in 

being smaller and in having a less clearly developed 

circumpolar ring of thin exine and polar island of normally 

thickened exine. These distinctions are subtle but important 

to recognize because, as emphasized by Nichols and Ott 

( 1978), they are the basis of the biostratigraphic utility of 

species of the genus Momipites in the Paleocene of western 

North America. 

F24 Evolution of Sedimentary Basins-Powder River Basin 

Momipites tenuipolus was originally described by 

Anderson (1960) from the lower Paleocene of New Mexico. 

As noted above, this species was previously reported from 

the Powder River Basin by Leffingwell (1970). The 

botanical affinity of this species is with the Juglandaceae 

(walnut family). 

In our study, we found Momipites tenuipolus to be 

more common in the middle and upper parts of the Tullock 

Member than in the lower part~ a pattern of distribution also 

recorded by Leffingwell (1970, pl. 1 ). It was present in all 

rock types we sampled but was more common in clastic 

rocks than in coal. Leffingwell also recorded this species in 

the uppermost part of the Lance Formation; we did not 

observe it in our control samples from the Lance or Hell 

Creek Formations. 

Momipites waltmanensis Nichols & Ott 

Plate 8, figure 17 

Momipites waltmancnsis is another species of the 

genus that lacks modification of exine at the poles. It differs 

from M. inaequalis and M. wyomingensis in having concave 

sides. 

Momipites waltmanensis was originally described 

from the Wind River Basin (Nichols and Ott, 1978). A 

specimen illustrated by Stanley (1965, pl. 45, figs. 8-1 0) as 

Engelhardtia microfoveolata may be referable to Momipites 

waltmanensis. Momipites waltmanensis was previously 

reported from the Tongue River Member in the Powder 

River Basin by Pocknall (19R7). The botanical affinity of 

this species is with the Juglandaceae (walnut family). 

In our Tullock samples Momipites waltmanensis was 

present only in the middle and upper parts of the member. 

Based on our stratigraphic control samples, it is present also 

in the Lebo Member but absent from the Lance and Hell 

Creek Formations in the Powder River Basin. 

Momipites wyomingensis Nichols & Ott 

Plate 8, figure 18 

Momipites wyomingensis has convex sides and lacks 

modification of the exine at the poles. It differs from M. 

inaequalis in larger size and in being perfectly symmetrical, 

with all sides of equal length. 

Momipites wyonzingensis was originally described 

from the Paleocene of the Wind River Basin by Nichols and 

Ott (1978) and was previously reported in the Powder River 

Basin by Pocknall ( 1987). The botanical affinity of this 

species is with the Juglandaceae (walnut family). 

This species is rare in the Tullock Member in the 

Powder River Basin. It was present in only one of our 

samples from the middle part of the unit at the Leverett 

Butte locality. It was present also in our control samples 

from the Lebo Member. 
Thomsonipollis magnificus (Pflug & Thomson) Krutzsch 

Plate 8, figure 19 

Thomsonipollis magnificus is a distinctive triporate 

species sometimes classified with the Normapolles pollen, 

although the pores do not project beyond the broadly 

rounded triangular to circular amb, as the apertures do in 

most species of Normapolles pollen. Internally the pores are 

complexly structured in the manner of Normapolles pollen, 

and they are annulate. The sculpture is densely baculate. 

Thomsonipollis magnificus is known from the lower 

Tertiary of the Gulf Coast of the United States and from 

Europe (Krutzsch, 1960), and it also is present in the 

uppermost Cretaceous in New Mexico (R.H. Tschudy, 

1973). This species has not been reported from the 

Cretaceous in Wyoming or Montana and has not been 

reported previously from the Paleocene in the Powder River 

Basin. The botanical affinity of this species is unknown. 

Thomsonipollis magnificus is rare in the Tullock 

Member in the Powder River Basin. It was present in only 

two samples, carbonaceous shales from the Dry Creek 

locality in Montana and the Leverett Butte locality in 

Wyoming. It was notably common in the sample from 

Leverett Butte. 

Triatriopollenites granulatus (Simpson) Leffingwell 

Plate 8, figure 20 

Triatriopollenites granulatus includes small grains 

that are almost circular in outline and have three atriate 

pores, without annuli, that appear as notches in the am b. The 

exine is thinned in three areas located between each of the 

pores and the polar area; in some specimens the normally 

thickened exine in the interapertural and polar areas appears 

as a triradiate structure. 

This species was originally described as a species of 

the modem genus Engelhardia ("Engelhardtia") by Simpson (1961), although it has little in common 

morphologically with pollen of that genus. Leffingwell 

( 1970) transferred Simpson's species to the form genus 

Triatriopollenites. Simpson's specimens were from the 

lower Paleocene of western Scotland. In the Powder River 

Basin this species was reported previously by Leffingwell 

(1970) and Pocknall (1987). The botanical affinity of T. 

granulatus is unknown, but it is unlikely to be with the 

J uglandaceae, although that was implied by the original 

generic assignment. The affinity of this 'species also is 

unlikely to be with the Myricaceae, as might be inferred 

from Frederiksen's (1988) comments on the genus Triatriopollenites. 

Triatriopollenites granulatus is rare in Tullock 

M'ember in the Powder River Basin. In our study it was 

present in only two samples from the Leverett Butte locality 

in Wyoming. 

Triatriopollenites subtriangulus (Stanley) Frederiksen 

Plate 9, figures 5, 6 

Triatriopol/enites subtriangulus is one of three 

commonly occurring species of probable betulaceous or 

myricaceous affinity in the Tullock palynoflora. The three. 

species are Triatriopollenites subtriangulus (Stanley) Frederiksen, Triporopollenites infrequens (Stanley) Frederiksen, 

and Triporopollenites granilahratus (Stanley) n. comb. 

Leffingwell (1970) referred pollen from the Powder River 

Basin having the morphology of these species to his 

"Betulaceae-Myricaceae-Casuarinaceae Complex," and 

Jerzykiewicz and Sweet (1986, pl. 3, fig. 3), who had 

similar specimens from the uppermost Cretaceous and 

lower Tertiary in Alberta, designated them "BetulaceaeMyricaceae pollen." Pollen of this general morphology is 

common in the lower Tertiary throughout North America 

and elsewhere in the world; distinguishing either conspecific or slightly different species with certainty is difficult, 

and there has been uncertainty about the genera or form 

genera to which they should be assigned. Because Stanley's 

(1965) type specimens from the lower Paleocene of South 

Dakota are unavailable for study, ultimate resolution of 

taxonomic and nomenclatural problems associated with 

these species may be unattainable. The discussion of these 

three species herein is based on specimens from the Tullock 

Member in the Powder River Basin, which on the basis of 

geographic proximity are more likely to be conspecific with 

the South Dakota specimens than are others that hav~ been 

described from the Atlantic and Gulf Coasts, Europe, or 

elsewhere. 

Triatriopollenites subtriangulus was originally 

described from the lower Paleocene Ludlow and 

Cannonball Members of the Fort Union Formation in South 

Dakota by Stanley (1965). He assigned it to the q~odem 

genus Carpinus in the Betulaceae (birch family), but it is 

unlikely that.the botanical affinity of this species is with the 

Betulaceae. The structure of the exine at the pores shows 

clearly that it is not a species Carpinus. Furthermore, 

presence of weakly developed atria at the pores suggests 

affinity closer to the Myricaceae (bayberry family) than to 

the Betulaceae. Oltz (1969) transferred Stanley's species to 

the form genus Triporopollenites, and Norton and Hall 

(1969) apparently identified similar specimens as Triporopollenite,s coryloides Pflug., However, careful 

i~spection of Stanley's original illustrations (1965, ·pl. 43, 

figs. 12-16) and well-preserved Tullock specimens reveals 

the presence of a weakly ·developed endop<)fe and poorly 

defined atrium, features characteristic not of Triporopollenites but of the form genus Triatriopollenites. Frederiksen 

(1979) transferred Stanley's species to Triatriopollenites, 

and we follow that assignment here, although the atriate 

structure of the pores is obscure. We reject the subsequent 

reassignment of the species to the form genus Carpin{pites 

Palynostratigraphy, Tullock Member of Fort Union Formation, Montana and Wyoming : F25 
(Zhu and others, 1985); Carpinipites does not differ 

significantly from Triporopollenites. 

Triatriopollenites subtriangulus differs from Triatriopol/enites granulatus in larger size, more triangular shape, 

and lesser degree of development of atria at the pores. It 

differs from Tullock species of Triporopollenites in having 

atriate pores and in lacking annuli. 

