Bulletins of American paleontology (Bull. Am. paleontol.) Vol 357

RESq

DECEMBER 3L

NUMBER 357

A Paleobiotic
the

Survey of Caribbean Faunas from

Neogene of the Isthmus of Panama
edited by

Laurel

S. Collins

and Anthonv G. Coates

Panama Paleonto

1999


PALEONTOLOGICAL RESEARCH INSTITUTION
Ojficers

Shirley K. Egan

President

John C. Steinmetz
Thomas E. Whiteley
Henry W. Theisen
Howard P. Hartnett

First Vice-President

Second Vice-President
Secretary
Treasurer
Director

Warren

D.

Allmon

Trustees

J.

Megan D. Shay
Mary M. Shuford

Brett
L. Crepet
Thomas Dutro, Jr.

Carlton
William

E.

Constance M. Soja
John C. Steinmetz

Shirley K. Egan

Howard

Hartnett
Harry G. Lee

Peter B. Stifel
Henry W. Theisen

Amy

Thomas

R.

Phillip

P.

McCune

E.

Whiteley

Proujansky
Trustees Emeritus

Harry A. Leffingwell
Robert M. Linsley
Samuel T Pees
Edward B. Picou, Jr.
John Pojeta, Jr.
James E. Sorauf

Raymond Van Houtte
William

P. S.

Ventress

BULLETINS OF AMERICAN PALEONTOLOGY
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3u(Qtmsqf
"fApwrxcan
tvlogs)
Begun

NUMBER

in

1895

LihjHAR

357

DECEMBER

31, 1999

Ui

A

Paleobiotic Survey of Caribbean Faunas

from the Neogene of the Isthmus of Panama
edited by

Laurel S. Collins and Anthony G. Coates

Panama Paleontology Project

Paleontological Research Institution

1259 Trumansburg Road
New York, 14850 U.S.A.

Ithaca,


ISSN 0007-5779

ISBN 0-87710-449-2
Librury of Congress Calalog Card Number: 99-76998

This publication

is

supported in part

by a Corporate Membership from

Exxon Exploration Company

This publication
to

is

The Program

contribution

in Tropical

number 9

Biology

at

Florida International University.

Note: Beginning with issue number 356, Bulletins of American Paleontology is no longer designating
volumes. The journal will continue to publish approximately 2-4 issues per year, each of which will continue
to

be individually numbered.

Printed

in the

United States of America

Allen Press, Inc.

Lawrence,

KS 66044

U.S.A.


CONTENTS
Page
Introduction

Laurel

Collins and

S.

Anthony G. Coates

PART
Chapter

5

1

.

STRATIGRAPHY AND PALEOENVIRONMENT

I

Lithostratigraphy of the

Neogene

strata

of the Caribbean coast from Limon. Costa Rica, to Colon,

Panama

Anthony G. Coates

17

Appendix to Chapter
Newest Biostratigraphy
Marie-Pierre Aubry and William A. Berggren
1

38

Chapter 2

Neogene calcareous nannofossil biostratigraphy of
Laurel M. Bybell

the

Caribbean coast of Panama and Costa Rica
41

Chapter 3

Neogene

Mathew

planktic foraminiferal biochronology of the southern Central

American isthmus

A. Cotton

61

Chapter 4

A

paleoenvironmenlal analysis of the Neogene of Caribbean Panama and Costa Rica using several phyla

Laurel S, Collins. Orangel Aguilera. Pamela

F.

Borne and Stephen D. Cairns

PART

2.

81

PALEOBIOTIC SURVEY

Chapter 5

The Miocene

to

Recent diversity of Caribbean benthic foraminifera from the Central American isthmus

Laurel S. Collins

91

Chapter 6
Stratigraphic distribution of

Neogene Caribbean azooxanthellate

corals (Scleractinia and Stylasteridae)

Stephen D. Cairns

109

Chapter 7
in the Limon Group of Costa Rica
Budd. Kenneth G. Johnson, Thomas A. Stemann and Bridget H. Tompkins

Pliocene to Pleistocene reef coral assemblages

Ann

F.

119

Chapter 8

Neogene cheilostome Bryozoa of

tropical America: Comparison and contrast between the Central American isthmus
(Panama, Costa Rica) and the North-Central Caribbean (Dominican Republic)
Alan H. Cheetham, Jeremy B.C. Jackson. JoAnn Sanner and Yira Ventocilla

159

Chapter 9
Diversity and assemblages of Neogene Caribbean MoUusca of lower Central America
Jeremy B.C. Jackson, Jonathan A. Todd, Helena Fortunato and Peter Jung

193

Chapter 10

Neogene-Quatemary Ostracoda and paleoenvironments of
Pamela E Borne. Thomas M. Cronin and Joseph E. Hazel
Chapter

the

Limon

Basin, Costa Rica, and Bocas del Toro Basin,

Panama
231

1

Bathymetric distribution of Miocene

to Pleistocene

Orangel Aguilera and Dione Rodrigues de Aguilera

Caribbean teleostean fishes from the coast of Panama and Costa Rica

25

Chapter 12

A

data model for the

Karl W.

Kaufmann

Appendix

Panama Paleontology

Project

271

A

Maps
Anthony G. Coates

287

Appendix B
Stratigraphic sections

Anthony G. Coates

299

Index

349



INTRODUCTION

Laurel

S.

Collins

Department of Earth Sciences
Florida International University

Miami, Florida 33199, U.S.A.

