Miocene Pollen and Spore 

Flora of Eniwetok Atoll, 

Marshall Islands

GEOLOGICAL SURVEY PROFESSIONAL PAPER 260-11
Miocene Pollen and Spore 

Flora of Eniwetok Atoll, 

Marshall Islands

By ESTELLA B. LEOPOLD

BIKINI AND NEARBY ATOLLS, MARSHALL ISLANDS

GEOLOGICAL SURVEY PROFESSIONAL PAPER 260-11

A Miocene pollen and spore flora representing 

raised island, intertidal, and beach-ridge 

environments is described from depths of 

6JO to 2,500 feet beneath Eniwetok Atoll

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1969
UNITED STATES DEPARTMENT OF THE INTERIOR 

WALTER J. HICKEL, Secretary

GEOLOGICAL SURVEY 

William T. Pecora, Director

For sale by the Superintendent of Documents, U.S. Government Printing Office 

Washington, D.C. 20402 - Price $1 (paper cover)
CONTENTS

Abstract...________________________________________

Introduction._ _____________________________________

Area._________________________________________

Marshall Islands drill holes._____________________

Acknowledgments___ _ _-____--_-___.____--_____

Geologic relations.__________________________________

Lithologic types and ages._______________________

Lithologic sequence-___--_-___----_-___--_______

Paleoecoiogy __--_-___--___-___-_-______________

Paleobotany of the oceanic Pacific islands, by F. R. 

Fosberg _________________________________________

Present environment and flora of Eniwetok____________

Methods of study_______---_-__-__-_________________

Treatment of fossil samples._____________________

Reference collection of Recent pollen___----__-___-

Composition and relationship of fossil flora to Recent flora. 

Floristic composition.___________________________

Modern distribution of Miocene genera-------_--__

Distribution of similar living species_______________

Abundance of fossil pollen and spores in Eniwetok 

sediments. ___________________________________

Some aspects of modern pollen rain in eastern 

Micronesia- ___-____-_-__-___---__-___________

Floral sequence in drill holes.____________________

Ecological relations.________________________________

Mangrove swamp forms.________________________

Pisonia forest._________________________________

Chroococcalean algal assemblages.________________

Mixed atoll forest versus forest on raised coral 

limestone____________________________________

Long-distance transport hypothesis.______________

Summary of environmental conditions.____________

Relation of Eniwetok Miocene flora to other fossil floras, 

and paleogeographic implications.___-____-----.____

Systematic descriptions._____________________________

Angiospermae. _ ________-___----_-__.___________

Monocotyiedonae__ _ ____---_--______________

Pandanaceae_ __________________________

Pandanus- _________________________

?Palmae_ ______________________________

Livistona type______________________

Dicotyledonae_ __--______---_______-______

Nyctaginaceae...__-_____-_____-_--___._

Pisonia cf. P. grandis_______________

Euphorbiaceae __________________________

Acalypha __________________________

Malvaceae. _----________-__.____-______

Thespesia cf. T. lampas- _____________

Sonneratiaceae -_______---______--_-_-_-

Sonneratia cf. S. alba. ________________

Page

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Systematic descriptions—Continued 

Angiospermae—Continued

Dicotyledonae—Continued

Rhizophoraceae. ___-.________-_--__----_

Rhizophora cf. R. apiculata.- _________

Rhizophora cf. R. mucronata- _________

Bruguiera cf. B. gymnorhiza __________

Ceriops cf. C. tagaL _________________

Combretaceae- ________-___---_____-_-_-

Terminalia cf. T. catappa ____________

cf. Combrelum. _____________________

Lumnitzera cf. T*. littorea. ______ ______

Myrtaceae. ____________________________

cf. Eugenia.------------------------

Boraginaceae. __________________________

Tournefortia cf. T. argentea___________

Cordia cf. C. subcordata-.- ___________

Verbenaceae____ _ _______________________

Avicennia cf. A. marina. _____________

Rubiaceae.____________________________

Ixora cf. /. casei-, _______ ___________

Gardenia cf. G. grievei-- _____________

Morinda cf. M. citrtfolia _____________

cf. Guettarda-- _____________________

cf. Timonius- ______________________

Randia cf. R. cochinchinensis - ______ _.

cf. Scyphiphora- ____________________

Dicotyledonous pollen of uncertain family affinity..--------------------------------

?Moraceae_ _______-_______---_-_-----_-

Malaisia type______________________

?Leguminoseae ____-_____-_--__---_----_ 

Sophora type_______________________

?Simarubaceae_ ________________________

Brucea type.____________-___-_----_

Picrodendron type___________________

?Caliitrichaceae_ _______________-----_-

Callitriche type.________-_____------

?Hippocrateaceae_ ______________________

Salacia type____ --------------------

?Elaeocarpaceae ________________________

Elaeocarpus type___________------_

?Rhizophoraceae__--_ _ __________________

Gynolroches type____________________

?Verbenaceae____ _ _____-_-__--_---------

Callicarpa type_ --------------------

? Gesneriaceae ______________-_--_-_-----

Cyrlandra type_______-_____-_-----_

? Rubiaceae ----------------------------

Coprosma type- ---------------------

References cited-____________---____--_-------------

Index.__-_-_-____--_----_-------------------------

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m
IV CONTENTS

ILLUSTRATIONS

[Plates follow index]

Page

PLATE 304. Miocene algae and marine cysts from Eniwetok and recent algae from the Gilbert Islands.

305. Miocene fern spores and monocotyledonous pollen of Eniwetok and selected modern counterparts.

306. Miocene dicotyledonous pollen of Eniwetok and their modern counterparts, Nyctaginaceae, ?Leguminoseae, 

Euphorbiaceae, ?Hippocrateaceae, Malvaceae.

307. Miocene Sonneratiaceae pollen of Eniwetok and modern comparative material.

308. Miocene Rhizophoraceae pollen of Eniwetok and Guam and modern comparative material.

309. Miocene Combretaceae pollen of Eniwetok and modern comparative material.

310. Miocene dicotyledonous pollen of Eniwetok and their modern counterparts, Myrtaceae, Boraginaceae, Verbenaceae, Rubiaceae.

311. Miocene dicotyledonous pollen of Eniwetok and their modern counterparts, Rubiaceae and undetermined

pollen types. 

FIGURE 332. Map of western Pacific region, showing location of Eniwetok and the Marshall Islands.____________________ 1135

333. Drill-hole sections, Eniwetok and BikinL___-___--___-----__-_----_____-__-__________________________. 1137

334. Paleoecology logs of drill holes E-l and F-l on Eniwetok and drill holes 2A and 2B on Bikini_____________ 1139

335. Map of Eniwetok Atoll showing location of drill holes F-l, K-lB, and E-l_______________________________ 1141

336. Generalized depth chart and section of Eniwetok Atoll-__----_----_--_--__--_-___-_____________________ 1142

337. Map of Bikini Atoll showing location of drill holes 2A and 2B__.________________________________________ H42

338. Map of northern Marshall Islands showing vegetation zones. ___________________________________________ 1142

339. Map showing distribution of modern and fossil Sonneratia.. _____________________________________________ 1148

340. Bar graph showing calculated number of pollen, spores, and colonial algae per gram of sediment in drill

hole E-l_----____-_-_____--_______----_______--_---_---__--___-_-----_--_--__________________ 1153

341. Bar graph showing calculated number of pollen, spores, and colonial algae per gram of sediment in drill hole

F-l____._____________________________________________________________________________________ 1153

342. Pollen diagram showing percentages of total pollen and spores in Eniwetok drill holes E-l and F-l__________ 1154

TABLES

Page 

TABLE 1. Calculated number of pollen, spores, and Chroococcalean algal colonies per gram of sediment, Eniwetok and

Bikini drill holes____--_______________________________--_-----_-__--_--_---_____------_-_----. 1145

2. Distribution of living taxa (native occurrences only) with which Eniwetok fossils show affinity-_____________ 1152

3. Calculated number of pollen and spores and Chroococcalean algal colonies in modern sediments from eastern

Micronesia. -_-_____-_____________________________-____-_____-__----__-___-_--___-___--__-_---_ 1155

4. Percentage composition and absolute numbers of pollen and spores per gram in modern sediments from Metalanim Harbor area, Ponape, Caroline Islands-______-___________--___________----_-__--------_---_- 1155

5. Percent total pollen and spores tallied in sediments from drill holes F-l and E-l, Eniwetok_________________ 1157

6. Habits and habitats of living taxa with which Miocene fossils of Eniwetok show affinity.___________________ 1160
BIKINI AND NEARBY ATOLLS, MARSHALL ISLANDS

MIOCENE POLLEN AND SPORE FLORA OF ENIWETOK ATOLL, MARSHALL ISLANDS

By ESTEULA B. LEOPOLD

ABSTRACT

Drill-hole sediments from depths of 670 to 2,500 feet beneath 

Eniwetok contain zones in which pollen, spores, and colonial 

blue-green algae are very abundant. The Miocene age of these 

sediments is established by the contained Foraminifera. Sparse 

pollen at 4,528-4,553 feet is of Eocene age based on associated 

Foraminifera.

Fifty-seven kinds of plants are represented in the Miocene 

flora, and these are mainly dicotyledons, but also present are 

remains of blue-green algae, pteridophytes, and monocots. 

Seventeen angiosperm genera were identified, and these can be 

grouped as follows. Four are native to Eniwetok today: Pandatuts, Pisonia, Tourncfortia, and Cordia. Six now grow in the 

southern Marshalls, but are not native to Eniwetok: Sonncratia, Rhisophora. Bniguicra, Lumtiitzera, Morinda, Randia. Five 

grow in western or central (but not eastern) Micronesia today: 

Acalypha, Ccriops, Terminalia, Aviccnnia, Ixora. One other 

genus, Gardenia, occurs in Borneo or New Guinea but is unknown 

in Micronesia. In addition, Thcspcsia of the Malvaceae was identified, but the Miocene fossils do not show an affinity with an 

existing Micronesian strand species, T. populnca-; instead they 

are related to a Malayan species, T. lampas. an upland form 

with a unique pollen morphology.

On a subgeneric basis, 80 percent of the Miocene flora now 

has relatives in the Western Caroline Islands, and the bulk of 

these relatives also grow in Indo-Malaya. This preponderance 

suggests that the primary affinity of the Miocene flora of Eniwetok is with the present flora of western Micronesia.

From the present habitats of taxa which are related to the 

Miocene forms, the following Miocene environments can be inferred for Eniwetok.

1. Mangrove swamps in intertidal zones: typified by very abundant Rhizopliora pollen, and occasional pollen of Sonneratia, 

Lumnitscra. Ceriops, Avircnnia.

2. Beach-ridge environments typified by strand genera such as 

Morinda, Pandaiuift, Terminalia, and Cordia.

3. Mangrove depressions on beach ridges, based on presence of 

Britffiticra.

4. Raised island habitats including upland forest, in which soils 

are not saline: based on identification of Ixora, Acalyplia, 

Thespcsia cfl T, lampas, Randia and Gardenia.

5. Intertidal l>each rock, based on presence of large numbers of 

blue-green algae. 

Of these, only environments 2 and 5 exist today on Eniwetok.

Samples of modern mud from atolls of Micronesia contain 

very little, if any, pollen; but muds from lagoons and harbors 

of larger islands contain abundant pollen. From the preparation of modern mud samples from various Micronesian islands, 

I have come to these conclusion*:

1. If the island or atoll has a land area smaller than 5 square 

miles and has a maximum elevation below 20 feet, pollen 

rain is negligible, and pollen usually can not be found in 

sediments except in muds of thickly vegetated swamps. 

Large numbers of blue-green algae are present in many 

lagoon muds.

2. If the island is larger or considerably higher, pollen rain is 

apparently more substantial, for near-shore marine muds 

contain several hundred or more pollen per gram of sediment. If mangrove communities are present locally, pollen 

density may range from 1,000 to 35,000 per gram of sediment (dry weight). Blue-green algae are occasional.

In the Miocene sediments in which blue-green algae are 

numerous, pollen abundance ranges from 0 to 1,000 per gram in 

sediments. In the zones in which RMzophora pollen was1 especially abundant, pollen frequency went as high as 100,000 per 

gram of sediment—higher than my modern comparative material from Micronesia.

Considering the high abundance of Miocene pollen in the sediments of several zones, I conclude that the pollen is of local 

(not transported) origin and that the pollen rain was probably 

more substantial in the Miocene than now, suggesting either 

a more dense vegetation on the same land area or an increased 

land area. The presence of high-island forms in the plant assemblage corroborates evidence from fossil land snails that 

at times during the Miocene, Eniwetok was a raised limestone 

island that stood well above the sea and supported upland forest 

communities.

Drill holes at Eniwetok and Bikini reveal about 4,000 feet of 

carbonate sediments underlain by volcanic basalt. The sedimentary section, which has been studied in great detail by Schlanger 

(1963) and his associates, is mainly composed of coral and shallow-water sediments. Three deeply weathered zones, which show 

leaching and solution cavities and which contain no pollen and 

have unconformities at their tops, indicate at least three periods 

of prolonged emergence of Bikini and Eniwetok—one between 

the late Eocene and the Miocene, one during the Miocene, and 

one in the post-Miocene interval. The evidence from lithology 

and fossils indicates that Eniwetok, Bikini, and probably the 

other Marshall Islands, are cylinders of coral slowly building 

on a sinking volcanic neck or guyot; subsidence has occurred 

in Eocene and younger time, and there were three major periods of emergence during which the coral rocks' were weathered 

subaerially.

From my analyses of Miocene pollen floras of Fiji and Guam, 

I note that some forms in both floras record spectacular cases 

of former wide ranges.

At Guam, Miocene pollen of Anacolosa (Olacaceae) and probable Wikcstrocmia (Thymeliaceae) are both Indo-Malayan, and 

I find no records that they grow in Micronesia today. Other

1133
1134 BIKINI AND NEARBY ATOLLS, MARSHALL ISLANDS

plants identified from the Miocene of Guam connote strandline 

vegetation (Rhizophora, Pisonia, Pandanm, Combretum or 

Tcrmmalia), and one high-island form (Ixora-) was found; 

these genera probably grow at Guam today.

At Fiji, Miocene pollen assemblages include Sonneratia, 

which now grows as far east as the Southern Mars-halls and New 

Guinea, and Anonaceae, cf. Milinsa; the family Anonaceae is 

apparently absent from Fiji today. Other Miocene forms from 

Fiji include strand plants (Rhizoph'ora, Morinda, cf. Timonim, 

Tcrminalia or Conibretum, Palmae) and various ferns.

A Miocene pollen flora from Palau seems to be largely composed of native genera. A Miocene pollen flora from Midway subsurface samples is now under study, but it is too early to state 

results.

Late Cenozoic floras of the north temperate zones show a general loss in forms, or impoverishment of the great floristic diversity characteristic of the Miocene. This change is usually associated with a late Cenozoic deterioration of climate. For example, in the northwestern coastal United States, from twothirds to one-half of the plant genera have disappeared from 

the regional flora since the Miocene, and the flora has changed 

in aspect from warm temperate to cool temperate.

At Eniwetok, 78 percent of the Miocene plant genera no longer 

grow on the atoll, and 66 percent do not grow any longer in the 

Marshall Islands. In spite of the similarity of these percentages 

with those of the coastal United States, the nature of the Eniwetok floral change does not suggest that it is caused by climate 

alone. The evidence from Eniwetok and Bikini overwhelmingly 

indicates that relative subsidence and emergence of the atolls 

have been extremely limiting factors. Tectonic factors probably controlled the availability of fresh-water environments, the 

total amount of land available to plants, the height of atoll 

ridges, and therefore the vulnerability of lagoon plants to 

typhoons; lastly, tectonic factors probably controlled the height 

of the island above sea level, which would probably affect the 

total amount of rainfall received.

INTRODUCTION

The purpose of this investigation was to identify and 

describe pollen, spores, and algae from drill-hole sediments of Miocene age on Eniwetok Atoll, and to determine thereby the nature of plant life and environment 

on that atoll during the Miocene.

Two deep holes were drilled to basement rock under 

Eniwetok in 1952 (Ladd and others, 1953) to determine 

the nature and depth of the sedimentary rocks beneath 

the atoll. The operation was supported by the Armed 

Forces Special Weapons Project and carried out for the 

Atomic Energy Commission and the Los Alamos Scientific Laboratory in cooperation with the Office of Naval 

Research and the U.S. Geological Survey. The middle 

and upper middle parts of the 4,000 feet of sedimentary 

rock above the igneous-rock foundation were found to 

be of Miocene age, according to contained Foraminifera 

(Cole, 1957; Todd and Low, 1960), and the present 

study is mainly concerned with these Miocene sediments. Pollen from selected drill-hole sediments from 

Bikini Atoll is also described.

I attempted pollen analysis of a few Eniwetok Miocene samples in 1957. The discovery of abundant fossil 

pollen in drill hole F-l at depth 810-860 feet, as mentioned by Ladd and Tracey (1957, p. 218) and by Ladd 

(1958, p. 194), indicated that a detailed palynological 

study should be made.

In this study the Miocene pollen and spore forms 

from Eniwetok are compared on generic and subgeneric 

levels with living forms from Micronesia. Identification on these taxonomic levels, which are most often the 

feasible limits of plant identification based on palynological evidence alone, provides a picture of the general 

type of vegetation that inhabited the atoll during the 

Miocene. The generic list of plants also gives some indication of the habitats that existed in the area.

Because information on the number of fossil pollen 

grains per gram of Miocene sediment might be worth 

comparing with pollen density in Recent sediments 

from the atoll area, the fossil samples were prepared 

by measured aliquots. For comparison, collections of 

Recent lagoon muds from Micronesia were obtained 

from several workers, and these were prepared by the 

same aliquot method. Tallies of pollen are extrapolated 

to number of grains per gram of sediment wherever 

possible.

For floristic comparison with the Miocene pollen 

assemblage of Eniwetok, collections of probable Miocene 

age from Fiji, Guam, and the Palau Islands were obtained from several field geologists and analyzed for 

fossil pollen and spores. I refer to these collections in 

this report. The general results of this study were summarized earlier (Leopold, 1963).

Because the pollen and spores are of a relatively 

young age, and because the primary objective here is to 

compare them with living material, the following taxonomic procedure seems appropriate. Where possible, the 

forms are identified to the nearest living plant group, 

and similarities to pollen of living species are cited with 

the indication "cf." (compare to). Where no family affinity is certain, the forms are indicated by arbitrary 

code numbers following the system suggested by 

Tschudy (1957). If a family assignment cannot be made, 

morphological comparisons with genera are cited as 

type, for example, "Brucea type." No formal species 

names for fossil pollen or spores are proposed in this 

report.

AREA

The fossil materials described here were obtained 

from drill holes on Eniwetok and Bikini Atolls in the 

northern Marshall Islands. These islands are 200 miles 

apart and lie in easternmost Micronesia. (See figs. 332, 

338.)
110°

MIOCENE POLLEN AND SPORE FLORA OF ENIWETOK ATOLL, MARSHALL ISLANDS

120° 130° 140" 150° 160° 170° 180° 170° 160° 150°

1135

. BONIN IS 

Okinawa^ VOLCANO IS,

• 

„• IwoJima; 

TAIWAN

FIG ORE 332.—Western Pacific region, showing location of Eniwetok and the Marshall Islands. Micronesia proper includes the Pacific islands east 

of the Philippines and north of the equator (map modified from Tracey and others, 1964).

Miocene pollen from outcrops on Guam, the Palau 

Islands, and Fiji were also examined for comparison 

with the Marshall Islands fossil flora. Guam is in the 

Mariana Islands group, about 1,200 miles west of Eniwetok (fig. 332). The Palau Islands and Fiji lie 1,800 

miles west and 1,300 miles southeast of Eniwetok, respectively. Ponape, from which modern pollen samples 

were obtained for comparison, lies 450 miles southwest 

of Eniwetok (fig. 332).

MARSHALL ISLANDS DRILL HOLES

The location of the three drill holes on Eniwetok 

Atoll that are discussed in the present report is shown 

in figure 335; these are drill holes F-l on Elugelab, 

K-1B on Engebi, and E-l on Parry Island. The drilling 

operations on Eniwetok and the lithology of the cores 

and cuttings obtained were described in detail by Ladd 

and Schlanger (1960) and Schlanger (1963). The holes 

on Bikini that were drilled in 1947 were described by 

Emery, Tracey, and Ladd (1954).

ACKNOWLEDGMENTS

Cores and cuttings from drill holes for this study 

were made available to me by Harry S. Ladd, whose 

helpful advice and aid throughout this project are most

gratefully acknowledged. For botanical guidance in 

making ecologic interpretations of the material and for 

providing me with up-to-date unpublished data on 

Micronesian plant distribution, I am very grateful to 

F. R. Fosberg of the National Research Council.

Identification of the fossil pollen material depended 

on the availability of appropriate modern pollen collections from herbarium material of Micronesia. Selected herbarium sheets for such collections were made 

available through the courtesy of the U.S. National 

Herbarium. With the permission of Dr. J. R. Swallen, 

Head Curator, U.S. National Herbarium, and Dr. A. C. 

Smith, then Director of the U.S. Museum of Natural 

History, I assembled material from about 600 plant 

species, including about 540 genera from the modern 

flora of Micronesia.

Recent sediments used for comparison include field 

collections by P. E. Cloud, Jr., from Onotoa, Gilbert 

Islands; by F. R. Fosberg and E. D. McKee from 

Jaluit; by J. I. Tracey, Jr., from Ifalik; by K. O. Emery 

from Bikini; and by Sam Riesenberg from Ponape.

Helen Pakiser, Imogene Doher, and Anne Davis assisted in the laboratory preparation of the pollen 

materials.
1136 BIKINI AND NEARBY ATOLLS, MARSHALL ISLANDS

GEOLOGIC RELATIONS

The structure of the reef at Eniwetok Atoll is better 

understood than that of most Pacific atolls because of 

information obtained from the two deep drill holes 

(F-l and E-l) that reached the basalt under the reef 

(Ladd and others, 1953; Ladd and Schlanger, 1960). 

Darwin's (1897) premise that an atoll reef is the product of upward and outward growth of a coral mass on 

a sinking island has been proved by the lithologic and 

paleontologic evidence obtained from the deep holes on 

Eniwetok Atoll. An interesting summary of Darwin's 

reasoning in relation to present subsurface evidence 

from this and other parts of Micronesia was presented 

by Ladd (1961, p. 710-711). Much of the detailed paleontologic evidence from these drill holes was described 

by various authors in previous chapters of Professional 

Paper 260.

LITHOLOGIC TYPES AND AGES

Lithologic information from Eniwetok deep drill 

holes indicates that the atoll reef is at least 4,630 feet 

in greatest thickness and that it rests on a somewhat 

irregular basalt surface. The thickness of the reef rock 

beneath Bikini is not yet known. A sedimentary profile of the drill holes on Eniwetok and Bikini by 

Schlanger (1963) is shown in general outline in figure 

333; this profile is based on a detailed study of the 

subsurface sediments using X-ray and chemical 

methods. Kocks penetrated in the five drill holes are 

classified by Schlanger (1963) and Macdonald (1963) 

as comprising five types.

1. Aragonitic limestone, unlithified. These sediments 

typically contain perfectly preserved mollusks, and 

some of the shells retain their original color patterns. Unaltered layers of aragonite presumably 

were not emergent, or at least not for a time long 

enough to permit alteration to calcite.

2. Calcitic limestone, with solution features, usually 

leached and lithified. In some levels the limestone 

contains prominent molds of coral and mollusks, 

and coarsely crystalline calcite fills the cavities. 

This sediment type was probably derived from primary aragonitic limestone by subaerial weathering 

during emergence.

3. Dolomitic limestone, well lithified, and containing 

calcite but no aragonite. Schlanger (1963) proposed that the dolomitization in these sediments 

may have followed the conversion of primary 

aragonite to calcite by solution and reprecipitation.

4. Partly recrystallized and leached limestones. These 

contain a mixture of calcite and aragonite matrix

and altered and unaltered fossils of coral and 

mollusks; the sediments are poorly lithified. 

Schlanger (1963) interpreted these limestones as 

being intermediate between aragonitic and calcitic, probably derived from aragonitic limestone 

by incomplete subaerial weathering. 

5. Basement basalt, somewhat altered by epigene solutions that formed carbonate veins in the upper 

layers. This alteration may have occurred when 

the top of the basalt was close to sea level, and part 

or all of the overlying limestone was well above sea 

level (Macdonald, 1963, p. 1047). 

The distribution of these rock types in the five drill 

holes permits a correlation of beds that is well substantiated by the fossil evidence. Four clear unconformities 

(fig. 333) have been identified in the sedimentary section; these are solution unconformities and present a 

rather sharp interface between a lower leached calcite 

sediment and an overlying primary aragonite. Three 

of the four unconformities coincide with faunal breaks 

(Schlanger, 1963).

The primary basis for age determination within the 

Eniwetok section is a study of diagnostic larger Foraminifera by Cole (1957) and of smaller Foraminifera 

by Todd and Low (1960). Cole reported that Recent, 

Pleistocene, and Pliocene larger Foraminifera occur 

from the surface to a depth of 615 feet, and below this he 

recognized several zones of Miocene age. Eocene sediments occur from a depth of 2,900 feet to the bottom 

of the holes, according to Cole (1957) and Todd and 

Low (1960). However, Todd and Low drew the upper 

boundary of the Miocene at a depth of about 500 feet 

instead of about 615 feet; they also suggested that the 

lowest 600 feet of what Cole considered Miocene may be 

Oligocene on the basis of smaller Foraminifera. Cole 

(1957) and Todd and Low (1960) seem to agree that 

there is as yet no certainty that Oligocene sediments are 

present.

LITHOLOGIC SEQUENCE

From the top downward, the section (fig. 333) may be 

summarized as follows.

The upper 70-100 feet in all four drill holes is unaltered aragonitic limestone, and below it is 150-200 feet 

of partly recrystallized and leached limestones; Schlanger (1963) suggested that a poorly developed unconformity exists at the top of the leached beds in each 

hole. Isotope dates on the sediments above that unconformity are from < 12,000 to 13,000 years, whereas 

immediately below, the range of dates is from 38,000 

to 280,000 years B.P. (Sackett and Potratz, 1963, p. 

1060). Sediments from these depth intervals were not 

examined for pollen.
MIOCENE POLLEN AND SPORE FLORA OF ENIWETOK ATOLL, MARSHALL ISLANDS 1137

DEPTH, IN FEET

K-1B

ENIWETOK 

F-l

BIKINI

E-l 2A 2B

500

1000

1500

2000

2500

3000

3500

4000

4500

2780ft

Top of Tertiary b (Cole) ,

Length of bar indicates roughly the percent

OL/ 

- OS

Limestone (calcite) with solution 

features

Partly recrystallized and leached limestones 

» ' A A

Limestone and unlithif ied sediments 

with primary aragonite

Basalt

Gradational zone

H________:

Position of cuttings and 

core samples analyzed

Solution unconformity in hole 

Correlation between unconformities

Total depth 4630 ft Foraminiferal zone

Numbers 1-15 along drill hole F-l and 1-3 along 

drill hole E-l indicate cored intervals

FIGURE 333.—Drill-hole sections showing weathered and unweathered limestone zones beneath Eniwetok and Bikini Atolls. The basalts underlying Eniwetok are shown (modified from Schlanger, 1963, fig. 308).

336-388 O—69———2
1138 BIKINI AND NEARBY ATOLLS, MARSHALL ISLANDS

At a depth of about 300 feet a very well developed 

unconformity exists where the partly leached sediments 

at Bikini and the primary aragonite beds at Eniwetok 

overlie calcitic limestone that shows solution features. 

This calcitic limestone is 300-400 feet thick. In contrast 

to the sharp contact at 300 feet, there is a gradational 

contact between the calcitic limestone and the unconsolidated aragonite beds below. Schlanger interpreted the 

calcite beds as a zone that had weathered under subaerial conditions. These sediments are of post-Miocene 

age, as indicated by larger Foraminifera (Cole, 1957), 

and some may be of Pleistocene age (Ladd, 1958). 

Samples from this interval were not studied for pollen. 

Beneath the weathered zone to a depth of about 1,000 

feet are primary aragonite beds rich in fossil corals, 

shallow-water mollusks (Ladd, 1958), and, at some 

levels, pollen. Larger and smaller Foraminifera indicate 

a Miocene age for this interval (Cole, 1957; Todd and 

Low, 1960) (fig. 333.) This zone, designated as Tertiary 

g by Cole (1957), is considered as late Miocene in age 

by Ladd (1958).

At a depth of 1,000 feet another sharp unconformity 

occurs at the top of a thick (300-800 ft) cemented calcite unit and represents another weathered zone. The 

calcite beds overlie (with a gradational contact) a 

very thick (about 1,000 ft) aragonite zone, which contains well-preserved remains of shallow-water Foraminifera, pelecypods, and corals. The lithology in this interval in drill hole F-l is poorly known. On the basis 

of larger Foraminifera from the various holes, this entire interval between 1,000 and 2,800 feet is of Miocene 

age (Tertiary e of Cole, 1957). However, smaller Foraminifera (Todd and Low, 1960) in the lower 600 feet 

of this zone suggest an early Oligocene age (Tertiary 

zone <?). Ladd (1958) considers Tertiary e to be early 

Miocene in age. The aragonite beds between 2,003 and 

2,510 feet are rich in Chroococcalean algae and contain some pollen.

A fourth solution unconformity marking the top of 

a thick calcite unit at the 2,780-foot level is well defined in drill hole E-1. Here Eocene calcite sediments 

(Cole's Tertiary zone 5) are overlain by Miocene aragonitic lime muds, and according to Cole (1957) this 

unconformity is the position of a sharp faunal break. 

Schlanger (1963, p. 996) concluded that the coincidence 

of this sedimentary unconformity with the faunal 

break indicates a post-Eocene emergence and erosional 

removal of Oligocene sediments before the first Miocene 

submergence of Eniwetok. Only spotty core runs of 

sediments at a depth below the 500-foot-thick Eocene 

calcite zone of hole E-1 are available, and most of these 

are from hole F-l; all are Eocene cemented dolomitic

limestones that contain shallow-water Foraminifera, 

corals, pelecypods, and calcareous algae. A few pollen 

grams were found in the lowest core run, only 100 feet 

above the basement basalt.

In summary, the three deeply weathered zones indicate at least three periods of prolonged emergence of 

Bikini and Eniwetok atolls—one after the late Eocene 

and before the Miocene, one during the Miocene, and 

one in the post-Miocene interval. The weakly developed 

unconformity at a depth of 300 feet suggests a brief 

emergence in the late Quaternary earlier than 12,000 

years ago.

PALEOECOLOGY

The ecology and paleoecology of sediments inferred 

from studies of Foraminifera, algae, corals, and mollusks have been discussed in detail by several authors 

(Tracey and others, 1948; Ladd and others, 1950; Cloud, 

1952; Emery and others, 1954; Forman and Schlanger, 

1957) and so will be only briefly summarized here.

Paleoecological interpretations for Eniwetok and 

Bikini are shown in the stratigraphic diagram (fig. 

334).

The sediments of the post-Miocene (younger than 

Tertiary g, fig. 334) are thought to represent lagoonal 

deposits, except for those at 140-300 feet in hole E-1, 

which are probably of reef-wall or reef-knoll origin.

The entire Miocene section is considered to be a shallow-water lagoonal deposit with the exception of certain zones below 1,750 feet in all drill holes; these zones 

probably represent a reef-wall environment in F-l and 

a lagoonal, fore-reef, and (or) open-shoal environment 

in E-1, 2A, and 2B. Abundant remains of the alga 

LitliopliyUum suggest a deeper water environment for 

parts of these zones.

The Eocene sediments in F-l, as far as they are 

known, seem to represent a fore-reef outer slope environment, and in the lower 300 feet shallow-water Foraminifera (Peneroplm triloculina. Omatanomolina, and 

Asterigerina zones, fig. 334) are present. These Foraminifera are also present at the top of the Eocene section in E-1, where other evidence suggests a near-reef 

environment; Todd and Low (1960) concluded that 

the basal parts of the F-l section are probably synchronous with the upper 700 feet of the E-1 Eocene 

section. Thus, the lower parts of the Eocene section in 

E-1 have no counterpart in F-l, and the unconformity 

at 2,780 feet in hole E-1 is greater than the unconformity in F-l (fig. 333). The only Eocene sediments recovered from the bottom of hole E-1 (at depths 4,078- 

4,100 ft) suggest shallow lagoonal and reef-wall environments (fig. 334).
MIOCENE POLLEN AND SPORE FLORA OF ENIWETOK ATOLL. MARSHALL ISLANDS 1139

DEPTH,IN FEET ENIWETOK

500-

1000-

1500-

2000-

2500-

3000-

E-l

BIKINI 

2A-B

4000-

4500-

Coral-mollusk- rich zone 

Top of Tertiary 6

zone

3500-2

Open shoal

No samples recovered

Unconformity 

Core

Numbers 1-15 along drill hole F-1, and 1-3 along 

drill hole E-1 indicate cored intervals

Total depth 4630 ft 

FIGURE 334.—Paleoecology logs of drill holes E-1 and F-1 on Eniwetok and drill holes 2A and 2B on Bikini. From Schlanger (1963).
1140 BIKINI AND NEARBY ATOLLS, MARSHALL ISLANDS

In summary, the combined evidence suggests that 

the greater part of the sedimentary section was deposited in relatively shallow water. Since Eocene time, 

at least three periods of prolonged emergence have occurred, during which the marine and lagoonal sediments underwent severe subaerial weathering.

PALEOBOTANY OF THE OCEANIC PACIFIC 

ISLANDS

By F. R. FOSBEKG

Paleobotanical work on Cenozoic material from the 

oceanic islands of the Pacific has been so rudimentary 

as to be almost nonexistent. Fossil calcareous algae 

from various Micronesian islands (including Guam, 

Saipan, Tinian, Rota, Palau, Bikini, and Eniwetok) 

were studied by J. H. Johnson, who published detailed 

and well-illustrated reports on algae from the Bikini 

drill holes (1954) and from the Eniwetok drill holes 

(1961). Mention was made of algal remains and also of 

carbonaceous material in the preliminary report on the 

Eniwetok core (Ladd and others, 1953). E. B. Leopold 

(in McKee and others, 1959) reported dinoflagellate 

cysts and rare pollen in Recent sediments from the 

lagoon of Kapingamarangi Atoll, Caroline Islands.