In the Tullock Member Triatriopollenites subtriangulus was present in about half of the samples studied in detail. 

It was present in coal and all fine-grained clastic rock types. 

Triporopollenites granilabratus (Stanley) n. comb. 

Plate 9, figures I, 2 

Basionymn: Corylus granilabrata Stanley, 1965, p. 293, pl. 43, 

figs. 17-28. 

Triporopollenites granilabratus is the second of three 

commonly occurring species of probable betulaceous or 

myricaceous affinity in the Tullock palynoflora. The other 

species are Triporopollenites infrequens (Stanley) Frederiksen and Triatriopollenites subtriangulus (Stanley) Frederiksen. Refer to the general comments on these species in the 

first paragraph under Triatriopollenites suhtriangulus. 

Triporopollenites granilabratus . was originally 

described by Stanley (1965) from the Ludlow Member of 

the Fort Union Formation in northwestern South Dakota. He 

assigned the species to Corylus, a modem genus in the 

Betulaceae (birch family), but the morphology of neither 

this fossil species nor pollen of living species of Corylus is 

distinctive enough to permit this assignment to be verified. 

Consequently, assignment to a form genus is more 

appropriate. Norton (in Norton and Hall, 1969) transferred 

Stanley's species to the form genus Triatriopollenites, 

which is characterized by presence of atriate pores in which 

the endexinallayer forms an endopore having much greater 

diameter than the exopore. Their specimen (1969, pl. 5, fig. 

18) possibly shows such structure at the pores (although the 

photomicrograph is unclear), but their specimen does not 

closely resemble Stanley's (1965, pl. 43, fig. 17-28), nor 

ours from the Powder River Basin. All but one of Stanley's 

specimens and all of ours show thickening of the exine at 

the pores (small annuli). If the pores are annulate and not 

atriate, the species is cannot be assigned to Triatriopollenites. 

Srivastava (1972a) transferred Stanley's species to 

the form genus Casuarinidites, which is based on a triporate 

species from the Southern Hemisphere. Frederiksen and 

Christopher (1978) noted that subtle but important 

differences exist between North American and Southern 

Hemisphere triporates of this general morphology, but at 

that time they followed Srivastava's use of Casuarinidites 

for the North American species. More recently, Frederiksen 

(1988) reviewed the morphology, taxonomy, and 

F26 Evolution of Sedimentary Basins-Powder River Basin 

nomenclature of some species of betulaceoid and myricaceoid morphology from North America and Europe, and the 

form genera Triporopollenites, Triatriopollenites, and 

Casuarinidites. He concluded that the North American 

species of this general morphology were inappropriately 

assigned to Casuarinidites. However, he also concluded that 

Stanley's species "Corylus" granilabrata should be 

assigned to Triatriopollenites, following Norton and Hall 

(1969). We do not follow that assignment because we 

maintain that Tullock specimens we believe to be conspecific with Stanley's are annulate, not atriate. Consequently, 

we have reassigned this species to the form genus Triporopollenites. 

Triporopollenites granilabratus differs from Triporopollenites infrequens, one of the other two betulaceoidmyricaceoid species in the Tullock palynoflora, in having 

small (rather than well developed) annuli around the pores. 

It differs from Triatriopollenites subtriangulus, the other 

betulaceoid-myricaeoid species, in having annuli and 

lacking atria. Triporopollenites granilabratus differs from 

Triporopollenites plektosus, a non-betulaceoid-myricaceoid 

triporate species, in having a rounded triangular outline and 

in lacking random folds in the exine. It differs from 

Triatriopollenites granulatus in lacking atria and in being 

considerably larger and having a more triangular amb. 

In the Tullock Member Triporopollenites granilabratus was present in about half of the samples studied in detail. 

It was present in coal and all fine-grained rock types. 

Triporopollenites infrequens (Stanley) Frederiksen 

Plate 9, figures 3, 4 

Triporopollenites infrequens is the third of the three 

commonly occurring species of probable betulaceous or 

myricaceous affinity in the Tullock palynoflora (the other 

two are Triporopollenites granilabratus and Triatriopollenites subtriangulus). Refer to the general comments on 

these species in the first paragraph under Triatriopollenites 

subtriangulus. 

Triporopollenites infrequens is triporate and has a· 

rounded triangular amb and scabrate exine; the pores are 

distinctly annulate. However, the pores are not vestibulate, 

and thus Stanley's (1965) original assignment of this 

species to the modem genus Betula is unjustified. Triporopollenites infrequens differs from Triatriopollenites 

subtriangulus in having annulate pores and in lacking atria 

and from Triporopollenites g~anilabratus in having thicker, 

more prominent annuli, which make the pores clearly 

aspidate. Among the Tullock triporates, Triporopollenites 

infrequens is most similar to T. granilabratus and can be 

distinguished from it primarily by the relatively more robust 

development of the annuli and secondarily by slightly 

smaller modal diameter. 
Stanley described his specimens as having vestibulate 

pores, but his illustrations (1965, pl. 43, figs. 7-11) do not 

show this feature. Frederiksen (1988) transferred Stanley's 

species to Triporopollenites. The form genus Triporopollenites is more appropriate for fossil specimens having annuli 

without vestibulae than is the modem genus Betula. The 

affinity ofT. infrequens may be with the Betulaceae, but it 

is not with Betula. 

Triporopollenites infrequens may have occurred in as 

many as half of our Tullock samples, but the difficulty with 

which it is distinguished from T. granilabratus during 

low-power scans of slides may have resulted in it being 

counted along with the latter species. It apparently was 

present in coal and all fine-grained rock types. 

Triporopollenites plektosus Anderson 

Plate 8, figures 21-23 

Triporopollenites plektosus is one of three species in 

the Tullock palynoflora that we assign to the genus Triporopollenites. It differs from the other two in not having a 

morphology that suggests affinity with the modem family 

Betulaceae. Triporopollenites plektosus is triporate and has 

a thin, scabrate exine. The pores are circular and have 

narrow annuli. The thin exine causes the grains to become 

irregularly folded on compression, and most specimens 

exhibit randomly oriented folds. Specimens are always 

almost circular in outline and were probably close to 

spheroidal in form before compression. As a consequence of 

the compression of these thin spheroidal forms, the pores 

are not necessarily located at the edge of compressed 

specimens. 

Triporopollenites plektosus was originally described 

from the uppermost Cretaceous and lower Paleocene in 

New Mexico (Anderson, 1960). Subsequently it was 

reported from the Upper Cretaceous Lance Formation and 

Paleocene Tullock and Lebo Members of the Fort Union 

Formation in the Powder River Basin (Leffingwell, 1970) 

and from the Upper Cretaceous and Paleocene Coalspur 

Formation in Alberta (Jerzykiewicz and Sweet, 1986). The 

botanical affinity of the species is uncertain. 

This species tends to dominate some assemblages in 

the Coalspur Formation (Jerzykiewicz and Sweet, 1986). In 

the Tullock Member it is generally rare. It was present in the 

lower, middle, and upper parts of the unit in fine-grained 

clastic rock types and was absent from coal. 

Ulmipollenites krempii (Anderson) Frederiksen 

Plate 9, figures 7, 8 

Ulmipollenites krempii includes triporate specimens 

and those having four or five pores at the equator (stepha-. 

noporate) and that have fine verrucate. sculpture. Some 

specimens have arci between two or more adjacent pores. 

Through compression, one or more pores of some 

specimens may appear to be displaced from the equator. 

Ulmipollenites krempii was originally described by 

Anderson ( 1960) from the uppermost Cretaceous and lower 

Paleocene in New Mexico. He placed the species in his new 

genus, Ulmoideipites. Thaf genus is synonymous with 

Ulmipollenites Wolff, however, because it differs in no 

important way. Frederiksen (1979) transferred Anderson's 

species to Wolff's genus. The binomial Ulmipollenites 

krempii was used previously for pollen of this morphology 

in the Powder River Basin by Pocknall (1987). Stanley 

(1965) did not record any. specimens under either Ulmipollenites or Ulmoideipites, although they were present in his 

samples. He misidentified some of them and erroneously 

assigned them to the modem juglandaceous genus Carya, as 

C. paleocenica Stanley. Norton and Hall (1969) assigned 

similar specimens from the Hell Creek and Tullock in 

Montana to species of both Ulmipollenites and Ulmoideipites. Leffingwell (1970) assigned specimens from the Lance 

and Fort Union Formations to Ulmipollenites. He 

distinguished two size classes among his specimens, those 

from 16 to 25 J.lm in diameter, and those from 25 to 35 J.lm 

(the larger specimens are more common in the upper part of 

the Fort Union than in the Tullock Member). In our study, 

we initially distinguished specimens less than or greater 

than 20 J.lm, but finally assigned all of them to a single 

taxon, Ulmipollenites krempii. 