AND

Anthony G. Coaxes
Smithsonian Institution
Smithsonian Tropical Research Institute
Washington, D.C. 20560-0580, U.S.A.

A

fundamental question

in biology

concerns the ex-

which populations and communities are affected by geographic isolation and environmental change,
a full comprehension of which must include understanding environmental conditions and biodiversity of
the past. The main research goal of the project that
produced this volume is an assessment of patterns of
changing marine invertebrate faunas of tropical Amertent to

~ 10 million years, for the purpose of
determining the impacts of environmental change and
genetic isolation on large-scale evolution and ecologic
systems. This multitaxonomic paleobiotic survey takes
ica over the last

advantage of a "natural experiment," the Miocene
constriction of the Caribbean-Pacific seaway and the
Pliocene emergence of the Isthmus of Panama, which
resulted in biotic isolation and changes in oceanic conditions

on opposite

sides.

We

initially

concentrated on

southern Central America because the bulk of evi-

dence indicates that this is where final isolation of the
tropical Atlantic and Pacific occurred. In this region,
the biological effects are likely to have been most pronounced and directly relatable to the physical, sedimentary record of isthmian emergence. A remarkably
complete record of these events is preserved in Neogene sediments of the region, including abundant, diverse and well-preserved macrofaunas and microfaunas. In addition, the Recent lies at the end of this time
range, providing extant collections for comparative anatomical and molecular studies.
The Panama Paleontology Project (PPP), was initiated to

make

the systematic, regional fossil collections

and fine-scaled chronologic framework necessary for
these investigations. All geographic, stratigraphic, and
taxonomic data are integrated in the PPP Database.
From these and and other data, paleontologists are
documenting biodiversity, biogeographic change, and
the origination and extinction of tropical American or-

ganisms, and relating these to patterns of environmen-

and tectonic changes.

tal

THE PANAMA PALEONTOLOGY PROJECT
The PPP

is

a geographically, chronologically and

logistically large-scaled

endeavor

that has taken con-

The advantage of
can take a multitaxon-

siderable time and effort to develop.
a coordinated project

is

that

it

omic, integrated approach to investigating evolutionary and environmental processes. The project currently
involves 35 scientists from 20 institutions in 7 countries (see the

"collinsl/),

ing

its

PPP

internet site at />
although

many more have participated dur1). The PPP organizes expe-

existence (Table

and measure geologic secprepares and curates macrofossils and
microfossils from standardized, random samples; assigns ages using microfossils, paleomagnetics and raditions to collect fossils

tions;

diometric dating; and reconstructs paleoenvironments

based on microfossil and macrofossil assemblages,
sedimentology, and stable isotopes. The maintenance
and development of the PPP Database and the extensive collections support longer term taxonomic, systematic, ecologic and evolutionary studies. Below we
describe the organization of the project.
This formal collaboration began in 1986 with a reconnaissance survey of the Neogene geology of Panama by Jeremy Jackson and Anthony Coates. The objective was to determine whether the fossils were sufficiently abundant, both stratigraphically and geographically, for research on the evolutionary and
ecological consequences of the rise of the Isthmus of
Panama. In 1987, Peter Jung and Laurel Collins joined
the project,

which became known

as the

Panama Pa-

leontology Project. This group, with the addition of

Ann Budd

in

1993, formed a steering committee to

plan collecting expeditions, seek funds, devise guide-


Bulletin 357

Table

ama

1.

— Members*. Held

parlicipants and assistants in the Pan-

Table

1.

— Continued.

Paleontology Project. 1986-1999.

Nehm*
Neumann

Ross

Committee

Steering

Hermatypic

my

corals, taxono-

U.S.A.

database

Anthony Coates*

Stratigraphy

U.S.A.

Laurel Collins*

PPP

U.S.A.

Database, benthic fora-

minfera, stable isotopes

Jeremy Jackson*

Scientific coordination,

Peter Jung*

Mollusks

U.S.A.

bryozoans, mollusks
Switzerland

Romania

Noda
Jorge Obando*
Luis Obando

Mollusks
Regional sedimentation
Regional stratigraphy and
geology

Japan
Costa Rica
Costa Rica

Marta Ordofiez

Foraminifera. biostratigraphy

Ecuador

Dawn

Peterson*
Stephen Schellenberg
Jay Schneider*

Ostracodes

John Sutter

Radiometric dating (Ar39/
40)
Cyclostome bryozoans
Stable isotopes of mollusks

Polystirid gastropods

U.S.A.
U.S.A.
U.S.A.
U.S.A.

Glycymerid bivalves

Switzerland

Palynology

Ecuador
Canada

Teresita Aguilar

Mollusks

Costa Rica

Paul Taylor*
Jane Terranes*
Jon Todd*

Orangel Aguilera*

Teleost fishes

Venezuela

Pascal Tschudin*

Laurie Anderson*

Corbulid bivalves

U.S.A.

Italo

Marie-Pierre Aubry*

Calcareous nannofossils,

France

Jijun

Guillermo Barbosa
Peter Baumgartner
William Berggren*

Regional geology

Costa Rica

Tectonics

Switzerland

Planktic foraminifera,

U.S.A.

Scientists

Zambrano
Zhang*

biochronology

Pamela Borne*

Ostracodes

U.S.A.

Laurel Bybell*

Calcareous nannofossils.