Lignite beds exist on Rapa in the Austral Group 

and on Babelthuap in the Palaus. Some fossils from the 

Babelthuap occurence were mentioned by Tayama 

(1939) and by Sato (1941), and material was collected 

there by P. E. Cloud, Jr., Gilbert Cor win, and P. Q. 

Elmquist; a cursory pollen study of these is reported in 

the present work (p. 1163). Attempts have been made to 

isolate from the Rapa lignite beds plant material collected by F. R. Fosberg in 1934, but no identifiable 

remains were found until recently, when Cranwell 

(1962, 1964) found scattered pollen in this and in Rapa 

material collected by the St. George expedition. The 

only positive identification of higher plant pollen from 

the material was Coprosma of the Rubiaceae; this genus 

now is represented by an endemic species (G. rapensis) 

on the island.

Boureau (1953) reported on certain fossil woods from 

the Mesozoic of New Caledonia. In Hawaii, tree molds 

and impressions of Sadleria ferns in lava are shown to 

tourists at Hawaii National Park and are described 

and illustrated in popular literature for tourists. The 

only scientific report on such impressions is a short 

paper by Palmer (1947) describing impressions of 

fronds of Gibotiwn chamissoi in recent lava in Kilauea 

Iki Crater, Hawaii. On Oahu a fossil flora preserved in 

volcanic tuff or ash at Salt Lake Crater was found and 

briefly described by Lyon (1930), but again no scientific

report was published. More material of this kind has 

been collected recently, and both collections are now 

in the laboratory of C. N. Lamoureus. Selling (1947) 

published an extensive report on pollen from cores 

taken in Hawaiian postglacial bogs. More recently some 

fossil wood from Guam was examined by E. S. Barghoorn (in Tracey and others, 1964, p. A32). Mention 

of plant fossils from the northern Marianas may be 

quoted in translation from Tayama (1952, p. 46) : "the 

tuff forming the surface of Alamagen and Guguan volcanoes contains fossilized plants such as coconut and 

screwpine leaves." Fosberg and Corwin (1958) reported 

a fossil flora from the tuffs on Pagan Island that was 

extensive enough to provide some basis for paleoecological speculation.

Fossil pollen records of mangrove vegetation in the 

Tertiary of Borneo were summarized by Muller (1964). 

Muller's own work indicates that the palm genus Nypa 

and probable Brownlowia (Tiliaceae) go back locally at 

least through the Eocene. He reported RMzophora-tj\>v 

pollen from Oligocene and younger sediments, and 

Sonneratia cf. caseolaris from lower Miocene and 

younger sediments. His earliest records of Sonneratia 

cf. alba are from uppermost Miocene to Recent, and 

of Avicennia type from middle Miocene to Recent.

PRESENT ENVIRONMENT AND FLORA OF 

ENIWETOK

Eniwetok Atoll lies in the northern and drier section 

of the Marshall Islands, at lat. 11°30' N., long. 162°14' 

E. It is oval shaped, elongate toward the northwest, and 

27 miles in greatest diameter. The forested larger islands 

all lie along the east flank of the atoll, whereas reefs 

and very small islets compose the west flank (fig. 335). 

The reefs of the atoll are well developed and have several 

shallow passages on their south margin and one deep 

passage on the southeast extending from the lagoon to 

the sea.

The sea-depth contours diagramed in figure 336 

shows a pronounced platform of basalt at a depth of 

500-800 fathoms (3,000-4,800 ft). Its axis trends northwest and it measures 52 by 28 miles. Below a depth of 

800 fathoms its flanks slope steeply. Hess (1946) suggested that this platform is an old guyot surface planed 

by wave action before subsidence, when the Marshall 

Islands were more highly elevated.

Eniwetok has a total of 39 islets, of which some of 

the larger are Parry, Engebi, and Runit. Most of the 

larger islands are on the eastern, or windward, side of 

the atoll.

Bikini Atoll, from which a few plant fossils were obtained, lies about 200 miles east of Eniwetok. The ocean 

between Eniwetok and Bikini is up to 13,000 feet deep.
MIOCENE POLLEN AND SPORE FLORA OF ENIWETOK ATOLL, MARSHALL ISLANDS

162°00' 162°10: 162°20' 162°30'

1141

1 MILE

INSERTS, APPROXIMATE

ENIWETOK ATOLL

PARRY ISLAND

15 MILES

FIGURE 335.—Map of Eniwetok Atoll, showing location of drill holes F-1, K-IB, and E-1.

Bikini Atoll is also oval shaped and has a northwesttrending axis; most of its larger islands are also on the 

eastern, or windward, side (fig. 337).

The current drift in the northern Marshalls is westward in the path of the North Equatorial Current; an 

equatorial countercurrent flo\vs eastward through the 

southern Marshalls, and the boundary between these 

currents is known to shift during the seasons. There is 

no large island group between the northern Marshalls 

and the American mainland along the path of the North 

Equatorial Current. There is, therefore, no significant 

source of flora nearby or up current (east).

The Marshall Islands lie in the trade wind belt, and 

prevailing winds blow from the east or northeast. As 

a result of these constant winds, there are clear vegetational differences between the windward and leeward 

islands, and even between the windward and leeward

sides of single islands (Fosberg, 1956). From June to 

September, calms or weak variable winds may occur. 

Storms and, rarely, typhoons usually come from the 

south.

The climate of the Marshall Islands is characterized 

by rather uniform temperatures and by southward-increasing precipitation (Fosberg, 1956). In the north, 

Eniwetok receives a mean annual rainfall of 50 inches, 

whereas farther south Ujelang receives 77 inches and 

Kwajalein 96 inches. The months during which the rainfall gradient is most obvious are December through 

February, when the southern Marshalls receive roughly 

three times more rain than the northern Marshalls. 

Variation in annual and monthly rainfall is very great; 

the annual rainfall on Eniwetok ranged from 48 to 83 

inches within a 3-year period (years not specified; Fosberg, 1956).
1142 BIKINI AND NEARBY ATOLLS, MARSHALL ISLANDS

CONTOURS, IN FATHOMS

FIGURE 336.—Generalized depth chart and section of Eniwetok Atoll. 

From Ladid and Schlanger (1960, fig. 285).

Corresponding to the north-south rainfall gradient in 

the Marshalls is a proportionate trend in luxuriance 

of vegetation. Fosberg (1956, p. 18'7) divided the vegetation of the northern Marshalls into four east-west belts 

(fig. 338).

Vegetation zone 1—the northernmost—comprises the 

Taongi Atoll and Wake Island. In the aridity of this 

belt, the coconuts do not thrive, and the vascular flora is 

very poor in species (nine native species). The atoll 

vegetation is sparse, and there is much open ground.

165°20'

11° 

40'

B 1 K 1 N 1 ATOLL

BIKINI ISLANOyV) 

Drill holes 2A and 2B I'i

FIGURE 337.—Map of Bikini Atoll, showing location of drill holes 2A

and 2B.

Only one atoll, Bikar, is in vegetation zone 2. Though 

coconut trees grow there, they fail to produce normal 

nuts in dry years; consequently the environment is considered to be marginal for that species. As in vegetation 

zone 1, the flora is very small; according to Fosberg 

(1956), only eight species of native vascular plants are 

known from Bikar but pure Pisonm forest with closed 

canopy occurs, which gives the atoll a more luxuriant 

aspect than on the islands of zone 1.

168° 170° VEGETATION ZONES AND FLORA

^UJELANG 

ATOLL

^ENIWETOK 

<Qj ATOLL

Current drift

BIKINI ATOLL

o

AILINGIN

Direction of trade

RONGELAP 

ATOLL

•B'-CP °«"<

ATOLL

t

UJAE ATOLL ^

\k

WOTHO

; ATOLL

KWAJALEIN 

ATOLL

\__^ ^^"^ \

\

LAE ATOLL V

^TAONGI

ATOLL

winds

LIT 

3ERIK 5

1 ^-

TAKA ATOLL

JEMO 1^ C

LIKIEP ATOLL

q

c

ERIKUB

ATOLL

BIKAR

£, ATOLL

IRIK ATOLL

AILUK

ATOLL

MEJIT 1

WOTJE ATOLL :3

•N MALOELAP

°" ATOLL

^

1

2

3

4

Only 9 native species of vascular

Climate arid.

Only 8 native species of vascular

plants; coconuts grow. Climate

arid.

32-42 native species of vascular 

plants. Climate semiarid.

42 native species of vascular 

plants. Climate mesic.

0 50

11,11!

150 MILES

FIGURE 338.—Map of northern Marshall Islands, showing vegetation zones. From Fosberg (1955b).
MIOCENE POLLEN AND SPORE FLORA OF ENIWETOK ATOLL, MARSHALL ISLANDS 1143

The third vegetation zone described by Fosberg includes seven atolls that lie along an east-west line at lat 

11°30' N., from Eniwetok and Bikini on the west to 

Utirik on the east. These atolls have larger floras and, as 

compared with those farther north, include more types 

of forest, such nsPisania. Cordia, and Pemphis. as well 

as mixed forest. Eniwetok has a flora of 32 indigenous 

species, according to F. R. Fosberg (oral commun., 

1963), and Bikini has about 28 native species (Fosberg, 

1956).

In Fosberg's fourth, and southernmost, vegetation 

zone are 10 atolls, including the largest one in the 

northern Marshalls, Kwajalein. These atolls have a more 

luxuriant aspect; their diverse vegetation includes all 

those types present on the more northern atolls and a 

few others, such as pure forests of Ochrosia. Fosberg 

listed 42 indigenous vascular species for this zone.

The existing vascular flora of Eniwetok totals 95 

species or minor taxa, according to St. John (1960, p. 

314), but many are not indigenous; 27 are adventive 

weeds, 26 are cultivated plants, including both food 

crops and ornamentals, and seven are species known 

only from seeds drifted up on the beaches. Of the 42 

native species or minor taxa listed by St. John, four are 

endemic to Eniwetok and belong to the genus Pandanus. 

F. R. Fosberg (oral commun., 1963), however, suggested that these four and four others are merely forms of 

the species Pandanus tectoriu-s. St. John's (1960) enumeration of this flora, which is a summary of his own 

and earlier collecting by others on the atoll, is given 

below as modified by F. R. Fosberg (oral commun., 

1963) ; taxa which St. John or Fosberg considered 

native to Eniwetok are marked with an asterisk; these 

include 29 vascular genera and 32 species.

Polypodiaceae

*Polypodium scolopcndria, Burni. f. (fern) 

Pandanaceae

*Pandanus tectorius Soland. (screw pine) 

Gramineae

Cenchrus broumii R. & S. (grass) 

C. cchinatus L. (grass) 

ChlorisinflatalLirik.. (grass) 

Cynodon dactylon (L.) Pers. (grass)

Dactyloctcnium acgyptium (L.) Aschers. & Sehweinf. 

(grass)

*Digitaria pruriens (Trin.) Buese. (grass) 

Eleusinc indica (L.) Gaertn. (grass) 

Eragrostis amabilis (L.) Wight & Arn. (grass)

*Lepturus repcns (Forst. f.) Rr. Br. var. repens, var. *occidentalis Foslberg, and var, *septentrionalis Fosberg. 

(grass)

Sctaria rcrticillata (L.) Beauv. (grass)

Sorghum bicolor (L.) Moench. var. tcclmiciim (Koem.) 

Jav. (sorghum)

*Thuarca inroluta (Forst. f.) R. & S. (grass) 

Tricachnc insularis (L.) Nees. (grass) 

Tricholacna rosca (Willd.) Hitchc. (grass) 

Zea mays L. (corn)

Cyperaceae

Cypcrus odoratus L. (sedge) 

Cypcrus javanicus Houtt. (sedge)

*Fim'bristyJi8 atollcnste St. John (sedge) 

Palmae

Cocos tmcifcra (coco palm) 

Liliaceae

Alliitm cepa- L. ( ?) (onion) 

Amaryllidaceae

CrinuniasiaticumLi. (?) (spiderlily) 

Taccaceae

Tacca Icontopctaloidcs (L.) Ktze. 

Ilrticaceae

*Fleurya rndcralis (Forst. f.) Gaud. 

Olacaceae

*X\nicnia amcricana L. 

Amaranthaceae

Achyranthcs aspcra L.

*A. vclutina H. & A. 

Amaranthus dubius Mart, (pigweed) 

A. viridits L. 

Nyctaginaceae

*Bocr1iavia repcns L.

*B. tctrandra Forst. f. 

MiraT)ills jalapa L.

*Pisonia grandis R. Br. 

Portulacaceae

*Portnlaca lutca Solander. 

P. olcracca L. 

"P. samocnsis v. Poelln. 

Lauraceae

*Cassytlia fill for mis L. 

Cruciferae

Brassica olcracca L. capitata (cabbage)

B. pckincnsis (Lour.) Rupr.

Raphanus sativus L. (radish)

Cacsalpinia bonfluc (L.) Roxb. 

Leguminoseae

*Canavalia microcarpa (DC.) Piper 

Phascolus vulgaris L. (bean)

*Vigna marina (Bunn.) Merr. 

Zygophyllaceae

*Tri1)ulU8 cistoidcs L. 

Surianaceae

*Suriana, mar it i ma L. 

Euphorbiaceae

^Euphorbia cJiamissonis (Klotsch & Garcke) Boiss.

E. hirta L.

E. thy mi folia. L.

Phyllanthits amarus Schum. & Thonn.

Ricinus communis L. (casterbean) 

Tiliaceae

*Triumfctta, procitmbcns Forst. f. 

Malvaceae

Malrastrum coromandcUanum (L.) Garcke

*8ida fallax Walp. 

Caricaceae

Carica papaya L. (papaya) 

Lythraeeae

*Pcmphi8 aciditla J. R. & G. 

Rhizophoraceae

RJiisophora mangle L. (mangrove)
1144 BIKINI AND NEARBY ATOLLS, MARSHALL ISLANDS

Combretaceae

*Terminalia samoensis Rechinger 

Apocynaceae

*0chrosia oppositifolia (Lam.) K. Schum. 

Convolvulaceae

*Ipomoca pes-caprae (L.) Sweet ssp. brasiliensis (L.)

v. Ooststr. 

/. purpurea (L.) Roth.

*/. tuba, (Schlecht.) G.Don. 

Boraginaceae

*Cordia subcordata Lam.

*Tournefortia argentea, L. 

Solanaceae

Nicotiana glauca Graham

Physalis angulata L.

Solatium lycopersicum L. 

Rubiaceae

*Gucttarda spcciosa L.

Morinda citrifolia L. 

Cucurbitaceae

Citruling vulgaris Schrad. (watermelon)

C iicu mis melo L. (cantaloupe)

Cucurbita maxima Duch. (squash) 

Goodeniaceae

*Scacrolataccada (Gaertn.) Roxb. 

Compositae

Conyza bonarlcnsis L. 

Lactnca sativa L. (lettuce) 

Pluchca indica (L.) Leg's. 

P. ordorata (L.) Cass. 

Veronia cincrca (L.) Less.

*Wcdclia bi flora (L.) DC. 

Zinnia elegant Jacq. (?) (zinnia)

Eniwetok Atoll has a land area above high tide of 

only about 2.5 square miles, and, thus, the habitats and 

area capable of supporting vascular plants are limited. 

St. John (1960, p. 314) described the only habitats as 

including "outer beaches of coral rock or coral gravel, 

inner beaches of coral sand, small coral sand dunes, 

coral gravel flats, and coral sand flats." Today there 

are no fresh ponds or central hollow depressions in 

the middle of the islets, nor is there any dark topsoil. 

The present vegetation on the large islands is reduced 

to a few sickly coconut trees and a small number of 

weedy plants, the original vegetation having been almost completely destroyed during World War II (Fosberg, 1956) and subsequent bomb testing.

The highest elevation above mean sea level at Eniwetok is about 12 feet. Ground water in existing wells on 

Eniwetok contains 88-300 ppm chloride (Fosberg, 

1956).

Bikini has a land area above high tide of about 2.4 

square miles. As on Eniwetok, the greater part of the 

original vegetation has been destroyed by man, and only 

on the small islets can relics of the original flora be 

observed. Fosberg (1956) and Taylor (1950) concluded 

that the original flora of Bikini was much like that of 

Eniwetok, but two genera, Tribulm and Euphorbia,

native to Eniwetok have not been found on Bikini. 

Tinbulus is doubtfully native to Bikini, and Euphorbia 

was presumably present but not found (F. R. Fosberg, 

written commun., 1964).

METHODS OF STUDY

The collection of cuttings from drill holes and methods of estimating depth intervals for the cuttings were 

described by Ladd and Schlanger (1960, p. 867). The 

chips of cuttings, though somewhat soft when wet, are 

too large to have been derived from the drilling mud. 

The samples were washed before preparation, to reduce 

the possibility of contamination. The surfaces of core 

samples were chipped clean before preparation.

TREATMENT OF FOSSIL SAMPLES

All dry-sediment fractions used for pollen analysis 

were weighed and the volumes of sediment were estimated before preparation. Only very small pieces of 

cuttings were available for analysis and, with two exceptions, less than 1 gram of sediment per cutting sample was used. (See list of cuttings used, table 1.) Core 

materials were not limited as to sample size, and 13-33 

grams of each sample were used (table 1).

Methods of sediment preparation employed in this 

study are similar to those I used with Kapingamarangi 

sediments (McKee, Chronic, and Leopold, 1959, p. 539). 

The technique involved dissolving a measured dry 

weight of sediment in a 10-percent HC1 solution and 

counting pollen, spores, and algae in a measured fraction of the suspended organic residues. To accomplish 

this, slides were prepared from aliquot fractions of the 

total organic residues, and the exact area of the slide 

examined for each tally was noted. Tallies were then 

multiplied by constants according to the fractions observed, and the number of pollen and spore grains and 

(or) algal colonies per gram was extrapolated (tables 

1,3) The calculated number of pa/lynomorphs per gram 

of sediment (table 1) should be considered only a general indication of pollen density.

Tallies of pollen and spores included more than 200 

specimens where adequate material was available; 

counts of less than 200 grains included all the pollen 

and spores that could be found in the preparation.

After a first aliquot slide was made, the remaining 

materials of each sample were acetylated for 2 minutes 

in a boiling-water bath (Faegri and Iversen, 1964, p. 

71), and a second slide was made. In certain algae-rich 

sediments, such as sample D1200-9 at depths of 2,490- 

2,500 feet in drill hole E-l, a second acetylation was 

done for an additional 2 minutes and a third slide made. 

As would be expected, prolonged acetylation definitely
MIOCENE POLLEN AND SPORE FLORA OF ENIWETOK ATOLL, MARSHALL ISLANDS 1145

TABLE 1.—Calculated number of pollen, spores, and Chroococcalean 

algal colonies per gram of sediment, Eniwetok and Bikini drift 

holes

[Samples are cuttings, except those marked by asterisk (*). which are from cores]

Depth

(ft)

Sample

Number Dry 

weight 

(grams)

Pollen 

and 

spores

Algal colonies

Less than More than 

12 cells 12 cells

Drill hole F-l (Eniwetok)

Post-Miocene: 

170-191---— fififl— R9^

Miocene: 

670-680,..—.

SI A-S9fl

820-830---—.

830-840--.—.

840-850 __.--.

850-860

1,232-1,248.—-.

1,718-1,740..—.

i Q7ft— 9 flfM

9 RR9— 9 ftR7

Eocene: 

3,054-3,055--— O OKft— ^l ^W

3,655-3,665. —— .

o Ofi3— ^l ORS

4,197-4,222. _ — .

4,316-4,341. —— .

4,406-4,431.—— A RfW A KOK

4,528-4,553———

—— F-l-1-2*

..... 2-1*

—— D1215-A

.—— B

C

.... . D

..... E

.... . F

..... F-l-3-3*

4— 1O*

.... . 5-6*

..— 6-10*

F-l-7-7*

o_1 *

O-4*

..... 10-1*

-— 11-33*

.—— 12-13*

— .. 13-2*

1A_ OQ*

.— - 15-12*

28

32

.17

2.17

.17

1.09

.17

33

28

28

24

25

24

21

17

24

30

23

24

13

8,300 ———————————

4,650 ——— ———————--

102,000 ———————————

12,600 ————————————

3,295 — ——— —————————

2 6 25

Drill hole E-l (Eniwetok)

Miocene:

870-880..- —

880-890.- — ..

2,440-2,450..—

2,450-2,460...-

2,460-2,470.....

2,470-2,480...-

2,480-2,490...-

2,490-2,500.- —

2,500-2,510..—

Eocene:

4, 078-4, 100.. ...

.... D1200-1

2

--„ 3

_.- E-l-1-8*

.... D1200-4

5

6

7A

8

9

10B

3-17

0.02

.20

.25

23

.33

.60

.23

.31

.23

.04

.73

27

26

21,200

545

36

72

169

960

180

120

12

8

150 ...

85,250

128 ...

10, 618

6,580

2,160

10,440

5,460

5,630

999

2,090

1,100

539

640

1,080

650

525

82

Drill hole K-1B (Eniwetok)

Miocene: 

694.8-705.3-.—

726.3-736.8.,.-

736.8-747.3.- —

747.3-757.8..—

799.8-810.3-- —

810.3-820.8--.-

820.8-831.3___-

841.8-852.3.- —

852.3-862.8- — .

862.8-873.3.- —

873.3-833.8.- —

883.8-894.3..—

894.3-904.8-..-

.-. D1381-1

--.- 2

3

4

5

6

---- 7

-.-. 8

g

.... 10

11

12

13

0.4 ...-.

.5 .--..

.17 ..--

.16 ... ..

.16

.15 ... ..

.16 .....

.50 .....

.20

.22-.

.08

.18

.33 .....

75 . ——— ——— — ———— -_

15 — ———— ... ———————

14 — — — — — — — —

25 ... . ..... ......... ...

6 ............ — .........

Drill hole 2A (Bikini)

Miocene:

929-935.5... 

935.5-946.0.

D1416-1 

2

2.1

2.0

reduced the amount of Chroococcalean algae in the 

material, making it possible to observe more pollen per 

slide. However, tallies on which the calculated number 

of algal colonies and pollen and spores per gram of 

sediment was based were carried out on the first, unacetylated, aliquot slide to simplify calculations for

336-3SS O—69——(3

the pollen and not modify the real number of algae 

present. The first acetylation tended to break up the 

large colonies of algae present, so that a tally of this 

material yielded a higher number of smaller colonies 

than did the first unacetylated slide. The second acetylation actually tended to destroy the algal cells, and thus 

the ratio of algae to pollen and spore grains was lower 

in the third slide than in the first and second slides.

Mounting medium was glycerine jelly for about half 

the slides; poly vinyl alcohol was used for the remaining 

material; all fossil materials were stained with Safranin 

O. Visibility of the palynomorph structures is good in 

many of the glycerine jelly slides and poor in most of 

the material mounted in polyvinyl alcohol.

Location of the figured specimens on the microscope 

slides are given as coordinates in the plate descriptions. 

Though the coordinates refer to the mechanical stage 

readings on a Zeiss photomicroscope in the U.S. Geological Survey pollen laboratory in Denver, the specimens can be relocated on another microscope by calculating the distances from the center of a standard 1X3 

inch slide. On our photomicroscope, the position of that 

center is 108.2 (horizontal axis) X 12.4 (vertical axis), 

and the coordinates increase toward the left and upward 

on the slide; coordinate readings cited here pertain 

when the slide label is placed on the left of the stage.

Slide designations begin with the USGS paleobotany 

locality number prefixed with a "D" for the Denver 

laboratory, and following a hyphen is the sample designation (a letter or a number) if one has been assigned; 

the last number which is in parentheses is the slide number. Slides of the fossil material described here are 

stored at the USGS pollen laboratory in Denver, Colo. 

Preparations from core samples carry the original core 

numbers assigned by Ladd and Schlanger (1960).

REFERENCE COLLECTION OF RECENT POLLEN

Pollen collections representing nearly all the higher 

plant genera listed in Kanehira's (1933) "Flora Microiiesia'1 ' were obtained from sheets in the U.S. National 

Herbarium and consisted of 600 species in about 500 

genera. Pollen of each species was prepared by acetylation. Two sets of photographs at X 1000 were made; 

one set of pictures was organized taxonomically and 

the other was classified according to pollen morphology. 

The morphological file was used as a key revealing possible affinities of the fossil pollen to guide the selection 

of reference material for detailed comparisons.

As a supplement to the modern pollen collection from 

Micronesia just described, I used a modern pollen collection of about 3,000 selected species of woody plants 

from Eastern Asia and the United States in the U.S. 

Geological Survey pollen laboratory in Denver. The
1146 BIKINI AND NEARBY ATOLLS, MARSHALL ISLANDS

photographic key to this collection was useful in checking the range of morphological variations within particular genera or families.

Modern pollen preparations are referred to here by 

their accession number which begin with "P"

COMPOSITION AND RELATIONSHIP OF 

FOSSIL FLORA TO RECENT FLORA

The following systematic list summarizes the relationships of the Miocene pollen, spore, and organic algal 

remains. Forms are identified to family and living 

genus, where possible. For some forms no affinity with 

living plants can be cited, nor can several unknown but 

distinctly different pollen or spore forms be recognized 

under a single morphological category or form species. 

For convenience in referring to these unknown forms, 

they have been given morphological code designations 

according to the system suggested by Tschudy (1967), 

which consists of three parts. The first part indicates 

aperture type and number, for example, C3 (tricolpate), 

Tl (trilete), M (monolete), and P3 (triporate); the system is adapted from J. Troell-Smith (in Faegri and 

Iversen, 1964). The second part describes the sculpture 

of the grain: sm, smooth; r, rough or psilate; rt, reticulate ; p, projections larger than 1 micron; and st, striate. The third part represents an accession number for 

the particular species in the combined aperture and 

sculpture category.

Systematic list of Miocene plant microfossils from Eniicctok

Algae, Chroococcales: 

Chroococcaceae:

Gloeothece type

Gomphosphaeria type

Glococapsa type

Coelosphacrium type

Aphanocapsa type 

Algae or Protista, Hystrichosphaeridae:

Pterospcrmopsis cf. P. ginginensis Deflandre & Cookson 

Micrhystridium temiissimnm Deflandre 

Cysts, undet. 

Spores of Pteridophyta: 

?Polypodiaceae:

M-sin(l)

Tl-sm(2) 

?Hyrnenophyllaceae :

Trichomancs type, Tl-p(2) 

?Pteridaceae:

Tl-r(3)

Pollen of Monocotyledonae: 

Pandanaceae:

Pandanus

Monocotyledenous pollen of uncertain family affinity: 

?Palmae:

Livistona type

Ci-sm(2), monosulcate 

Pollen of Dicotyledonae: 

Nyctaginaceae:

Pisonia cf. P. yrandis R. Br. 

Euphorbiaceae:

Acalypha 

Malvaceae:

Thcftpcsia cf. T. lampas (Cav.) Dalz.

Systematic list of Miocene plant microfossils 

from Eniicetok—Continued

Pollen of Dicotyledonae—Continued 

Sonneratiaceae:

Sonneratia cf. 8. alba J. Sm. 

Rhizophoraceae:

RhisopJiora cf. R. apicitlata Bl.

Rltisophora cf. R. mucronata Lam.

Rhizophora sp.

Bruffiiiera cf. B. gymnorliiza- (L.) Merr.

Ceriops cf. C. tagal (Perr.) C. B. Rob. 

Combretaceae:

Terminalia cf. T. catappa L.

cf. Combretum

Lumnitzera, cf. L. littorea (Jack.) Voight 

Myrtaceae:

cf. Eugenia 

Boraginaceae:

Tournefortia cf. T. arffentea- L.

Cordia cf. C. subcordata- Lam. 

Verbenaceae:

Avicennia cf. A. marina Forsk. 

Rubiaceae:

Ixora cf. / casci Hance

Gardenia cf. G. grievei Home

Randia cf. R. cocliincliincnsis (Lour.) Merr.

cf. Guettarda

cf. Timonius

Morinda cf. M. citrifolia L.

cf. Mussaenda

cf. Scyphiphora

Dicotyledonous pollen of uncertain family affinity : 

Cplpates:

Cs-r(l), ?Verbenaceae, Callicarpa type

C3-sni(3), ?Gesneriaceae, Cyrtandra- type

C3 undet.

C4-r(l), ?Ca|llitrichaceae, Callitriclic type

C4 and C5 undet. 

Porates:

Ps-sm(3)

Pa undet.

P2-sm (1), ?Moraceae, Malaisia type

P4-p(l), ?Simarul>aceae, Picrodendron type

Poo-(l) 

Colporates:

CsPs-sm^lO), C3P8-sm(8) ) ?Elaeocarpaoeae, Elaeocarpus type

CsPs-sm (9)

C3P3-sm(7), ''Rhizophoraceae, Gynotrochcs type

CsPs-rdl), ?Leguminoseae, Sophora type

C3P3-r(9), ?Hippocrateaceae, Solatia type

C3P3-st(l), ?Simarubaceae. Bnicca type

C3P3-r(10)

C5Po-r(l), ?Rubiaceae, Coprosma type

FLORISTIC COMPOSITION

The Miocene flora of Eniwetok includes 56 kinds of 

plants; of these, five are algae, four are pteridophytes, 

three are monocotyledons, and 44 are dicotyledons. 

Seventeen angiosperm genera are definitely identified, 

including one monocot and 16 dicot genera. One algal, 

one monocot, and 10 dicot families are recognized. 

Twenty-four pollen types are definitely assignable to 

dicot families, but only one monocot and five algal types 

can be identified to living family.

The flora is overwhelmingly dicotyledonous and all 

identified genera are trees or shrubs. Rubiaceae is the 

best represented family, with four genera and eight 

pollen types; next best represented are Rhizophoraceae 

with three genera and six pollen types,; Combretaceae,
MIOCENE POLLEN AND SPORE FLORA OF ENIWETOK ATOLL, MARSHALL ISLANDS 1147

with two genera and three pollen types; and Boraginaceae, with two genera and two pollen types.

Numerically, Rhizophoraceae (Rhizophora) pollen 

grains vastly outnumber pollen or spores of all other 

groups. The only other pollen form that was at all 

abundant in the tallies (table 5) was that referred to 

Elaeocarpiis type (code species C3P3-sm(10)). More 

abundant than pollen and spores of vascular plants in 

drill hole E-l were the remains of Chroococcalean algae, 

which numbered 5,000-10,000 colonies per gram of sediment. Relative abundance of plant materials is discussed 

on p. 1152.

The Pteridophyta are poorly represented in the 

flora; only four spore types were found. The form having the widest stratigraphic occurrence was a simple 

monolete smooth spore (M-sm(l), pi. 305, figs. 1, 2) 

that very probably represents a member (or members) 

of the Polypodiaceae. This fossil is unlike the spores of 

Polypodium scolopendria, which is the only Polypodiaceae now known to grow on Eniwetok.

Of the three monocot pollen types found, only 

Pandanus pollen was identified (pi. 305, figs. 16,18,19). 

Pandanus, known as screw pine, now grows on Eniwetok 

and is distributed throughout the Indo-Pacific region, 

where it occupies many habitats from coastal to 

montane.

Fossil Pisonia pollen of the P. grandis R. Br. type 

(pi. 306, figs. 1, 5) was compared with modern collections of P. grandis R. Br. and P. imibellifera (Forst.) 

Seem., which were the only two species of the genus 

listed by Kanehira (1933) as present in Micronesia. 

Pollen of these two species is easily distinguished, and 

only P. grandis seems to be represented now on Eniwetok as a coastal forest tree; it is common at low elevations on South Pacific islands.

The Sophora-ty}& pollen (pi. 306, figs. 6-8) was 

compared with two collections of S. tomentosa L. and 

one of S. secundiftora. Its resemblance to /S. tomentosa 

L. is striking, but because the morphology involved is 

not particularly unusual among dicot pollen types there 

is no certainty as to either the family or the generic 

affinity. Of 60 other leguminous genera considered, 

Sophora is the only form similar to the fossil. The 

genus grows on many Pacific islands today; the species 

8. tomentosa L. was recorded in the northern Marshalls 

at three localities by Fosberg (1955a, p. 12), who susspects that the plant is native to those islands. He 

observed that the plant is a common pantropical strand 

species.

A single fossil specimen of Acalypha (pi. 306, figs. 9, 

10) is extremely similar to a modern collection from 

Ponape at an elevation of 400 feet which was identified 

as Acalypha sp. by S. F. Glassman. In comparing the 

fossil with modern pollen of five other Acalypha species

(only one of these was from Micronesia), it was evident 

that there is considerable pollen morphological variation 

within the genus. The fossil is somewhat larger than 

the modern pollen of Acalypha^ but otherwise it is 

almost identical with the Glassman collection. Acalypha 

was not reported from the present Eniwetok flora by 

St. John (1960), but it grows on Arno Atoll and in the 

northern Marshalls, where it was introduced (Fosberg, 

1955a). It is common throughout Malaysia, New Guinea, 

Melanesia, west through Polynesia to the Austral 

Islands, in the high islands of the Carolines, and on 

low Kayangel Atoll in the Palaus (F. R. Fosberg, oral 

commun., 1965).

Probable Oallitriche pollen was unexpected in this 

flora; the genus is generally characterized as a cosmopolitan fresh-water annual in the temperate and tropical zones, but no record of the genus, fossil or living, 

is known from Micronesia. A living species in New 

Guinea was reported by Merrill and Perry (1941); 

many species occur in New Zealand and Australia, some 

of which may tolerate brackish water, since they are 

reported from harbors and barrier reef islands.

/Solatia-type, pollen (pi. 306, figs. 12, 13), of which 

two specimens were found at Eniwetok, is probably a 

member of the family Hippocrateaceae. The family 

does not now grow on Eniwetok, but Kanehira (1933) 

reported Solatia and Hippocratea (referred to Loesneriella by A. C. Smith) from Yap and the Palau Islands, 

and a third genus, Salacicratea, with an endemic species, 

in the Palaus; these plants are described as climbing 

shrubs. I have compared the fossils with material of 

the first two but not with that of the third. Van Campo 

and Halle (1959), in describing the range of pollen 

morphology in the family Hippocrateaceae, indicated 

that many intermediate morphological pollen types occur within the family. For lack of enough comparative 

material, the fossils here reported are only tentatively 

assigned to Solatia.