Ulmipollenites krempii is one of the most commonly 

occurring species in the Tullock palynoflora in the Powder 

River Basin. It was present in all but two samples studied in 

detail. 

Angiosperm Pollen-Multiporate 

Chenopodipollis spp. 

Plate 9, figures 9, 10. 

Chenopodipollis spp. includes pollen grains that are 

spheroidal and periporate and have 20--30 circular, unbordered pores evenly distributed over their surfaces. The exine 

is tectate and either finely granulate or finely foveolate. 

More than one species might be distinguished on the basis 

of pore diameter and number and exine sculpture, but in this 

study all specimens conforming to this general description 

were grouped in one taxon. 

Pollen of this morphology apparently has not been 

reported previously in the Tullock Member or equivalents in 

the Powder River Basin or elsewhere in the Rocky 

Mountain region. It was not described or illustrated by 

Stanley (1965), Norton and Hall (1969), or Leffingwell 

(1970). It has been reported from the upper Paleocene of the 

Gulf Coast in Texas (Elsik, 1968; Nichols and Traverse, 

1971 ). Its botanical affinity probably is with the Chenopodiaceae (goosefoot family) or Amaranthaceae (pigweed 

Palynostratigraphy, Tullock Member of Fort Union Formation, Montana and Wyoming F27 
family); both families have living species that produce 

pollen of closely similar morphology. 

Chenopodipollis spp. was present in about one-third 

of our Tullock samples but not in high relative abundance. 

It was present in coal, carbonaceous shale, and mudstone at 

localities in both Montana and Wyoming. 

Erdtmanipollis cretaceus (Stanley) Norton 

Plate 9, figures 11, 12 

Erdtmanipollis cretaceus is spheroidal and periporate 

and has distinctive crotonoid-reticulate sculpture. Each pore 

is ringed by a rosette of sculptural elements that are elongate 

or triangular ih form and are aligned radially; the rosettes 

are interconnected in a reticulate pattern. Specimens are 

from 20 to 40 ~m in diameter. In poorly preserved 

specimens the sculpture can be stripped off, leaving a 

relatively smooth periporate form. Most Tullock specimens 

are well preserved. 

Erdtmanipollis cretaceus was first described by Stanley (1965), who assigned it to the modem genus 

Pachysandra (Buxaceae). Species of this genus produce 

pollen having the same distinctive morphology as the fossils 

but so do species of the modem genus Sarcococca, in the 

same family. The form genus Erdtmanipollis Krutzsch 

includes pollen of this morphology and is more appropriate 

because it is uncertain which modern genus may be 

represented by the fossils. Norton (in Norton and Hall, 

1969) transferred Stanley's species to Krutzsch 's genus. 

Oltz (1969) and Srivastava (1972b) each attempted to make 

the same new combination, but Norton and Hall's 

publication preceded theirs. Srivastava (1969) described 

closely similar forms from the uppermost Cretaceous of 

Alberta but named them E. albertensis. We regard the 

Canadian specimens as conspecific with E. cretaceus. 

Botanical affinity is with the Buxaceae (box tree family). 

Erdtmanipollis cretaceus was present in about onefourth of our samples from the Tullock Member. We also 

noted its presence in the Lance Formation. It is more 

common in coal than in clastic rock types and more 

common in the Montana part of the basin than in Wyoming. 

Penetetrapites inconspicuus Sweet 

Plate 9, figures 13-15 

Penetetrapites inconspicuus is triangular to circular in 

outline although due to random folding of its thin exine, it 

tends to be irregular in shape. It has three or four large, 

vaguely defined, poroid apertures, one of which may be 

polar rather than equatorial in position. The form of the 

grain and nature and position of the apertures is reminiscent 

of pollen of modem species of Cyperaceae. 

This species was originally described by Sweet 

( 1986), based on specimens from the Coalspur Formation in 

Alberta; Sweet noted that it also is present in the uppermost 

F28 Evolution of Sedimentary Basins-Powder River Basin 

Cretaceous and lower Paleocene of southwestern Saskatchewan. It has not been reported previously from the Powder 

River Basin. The botanical affinity of P. inconspicuus is not 

certain, but its morphology, especially that of the apertures, 

suggests that it may be related to the Cyperaceae (sedge 

family). If this pollen does indeed represent ancestral 

sedges, its occurrence suggests the presence of wetland 

depositional environments. 

Penetetrapites inconspicuus is rare in the Tullock 

Member. We found it only in carbonaceous shale from the 

Dry Creek, Montana, and Lance Creek, Wyoming, 

localities. In these samples it is associated with Pandaniidites typicus and Sparganiaceaepollenites sp., both of 

which also are interpreted to represent m·arsh plants. 

Wodehouseia fimbriata Stanley 

Plate 10, figure 12 

Wodehouseia fimbriata is one of two species of 

oculate pollen present in the Tullock palynoflora. The body 

of the grain is an elongate oval surrounded by a wide 

fimbriate flange. There are four pores, two on each side of 

the grain, at either end. 

Wodehouseia fimbriata was originally described by 

Stanley ( 1961 a) from the Ludlow Member of the Fort Union 

Formation in northwestern South Dakota. It also has been 

reported from the Tullock Member in the Hell Creek area of 

east-central Montana (Norton and Hall, 1967, 1969; Oltz, 

1969) and the lower Paleocene in central Alberta (Russell 

and Singh, 1978; Demchuck, 1990). This species has never 

been reported from the Upper Cretaceous and probably is 

restricted to the lower Paleocene. It has not been reported 

previously in the Powder River Basin. 

This species is rare in the Tullock Member in the 

Powder River Basin. It was found in only one sample of 

shale from the lower part of the unit at the Reno Creek, 

Montana, locality. This species serves as a guide fossil for 

the lower Paleocene, but it probably is near the southern 

limit of its paleogeographic range in southeastern Montana 

and northwestern South Dakota, where it was first 

described. 

Wodehouseia spinata Stanley 

Plate 10, figures 10, 11 

Wodehouseia spinata is the second species of ·oculate 

pollen in the Tullock palynoflora. Like W. fimbriata, it has 

an elongate, oval body and four pores. It also has a 

prominent flange surrounding the body, but the flange is 

narrower and is supported by a few rigid spines. Spines also 

are present as sculptural elements on the body of the grain. 

This species was originally described by Stanley 

(1961 a) from the Hell Creek Formation in northwestern 
South Dakota. It has been reported widely in the uppermost 

Cretaceous of. western North America (references in 

Nichols and Jacobson, 1982, p. 142). Nichols and others 

(1983) named their uppermost Cretaceous palynostratigraphic zone for Wodehouseia spinata. Stanley (1961a) and 

Norton and Hall (1967) believed this species to be restricted 

to the Cretaceous, but it also is present rarely in the 

lowermost Paleocene in Wyoming (Leffingwell, 1971), 

Montana (this study), North Dakota (Johnson and others, 

1989), and Alberta (Jerzykiewicz and Sweet, 1986; Lerbekmo and others, 1987). 

Wodehouseia spinata is rare in the Tullock Member. 

It was found in only two samples from localities in 

Montana, a coal from the East Beaver Creek locality and a 

carbonaceous shale from the Dry Creek locality. In contrast, 

it is relatively common in the Lance and especially in the 

Hell Creek Formations in Wyoming, Montana, and the 

Dakotas. 

Angiosperm Pollen-Jugate 

Dyadonapites reticulatus Tschudy 

Plate 9, figures 16-18 

Specimens of Dyadonapites reticulatus are inaperturate dyads. Individual grains of the dyad are spheroidal to 

ovoidal in form and equal or subequal in size. The exine is 

thin and the sculpture is finely reticulate. 

This species was originally described by B.D. 

Tschudy (1973) from the Judith River Formation (Upper 

Cretaceous, Campanian) in Montana. It was previously 

reported in the uppermost Cretaceous and lowermost Paleocene in Saskatchewan (Nichols and others, 1986), in the 

Lance Formation and the Tullock Member in the Powder 

River Basin at the Sussex K-T boundary locality (Nichols 

and others, 1992), and in the Tongue River Member of the 

Fort Union Formation in the Powder River Basin (D;T. 