U.S.A.

biochronology

Alan Cheetham*
Stephen Cairns*

Cheilostome bryozoans
Ahermatypic corals

U.S.A.

Mathew Cotton*

Planktic foraminifera.

U.S.A.

U.S.A.

biochronology
Gastropods, molecular

Thomas Cronin*
John Dawson*
Stephen Donovan*

Ostracodes

Harry Dowsett*

U.S.A.

biology

U.S.A.

Ahermatypic corals

U.S.A.

Echinoids

England

Planktic foraminifera,

U.S.A.

paleoceanography

Helena Fortunato*

Strombiniid gastropods.

Panama

taxonomy database

Andrew Gale
Dana Geary*

Facies analysis

England

Strombid gastopods, stable

U.S.A.

Thor Hansen*

Mollusks

isotopes

Antoine Heitz

MoUusk

U.S.A.
curation and

France

Nelson Jimenez

Calcareous nannofossils

Ecuador

Kenneth Johnson*

Hermatypic

U.S.A.

analysis

Karl

Kaufmann*

PPP Database

U.S.A.

Patricia Kellcy*

Mollusks

U.S.A.

Susan Kidwell

Stratigraphy

U.S.A.

Michael Kunk

Radiometric dating {Ar39/

U.S.A.

40)

Lorena Lanza
Peter

Marko*

Planktic foraminifera,

England
U.S.A.

England

Research Assistants

Dione R. de Aguilera

Sample processing

Raul Brito

Student assistant

Venezuela
Ecuador

Brown

Regional geology

Nicaragua

Arcid bivalves, molecular

U.S.A.

for fishes

Field assistant

Panama

Martin Brunner

Student assistant

Switzerland

Magnolia Calderon

Sample processing

Rogelio Cansari

Field guide

Daniel Castaiieda

Field guide

Panama

Panama
Panama
Panama

Eric

Sebastian Castillo

Boatman

Janet Coates

Field logistics

U.S.A.

John-Mark Coates
Chena Cooke
Luis Cruz
James Diaz

Field assistant

U.S.A.

Field logistics

Panama
Panama

Student assistant

U.S.A.

Beatrice Ferrenbach

Field logistics

Lucien Ferrenbach
Xenia Guerra

Field logistics

Research assistant

Panama
Panama
Panama

Karl Hansen

Photographer

U.S.A.

Huichan Lin
Dorotheo Machado

Nannofossil processing

U.S.A.

Field assistant

Panama

Claudia Mora

Field assistant

Costa Rica

Angelica Mufioz

Field guide

Nicaragua

Agustm Paladines
Rene Panchaud

Student assistant

Ecuador

Field assistant, collections

Switzerland

Field assistant

Betzabeth Rios

manager
Sample processing

Panama

Fabricio Sierra

Student assistant

Ecuador

Omar

taxonomy
corals, data

Sr isotopes of reef corals
Cardiid bivalves

biochronology

biochronology

Timothy Collins*

U.S.A.

Dinoflagellates

Hiroshi

Ann Budd*

Marginellid gastropods

Florin

Field assistant

Panama

Bridget Tompkins

Student assistant

U.S.A.

Sophia Vclotti

Sample processing
Sample processing

Panama
Panama

Sugasti

Yira Ventocilla

Jamie Wineberg
David West

Student assistant

U.S.A.

Research vessel. Captain

Panama

biology

Donald McNeill*

Magnelostratigraphy

U.S.A.

Jorge Mideros

Petroleum geologist

Ecuador

Daniel Miller*

Muricid gastropods, mollusk

U.S.A.

taxonomy

Simon Mitchell

Stratigraphy and

Jamaica

sedimentology

lines for preparing collections, coordinate studies of

taxonomic groups, and organize joint publications.
U. S. Geological Survey paleontologists Bybell (calcareous nannoplankton), Dowsett (planktic foraminifera)

Richard Mooi*

Clypeasteroid echinoderms

U.S.A.

Galo Montenegro

Petroleum geologist

Ecuador

and Cronin (ostracodes), together with graduate

student Cotton (planktic foraminifera), contributed the

PPP's biostratigraphic foundation. The question of an


Introduction: Collins and Coates

adequate

Coates

fossil

collections are

Fossil

when

record was answered affirmatively by

most useful

researchers

to

they reside at centralized locations.

An

agree-

ment was signed between

the Smithsonian Tropical
Research Institute (STRI, the home institution of Jackson and Coates) and the Naturhistorisches Museum
Basel (Jung's institution) that all of the mollusks and
less abundant groups (crustaceans, echinoderms, brachiopods) would be prepared and accessioned in Basel,
and that all bryozoans, corals, foraminifera, calcareous
nannofossils, and ostracodes would be permanently

housed, after study by the appropriate specialists,
the U.S. National

Museum

at

of Natural History, Wash-

ington D.C.