Pollen assigned to Thespesia (pi. 306, figs. 22-24) 

includes only two specimens, and both resemble the 

Lido-Malayan species T. Pampas (Cav.) Dalz rather 

than T. populnea (Linn.) Soland. ex Corr. The latter 

species is the only member of the genus now known in 

Micronesia. Thespesia populnea was described by Kanehira (1933) as being of broad paleotropical distribution 

in coastal forests. Thespesia is not represented in the 

living Eniwetok flora, according to St. John (1960), 

but another malvaceous genus, Sida, now grows on the 

atoll and is considered native there.

Modern pollen of the genus Sonneratia (pi. 307, figs. 

7-11, 22-24) has a unique morphology among angiosperm pollen types. The fossil material assigned to this 

genus (pi. 307, figs. 1-6, 12-21) varies greatly in size
1148 BIKINI AND NEARBY ATOLLS, MARSHALL ISLANDS

and in degree of folding and may represent more than 

one species. The fossils compare well with two collections of modern S. alba J. Smith pollen. Five species of 

the genus exist, according to Mahabale and Deshpande 

(1957, p. 52), and, except for S. alba, which grows in 

Micronesia as far east as the southern Marshalls, are 

of Indo-Malayan distribution (fig. 339). On Arno 

Atoll, about 5° south of Eniwetok, S. alba grows in association with Lumnitzera in mangrove depressions in 

the central higher parts of the atoll (Anderson, 1951). 

Sonneratia also grows on Jaluit, according to F. R. 

Fosberg (written commun., 1964).

Modern distribution of the genus Sonneratia is shown 

in figure 339, in which the localities of individual herbarium collections are indicated. The known fossil occurrences (fig. 339) include one recorded in southern 

India—fossil wood thought to be of Eocene or late 

Tertiary age (Ramanujam, 1957). A fruit from the 

Deccan flora (Eocene or younger Tertiary) (Sahni, 

1943; Mahabale and Deshpande, 1957) and a flower 

from the Deccan flora (Shukla, 1944) may be related 

to Sonneratia also. Fossil pollen occurrences shown in 

figure 339 include not only those on Eniwetok but also 

those on Fiji (p. 1163-1164), Borneo (Muller, 1964), 

and Palau India.

Rhizophoraceae pollen (pi. 308), which is so abundant in the Miocene sediments, is of five types: two primary Rhizophora types (cf. R. apiculata Bl. and cf. 

R. mucronata Lam.) and Bruguiera, Ceriops, and cf. 

G-ynotroches. Modern comparative material includes 

pollen of R. mucronata (three collections), R. apiculata 

(two collections), a hybrid of R. mucronata X R. apiculata (one collection), R. mangle L. (one collection), 

B. gymnorliiza (L.) Merr. (three collections), Ceriops 

tagal (Perr.) C. B. Rob. (two collections), and G. axillaris Bl. (one collection). These collections include all 

the living genera of the family and all the Micronesian 

species reported by Kanehira (1933). Fossil material 

that compares favorably with R. apiculata is the most 

frequent pollen type (pi. 308, figs. 1-8), but fossil R. 

mucronata types are represented (pi. 308, figs. 20, 21, 

26, 27). Also present are some forms (pi. 308, figs. 20, 

21, 26) which are identical with the modern hybrid 

material of R. mucronata X R. apiculata. Kanehira 

(1933, p. 212) reported that R. mucronata and R. apiculata are widely distributed in the paleotropical zone and 

often occur together; he noted their presence on Ponape 

and Yap. R. apiculata is reported on Kusai but is not 

known from the Marshall Islands. R. mucronata now

120°

FIGURE 389.—Distribution of modern and fossil Sonneratia. Circles, modern distribution (Mahabale and Deshpande, 1957). Crosses, Tertiary 

occurrences. Fossil wood in southern India is of Eocene or younger Tertiary age (Ramanujam, 1957) ; pollen from Borneo is Miocene and 

Pliocene (Muller, 1964), and pollen from Fiji (,p. 1164) and from Eniwetok (p. 1168) is Miocene..
MIOCENE POLLEN AND SPORE FLORA OF ENIWETOK ATOLL, MARSHALL ISLANDS 1149

ranges eastward into the southern Marshalls (Fosberg, 

1960). R. mangle, now of New World and eastern Pacific distribution, was reported by St. John (1960) to 

have been planted on Eniwetok in 1954; it is therefore 

exotic to the atoll. None of the fossil forms resemble 

the modern pollen of R. mangle (pi. 308, figs. 36, 37).

Fossil pollen assignable to Bruguiera (pi. 308, figs. 

31, 32, 40) occurs infrequently in the Miocene sediments, 

though some of the forms tallied as Elaeocarpus type 

(table 8) may be weathered specimens of Bruguiera. The 

genus is Indo-Pacific; it now grows in the mangrove 

depressions on the higher parts of the southern Marshall 

Islands and on Lae, Utirik, Ailuk, and Bikini in the 

northern Marshalls (Fosberg, 1947, 1960).

Fossil pollen of Ceriops is comparable with G. tagal 

(pi. 308, figs. 41-43), which is the only species of that 

genus now in Micronesia. However, comparisons with 

C. Toxburgli'mna Am. of India and Malaya were not 

made, so subgeneric affinities are not clear. C. tagal is 

Indo-Malayan and ranges eastward as far as the western 

Carolines.

A few fossil pollen are similar to the genus Gynotroclies (pi. 308, figs. 44, 45), but the genus is not identified with certainty in this flora.

All the living relatives of the identified Ehizophoraceae are trees occupying swamp habitats in the intertidal coastal zones or in mangrove depressions (Fosberg, 

1947). Gynotroches, however, is an upland tree.

Of the Coinbretaceae forms represented in the Eniwetok flora, Lumnitzera pollen is the most abundant 

(pi. 309, figs. 22-26) ; the fossils are identical with the 

pollen of L. littorea (Jack.) Voigt, and are quite different from the pollen of L. racemosa Willd. (pi. 309, fig. 

40). L. littorea is the only species of the genus now in 

Micronesia; it is a small- to medium-size tree that grows 

in association with Rhizophora in mangrove swamps in 

the Indo-Malayan. area, but in the southern Marshalls it 

grows with Bruguiera and fionneratia in mangrove 

depressions.

At least two other types of Coinbretaceae pollen were 

found in the Miocene flora; Terminalia cf. T. catappa 

L. (pi. 309, figs. 1-5) and a probable Combretum type 

(pi. 309, figs. 6, 7). T. samoensis, which now grows on 

Eniwetok, does not compare favorably with the fossil 

Terminalia pollen. T. catappa is a large tree in the 

coastal forests of the Caroline and Mariana Islands, 

and it is introduced in the Marshall Islands (Fosberg, 

1956, p. 288).

The family Myrtaceae, which is certainly represented 

by the fossil pollen shown on plate 310, figures 1 and 2, 

is not now represented in the Eniwetok vegetation. Unfortunately, only one fossil pollen grain assignable to 

that family lias been found in the Miocene sediments.

Determination of Myrtaceae genera on the basis of 

pollen type is not a very good procedure because of the 

large number of similar pollen types in the family; for 

this reason comparisons with living genera made on the 

basis of pollen are arbitrary. In Micronesia, one would 

expect Eugenia and Decaspermum; of these the fossil 

in question is somewhat like Eugenia, although no good 

matching species could be found, but it is more like pollen of Rhodamnia (pi. 310, fig. 3). Eugenia is of worldwide distribution, and many endemic species inhabit 

Micronesia.

Tournefortia pollen of the T. argentea L. type (pi. 

310, figs. 4, 5) occurs occasionally in the fossil flora; 

T. argentea is a small tree of the coastal forests and 

sandy beaches of Micronesia, and it now grows on Eniwetok Atoll.

Pollen assignable to Cordia cf. C. subcordata Lam. 

was found at two levels in hole F-l. This tree, which 

now grows on Eniwetok, is a highly variable widely distributed Indo-Pacific and Micronesian species.

Fossil Avicennia pollen in the flora (pi. 310, fig. 10) 

is extremely similar to that of A. marina Forsk., but is 

unlike that of A. nitida. A. marina grows in mangrove 

swamps in China, Indo-Malaya, the Palaus, and as far 

east as Guam. According to F. E. Fosberg (written 

commun., 1964), it does not grow in the Marshall Islands 

today.

The Eubiaceae pollen types in this flora are many and 

varied. Fossil Morlnda pollen (pi. 311, figs. 1, 2, 9, 10) 

compares especially well with that of M. citrifolia var. 

bracteata, Eoxb., which ranges from India to the 

Eyukyus and occurs on Amboina in the Moluccas. The 

fossil pollen compares fairly well with M. citrifolia L., 

which now grows on Eniwetok but may not be native 

there; Fosberg (1956) thought the species might have 

been introduced by aborigines.

Pollen that is suggestive of Mmxaenda frondosa L. is 

present in the Miocene flora (pi. 311, figs. 3, 4), as are 

forms that are similar to Scypliiphora. liydrophyllacea 

Gaertn. (pi. 34, figs. 15,16). Both species occur in central and western Micronesia today.

Miocene Randia pollen from Eniwetok is sparse, but 

several specimens have been found. They are very similar to pollen of the modern R. cochinchinensi* (Lour.) 

Merr. of the Carolines and Marianas except that they 

are somewhat larger (pi. 310, figs. ?>1, 32). /?. cocliinchi-nenxi* is a small tree of the coastal forests; the genus 

Randia is not found in the living flora of Eniwetok, but 

R. graeffi (equals cochincliinensis] was collected on 

Arno Atoll by Anclerson (1951).

Pollen assigned to Ixora (pi. 310, figs. 13-15) was 

compared with that of only one living species (/. casei 

Hance), but they are a close matoh, and the morphology
1150 BIKINI AND NEARBY ATOLLS, MARSHALL ISLANDS

of Ixora is apparently unique among genera of the 

Rubiaceae. The genus includes several shrub and forest 

tree species endemic to the Caroline Islands. One occurrence of Ixom casei in the Marshall Islands (Likiep 

Atoll) was noted by Fosberg (1955a, p. 20), who termed 

the species an introduced plant but thought it might be 

native to the southern Marshalls.

Pollen that probably represents the genus Timonius 

(pi. 310, figs. 21-23) is found at several levels in the 

Miocene section. The pollen of a Central American 

species of Guettarda, G. macrosperma Donnel Smith, 

is rather similar to that of Timonim ; the similarity suggests that these two genera perhaps cannot be distinguished morphologically. Actually, the pollen of the 

only Micronesian Guettarda species (G. speciosa L.) is 

competely different from that of the Thnonius species 

considered here. Tinioniiw-type, fossil material is compared with modern Thnonius and Guettarda. pollen on 

plate 310. Timon'tuz is a common genus in the Carolines 

and Marianas but is an upland form. An atoll species, 

T. polygamu* Robinson, occurs in Polynesia (F.R. Fosberg, written commun., 1964).

A single specimen of Gardenia, pollen was found in 

the Eniwetok Miocene flora (pi. 310, figs. 16, IT). Its 

discovery was unexpected because the genus is known 

as an upland or montane form; it occurs in Malaysia, 

Borneo, Fiji, the Ryukyus, Polynesia, and Hawaii, but 

I could find no record for the genus in Micronesia. The 

pollen morphology of Ga.rdenia is unusual in Rubiaceae, 

because it is one of the few genera of this family in 

which the pollen tetrads do not break apart upon 

anthesis. The other Gardenieae of which this is also 

characteristic are of Asiatic or Caribbean distribution. 

The present record cannot be explained by laboratory 

or field contamination. One might suppose that this 

specimen could have reached Eniwetok lagoon during 

the Miocene by means of long-distance transport by 

wind, except that it is a relatively heavy large grain. 

Gardenia may have grown on islands nearer Eniwetok 

than it does today.

Of the 21 pollen types of undetermined family affinity 

listed on page 1146,12 are described under "Systematic 

Descriptions" (p. 1165).

MODERN DISTRIBUTION OF MIOCENE GENERA

Generically, the Miocene Eniwetok flora can be classified into broad geographic elements according to their 

total ranges; geographic groups are according to Glassman (1957). On this basis, the fossil flora can be classified as follows:

Group 1. Micronesian or Pacific island genera: None 

found.

Group 2. Indo-Pacific genera (occurring in Indonesia 

or southeast Asia and on islands of the Pacific and 

Indian Oceans) and paleotropical genera: 29 percent.

Lumnitzera

Sonneratia

Bruguiera

Pandanus

Ceriops 

Group 3. Pantropical genera: 71 percent.

Ixora

Toimiefortia

Morinda

Gardenia

Randia

Temmnalia

Rhizophora,

Thespesia

Cordia

Acalyplia

Pisonia

Avicennia 

Group 4. Cosmopolitan genera: None found.

The prevalence (71 percent) of pantropical genera in 

the Miocene flora is also characteristic of the modern 

genera of Eniwetok flora (48 percent pantropical 

genera). Indo-Pacific and paleotropical genera, which 

comprise 29 percent of the Miocene flora, represent 31 

percent of the modem flora. Cosmopolitan genera which 

as a group were lacking in the fossil flora comprise 21 

percent of the modern Eniwetok flora.

Only four of the identified fossil genera are native 

to Eniwetok today; these are Pandanus. Pisonia, Cordia. 

and Toitmefortia. The relation between the generic 

composition of the Micronesian fossil and modern floras 

is discussed in the context of other late Tertiary floras 

on pages 1163-1165.

DISTRIBUTION OF SIMILAR LIVING SPECIES

Even though the preponderance of fossil genera has 

pantropical distribution, the modern affinities of the 

fossil flora may be Indo-Pacific. Almost all species 

affinities suggested in the systematic descriptions are 

Indo-Pacific in distribution; however, this specific 

relationship, probable as it may be, cannot be categorically established for all the fossils belonging to pantropical genera for two reasons: (1) the geographic 

scope of the modern reference material was, for several species, not wide enough to establish an Indo-Pacific 

affinity versus some other, or (2) the pollen morphological differences between the species of a genus were not 

great enough (as they are, for example, in Pandanus} 

to permit subgeneric determinations.

An evaluation of fossil affinities by geographic divi-
MIOCENE POLLEN AND SPORE FLORA OF ENIWETOK ATOLL, MARSHALL ISLANDS 1151

sions, including fossils identified on a subgeneric level 

where that was possible, is as follows (an asterisk marks 

genera which have all their species in the same geographic province) :

Group 1. Micronesian or Pacific island species: None

identified. 

Group 2. Indo-Pacific elements: 56 percent.

Pisonia cf. P. grandis

Sonnemtia cf. S. alba

Rhizophora cf. R. apioulata

Rhizophora cf. R. mucronata

*Bruguiera sp.

*Ceriops sp.

Lumnitzera cf. Z. littorea

Tournefortia cf. T. argentea

Morinda cf. M. eitrifolia

Thespesia, cf. T. lampas 

Group 3. Pantropical elements: 44 percent.

Pandanus sp.

Acalypha. sp.

Terminaliasp.

Cordia

Avicennia

Ixom

Gardenia

Randia 

Group 4. Cosmopolitan elements: None identified.

Whereas the affinity of the fossil flora is primarily 

paleotropical (Indo-Pacific), the affinity of the modern 

flora at Eniwetok (here classified) is about evenly split 

among Micronesian, paleotropical, and pantropical 

species (those for which comparative fossils have been 

found are marked with an asterisk) :

Group 1. Micronesian and Pacific island species: 31 

percent.

Lepturus repens

Fimbristylis atollensis

Achryanthes velutina

Portulaca lutea

P. samoensis

Boerhama tetrandra

Euphorbia chamisso-niz

Terminalia sainoensis

Ochrosia oppositifolia

Sida fallax

Group 2. Paleotropical or Indo-Pacific species: 38 

percent.

Polypodiuin scolopendria

*Pandanus tectorius 

Pemphw acidula

* Cordia subcordata

*T oiimefortia, argentea

Fleurya ruderalis

* Pisonia grandis

Canavalia microcarpa

Triumfetta procumbent

Wedelia biflora

Thuarea involuta

Scaevola taccada 

Group 3. Pantropical' species: 28 percent.

Xianenia americana

Boerhavia repens

Oassytlia filiforwiis

Vigna marina

Tribulus cistoides

Suriana maritima

Iponwea pes-caprae

Cruettarda speciosa

Ipomoea tuba 

Group 4. Cosmopolitan species: 3 percent.

Digit aria pruriem

In comparison with the affinities of the living indigenous plant species of Eniwetok, the plants with 

which the fossils have affinities are of the following 

distribution types (figures are percentages of the identified floras) :

Modern

Present distribution Fossil taxa species

Pacific island or Micronesian--_____ None certain 31

Paleotropical (Indo-Pacific)________ 56 38

Pantropical________--_-_-----_-__ 44 28

Cosmopolitan ____________________ None certain 3

These figures indicate that the Miocene taxa which 

now either grow mainly west and south of Eniwetok 

or are paleotropical were partly replaced by taxa which 

are Pacific island forms today. The composition of the 

vegetation of Eniwetok clearly was altered significantly 

during the late Cenozoic, and because consideration of 

these floral changes will perhaps aid in understanding 

environmental changes on the island during that time, 

these floral changes are considered in detail here.

Table 2 and the foregoing lists show that more than 

half the identified Miocene flora now occur in the IndoMalayan area; some species range as far west as Africa 

(paleotropical distribution) and some eastward into 

Micronesia, The ranges of two plants to which the fossils are related have retreated westward at least 20° 

longitude since the Miocene; these are Ceriops, which is 

not now found east of the western Carolines, and Thespesia lampas, not now found east of New Guinea in 

the South Pacific (table 2). Gardenia has several endemic species in Hawaii, longitude 40° E. of Eniwetok, 

and also grows in Fiji, Tahiti, and New Guinea. Its 

fossil occurrence at Eniwetok suggests that in the midPacific its range has retreated southward about 1,300 

miles since Miocene time.
1152 BIKINI AND NEARBY ATOLLS, MARSHALL ISLANDS

Four other taxa to which the fossils are related— 

Acalypha, Rhizophora apiculata, Ixora case'i, and Avicennia marina—now occur in Micronesia as far east as 

the Mariana Islands and the eastern Carolines, 400 

miles southwest and 1,000 miles west, of Eniwetok, respectively. (Acalypha also occurs on Fiji.) Five others 

range from Indo-Malaya eastward into the southern 

Marshalls; these are Terminalia catappa* Lunvnitzera 

littorea, Rhizophora rrwcronata, Randia cochinchinensi-s, and Sonnemtia alba. Two taxa, Bruguiera gymnorhiza and Morinda, citrifolia, now range from IndoMalaya eastward to the southern Marshalls, but they 

are not indigenous to Eniwetok today. Four others have 

the same general range but, in addition, are native to 

Eniwetok today: Pandanus sp., PLwnia grandis, Tournefortia argentea^ and Cordia subcordata.

TABLE 2.—Distribution of living taxa (native occurrences only) 

with which Eniwetok fossils show affinity

[Localities listed from west to east; question mark indicates either questionable 

occurrence or occurrence but questionably native]

Taxa (17 genera, 18 species)

Total... -.-__._.____.-_...

Asia eatern Continental 

X

X 

X

X 

X

X 

X 

X

X

9

Borneo Indo-Malaya and yy<yy.yy* 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X

17

Philippine New Gulnea« * ' uv

yy*WKyK Islands

X 

X 

X 

X 

? 

X 

X 

X 

X 

X 

X

16

Micronesia

Islands Western aroline y.y.y.y*.y<. C 

T

X 

X 

X 

X 

X 

X 

X 

X 

X

X

16

13

1

I-H

1 

1

xf

X

X

X 

X 

X 

X 

X 

X 

X

?

X

11

•3

M

1o

1 

1

H 

X

X

X

X 

X 

X 

X 

X 

X 

X 

X 

X 

X

X

14

Islands Marshall Southern 

X

X

?

X 

X 

X 

X 

X

X 

X

1

X

10

1

I-Hi

0

1

X

X

? 

X 

X

X

5

1

•<

•8

| 

a W

X

X 

X

X

4

£

X

X

X 

X

X 

X

7

X

X

"T

•S

h3

_<3 '3

1

B

— -

X 

X

X 

X

4

Table 2 shows that 16 out of 18, or 89 percent, of the 

present relatives of the Miocene flora now grow in 

the western Carolines, and that most of these taxa also 

occur in Indo-Malaya. Moreover, the enormous diversity of the Indo-Malayan and New Guinea-Borneo modern floras is not at all suggested by the relatively sparse 

Miocene flora of Eniwetok. Therefore, it is reasonable 

to conclude that the primary affinity of the fossil flora 

is with the present flora of the western Carolines 

rather than with flora on larger land areas farther 

west.

ABUNDANCE OF FOSSIL POLLEN AND SPORES IN 

ENIWETOK SEDIMENTS

In this report the abundance of plant fossils is expressed in two ways: absolute number of fossils per 

gram of dry sediment, and relative number, expressed 

as a percentage, of the total pollen and spores tallied. 

When the area of the aliquot slide used for a tally has 

been noted, the tally can be used to calculate the approximate number of specimens per gram of sediment 

(p. 1144). Calculations for the Eniwetok sediments are 

summarized in table 1, and are shown on a semilogarithmic graph in figures 340 and 341. Table 4 indicates relative abundance of the identified fossil pollen and spores 

in tallies, and figure 342 shows this abundance graphed 

as a pollen histogram.

Hole E-l.—Small amounts of pollen and large 

amounts of Chroococcalean algae per gram of sediment 

occur at depths 2,000-2,500 feet (table 1 and fig. 340). 

Pollen density is very great (about 21,000 grains per 

gram) in the highest interval sampled, at 850-860 feet; 

algae are present in this pollen-rich sample but are not 

abundant.

Hole F-l.—No algae were found except in the sample 

from the lowest interval; this sample is of Eocene age, 

and was taken 100 feet above the basement basalt (table 

1 and fig. 341). A total of 24 (about 2 per gram) waxy 

pollen grains was found in this sample, but none could 

be identified with living genera. Peak concentrations 

of pollen and spores occur at two levels in drill hole F-l; 

the astonishing calculated density of 102,000 pollen 

grains per gram of sediment was determined for the 

sample taken at depths 830-840 feet, and 35,000 pollen 

grains per gram for the sample at 670-680 feet.

SOME ASPECTS OF MODERN POLLEN RAIN IN EASTERN 

MICRONESIA

To compare the abundance of pollen and Chroococcalean algae in fossil sediments with that in modern sediments, 32 modern lagoonal and marine sediments from 

eastern Micronesia were analyzed. Table 3, which shows 

the results for the modern samples, indicates that only 

five of the 32 samples contained pollen, and that only 

three contained remains of Chroococcalean algae. I was 

unable to find any pollen in the atoll lagoonal sediments 

of Eniwetok, Bikini, or Jaluit in the Marshalls, or in 

Onotoa lagoon, Gilbert Islands. However, in the Caroline Islands rare pollen was found in lagoonal muds 

of Kapingamarangi and in a taro-swamp mud on Ifalik. 

It will be noted that the only significant amounts of 

pollen (more than 500 grains per gram of sediment) 

were found in three lagoonal samples from Ponape.
MIOCENE POLLEN AND SPORE FLORA OF ENIWETOK ATOLL, MARSHALL ISLANDS 1153

850-860

860-870 

880-890

2003-2028

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£j 2480-2490

Q

2500-2510

4078-4100

1(

_

_

, , , i 1 - ——————————

X) 1000 10,000 20,000

CALCULATED NUMBER (LOG SCALE)

FIGURE 340.—Calculated number of pollen and spores (solid lines) and colonial algae (dashed lines) per gram of sediment in drill hole 

E-l. +, Pollen or spores present but less than 100 per gram. *, Colonial algae present but less than 100 per gram.

170-191

600-625

670-680

< 810-820 

>

£• 820-830

Z 830-840 

I 840-850

£ 850-860

Q

1000-4500 (12 samples yielded no pollen, spores, or colonial algae)

4528-4553 \— + *

1000 10,000 

CALCULATED NUMBER (LOG SCALE)

100,000

FIGURE 341.—Calculated number of pollen and spores and colonial algae per gram of sediment in drill hole F-l. +, Pollen or spores 

present but less than 1,000 per gram. *, Colonial algae present but less than 1,000 per gram.

If the modern pollen data listed in table 3 are arranged by localities according to size of land area, an 

interesting relation is suggested. On the atolls and 

islands having a land area of less than 4 square miles 

and a maximum elevation of less than 20 feet (Eniwetok, Bikini, Jaluit, Onotoa, Kapingamarangi, and 

Ifalik) no pollen is present in 23 lagoonal or swamp 

sediments and rare pollen is present in five samples. In contrast, lagoonal sediments from the large 

high island of Ponape (90 sq mi of land area, and 

2,595 ft maximum elevation) contain abundant pollen— 

about 34,000 pollen and spores per gram of sediment 

(four samples).

Even though in the present study the sampling of 

modern sediments is limited (32 samples from seven 

islands or atolls), a strong indication of an all-or-nothing situation is apparent; the contrast between the 

scarcity or lack of pollen in random samples from atolls 

or small islands and the abundance of pollen in samples 

from a large high island is extreme. The data strongly 

indicate that the size and, probably, height of the 

vegetated land area are important limiting factors for 

maximum pollen density in the lagoonal sediments of 

eastern Micronesia. Though there is no direct evidence, 

as from modern pollen traps, in that part of the world 

to establish the volume of annual pollen rain at different

336-388 O—«9-
1154 BIKINI AND NEARBY ATOLLS, MARSHALL ISLANDS

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40 60 80 0 10 010 0 20 40 60 80 0 10 0 10 0 0 10 0 0 0 10 0 0 20 0 10 

TOTAL POLLEN AND SPORES: SOLID BARS IN PERCENT; OPEN BARS IN ACTUAL NUMBERS

FIGURE 342.—Pollen diagram showing percentages (solid bars) of total pollen and spores in Eniwetok drill holes E-l and F-l; in lower part 

of section where less than 100 grains were found per sample, results are shown ns actual numbers of grains (open bars). +, Percentages 

of less than 1 or occurrences not included in tally. Samples from drill hole F-l are assigned Use's paleobotany loc. D1215, and those 

from drill hole E-l, USGS paleobotany loc. D1200. *. barren zone.

sites, evidence from the modern lagoonal sediments indicates that pollen rain is relatively sparse on atolls and 

prolific on high larger islands.

Factors other than the abundance of plants should be 

considered in discussing abundance of pollen in atoll 

sediments; distance from source plants, nature of water 

currents, depth of water at the deposition site, and texture of the sediments are a few. In a modern pollen 

study at Kapingamarangi, I found that occasional pollen is present in shoreline and shallow-water sediments 

and in very deep water sediments (E. B. Leopold, in

McKee and others, 1959) and that pollen is more abundant in finer grained sediments, as at Ponape (table 4). 

Another important factor affecting pollen density is 

probably the location of land along the reef rim of atolls 

in relation to dominant wind direction. At Eniwetok, 

Bikini, and Kapingamarangi, the bulk of land above 

mean sea level is on the windward side of the atoll, so 

that local pollen has a reasonable possibility of falling 

into the lagoon. If the vegetation were mainly on the 

lee side of the atoll, however, pollen might be even more 

infrequent in lagoonal sediments.
MIOCENE POLLEN AND SPORE FLORA OF ENIWETOK ATOLL, MARSHALL ISLANDS 1155

TABLE 3.—Calculated number of pollen and spores and Chroococcalean algal colonies in modern sediments from eastern Micronesia

[All sediments are lagoonal except sample D1655, which was taken from seaward slope]

Locality

Marshall Islands: 

Eniwetok

Bikini- __

Jaluit- _ _ _ _ _

Gilbert Islands: 

Onotoa _

Caroline Islands:

Ifalik____. ______

land (ft) 

area 

(sq mi)

= 2.5 =12

= 2.4 =12

= .4 =12

= 1 =12

= 1 =12

=.6 =18

90 2, 595

Type of collection 

area

do

____.do._._---_-

_____do-___._--

Pacific Ocean,

northwest of 

Bikini. 

Lagoon____

___._do_--------

do

-_-__do___-.___.

^-_--do_-_-_____

do

Harbor area. 

__-_.do- — _____

_ — _do— ---__-

_—— do— — — _

Sample

Number

Emory 165 __ _

Fosberg 1 _ _ _ _

Fosberg 2 _ _ _ _ . D1654_______.__

Dl655_-_---____

McKee 494-496,

498. 

Dl657___-______

D1658___ — -____.

51-S-7,

D1659-D1661. 

D1662_ ____---__

D1141-1

through -11. 

IF-9

D3248_----_____

D3249---------.

D3250_._-__-_-_

D3251_ _-__._._

Dry weight 

(grams)

9

10

10

20

20

14-20

20

20

20

20

2

8. 5

5

Depth below 

mean sea 

level (ft)

9

10

10 8-10

3,400

6-14

0

0-19

0

0-240

0

4

4

4

4

Pollen and spores

Per Per

tally gram

_-.___ 0-200

140 214

225 34, 640

550 1, 180

430 1,475

325 392

Algal colonies

Per Per 

tally gram

151 4, 200

43 1, 600

15 320

TABLE 4. — Percentage composition and absolute numbers of 

pollen and spores per gram in modern sediments from Metalanim 

Harbor area, Ponape, Caroline Islands

[Water depth, —4 ft mean sea level; asterisk (*), forms found as Miocene fossils on 

Eniwetok. Actual numbers shown in parentheses]

Type of sediment _ _._______-..___.

Distance from mangrove stands (ft) . 

USGS paleobotany loc. ------------

Rhizophoraceae :

Sonneratiaceae:

Combretaceae: 

cf. Lumnitzera* . . . .............

Proteaceae? _....._....--.._.---_.--

Malvaceae: 

Sidafallax. .....................

cf. Rosaceae... ---------------------

cf. Polypodiaceae:

Verrucate trilete.-. .___.__-.____

Taccaceae:

Pandanaceae:

Rubiaceae:

Other.. __-._-_.._.-------__-_.-

Leguminoseae:

Ulmaceae: 

Trema.... ......................

Total.. .......................

Black Brown Brown 

organic organic organic Gray 

silt sand and carbonate carbonate 

silt sand sand 

and silt 

20 100 300 360 

D3248 D3249 D3250 D3251

46.5 41.4 46.0 24.4 

----------- 7.8 ....__......-.....-.....

16.0 20.2 23.8 14.1 

8 ..................................

8 ..................................

16 .6 .................

8 .------._-._..__......_.___.__._....

8 ................ ... ... . .

5.6 6.1 11.3 20.8 

4.8 5.6 11.0 23.0 

................_......__-__.------ 3.0

4 44

.8 1.7 .4 .7 

.8 2. 2 1.1 2. 2 

.6

------------ .6 .4 ..__-_-. . _

4 11

....................... .4 ._____-.....

.---..-.„......-... — ..-_.__...-. .7

10.4 11.7 4.1 3.0 

.8 ............ .8 1.5

100.1 09.1 100.1 100.1

TABLE 4. — Percentage composition and absolute numbers of 

pollen and spores per gram in modern sediments from Metalanim 

Harbor area, Ponape, Caroline Islands — Continued

Black Brown Brown 

organic organic organic Gray 

T ype of sediment. .._____..-_._..-._ silt sand and carbonate carbonate

silt sand sand 

and silt 

Distance from mangrove stands (ft) . 20 100 300 360 USGS paleobotany loc. ------..--.- D3248 D3249 D3250 D3251

Total pollen and spores tallied for 

percentages....-.-.-....-......-- (125) (179) (265) (135)

Calculated pollen and spores per

gram of sediment. ................ (34,640) (1,180) (1,475) (392) 

Based on counts of.....-......-.--- (100) (472) (163) (190)

NOTE.— 2 Foraminifera per 125 pollen and spores were found in D3248, and 2 per 

135 pollen and spores in D3251; one dinoflagellate cyst was seen in D3240.

Distance from source vegetation was shown by Muller 

(1957) to be an important factor in determining major 

differences in pollen abundance. He established that, in 

the Gulf of Paria, Venezuela, a great abundance of 

pollen (more than 2,000 to 10,000 pollen and spores per 

gram of sediment) is found within a few miles of land, 

whereas at greater distances from the coast, progressively less pollen is found and that amount seems to have 

been controlled by water currents. He found the greatest 

abundance of pollen ( 100,000 pollen and spores per gram 

of sediment) in a continental (back swamp) environment where source plants were only a short distance 

away and where deposition rates were probably slow. 

Productivity of source plants also should be considered as a controlling factor. Mangroves of the Rhizophoraceae characteristically are higher pollen producers
1156 BIKINI AND NEARBY ATOLLS, MARSHALL ISLANDS

than are other types of strand vegetation, such as Pandanus and Pisonia. Modern sediment samples (D3248- 

D3250) from Ponape collected from 18 to 300 feet from 

mangrove stands contain about 50 percent mangrove 

pollen and the sediments are rich in pollen; but one 

sample (D3251) taken 360 feet away contains only 

about 25 percent mangrove pollen (table 4), and total 

pollen frequency is much lower. Muller (1957) found, 

however, that the mangrove pollen represents as much 

as TO percent of the pollen assemblage at sampling points 

about 50 miles from land, though at that distance the 

pollen grains were fewer than 500 per gram of sediment. 

In the Gulf of Paria the combination of dominance of 

mangrove pollen in the assemblage and high pollen density in the sediments is found only between 1 and 5 miles 

from the shoreline.

Both Muller's and my own modern pollen data suggest that mangrove pollen can mask the abundance of 

pollen from inland vegetation types. At Ponape (table 

4) and in the Gulf of Paria, pollen of the rich vegetation of inland environments and nonmangrove strand 

vegetation is poorly represented in nearshore marine 

environments.

The mere presence of mangroves on an atoll does not 

guarantee that mangrove pollen will be readily found 

in lagoonal sediments. A small patch of mangroves now 

grows on the atoll of Onotoa, Gilbert Islands; yet mangrove pollen was not found in any of the seven samples 

of Onotoa lagoonal sediments. Mangroves now grow on 

Jaluit, but mangrove pollen was not found in the four 

samples from that lagoon (table 3).

In summary, the abundance of fossil pollen and 

spores in the Miocene sediments under Eniwetok, ranging from 100 to 100,000 per gram of sediment, is in 

complete contrast to their apparent scarcity in modern 

lagoonal sediments of eastern Micronesia. The abundance of fossil pollen in certain of the Miocene sediments of Eniwetok is comparable with the abundance of 

modern pollen in shallow-water lagoonal sediments 

from Ponape in the Caroline Islands; the predominance 

of mangrove pollen in both is a second feature in common. Data secured by the comparative study of modern 

and fossil pollen for this report indicate that the pollenrich Miocene sediments were deposited in an environment not far from dense stands of vegetation; the 

vegetated land area on Eniwetok was probably larger in 

Miocene time than at present.