Pocknall and D.J. Nichols, unpublished data). Its small size 

and unusual form may have caused it to be overlooked in 

other studies of the palynology of Upper Cretaceous and 

lower Tertiary rocks. The botanical affinity of Dyadonapites reticulatus is uncertain. Dyads are rare in the fossil 

pollen record. Some species of the Typhaceae (cattail 

family) produce obligate tetrads that have reticulate 

sculpture, but the individual grains of such tetrads are 

monoporate, as are the monad grains of other species of the 

Typhaceae and the morphologically similar reticulate 

monads of the Sparganiaceae (bur-reed family), whereas 

individual grains of D. reticulatus are inaperturate. Possibly 

D. reticulatus represents an ancestral species of one of these 

families. 

Dyadonapites reticulatus is rare in the Tullock 

palynoflora. We found it in only five samples. It shows no 

clear pattern of stratigraphic, geographic, or lithologic 

distribution. 

Simplicepollis ral/us (Stanley) n. comb. 

Plate 10, figures l-6 

Basionym: Eric:aceaeoipollenites raflus Stanley, 1965, p. 296-297, pl. 44, 

figs. 15-18. 

Stanley (1965) described "Ericaceaeoipollenites" rallus as inaperturate to weakly tricolpate grains arranged in 

tetrahedral tetrads. Well-preserved specimens from the 

Tullock Member in the Powder River Basin observed in 

differential interference contrast illumination reveal that the 

apertures of these tetrads are large, sometimes poorly 

defined ora. The form genus Ericaceaeoipollenites is a 

junior synonym of Ericipites Wodehouse, . which 

encompasses pollen tetrads of rather different morphology 

(compact, robust tetrads with distinctly tricolporate 

apertures). Stanley's species requires redescription and 

reassignment to an appropriate genus. 

Redescription-Triporate pollen united in obligate 

tetrahedral tetrads; individual grains spheroidal but easily 

distorted because exine is thin, about 0.5 J..Lm. Each grain 

bears three large orate apertures. Pores are about 5 by I 0 J..Lm 

in diameter and may be covered by thin membranes; 

apertures are difficult to resolve on many specimens. Exine ' 

psi late to scabrate, finely granulate on apertural membranes. 

Individual grains about 25 J..Lm in diameter; complete tetrads 

about 40 J..Lm in greatest dimension. 

The form genus Simplicepollis was proposed by 

Harris (1965) for a generally similar species from the lower 

Tertiary of Australia. Simplicepollis rallus differs from S. 

meridianus Harris, type species of the genus, in having 

thinner exine and larger pores. Both species have large orate 

apertures covered by membranes. S. ral/us differs from 

Inaperturotetradites scabratus in apertures and sculpture. 

The botanical affinity of S. rallus is uncertain, but it is 

unlikely to be with the Ericaceae (heath family), as was 

suggested by Stanley (1965), who tentatively referred it to 

the modem ericaceous genus Kalmia. 

Simplicepol/is ra/lus was originally described by 

Stanley (1965) from the Ludlow and Cannonball Members 

of the Fort Union Formation in South Dakota. It is abundant 

in the basal part of Ludlow Formation of the Fort Union 

Group in North Dakota (Johnson and others, 1989). In the 

Tullock Member of the Powder River Basin it was present 

in about one-third of samples studied in detail but not in 

high relative abundance in any of them. It was present in 

coal and all fine-grained clastic rock types and was more 

common in Wyoming than in Montana. 

'lnaperturotetradites scabratus Tschudy 

Plate I 0, figure 7 

Specimens of Inaperturotetradites scabratus are 

inaperturate tetrads. Individual grains of the tetrad are 

spheroidal or nearly so and are arranged in a tetrahedral 

Palynostratigraphy, Tullock Member of Fort Union Formation, Montana and Wyoming F29 
pattern. The exine is thin, less than I ~m, and scabrate. The 

diameter of Tullock specimens is 35-40 ~m. 

This species was originally described by B.D. 

Tschudy (1973) from the Judith River Formation (Upper 

Cretaceous, Campanian) in Montana. She noted that it is 

also present in Campanian and Maastrichtian rocks 

elsewhere in Montana and in Wyoming. Our record from 

the Tullock Member extends the range of the species to the 

lower Paleocene. 

Tschudy (1973) discussed the superficial resemblance 

of Inaperturotetradites scabratus and the tetrad Simp/icepol/is rallus (which she referred to by its original name, 

Ericaceoipollenites ral/us) and the possibility that the two 

species might turn out to be synonymous. The Tullock 

specimens of these species show the clear morphologic 

distinction that ex.ists between these species: /. scabratus is 

inaperturate (as recognized and described by Tschudy) and 

S. ral/us has poorly developed but definite orate to colpate 

apertures (as described by Stanley, I965, and herein); the 

exines differ also, being distinctly scabrate in /. scabratus 

and psilate to scabrate in S. ral/us. 

Inaperturotetradites scabratus is rare in the Tullock 

palynoflora. We recorded it only at the Dry Creek and Reno 

Creek localities, in the lower part of the Tullock Member. 

Angiosperm Pollen-Triprojectate 

Aquilapollenites reticu/atus (Mtchedlishvili) 

Tschudy & Leopold 

Plate I 0, figures 8, 9 

The morphology of Aquilapol!enites reticulatus is 

one of the most distinctive of any species of fossil palynomorph in the Tullock palynoflora. It is one of the species of 

triprojectate pollen whose morphology is not only unusual 

among fossil forms but is unknown among pollen of living 

plants. Aquilapollenites reticulatus has an ovoid body and 

three short equatorial protrusions that bear colpate 

apertures. The exine is finely but distinctly reticulate. 

The taxonomic and nomenclatural history of this 

species is somewhat unusual if not complex. Aquilapollenites reticu/atus was first described by Mtchedlishvili (in 

Samoilovich and others, I96I) from Siberia as "Parviprojectus" reticu/atus. Later that same year, Stanley (196I b) 

described essentially identical specimens from South 

Dakota that he named Aquilapol/enites reticulatus. His 

species is synonymous with Mtchedlishvili's. Tschudy and 

Leopold (197I), in their monographic treatment of the 

genus Aquilapollenites, transferred Mtchedlishvili' s species 

to Aquilapol/enites, which made Stanley's species a 

homonym as well as a synonym. We follow Tschudy and 

Leopold and reject assignment of this species to Integricorpus. 

Aqui/apollenites reticulatus survived the K-T 

extinction event, whereas most species of the genus did not. 

F30 Evolution of Sedimentary Basins-Powder River Basin 

This species is more common in the uppermost Cretaceous 

of the Rocky Mountain region than in the lowermost 

Paleocene, but it has been recorded from the Paleocene in 

Alberta by Jerzykiewicz and Sweet (1986), in North Dakota 

by Johnson and others (19R9), and in Montana and 

Wyoming (this study). 

Aquilapol/enites retic!A1atus is rare in Tullock palynoflora. In this study it was recorded in only two samples from 

lower part of the Tullock Member, in shale from the Reno 

Creek locality in Montana and in mudstone from the South 

Snyder Creek locality in Wyoming. 

CONCLUSIONS 

On the basis of the comparison of assemblages of 

fossil palynomorphs discussed here and by its position 

above the palynologically defined Cretaceous-Tertiary 

(K-T) boundary, the age of the Tullock Member is 

determined to be early Paleocene, equivalent to palynostratigraphic zones PI and P2 of Nichols and Ott (1978). 

Palynomorph assemblages of the Tullock Member are 

distinguishable from those of the underlying Lance and Hell 

Creek Formations and the overlying Lebo Member of the 

Fort Union Formation. Lowermost Paleocene assemblages 

also are present in the uppermost parts of the underlying, 

predominantly Cretaceous units at some localities in the 

Powder River Basin. At other places the base of the Tullock 

is coincident with the K-T boundary. The Tullock Member 

in the Powder River Basin is mostly or entirely biostratigraphicnlly correlative with the Tullock Member in eastern 

Montana; the Tullock, Ludlow, and Cannonball Members in 

northwestern South Dakota; the Tullock, Ludlow, and 

Cannonball Formations in southwestern North Dakota; and, 

with less precision, the lower part of the lower unnamed 

member of the Fort Union Formation in the Wind River 

Basin in Wyoming. 