By

1990, growth in the volume and completeness

new procedures and

of the collections required

lapping) research groups, a division reflected in the
parts of this

volume. The

first

group establishes a

chronologic and paleoenvironmental framework for

each region, and the second builds its paleobiological
studies upon this framework. The stratigraphic part of
first group consists of Coates, Aubry (calcareous
nannofossil biostratigraphy), Berggren and Zhang

the

(planktic foraminiferal biostratigraphy), and

McNeill

(paleomagnetics). Within the constraints of the physical stratigraphy, the biostratigraphers use the evolu-

tionary and paleoceanographic history of microfossils
to establish a high-resolution

graphic sections.
refined

chronology for

The ages of many

strati-

sections are further

by applying the chronology of paleomagnetic

reversals. Paleoenvironmental determinations (Chapter

4) are based on the

modem

tunato, Jackson, Marko, Miller, Nehm, Schneider,
Tshudin and Todd. Additional paleobiological research
includes that of Aguilera (otoliths). Borne and Peterson (ostracodes), Donovan and Mooi (echinoderms),
Budd, Johnson, and Stemann (reef corals). Cairns and
Dawson (ahermatypic corals), Cheetham, Jackson and
Taylor (bryozoans), and Collins (benthic foraminifera).
In addition to the PPP Database of information about
locality, stratigraphy, age, and taxon occurrence Kaufmann and Collins), Budd designed and implemented a
taxonomic database (Nmita) that contains information
such as photographic and scanning electron micrograph images on PPP and other tropical American pa(

leontological collections.

To obtain comparative Caribbean and Eastern Paexpeditions were undertaken more or

a

broadened taxonomic expertise. To census the macrofauna, full-time "factories" at STRI and Basel were
established for processing bulk sediment samples taken at shell-rich sites. The data on locality, stratigraphy,
age, sample processing, and identified taxa began to
be tracked in the PPP Database designed by Kaufmann
(Chapter 12) and Collins. New colleagues began to
study PPP bryozoans (Cheetham), mollusks (Geary,
Anderson, Schneider), corals (Cairns), and regional
sedimentation (Obando).
Since 1993, the PPP has developed into two (over-

two

sisthmian distributions are being studied with morphometric and/or molecular techniques by Anderson, For-

et al. in 1992.

cific collections,

less

equally to both sides of the southern Central

American isthmus during
(Table

2). In the

Peterson),

otoliths

(Aguilera),

ahermatypic

The second PPP research group includes members
conducting macrofossil and microfossil studies of evolution, biogeography and ecology. For the mollusks,
by

most diverse group, Jackson coordinates the
lists of genera and subgenera that
have been taxonomically standardized by Heitz, Jung
and Todd. Several molluscan clades with modern tranfar the

analysis of faunal

years of the

PPP

and the Bocas del Toro and Colon regions of Panama.
Many new formations were described, dated, and collected in detail to yield unparalleled collections of fos-

from different stratigraphic levels and facies. The

Caribbean stratigraphy and collections form the focus
of this volume.
In contrast to the Caribbean coast, the Pacific coast
from the Darien (eastern Panama) to Nicaragua has
sils

yielded sequences that are less continuous chronolog-

and not comparable in age, environment, and
taxonomic diversity with the Caribbean faunas. The
most important Pacific sequences are in the Darien
(Middle-Upper Miocene) and the Burica Peninsula
(Pliocene-Lower Pleistocene). Recently, to compensate
for this inadequate record, the PPP began fieldwork in
Ecuador, where richly fossiliferous, Neogene sequences extend from the coast to the Andean foothills of the
Borbon and Manabi basins. We hope to suimnarize all
these sequences in a companion volume on the Neogene of the Pacific coast.
ically

ecology of primarily ben-

corals (Cairns), and sedimentology.

first five

cused on the relatively complete and fossiliferous Caribbean sections of the Limon region of Costa Rica,

BIODIVERSITY

thic foraminifera (Collins), but also ostracodes (Borne,

Cronin,

the

next six years, most expeditions fo-

AND SCALE

The large scale of the Panama Paleontology Project
main characteristic that differentiates it from other field-based paleontological projects. To study the
is

the

and distribution of taxa within a tropical
ocean basin over —10 million years at a relatively fine
diversity

chronological scale requires years of constructing a regional stratigraphy and collecting and identifying fossils.

For most taxonomic groups, collections have only

recently

become

sufficient to calculate biodiversity re-

Bulletin 357

Table

2— PPP expeditions,

1986-1999.


Introduction: Collins and Coates

Table

3.

— Ages of Caribbean

stratigraphic units

PPP, based on the time scale of Berggren el

Formation

al.

(

examined by

1995).

the


Bulletin 357

10

Cayo Agua

Gatun-

Escu(do de Veraguas

Bastimentos-

Rio Banano-

Swan CaySharkHole

Lomas

del

Mar-

—

Lomas

—

Point

(del

Mar-

—

I

I

1

1

—

I

0.3

0.2

0.1

0.4

0.5

0.6

0.7

0.0

Distances
Text-figure

1.

0.3

0.2

0.1

—

I

1

1

1

1

I

co

0,4

0.5

0.6

0.7

Distances

—

Cluster analysis (complete linkage method) of the

Text-figure 2.

—Cluster analysis (complete linkage method) of

the

presence/absence of species of reef corals, genera of teleost fishes,

presence/absence of taxa

and genera to subgenera of mollusks in the Gatun Formation (Panama Canal Basin), the Fish Hole section of Bastimentos Island (Bocas del Toro Basin), the Swan Cay Formation (Bocas del Toro Ba-

and Shark Hole Point formations of the Bocas del Toro Basin, and
the Rio Banano Formation and Lomas del Mar Member of the Moin
Formation in the Limon Basin. Included in the analysis are species

Member of the Moin Formation (Limon

of benthic foraminifera, azooxanthellate corals, cheilostome bryo-

sin),

and the Lomas del Mar

Assemblages from the same basin
are more similar than assemblages from the same age or bathymetry.
Basin). Distances are Euclidean.

in the

Cayo Agua, Escudo de Veraguas,

zoans, and ostracodes, genera of teleost fishes, and genera to sub-

genera of mollusks. Distances are Euclidean.