FLORAL SEQUENCE IN'DRILL HOLES

Tallies of pollen and spores in samples from drill 

holes F-l and E-l are shown in table 5. These results 

are presented in graph form in figure 342, which is

drawn as a composite section incorporating data from 

both holes. A sampling overlap occurs in the two holes 

at 850-860 feet.

The deepest interval, recognized stratigraphically in 

this study as zone 1, is in drill hole F-l at 4,528-4,553 

feet, sample 15-12. In 13 grams of Eocene sediment, 24 

angiosperm pollen grains, or about two per gram, were 

found. In addition, Chroococcalean algal colonies numbering about 25 per gram of sediment were seen. These 

were the only fossils found within the Eocene part of 

the section, although about nine sampling levels of 

Eocene core runs were examined. The contained pollen 

is not identifiable in terms of living genera (table 5, 

sample 15-12) ; but because some grains can be assigned 

to Rubiaceae, one can be sure that pollen of land plants 

is present. This occurrence of land-plant remains is of 

great interest because of its stratigraphic position about 

77-102 feet above the basement basalt. The lithology 

of this zone is firm dolomitic and calcitic limestone. 

These sediments are at the base of Cole's (1957) Tertiary zone 5 (Eocene).

The second zone, at 2,662-4,525 feet in drill hole F-l, 

may be defined as a barren interval in terms of pollen, 

spores, or Chroococcalean algae. Samples from nine core 

intervals (table 1) were found to be devoid of these fossils. The interval includes mainly the sediments of Eocene (Tertiary b) age but also the lowest part of the 

Miocene sediments. The lithology of this zone is lithified 

calcite and dolomite of clay and silt sizes.

The third zone, from 2,440 to 2,510 feet in drill hole 

E-l, may be termed the "Chroococcalean algal zone" because it is characterized by high frequencies of Chroococcalean algae, numbering from about 200 to 10,000 

colonies per gram of sediment. Pollen is present in small 

to moderate amounts (up to 1,000 grains per gram of 

sediment) in every sampling level. The pollen is mainly 

that of Pisonia. Rubiaceae, and an undetermined monocot, but Callitriclie type and cf. Coprosma are also 

present. The zone represents lower Miocene sediments at 

the base of Cole's Tertiary e (Ladd, 1958), Lithology 

is soft unaltered aragonitic mud.

The fourth zone is barren, and no organic remains 

were found. It is represented by only four samples: 

from drill hole E-l, a core from 2,003-2,028 feet, and 

from drill hole F-l, three cores from the interval 1,232- 

2,003 feet. The lithology of the core in both holes E-l 

and F-l is recrystallized calcitic limestone; age is early 

Miocene (Tertiary zone e of Cole, 1957; Ladd, 1958).

The fifth zone is a richly polleniferous interval represented in both drill holes E-l and F-l; Rhizopliord pollen is the dominant form. Because another zone, the 

seventh, is also dominated by Rhizophora pollen, I refer 

to the fifth as the lower Rliizophora zone.
TABLE 5.—Percent total pollen and spores tallied in sediments from drill holes F-l and E-l, Eniwetok 

[Numbers in parentheses are actual number of grains observed; + indicates occurrence but not encountered in tally]

Drillhole. — .. — - — ———— „ — . — — — .. — „„ — —— -.

USGS paleobotany loc...-- -------- . — — -.._ _ . __.—— — .

Sample No. _...-- _______ ................ —__....._— _-_...__.

Depth (ft).. —— . — —— —— — —— —— —— — —— ———— — ...

Palynological zones '-----_ ---------....-------. _ .--------..--...

Spores of Pteridophyta:

?Polypodiaceae:

M-sm(l) -....._. . ------._-. .- -_____ — _--_ — ._

Tl-sm(2)

?Pteridaceae:

?Hymenophyllaeeae:

Trichomanes type, Tl-p(2) __ __ . — — ... __ — ..... — ..

Pollen of Monocotyledonae:

Pandanaceae:

Pandanus

Monocotyledonous pollen of uncertain family affinity:

?Palmae:

Livistona type, C1-sm(l).. — . .......................

Cj— sm(2)

Ci and Inaperturateundet.. — ----. — -- — — -.--- .-----....-..

Pollen of Dicotyledonae:

Nyctaginaceae:

Pisonia cf. P. grandis ... ... ...................... .......

Euphorbiaceae:

Acalypha. .................................................

Malvaceae:

Thespesiaci. T.lampas...... .... .... ... ........... ___ ..

Sonneratiaceae:

Sonneratia cf. S. alba........... — — — — — — — — — — —

Bhizophoraceae:

Rhizophora cf. R. apiculata. ...................... _. .....

Rhizophora cf. R.mucronata ____ —— . __ ______ ..

Rhizophora sp _ . ___ _ . ___ . —— ___ „ —— .. — ..

cf. Rhizophora... ... .. ... ................. .... — - — .— ...

Bruguiera cf. B. gymnorhiza.. .... .... ... ............... ...

Ceriops cf. C. tagal..... ___ .. ___ . _ ... _ . _ __

Combretaceae: ^ Terminalia cf. T. catappa .... ........... ... ............ ... ..

cf. Combretum ... .... ... ................................ ... . Lumnitzera cf. L. littorea........ ....................... ...

Myrtaceae:

cf. Eugenia.................................................

Boraginaceae:

Tournefortia cf. T. argentea. .................. ..............

Cordia cf. C.subcordata... ... ........ ..... ... .... ... ........

Verbenaceae:

Avicennia cf. A. marina ... ... ............ .................

Bubiaceae:

Ixora cf. /. casei. _____ .... ______ ... ___ .„. — ..

Gardenia cf. O. grievei.. ............... . _____ .. _ . — . Morinda cf. M. citnfatia.. ................................... 

cf. Guettarda. ... ...... ..... . ........................... ...

cf. Timonius. ......................... ....... ..... ..... ... . Randia cf. R. cochinchinensis . _______ ... __ .... _ ...

cf. Scyphiphora ....................... — __ . __ .. _ ....

cf.Mussaendafrondosa....... .... . ..... .... .... .... .......

.............. F-l E-l

.__ ———— —— D1215 D1200

.- ———— ... . 15-12 10B 9 8 7A 6 5 4 3 2 1 F

4,528- 2,500- 2,490- 2,480- 2,470- 2,460- 2,450- 2,440- 880- 870- 850- 850-

......———— 4,553 2,510 2,500 2,490 2,480 2,470 2,460 2,450 890 880 860 860

.. _ ......... Zone 1 ZoneS Zone 5

— ——— —— ——— ————— — (3) — ............. (1). ...... —— - ————— — ....——— 2.2 0.

(1) ....

--... .. ..... —— ..... ...... . —— ———— —— ——— ..... .. — — — ——— . 0.9 .4 _-.- —

.... ......... — — ... (2).. — ——— — ——— ———— ——— (7) (2)-——— 1.8 ——— — _ ———

....... . ——— ——....... — — . ——— ... — —— (1) (1)—— .... (2) ————— ———— .———— .2

..... — __ — . (6) —— ———— — — --- — --— (4)————— (6) — ....... .. ————— .... .2

— — —— ___ — _ —————— ——— __ —————— -———— (12)--- — -—- — - — — — — — — — - — - —

.4

... — — __———— — — —— — ——————————— (1) (1)————. — — . 30.2 21.2 51.8

...... - —— ..... ——— - —— ——————... (I). — . ————— —— —— 31.2 32.0 5.3

...— - ——. ——— —— ——— ——————————— (3) (I) — — ..————. 6.4 4.8 30.6

____ . .9 .9

..... ... .............................. ........... .-. — ....-...-.. ——— ———— .. .4 6.5

————— ...... . — ....... ............. ...... .... ——— .. — ... (3) — — — — .— .9 7.1 .2

..-. .4

............. ........ ........-. — ... (I) — .. — —— — —— — .-. —— . — ..—— 1.8 14.6 .......

. ... .9

—— ——— — —— ———— —————— ——— . ——— ——— ——— — —— —— - (1)...——— 5.5 ........ .2

— ————————————— — — —— .—.——.—— (1) (3) — ————— — .9 1.3 .......

.... . (2). ....

............. ——————— .. ———— .. ——————— — —— (8) (6).———— (1) ——— — ———— ———— 

.. — .— ——— ................... _______...——— (1) (1) (2)..————— ....... ..... ————— 

—— ——— ——— (1). ——— ——— ————— .. — ——— ——— — — (1)——— ————— ————— +... ....

See footnote at end of table.
1158 BIKINI AND NEARBY ATOLLS, MARSHALL ISLANDS a

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MIOCENE POLLEN AND SPORE FLORA OP ENIWETOK ATOLL, MARSHALL ISLANDS 1159

In drill hole E-l, the fifth zone is at 850-880 feet, and 

abundant pollen occurs at two intervals (850-860 and 

870-880 ft). (Pollen is present between depths of 880 

and 890 ft, but only three grains were found.) Pollen 

grains in the two rich intervals are about 500 and 21,000 

per gram, respectively, and algal colonies are as numerous as 85,000 per gram of sediment. In the lower 

level sampled, Rhizopfiora pollen is associated with 

small amounts of Avicennia, Lumnitzera, Terminalia 

and Rubiaceae pollen; undetermined pollen constitutes 

20 percent of the sample. In the upper level, Rhizophora 

is associated with Lumnitzera, Terminalia, Sonneratia, 

and Avicennia.

In drill hole F-l, the fifth zone is at 840-860 feet, 

and samples were taken from two levels. Pollen abundance at the two levels is about 3,000 and 13,000 grains 

per gram of sediment, and algae are absent. Dominant 

Rhizophora is accompanied by 5 percent Oeriops. 

Randia, Morinda, Avicennia, Tournefortia, Gordia, 

Bruguiera, cf. Gynotroches, Sonneratia, and cf. SopJiora are 'also present. The lithology of the zone is unaltered soft aragonitic mud, which includes Miocene sediments of Cole's (1957) Tertiary / and g (late Miocene, 

Ladd,1958).

The sixth zone, at 820-840 feet in drill hole F-l, is 

dominated at the two sampling levels by Elaeocavpm 

type pollen, accompanied by fern spores (about 7 percent of pollen count). In the lower level sampled, cf. 

Elaeocarpus is especially frequent (about 83 percent 

of pollen count). Here is the only zone in which Sonneratia pollen represents more than 1 percent of the 

count. In the upper level, Oeriops, cf. Gynotroches, and 

Temn-inalia are present in small percentages. Cf. Salacia, cf. Eugenia,. Gardenia, and Ixora occur only in 

this zone. Cf. Guettarda, Morinda, Avicennia, Tournefortia, and Lumnitzera are also present. The lithology 

is soft aragonitic mud containing small flakes of carbonaceous material. These sediments belong to the lower 

part of Cole's (1957) Tertiary g or youngest Miocene

zone.

In the seventh zone, a polleniferous zone, Rhizophora 

dominates again; the zone is therefore termed the "upper Rhizophora zone." Samples were taken at two levels 

in drill hole F-l at 810-820 feet and 670-680 feet. A 

small amount of Ceriops pollen is present; Thespesia, 

Oallitriche type, Bruguiera, Gynotroches type, Cordia, 

Terminalia, Morinda, Randia, and Pandanus are all 

present. The sediments are soft aragonitic mud and 

represent the upper part of the Tertiary g of Code 

(1957) or the youngest Miocene.

In zone eight (drill hole F-l, at 170-190 ft. and 600- 

625 ft.) two samples of cores were barren. The lithology

of the sediments is calcitic reef limestone, which is postMiocene in age.

A summary of the data concerning the eight zones 

and the number of fossils per gram of sediment, 

follows:

Maximum density

of palynomorphs

per gram of

sediment

Age (Cole, 1957) 

Post-Miocene... _ - _ 

Late Miocene, Tertiary g. -

Late Miocene, Tertiary g.. 

Late Miocene, Tertiary/, g

Early Miocene, Tertiary e. 

Early Miocene, Tertiary e.

Eocene to Miocene, Tertiary e, b. 

Eocene, Tertiary ft...--_

Zone 

8

7

6

5

Depth 

170-625 

670-820

820-840 

840-880

Colonial 

Pollen algae

~~46~666"-~~~~-~-! 

100,000 ..........

10,000 10,000

4 1,232-2,028 .... — .........-..

3 2,440-2,510 1,000 10,000

2 2,662-4,525 ....................

1 4,528-4,553 2 25

Zone 

description

Barren.

Upper Rhizophora zone.

Sonneratia 

zone.

Lower Rhizophora zone.

Barren.

Chroococcalean algal 

zone.

Barren.

Eocene pollen 

zone.

ECOLOGICAL RELATIONS

The present habitats of the species and genera with 

which the fossil forms have affinity are given under 

"Systematic Descriptions" (p. 1165) and are summarized in table 6. Also listed in the table are the habits 

of these plants: seven are mangrove swamp; four are 

strand and coastal forest or thicket; three are coastal 

f oresit or thicket; two are coastal forest to upland forest; 

two are upland forest only. Evidence from identification of pollen indicates that certainly two if not three of 

the habitats existed on Eniwetok during Miocene time. 

A discussion of the inferred plant associations follows.

MANGROVE SWAMP FORMS

None of the seven mangrove swamp forms to which 

the Miocene pollen are related now grow on Eniwetok 

Atoll. Estimation of the probable community structure 

requires comparisons with mangrove swamps elsewhere 

in Micronesia.

Though most of the mlangrove forms identified here 

can be found in association in mangrove swamps in the 

Palau Islands and in Malaya, a few of the forms are 

known in the southern Marshalls in a unique mangrove 

habitat, described by Fosberg (1947,1949) as mangrove 

depressions. In the middle of atoll islets in the southern 

Marshalls, he observed depressions in which Bruguiera, 

Sonneratia, Lumnitzera, and even Rhizophora mucronata grow. On the atoll ridges, salinity of the ground 

water is much lower than that of soils closer to the shoreline (Fosberg, 1956). The water in mangrove depressions, especially where Bruguiera grows, is of surprisingly low salinity; Hatheway (1953) found chlorine 

concentrations of only 15 ppm (parts per million), or 

only about 0.1 percent of that in local sea water, in a 

Bruguiera swamp on Amo Atoll, and in water from a
1160 BIKINI AND NEARBY ATOLLS, MARSHALL ISLANDS

TABLE 6.—Habits and habitats of living taxa with which Miocene fossils of Eniwetok show affinity

Number of species

Taxa Habit Habitat of the genus now

growing in 

Micronesia *

Acalypha sp________---__-___-- Shrub__-___ Coastal forest to upland forest, but not strandAvicennia marina- _____________ Tree_-_____ Mangrove swamp_______---___--_--__-_-__-

Bruguiera gymnorMza-.-.------- do_-__--- Mangrove swamp and mangrove depression__

Ceriops ta0aL__-_____--_--___--_-do_--___- Mangrove swamp______----_--_-____--_____

Cordia subcordata- ___-_______--___do_______ Coastal forest and strand__________________

Gardenia sp____--_____-_---__- Shrub______ Upland forest, not strand._____--____-______-

Ixora case«-,______-__-____--__--_-do_------ Coastal forest or thicket_____________________

Lumnitzera littorea.. ____________ Tree _______ Mangrove swamp and mangroye depression.

Morinda citrifolia. _______--__-_ Shrub._____ Strand and coastal forest or thicket.__________

Pandanus sp__-_-_-_-_________ Tree...---- Coastal forest or thicket_____________________

Pisonia grandis..- ________________do-_._________do_.__________-__---____---___________

Randia cocfo'ncJw'ne7m's____--__-____do_______ Coastal forest to low-hill forest, but not strand.

Rhizophora apiculata ______________do_______ Mangrove swamp_____-___---_-___--_______

R. mucronata. ____________________ do.___________ do.__________-__--___---_-_-_----__--_

Sonneratia a/6a__-_______.-_-_-----do______- Mangrove swamp and mangrove depression....

Terminalia catappa______________ do. ______ Strand and coastal forest or thicket ___________

Thespesia lampas..-.. _______--__-do_______ Upland forest, not strand____________________

Tournefortia argentea. _____________do_______ Strand and coastal forest or thicket.__________

i Kanehira (1933); F. R. Fosberg (written common., 1964).

Lumnitzera swamp he found 640 ppm chloride, or about 

3 percent of that in local sea water. Species of Bruguiera 

also grow in tidal-inlet mangrove swamp in Malaya 

(Richards, 1952). Thus, it is clear that Bruguiera can 

tolerate a wide range of salinity.

Fosberg (1949) described mangrove depressions as 

typically having Bruguiera or Lumnitzera growing on 

the lagoon side of swales and Rhizophora (presumably 

R. mucronata) or Sonneratia growing on the seaward 

margin of depressions. He stated, however, that Bruguiera and Lumnitzera usually occur in separate depressions and that each may be associated with Sonneratia.

As mangrove-depression ground water appears to be 

nearly fresh, this may have been an environment in 

which Callitriche could have grown at Eniwetok. 

Callitriche type pollen is found in the upper Rhizophora 

and the Chroococcalean zones.

Hatheway (1953) distinguished between the firmbottomed depressions with no outlet and the softer mudbottomed mangrove swamps along lagoon margins. He 

indicated that Rhizophora and Sonneratia, can grow in 

both environments, whereas Bruguiera is rarely found 

in open lagoonal environment.

The presence of fossil Bruguiera pollen suggests that 

an atoll mangrove-depression environment probably 

existed on Eniwetok in Miocene time. Rhizophora probably grew along the margins of Eniwetok lagoons near 

tidal passes, and Sonneratia may have been associated 

with both Bruguiera and Sonneratia.

The mangrove forms Ceriops and Avicennia are not 

known to grow in the mangrove communities in the 

Marshall Islands today; they do, however, belong to the 

so-called Indo-Malayan mangrove vegetation. On 

Ponape, which is the east limit of their present geographic range, Avicennia and Ceriops are associated

with Lumnitzera littorea, Nypa, Rhizophora apiculata, 

R. mucronata, Scyphiphor-a hydrophyllacea, Sonneratia 

alba, wcAXylocarpus granatum (Kanehira, 1933, p. 36). 

This vegetation grows in Kilonia Harbor at Ponape 

but occupies a relatively small area there.

With the exception of Xylocarpus, forms comparable 

to the taxa just mentioned are identified in the Miocene 

flora. Kanehira (1933, p. 213) observed that mangrove 

associations require intertidal mud in somewhat protected coastal indentations. Because the mangrove taxa 

are dominant in the Miocene flora and because their 

remains are so numerous at both drill-hole sites, we 

can suppose that conditions appropriate for mangroveswamp development existed on two sides of Eniwetok 

lagoon during Miocene time—in the vicinities of Parry 

Island and Elugelab Island.

PISONIA FOREST

Pure stands of Pisonia are among the most widely 

distributed types of atoll forests and in historical time 

may have covered the greatest area of any pure tree 

stands in the Marshalls (Wiens, 1962, p. 395). But pure 

Pisonia stands have been practically eliminated by man 

from larger atolls and are now largely replaced by 

coconut plantations (Fosberg, 1956). Hatheway (1953, 

p. 61) indicated that Pisonia grandis tends to grow in 

groves as large as 10 acres. Anderson (1951) described 

Pisonia on Arno Atoll as associated with Tournefortia 

and Cordia just above high-tide level on seaward 

beaches, and other authors have indicated that Pisonia 

most commonly grows in this environment today in the 

Marshalls.

Pisonia pollen makes two appearances in the drill 

holes. In the Chroococcalean algal zone, at 2,460 and 

2,470 feet, Pisonia pollen is the dominant type, although
MIOCENE POLLEN AND SPORE FLORA OF ENTWETOK ATOLL, MARSHALL ISLANDS 1161

only 12 grains of it were found; it appears at only one 

other level in the drill holes, at 810-820 feet in the 

upper Rhizophora zone. Associated with Pisonia in the 

Chroococcalean zone are rare pollen of Rhizophora, 

Callitriche type, and some unidentified dicot forms. It 

seems likely that Pisonia grew near the deposition site 

(Parry Island) at that time.

The occurrence of Callitriche type pollen in the same 

level as Pisonia pollen raises a question concerning a 

possible fresh-water environment at Eniwetok. Of 

interest here is Fosberg's (1955b) observation of freshwater ostracodes growing in an old hollow trunk of 

Pisonia on Bikar; the water in the Pisonia trunk was 

fresh. However, it seems unlikely that on a mid-Pacific 

atoll such an isolated environment could persist over a 

long period of time. Because the ostracode anomaly indicates that fresh-water animal forms can grow on atolls 

today, it seems possible that fresh-water plant forms 

could too. A few fresh-water plants occur in the present 

flora of coral atolls, and include L&mna, sedges, grasses, 

and many fresh-water algae (F. E. Fosberg, written 

commun., 1964).

The occurrence of a fresh-water planorbid snail 

(Gyraulus} and a brackish-water neritid (Neritilia) in 

sediments of Bikini drill hole 2B at depths below 1,700 

feet provides strong evidence that fresh-water environments did exist on Bikini during Miocene time (Ladd, 

1965). Occurrence of fossil endodont land snails like 

those that now live in forests of high islands also 

strongly indicates that( Bikini and probably Eniwetok 

were raised limestone islands at times during the early 

and late Miocene and Pleistocene(?) (Ladd, 1958). 

Apparently there was fresh and brackish water on the 

elevated Marshall Islands.

CHROOCOCCALEAN ALGAL ASSEMBLAGES

Fosberg (1956) described an association of microscopic blue-green algae as growing on beach rock, elevated reef rock, boulders, cobbles, and pebbles that are 

scattered on reef flats just above high-tide level. He 

stated that a crust of bluish-gray to blackish algae 

literally covers every type of exposed sedimentary material in this particular zone above high tide on coral 

atolls, and that the same crust grows equally well on 

noncoralline limestone in the tropical region.

Fosberg (1956, p. 210) observed that algal crusts of 

the same color form in areas of bare coral sand. These 

algae have a gelatinous consistency when wet, and sand 

grains are embedded in them. He pointed out that these 

algae "contribute in a very important way to stabilizing the sand and to initiating soil formation. It is probable that at least some of the species of algae are capable

of nitrogen fixation. In any event, the development of 

such crusts often represents the initial stage in establishment of vegetation on coral sand."

At Bikini, Taylor (1950, p. 103) identified three filamentous Myxophyceae algae and the gelatinous colonial 

Gloeocapsa^ a Chroococcalean alga, as the chief constituents of the sand crust.

At Eniwetok, Dawsoh (1957, p. 125-126) collected 

two kinds of Chroococcalean algae and described three 

others collected by other workers. He found the colonial 

form Anacystis dimidiata (Kutzing) Drouet and Daily 

(equals Gloeocapsa turgida (Kutz.) Hollerbach) growing as "scum on lagoon rocks" on Igurin Island. He collected another colonial form, Coccochloris stagnina 

Sprengelr on the seaward flats of Bokanjoio Island and 

in the lagoon and listed and figured several other bluegreen algae from Eniwetok.

Dawson's figured specimens of Gotnphosphaeria 

aponina Kutzing from Eniwetok closely resemble my 

specimens identified as GomphospJiaeria type (pi. 304, 

fig. 3). His illustrations of Anacystis ( = Gloeocapsa 

turgida} are very similar to my Gloeocapsa type (pi. 

304, fig. 5).

Modern sediments from the lagoon margin of Onotoa 

Atoll, Gilbert Islands, were found to contain as many 

as 4,200 Chroococcalean algal colonies per gram, which 

were mainly of the Olorogloea and Placoma types (pi. 

304, figs. 9-13).

The crustlike material from Eniwetok drill hole E-l 

(at 2,490-2,510 ft), sectioned by microtome and figured 

on plate 304, figure 19, is a cross section of a probable 

algal crust similar to the one described by Fosberg 

(1956). Although the morphology of the algal cells 

could not be discerned in the sectioned material, it 

follows Fosberg's description of brittle flat flakes that 

curl when dry. The crust material sectioned here was 

mainly organic. Upon laboratory maceration, the crusts 

were found to be composed almost entirely of Chroococcalean colonies of the Gloeocapsa type; no pollen or 

spores were present.

There is little doubt that the Chroococcalean zone is 

a deposit related to the algae-encrusted sand or reefrock flats described by Fosberg (1956). Whether the 

environment was lagoonal or seaward reef cannot be 

determined from the present material; however, the 

large number of blue-green algae in the sediments of 

the Chroococcalean zone in drill hole E-l indicates that 

the sedimentary surface was not far from sea level 

during that depositional interval. It should be stressed 

that these algae are light-dependent forms that cannot 

tolerate water of great depth.
1162 BIKINI AND NEARBY ATOLLS, MARSHALL ISLANDS

MIXED ATOLL FOREST VERSUS FOREST ON RAISED 

CORAL LIMESTONE

The primary difference between plant environments 

on atolls and those on raised coral limestone islands 

may be related to the comparative frequency of halophytic and mesophytic environments. "Strand vegetation, in general of course, indicates salinity" (Fosberg, 

1960, p. 20). In the interior of atoll islands the substantial number of plants that do not normally grow on 

strand lines is, according to Fosberg (1947), chiefly 

a reflection of differences in salinity of atoll soils. This 

differentiation of vegetation even on low atolls displays 

a trend toward mesophytic forest on the higher parts 

of the atoll.

The vegetation on elevated limestone is a modified 

strand type (Fosberg, 1960, p. 21), and boundaries 

between this and the atoll type of forest are difficult to 

delimit. Many of the atoll forest trees also occur on 

elevated limestone, and these include, from the Eniwetok flora, Morinda citrifolia, Pisonia grandis, Randia, 

Ixora, and Pandanus. Certain forest forms, such as 

Thespesia lam/pas and Gardenia, found on elevated limestone are never found on strand lines or on atolls.

During Miocene time, atoll-islet environments in 

which the atoll type of mesophytic forest could grow 

were certainly present at Eniwetok; Pisonia, Pandanus, 

Tournefortia, and perhaps Eugenia probably comprised 

that vegetation. Also, a raised-limestone environment 

where Thespesia lampas and Gardenia could grow was 

probably present.

LONG-DISTANCE TRANSPORT HYPOTHESIS

Because only a few pollen specimens represent the 

nonatoll forms (Gardenia and Thespesia cf. T. lampas) , 

one could assume that during Miocene time the pollen 

reached the site by wind transport from an upwind 

source. Long-distance transport by wind has been shown 

to be the source for a small percentage of the post glacial pollen flora of Tristan da Cunha (Hafsten, 1960). 

The inferred and only possible source was about 1,000 

miles away; the transported pollen, however, belongs to 

groups that are high pollen producers and are wind pollinated.

The source for the Eniwetok material probably would 

have been from the west, for centers of distribution for 

the two taxa are west of the Marshalls today. A longdistance-transport hypothesis requires consideration of 

two influential factors:

1. Wind direction. The trade winds now extant in the 

northern Marshalls emanate from the east and the 

northeast. The exceptions are either weak winds or 

winds from the south bringing storms. A shift in

basic wind patterns to account for a western source 

for the pollen types involved seems unlikely. 

2. Pollen characteristics in relation to long-distance 

transport. Both Thespesia and Gardenia have relatively large, heavy (thick walled) pollen; their 

respective families, which probably are insect pollinated, are in general poorly represented in the 

fossil pollen record even when member taxa are 

growing locally. Hence pollen of these genera are 

not likely candidates for long-distance transport 

by wind.

The assumption that favorable environments for 

these plants existed on Eniwetok during the Miocene 

seems reasonable. The ample evidence from fossil endodont land snails (Ladd, 1958) and the presence of extensive leached zones in the subsurface (Schlanger, 

1963) suggests that Eniwetok was in fact a raised limestone island capable of supporting forests during long 

periods of Miocene and later time.

SUMMARY OF ENVIRONMENTAL CONDITIONS

A chronological description of the inferred environments on Eniwetok, as indicated by fossil pollen and 

spores from the drill holes, may be summarized as 

follows:

Zone 1 (4,553-4,528 ft).—Low densities of Chroococcalean algae and pollen of land plants indicate that 

these Eocene (Tertiary &) sediments now only about 

100 feet above basement rock and 4,500 below sea level 

were near sea level when they were deposited.

Zone 2 (4<525-2,fi62 ft).—No plant fossil evidence. 

Pollen, if present after deposition, may have been 

oxidized during the period (s) of emergence in Eocene 

or Oligocene time.

Zone 3 (2.510-2,440 ft).—The great abundance of 

Chroococcalean algae and small amounts of pollen 

present in this depth interval in drill hole E-l indicate 

that these early Miocene (Tertiary e) deposits accumulated at or very near sea level. The palynological evidence corroborates the conclusion based on calcareous 

algae and Foraminifera that the sediments of this zone 

were deposited in shallow water and suggests that the 

environment was either lagoonal or seaward reef flat.

The association of Pisonia pollen with pollen of 

Rhizophora in the upper part of this zone indicates 

that a beach-ridge environment and tidal passes where 

Rhizophora could grow were not far from the area of 

drill hole E-l. The presence of probable Callitriche pollen near the top of this zone suggests that fresh-water 

environments ~\vere available on the island at this time.

Zone 4 (2,028-1,232 ft).—No pollen found at Eniwetok. Petrographic evidence indicates a major period 

of uplift and leaching at the end of this early Miocene
MIOCENE POLLEN AND SPORE FLORA OF ENIWETOK ATOLL, MARSHALL ISLANDS 1163

interval. In this zone at Bikini, fresh- or brackish-water 

mollusks were found (Ladd, 1965) and occurrence of 

endodont land snails suggests a high-island forest environment (Ladd, 1958). Also at Bikini, in drill hole 

2A, Pandanus and ?Palmae pollens suggest that strand 

plants grew on the island at this time.

Zone 5 (890-850 ft}.—The great abundance of both 

Chroococcalean algae and pollen in the lower Rliizophora zone (in drill hole F-l and above a depth of 880 

ft in E-l) indicates that the deposition sites were very 

close to sea level during late Miocene. The abundjanee of 

RMzophora pollen suggests that the environment was 

lagoonal rather than seaward reef—a conclusion supported by other fossil evidence. The presence of Bruguiera pollen suggests that mangrove depressions may 

have existed on the atoll at this time. Strand plant elements of the beach-ridge environment, Morinda, Pandanus, Terminalia, and Cordia, are present. Coastal 

and upland forest forms that do not grow on strand 

lines are present also and include Acalyplia, Thespesia 

cf. T. lampaSy and Rcmdia.

Zone 6 (840-820 ft).—Sonneratia zone. Because the 

dominant pollen form, cf. Elaeocarpus, is not identified 

with certainty this zone is difficult to interpret. Maximum pollen densities are greatly in excess of those now 

found in eastern Micronesian atoll lagoons; hence, the 

vegetation probably was far more luxuriant and occupied a larger land area then than now. The presence 

of Sonnemtia,) Lumnitzera, Ceriops, and Avicennia indicates that the mangrove communities were rich in 

species. Coastal forest forms (Ixora) and upland forest forms (Gardenia) were also present. High-island 

land snails in drill hole K-IB indicate that Eniwetok 

stood well above the sea during this part of the late 

Miocene (Ladd, 1958).

Zone 7 (820-670 ft).—Upper Rhizophor, zone. Mangrove communities continued to occupy Eniwetok at the 

end of the late Miocene and were locally dominated by 

Rhizophom. Mangrove depressions probably existed 

on the beach ridges (supposition based on the presence 

of Bruguiera) , and CaHitriche-type pollen suggests that 

fresh-water environments may have occurred locally 

on the island at that time. Atoll forest forms are scarce 

in the highest fertile sample, at 670 feet, and mangrove 

forms comprise almost the entire count. Coastal and 

upland forest forms (Thespesia cf. T. lampas, Ixora, 

and Randia] are present.

Zone 8 (625-170 ft] .—The two samples of post-Miocene sediments, as far as they have been examined, are 

barren of plant fossils. High-island land snails of probable Pleistocene age from this zone were found at 

Bikini (447-45$ ft; Ladd, 1958).

In summary, the abundance and kinds of pollens, 

pores, and colonial algae strongly support the theory 

that part of the Eocene and much of the Miocene sediments beneath Eniwetok were deposited near sea level. 

Evidence from vascular plants also supports the conclusion based on the presence of land snails (Ladd, 

1958) that a coastal and upland forest grew on Eniwetok during parts of the Miocene; the soils of that forest 

could not have been saline.

RELATION OF ENIWETOK MIOCENE FLORA

TO OTHER FOSSIL FLORAS, AND PALEOGEOGRAPHIC IMPLICATIONS

The Eniwetok Miocene flora has been compared with 

several pollen collections from Miocene(?) localities 

in Micronesia and Polynesia: Guam, Fiji, the Palaus, 

and Bikini. Correlation of Miocene sediments from these 

islands is discussed by Cloud (1953). Pollen from an 

undated Tertiary lignite of Rapa (Austral Islands) reported by Cranwell (1962, 1964) was compared with 

the pollen considered in this study as well.

Pollen from the Tertiary lignite of Rapa has little 

in common with the Miocene pollen flora of Eniwetok. 

Cranwell reported identifications of Coprosma, Myrtaceae, Liliaceae, Taccaceae, Piperaceae?, and Sapindaceae. Of these, Coprosma, a high-island member of the 

Rubiaceae, is tentatively identified in the Miocene of 

Eniwetok (pi. 311, fig. 37); unidentified members of 

the Myrtaceae are found in both floras. The other pollen 

identified from the Rapa material were not found in 

Eniwetok sediments.

The Miocene Airai Clay (Tayama, 1939) of the Palau 

Islands (US'GS paleobotany Iocs. D1182, D1186, D1317, 

D1647, D1648, D1649, D1650, and D1626) contains a 

rich flora of almost 100 pollen and spore forms that is 

very different from the flora at Eniwetok. Present in 

the .Airai Clay but absent from Eniwetok are a very 

distinctive palm, Lycopodiwn cf. L. phlegmaria, and 

Pteris, Schizaeal, Spatliypliyllum, Rubiaceae undet., 

Nyctaginaceae cf. Abronia, Sterculiaceae cf. Kleinhovia, Sida cf. 8. fallax, Sapotaceae cf. Northiopsis. 

Myrtaceae, Anacardiaceae cf. Campnospemw, and cf. 