The palynostratigraphic zonation of the lower Paleocene can be revised to some extent, based on results of our 

study of assemblages from the Tullock Member. The 

biostratigraphically important species of the pollen genus 

Momipites that defines palynostratigraphic zone Pl. in the 

Wind River Basin is absent from the basal Paleocene in the 

Powder River Basin, appearing first in the middle part of the 

Tullock Member. Zone PI in the Powder River Basin is 

characterized by presence of Momipites inaequalis instead 

of M. leffingwellii, the species that defines zone PI in the 

Wind River Basin. Zone P2 in the Powder River Basin is 

characterized by presence of Momipites inaequalis, M. 

leffingwellii, M. tenuipolus, M. waltmanensis, and M. wyomingensis; the last two species named characterize zone P2 

in the Wind River Basin. The presence of M. inaequalis and 

M. tenuipolus in the lower Paleocene in the Powder River 

Basin indicates strong biostratigraphic similarity with the 

lower Paleocene of the Raton Basin of southern Colorado 

and New Mexico, based on data of Fleming (1990). The 
Tft 

East Burnt 

Creek 

(NW) 

. .-. .-::·.: ::: .·.·. 

1:='.:: ::.=:.- ::;.',:: Sussex 

(SW) 

:: :' ·: ::::. :- · .... :. ~ : ::.: : : : :~: 

Tft 

Kl 

Lance 

Creek 

(SE) 

KhcL--------L~T~e~rt~ia~~l_ ______________ ~T~ft~;:-:;··.~; .. ;-=:;~:.·;·~:.;-:::;,::~T~e~rt~ia~ry~ __________________ j;;;;;;;~~T~e~rt~ia~ry __ ___ 

Cretaceous Kl Cretaceous Cretaceous 

METERS 

.---0 

1- 10 

'- 20 

:;:··.:· =~.·.:· .. ::::/:\ .. ·.· .. ·.·. ·.·. 

>>:<<> ... -<·.· .. ;·.:· 

EXPlANATION 

rX:?~:\.\1 Dinosaur bone -Coal U.i./!}/:{{:(1 Sandstone 0 Shale and mudstone 

Figure 5. Relationship between the Cretaceous-Tertiary (K-T) boundary, which is defined on the basis of palynostratigraphy 

(this study), and formation contacts, which are placed at the base of the first persistent coal bed above the stratigraphically highest 

dinosaur remains, at three sections in the Powder River Basin. No dinosaur bones were present in the East Burnt Creek section, 

but the coal bed shown is bed A of Rogers and Lee (1923), the base of the Fort Union Formation in that area. Khc, Hell Creek 

Formation; Kl, Lance Formation; Tft, Tullock Member of the Fort Union Formation. Locations of sections shown in figures 3 

and 4. 

presence of Wodehouseia fimbriata in the Tullock in the 

Montana part of the Powder River Basin indicates biostratigraphic similarity with the lower Paleocene of Alberta, 

based on data of Demchuk (1990). 

The palynoflora of the Tullock Member in the 

Powder River Basin includes 75 or more taxa. Excluding 

algae, which constitute about 12 percent of the taxa 

discussed here, the palynoflora is dominated by pollen of 

angiosperms (70 percent) and includes pollen of 

gymnosperms (1 0 percent) and spores of pteridophytes and 

bryophytes (20 percent). The most commonly occurring 

taxa are pollen of a palm (Arecipites tenuiexinous), platanaceous(?) and ulmaceous dicots (Tricolpites spp. and Ulmipollenites krempii), and conifers (Pityosporites spp.) and 

spores of ferns (Cyathidites diaphana, Laevigatosporites 

spp., and Reticuloidosporites pseudomurii). Locally 

abundant taxa tend to dominate some assemblages, 

reflecting concentration of parent plants in certain 

depositional environments. Among the angiosperms these 

taxa are the palm and ulmaceous dicot mentioned above, 

pollen of betulaceous and (or) myricaceous dicots (some 

species of Triporopollenites and Triatriopollenites) and 

dicots of uncertain affinity (Kurtzipites spp.), and pollen of 

a probably pandanaceous dicot (Pandaniidites typicus). 

Among the pteridophytes and bryophytes locally abundant 

taxa are the ferns mentioned above, two other species of 

fern (Toroisporis major and G/eicheniidites sp.), and sphagnum moss (Stereisporites spp.). No gymnosperms are 

believed to have been locally abundant in Tullock 

depositional environments. Conifer pollen (Pityosporites 

spp.), which is attributed to pines, probably was transported 

from adjacent highland areas by wind and water. No 

palynomorph species is known to be stratigraphically 

restricted to the Tullock Member, but four species that range 

into the Tullock from the underlying Cretaceous (Aquilapollenites reticulatus, Kurtzipites circularis, K. trispissatus, 

and Wodehouseia spinata) range no higher than the Tullock 

in the Powder River Basin. 

The relative abundances of pollen and spores indicate 

that Tullock plant communities probably consisted of wetPalynostratigraphy, Tullock Member of fort Union formation, Montana and Wyoming f31 
MONTANA 

Figure 6. Paleogeography of the area of the Powder River 

Basin in earliest Paleocene time. Readvance of the Western 

Interior seaway (Cannonball Sea) would tend to pond drainage 

progressively from southeast to northwest in the area that was 

to become the Powder River Basin. Pending would promote 

accumulation of peat that later formed coal deposits of the 

Tullock Member. The structural basin developed later in 

Paleocene. time. Paleogeography from Cherven and Jacob 

(1985, fig. 25). 

lands and mires interspersed among lowland forests of 

warm temperate to subtropical aspect Mires were inhabited 

mostly by ferns and in some places by sphagnum moss. The 

forests were dominated by a somewhat unusual mix of 

palms and deciduous trees including U1maceae, Platanaceae, and Betulaceae. The paleoclimatic interpretations we 

draw from this vegetation differ from those of an earlier 

study by Hall and Norton (1967), who placed undue 

emphasis on the presence of conifer pollen in the Tullock 

Member in eastern Montana and concluded that early 

Paleocene climates were considerably cooler than we 

believe. Our conclusions are consistent with more recent 

interpretations by Wolfe (in Nichols and others, 1988), 

which are based on the physiognomy of megafossil (leaf) 

assemblages. 

Some implications for sedimentary history of the 

Tullock Member can be drawn from the palynology of the 

Tullock Member. They supplement the major conclusions 

based on the sedimentology of the Tullock (Brown, in 

press). Tullock-style deposition, as defined by presence of 

carbonaceous zones and coal beds, was initiated in early but 

not earliest Paleocene time in the northwestern part of the 

Powder River Basin. This observation in conjunction with 

the presence of coal beds in the upper part of the Lance 

Formation and the transitional nature of the Lance-Tullock 

cont~ct in the southeastern part of the basin (Clemens, 1964; 

teffingwell, 1970) suggests that Tullock depositional 

environments spread from southeast to northwest across the 

basin in the early Paleocene. This conclusion is illustrated 

clearly by the relationship of the palynologically defined 

K-T boundary to the Lance-Tullock and Hell Creek-Tullock 

F32 Evolution of Sedimentary Basins-Powder River Basin 

lithostratigraphic contacts (fig. 5). The K-T boundary 

datum, which is a time line, shows that the formation 

contact is time transgressive from southeast to northwest 

across the basin. 

Wolfe and Upchurch (1986) invoked a sudden 

increase in precipitation following the K-T boundary event 

to explain putative widespread initiation of peat deposition 

in the northern High Plains in earliest Paleocene time. Data 

summarized in figure 5 for the Powder River Basin and by 

Johnson and others (1990) for the southwestern Williston 

basin are evidence against that hypothesis. The more likely 

control on early Paleocene paleoenvironments was 

temporary read vance of the Western Interior seaway, 

represented by the Cannonball deposits of the Dakotas. The 

readvance gradually raised base level and tended to pond 

the slowly flowing streams in the region of the Powder 

River Basin (Nichols and Brown, 1989, 1990). Ponded 

drainage promoted peat accumulation, and ponding affected 

local areas at varying times, not simultaneously. In the area 

that was to become the Powder River Basin, base level rose 

progressively from southeast to northwest. Peat 

accumulation began before the end of Cretaceous time in 

the southeast (Lance Creek, Wyoming), was essentially 

coincident with the K-T boundary in the southwest (Sussex, 

Wyoming), and did not begin until well into the early 

Paleocene in the northwest (East Burnt Creek, Montana). 

This conclusion is supported by regional paleogeographic 

mapping by Cherven and Jacob (1985). Their map, adapted 

here as figure 6, pertains primarily to the Williston basin 

area, and the presence of marine deposits in the southern 

Powder River Basin implied by their map is not supported 

by our palynological study of the Tullock Member. 