Age and environment

have approximately equal influences on the similarity of assemblages.

Ma, and Lomas

del

Mar

is

1.9-1.5

Ma. Units do

not cluster by paleobathymetry, either: Bastimentos

and Lomas del Mar are middle

Cay

is

middle

neritic,

shallowest outer neritic with transported

shows the

graphic units using

all

to the bathyal units. The older, shallower Gatun
Formation falls between the old, deep units in the
upper cluster and the lower cluster of shallower-

similarity of five strati-

taxa except reef corals.

Age

and environment affect the similarity of the units'
faunal assemblages about equally. Although the Rio
Banano and Cayo Agua formations are most alike
in environment (inner-middle neritic), the former is
linked first to an outer neritic unit of a comparable,
Early-middle Pliocene age, the Shark Hole Point
Formation. However, the Escudo de Veraguas Formation, which is Late Pliocene and mixed middle
to outer neritic, is most similar to the first two units,
suggesting that environment has a stronger influence in this grouping than age. The unit that is most
different in both environment and age, the reefal,
latest

Point and

neritic material.

Text-figure 2

Pliocene to earliest Pleistocene

Mar Member,

Lomas

del

Early Pliocene and Pleistocene Shark Hole
Swan Cay formations, are most similar

neritic.

and Swan

water. Pliocene-earliest Pleistocene units.

GatunShark Hole PointUscari-

Nancy PointChagres-

Swan CayLomas

del

Mar-

Rio Banano-

Escudo de Veraguas

Cayo Agua-

has the most different faunal assem-

1

1

1

1

1

1
1

I

blage.

Text-figure 3

0.0
is

of assemblages more than age, although age and
environment are somewhat correlated because of
ity

Neogene uplift of the Bocas del
Toro and Limon basins. There are two main clusters. In the upper one, the Late Miocene, bathyal
Uscari, Nancy Point and Chagres formations are
most similar. The next shallowest units, the outer

0.3

0.5

0.6

0.7

Distances
Text-figure

suggests that environment influences the similar-

the progressive

0.2

an analysis of ten stratigraphic units

using only benthic foraminifera, fish and mollusks.
It

0.1

0.4

3.

—Cluster

presence/absence of taxa

analysis (complete linkage method) of the
in

the

Gatun and Chagres formations of

Nancy Point, Swan
Agua formations of the Bocas
del Toro Basin: and the Uscari Formation, Lomas del Mar Member
of the Moin Formation, and Rio Banano Formation of the Limon
the

Panama Canal

Basin; the Shark Hole Point,

Cay, Escudo de Veraguas, and Cayo

Basin. Included in the analysis are species of benthic foraminifera,

genera of teleost fishes, and genera to subgenera of mollusks. Distances are Euclidean. Environment seems to influence the similarity

of assemblages more than age.


Introduction: Collins and Coates

We

conclude from these exploratory analyses that
there are strong age, paleoenvironment, and basin effects on the similarity of PPP assemblages. Age reflects

evolutionary changes but

is

somewhat

combined

tions are

for an

environmental change

set

overview of larger-scale

within the region's tecton-

ic history.

correlated

with paleoenvironment because of regional tectonic
uplift through time. Similarities of assemblages from
result from ecological asand the basinal effect reflects more localized conditions. Analyses of this sort begin to disentangle evolutionary and ecological faunal changes for
the ultimate purpose of isolating evolutionary events.
These analyses are of multiple, higher-level taxa recorded as presence/absence in stratigraphic units, and
future analyses using relative abundances and a finerscaled chronology will undoubtedly reveal other trends
in evolution and ecology.

same paleoenvironments

the

11

sociations,

CONTENT OF CHAPTERS

Part 2, Paleobiotic Survey, includes seven chapters
that report the distribution of species or genera at

PPP

sites, and address topics such as faunal and paleoen-

vironmental change through time.

sions of Chapters 5 to 12 are

Chapter

Some

Collins combines fossil and

5.

of the conclu-

summarized

as follows;

modern

distri-

butions of species of Caribbean benthic foraminifera

from Panama and Costa Rica and shows that their
diversity has doubled from the Late Miocene to Recent, through the time of seaway constriction, complete closure, and afterward. The proportion of taxa
associated with carbonate shoals and reefs increased
during this time, which agrees with the trend of increasing speciation in these ecologically restricted

The volume

is

divided into two parts. Part

1,

Stra-

tigraphy and Paleoenvironment, consists of four chap-

on the formal lithostratigraphy, biostratigraphy,
geochronology, and paleoenvironments of sediments
from the Panama Canal, Bocas del Toro, and Limon

ters

basins.

The chapters

are

summarized

as follows:

Coates places the physical stratigraphy of
Neogene sediments of Caribbean Panama and Costa
Rica within a regional tectonic framework, incor-

Chapter

1.

porating the units defined in Coates et

al.

(1992)

and creating several new ones. In Appendix 1 of
Chapter 1, Aubry and Berggren give the latest biostratigraphic data and chronological correlation of
the

new

Chapter

2.

sections.

Bybell presents calcareous nannofossil data

collected until 1991, and discusses their application

geochronology of the formations described by
Coates et al. (1992). Her research laid the foundation upon which the later biochronology was built.
Chapter 3. Cotton presents data from planktic foraminifera collected before 1993 and combines it with
the nannofossil data for refined age estimates of forto the

mations.