Semecarpus, among other forms. In common with the 

Eniwetok flora are Avicennia, Terminalia, 2'inwnius 

or Guettarda, Pandanus, Rhizophora, Sonneratia, and 

CombretumL The present flora of Palau is, of course, 

very much more diverse than that of Eniwetok; also, 

because Palau is close to the continent, it shows a strong 

relation to the present flora of Malaysia. The Palau Miocene flora includes strand-line plants (Terminalia, 

Pandanus) , mangrove forms (Rhizopliora, Sonntratia) ,
1164 BIKINI AND NEARBY ATOLLS, MARSHALL ISLANDS

and probably high-island forms (cf. Campnosperma 

and others). The relation of this fossil flora to the Malayan flora of today cannot be defined from the present 

cursory study, but the Miocene flora from Palau is 

both larger and more complex than the one described 

from Eniwetok.

A Miocene sample of the Suva Series, Viti Levu, Fiji 

(USGS paleobotany loc. D1417), contains pollen and 

spores of cf. Casuarina, Schizaeaceae, Polypodiaceae cf. 

Botrychium, Morinda cf. M. citrifolia, and several unidentified fern spores. Another Miocene sample from the 

Suva Series (USGS paleobotany loc. D3277), Nasoranga Creek, Viti Levu, Fiji, contains the following 

forms:

Number of. 

grains in tally

Sonncratia cf. S. alba—————————————— 37

Rliisopliora ______————————————————— 21

cf. Bruguiera,-—————————————————— 1

?Palmae ____——————————————— 2

Tcrminalia, or Combretum___________________ 2

Anonaceae, Miliusa type.———————————— 16

cf. Timonius_——————————————————— 1

Pteris ________________—————————— 2

CyatJiea type________——————————— 5

Polypodiaceae types——————————————— 16

Humata or Davallia type_——___—____ 4

Vaginularia type-—_—————————————— 5

?Amaranthaceae _________________ 1

Undetermined dicotyledons——————-———- 23

Undetermined fern spores——-——_—__ 1

Total _____________________ 137

These results are mentioned by Ladd (1965), who described a fresh-water snail from the same Miocene rocks.

Of the plants identified, Sonneratia represents the 

most remarkable extension of range in the Miocene; the 

nearest modern occurrence of this Indo-Pacific genus is 

at Ponape in the southern Marshall Islands, 1,300 miles 

northwest of Fiji, and in New Guinea, about 2,100 miles 

west of Fiji. The fossil Miliusa type of Anonaceae is 

of interest because the family is not known to occur on 

Fiji today, although it is represented by several genera 

in Burma and Java. Rhizoplwra and Timonim, and 

probably Pteris, now grow on Fiji.

Samples of the Miocene Talisay Member of the Alif an 

Limestone on Guam (USGS paleobotany Iocs. D1653, 

D1652) yield the following assemblage: Pandanus, 

Anacolosa, Thymeliaceae cf. Wikestroemia, RJdzophora (pi. 308, figs. 63-65), IPisonia, Cotnbretwn or 

Termina.Ha, Ixora cf. 7. easel, and Phegopteris or Lastrea. The genera Anacolosa of the Olacaceae and Wikestroemia are Indo-Malayan; I could find no record of 

their occurrence in Micronesia today. Ixora, which also 

was found in the Miocene of Eniwetok is represented by 

three species in Micronesia, /. triantha being very common on Guam. The other pollen forms in the Guam flora 

represent mangrove and strand plants that occur in the 

Miocene of Eniwetok. Phegopteris and Lastrea are polypodiaceous ferns closely related to Thelypteris (Copeland, 1947, p. 136). Their spores are distinct from those 

of many other species of Polypodiaceae (95 species were 

checked). These genera now grow on Ponape and probably elsewhere in Micronesia; both are pantropical.

Only about five pollen grains were found in two 

Bikini drill-hole samples (Miocene) (USGS palebotany 

loc. D1416), and only Pandanus pollen could be identified. Palm pollen of the Livistona type was seen.

In summary, high-island plants were identified from 

Miocene or probable Miocene sediments from Guam, 

Fiji, Palau, and Eniwetok. Mangroves and associated 

forms were also found at Guam, Fiji, the Palaus, and 

Eniwetok. Strand plants were identified at these localities as well as at Bikini. These data indicate that certain of the strand plants now widespread in Micronesia 

(Pandanus, Tournefortia, Morinda, Cordia, Pisonia) 

were equally widespread there in the Miocene. Mangroves and their associates (Sonneratia, Rhizophora, 

Lumnitzera, and Avicennia) ranged much farther southeast and northeast than they do now. Indo-Malayan upland forms such as Anacolosa and Thespesia cf. T. 

lampas, and Indo-Malayan and Fijian forms, such as 

Gardenia, had greatly extended ranges during the 

Miocene, occurring at Guam or Eniwetok. These plants 

probably occupied high islands in Micronesia during the 

Miocene. Coastal forest forms (Acalypha, Randia*, and 

Ixora} grew somewhat east and north of their present 

Indo-Pacific ranges.

The plant evidence discussed here indicates that the 

present high islands of the Palaus, Fiji, and Guam were 

also high islands in Miocene time. Because their floras 

were enriched by Indo-Malayan forms, it is likely that 

more intermediate islands than now exist provided 

stepping stones that allowed the extension of IndoMalayan plant ranges into north-central and southeastern Micronesia.

Climatic change, particularly decrease in annual rainfall, may have been a factor in the disappearance of 

several Miocene taxa from Eniwetok. As has been 

pointed out (p. 1142), the existing north-south gradient 

in rainfall in the Marshall Islands group is reflected 

by a north-south gradient in diversity of the modern 

flora—a trend which seems somewhat independent of 

islet size. During an unusually dry season in 1951 in the 

northern Marshalls, Pisonia, Cordia, and Terminalia 

were partially defoliated in some places (Fosberg, 

1953). Short-term climatic fluctuations apparently affect the luxuriance of some species on atolls, and longer 

term shifts might eliminate more sensitive taxa.
MIOCENE POLLEN AND SPORE FLORA OF ENIWETOK ATOLL, MARSHALL ISLANDS 1165

The amount of precipitation is not solely a result of 

climate, but it is partly dependent upon land height 

above the sea. Hosakawa (1950) observed that in the 

same trade-wind belt in the equatorial zone, Kusaie, 

which has about the same land area as Truk but is 1.6 

times higher, receives 1.8 times more rain in the average 

year. If, for purposes of discussion, the Miocene climate 

of Eniwetok had been the same as it is now, Eniwetok 

would have received slightly more rainfall during the 

end of Tertiary g and e time (of Cole, 195Y) than now, 

because the presence of fossil land snails and certain 

plants have established that the atoll had a greater elevation then. Increases in precipitation that probably resulted from Eniwetok's higher elevation during periods 

of emergence were probably temporary because submergence followed emergence.

In evaluating the possible effects of overall climatic 

change on the late Cenozoic vegetation of Eniwetok, one 

should bear in mind that at least four of the Miocene 

plant taxa now absent from the atoll are raised limestone island forms (table 6) that cannot tolerate saline 

soils. The relative availability of mesophytic environments on Eniwetok thus has been an important limiting 

factor in the survival of the raised-island flora. In view 

of the obviously important tectonic history of the northern Marshalls, it is reasonable to assume that relative 

rates of submergence and emergence controlled the overall availability of land environments and, hence, the 

impoverishment of the flora.

Possibly at times during the post-Miocene, Eniwetok 

was completely submerged, and the present flora may be 

the result of recolonization of the atoll by strand and 

atoll forms. The present Eniwetok flora is primarily of 

southwestern Pacific distribution, and no outposts of 

the Micronesian flora now occur east of the Marshall 

Islands; hence, it does not seem reasonable to assume 

that the last recolonization came from eastern sources 

(for example, by means of the easterly trade winds and 

ocean currents). However, the present storm patterns 

from the south may have prevailed in Pliocene and 

Pleistocene time and could have served to transport 

seeds or fruits to Eniwetok from Kusaie or Ponape, 

about 400 miles south and 400 miles southwest of the 

atoll, respectively.

Modern mangrove communities at lagoon margins 

seem to require quiet tidal embayments. The height of 

the atoll islets perhaps in part controls the vulnerability of atoll lagoons to typhoon damage, and if so, the 

relative relief on atolls may affect the diversity of mangrove associations. The local extinction of mangroves

from Eniwetok may have been aided by typhoon damage 

during a time when subsidence provided low relief.

In summary, the post-Miocene elimination of the 

high-island and atoll forest forms from the Eniwetok 

flora may have been primarily the result of subsidence; 

the effects of secular climatic change on floristic impoverishment may have been incidental during the late 

Cenozoic.

SYSTEMATIC DESCRIPTIONS

ANGIOSPERMAE

MONOCOTYLEDONAE

PANDANACEAE

PANDANUS Rumph. ex. L. 

Plate 305, figures 16,18,19

Pollen monoporate; 14-17fiat equator, and 21-23 n 

in polar dimension. Wall of one layer, 1 /* thick at proximal pole and thinning to distal pole where pore is situated. Pore circular, 4-5 ju, in diameter, and simple, with 

no marginal thickenings. Spinules on outer surface 

0.75-1 fj. in length and distributed 2-3 /* apart.

Comparative material.—Fossil Pandanus pollen was 

compared with modern pollen of P. tectorius Sol. (pi. 

305, fig. 17) and P. kafu Martelli. There is little morphologic difference between these modern Pandanus 

collections. Other authors (Selling, 1947, p. 340; Cranwell, 1953, p. 31) have found that pollen morphology is 

quite uniform within the genus.

Fossil occurrence.—In Eniwetok drill hole E-l at 

850-880 feet and in drill hole F-l at 810-840 feet, rare 

(about 1 percent total pollen and spores). Bikini (US 

GS paleobotany loc. D1416-2), in drill hole 2A, core 

2A-36-2, at depths 929-935.5 feet, one specimen. Guam, 

Miocene Talisay Member of the Alifan Limestone 

(USGS paleobotany loc. D1653), one specimen. Palau 

Miocene Airai Clay (USGS paleobotany loc. D1186), 

several specimens.

Present distribution.—The genus Pandanus has wide 

distribution in the South Pacific, and many endemic 

species occur in Micronesia. The genus ranges from 

Hawaii and the Henderson Islands to Africa. Eight 

species are thought to be native to Eniwetok, according 

to St. John (1960), but F. K. Fosberg (written commun., 

1964) considered all specimens to belong to P. tectorius.

Ecology.—Fosberg (1955a, p. 3) stated that in the 

northern Marshalls Pandanus species grow in mixed 

forest stands. On Arno Atoll in the Marshalls Pandanus 

grows on the wetter shores of the lagoon along with 

TerminaUa samoensis Rech.
1166 BIKINI AND NEARBY ATOLLS, MARSHALL ISLANDS

?PAIMAE 

LIVISTONA R. Brown

Livistona type 

Plate 305, figure 20

Pollen monosulcate; 27-29 /* at equator, and 13-15 p 

in polar dimension. Wall 1 /* thick in proximal hemisphere, thinning toward sulcus. Sulcus passing through 

distal pole and extending to equator. Margins of sulcus 

inrolled toward cell lumen. Wall surface appears 

smooth except under oil, and then very finely granulate 

or shagreenate. Not apparent whether Avail is two layered, even under oil.

Comparative material.—This form was compared 

with a wide range of monbcotyledonous groups and 

with Cycas in the Gymnospermae. Though Cycas grows 

in Micronesia today, the boatlike shape of Cycas pollen 

is unlike the shape of the fossil material. The sulcus of 

Cycas pollen does not ordinarily reach the poles, 

whereas sulci of the fossils pass through the polar 

area. Many members of the Palmae have monosulcate 

pollen, and in some the pollen wall is nearly smooth, as 

in Ptychosperma and Erythaea. Pollen of the genus 

Livistona (pi. 305, fig. 19) is of the same average size 

and wall thickness as the fossil material and has a very 

similar shape in the contracted grains but a clear granular sculpture. The fossil material compares favorably 

with pollen of palm genera such as Livistona; however, 

this is not a positive identification even on the family 

level.

Fossil occurrence.—Code species Ci-sm (1) in Eniwetok drill hole E-l at various depths between 870 and 

2,510 feet and in drill hole F-l at 670-830 feet, rare 

(less than 2 percent of total pollen and spores). Bikini 

(USGS paleobotany loc. D1416-2), core 2A-37-15, at 

935.5-946, one specimen.

Present distribution.—Palms are not now indigenous 

to the northern Marshalls. Livistona now occurs on 

the Bonin and Eyukyu Islands and from Formosa to 

Australia.

DICOTYLEDONAE

NYCTAGINACEAE

PISONIA L.

cf. P. grandis R. Brown 

Plate 306, figures 1, 5

Pollen tricolplate, subprolate; 34-44 /* in polar dimension and 26-35 /* in equatorial diameter. Colpae extending four-fifths of way from equator to poles; colpal 

margos well defined, and about 1 /* in width. Wall characteristically folded inward to lumen under colpi; 

hence, what appear to be margos on plate 306, figure 1,

are partly folds where wall bends inward into iumen. 

Sculpture scabrate. Wall 1.5 p. thick; ektexine thicker 

than endexine.

Comparative material.—Comparative material includes Pisonia grandis (pi. 306, figs. 2-4), Ceodes umbellifera (Forst.) Seem., and six other Nyctaginaceous 

genera. According to Erdtman (1952, p. 285), the genus 

Ceodes, which is closely related to Pisonia, has "minute 

spinules'' on the scabrate pollen wall. Selling (1947, 

p. 99) stated that these features are probably minute 

projections that might be interpreted as vestiges of 

true spines, which are a common feature in this family. 

My Ceodes material displays small projections among 

the smaller scabrae that seem to confirm Selling's interpretation. Pisonia grandis either lacks these "spinule" 

projections, or they are small and hard to see. Pollen of 

both genera have simple colpi that are not folded inward to the lumen in fresh imcontracted material. 

Pisonia grandis pollen is mainly contracted and infolded after acetylation; only about half the Ceodes 

pollen grains contracted after acetylation. Ceodes 

pollen, which has 6-12 rugate colpi, tends to contract 

along three parallel latitudinal lines, and closely resembles Pisonia pollen in the contracted state; however, Ceodes pollen is nearly isodiametric in shape, 

whereas Pisonia is subprolate. Selling's (1947, pi. 2, figs. 

39,40) figures of Rockia pollen indicate that it is closeily related to Pisonia, though its wall is tectate according 

to Erdtman (1952, p. 285).

The fossil specimens are identified as contracted 

grains of Pisonia; they display what seem to be welldeveloped margos along the colpi but are simple folds 

marking the place where the wall bends inward to the 

lumen.

Fossil occwm*ence.—In two samples only, at 2,460- 

2,470 feet in drill hole E-l, 12 specimens; and at 810- 

820 feet in drill hole F-l, one specimen. Miocene Talisay member of the Alifan Limestone, Guam (USGS 

palebotany loc. D1653), one specimen.

Present distribution*.—Pisonia grandis is widespread 

in Micronesia: Moluccas, northwestern Australia, the 

Pacific islands, and east to the Palmyra Islands and 

Tuamota Archipelago; it is absent from Bonin Islands. 

The genus is also Indo-Malayan and American.

Ecology.—Pisonia grandis is a tall tree with a large 

crown. It grows in mixed stands (commonly in pure 

stands) on atoll ridges and dunes; on Arno Atoll it 

grows on the seaward slope on the windward islets but 

does not grow on the leeward islets (Anderson, 1951, 

p. 3). Fosberg (1955b) described a phosphatic hardpan 

under humus as a soil characteristic of a Pisonia forest 

floor.
MIOCENE POLLEN AND SPORE FLORA OF ENIWETOK ATOLL, MARSHALL ISLANDS 1167

EUPHORBIACEAE 

ACAIYPHA L.

Plate 306, figures 9,10

Pollen triporate; single specimen found measures 

25 by 26 /x in polar view. Pollen circular to somewhat 

intersemiangular in polar view; pores appear to be 

circular in outline and are from 2.5 to 3 /x in diameter. 

Pore rim protrudes very slightly relative to overall 

shape of cell. Endexine thickens as a costa under pore 

lip; as seen in cross section, thickening is wedge shaped, 

whereas ektexine is same thickness at all points on equator. Two wall layers are fused at pore lip to form simple 

pore margin. Wall is 0.8 /x thick at equator in interpore 

area and 1.5 /x thick at pore lip. Sculpture under high 

dry lens appears scabrate; however, analysis under different focal levels with an oil lens reveals that connected 

muri and poorly defined probably shallow lumina form 

vague microreticulate pattern. Lumina are about 0.8 /x 

in width and muri between them are about the same 

thickness.

Comparative material.—Six collections, including 

five species of Acalypha, were examined for this identification: A. alopecuroides Jacq., A. californica Benth., 

A. grandis L., A. leptopoda Muell., A. lindlieimeri 

Muell., and a specimen identified only as Acalypha sp. 

(pi. 306, figs. 11, IT-19) collected from Ponape by Glassman. These pollen collections all show costae under the 

pores as just described for the fossil and have from 

three to five pores, but in most of them the pollen walls 

are smooth. Only the collection from Ponape has sculpture and cell shape comparable with those of the fossil. 

The average size of the Acalypha sp. pollen from Ponape is 19 /x, with a maximum dimension of 22 /x (in 

polar view). The fossil is 30 percent larger than specimens from this modern collection; however, the great 

similarity in morphology and structural details makes 

Acalypha a certain generic determination for the fossil.

Fossil occurrence.—In drill hole F-l at 840-850 feet, 

one specimen.

Present distribution.—Three Micronesian species of 

Acalypha were recorded by Kanehira (1933) ; two are 

pantropic (A. hispida Burm. f.; A. indica L.), and F. 

K. Fosberg (written commun., 1963) thought that these 

were introduced in Micronesia; and one is Malayan and 

Micronesian (A. grandis}. Others, A godseffiana Mast. 

and A. hispida Burm. f., grow on Likiep, and A. ^oilkesiana M. A. grows on Ailuk Atoll, but all are considered 

to be introduced (Fosberg, 1955a). Merrill (1929) listed 

another species, A. caturus Blume, as a shrublike tree 

on forested ridges in Borneo.

Ecology.—The genus includes about 400 species, all 

tropical; most are woody, but some are herbaceous. The 

habitats of the Micronesian forms include secondary

scrub and forest margins on Truk and upland thickets 

on atolls near Palau.

MALVACEAE 

THESFESIA Soland.

cf. T. lampas (Cav.) Dalz. ex. Dalz. and Gibs. 

Plate 306, figures 22, 23

Peri-brevicolporate; suboblate; one specimen measures 65 by 53 /x without including projections; a second 

broken one is at least 65 /x in one dimension. Colpi 

slitlike, measuring 6-9 by 1-2 /x. Pores internal, oval, 

about 4 by 6 /x. Five apertures; four of these appear to 

be in one plane but colpi are not parallel to each other; 

fifth is in separate plane. Eim of endopore marked with 

endexinal thickening.

Wall thickness ranges from 2 /x in the areas between 

the sculpture projections to 5 /x at the base of the projections. Endexine is 1-1.2 /x thick except on the margins of endopore, where it swells to 2.5 /x. Ektexine 

ranges from 1 /x thick in the areas between sculptural 

projections to 4 /x thick immediately at the base of the 

projections. Ektexine is composed of vertical unbranched collumellae about 0.5 /x thick fused into a closed 

tectum. Small rounded projections appear to protrude 

above the tectum, so that the sculptural topography is 

scabrate,, The major wall projections are baculae and 

clavae 6-8 /x long and 2-2.5 /x wide; they are slightly 

thicker at the base and tip than in the middle. These 

are curled and bent; none seem to stand erect on the 

pollen wall. About nine projections occur on each 

hemisphere.

Comparative, material.—The fossil was compared 

with herbarium collections of eight genera and 16 species of Malvaceae and with figures and descriptions of 

10 other Malvaceous genera, including 19 species. Comparisons were made with five species of Thespesia. Also 

considered were Ipomaea of the Convolvulaceae, Eriolaena and Dombeya of the Sterculiaceae, and Montezuma, Hampea, and Matisia of the Bombacaceae; these 

have pollen similar to the pattern of the Malvaceae. 

Among these, however, only Thespesia lampas and T. 

peekelii have pollen comparable to this fossil.

Thespesia lampas (Cav.) Dalz. ex Dalz & Gibs, pollen 

(pi. 306, fig. 26), of which two collections were observed, 

has heteromorphic projections in some specimens; 

some grains have only straight spines, but some are 

heteromorphic having spines, clavae, and baculae. The 

projections are moderately crowded (about 12 per 

hemisphere), usually have swollen bases, and are in 

many cases bent or curved. Though the fossil does not 

possess spines, the clavae and baculae of the fossil 

closely resemble the comparable projections in T. lampollen.
1168 BIKINI AND NEARBY ATOLLS, MARSHALL ISLANDS

TJiespesia peeJcelii (Ulbr.) Borss. (equals Cephalohibiscm peeJcelii Ulbr.) has projections which are clavae 

and baculae, with somewhat swollen bases, and which 

are sometimes bent or curved and occasionally branched. 

The projections are more crowded than those of the 

fossils but their resemblance to those of the fossils is 

striking.

The apertures of TJiespesia peeJcelii and T. lampas are 

four to six forevicolpori, some of which are arranged in 

a single plane and some not. In some modern grains the 

apertures appear to be narrow slits, but in most the 

endopores 'are clearly evident. The microstructure of the 

wall in the fossils is similar to that in both of these 

modern species, except the fossils lack the spines which 

are the dominant projection type in T. lampas.

Pollen of Thespesia patellifera Borss., T. multibracteata Borss., and T. fissicalyx Borss. have sharp spines or 

echinae and so do not resemble the fossils. T. populnea 

(L.) Soland., the common pantropical strand species, 

has sharp or blunt spines that are sometimes branched 

and are usually crowded (from 12 to 30 per hemisphere), but it has no baculae or clavae. In summary, 

Thespesia lampas and T. peeJcelii are the only species 

thus far found in the Malvaceae which have baculae, 

clavae, and the structure comparable with those of the 

fossils.

Fossil occurrence.—In drill hole F-l one specimen 

at 670-680 feet and a broken specimen at 840-850 feet.

Present distribution.—T. lampas occurs in the tropics 

of India, Burma, China, Malaya, Philippines, the 

Celebes, Java, and Borneo. I cannot find records of it 

in Micronesia. The genus contains some 18 species, all 

tropical, and occurs in Africa, the Caribbean area, and 

Asia. T. peeJcelii occurs in New Guinea, New Britain, 

and the Solomons. T. populnea Soland. ex. Correa, 

which the fossil does not resemble, is the only Micronesian species of this genus and is widespread in Micronesia, as well as in Southeast Asia. The genus does not 

now occur on Eniwetok but does grow on Kwajalein 

Atoll where it is planted (Fosberg, 1955a).

Ecology.—T. lampas is a lowland forest tree. T. 

peeJcelii is an upland forest tall tree (occurs at 3,250 ft 

elevation in New Guinea). T. populnea is a mediumsized tree that occasionally occurs in the coastal forests 

of Micronesia. Fosberg (I960, p. 45) observed T. populnea growing with Bruguiera in a mangrove swamp 

and with Pisonia in the strand zone on Saipan.

SONNERATIACEAE 

SONNERATIA L. f.

cf. S. alba J. Smith 

Plate 307, figures 1-6, 12-21

Pollen triporate; prolate in equatorial view, ranging 

from 38 by 24 to 53 by 33 ju in size. No polar views were

available. Canted equatorial views suggest circular outline in polar view, with pores protruding. Pore margins 

granular; pores round from 3 to 4 /* in diameter. 

Meridional endexinous thickenings in the interpore 

area have 2-3 meridional thin areas as bands between pores, and these areas resemble colpi, though 

all do not coincide with the pores. One of these inward folds is shown in optical section on plate 307, 

figure 1. The linear thickenings seem to form structural axes for folding, and usually there are at least two 

well-developed wall folds between each pair of pores, 

as shown on plate 307, figures 2-4. The wall folds sometimes pull the pore margo inward so that only part of 

it protrudes. These pores seem to be partly hidden 

behind the folds, as on plate 307, figures 12-21. Sculpture is scabrate or lacking at the poles, and coarsely 

scabrate or verrucate at the equator. Wall ranges from 

1.5 to 3 //, in thickness. The endexine is smooth except 

for surface of endexinal thickenings, which appears 

granular on the underside (pi. 307, fig. 1). Ektexine is 

strikingly different in polar and equatorial areas: at 

the poles it is composed of crowded vertical elements 

which are fused in a tectum that sometimes has small 

scabrate projections as surface sculpture, but at the 

equator the ektexine is reduced to simple verrucae (or 

scabrae in some individuals) and does not form a tectum.

The unique morphology of this pollen seems to be 

restricted to the genus Sonneratia of the Sonneratiaceae. 

The only other modem pollen known to me that seems 

comparable is that of Santalum of the Santalaceae. 

Cookson and Pike (1954, pi. 2, figs. 67-70, 72) figured 

early Tertiary pollen of the Santalum type under the 

name Santalumidites Cookson and Pike (p. 209), and 

in addition they figured one grain (pi. 2, fig. 71) from 

the Pliocene of New Guinea which I believe should be 

assigned to the living genus Sonneratia, not to Santalumidites. Miocene and younger occurrences of Sonneratia pollen are reported from Borneo by Muller (1964), 

who distinguishes between S. caseolaris (L.) Engl. 

pollen in Miocene beds and S. alba pollen which first 

appears there in Pliocene beds.

Though Erdtman (1952, p. 413) indicated that the 

pollen of Sonneratia is very similar to the pollen of 

Diplusodon, a Brazilian genus of the Lythraoeae, the 

meridional thickenings are absent from Diplusodon.

Comparative material.—The fossils were compared 

with pollen of Sonneratia alba J. Smith, some specimens of which are figured on plate 307 (figs. 7-11, 

22-24). The three medidional thickenings in the interpore area are clearly shown on figure 9; this specimen 

apparently represents a turgid grain that has undergone no folding. Figures 10 and 11 show that folding 

is not always bilaterally symmetrical in Sonneratia,
MIOCENE POLLEN AND SPORE FLORA OF ENIWETOK ATOLL, MARSHALL ISLANDS 1169

and similar deviations are found in the fossil material 

(pi. 307, fig. 19).

Because the fossils range in polar dimension from 

about 25 to 54 /* and show some variation in sculpture 

pattern, it is possible that two different species are represented in the Eniwetok material. Lacking a variety of 

comparative material, however, I have chosen to treat 

them as one form in the present study.

Fossil occurrence.—In drill hole E-l at 850-860 feet, 

rare. In drill hole F-l at 820-840 feet, rare (maximum 

3 percent of pollen and spore tally). Miocene Airai Clay, 

Palau (USGS paleobotany loc. D1626), several specimens. In Suva Series, Viti Levu, Fiji, Miocene sample 

(USGS paleobotany loc. D1417), several specimens. A 

similar form from Pliocene of Borneo was reported by 

Muller (1964).

Present distribution.—The genus has six species of 

Indo-Malayan distribution; of these, the only species 

now known from Micronesia is S. alba. It grows in the 

Carolines and in the southern Marshalls on Arno and 

Jaluit Atolls (Mahabale and Deshpande, 1957). The 

present distribution of the genus is shown in figure 339.

Ecology.—On Arno Atoll, S. alba inhabits saline 

mangrove swamp depressions, where it is associated 

with Bruguiera and Lumnitzera (Anderson, 1951).

RHIZOPHORACEAE 

RHIZOPHORA L.

The fossil material of Rhizopliora seems to represent 

two basic types of morphology: pollen with strongly 

developed costae and a tendency toward a somewhat 

prolate shape (pi. 308, figs. 7, 8), and pollen with weak 

costae and a spherical shape (pi. 308, figs. 20,21,26,27). 

The latter are referred to as cf. R. mucronata and the 

former as cf. R. apiculata. Other distinctive forms (pi. 

308, figs. 46-48) which are referred to Rliizoplwra,\\&v§ 

a long prolate shape and rather well developed costae 

under the colpi and under the equator; these are referred to Rliizophora sp.

cf. R. apiculata Bl. 

Plate 308, figures 1-8, 19

Pollen tricolporate; spherical to prolate spherical, 

ranging from 17 by 16 to 18 by 17 //, in size. Polar views 

show RMzoplwra sp. to be circular, mostly with colpi 

open. From an equatorial view, colpi have parallel 

margins and are long, extending three-fourths of the 

distance to the poles. Costae along the equator are very 

clear in both equatorial and polar views. They are composed of endexine and are as much as 2 //, wide in the 

pore area, as can be seen by their outlines in plane view 

on plate 308, figures 1-5. In a canted specimen (pi. 308, 

fig. 7, 8), the costae appear to be very thin (about 1 //.)

in the intercolpal area and very thick (about 3 //.) in 

the colpus area. In polar view their outlines may be represented by the characteristic dark circle 1.5-2 //. wide 

within the inside circumference of the equatorial belt 

(pi. 308, fig. 17), but in this view the true thickness of 

the equatorial costae is probably distorted by the curvature of the wall. Grains in polar view were not assigned 

to subgeneric taxa, but the dark inner circle formed by 

these costal thickenings is a characteristic that permits 

the assignment of these grains to Rhizopliora. The pores 

may be defined as the area of intersection of the equatorial costae with the colpus margins and range from 

about 2 by 3 to 3 by 3 //, in size.

Costae that underlie the colpal margins are rounded 

and wedge shaped in optical section, and they are thickest (as much as 2 /*) just beneath the pore rim, where 

the total Avail thickness is about 3 //..

Sculpture is lacking. Wall layers are of about equal 

thickness at the poles, but endexine is thicker than 

ektexine at the equator and along the furrows. Total 

wall thickness ranges from 1.5 to 3 //,.

Canted polar and equatorial views may be seen in the 

clump of Rliizopliora pollen shown on plate 308, figure 

19. Clumps of this type, which are common in the Eniwetok material, are probably young pollen grains from 

RJiizoplwra anthers that fell into the lagoon before anthesis. Though some plants that are high pollen producers occasionally release clumps of pollen grains, 

according to Rempe (1937, p. 103), this occurrence is 

extremely rare. Clumps of pollen from a high pollenproducing plant such as Rhizopliora may be construed 

as representing the contents of a young anther, and 

probably the parent plant was near the site of 

deposition.

Comparative material.—Collections for comparative 

purposes include the following species: Rhizopliora 

mucronata Lam. (four collections), R. apiculata (one 

collection), and R. mangle L. (two collections). Material of R. apiculata appears to have a somewhat more 

prolate shape and better developed costae than that of 

R. mucronata Lam. R. mangle (pi. 308, figs. 36, 37) differs from both in having a far more prolate shape and 

more strongly developed costae along the colpi but 

weak equatorial costae. In addition, it is considerably 

larger than pollen of R. apiculata or R. mucronata.

The fossil material resembles R. apiculata in having 

strongly developed costae at the furrows and the equator but is more nearly spherical in shape.

Fossil occurrence.—In drill hole E-l at 2,450-2,470 

feet, two specimens found, and at 850-880 feet, common (as much as 30 percent of the pollen count). In 

drill hole F-l at 840-860 feet, dominant (as much as 

60 percent of the pollen count), and at 670-830 feet,
1170 BIKINI AND NEARBY ATOLLS, MARSHALL ISLANDS

rare to dominant (0.7 to about 58 percent). Talisay 

member of Alifan Limestone (Miocene), Guam (USGS 

paleobotany loc. D1653, D1652), many specimens. Airai 

Clay (Miocene), Palau (USGS paleobotany loc. 

D1626), many specimens. Suva Series, Viti Levu, Fiji 

(Miocene sample; USGS paleobotany loc. D3277), 21 

specimens.

Present distribution.—Rhizophora is pantropical. R. 

apiculata is Indo-Malayan and occurs in the Philippines, Melanesia, and Polynesia; in Micronesia it occurs 

in the Carolines as far east as Kusaie. R. mangle, a 

South American species, is introduced on Eniwetok (St. 

John, 1960).

Ecology.—R. apiculata grows in association with R. 

mucronata in salt-water mudflats, where tidal channels 

flood the flats at high tide (Fosberg, 1960). The mudflats 

Avhere these species grow are generally at exactly mean 

sea level.

cf. R. mucronata Lam. 

Plate 308, figures 20, 21, 26, 27

Pollen tricolporate; spherical to prolate spheroidal; 

ranging from 18 by 18 to 20 by 18 /* in size. In equatorial view, colpi are uniformly 1 p wide when closed (pi. 

308, fig. 26) and as much as 2 /* wide when open (pi. 308, 

figs. 20, 21). Colpi are long, extending three-fourths 

or more of distance from equator to pole. Costae along 

equator are less well developed than those in R. cf. apiculata and often are not well defined between pores (pi. 

308, figs. 20, 21). Maximum wall thickness in colpus 

area is about 1.5 ytt, including both wall layers. Equatorial costae are thin to absent in interfurrow area. Specimens presenting polar views were not identified to subgeneric level, but all those assigned to Rhizophora displayed a discernible equatorial thickening; some were 

exceptionally thick (pi. 308, fig. 17).

Sculpture is lacking except at poles; ektexine at poles 

in many grains shows columellae or tiny clavae with 

heads crowded together, giving an apparent roughness 

to sculpture (pi. 308, figs. 20, 26). Wall layers are of 

about equal thickness in many parts of grain; total wall 

thickness ranges from 1 to 1.5 /*.

Comparative material.—Collections, used for comparative purposes are the same as those listed for Rhizophora cf. R. apiculata (p. 1169). The fossil material resembles R. mucronata in having poorly developed 

costae, both equatorial and colpal. The polar wall structure that provides a rough sculpture in that area of some 

fossil grains is a feature not found in modern R. mucronata material, however. A somewhat rough sculpture 

is seen on some Rhizophora mangle grains (pi. 308, fig. 

36), but it does not seem to be limited to the polar areas, 

indicating that the fossil material may represent either

a modern species not included in the comparative material studied here or an extinct species.

Fossil occurrence.—In drill hole E-l at 2,460-2,470 

feet, one specimen found, and at 850-880 feet, common 

(about 31 percent of count). In drill hole F-l, at 840- 

860 feet, rare (less than 6 percent of count), and at 670- 

820 feet, rare (less than 2 percent of count).

Present distribution.—Present distribution is the 

same as that for R. apiculata except that this species 

ranges farther eastward into the southern Marshalls 

(Fosberg, 1960).

Ecology.—Same as that for R. apiculata.