However, the general pattern of readvance of the sea 

probably is correct, and the progressive change in base level 

that would be a consequence explains the stratigraphic 

distribution of coal shown in figure 5. 

Our final conclusion concerns the Tullock coals 

themselves. The peat that eventually formed the Tullock 

coals was deposited in mires inhabited primarily by ferns. 

The vegetation of these coal-forming depositional 

environments differed from that which developed later in 

the Paleocene during deposition of the Tongue River 

Member of the Fort Union Formation and which was 

predominantly woody. The predominance of herbaceous 

rather than woody vegetation in Tullock mires may account 

in part for Tullock coals being thinner and less extensive 

than the younger Fort Union coals. 

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119-147, pls. 1-4. 

Nichols, D.J., Jacobson, S.R., and Tschudy, R.H., 1982, 

Cretaceous palynomorph biozones for the central and 

northern Rocky Mountain region of the United States, in 

Powers, R.B., ed., Geologic studies of the Cordilleran thrust 

belt: Rocky Mountain Association of Geologists, v. 2, p. 

721-733, pl. 1. 

Nichols, D.J., Jarzen, D.M., Orth, C.J., and Oliver, P.Q., 1986, 

Palynological and iridium anomalies at Cretaceous-Tertiary 

boundary, south-central Saskatchewan: Science, v. 231, 

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93-112, pis. 1-2. 

Nichols, D.J., and Traverse, Alfred, 1971, Palynology, petrology, 

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F34 Evolution of Sedimentary Basins-Powder River Basin 

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G.S., ed., Geological Society of America Field Trip 

Guidebook 1988: Colorado School of Mines Professional 

Contributions, no. 12, p. 205-210, 222-226. 

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___ 1969, Palynology of the Upper Cretaceous and lower 

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p. 1-64, pis. 1-8. 

Oltz, D.F., 1969, Numerical analyses of palynological data from 

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208-219, pis. 1-6. 

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Palynostratigraphy, Tullock Member of Fort Union Formation, Montana and Wyoming F35 

'(:U.S. GOVERNMENT PRINTING OFFICE: 1991-673-049/46,031 REGION NO.8 

PLATES 1-10 

Contact photographs of the plates in this report are available, at cost, 

from the U.S. Geological Survey Photographic Library, Federal Center, 

Denver, CO 80225 
PLATE 1. Algal cysts and monolete spores 

[All specimens x I ,000. England Finder coordinates in brackets] 

FIGURE 1. Schizoplzacus laevigatus (Stanley) n. comb. East Beaver Creek, Mont.; slide D6937-K 

(1) [G51/l]. 

2. Schizophacus sp. Cow Creek, Wyo.; slide D7419 (1) [M44/2]. 

3. Sigmopollis hispidus Hedlund. East Beaver Creek, Mont.; slide D6937-K (1) [R45/2]. 

4. Sigmopollis sp. East Beaver Creek, Mont.; slide D6937-K (I) [N60/1 ]. 

5. Algal cyst type 1. East Beaver Creek, Mont.; slide D6937-K (1) [G44/2]. 

6. Algal cyst type 2. East Beaver Creek, Mont.; slide D6937-K (1) [Q48/l]. 

7, 8. Tetraporina spp. 

7. Dry Creek, Mont.; slide D7000-B (1) [140/2]. 

8. Dry Creek, Mont.; slide D7000-B (1) [L49/0]. 

9, 10. lncertae sed is type 1. Two levels of focus on a single specimen; South Snyder Creek, 

Wyo.; slide D7422-E (1) [N70/3]. 

11-14. Laevigatosporites sp. L. 

11. Dry Creek, Mont.; slide D7000-B (1) [N39/2]. 

12. Dry Creek, Mont.; slide D7000-B (1) [P40/2]. 

13. South Snyder Creek, Wyo.; slide D7422-E (1) [R47/0]. 

14. Reno Creek, Mont.; slide D7411-C (1) [G44/3] 
U.S. GEOLO GICAL SU RVEY B U LLETIN 19 17- F PLATE 1 

2 

3 4 5 

7 9 10 

8 

1 2 

ALGAL CYSTS AND MONOLETE SPORES 
PLATE 2. Monolete and trilete spores 

[All specimens x 1,000, except 8, which is x 250. England Finder coordinates in brackets) 

FIGURES 1-5. Laevigatosporites sp. S. 

1. Dry Creek, Mont.; slide D7000-B (1) [R37/1]. 

2. Dry Creek, Mont.; slide D7000-B (1) [R43/2]. 

3. Reno Creek, Mont.; slide D7411-C (1) [R65/0]. 

4. Dry Creek, Mont; slide D7000-B (1) [R53/1]. 

5. Jacobs Coulee, Mont.; slide D6940-AA (1) [H45/2]. 

6, 7. Reticuloidosporites pseudomurii Elsik. 

6. Lance Creek 1, Wyo.; slide D7100-B (1) [P61/2]. 

7. Dry Creek, Mont.; slide D7000-B (1) [Q65/0]. 

8-10. Azolla cretacea Stanley. 

8. Megaspore, x 250; South Snyder Creek, Wyo.; slide D7422-F (1) [G51/0]. 

9. Part of megaspore showing glochidia, x 1,000; South Snyder Creek, Wyo.; 

slide D7422-F (1) [S43/0]. 

10. Microspore; South Snyder Creek, Wyo.; slide D7422-F (1) [M40/2]. 

11. Osmundacidites sp. Dry Creek, Mont.; slide D7000-B (1) [059/0]. 

12. Cicatricosisporites sp. Dry Creek, Mont.; slide D7000-B (1) fK63/1]. 

13, 14. Ghoshispora bella (Kondinskaya) Srivastava. Two levels of focus on a single 

specimen; Lance Creek 1, Wyo.; slide D7100-B (1) [R63/0]. 
U.S. GEOLO GICA L SU RVEY 

6 

2 

7 

1 3 

MONOLETE AND TRILETE SPORES 

B ULLETI N 19 17-F PLATE 2 

4 

8 

10 

1 1 

14 
PLATE 3. Trilete spores 

[All specimens x I ,000. England Finder coordinates in brackets] 

FIGURES I, 2. Ghoshispora bella (Kondinskaya) Srivastava. Two levels of focus on a single 

specimen; Lance Creek 1, Wyo.; slide D710G-C (1) [K59/l]. 

3-5. Cyathidites diaplzana (Wilson & Webster) n. comb. 

3. Dry Creek, Mont.; slide D7000-B (1) [R47/l]. 

4. Dry Creek, Mont.; slide D7000-B (1) [065/0]. 

5. South Snyder Creek, Wyo.; slide D7422-E (1) [N48/0]. 

6-8. G/eicheniidites sp. cf. Gleichenia triangula Stanley. 

6. Jacobs Coulee, Mont.; slide D6940-AA (1) [R47/1]. 

7. East Beaver Creek, Mont.; slide D6937-D (1) [053/0]. 

8. East Beaver Creek, Mont.; slide D6937-L (1) [059/0]. 

9-11. Toroisporis major (Pflug) Stanley. 

9. Jacobs Coulee, Mont.; slide D6940-AA (1) [N52/1]. 

10. Dry Creek, Mont.; slide D7000-B (1) [R45/2]. 

11. Dry Creek, Mont.; slide D7000-B (1) [135/2]. 

12-15. Stereisporites spp. 

12. Dry Creek, Mont.; slide D7000-B (1) [H66/1 ]. 

13. Jacobs Coulee, Mont.; slide D6940-AA (1) [J44/3]. 

14. Dry Creek, Mont.; slide D7000-B (1) [G58/4]. 

15. Sussex, Wyo.; slide D7299-0 (1) [K41/2]. 
U.S. GEOLOGICAL URVEY BULLETIN 1917-F PLATE 3 

3 

2 

6 7 8 

5 

10 

12 1 3 14 15 

TRILETE SPORES 
PLATE 4. Trilete spores 

[All specimens x I ,000. England Finder coordinates in brackets] 

FIGURES 1-4. Stereisporites spp. 

1. East Beaver Creek, Mont.; slide D6937-L (1) [067/1]. 

2, 3. Two levels of focus on a single specimen; Dry Creek, Mont.; slide 

D7000-B (1) [L61/0]. 

4. Dry Creek, Mont.; slide D7000-B (1) [G42/3]. 

5, 6. Zlivisporis novomexicanum (Anderson) Leffingwell. Two levels of focus on a 

single specimen; Lance Creek 1, Wyo.; slide D7100-C (1) [L57/2]. 