He

correlates the Central

American

for-

mations with other tropical to subtropical American
formations from southeastern Virginia to Ecuador.

Chapter 4. Collins, Aguilera, Borne and Cairns combine environmental assignments from four different
phyla (benthic foraminifera, teleost fishes, ostracodes, and ahermatypic corals, respectively) for

most stratigraphic units. The results among taxa are
remarkably congruent, considering the different life
modes of the organisms (e.g., benthic versus nektonic; feeding at versus above the subtratum), as
well as variations in technical and analytical ap-

proach.

The paleoenvironments

for individual sec-

The

changes apparently occurred

Recent rather than the middle
Pliocene, suggesting that complete seaway closure
had little effect.
Chapter 6. Cairns reports the stratigraphic ranges of
142 Caribbean azooxanthellate coral species, 101 of
taxa.

largest faunal

in the Pleistocene to

which

are extant.

The data suggest

that the highest

origination rate occurred in the Middle to Late

Mio-

cene and the highest extinction rate occurred in the
Late Pliocene. Neither of these evolutionary pulses
occurred near the time of complete seaway closure.
Chapter 7. Budd, Johnson, Stemann, and Tompkins describe the distribution of reef coral species from the
Limon Basin, and identify different periods of faunal change that occurred at various Caribbean localities

during the Late Pliocene to Pleistocene.

Cheetham, Jackson, Sanner, and Ventocilla
contrast assemblages of cheilostome bryozoans
from both sides of the Central American isthmus
with those of the Dominican Republic in an analytical comparison of Caribbean and Pacific faunas. An
unexpected result is that the complete closure of the
isthmian seaway apparently had relatively little evolutionary effect. The authors also find a Middle

Chapter

8.

Miocene

to Pleistocene decline in the diversity of

erect species, possibly associated with their

growth

on decreasingly available substrata such as seagrass.
Chapter 9. Jackson, Todd, Fortunato and Jung control
for sampling and taxonomic biases in an enormous
dataset of Neogene molluscan genera to subgenera
from Caribbean Panama and Costa Rica. Local molluscan diversity varied more than six-fold, and either increased or

remained constant from the Mio-

cene to Recent. Previous studies which identified a
decline in Pliocene Caribbean molluscan diversity

Bulletin 357

12

and associated it with seaway closure were based on
inadequate sampling of the faunas.
Chapter 10. Borne, Cronin and Hazel use assemblages
of ostracodes from the Limon and Bocas del Toro

mations, with age ranges for single samples varying
between approximately 100,000 years and 1.5 million years.
3.

species suggest that cold, upwelling currents im-

low Middle Miocene basin until deepening ~6 Ma
caused an inflow of deep. Pacific water. The Bocas
del Toro and Limon basins differed in sediment
source, isobathyal microfaunas, and stable isotopes.

pinged on the Late Pliocene to Early Pleistocene

They were

Central American shelf.

of

basins to identify lagoon, carbonate platform, re-

and outer shelf

stricted nearshore,
facies.

The

distributions and

to

upper slope

morphology of several

Chapter 1 1 Aguilera and Aguilera describe teleost fish
assemblages at the genus level from otoliths, and
infer bathymetries by comparison to living representatives of the genera. Several genera, found living only in the Indo- or Western Pacific, show that
relict elements of Tethyan faunas persisted in the
Caribbean until at least the Late Pliocene.
.

4.

isthmian seaway, although an evolutionary turnover

database of information on stratigraphy, geography,

chronology, paleoenvironment, and faunal occur-

the latest Pliocene to Early Pleistocene for the mol-

plains

in reef corals did

Kaufmann presents a data model that exthe way in which the elements of the PPP

12.

function as a whole, as well as the working of the

rence. For

complex

projects, data

ify the relationships

models help

lusks, perhaps

clar-

ently had relatively

5.

are the following:

There exists along the Caribbean
coast of Panama and Costa Rica a series of exposures of richly fossiliferous, Neogene, shallow-water sediments which, when placed in stratigraphic
succession, cover the late Middle Miocene to Early
Stratigraphy.

Pleistocene interval.

Chronology. The

fossil

collections can be dated

biostratigraphically and paleomagnetically with a

precision that

is

relatively fine for land-based for-

little

evolutionary effect on

cheilostome bryozoans.

Biodiversity. From Late Miocene to Recent time,
the diversity of molluscan genera either increased

or remained constant and that of species of benthic
foraminifera increased.

SUMMARY
For the Panama Paleontology Project, the whole is
much greater than the sum of the parts. Basing studies
of multiple, higher-level taxa on the same, well-dated
set of samples has provided many possibilities for integrated research. A few of the conclusions the PPP
can make thus far, based on the Caribbean collections,

because of increased northern hemi-

sphere glaciation. Complete seaway closure appar-

of the many, diverse parts.

Appendices. Coates locates all PPP collecting sites
used in this volume, plotting them on maps in Appendix A. Each site is represented by a unique PPP
number. In Appendix B, he places the sites stratigraphically in a series of 39 detailed sections.

2.

similar in their back-arc setting, histories

and sedimentary sequences of bathyal
Miocene mudstones, neritic Pliocene siltstones/
sandstones, and lower Pleistocene coral reefs.