RHIZOPHORACEAE 

BRUGUIERA Lam.

cf. B. gymnorhiza (L.) Merrill 

Plate 308, figures 31, 32, 40

Pollen tricolporate; prolate spherical; ranging from 

16 by 16 to 18 by 17 ^ in size. Specimens presenting polar 

views could not be assigned to Bruguiera with certainty. 

Colpi observed are all closed, and have parallel margins. Endexinal costae well developed immediately 

under colpus margins and, when viewed from above, 

appear as a thin dark line in the position of a margo. 

(Note center furrow, pi. 308, fig. 32.) Viewed at an 

angle or in optical section, these costae appear very 

prominent indeed and are about 1 p. thick. (See left and 

right furrows, pi. 308, fig. 32.) Costae are discontinuous 

across the equator, as they are absent under the pores. 

The pores are slitlike, their longest dimension is in the 

plane of the equator, and they are about 1.5 by 3.5 p in 

maximum size. True equatorial costae do not seem to be 

present in this form; however, there is a thinning 

of the endexine in the equatorial area on each side of 

each pore, perhaps representing a reduced equatorial 

girdle. Sculpture is lacking. Wall layers are of equal 

thickness and have a maximum total thickness of 2 /*.

Comparative material.—Comparative material includes three collections of Bruguiera gymnorhiza. The 

fossil material is similar to modern B. gymnorhiza in all 

respects. It differs from pollen of Rhizophora as it lacks 

equatorial costae and from Ceriops as it is larger and 

has a more prolate shape.

Fossil occurrence.—In drill hole E-l, at 850^-880 feet, 

less than 1 percent. In drill hole F-l, 670-820 feet, less 

than 2 percent. Suva Series, Viti Levu, Fiji (Miocene 

sample; USGS paleobotany loc. D3277), one specimen.

Present distribution.—The genus is Indo-Pacific. B. 

gymnorhiza grows in Indo-Malaya, New Guinea, the 

Marianas, the Carolines, and the Marshall Islands. In 

the southern Marshalls it is present on many of the 

atolls; in the northern Marshalls it has been found 011
MIOCENE POLLEN AND SPORE FLORA OF ENIWETOK ATOLL, MARSHALL ISLANDS 1171

Lae, Likiep, Utirik, and Ailuk, and a few specimens 

are reported from Bikini (Fosberg, 1960). It is probably not limited to these atolls but merely has not been 

collected on the others. However, it has most likely 

been spread by the Marshallese, who used it, according 

to F. E. Fosberg (written commun., 1964).

Ecology.—Bmguiera can grow farther inland and 

in fresher water than either Sonneratia or Rhizophom. 

In the Marshalls it occupies mangrove depressions on 

the higher parts of the atoll islands (Fosberg, 1947, 

1960).

CERIOPS Arnott

cf. C. tagal (Perr.) C. B. Rob. 

Plate 308, figures 41-43

Pollen tricolporate; spherical to prolate spherical; 

ranging from 13 by 13 to 12 by 13 ju, in size. Colpi 

vague, extending one-half to three-fourths of the distance from equator to pole. Pores elongated along equatorial plane, with dimensions of about 2 by 4 /*, their 

poleward margins very slightly thickened by endexine. 

Endexinous costae line the inner margins of colpi resulting in maximum wall thickness of 2 /* under poleward margins of pore. Equatorial costae not evident. 

Sculpture lacking. Wall layers of equal thickness in 

intercolpal areas, and average wall thickness of about 

1 p.

Comparative material.—Includes three collections 

of Ceriops tagal pollen.

Fossil occurrence.—In drill hole E-l at 850-860 

feet, less than 1 percent. In drill hole F-l, at 670-860 

feet, as much as 13 percent.

Present distribution.—One species, Ceriops tagal, 

occurs in India, Malaya, the Palaus, and on Yap.

Ecology.—Ceriops tagal is a small tree growdng in 

mangrove swamps. In Borneo, Merrill (1929, p. 214) 

observed the species growing "on saline soil"; he stated 

that in India and Malaysia it grows "along the seashore and tidal streams."

COMBRETACEAE 

TERMINALIA L.

cf. T. catappa L. 

Plate 309, figures 1-5

Pollen tricolporate, with three distinct pseudocolpi 

in intercolpal areas; prolate; ranging from 18 to 19 /* 

in equatorial diameter and from 19 to 23 /* in polar 

dimension. Colpi extending about two-thirds of distance from equator to pole. Pore not evident from polar 

view, but as seen from above in equatorial view is rectangular with rounded corners and 4 by 5 /* in maximum size; its long axis lies along equator. At its intersection with equator, pore is extended as two thin

straight line slits. Terminalia and Combretum may be 

distinguished in equatorial view by this feature: Combretum lacks the slits and usually has less distinct, often 

rounded or figure-eight-shaped pores. Because some 

Terminalia grains do not show a distinct pore, not all 

equatorially oriented specimens of the two genera can be 

distinguished.

Wall thickest, 1.5 /*, 'at costae near the colpus margins ; farther toward colpus opening, wall thins to membranous margin which sometimes lies flat with surface 

of grain and often projects slightly outward (pi. 309, 

fig. 1). Margin rarely folds inward in cf. T. catappa; 

where it does, grain appears to have six colpi, for the 

colpi resemble pseudocolpi that lie between them 

(pi. 309, figs. 3,4).

Sculpture is lacking or granulate under oil. Wall is 

clearly two layered and simple, outer layer thinner than 

inner at most points.

Comparative material.—Comparative material includes four collections of Terminalia catappa pollen, 

two collections of Terminalia samoemis Rech., and one 

collection of Terminalia hayesii Pittier. Also considered 

were four species ol Combretum (listed p. 1172), Conocarpus erectus L., two species of Lumnitzera (listed 

p. 1172), Laguncularia racemosa (L.) Gaertn. f., BucJienavia capitata (Vahl.) Eichler, and Caliopteris floribunda Lambert.

Fossil occurrence.—In drill hole E-l at 2,450-2,460 

feet, three specimens, and at 850-880 feet, less than 7 

percent. In drill hole F-l, occurs in every sample between 670 and 860 feet, and represents as much as 5 

percent. Airai Clay (Miocene), Palau (USGS paleobotany loc. D1186), two specimens.

Present distribution.—The genus is pantropical; T. 

samoensis occurs on Eniwetok today, as well as on most 

of the Marshall Islands south of Eniwetok. T. catappa 

is planted on Likiep in the northern Marshalls (Fosberg, 1956, p. 288) ; elsewhere in Micronesia it growrs in 

the western and eastern Carolines and the Marianas 

where it may be indigenous (Kanehira, 1933). Degener 

and Gillaspy (1955), who observed T. catappa on Canton Island, stated that it is native to the Old World 

and is planted on Canton Island. Kanehira (1933) reported that it also grows in the Ryukyus and Bonins 

and on Formosa.

Ecology.—T. catappa is a large tree of the coastal 

forests (Kanehira, 1933). Taylor (1950, p. 192) reported that T. samoensis on Eniwetok and Bikini is 

"most characteristic of the area just behind the beach or 

shore rocks. * * * This species ordinarily occurs as 

scattered individuals and seldom dominates the vegetation, though it is common on the lagoon shore of * * * 

E1uo;e1ab Island."
1172 BIKINI AND NEARBY ATOLLS, MARSHALL ISLANDS

COMBRETUM L.

cf. Combretum

Plate 309, figures 6, 7

Pollen tricolporate, with three distinct pseudocolpi 

between the true apertures; spheroidal prolate to prolate; from about 19 by 22 to 19 by 25 /* in size. Colpi 

long, extending about two-thirds of distance from 

equator to pole. Only equatorial views available. Pores 

indistinct rounded or figure-8 shaped, usually transected or partly bisected by margo of colpus (pi. 309, figs. 

6,7).

Wall thickness probably greatest at costae on colpus 

margin (about 3 ft), and it is about 2 /* at other parts of 

grain. Wall thins at pseudocolpi and typically bends 

inward at these points, so that grains appear to have 

six colpi. Outer wall layer thinner than inner. Sculpture lacking, or granulate under oil.

Comparative material.— One collection each of Gombretum decandrum, G. farinosum H. B. & K., 0. tetralophum Clarke, and G. squamosum Roxb. were considered. The fossil grains are similar to G. tetraloplium and 

G. squamosum and resemble certain grains of Terminalia catappa.

Fossil occurrence.—In drill hole E-l at 850-860 feet, 

and F-l at 670-680 feet, less than 1 percent. Suva 

Series, Viti Levu, Fiji (Miocene sample; USGS paleobotany loc. D3277), two specimens. Talisay Member 

of Alifan Limestone (Miocene), Guam (USGS paleobotany loc. D1653), one specimen. Airai Clay (Miocene), Palau (USGS paleobotany loc. D1626), three 

specimens.

Present distribution.—The genus Combretum does 

not grow in the northern Marshalls, but it does occur 

in the western Carolines, Africa, Indo-Malaya, and 

Borneo.

Ecology.—C. tetraJophum is a woody vine, occurring 

in "wayside" thickets in coastal areas of the Palau Islands (Kanehira, 1933).

LUMNITZERA Willd. 

cf. L. littorea (Jack.) Voight. 

Plate 309, figures 22-26, 32-36

Tricolporate, with strongly developed pseudocolpi 

between apertures; spheroidal prolate to prolate; 29-32 

p in equatorial dimension and 30-31 /* in polar length. 

Colpal margins bend inward on most grains. Costal 

thickenings are present; these, in addition to inwardfolding margins of colpi, give grain the appearance 

of having very thick margos. Wall also bends inward 

at pseudocolpi, so that grain appears to have six colpi. 

Pore represented as a slit or break in costae under furrow. As seen from above, pore is slit along equator, as 

much as 8 /* long and 2 /*, wide (pi. 309, figs. 32, 33).

Sculpture lacking except in polar region, which has 

distinctive canallike grooves on surface. Grooves are 

dichotomizing (pi. 309, fig. 22) and threadlike and appear on several fossil grains.

Wall of two simple layers, outer layer thinner than 

inner. (See pi. 309, fig. 36.) Wall averages 3 /* in thickness and is 4 /* at costal thickenings.

Comparative material.—Pollens of both living species 

of Lumnitzera, including two collections of Lumnitzera 

racemosa Willd. and one of L. littorea, were examined. 

L. racemosa pollen is characterized by a reticulate 

sculpture (pi. 309, fig. 40), but sculpture is lacking or 

canaliculate in L. littorea. The pollen of this genus 

seems to be somewhat larger than that of the other 

CombretaJceous genera considered here (listed, p. 1171). 

In my estimation, the fossil Lumnitzera pollen in 

the Eniwetok material is identical with that of Lumnitzera littorea, and is unlike that of L. racemosa. Except 

for the Miocene age of the material, the fossils could 

probably be assigned to L. littorea.

Fossil occurrence.—In drill hole E-l at 2,480-2,490 

feet, one specimen, and at 850-880 feet, as much as 15 

percent of count. In drill hole F-l at 805-820 feet, less 

than 2 percent of count.

Present distribution.—One species in Micronesia, L. 

littorea, is also in Indo-Malaya, Australia, and the Pacific islands. Fosberg (1956) indicated that the genus 

is absent from the northern Marshalls. Anderson (1951) 

reported L. littorea on Arno Atoll. It is also on Jaluit 

and Ailinglaplap (F. R. Fosberg, written commun., 

1964).

Ecology.—On Arno Atoll, L. littorea occurs in saline 

swamps on the higher parts of the islands, where it is 

associated with Bruguiera and Sonneratia.

MYRTACEAE 

EUGENIA L.

cf. Eugenia 

Plate 310, figures 1, 2

Brevicolporate; only two specimens, both oriented in 

polar view; pores internal, colpi intruding, semiangular in shape; 15 /A in equatorial dimension; polar axis 

probably much shorter than 15 /*. Colpi very short, 

about 2 fi in total length and about 0.5 /* in greatest 

width. Brevicolpori subtended by pronounced local 

endexinous thickenings of about 1.5 /* that have flat 

surface on underside of colpus. Sculpture minutely 

rough under direct light and appears lacking under 

phase lighting. In interfurrow area, Avail thickness 1 ju. 

Two wall layers not distinct except under furrow, where 

inner layer thicker than outer.
MIOCENE POLLEN AND SPORE FLORA OF ENIWETOK ATOLL, MARSHALL ISLANDS 1173

Comparative material.—Pollen of the following1 

Myrtaceae forms was examined: three species of Eugenia, (E. capull (S. & C.) Berg1 ., E. lineata DC., and 

E. antiquae Riley), Eucalyptus incrassata Labill., E. 

globulus Labill., Decaspermum fruiticosum Forst., D. 

mymondii Diels, Myrtella benningseniana (Volkens) 

Diels, Rhodamnia trinervia (Sm.) BL, Psidium guajava 

L., and P. guineense Sw. Pike (1956) figured and described modern pollen of a large number of southwest 

Pacific Myrtaceae, including about 30 genera of the 

family. The fossil form certainly belongs to the family 

Myrtaceae for, like the pattern in that family, it has a 

breviaxial brevicolporate form, a subtriangular equatorial shape, and thickenings under the furrow. It is 

similar to pollen of the genera CJiamaelaucium and 

Rhodamnia. The fossils do not seem to belong to the 

Micronesian species of myrtaceous genera that one 

might expect here, such as Eugenia. Decaspermum, or 

Myrtella. As far as I know, pollen of these genera all 

typically have rather long colpi. I have not seen a 

wide selection of Eugenia species, and it is possible that 

the fossils belong to one of the many species of that 

genus now in the South Pacific. However, from what 

I have seen of this family, the fossils compare well with 

pollen of Rhodamnia, a Malaysian genus (pi. 310, fig. 

3).

Fossil occurrence.—In drill hole F-l at 830-840 feet, 

two specimens.

Present distribution.—Eugenia has a worldwide distribution in the temperate and subtropical zones; it has 

many endemic species in central and western Micronesia. Members of the family Myrtaceae are now absent 

from the Marshall Islands.

Ecology.—Eugenia species are known from both 

coral atoll and highland forest environments in the 

Carolines. On atolls, Eugenia grows in mixed forest on 

the higher parts of the islands (Fosberg, 1960, p. 19).

BORAGINACEAE 

TOURNEFORTIA L.

cf. T. argentea L. 

Plate 310, figures 4, ."

Tricolporate; prolate; 12-15 p in equatorial dimension, and 20-22 IJL in polar length. (Only specimens 

presenting equatorial views were identifiable.) Colpi 

extending about two-thirds of distance to pole, subtended by costae. Pseudocolpi occur between true colpi; 

both colpi and pseuclocolpi margins tend to fold 

inward toward cell lumen, so that this form is similar 

to the pollen forms in Combretaceae. Pore is not clearly 

defined and appears to be merely an interruption in 

colpus margin and costae. Pore is an area of thin wall 

about 2 {JL long in the plane of equator and 1 /A wide

in polar dimension. In profile, pore area is bulging; colpus margin bends at pore and follows straight line 

from pore to polar area.

Sculpture is lacking. Wall thickness about 1.3 /* in 

polar area 'and about 2 p under colpi. Outer wall layer 

seems thicker than inner.

Comparative material.—One collection of Tournefortia argentea was examined (pi. 310, figs. 6-9). Heliotropium pollen was considered because it has pseudocolpi. Combretaceae forms are similar, but none of the 

ones examined had such long axes and small size as T. 

argentea. This form may be hard to find in polar view, 

for its preferred orientation is equatorial because of its 

long prolate shape. In polar view, T. argentea closely resembles Combretum.

Fossil occurrence.—In drill hole E-l at 850-860 feet, 

less than 1 percent of count. In drill hole F-l at 820- 

840 feet, less than 1 percent.

Present distribution.—The species T. argentea is 

paleotropical and is widespread in Micronesia; it grows 

on Eniwetok today.

Ecology.—Anderson (1951) described T. argentea, on 

Arno Atoll as growing on drier lagoon shores with 

fSophora and Cordia. Fosberg (1960) stated that these 

three forms grow along the beach above high tide level. 

Pure stands of T. argentea are occasionally found (Fosberg, 1960, p. 19). T. argentea is generally found in all 

atoll environments except dense mature forests and is 

one of the commonest Micronesian plants (F. E. Fosberg, written commun., 1964).

BORAGINACEAE 

CORDIA L.

cf. C. subcordata Lam.

Tricolpate spheroidal (two specimens found, only 

polar view available) ; 44 ^ in equatorial diameter. Apertures are thin places in wall where ektexine absent; in 

single specimen found, apertures of ill-defined shape 

and size but seem to be restricted to equatorial area. 

Sculpture irregularly clavate, heads of some clavae joining to form vermiculate pattern. Endexine of uniform 

thickness (about 1 //,), and ektexine has an irregular 

thickness ranging from 1 to 2 p.

Comparative material.—Three collections of Cordia 

subcordata were each different from the other, and only 

Fosberg's collection 33784 from the Marshall Islands 

was similar to the fossil. Pollen of the Cordioidae do not 

seem to resemble pollen types in other sections 

of the family (Erdtnian, 1952, p. '78). Selling (1947) 

reported that C. subcordata has large grains (43 by 

40 /JL} with minutely reticulate sculpture; one of our C. 

subcordata- pollen preparations from Tonga resembles 

his description. Cordia is a large, complex, and variable
1174 BIKINI AND NEARBY ATOLLS, MARSHALL ISLANDS

genus that has not yet been thoroughly worked out taxonomically. Even so, it is surprising that in one species 

there is such diversity in pollen sculpture.

Fossil occurrence.—In drill hole F-l at 840-850 feet, 

one specimen, and at 810-820 feet, one specimen.

Present distribution.—O. subcordata is pantropical. 

In the Marshalls it is absent from the driest, most northern atolls but occurs on Eniwetok and those Marshall 

atolls farther south.

Ecology.—On atolls, O. subcordata occurs in brushy 

strips of mixed forest just inside the beach along with 

Tournefortia, Sophora, Pisonia, Terminalia samoensis, 

and Guettarda.

VERBENACEAE 

AVICENNIA L.

cf. A. marina Forsk. 

Plate 310, figure 10

Tricolpate; spheroidal; 27-28 /* in equatorial diameter (only polar view seen). Colpi long, extending 

three-fourths of distance from equator to pole. No pore 

visible.

Sculpture reticulate, with muri and lumina each 

about 0.7 (A wide. Inner wall of even thickness, 0.8 /*. 

Outer wall 1.2 /x thick in intercolpal area and thins 

abruptly at colpus margin; ektexine is composed of 

small clavae with heads joined in an open tectum.

Comparative material.—Comparative material includes Avicennia marina var. rumphiana (Hall f.) 

Balsh. (pi. 310, figs. 11,12), A. resinifera Forst. f., and 

A. nitida Jacq. A. nitida has pollen that is very similar 

to the fossil, but wall-thinning at the edge of the colpus 

is not as pronounced as in A. marina. A. resinifera has 

a coarser reticulum than the fossil. Several other genera O

of Verbenaceae were examined, but none compared 

well with the fossil.

Fossil occurrence.—In drill hole E-l at 2,440-2,450 

feet, one specimen, and at 870-880 feet, 5.5 percent. In 

drill hole F-l at 830-860 feet, less than 2 percent, and 

at 670-820 feet, less than 2 percent. Airai Clay (Miocene), Palau (USGS paleobotany loc. D1626), about 

10 specimens. Upper Miocene and younger beds of Borneo (Muller, 1964).

Present distribution.—A. marina occurs in India, Malaya, south China, and in the Pacific islands eastward 

as far as the Mariana Islands.

Ecology.—A. marina is a mangrove forest tree; in the 

Palaus it is rare but is more common farther west.

RUBIACEAE 

IXORA I.

cf. I. casei Hance 

Plate 310, figures 13-15

Tricolporate; all three Eniwetok specimens found 

present polar views. One specimen (pi. 310, figs. 13- 

15) is 25 [A in greatest equatorial dimension; other two 

measure only 18-19 /*, but three are identical in all other 

respects. Spheroidal shape, pore margins protruding 

slightly. Colpi very long, extending seven-eights of 

distance to pole. Colpi gape but are subtended with 

thin membrane of endexine; colpal margins very distinct but not thickened externally. Colpal margins have 

small endexinous thickenings where they intersect pore, 

and at these points wall protrudes slightly. Pores 1.5 ft 

wide along equatorial axis and probably round. (See 

pore at upper left corner of pi. 310, figs. 13-15.)

Sculpture finely reticulate and centers of lumina 

about 0.75 /x apart. Polar areas of one specimen marked 

by two small veinlike canals as viewed under phase 

lighting. Wall 1.5 p thick in midintercolpal area and 

thins slightly toward furrow and then thickens at pore 

margin to 1.5 p. Wall is two layered, endexine somewhat 

thicker than ektexine in intercolpal area.

Comparative material.—The comparative materials 

used were Ixora casei, three collections, and /. volkensii 

Hosakawa ( = /. casei). Pollen of some 24 Rubiaceae 

genera of Old World and Micronesian distribution 

were examined. Of these, only the Malayan, Melanesian, 

and Micronesian genus Gynochthodes has the same general pollen morphology as Ixora, but its pollen is larger 

and has coarser reticulation. Among the three collections of modern Ixora casei pollen, one was large, 22- 

28 /A in equatorial diameter, and two were smaller, 18-28 

/x. The three fossil Ixora pollen grains fall within that 

size range and are referred to cf. /. casei.

Fossil occurrence.—In drill hole F-l at 820-840 feet, 

three specimens. At Guam (USGS paleobotany loc. 

D1652) in the Talisay Member of the Alifan Limestone 

of Miocene age, one specimen.

Present distribution.—Ixora has three endemic species in Micronesia. Ixora sp. (probably /. casei, according to F. R. Fosberg, written commun., 1964) was reported from Arno Atoll by Anderson (1951), but is 

not known in the northern Marshalls.

Ecology.—Ixora is a shrub in the coastal forests of 

the Palaus (Kanehira, 1933; F. R. Fosberg, written 

commun., 1964).
MIOCENE POLLEN AND SPORE FLORA OF ENIWETOK ATOLL, MARSHALL ISLANDS 1175

GARDENIA Ellis 

cf. 6. grievei Home

Plate 310, figures 16, IT

Pollen in tetrads; each cell triporate. Single tetrad 

found is torn and flattened, 35 by 54 /A in size. Individual 

cells 25 by 30, 20 by 31, 30 by 32, and 30 by 30 p in equatorial diameter. Polar axes cannot be measured, but 

cells seem to be oblate and short axial. Pores are round, 

as much as 3 /A in size. Endexine thickening immediately 

under pore rim makes total wall thickness from 3 to 

3.5 /A at that point; wall at interpore area only 0.8-1 /A 

thick. Ektexine thicker than endexine. As seen from 

above, pore rim thickening is 1.5 /A wide. Scabrate 

sculpture.

Comparative material.—Of the entire Micronesian 

modern pollen collection prepared for this study, only 

seven genera have pollen in tetrads: Gardenia, Hydrostachys, Alocasia, CyatJiodes (equals /Styphelia), Codiaeum, Nepenthes, and Drosera. Of these, only Gardenia 

resembles the fossil. Of the monad forms with triporate 

pollen of rough sculpture and thickened pores, only 

Guettarda speciosa L. is much like the individual cells 

of the fossil tetrad, but not only is its pollen about twice 

as large as that of Gardenia grievei, its sculpture is very 

rough, or gemmate. No tetrads were present in the 

modern Guettarda speciosa collections I examined.

Gardenia grievei pollen is very similar in size, sculpture, and aperture morphology to the fossil. There is 

little question in my mind that the fossil represents 

pollen of that genus.

Fossil occurrence.—In drill hole F-1 at 820-830 feet, 

one specimen.

Present distribution.—Gardenia is not known from 

Micronesia. Seven species of Gardenia were reported 

from Borneo by Merrill (1929). Takeda (1957) reported 

one species from the Ryukyu Islands. The genus has 

about 80 paleotropical species, ranging from Africa, 

Indo-Malaya, and Thailand to the Philippines, Fiji, 

and Tahiti; several endemic species occur in the 

Hawaiian Islands.

Ecology.—Gardenia is either a tree or a shrub; most 

species are upland forest forms and are not found growing close to sea level in halophytic environments.

MORINDA I. 

of. M. citrifolia L.

Plate 311, figures 1, 2, 9, 10

Pollen tricolporate and 35-39 /A in equatorial diameter. 

Equatorial views not found, but grain appears oblate, 

short axial. Colpi extend two-thirds of distance to 

pole. Colpi margins distinct, unornamented, and gape 

(from 1 to 3 /x) at pore to reveal a wedge-shaped membrane of endexine. Pore margins thickened on underside

by endexine where intersected by colpi margins. 

Ektexine thins slightly at pore margin and arches upward over endexine thickening, so that pore edge protrudes. From polar view, pore appears circular and is 

of same width as colpi at equator. Endexine 0.8 /A thick; 

ektexine 1.2 /A thick, composed of clavae with partly 

fused heads. Sculpture an even reticulum with lumina 

about 1 fi in diameter and muri about 0.3 /A in width.

Comparative material.—Comparative material includes Morinda umbellata L. and three collections of 

M. citrifolia. Certain other Eubiaceae genera have pollen of this general form but of vastly different sizes. 

(See /Scyphiphora. pi. 311, figs. 15, 16; Mussaenda, pi. 

311, figs. 7,8.)

Fossil occurrence.—In drill hole E-l at 2,450-2,470 

feet, four specimens, and at 850-880 feet, less than 2 percent. In drill hole F-1 at 830-850 feet and 810-820 feet, 

less than 1 percent. Suva Series, Viti Levu, Fiji (Miocene sample; USGS paleobotany loc. D1417), two 

specimens.

Present distribution.—Morinda citrifolia occurs from 

India to Polynesia; it is present on Eniwetok and all 

the larger northern Marshall Islands, but Fosberg 

(1956, p,, 285) thought that it was introduced by man in 

this area.

Ecology.—Fosberg described M. citrifolia as growing 

either on atolls inland from the beach line with Tournefortia, Oordia, Pisonia, and Pandanus or along passages 

between islets, usually in shade.

Of the fruit of this species, Kanehira (1933, p. 365) 

said: "Fruit a multiple drupe about the size of a hen's 

egg, (seeds) hollow inside, buoyant, retaining germinating power for a long time, and can therefore be distributed by ocean currents." Because the root of this 

species is used by natives as a dye for loincloths (Kanehira, 1933, p. 365), its present distribution might have 

been aided by man.

GUETTARDA I.

of. Guettarda 

Plate .310, figures 29, 30

Pollen triaperturate, probably porate. Equatorial 

outline circular, and cell probably oblate. Equatorial 

diameter from 28 to 30 /A. Apertures are represented 

only by parting of ektexine; nature of aperture in many 

specimens obscured by sculpture elements. The aperture areas free of ektexine for equatorial distance of 1-2 

/A and appear isodiametric. Sculpture uniformly and 

coarsely reticulate. Ektexine composed of clavae 2 /A in 

length, their heads partly joined in an open tectum. 

Endexine barely visible through ektexine but seems to 

be about 1 /A thick and without accessory thickenings.
1176 BIKINI AND NEARBY ATOLLS, MARSHALL ISLANDS,

Comparative material.—Comparative material includes Guettarda odorata Lam. (pi. 310, figs. 35, 36), G. 

macrosperma J. D. Smith (pi. 310, figs. 37,38), and two 

collections of G. speciosa L. Pollen of G. macrosperma 

has a reticulum similar to that of the fossil form, but its 

pore has wall thickenings that are not evident in the fossil. G. odorata has a wall structure like that of the fossil 

form but is slightly larger in size; the fossil cannot be 

assigned to this genus with certainty because the morphology of Guettarda pollen intergrades with that of 

Timonius. The fossils are definitely not comparable to 

G. speciosa pollen because that species has scabrate triporate pollen.

Fossil occurrence.—In drill hole E-l at 2,450-2,460 

feet, two specimens. In drill hole F-l at 820-840 feet, 

less than 1 percent.

Present distribution.—The species which compare 

favorably with the fossil material (G. macrosperma of 

Costa Rica, G. odorata of Panama) are not represented 

in Micronesia today. The Micronesian strand species, 

Guettarda speciosa, is not similar to the fossil.

Ecology.—G. macrosperma and G. odorata are upland forest forms.

TIMONIUS Rumph.

cf. Timonius 

Plate 310, figures 21-23

Pollen triaperturate, probably porate; equatorial 

outline circular. Cell short axial, probably oblate. Equatorial diameter ranges from 27 to 30 p. Apertures represented only by a parting of ektexine; nature of apertures hidden by thick ektexine reticulum near them. 

Aperture areas seem free of ektexine for an equatorial 

distance of only 2 /* and appear isodiametric. Sculpture 

medium to coarsely reticulate. Ektexine composed of 

clavae from 1.5 to 2 /* in length, with heads joined in 

an open tectum and in a reticulate pattern that grades 

toward a finer pattern at the poles (pi. 310, figs. 21, 22). 

Endexine, barely visible through the ektexine, appears 

to have a uniform thickness of about 1 /*.

Comparative material.—Comparative material includes Timonius corymbosus Val. and Timonms affinis 

A. Gray. The pollens of 24 Rubiace;ae genera were considered in the course of this study, and of these only 

Guettarda, and Timonius were similar to the fossils. The 

New World species Guettarda odorata (pi. 310, figs. 35, 

36) and G. macrosperma Donnell Smith (pi. 310, figs. 

37, 38) have pollen rather similar to that of the fossil 

but are distinguished by their coarser reticulate sculpture. Timonius corymbosus pollen is rather like that of 

G. macrosperma, but T. affinis pollen (pi. 310, figs. 26- 

28) is very close indeed to the fossil form.

Fossil occurrence.—In drill hole E-l at 2,450-2,470

feet, 14 specimens, and at 880-890 feet, one specimen. 

In drill hole F-l at 830-840 feet, less than 1 percent. 

Airai Clay (Miocene), Palau (USGS paleobot'any loc. 

D1186), one specimen. Suva Series (Miocene), Viti 

Levu, Fiji (USGS paleobotany loc. D3277), one 

specimen.

Present distribution.—The genus is of Indo-Malayan 

distribution; it also occurs in Melanesia and Polynesia, 

and in Micronesia eastward as far as the eastern Carolines. T. affinis, which the fossils especially resemble, occurs on Fiji. The genus shows a high degree of endemism in the Palau Islands, where it has eight species.

Ecology.—Of the eight species in the Palaus, all are 

shrubs, and only one is definitely known to grow on 

coral soil; seven are forest forms.

RANDIA Houst. ex. L.

cf. R. cochinchinensis (Lour.) Merr.

Plate 310, figures 31, 32

Pollen 4-pored; oblate; single specimen is 22 by 25 /* 

in size. Pores distributed randomly on cell; pores 4.5 /* 

in diameter, round; borders thickened only on underside by wedge-shaped endexinous thickening. As seen 

from above, pore margins very distinct. Sculpture 

microreticulate, with centers of lumina only 0.8 /* apart. 

Ektexine composed of small clavae 0.8-1 p. in length, 

with heads fused in an open tectum. Endexine about 

0.8 n thick except under pores, where 1-1.5 /x thick.

Comparative material.—Comparative material includes Randia cochinchinensis, three collections, and 

Randia caroUnensis Val. Four-pored pollen is apparently uncommon, not only in the family Rubiaceae, but in 

the genus Randia. Erdtman (1952, p. 386) indicated 

that among 120 Rubiaceae genera, none typically are 

four or five pored. In discussing pollens of about 12 

species of Randia he said that these are triporate, polycolpate, or polycolporate. However, in the three collections of R. cochinchinensis pollen I noted that although 

the pollen is predominantly three pored, a few fourpored pollens occur in each. The similarity of the fossil 

pollen morphology to that of Randia cochinchinensis is 

unmistakable, though there is a slight difference in size; 

R. cochinfhinemis is 18-22 p. in greatest diameter, and 

the fossil is 25 /*. A second specimen may be assignable 

to Randia, but it seems to have small colpi passing 

through the pores. The second is figured on plate 311, 

figure 20.

Fossil occurrence.—In drill hole E-l at 850-860 feet, 

one specimen.

Present distribution.— Randia- has a pantropical distribution. Two species are recorded in Micronesia, R. 

cochinchinensis from the western Carolines, Marianas, 

and southern Marshalls (Arno Atoll), and R. carolinen- 

•sv',« from the Carolines.
MIOCENE POLLEN AND SPORE FLORA OF ENIWETOK ATOLL, MARSHALL ISLANDS 1177

Ecology.—R. cocliinchinensis is a small tree abundant 

in the coastal forests, on the plains, and in the foothills 

of every island in western Micronesia (Kanehira, 

1933) ; it grows in forests on Arno Atoll, according to 

F. R. Fosberg (written commun., 1961).

SCYPHIPHORA Gaertn. f.

cf. Scyphiphora 

Plate 311, figures 13, 14

Tricolporate; 25-26 //, in equatorial dimension; four 

specimens seen; apparently breviaxial. Colpi extending three-fourths of distance to poles. Pores indicated 

by costal thickenings at equator but not seen clearly 

in this specimen. Wall protruding slightly at pore rims. 

Sculpture uniformly reticulate, with centers of lumina 

1 p apart. Wall 1.7 ju, thick at intercolpus areas and 2.5 

p. thick at pore rim. Ektexine thicker than endexine and 

composed of small bacculae elements with heads fused 

into an open reticulum.

Comparative material.—One collection of /Scyphiphora hydrophyllacea Gaertn.

Fossil occurrence.—In drill hole F-l at 830-840 feet, 

one specimen. In drill hole E-l at 2,440-2,470 feet, four 

specimens.

Present distribution.—/Scyphiphora liydropliyllacca 

is paleotropical and occurs as far east in Micronesia as 

Yap in the western Carolines. It seems to be absent from 

Ponape (Glassman, 1957) and from the Marshalls.

Ecology.—A small tree or shrub and mangrove 

swamp associate.

DICOTYLEDONOS POLLEN OF UNCERTAIN FAMILY AFFINITY

7MORACEAE 

MALAISIA Blanco

Malaisia type 

Plate 311, figure 18

Diporate; 16 by 13 p in size; oblate. Pores round, 

about 1.5 [j. in diameter, spaced opposite each other. 

Sculpture lacking or very slightly granulate. Wall simple, two layered, about 0.7 //, thick.

Comparative material.—One collection of Malaysia 

tortuosa Blanco has pollen that is nearly identical with 

this fossil, but Morus and Trema (Ulmaceae) have pollen that is closely similar. Lacking more comparative 

material, I feel that neither the family nor the genus 

can be ascertained at this time.