7, 8. Zlivisporis novomexicanum? Two levels of focus on a single specimen; Dry 

Creek, Mont.; slide D7000-B (1) [H51/4]. 

9-12. Zlivisporis novomexicanum (Anderson) Leffingwell. 

9, 10. Two levels of focus on a single specimen; Dry Creek, Mont.; slide 

D7000--B (1) [M59/3]. 

11, 12. Two levels of focus on a single specimen; Lance Creek 1, Wyo.; slide 

D7100--C (1) [Q40/2]. 

13. Zlivisporis novomexicanum? Lance Creek 1, Wyo.; slide D7100-C (1) [L46/1]. 
lJ.S. GEOLOGICAL SlJRVEY BlJ LLETI . 1917-F PLATE 4 

2 3 4 

5 6 

9 10 

1 1 13 

TRILE TE SP ORES 
PLATE 5. Gymnosperm pollen 

[All specimens x 1,000. England Finder coordinates in brackets] 

FIGURE 1. Araucariacites sp. Reno Creek, Mont.; slide 07411-C (1) [Q58/l]. 

2, 3. Corollina sp. 

2. Lance Creek 1, Wyo.; slide 07100-C (1) [P44/0]. 

3. Lance Creek 1, Wyo.; slide 07100-C (1) [157/1]. 

4. Cycadopites scabratus Stanley. East Beaver Creek, Mont.; slide 06937-K (1) [Q50/0]. 

5, 6. Taxodiaceaepollenites hiatus (Potonie) Kremp. 

5.: Dry Creek, Mont.; slide 07000-B (1) [P45/0]. 

"6.-· ·Cow Creek, Wyo.; slide 07419 (1) [P55/2]. 

7-10. Pityosporltes spp. 

7. East Beaver Creek, Mont.; slide 06937-K (1) [M64/1]. 

8, 9. Two levels of focus on a single specimen; South Snyder Creek, Wyo.; slide 07422-F (1) [050/3]. 

10. East Beaver Creek, Mont.; slide 06937-H (1) [160!0]. 

11. Pityosporites? sp. Specimen possibly closer to Cedrus than to Pinus in botanical affinity; Dry Creek, Mont.; 

slide 07000-B (1) [H54/0]. 
U. S. GEOLOGICAL S URVEY 

5 

2 

6 

8 

10 

GYMNOSPERM POLLEN 

BULLETIN 1917-F PLATE 5 

3 

7 

9 

1 1 
PLATE 6. Gymnosperm pollen and monosulcate and tricolpate angiosperm pollen 

[All specimens x 1,000. England Finder coordinates in brackets] 

FIGURES 1, 2. Pityosporites? sp. Two levels of focus on a single haploxylonoid specimen; Cow Creek, Wyo.; 

slide D7419 (1) [L66/2]. 

3. Podocarpidites maximus (Stanley) Norton & Hall. East Beaver Creek, Mont.; slide D6937-K (1) [N35/2]. 

4-7. Arecipites tenuiexinous Leffingwell. 

4. East Beaver Creek, Mont.; slide D6937-K (1) [R54/2]. 

5. South Snyder Creek, Wyo.; slide D7422-E (1) [K45/0]. 

6. East Beaver Creek, Mont.; slide D6937-K (1) [N43/2]. 

7. East Beaver Creek, Mont.; slide D6937-K (1) [044/1]. 

8. Liliacidites leei Anderson. East Beaver Creek, Mont.; slide D6937-D (1) [P55/2]. 

9-11. Discoidites parvistriatus (Norton) n. comb. 

9. East Beaver Creek, Mont.; slide D6937-K (1) [N66/0]. 

10. East Beaver Creek, Mont.; slide D6937-K (1) [Q36/2]. 

11. South Snyder Creek, Wyo.; slide D7422-F (1) [040/2]. 

12-16. Fraxinoipollenites variabilis Stanley. 

12. Polar view; Lance Creek 2, Wyo.; slide D7137-l (1) [071/0]. 

13. Equatorial view; Lance Creek 2, Wyo.; slide D7137-I (1) [Q47/2]. 

14. Equatorial view; Lance Creek 2, Wyo.; slide D7137-I (1) [Q71/l]. 

15. Equatorial ,view; Lance Creek 2, Wyo.; slide D7137-I (1) [P47/4]. 

16. Equatorial view; Lance Creek 2, Wyo.; slide D7137-I (1) [R43/0]. 

17, 18. Quercoidites spissus Leffingwell. 

17. Jacobs Coulee, Mont.; slide D6940-F (1) [R36/2]. 

18. Questionably identified specimen; East Beaver Creek, Mont.; slide D6937-D (1) [L44/0]. 

19-21. Retitrescolpites anguloluminosus (Anderson) Frederiksen. 

19. Equatorial view; Cow Creek, Wyo.; slide D7419 (1) [S68/0]. 

20. Polar view; Leverett Butte, Wyo.; slide D7421-D (1) [Q63/2]. 

21. Polar view; Leverett Butte, Wyo.; slide D7421-D (1) [N50/1]. 
U.S. GEOLOGICAL SliRYEY BCLLETIN 1917- F PLATE 6 

3 

4 5 6 7 

8 9 10 1 1 

12 13 14 1 5 16 

1 7 18 19 20 21 

GYMNOSPERM POLLEN AND MONOSULCATE AND TRICOLPATE ANGIOSPERM POLLEN 
PLATE 7. Tricolpate and tricolporate angiosperm pollen 

[All specimens x 1,000. England Finder coordinates in bmckets] 

FIGURES 1, 2. Rousea spp. 

1. Dry Creek, Mont.; slide D7000-B (1) [H64/4]. 

2. Jacobs Coulee, Mont.; slide D6940-AA (1) [S39/2]. 

3, 4. Striatopollis tectatus Leffingwell. 

3. Polar view; Dry Creek, Mont.; slide D7000-B (I) [N59/2]. 

4. Equatorial view; Jacobs Coulee, Mont.; slide D6940-AA (1) [R64/0]. 

5-7. Tricolpites hians Stanley. 

5. Polar view; Dry Creek, Mont.; slide D7000-B (1) [K40/0]. 

6, 7. Two levels of focus on a single specimen in equatorial view; Dry Creek, Mont.; 

slide D7000-B (1) [K57/0]. 

8-12. Tricolpites spp. 

8. East Beaver Creek, Mont.; slide D6937-D (1) [052/0]. 

9. Reno Creek, Mont.; slide D7411-C (1) [F44/1]. 

10. Jacobs Coulee, Mont.; slide D6940-AA (1) [R42/0]. 

11. Jacobs Coulee, Mont.; slide D6940-AA (1) [S34/2]. 

12. East Beaver Creek, Mont.; slide D6937-D (1) [P64/3]. 

13, 14. Brevicolporites co/pella Anderson. 

13. Leverett Butte; Wyo.; slide D7421-E (1) [H55/4]. 

14. Leverett Butte, Wyo.; slide D7421-E (1) [S47/2]. 

15-17. Kurtzipites circularis (Norton) Srivastava. 

15. Lance Creek 2; Wyo.; slide D7137-E (1) [S61/0]. 

16. Cow Creek, Wyo.; slide D7419 (1) [051/1]. 

17. Cow Creek, Wyo.; slide D7419 (1) [P50/l]. 

18, 19. Kurtzipites trispissatus Anderson. 

18. Dry Creek, Mont.; slide D7000-B (1) [162/2]. 

19. Dry Creek, Mont.; slide D7000-B (1) [P39/2]. 

20, 21. Nyssapol/enites spp. 

20. Dry Creek, Mont.; slide D7000-B (1) [N54/2]. 

21. Dry Creek, Mont.; slide D7000-B (1) [R60/2]. 

22-24. Rhoipites sp. 

22. Dry Creek, Mont.; slide D7000-B (1) [R46/2]. 

23, 24. Two levels of focus on a single specimen; Jacobs Coulee, Mont.; slide D6940-AA (I) [H44/1]. 
U.S. GEOLOGICAL SURVEY BULLETIN 1917- F PLATE 7 

3 4 

5 6 7 8 

10 1 1 1 2 1 3 14 

1 5 16 1 7 18 

20 21 22 23 24 

TRICOLPATE AND TRICOLPORATE ANGIOSPERM POLLEN 
PLATE 8. Tricolporate, syncolporate, monoporate, and triporate angiosperm pollen. 

[All specimens x I ,000. England Finder coordinates in brJckets] 

FIGURES 1, 2. Tilia vescipites Wodehouse. Two levels of focus on a single specimen; East Beaver Creek, Mont.; 

slide D6937-K (1) [N58/0]. 