Seaway closure. To date, research on PPP collections shows no strong evolutionary response to the
complete closure —3.5 Ma of the Central American
uplift,

occur sometime between 4 and 1
Ma. Whereas the largest pulses of origination in the
Neogene occurred for azooxanthellate corals and
benthic foraminifera in the Middle and Late Miocene, during seaway constriction, they occurred in

Chapter

1.

Environments. The Panama Canal Basin was a shal-

From

the

Middle Miocene

to the Pleistocene, the diversity of erect cheilostome

bryozoans declined.

ACKNOWLEDGMENTS
Grants from the Biotic Surveys and Inventories Pro-

gram of the National Science Foundation (grant numbers BSR90-06523, DEB-9300905, DEB-9696123,
DEB-9705289) provided the means to build the PPP

Database, prepare large numbers of samples, track fossil

collections,

and assign ages and paleoenvironments.

The National Geographic Society has consistently
funded PPP fieldwork in Panama, Costa Rica, Nicaragua and Ecuador. The Smithsonian Institution, STRl,
Swiss National Science Foundation, and Naturhistorisches Museum Basel have also funded fieldwork and
the preparation of collections. This is contribution
number 10 to The Program in Tropical Biology at
Florida International University.


Introduction: Collins and Coates

13

REFERENCES CITED
Berggren, W.A., Kent, D.V., Flynn,
1985.

J.J.,

and Van Couvering,

Cenozoic geochronology. Geological Society of America
Bulletin, vol. 96, pp. 1407-1418.

Geological Society of America Special Paper, no. 295.

Coates, A.G., Jackson, J.B.C., Collins, L.S., Cronin, T.M.,
sett, H.J.,

Bybell, L., Jung, P.,

Dow-

and Obando, J.A.

Closure of the Isthmus of Panama: the near-shore marine
record of western
ciety of

America

Panama and Costa

Timing and

Rica. Geological So-

Bulletin, vol. 104, pp.

Collins, L.S., Coates, A.G., Jackson, J. B.C.,

1995.

Toro basins: Caribbean effects of Cocos Ridge subin Geologic and tectonic development of the Ca-

duction?

Berggren, W.A., Kent, D.V., Swisher, C.C, and Aubry, M.-P.
1995.
A revised Cenozoic geochronology and chronostratigraphy. SEPM Special Publication, no. 54, pp. 129-212.

1996.

del

J.A.

rates of

emergence of

814-828.

and Obando, J.A.
Limon and Bocas

the

ribbean Plate

Mann.

eJ.. pp.

Boundary

in

southern Central America.
P.

263-289.

Jackson, J.B.C., Jung, P., Coates, A.G., and Collins, L.S.
Diversity and extinction of tropical American mollusks
1992.
and emergence of the Isthmus of Panama. Science, vol.
260, pp. 1624-1626.
McNeill, D.F., Coates, A.G., Budd, A.F., and Borne. P.P.
1999.

Integrated paleontological and paleomagnetic stratigraphy

of the upper Neogene deposits around Limon, Costa Rica:

A

coastal

emergence record of the Central American

mus. Geological Society of America Bulletin

Isth-

(in press).



PART

1

STRATIGRAPHY AND PALEOENVIRONMENT



CHAPTER

1

LITHOSTRATIGRAPHY OF THE NEOCENE STRATA OF THE CARIBBEAN COAST
FROM LIMON, COSTA RICA, TO COLON, PANAMA
Anthony G. Coates
Smithsonian Institution
Smithsonian Tropical Research Institute
Washington, D.C. 20560-0580, U.S.A.

INTRODUCTION
The Central American isthmus

ican

Mann
Plates,

et al.. 1990).

lies at the intersec1;

Burke

et al,

The North and South Amer-

with relative westerly and west-north-

westerly motions, respectively, override two large oce-

Cocos and Nazca, with northThe

anic Pacific plates, the

easterly or easterly relative motions, respectively.

two sets of plates has formed, since
the Cretaceous, a major zone of subduction along the
western margin of the Americas, a segment of which
constitutes the Central American volcanic arc.
The southern Central American isthmus consists primarily of igneous and sedimentary rocks of oceanic
crustal composition, generated by the Central American volcanic arc. In this chapter, I focus on the stracollision of these

tigraphy of three important sedimentary basins that
flank the

fig.

2),

magmatic

arc

on the Caribbean side (Text-

namely, the southern Limon Basin in Costa

Panama Canal basins
Panama. These basins are dominated by volcaniclastic sediments, commonly with foraminiferal and
Rica, and the Bocas del Toro and
in

They also contain important
Miocene through Pleistocene coral reefs, as well as a
nannofossil microfaunas.

and diverse molluscan, bryozoan, fish
and coral assemblages at many stratigraphic

series of rich
(otoliths),

levels. In this chapter,

I

present a revision of the formal

stratigraphy of the sediments in
cur,

(Kaneps, 1970; Berggren and Hollister,

1973, 1974; Keigwin, 1978, 1982).

tion of six tectonic plates (Text-fig.

1984;

Ma

about 3

which the faunas oc-

including the definition of several

new formations

and their biochronology (Appendix 1 this chapter).
Also included are 1 1 maps and detailed insets, showing the location of all samples (Appendix A, this volume), and the computer-drawn logs of 39 sections
measured across the three basins that show the stratigraphic relations of all the samples (Appendix B, this
volume). The locations of the measured sections are

shown in Text-figure 2.