Fossil occuwence.—Code species P2-sm(l) ; in drill 

hole E-l at 2,440-2,450 feet, three specimens.

Present distribution.—Malaisia scandem is paleotropical; M. tortuosa occurs on New Caledonia.

Ecology.—M. scandens is a woody creeper occurring 

at the foolt of mountains and at the edge of forests and 

clearings on Saipan (Kanehira, 1933).

?LE6UMINOSEAE 

SOFHORA L.

Sophora type 

Plate 306, figures 6-8

Tricolporate; single specimen found measures 12 //, 

in equatorial diameter and about 11 //, in polar dimension. Spheroidal or oblate spheroidal. Colpi long, extending almost to pole, with narrow margos, 0.5 //, wide. 

Pores circular, 4 //, in diameter. Sculpture finely reticulate, with lumina and muri each about 0.5 //, in width.

Comparative material.—The fossil grain was compared with Sophora tomentosa L. and Sophora secundiflora Lag. Mature pollen of S. tomentosa (pi. 306, figs. 

14-16) is similar to the fossil because of its large pore 

(6 by 7 /A), overall similarity in length of colpi, small 

margos, size of grain, and micro reticulate sculpture; 

however, the outline of the grain in polar view is not 

similar to that of the fossil. S. tomentosa has a somewhat triangular rounded shape in polar view, whereas 

the fossil is rounded but somewhat folded inward at 

the pore in a pattern termed "fossaperturate" by Erdtman (1952, p. 13).

Fossil occurrence.—Code species C3Pri-r(ll) ; at 870- 

880 feet in drill hole E-l, one specimen.

Present distribution.—Genus presently occurs in 

Japan, Polynesia, Melanesia, and east to eastern Caroline Islands; Sophora tomentosa occurs at Arno, Ujelang, Ujae, and Likiep Atolls in the Marshall Islands 

but is not known on Eniwetok. It is a pantropical strand 

plant.

Ecology.—S. tomentosa grows along lagoon sides of 

islets just in back of beaches (Fosberg, 1955a, p. 12). 

On Arno Atoll, Anderson (1951) observed the species 

on the drier lagoon shores in association with Scae v.o7a. 

Suriana. Pern-phis, Tournefortia. and Cordia.

?SIMARUBACEAE 

BRUCEA J. S. Miller

Brucea type 

Plate 311, figure 31

Tricolporate; prolate in equatorial view. Single 

specimen 26 by 30 //, in size. Colpi extending threefourths of distance to poles. Colpus margins folding 

inward, forming what appear to be narrow margos. 

Pores internal, 3-4 //, along equatorial plane and 1-3 

p along polar axis, size depending on state of contraction of the furrow. Sculpture finely striate; sculptural 

elements consist of clavae or baculae in optical section. 

Ektexine about 1.5 ^ thick; endexine 0.5 ^ thick.

Comparative material.—The single specimen \vas 

compared with pollen of the same general structure in 

the Anacardiaceae, Rutaceae, Rosaceae, and Simaruba-
1178 BIKINI AND NEARBY ATOLLS, MARSHALL ISLANDS,

ceae. Though comparative material for Brucea was not 

available for this study, the fossil seems to closely 

resemble that genus as described and figured by Erdtman (1952, p. 407). The family assignment to Simarubaceae must be considered tentative.

Fossil occurrence.—Code species C3P3-st(l) ; single 

specimen in drill hole F-l at 850-860 feet.

Present distribution.—The genus has one species in 

Micronesia, B. Javanica (L.) Merr. (Kanehira, 1933), 

which also occurs in India, Australia, and Malaya, and 

it is planted on Ponape.

Ecology.—Unknown to me.

TSIMARUBACEAE 

PICRODENPRON Planch.

Picrodendron type 

Plate 311, figure 19

Pollen with four apertures, stephanoporate. Only 

specimen is 35 by 33 ^ in equatorial view; even though 

specimen is split, its shape is clearly oblate spheroidal. 

Apertures oval to circular, range from 2 to 2.5 //, in diameter, and have a rough outline. Pores are subtended by 

thickenings, presumably of the endexine, although no 

aperture can be seen in optical section. Sculpture is 

echinate, and conical spines are about 0.5 p across at base 

and about as wide as long. The two layers of cell wall 

are of about equal thickness, and the total Avail is 1 p 

thick in interpore area. The wall is about 1.5 ^ thick at 

the pore margin, as shown at extreme right on plate 311, 

figure 19. Wall sculpture between spines seems lacking, 

but because this specimen is mounted in polyvinyl alcohol, visibility is not good even under oil immersion 

lens or phase lighting.

Comparative material.—This fossil was compared 

with groups which are characteristically three to five 

stephanoporate or brevicolporate, including Campanulaceae (Section Campanuloideae), and Curcurbiitaceae. 

The characteristics of the fossil seem best matched by 

the pollen of a morphologically isolated'genus of the 

Simarubaceae, Picrodendron. Pollen of P. baccatum 

(L.) Krug & Urban is nearly identical with the fossil 

form except that it has a greater wall thickness. However, because neither this genus nor closely related forms 

are now known from the Micronesian area and because 

critical comparison of the pore structures is not possible 

here, the identification even to family must be considered 

tentative. More modern collections in the family Simarubaceae should be studied to assure the assignment suggested here, but of the 24 genera of Simarubaceae whose 

pollen was described by Erdtman (1952) none except 

Picrodendron has pollen of this fossil type.

Fossil occurrence.—Code species P4-p(l) ; in drill 

hole F-l at 820-830 feet, one specimen.

Present distribution.—Picrodendron is a genus of the 

West Indies.

?CALIITRICHACEAE 

CALLITRICHE L.

Callitriche type 

Plate 311. figure 24

Pollen tricolpate or quadricolpate; when tricolpate, 

shape is circular, and when quadricolpate, rectangular; 

in both, colpi are open. Equatorial views are not available in fossil material. Colpi extend halfway from 

equator to poles and have a vague outline. The sculpture 

under high dry lens appears merely scab rate, but under 

oil immersion lens it is very clearly reticulate. The sculpture is coarser on the poles, and there the lumina are 

about 1 fj. wide and about 1 //, apart. The cell wall is composed of two distinct layers of equal thickness, the outer 

wall being composed of the fused verrucate elements 

of the reticulum. The endexine and ektexine extend to 

the furrow edge together and without thickening. The 

wall is about 0.8 /* thick.

Comparative material.—C. christensenii Christoph. 

was used for comparison; the fossils match well with 

Callitnche pollen described and figured by several 

authors (Moar, 1960; Hafsten, 1960).

Fossil occurrence.—Code species C4-r(l). In drill 

hole E-l at 2,450-2,470 feet two specimens. In drill hole 

F-l, at 670-680 feet, one specimen.

Present distribution.—The genus is cosmopolitan except for Pacific islands. No records are known for Callitriche in Micronesia. One species, C. papuana Merrill 

and Perry (1941), is recorded from New Guinea.

Ecology.—Gallitriche is a delicate plant whose stems 

usually are supported by water but sometimes are prostrate on mud or on moist soil. Many species are freshwater forms, as is C. papuana, of New Guinea. C. muelleri Sond. has been collected from numerous harbors and 

reef islands between lats 17° and 41° S. by Mason 

(1959) ; precise local ecology was not documented by 

Mason, but the occurrence of this species on Great Barrier Island suggests a somewhat brackish soil environment.

THIPPOCRATEACEAE 

SALACIA L.

Salacia type 

Plate 306, figures 12, 13

Tricolporate; single specimen found is 18 by 19.5 p. 

in polar view. Circular to somewhat intersubangular in 

polar view with colpi intruding. No equatorial view 

available. Colpi and narrow marges extend threefourths of distance to poles. In polar view, specimen has 

narrow pores only 1 ^ wide. Wall 2.5-3 //, thick at equator
MIOCENE POLLEN AND SPORE FLORA OF ENIWETOK ATOLL, MARSHALL ISLANDS 1179

in intercolpal area, both component layers thinning toward colpi. Wall protrudes slightly at furrow edge 

and then ektexine bends inward at furrow lip. Endexine 

appears to thicken immediately under colpus margins 

and may either form internal costae or represent an endexinous membrance subtending colpus itself. (See 

lowermost colpus, pi. 306, fig. 13). Sculpture microreticulate with lumina about 1 ^ apart.

Comparative material.—This specimen was compared 

with modern pollen of Solatia printides DC. (pi. 306, 

figs. 20, 21) and (Hippocratea macrantha Koeth. The 

detailed pollen descriptions of 14 genera and 46 species 

of Hippocrateaceae by Van Campo and Halle (1959) 

provided information on the range of pollen morphology in this family. Their work makes it clear that the 

nature of the structure under the furrow is a critical 

feature in assigning pollen to the Hippocrateaceae, 

though Erdtman (1952, p. 205) did not mention nor 

figure it in Solatia. Because the exact nature of that 

structure is not clear in my fossil specimen, a definite 

assignment cannot be made. A species of /Solatia that 

appears to have a pollen morphology closely resembling that of the fossil specimen, but of which comparative material was not available for this study, is 8. 

zenkeri Loesener. Van Campo and Halle (1959, description for their pi. 46) indicated that the equatorial 

size of /$. zenkeri is 19-20 ^ and that it is finely reticulate. Pollen of that species seems to resemble closely 

the fossil described here, but because of its present 

African distribution it seems unlikely that S. zenkeri is 

related to this Pacific fossil.

Fossil occuwence.—Code species C3P3-r(9) ; in drill 

hole F-l at 830-840 feet, one specimen.

Present distribution and ecology.—Salada has one 

known species in Micronesia, S. naunwnnii Engl., which 

is a small twinning shrub of low-elevation thickets in 

New Guinea and in the western Carolines (Kanehira, 

1933, p. 196). Merrill (1929) described Solatia korthalsiana Mig. as a liana in dense forests in Java.

?ELAEOCARPACEAE 

ELAEO CARPUS Burm. ex. L.

Elaeocarpus type 

Plate 311, figures 25-27

Tricolporate; oblate; 9-11 /j. in equatorial dimension. 

Colpi gaping and protruding at equator and extending 

two-thirds of distance to poles. Pores evident as pouting areas at equator, where colpus margins bend so as 

to appear angular in equatorial view. Pores 1 ^ in dimension. Sculpture lacking, and wall two layered, about 

0.8 p thick.

Comparative material.—Comparative material includes Elaeocarpus carolinensis Koidz., E. graeffei

Seem., E. joga Merrill, and E. polystachyus Wall. Pollen of these species are difficult to distinguish, and the 

fossil form is very similar to pollen of all these taxa. 

Small tricolporate smooth pollen of this very ordinary 

pattern is found in Gynotroches (Rhizophoraceae), Tarenna (Rubiaceae), and in other unrelated genera; hence, 

a family and genus assignment cannot be made with 

certainty.,

Fossil occurrence.—C3P3-sm(10), polar view; C3P3- 

sm(8), equatorial view; in drill hole F-l at 840-860 

feet, less than 3 percent of total pollen and spores, at 

820-840 feet, common to dominant, 40-80 percent of 

total pollen and spores, and at 810-820 feet, less than 1 

percent.

Present distribution.—Elaeocarpus is pantropical and 

has six species in the western Carolines. It is not now 

found in easternmost Micronesia but has one species in 

the Marianas and several on Ponape.

Ecology.—Elaeocarpm is one of the largest trees on 

Ponape and grows scattered in forests at low elevation, 

according to Kanehira (1933).

?BHIZOFHOBACEAE 

GYNOTROCHES Blume

Gynotroches type 

Plate 308, figures 44, 45

Tricolporate; prolate; 12.5 by 8.5 ^ in size. Colpi 

extending about two-thirds of distance from equator 

to pole. Polar view (pi. 5, fig. 45) shows that oolpi 

margins are rolled inward toward the cell lumen and 

appear as internal thickenings. Pores are areas of thin 

endexine elongated along equatorial plane or of poorly 

defined equatorial extent and are about 2 ^ wide along 

polar axis. Inrolled colpus margin (or possibly internal costae under colpus) attenuated greatly at equator 

in pore area. Sculpture lacking, and wall about 1 ^ thick 

in noncolpus areas. Wall simple, of two equally thick 

structureless layers.

Comparative material.—The comparative material is 

one collection of Gynotroches axillaris Bl. pollen (pi. 

308, figs. 53-55). The fossil pollen is slightly larger than 

Gynotroches pollen, and though the gross morphology 

of the fossil is of a somewhat generalized tricolporate 

type so as to make certain identification difficult, the 

fossil bears a striking resemblance to pollen of 

Gynotroches.

Fossil occurrence—Code species C3P3-sm(7) ; in drill 

hole E-l at 850-880 feet, less than 3 percent, In drill hole 

F-l at 6TO-850 feet, as much as 15 percent.

Present distribution—One species, Gynotroches axillaris. occurs in Micronesia (Kanehira, 1933). It is IndoMalayan, Polynesian, Melaiiesian, and Philippine in
1180 BIKINI AND NEARBY ATOLLS, MARSHALL ISLANDS

distribution and occurs in the eastern Carolines on 

Ponape.

Ecology.—Gynotrochcs axillaris occurs in forest 

stands, both lowland and highland, on Ponape and is 

a medium-sized tree.

?VERBENACEAE 

CALLICARPA I.

Callicarpa type 

Plate 311, figures 22, 23

Tricolpate; oblate; 21 ;u, in equatorial dimension. 

Colpi reaching two-thirds of distance to poles. Colpus 

margins have no accessory •thickenings, and no evidence 

of pores. Colpi gaping at equator; endexinous membranes extend from ektexine to form membranous colpus margins. Sculpture microreticulate, with himina 

centers about 1 ;u, apart. Wall 1.5-2 p. thick, with ektexine 

thicker than endexine. Reticulum composed of bacculae with heads fused.

Comparative material.—Comparative material includes Callicarpa acuminata H.B.K., and C. cana, L. 

The fossils are very similar to the pollen of C. acumiiuita. More modern comparative collections from Pacific 

species must be seen, however, before a generic determination can be made.

Fossil occurrence.—Code species C3-r(l) ; in drill 

hole E-l at 2,440-2,450 feet, one specimen, and at 870- 

880 feet, six specimens. In drill hole F-l, at 810-820 

feet, one specimen, and at 670-680 feet, one specimen.

Present distribution.—Callicarpa is pantropical; in 

Micronesia, Kanehira (1933) recorded one species of 

Malayan Archipelago distribution and two endemic to 

the western Carolines.

Ecology.—Kanehira ?s species are shrubs in mixed and 

open forest.

?GESNERIACEAE 

CYRTANDRA Forst.

Cyrtandra type 

Plate 311, figure 21

Tricolpate; subp relate; 23 by 31 p in size. Colpi almost 

reaching poles; margins turning inward toward cell 

lumen. Specimens are compressed, showing infolding on 

two lateral colpi. No clear evidence of pores, which are 

vaguely defined in Cyrtandra pollen. Wall 1.5 ;u, thick, 

and made up of two layers of equal .thickness. Sculpture 

lacking or minutely granulate.

Comparative material.—One collection of Cyrtandra 

urvillei C. B. Clarke, which has pollen much smaller 

(12 by 18 ju,) than the fossil type, was used for comparison. Selling (1947, pi. 40) figured pollen of Gyrtandra 

lysiosepala (A. Gray) C. B. Clarke, which is very similar in morphology to the fossils and almost as large; 

his material averages 26 by 20 //, in size, is up to 29 ;u, long. 

There is, I think, a fair indication that this fossil belongs to the genus Cyrtandra, but more modern comparative material would be needed to be certain.

Fossil occurrence.—Code species C3-sm(3); in drill 

hole E-l at 2,450-2,470 feet, six specimens.

Present distribution.—Cyrtandra is a paleotropical 

genus with a high degree of endemism (250 species of 

this genus are known). Kanehira (1933) recorded 

four endemic species for the Palau Islands; there are 

also one or two on Kusaie.

Ecology.—Cyrtandra species are shrubs or vines in 

the Palaus. All four species mentioned by Kanehira are 

highland wet forest forms, but at least one grows on 

limestone (F. K. Fosberg, written commun., 1964).

?RTTBIACEAE 

COPROSMA Forst.

Coprosma type 

Plate 311, figure 37

Pentacolporate; spherical; 32 ^ in equatorial diameter; single specimen seen. Colpi reaching halfway to 

pole, and gaping at equator; margins simple and unadorned. Pores 5 by 7 ^ in size, with long axis along 

equator; poleward margins thickened slightly by endexine. Sculpture lacking or minutely granulate. Wall 

two layered and about 1 ^ thick.

Comparative material.—This fossil was compared 

with Sapotaceae genera that have four- to six-colporate 

pollen; the fossil is unlike members of that family because of its spheroidal shape, thin wall, gaping furrows, and lack of costae or margos. The fossil resembles 

Selling's (1947, pi. 48, especially figs. 758, 762) figured 

pollen of Coprosma of the Rubiaceae. Modern pollen of 

C. ernodeoides A. Gray and a collection of Coprosma sp. 

from New Guinea were on hand for direct comparison. 

Coprosma pollen is typically -tricolporate, whereas pollen of C. ernodeoides A. Gray is either tricolporate or 

tetracolporate; other species are occasionally tetracolporate, according to Selling (1947, p. 315). Apparently 

the polycolporate condition is a tendency in pollen of 

this genus. The great similarity in shape, size, wall 

thickness, and aperture structure between the fossil and 

Selling's Coprosma and my own Coprosma sp. material 

indicates that the fossil may belong to this or a closely 

related genus.

Fossil occurrence.—Code species C5P5-r(l) ; in drill 

hole E-l at depths 2,450-2,470 feet, five specimens. 

Cranwell (1962, 1964) reported Neogene(?) pollen of 

this genus from Rapa, Austral Islands.

Present distribution.—Coprosma is an Antarctic and 

Austral-Pacific genus, not now known in Micronesia 

(Croizat, 1952, p. p. 101).

Ecology.—The habit is shrubby; the habitat is not 

known to me.
MIOCENE POLLEN AND SPORE FLORA OF ENIWETOK ATOLL, MARSHALL ISLANDS 1181

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resources of Babelthuap Island (Palau main island) : 

Tropical Industry Inst. Bull. 3, p. 1-19.

————1952, Coral reefs in the South Seas: Japan Hydrog. Office 

Bull., v. 11. 292 p.

Taylor, W. R., 1950, Plants of Bikini and other northern Marshall Islands : Michigan Univ. Press, 227 p.

Todd, Ruth, and Low, Doris, 1960, Smaller Foraminifera from 

Eniwetok drill holes: U.S. Geol. Survey Prof. Paper 260-X. 

p. 799-861.

Tracey, J. I., Jr.. Ladd. H. S., and Hoffmeister. J. E., 1948, Reefs 

of Bikini, Marshall Islands: Geol. Soc. America Bull., v. 59, 

no. 9, p. 861-878.

Tracey, J. I., Jr., Schlanger, S. O., Stark. J. T.. Doan, D. B., and 

May, H. G., 1964. General geology of Guam: U.S. Geol. Survey Prof. Paper 403-A, 104 p.

Tschudy, R. H., 1957, Pollen and spore formulae—a suggestion: 

Micropaleontology, v. 3, no. 3, p. 277-280.

Van Campo, Madeleine, and Halle. Nicolas, 1959, Les pollens 

des Hippocrateacees d'Afrique de L'Ouest: Pollen et Spores, 

v. 1, no. 2, p. 191-272, 50 pis.

Wiens, H. J., 1962, Atoll environment and ecology: Yale Univ. 

Press, 532 p.

Wolfe, J. A., and Barghoorn, E. S., 1960, Generic change in 

Tertiary floras in relation to age (Bradley volume) : Am. 

Jour. Sci. v. 258-A, p. 388-^399.
INDEX

Abronia.. ..................................... 1163

Acalypha.... 1146,1147,1150,1152,1163,1167; pi. 306

alopecuroides.. ........................... 1167

ediforniea................................ 1167

catarus................................... 1167

godseffiani................................ 1167

grandis................................... 1167

hitpida................................... 1167

indka.... ................................. 1167

leptopoda................................. 1167

lindheimeri.......... ..................... 1167

wSfeeswmi. _.__....................._... 1167

sp........ 1147, 1151, 1152, 1160, 1167; pi. 306

Achyranthes aspera............................ 1143

velutina.......... ..................... 1143,1151

acidula, Pemphis........................ 1143,1151

Acknowledgments.................._....... 1135

acuminata, Callicarpa.......... ............... 1180

aegyptium, Dactyloctenium.................... 1143

affinis, Timcnius....................... 1176; pi. 310

Age determination_........................ 1136

Airai Clay, Palau Islands, Miocene pollen

flora.............................. 1163

dba, Sonneratia..------... ................... 1140,

1146, 1148, 1151, 1152, 1155, 1160, 1164, 

1168, 1169; pi. 307 

Algae, Miocene, listed...................:..... 1146

Aliquot method........_................... 1134

Allium cepa..... .........._................. 1143

Alocasia............. ......................... 1175

dopecuroides,Acdypha... .................... 1167

amabilis, Eragrostis. .......................... 1143

Amaranthus dubius..... ...................... 1143

viridus.................................... 1143

amarus, Phyllanthus.......................... 1143

americana, Ximenia. ..................... 1143,1151

Anacystis... .................................. 1161

dimidiata......... ...._.................. 1161

angulata, Physalis............................. 1144

antiquae, Eugenia. ....................._... 1173

Aphanocapsa.. ....................... 1146; pi. 304

Aphanothece.. .............................. pi. 304

apiculata, Rhizophora. ........................ 1146,

1148, 1151, 1152, 1160, m<V pi. 308 

aponina, Gomphosphaeria... .................. 1161

argentea, Tournefortia. ........................ 1144,

1146,1149,1151,1152,1160, J/rS; pi. 310 

asiaticum, Crinum............................ 1143

aspera, Achyranthes.......... ................. 1143

Asterigerina.... .............................. 1138

ctfoKerms, Fimbristylis.. ................. 1143,1151

Avkennia...... 1140,1149,1150,1151,1159,1160,1163

marina...... 1146, 1149, 1152, 1160, 1174; pi- 310

mtato................................. 1149,1174

resinfera.. .............._............... 1174

axiOaris, Gynotroches.............. 1148,1179; pi. 308

B 

baccatum, Picrodendron.. ..................... 1178

bracteata,Morindacitrifolia.-.--.....--.._.._._ 1149

Basalt........................................ use

benningseniana, Myrtella....... ............... 1173

bicolor, Sorghum..... ......................... 1143

technicum, Sorghum....................... 1143

6i#ora, Wedelia........................... 1144,1151

[Italic page numbers indicate major references}

Boerhavia repens.......................... 1143,1151

tetrandra.- ........................... 1143,1151

bonariensis, Conyza........................... 1144

bonduc, Caesalpinia........................... 1143

Botrychium................................... 1164

brasiliensis, Ipomoea pes-caprae. .............. 1144

Brassica oleracea capitata...................... 1143

pefezwewsis-............................... 1143

brownii, Cenchrus............................. 1143

Brownlowia................................... 1140

Brucea... .........................1146,^77; pi. 311

javanica................................... 1178

Bruguiera.................................... 1148,

1149, 1150, 1155, 1159, 1160, 1163, 1164, 

1168,1169,1172

Wmnorfttea——1146,1148,1152,1160, m0;pi.308 

sp........................................ 1151

Buchenavia capitata........................... 1171

Caesalpinia bonduc...... ...................... 1143

jayafto. —_-. — -._ — — — _.................. 1155

californ ica, Acalypha............................n&7

Caliopteris floribunda......................... 1171

Callicarpa........ ................. 1146, 1180; pi. 311

acuminata................................ 1180

cana.... .................................. 1180

Cdlitriche..................................... 1146,

1147, 1156, 1159, 1160, 1161, 1162, 1163, 

1178; pi. 311 

christensenii............................... 1178

muelleri................................... 1178

papuana ................................. 1178

Campnosperma. .............................. 1163

cawa, Catticarpa.............................. 1180

Canavalia microcarpa. .................... 1143,1151

capitata, Brassica oleracea..................... 1143

Buchenavia............................... 1171

capuli, Eugenia............................... 1173

Carica papaya................. ......._....... 1143

carolinensis, Elaeocarpus...................... 1179

Randia.... ............................... 1176

casd, /zora......... 1146,1149,1152,1160,^74; pi. 310

caseolaris, Sonneratia...................... 1140,1168

Cassythafiliformis—............ ......... 1143,1151

Caswanwa.................................... 1164

catappa, Terminalia........................... 1146,

1149,1152,1160, Jm, 1172; pi. 309 

catarus, Acalypha.. ........................... 1167

Cenchrus brownii.............................. 1143

echinatus................................. 1143

Ceodes........................................ 1166

cepa, .AMmm..____............................ 1143

Cmops—._ 1148,1149,1150,1151,1159,1160,1163,1170 

roxburghiana.............................. 1149

tagal...... 1146,1148,1149,1152,1160, 1171; pi. 308

sp........................................ 1151

Chamaelaucium............................... 1173

chamissoi, Clbotium........................... 1140

chamissonis, Euphorbia..... ............... 1143,1151

chinensis, Livistona.......................... pi. 305

Chloris inflata................................. 1143

christensenii, Callitriche....................... 1178

Chroococcies................................. pi. 304

Chroococcalean algal assemblages............. 1161

Chroococcalean algal zone ..„...-... 1156,1159,1160 

inferred environment-.------------------- 1162

Cibotium chamissoi............................ 1140

cinerea, Veronica............--.-..--.-.-.----- 1144

cistoides, Tribulus......... ................ 1143,1151

citrifolia, Morinda...----.--------------------- 1144,

1146, 1149, 1151, 1152, 1160, 1162, 1164, 

m5; pi. 311 

bracteata, Morinda......................... 1149

Citrullus vulgaris...........—--------------- 1144

Climate..-..-..-.----------------------- H41

Clorogloea.......... .._ — -- ——------ 1161; pi. 304

Coccochloris stagnina.-..----------------- — — - 1161

cochinchinensis, Randia....................... 1146,

1149,1152,1160, 1176; pi. 310 

Coco* nucifera..... ...------. —--------------- 1143

Code designations.-..---------- ——— - —— -- H46

CodioeMm--..------------------------ —— — - H75

Coelosphaerium-.-................... H46; pi. 304,

Combretum---..---...------------------------ 1146

1149, 1163, 1164,1171, 1178, 1173; pi. 309 

decandrum..-.-.*.-.---- ----------------- 1172

/arj»<WM7ra.-...--.--- —------------------- H72

sguamosum.......................... —- pi. 309

tetralophum........................ H72; pi. 309

communis, Ricinus..-------------------------- 1143

Conyza bonariensis.--...-....--.------------- 1144

Coprosma.......... 1140,1146,1156,1163,^80,-pi. 311

ernodeoides------------------------------- H80

.-.... —— --- 1180 sp.

Cordia. 1143, 1150, 1151, 1159, 1160, 1163, 1173, 1175, 1177

subcordata.. . 1144, 1146, 1149, 1151, 1152, 1160, 1173

coromandelianum, Malvastrum ... -------------- 1143

corymbosus, Timonius..... ------- —— --------- 1176

Crinum asiaticum...-. ... -------- —— ---- — - H43

Cucurbita maxima ...... ... -------------------- 1144

Current drift.------------------- — ---- 1141

Cyathodes........---.- — ------------- 1175

Cycas. _. — ..- — -- — --- — - —— ------- 1166

Cyclosorus goggilodus. . — — --.- ----- ---- -— - Pi- 305

Cynodondactylon.. — ... ... ----- -------------- H43

Cyperus odoratus... --------------------------- H43

Cyrtandra......- —— ............. H46, HW; Pi- 311

Z^/siosepaZa. --------------------- —— ---- U80

urvittei.. ....———- ———— — — — H80

D

Dactyloctenium aegyptium ... ....... ---------- 1143

dactylon, Cynodon. .—. ------- — ------ — ---- H43

decandrum, Cobretum..---. ---------------- I172

Decaspermum—- ----------------------- U49, 1173

ra^/mowdt- ------------------------------ I173

Depositional environment, sedimentary rocks. 1138 

Digitaria prurient.... ....-..- — ——— 1143,1151

dimidiata, Anacystis... . — .--—---— ------ n61

----------------------- 1168

Distribution of floras..----------------- 110U

Dombeya........ — .. —— -— — -- — --- 1167

Drill-hole sediments, pollen density.. — — -- H52

spore and pollen percentages._ — — — — 1157

Drill holes, location....—... — ————— U35

Drosera.- ——-.——- — --—— ———- 1175

dubius,Amaranthus.........—— — - — ------- H43

1183
1184 INDEX

E

eckinatus, Cenchrus-. __-----...__--__. 1143

Elaeocarpus.......... 1146, 1147, 1149, 1159; pi. 311

carolinensis............................... 1179

joga............................... 1179; pi. 311

polystachyus.............................. 1179

elegans, Zinnia................................ 1144

Eleusineindica................................ 1143

Environmental conditions, zones...---------- 1168

Eocene pollen zone, inferred environment.... 1162

Eragrostis amabilis............................ 1143

Erythaea..................................... 1166

Euphorbia.................................... 1144

chamissonis........................... 1143,1151

hirta...................................... 1143

thymifolia................................. 1143

Eocene pollen zone.-.-..-.----...----.-.. 1156,1159

Eriolaena..................................... 1167

ernodeoides, Coprosma........................ 1180

Eucalyptus globulus.......................... 1173

incrassata................................. 1173

.............. 1146,1149,1159,1162; pi. 310

antiquae.................................. 1173

capuli.................................... 1173

lineata.................................... 1173

fattax, Sida..................... 1143,1151,1155,1163

farinosum, Combretum........................ 1172

filiformis, Cassytha........................ 1143,1151

Fimbristylis atottensis..................... 1143,1151

fissicalyx, Tkespesia........................... 1168

Fleurya ruderalis.......................... 1143,1151

Flora, Miocene, relation to other fossil floras.. 1163 

floribunda, Caliopterls......................... 1171

Floristic composition.---...-........--.--.--. 1146

Forests, inferred types...................._. 1162

Forests, Pisonia.............................. 1160

Fosberg, F. E., "Paleobotany of Oceanic

Pacific Islands".................. 1140

quoted............................... 1161,1162

Fossil flora, composition and relation to recent

flora.............................. 1146

frondosa, Mussaenda.................... 1149; pi. 311

G 

Gardenia........................ 1150,1151,1159,1162

grieoei........................ 1146, i/75; pi. 310

sp.................................... 1152,1160

ginginensis, Pterospermopsls............ 1146; pi. 304

glauca, Nicotiana............................. 1144

globulus, Eucalyptus.......................... 1173

Gloeocapsa........................ 1146,1161; pi. 304

turgida.................................... 1161

Gloeothece.............................. 1146; pi. 304

godseffiani, Acalypha.......................... 1167

goggilodus, Cydosorus....................... pi. 305

Gomphosphaeria........................ 1146; pi. 304

aponina.................................. 1161

Goniophlebium ponapense................... pi. 305

graeffi, Randia................................ 1149

granatum, Xylocarpus......................... 1160

grandis, Acalypha............................. 1167

Pisonia................................... 1143,

1146, 1147, 1151, 1152, 1160, 1162, 1166; 

pi. 306 

grievei, Gardenia.................. 1116,1175; pi. 310

gwjava, Psidium.............................. 1173

Guettarda..... 1146,1150,1159,1163,1174, 1175; pi. 310

macrosperma.................. 1150,1176; pi. 310

odorata............................. 1176; pi. 310

speciosa.......... 1144,1150,1151,1155,1175,1176

guineense, Psidium............................ 1173

gymnorhiza, Bruguiera........................ 1145,

1148,1152,1160, 1170; pi. 308 

Gynockthodes.................................. 1174

Gynotroches........ 1146,1148,1149,1159,^70; pi. 308

ozflterw...................... 1148, 1179; pi. 80S

Gyraulus........ .........__._._._... nei

H

Habitats of modern taxa..............._.... 1160

Hampea...................................... 1167

hayem, Terminalia........................... 1171

Heliotropium................................. 1173

Hippocratea................................... 1147

macrantha................................ 1179

hirta. Euphorbia.............................. 1143

hispida, Acalypha............................. 1167

hydrophyllacea, Scyphiphora.. ................. 1149,

1160, 1177; pi. 311

Hydrostachys. ............._..___-.---..-. 1175

incrassata. Eucalyptus........................ 1173

indica, Acalypha.............................. 1167

Eleusine.................................. 1143

Pluchea................................... 1144

Indo-Pacific ?enera...................... 1150,1151

insularis, Tricachne... ....................._ 1143

involuta, Thuarea........................ 1147,1151

Ipomaea...................................... 1167

Ipomoea pes-caprae...................... 1144,1151

pes-caprae brasiliensis. .................... 1144

purpurea................................. 1144

tuba................................. 1144,1151

Ixora. .............. 1149,1150,1151,1159,1162,1163

casei.. ....... 1146, 1149, 1152, 1160, 1174; pi- 310

volkensii.................................. 1174

jalapa, Mirabilis.............................. 1143

javanica, Brucea.............................. 1178

javanicum, Trkhomanes..................... pi. 305

javanicus, Cyperus............................ 1143

jayabo, Caesalpinia............................ 1155

joga, Elaeocarpus..................... 1179; pi. 311

K 

kafu, Pandanus............................... 1165

Kleinhamia................................... 1163

korthalsiana, Salacia.......................... 1179

Lactuca saliva................................ 1144

Laguncularia racemosa........................ 1171

lampas, Thespesia.. ........... —............. 1146,

1151,1152,1160,1162,1163, 1167, 1168; pi. 306 

Lemna........................................ 1161

leontopetaloides, Tacca......................... 1143

leptopoda, Acalypha........................... 1167

Lepturus repens.......................... 1143,1151

repens occidentalis........................ 1143

repens................................ 1143

septentrionalis......................... 1143

Limestone_............-.-..---..--..--..... 1136

lindheimeri, Acalypha......................... 1167

lineata, Eugenia............................... 1173

Lithology..._........„......„.. — .. — ..„. 1136

Lithophyllum................................. 1138

littorea, Lumnitzera........................... 1146,

' 1149,1151,1152,1160, 1172; pi. 309 

Livistona..-...................... 1146,1166; pi. 305

chinensis................................. pi. 305

Location of study area.....—.............— 1140

Lumnitzera.....---.---.....---.....-......... 1148,

1149, 1150, 1155, 1159, 1160, 1163, 1169, 

1172; pi. 309 

littorea.... 1146,1149,1151,1152,1160,^73; pi. 309

racemosa...................... 1149,1172; pi. 309

lutea, PortuJaca... ........................ 1143,1151

lycopersicum, Solanum........................ 1144

Lycopodiumplegmaria ........................ 1163

i, Cyrtandra......................... 1180

M

macrantha, Hippocratea....................... 1179

macrosperma, Guettarada.......... 1150,1176; pi. 310

Malaisia ......................... 1146,^77; pi. 311

scandens............................ ...... 1177

tortuosa...........__..__...... ——.... 1177

Malvastrum coromandelianum.. ................ 1143

mangle, Rhizophora...... 1143,1148,1169,1170; pi. 308

Mangrove swamp forms....................... 1159

marina, Avicennia.. 1146,1149,1152,1160, 1174; Pi- 310

Vigna................................. 1143,1151

marttima, Suriana......................... 1143,1151

Matisia....................................... 1167

maxima, Cucurbtta............................ 1144

mays, Zea..................................... 1143

melo, Cucumis................................ 1144

Methods of study__........._............ 1144

Micrhystridium tenuissimum............ 1146; pi. 304

microcarpa, Canavalia..................... 1143,1151

Micronesian species...-...-..___... —.... 1151

MUiusa.... ................................... 1164

Miocene flora, distribution.................... 1160

MirabUis jalapa............................... 1143

Modern flora, distribution.................... 1161

Modern pollen rain........................— 1168

Morinda. ....................... 1149,1150,1159,1163

citrifolia... ................................ 1144,

1146, 1149, 1151, 1152, 1160, 1162, 1164, 

1175; pi. 311 

bracteata. ............................. 1149

umbeUata........................... ...... 1175

Morus........................................ 1177

mucronata, Rhizophora...... ........... —.... 1146,

1148, 1151, 1152, 1159, 1160, 1169, 1170; 