3, 4. Syncolporites minimus Leffingwell. 

3. Dry Creek, Mont.; slide D7000-B (1) [F51/3]. 

4. Dry Creek, Mont.; slide D7000-B (1) [P40/0]. 

5, 6. Cupanieidites inaequalis Leffingwell. 

5. Specimen showing polar island; Dry Creek, Mont.; slide D7000-B (1) [M61/l]. 

6. Specimen without polar island; Dry Creek, Mont.; slide D7000-B (1) [P47/2]. 

7-9. Pandaniidites typicus (Norton) Sweet. 

7. Dry Creek, Mont.; slide D7000-B (1) [J45/2]. 

8. Dry Creek, Mont.; slide D7000-B (1) [N44/2]. 

9. Dry Creek, Mont.; slide D7000-B (1) [R36/2]. 

10-12. Sparganiaceaepollenites sp. cf. Sparganium globites Wilson & Webster. 

10, 11. Two levels of focus on a single specimen; East Beaver Creek, Mont.; slide D6937-K (1) 

[K46/l]. 

12. Cow Creek, Wyo.; slide D7419 (1) [046/2]. 

13. Momipites inaequalis Anderson. Sussex, Wyo.; slide D7299-0 (1) [F60/4]. 

14. Momipites leffingwellii Nichols & Ott. Leverett Butte, Wyo.; slide 07421-D (1) [L51/4]. 

15, 16. Momipites tenuipolus Anderson. 

15. Leverett Butte, Wyo.; slide D7421-D (1) [M62/2]. 

16. Leverett Butte, Wyo.; slide D7421-D (1) [M62/2]. 

17. Momipites waltmanensis Nichols & Ott. Leverett Butte, Wyo.; slide D7421-D (l) [R40/0]. 

18. Momipites wyomingensis Nichols & Ott. Leverett Butte, Wyo.; slide D7421-D (1) [N63/2]. 

19. Thomsonipollis magnificus (Thomson & Pflug) Krutzsch. Leverett Butte, Wyo.; 

slide D742l-D (1) [Q42/4]. 

20. Triatriopollenires granulatus (Simpson) Leffingwell. Leverett Butte, Wyo.; slide D7421-D (1) [P64/2]. 

21-23. Triporopollenites plektosus Anderson. 

21. Polar view; Lance Creek 1, Wyo.; slide D7100-C (1) [Q51/0]. 

22. Folded specimen in polar view; Dry Creek, Wyo.; slide D7000-B (1) [H63/4]. 

23. Equatorial view; Dry Creek, Wyo.; slide D7000-B (1) [054/1 ]. 
U.S. GEOLOG ICAL SURVEY BULLET! 1917 - F PLATE 8 

2 3 4 5 

7 8 

10 1 1 12 13 

14 1 5 16 1 7 18 

19 20 21 22 23 

TRICOLPORATE, SYNCOLPORATE, MONOPORATE, AND TRIPORATE ANGIOSPERM POLLEN 
PLATE 9. Triporate, multiporate, and dyad angiosperm pollen 

[All specimens x 1,000. England Finder coordinates in brackets] 

FIGURES 1, 2. Triporollenites granilabratus (Stanley) n. comb. 

1. East Beaver Creek, Mont.; slide D6937-K (1) [063/4]. 

2. Jacobs Coulee, Mont.; slide D6940-F (1) [N38/4]. 

3, 4. Triporopollenites infrequens (Stanley) Frederiksen. 

3. Jacobs Coulee, Mont.; slide D6940-AA (1) [Q35/1]. 

4. Jacobs Coulee, Mont.; slide D6940-AA (1) [Q37/2]. 

5, 6. Triatriopollenites subtriangulus (Stanley) Frederiksen. 

5. East Beaver Creek, Mont.; slide D6937-D (1) [N41/1]. 

6. Leverett Butte, Wyo.; slide D7421-D (1) [N50/2]. 

7, 8. Ulmipollenites krempii (Anderson) Frederiksen. 

7. Triporate specimen; East Beaver Creek, Mont.; slide D6937-K (1) [P57/1]. 

8. Quadraporate specimen; Dry Creek, Mont.; slide 07000-B (1) [S58/0]. 

9, 10. Chenopodipollis spp. 

9. East Beaver Creek, Mont.; slide D6937-L (I) [Q63/1]. 

10. South Snyder Creek, Wyo.; slide D7422-F (1) [050/3]. 

11, 12. Erdtmanipollis cretaceus (Stanley) Norton. Two levels of focus on a single specimen; 

Lance Creek 2, Wyo.; slide D7137-I (1) [S54/3]. 

13-15. Penetetrapites inconspicuus Sweet. 

13, 14. Two levels of focus on a single specimen; Lance Creek 1, Wyo.; slide D7100-C (1) [J68/2]. 

15. Dry Creek, Mont.; slide D7000-B (1) [G57/3]. 

16--18. Dyadonapites reticulatus Tschudy. 

16, 17. Two levels of focus on a single specimen; South Snyder Creek, Wyo.; slide D7422-E (1) 

[R58/2]. 

18. Lance Creek 1, Wyo.; slide D7100-B (1) [M41/3]. 
U.S. GEO LOGI CAL SURVEY BULLET!!'\ 1917- F PLATE 9 

4 

5 6 7 8 

9 10 1 1 

13 1 5 

16 1 7 18 

TRIPORATE, M ULTIPORATE , AND DYAD ANGIOSPERM POLLEN 
PLATE 10. Jugate, triprojectate, and multiporate (oculate) angiosperm pollen 

[All specimens x 1,000. England Finder coordinates in brackets] 

FIGURES 1-6. Simplicepollis rallus (Stanley) n. cpmb. 

1-3. Three levels of focus on a single specimen; South Snyder Creek, Wyo.; slide D7422-E (1) 

[R59/2]. 

4, 5. Two levels of focus on a single specimen; Lance Creek 1, Wyo.; slide D7100-C (1) [161/2]. 

6. Cow Creek, Wyo.; slide D7419 (1) [K63/l] .. · 

7. lnaperturotetradites scabratus Tschudy. Dry Creek, Mont.; slide D7000-B (1) [V51/2]. 

8, 9. Aquilapollenites reticu'Latus (Mtchedlishvili) Tschudy & Leopold. Two levels of focus on a single 

specimen; South Snyder Creek, Wyo.; slide D7422-F (1) [L61/2]. 

10, 11. Wodehouseia spinata Stanley. · · 

10. Dry Creek, Mont.; slide D7000-B (1) [K66/0]. 

11. East Beaver Creek/Mont.; slide D6937-D (1) [K36/0]. 

12. Wodehouseia fimbriata Stanley. Reno Creek, Mont.; slide D7411-K (1) [R40/2]. 
U .. GEOLOGICAL SURVEY BULLETIN 1917 - F PLATE 10 

2 3 

4 5 6 

7 8 9 

1 1 12 

JUGATE, TRIPROJECTATE, AND MULTIPORATE (OCULATE) ANGIOSPERM POLLEN 
SELECTED SERIES OF U.S. GEOLOGICAL SURVEY PUBLICATIONS 

Periodicals 

Earthqu~kes & Volcanoes (issued bimonthly). 

Preliminary Determination of Epicenters (issued monthly). 

Technical Books and Reports 

Professional Papers are mainly comprehensive scientific reports 

of wide and lasting interest and importance to professional scientists and 

engineers. Included are reports on the results of resource studies. and of 

topographic, hydrologic, and geologic investigations. They also.mclude 

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Bulletins contain significant data and interpretations that are of 

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investigations in all phases of hydrology, including hydrology, availability of water, quality of water, and use of water. . . . . 

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Maps 

Geologic Quadrangle Maps are multicolor geologic maps on topographic bases in 7 1/2- or 15-minute quadrangle fo~ats (scal:s m~nly 1:24,000 or 1 :62,500) showing bedrock, surficial, or engmeenng 

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Geophysical Investigations Maps are on topographic or planimetric bases at various scales, they show results of surveys using geophysical techniques, such as gravity, magnetic, seismic, or radioactivity, which 

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Miscellaneous Investigations Series Maps are on planimetric or 

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Permanent catalogs, as well as some others, giving comprehensive 

listings of U.S. Geological Survey publications are available under the 

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--.,....,-cnms ana Brown-==-rttCY"N"USI Ri\TTGRAPHY I ULLOCk MEMBER OF FORT UNION FORMATION, MONTANA AND WYOMING-U.S.