pi. 308 

mueUeri, Cattttrkhe...—...................... 1178

multibracteata, Thespesia...................... 1168

Mussaenda........................ 1146,1175; pi. 311

frondosa................ ............1149; pi. 311

Myrtella.......... ............................. 1173

benningseniana......... .........———---- 1173

N 

naumannii, Silacia...... .....———————-- 1179

Nepenthes.......--------------------- — ------ 1175

Neritilia... ....................... — — — — 1161

Nicotiana glauca...................--------— 1144

nitida, Avicennia... ...................... 1149,1174

North Equatorial Current....... ———....... 1141

Northiopsis.. ................................. 1163

nucifera, Cocos...........................----- 1143

Nypa..--------------------------------- H40,1160

O

occidentalis, Lepturus repens............ — ..... 1143

Oceanic Pacific islands, paleobotany.......... 1140

Ochrosia...................-.....—. — . — - H43

oppositifolia.......................... 1144,1151

odorata, Guettarda...................... 1176; pi. 310

odoratus, Cyperus.-.....------.--.------------ H43

oleracea, Portulaca............................ 1143

capitata, Brassica.......-----...-------— 1143

opposttifolia, Ochrosia.................... 1144,1151

ordorate, Pluchea..........----------- — ------ 1144

Ornatanomolina.—.......-.-.---.------------- 1138

Pacific island species..-..----..-----.-------- 1151

Palau Islands, Miocene pollen.. —...- ——— -- 1163 

Paleoecology.._. — - —... ——.....---.— 11S8

Pandanus...---...-...- ---------- —— - — ---- U43,

1146, 1147, 1150, 1156, 1159, 1162, 1163, 

1166, 1175 

kafu........................... --------- 1165

teaoriut................ 1143, 1151, 1165; pi. 305

sp................ 1151, 1152, 1155, 1160; pi. 305

Pantropical genera.........---..---.---- 1150,1151

papaya, Carica......... .... —....---------— 1143

papuana, Callttrkhe.....--...---------------- 1178

patettifera, Thespesia.......................... 1168

peekelii, Thespesia ................ 1167,1168; pi. 306

pekinensis, Brassica...-. ........ — ----- — --- 1143
INDEX 1185

Pemphis................................. 1143,1177

acidula......- —..................... 1143, 1151

Peneroplis Mloculina......................... 1138

pes-caprae, Ipomoea...................... 1144,1151

brasiliensis, Ipomoea....................... 1144

Phaseolus vulgaris.......-.-..-.--------------- 1143

Phegopteris.----------------------- ----------- 1155

Phyllanthus amarus.................-..--.-..- 1143

Physalis angulata............................. 1144

Picrodendron...................... 1146, 1178; pi. 311

baccatum.................................. 1178

Pisonia....................................... 1142,

1143, 1147, 1150, 1156,1162, 1168, 1174, 

1175

forest-........-.---.------------ 1142, 1160

grandis................................... 1143,

1146, 1147,1151, 1152, 1160,1162, 1166; 

pi. 306

umbellifera......-...-...--.---.---------.- 1147

Placoma............................... 1161; pi. 304

plegmaria, Lycopodium........................ 1163

Pluchea indica................................ 1144

ordorate................................... 1144

Pollen, Miocene, listed—........————- — - 1146

Pollen collections (modern)..—. — -.-—....— 1145

Pollen density in sediments, eastern Micronesia...........—------- 1152,1156

Gulf of Paria, Venequela. — ..——— — — — 1155

Pollen rain, Micronesia....._._. — . — —— . 1152

polygamus, Timonius......................... 1150

Polypodium scolopendria............. 1143,1147,1151

polystachyus, Elaeocarpus..................... 1179

ponapense, Goniophlebium................... pi. 305

populnea, Thespesia...................... 1147,1168

Portulacalutea—......................... 1143,1151

cleracea................................... 1143

samoensis............................. 1143,1151

princides, Solatia....................... 1179; pi. 306

procumbens, Triumfetta................... 1143,1151

pruriens,Digitaria........................ 1143,1151

Psidium guajava........................^..... 1173

guineense.................— ........ — .. 1173

Pteris......................................... 1163

Pterospermopsis ginginenais..........:.. 1146; pi. 304

Ptychosperma................................. 1166

purpurea, Ipomoea............................ 1144

R 

racemosa, Laguncularia........................ 1171

Lumnitzera.................... 1149,1172; pi. 309

Randia- 1149,1150,1151,1159,1162,1163,1176; pi. 311 

carolinensis............................... 1176

cochinchinensis. 1146,1149,1152,1160, 1176; pi. 310 

graeffi.................................... 1149

Rapa, fossil pollen................... — ....-.. 1163

Raphanus sativus............................. 1143

raymondi, Decaspermum...................... 1173

Recent flora, relation to fossil flora........... 11 !ft

Reference collection.......................... 1145

repens, Boerhavia.......................... 1143,1151

Lepturus............................. 1143,1151

repens................................ 1143

ocddmtalis, Lepturus..................... 1143

repens, Lepturus.......................... 1143

septentrionalte, Lepturus.................. 1143

resinfera,Amcennia........................... 1174

Rhizophora.................................... 1140,

1147, 1149,1150,1155, 1156,1159, 1160,1162, 

1163, 1164, 1169, 1170, 1171; pi. 308 

apiculata...... —— ———————————— 1146,

1148, 1151, 1152, 1160, 1169; pi. 308 

mangle.............. 1143,1148,1169,1170; pi.308

mucronata................................ 1146,

1148, 1151, 1152,1159, 1160,1169, 1170; 

pi. 308

Rhizophora— Continued

zone—— —— — — — — ——— 1156,1159, 1160

inferred environment.--._.......... 1163

sp..... — .. — .... ——....... 1146,1169; pi. 308

Rhodamnia............................... 1149,1173

trinervia............................ 1173; pi. 310

Ricinus communis............................. 1143

Rock types_.„ — .. —— .... —.... — .... — .— 1136

Rockia........................................ 1166

rosea, TrichoHaena............................. 1143

roxburghiana, Ceriops......................... 1149

ruderalis, Fleurya........................ 1143,1151

S 

Sadleria....................................... 1140

Salacia.................. 1146,1147,1159, 1178; pi. 306

korthalsiana............................... 1179

naumannii................................ 1179

princides........................... 1179; pi. 306

zenkeri.................................... 1179

Salacicratea................................... 1147

samoensis, Portvlaca..................... 1143, 1151

Terminalia...... 1144, 1149,1151,1165, 1171,1174

Sample preparation. ...... —. — . — — ....— 1144

Santalum...-.-----------..-.....--------.--.. 1168

Santalumidites................................ 1168

saliva, Lactuca................................ 1144

sativus, Raphanus............................. 1143

Scaevola ...................................... 1177

taccadT..—.......................... 1144, 1151

scandens, Malaisia............................. 1177

Schizaea...................................... 1163

scolopendria, Polypodium............ 1143,1147,1151

Scyphiphora....................... 1146. 1177; pi. 311

hydrophyllacea......... 1149, 1160, 1177; pi. 311

secundiflora, Sophora..................... 1147,1177

. —— ... —.. ———— ... ——— . 1163 

s, Lepturus repens............... 1143

Setaria verticillata............................. 1143

Sida.......................................... 1147

fallax...................... 1143, 1151, 1155,1163

Snails..... ——— — —— ———— — . — . 1161,1162

Solanum lycopersicum......................... 1144

Sonneratia.................................... 1147,

1149, 1150, 1159, 1160, 1163, 1171, 1172 

alba....................................... 1140,

1146, 1148,1151,1152, 1155, 1160, 1164, 

1168, 1169; pi. 307 

casedaris............................. 1140,1168

zone..— — — -- — — —- — — — — --— 1159

inferred environment... — — ... — — . 1163 

Sophora.. .... 1146,1147,1159,1173,1174, 1177; pi. 306

secundiflora........................... 1147,1177

tomentosa..................... 1147,1177; pi. 306

Sorghum bicolor............................... 1143

bicolor technicum.......................... 1143

Spathyphyllum................................ 1163

spedosa, Guettarda.... 1144,1150,1151,1155,1175,1176

Spores, Miocene, listed._........... __.... 1146

squamosum, Combretum..................... pi. 309

stagnina, Coccochloris......................... 1161

Styphelia..................................... 1175

subcordata, Cordia............................. 1144,

1146,1149,1151,1152,1160, 1173 

Suriana...................................... 1177

maritima............................. 1143,1151

Tocca.................---. — -„....--..... 1155

leontopetaloides............................ 1143

taccada, Scaevola.......................... 1144,1151

tagal, Ceriops. 1146,1148,1149,1152,1160, 1171; pi. 308 

Tarenna...................................... 1179

Taxonomic procedure._ ——....... —.... — . 1134

Taylor,W. R., quoted...--..-.---.-------. 1171

technicum, Sorghum bicolor.................... 1143

tectorius, Pandanus.......... 1143,1151,1165; pi. 305

tenuissimum, Micrhystridium........... 1146; pi. 304

Terminalia................ 1150,1159,1163,1164,1171

catappa... 1146,1149,1152,1160, 1171, 1172; pi. 309 

hayesii.................................... 1171

samoensis......... 1144,1149,1151,1165,1711,1174

sp....————..——. ——................ 1151

tetralophym, Combretum................ 1172; pi. 309

tetrandra, Boerhavia....................... 1143,1151

Thespesia....................... 1147,1150,1159,1163

flssicalyx................................. 1168

lampas................................... 1146,

1151,1152, 1160,1162, 1163, 1167, 1168; 

pi. 306 

multibracteata............................. 1168

patellifera................................. 1168

peekelii....................... 1167,1168; pi. 306

populnea............................. 1147,1168

Thuareainvoluta.......................... 1147,1151

thymifolia, Euphorbia......................... 1143

Timonius............... 1146,1150,1163, 1176; pi. 310

affinis............................. 1176; pi. 310

corymbosus................................ 1176

polygamus................................ 1150

tomentosa, Sophora................ 1147,1177; pi. 306

tortuosa, Malaisia............................. 1177

Tournefortia.................................. 1149,

1150,1159,1160,1162,1174,1175,1177 

argentea.................................. 1144,

1146, 1149, 1151, 1152, 1160, 1173; 

pi. 310

Trade winds——-..---..---..---... 1141 

pollen transport........ —.. — . — ._.... 1162

Transport hypothesis.-_._........_.... 1162

Trema................................... 1155,1177

Tribulus...................................... 1144

cistoldes............................. 1143,1151

Tricachne insularis........................... 1143

Tricholaena rosea.............................. 1143

Trichomanes........................... 1146; pi. 305

javanicum............................... pi. 305

triloculina, Peneroplis......................... 1138

trinervia, Rhodamnia................... 1173; pi. 310

Triumfetta procumbens................... 1143,1151

tuba, Ipomoea............................ 1144,1151

turgida, Gloeocapsa........................... 1161

U 

umbellata, Morinda........................... 1175

umbettifera, Pisonia........................... 1147

urvillei, Cyrtandra............................ 1180

V, W

Vascular flora (modern) of Eniwetok......... 1U3

Vegetation zones, northern Marshall Islands.. 1142 

velutina, Achyranthes.................... 1143,1151

Veronica cinerea............................... 1144

verticillata, Setaria............................. 1143

Vigna marina.....-......-....---..-.---- 1143,1151

viridus, Amaranthus........................... 1143

volkensii, Ixora..------........................ 1174

vulgaris, Citrullus............................. 1144

Phaseolus................................ 1143

Wedeliabiflora.-........................ 1144,1151

wilkesiani, Acalypha.......................... 1167

X 

Ximeniaamericana................ — —— 1143,1151

Xylocarpus................................... 1160

granatum............... ... — — -——. — — 1160

Zeamays.............................. ....... 1143

zenkeri, Salacia-.-.-.......-.---.------------- 1179

Zinnia elegans...-. — - — — — .- — — - — — — 1144

Zones, environmental conditions——.-..-.... 1168

floral sequence.——.... — —— - ——— — 11&6

U.S. GOVERNMENT PRINTING OFFICE:!969 Ow-336-388

PLATES 304-311
PLATE 304

FIGURES 1-8. Chroococcales, Algae, Miocene of Eniwetok, X 800.

1. Gloeothece type, Dl200-9(2), 97.5 X 9.4.

2. Gloeothece type, D1200-9(2), 98.1 X 3.7.

3. Gomphosphaeria type D1200-7A(2), 88.3 X 8.5.

4. Aphanothece type, D1200-9(2), 100.8 X 5.5.

5. Gloeocapsa type, D1200-10B(2), 103 X 7.2.

6. Gloeothece type, D1200-10B(2), 111.5 X 7.

7. Coelosphaerium type, Dl200-9(2), 100.4 X 3.

8. Chroococcus type, D1200-7A, 78.4 X 16.6. 

9-13. Chroococcales, Recent algae from lagoon margin, Onotoa Atoll, Gilbert Islands, X 800.

9. Clorogloea type, D1657(l), 97.3 X 14.6.

10. Clorogloea type, D1657(1), 78.5 X 9.5.

11. Clorogloea type, endospore D1657(l), 90 X 15.4.

12. Placoma type, D1657(1), 92.4 X 15.1.

13. Placoma type, D1657(l), 81.1 X 19.4. 

14-18. Algal cysts and Hystrichosphaeridae, Miocene of Eniwetok.

14. Pterospermopsii, cf. P. ginginensis Deflandre & Cookson, D1215-A(1), 16.1 X 89.5, X 600.

15. Cyst, undet., D1200-2(2), 108.2 X 10, X 800.

16. Cyst, undet., D 1200-2(2), 106.6 X 10, X 800.

17. Micrhystridium tenuissimum Deflandre, D1215-C (2), 93X5.3,X600.

18. Aphanocapsa type, D1200-9(2), 104 X 13.1, X 600.

19. Microtome thin section, transverse section of laminae of lignitic fragment, Miocene of Eniwetok, D1200-4 (B-4), 

117.2 X 19.4, X 248. Colonies of Gloeothece and Gloeocapsa types total about 11,000 per gram of sediment at 

this sample level; however, their structures could not be discovered from these microtome sections.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 260-11 PLATE 304

17

18 19 -

MIOCENE ALGAE AND MARINE CYSTS FROM ENIWETOK 

AND RECENT ALGAE FROM THE GILBERT ISLANDS
PLATE 305

[All magnifications X 800]

FIGURES 1, 2, 5. Fossil spores of the Polypodiaceae type, code species M-sm(l).

1. D1215-C(2), 81 X 15.

2. D1215-C(2), 93.9 X 4.1. 

5. D1215-D(3), 82.5 X 11.7. 

3, 4. Modern spores of Polypodiaceae and Aspidiaceae.

3. Goniophlebium ponapense Copeland p!584, Ponape, Glassman colln. 2378.

4. Cyclosorus goggilodus (L.) Link p!578, Ponape, Glassman colln. 2446. 

6-8. Fossil spores, Polypodiaceae type, code species Tl-sm(2).

6. D1215-D(3), 104.8 X 13. 

7, 8. D1215-D(3), 12.6 X 100.9. 

9, 10. Fossil spore, Hymenophyllaceae type, cf. Trichomanes, code species Tl-p(2). D1215-D(6), 88.4 X 16.2.

11. Fossil spore, D1215-C(2), 102.7 X 13.3.

12. Modern spore, Trichomanes javanicum Blume p!422B, Yap Island, Wong colln. 371. 

13-15. Fossil spore, Pteridaceae types.

13, 14. D1215-D(3), 100.3 X 13.5 (cf. Dennstaedtia).

15. D1215-D(3), 100.7 X 7.8. 

16, 18, 19. Fossil pollen, Pandanus sp. (p. 1165).

16. D1215-B(3), 96.5 X 12.6. 

18, 19. D1215-B(3), 85.7 X 10. 

17. Modern pollen, Pandanus tectorius Sol. p!224, Hawaii, W. H. Elder colln.

20. Fossil, Livistona type, (p. 1166). 

D1215-B(3), 15.5 X 86.8.

21. Modern, Livistona chinensis var. subglobosa (Mart.) Becc., p441, Okinawa, Reid Moran colln. 5058.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 260-11 PLATE 305

20

21

MIOCENE FERN SPORES AND MONOCOTYLEDONOUS POLLEN OF ENIWETOK 

AND SELECTED MODERN COUNTERPARTS
PLATE 306

[All magnifications X 800]

FIGURES 1-5. Pollen of Nyctaginaceae (p. 1166).

1. Fossil, Pisonia cf. P. grandis.

D1200-6(l), 96.5 X 12.5. 

2-4. Modern, Pisonia grandis R. Br. pl731, Marshall Islands, Fosberg colln. 34263.

5. Fossil, Pisonia cf. P. grandis. D1215-B(3), 6.4 X 104. 

6-8, 14-16. Pollen of ?Leguminoseae (p. 1177).

6-8. Fossil, Sophora type, D1200-2(2), 101.4 X 8.

14-16. Modern, Sophora tomentosa L. p!767, Tonga, Yuncker colln. 15865. 

9-11, 17-19. Pollen of Euphorbiaceae (p. 1167).

9, 10. Fossil, Acalypha, D1215-E(2), 19.2 X 81.4.

11, 17-19. Modern, Acalypha sp.; p!536, Ponape, Glassman colln. 2916. 

12, 13, 20, 21. Pollen of ?Hippocrateaceae (p. 1178).

12, 13. Fossil Salacia type, D1215-D(7), 71.4 X 16.9.

20, 21. Modern Salacia princides DC. p!803, N. Borneo, A. Villamil colln. 286. 

22-26. Pollen of Malvaceae (p. 1167).

22, 23. Fossil Thespesia cf. T. lampas. D1215-A(1), 12.7 X 96.2, D1215-E(1), 85.8 X 15.8.

24. Fossil Malvaceae, undet., D1215-E(1), 85.8 X 15.8. '

25. Modern Thespesia peekelii (Ulbr.) Borss., p3183, New Guinea, P. J. Darbyshire colln. 174.

26. Modern Thespesia lampas Dalz. ex Dalz. & Gibs., p2031, Lacchrwale, Mohammad colln.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 260-11 PLATE 306

MIOCENE DICOTYLEDONOUS POLLEN OF ENIWETOK AND THEIR MODERN COUNTERPARTS, 

NYCTAGINACEAE, 7LEGUMINOSEAE, EUPHORBIACEAE, 7HIPPOCRATEACEAE, MALVACEAE
PLATE 307

[All magnifications X 800]

FIGURES 1-6, 12-21. Fossil pollen, Sonneralia cf. S. alba J. Sm. (p. 1168). Equatorial views.

1. D1215-D(4), 106 X 19.7.

2-4. D1215-D(3), 11.5 X 85, high, middle, and low focus. 

5, 6. D1215-D(3), 92.9 X 16.7, high, and middle focus. 

12, 13. D1215-D(3), 96.8 X 14.9, high and middle focus.

14. D1215-D(7), 71.7 X 13.5.

15, 16. D1215-D(2), 89.7 X 18.6, high and middle focus. 

17, 18. D1215-D(3), 94.8 X 12.9.

19. D1215-D(4), 110.5 X 18.5. 

20, 21. D1215-D(3), 99.4 X 14.8. 

7-11, 22-24. Modern pollen, Sonneralia alba J. Sm.; equatorial views, pl984, Kusaie, H. F. Moore colln. 76.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 260-11 PLATE 307

MIOCENE SONNERATIACEAE POLLEN OF ENIWETOK AND MODERN COMPARATIVE MATERIAL
PLATE 308

[All magnifications X 800]

FIGURES 1-8, 19. Fossil pollen, Rhizophora cf. R. apiculata BL, equatorial views (p. 1169). 

1, 2. D1200-2(2), 107.4X8, middle and high focus.

3. D1200-2(2), 75.3X9. 

4, 5. D1215-A(1), 91X13, high and middle focus.

6. D1215-A(1), 90.7X13.3.

7, 8. D1200-2(2), 98.8X19, high and middle focus. 

19. D1215-A(1), 92.8X14.6, clump of nine grains. 

9-16, 22, 23. Modern pollen, Rhizophora apiculala BL, p!996, Sumatra, Liitzeharm colln. 5201.

9-16. Equatorial views. 

22, 23. Polar views. 

17, 18. Fossil pollen, Rhizophora sp., polar views.

17. D1215-A(1), 100.5X11.8.

18. D1215-B(3), 116X16.6.

20, 21, 26, 27. Fossil pollen, Rhizophora cf. R. mucronata Lam., equatorial views (p. 1170). 

20, 21. D1215-A(1), 100.9X8.1.

26. D1200-1(1), 91.6X5.1, note polar columellae in wall.

27. D1215-A(1), 88X8.7.

24, 25, 33-35. Modern pollen, Rhizophora mucronata Lam., equatorial views, p!989, New Caledonia, McKee colln. 2073. 

28-30. Fosfil pollen, Rhizophora sp.

28. D1215-A(1), 105.9X9.1, equatorial view.

29. D1215-A(1), 90.1X9.2, equatorial view.

30. D1215-E(2), 93.5X6.1, polar view.

31, 32, 40. Fossil pollen, Bruguiera cf. B. gymnorhiza (L.) Merr. (p. 1170). 

31, 32. D1215-B(4), 94.6X13.3. Compare with figs. 38, 39.

40. D1215-B(3), 85.7X10. Compare with fig. 49.

36, 37. Modern pollen Rhizophora mangle L., equatorial and polar views, p!292, Venezuela, R. H. Tschudy colln. 293. 

38, 39, 49. Modern pollen, Bruguiera gymnorhiza (L.) Merr., equatorial views, p!560, Ifalik, Abbott and Bates colln. 27 

41-43. Fossil pollen, Ceriops cf. C. tagal (Perr.) C. B. Rob. (p. 1171). Compare with figs. 50-52.

41. D1215-B(3), 91X15, equatorial view.

42. D1215-A(1), 86X11, equatorial view.

43. D1215-A(1), 91.5X11.3, polar view. 

44, 45. Fossil pollen, ?Rhizophoraceae, Gynotroches type. (p. 1179). Compare with figs. 53-55.

44. D1215-D(3), 95.1X15.5, equatorial view.

45. D1215-A(1), 104.5X19.7, polar view. 

46-48. Fossil pollen, Rhizophora sp.

46, 47. D1215-A(1), 91.4X18.5.

48. D1200-l(4), 97X8.2. 

50-52. Modern pollen, Ceriops tagal (Perr.) C. B. Rob., two equatorial views, one polar view, p!986, Wilhelmsland, K.

Weinland colln., USNH 795002.

53-55. Modern pollen, Gynotroches axillaris BL, p!455, Ponape, Glassman colln. 2550. 

56-65. Fossil pollen, cf. Rhizophora.

56. D1215-B(3), 100.IX 14.8, polar view.

57. D1215-B(4), 104.2X9.9, equatorial view. 

58, 59. D1200-2(2), 99X19.3, high and medium focus.

60. D1200-2(2), 100X18.1, broken along two colpae. 

61, 62. D1200-2(2), 89.5X9, canted polar view. 

63, 64. D1652(1), 100.5X14.2 (Guam, Miocene). 

65. D1652(l), 84.8X17 (Guam, Miocene).
GEOLOGICAL SURVEY PROFESSIONAL PAPER 260-11 PLATE 308 

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13

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19

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27 28 31

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48

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59 62 64 65

MIOCENE RHIZOPHORACEAE POLLEN OF ENIWETOK AND GUAM 

AND MODERN COMPARATIVE MATERIAL
PLATE 309

[All magnifications X 800]

FIGURES 1-5. Fossil pollen, Terminalia cf. T. catappa (p. 1171).

I, 2. D1215-D(3), 83X10.5, polar view. 

3,4. D1215-D(3), 102X10, polar view.

5. D1215-D(3), 86.7X16.9, equatorial view. 

6, 7. Fossil pollen, cf. Combretum. D1215A, 11.8X85 (p. 1172). 

8-14. Modern pollen, Terminalia catappa L., p2046, Guam, Anderson colln. 191. 

8-10. Polar views.

II. Canted polar view (more typical than true polar view because of prolate shape). 

12-14. Equatorial views.

15, 16, 19, 21. Modern pollen, Combretum tetralophum Clarke, p!846, Borneo, Foxworthy colln. 9. 

15, 16. Polar views. 

19, 21. Equatorial views.

17, 18, 20. Modern pollen, Combretum squamosum Roxb., p!847, Sumatra, Toroes colln. 3951. 

17, 18. Polrj- views.

20. Equatorial view.

22-26. Fossil pollen, Lumnitzera cf. L. littorea (Jack.) Voight. 

(p.1172).

22. D1200-l(2), 104.3X7.5, polar view. Compare with fig. 27. 

23, 24. D1215-C(1), 102X17, canted grain, high and middle focus. 

25, 26. D1200-l(l), 99.7 X 17.5, equatorial view, high and middle focus.

27-31, 37-39. Modern pollen, Lumnitzera littorea (Jack.) Voight, p!469, Ponape, Glassman colln. 2452. 

27-30. Polar views in high and middle focus; note veinlike areas of ektexine thinning. 

31, 39. Canted polar view.

37, 38. Equatorial view, high and middle focus. 

32-36. Fossil pollen, Lumnitzera cf. L. littorea (p. 1172). 

32,33. D1200-l(2), 96.8X8. 

34,35. D1200-l(2), 102.4X1.8. 

36. D1200-l(2), 96.7X3.7.

40. Modern pollen, Lumnitzera racemosa Willd., p2032, Philippines, McGregor colln. 1718, equatorial view.

41. Fossil pollen, cf. Lumnitzera. D1215-D(2), 99.3X14.5.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 260-11 PLATE 309

41.

MIOCENE COMBRETACEAE POLLEN OF ENIWETOK AND MODERN COMPARATIVE MATERIAL
PLATE 310

[All magnifications X 800]

FIGURES 1-3. Pollen of Myrtaceae (p. 1172).

1, 2. Fossil, cf. Eugenia. D1215-D(3), 96.7X16.0.

3. Modern, Rhodamnia trinervia (Sm.) Blume, p566, China, F. C. How colln. 71052. 

4-9. Pollen of Boraginaceae (p. 1173).

4, 5. Fossil, Tournefortia cf. T. argentea L. D1215-C(2), 89.3X 15.5, equatorial view, high and middle focus.

6-9. Modern, Tournefortia argentea L., p!914, Marshall Islands, Fosberg colln. 33643. Three equatorial views,

high and middle focus; one polar view at middle focus. 

10-12. Pollen of Verbenaceae (p. 1174).

10. Fossil, Avicennia cf. A. marina, Forsk. D1215-B(3), 87.2X14.8, middle focus. 

11, 12. Modern, Avicennia marina var. rumphiana (Hall, f.) Balsh., p!995, Philippines, Ferraris and Stadt Miller

colln. 20800, high and middle focus. 

13-40. Pollen of Rubiaceae (p. 1174).

13-15. Fossil, Ixora cf. I. casei Hance. D1215-C(2), 105.8X15, high, middle and low focus. Compare with figs.

18-20 (p. 1174). 

16, 17. Fossil, Gardenia cf. G. grievei Home (p. 1175). D1215-C(2), 80X14. Tetrad with one broken cell, high and

middle focus. Compare with figs. 24, 25.

18-20. Modern, Ixora casei Hance, p2043, Caroline Islands, Hosaka colln. 3207, polar views. 

21, 22. Fossil, cf. Timonius (p. 1176). D1215-D(3), 103X8.9, high and middle focus. Compare with figs. 26, 27.

23. Fossil cf. Timonius (p. 1176). D1215-D(4), 84.1X16.5. Compare with fig. 28. 

24, 25. Modern, Gardenia grievei Home, p!930, Fiji, A. C. Smith colln. 6694. 

26-28. Modern, Timonius affinis A. Gray, p!896, Fiji, A. C. Smith colln. 4159. 

29, 30. Fossil, cf. Guettarda (p. 1175). D1200-5(l), 94.5X16.4. Compare with figs. 35-38. 

31, 32. Fossil, Randia cf. R. cochinchinensis (Lour.) Merr. (p. 1176). D1215-B(3), 101.IX 12.4; probably four pores.

Compare with figs. 33, 34, 39, 40. 

33, 34. Modern, Randia cochinchinensis (Lour.) Merr., p2037, Guam, Hosaka colln. 3051, equatorial view showing

three pores, high and middle focus.

35, 36. Modern, Guettarda odorata (Jacq.) Lam., p2035, Panama, Erlanson colln. 155. 

37, 38. Modern Guettarda macrosperma, p!062, Costa Rica, Paul H. Alien colln. 5642. 

39, 40. Modern, Randia cochinchinensis (Lour.) Merr., p2038, Saipan, Fosberg colln. 25222.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 260-11 PLATE 310

40

MIOCENE DICOTYLEDONOUS POLLEN OF ENIWETOK AND THEIR MODERN COUNTERPARTS, 

MYRTACEAE, BORAGINACEAE, VERBENACEAE, RUBIACEAE
PLATE 311

[All magnifications X 800]

FIGURES 1-16. Pollen of Rubiaceae, polar views in high and middle focus.

1, 2. Fossil, Morinda cf. M. cilrifolia L. (p. 1175). D1200-1(1), 91.8X8.6. 

3, 4. Fossil, cf. Mussaenda, D1200-1(2), 98.1X12.1.

5, 6. Modern, Morinda cilrifolia L., p!893, Amboina, C. B. Robinson colln. 155. 

7, 8. Modern, Mussaenda frondosa L., p2039, Palau, Fosberg colln. 32132. 

9, 10. Fossil, Morinda cf. M. citrifolia L. (p. 1175). D1215-D(2), 88.6X16.7. 

11, 12. Fossil, Rubiaceae undet., D1215-D(7), 75.9X21.2. 

13, 14. Fossil, cf. Scyphiphora (p. 1177). D1215-D(3), 102.8X16.1.

15, 16. Modern, Scyphiphora hydrophyllacea Gaertn., p!895, Australia, Hoagland colln. 4378. 

17. Undetermined spore, code species Tl-sm(5); D1200-3(1), 89.7X17. 

18-27, 30-37. Dicotyledonous pollen; family assignment uncertain (p. 1177).

18. Code species P2-sm(l); ?Moraceae, Malaisia type (p. 1177). D1200-4(2), 93.9X6.6; diporate with 

smooth wall.

19. Code species P4-p(l); ?Simarubaceae, Picrodendron type (p. 1178). D1215-C(2), 97.8X15.9.

20. Code species P4-r(l); ?Rubiaceae, Randia type. D1200-2(2), 95.7X14.4; pentaporate with infrabacculate 

wall.

21. Code species C3-sm(3); ?Gesneriaceae, Cyrtandra type (p. 1180). D1200-6(1), 107.6X6.1; tricolpate with

psilate wall. 

22, 23. Code species C3-r(l); ?Verbenaceae, Callicarpa, type (p. 1180). D1215-A(1), 89.8X11, and D1215-E(2),

96.1X10.1; tricolpate with reticulate sculpture. 

24. Code species C4-r(l); ?Callitrichaceac, CaUitriche type (p. 1178). D1215-A(1), 104.9X15.8; tctracolpate

scabrate sculpture. 

25-27. Code species C3P3-sm(10); ?Elaeocarpaceae, Elaeocarpus, type, polar view (p. 1179). 27, D1215-A(1), 104.5

X19.7; and 25, 26, Dl215-D(3), 80.1X10.2. Compare with figs. 28, 29. 

30, 36. Code species C3P3-sm(9), D1215-C(2), 95X15.9; tricolporate, with smooth wall.

31. Code species C3P3-st(l), ?Simarubaceae, Brucea type (p. 1177). D1215-F(1), 98X16.9; tricolporate with

striatoid reticulate sculpture. 

32, 33. Code species C3P3-sm(8) ?Elaeocarpaceae, Elaeocarpus type, equatorial view (p. 1179). D1215-D(3),

90X15. 

34, 35. Code species C3P3-r(10), D1200-l(l), 94.4X6.9; tricolporate with scabrate wall.

37. Code species C5P5-r(l); ?Rubiaceae, Coprosma type (p. 1180). D1200-6(l), 87.4X16.3; pentacolporate

with granulate wall. 

28, 29. Modern, Elaeocarpus joga Merr., p. 1813, Guam, Robert Rodin colln. 804.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 260-11 PLATE 311

v_

9 25 • ^*26 A 27 -a. 28 ©29

37

MIOCENE DICOTYLEDONOUS PO-LLEN OF ENIWETOK AND THEIR MODERN COUNTERPARTS, 

RUBIACEAE AND UNDETERMINED POLLEN TYPES