The Isthmus of Panama was the last portion of
Central American isthmus to emerge (Coates et

the
al.,

1992; Coates and Obando, 1996), closing the marine

connections between the Caribbean and the Pacific

The Panama Pa-

leontology Project (PPP) set out to look for extensive

upper Neogene fossiliferous sedimentary sequences in
this region on the assumption that the sedimentary record here would track most closely the marine environmental and ecological changes caused by the emer-

gence of the Isthmus.

The

stratigraphic sections

and faunal samples ana-

lyzed in this volume are located in back-arc basins
(e.g.,

southern

Limon Basin)

or in marginal aprons

Bocas del Toro and Panama Canal Basins) derived from the Caribbean side of the Central American
volcanic arc, the structure of which is shown in cross
section in Text-figure 3. Although we originally undertook field expeditions to both Pacific fore-arc and
Caribbean back-arc basins, the Caribbean sequences
yielded more complete stratigraphic sections and more
abundant and diverse faunal assemblages. This is
largely due to erosion of many younger sequences on
the tectonically active Pacific coast. Older sediments
have been subducted or obducted onto the overlying
plate and are either highly deformed or lost (Text-fig.
3). By contrast, on the passive Caribbean margin, the
southern Limon, Bocas del Toro, and Panama Canal
basins (Text-fig. 2) have yielded numerous diverse and
abundant faunas. These sections are less deformed, and
(e.g.,

span a greater time interval than the Pacific sections.
For example, the Pacific Burica Peninsula fore-arc basin (Corrigan et al.,

more than 4000

<

m

1990; Coates et

al.,

1992) has

of sediments, ranging from about

Ma, whereas

Bocas del Toro
Group has about 1000 m, ranging from 8.5 to about
1 .5 Ma. In the region of the Talamanca Range (Textfig. 1 ) in Costa Rica, subduction of the Cocos Ridge
has elevated and structurally deformed both the inner
fore-arc Terraba Basin and the now inverted back-arc
3.5 to

1

.6

the Caribbean

Limon Basin (Kolarsky et al., 1995), as is
shown in Text-figure 3.
From 1986 to 1992, the PPP undertook a series of
reconnaissance field expeditions to explore a number
southern


Bulletin 357

18

Caribbean Sea

TERRANE

^^

Amenca

—

Text-figure \.
Map of Central America showing location of the older Maya, Chortis. Chorotega. and Choco geological terranes, and the
younger Panama microplate, picked out in thick dashed lines and gray stipple. The northern border of the Panama Microplate is called the
North Panama Deformed Belt. Also shown is the Talamanca Range (dash-dot stipple) and the volcanoes of the central magmatic arc (black
triangles

=

active,

open triangles =

inactive).

Caribbean Sea

\\f Colombia

Text-figure 2.

gray stipple).

— Map of Costa Rica and Panama showing

Numbers correspond

location of the .southern

to sections referred to in text

and

in

Appendix B.

Limon. Bocas

del Toro.

and Panama Canal Basins (dark


Lithostratigraphy; Coates

Text-figure

3.

— Schematic geologic

cross section from the

Osa Peninsula on

19

the Pacific coast to the southern

Limon Basin on the Caribbean
Government of

coast (see line on Text-fig. 2). Modified from "Hydrocarbon potential of Costa Rica". Ministry of Environment and Energy,

Costa Rica. 1996.

of the Neogene sedimentary fore- and back-arc basins
associated with the volcanic arc in southern Central

America. Basins were surveyed on the Pacific coast,
from the Nicoya Peninsula, northwestern Costa Rica,
to Darien, eastern Panama, and on the Caribbean coast,
from the northern part of the Limon Basin, Costa Rica,
to the Panama Canal Basin, Panama (Text-fig. 2). In a
preliminary review of the litho- and bio-stratigraphy,
Coates et al. (1992) established that a well-preserved
and diverse marine fossil record existed on both coasts,

containing nannofossils and planktic foraminifera capable of yielding a precise geochronology for the late

Neogene sediments.
In 1993, with a

view

more

to

detailed comparisons

of geologic history and evolutionary and ecological
patterns, the

PPP began

a

more extensive

series of field

expeditions. These focused particularly on the

com-

and richly fossiliferous sections of the Caribbean
coast, specifically in the southern Limon, Bocas del

Toro, and Panama Canal basins (Text-fig. 2) described
here. The northern part of the Limon Basin is not treated in this chapter because it is extensively covered by
Pleistocene volcanic deposits and did not yield abunplete

dantly fossiliferous sections.

Because the Miocene
the southern

to Pleistocene sediments of

Limon Basin

are relatively elevated and
complex, the physical stratigraphy of this
basin has been difficult to reconstruct (Text-fig. 3). The
stratigraphic sequence has been studied mostly along
structurally

rivers draining the foothills

and coastal plain northeast

of the Talamanca Range in the area around

(Map
as the

1

1 )

Limon

and, to a lesser extent, further south as far

Panamanian border (Map

10).

Many new,

ex-

by housing construction in the hills of the
western part of Limon and by commercial construction

porarily,

along Route 32 between Buenos Aires and
sets

A, B,

Map

In contrast to the sediments of the southern

Basin, the

Miocene

Limon

to Pleistocene deposits of the

Bo-

and are generally only gently folded. In the Bocas del
Toro Basin (Text-fig. 2), flat-lying sediments are extensively exposed along coastal sections of the islands
and peninsulas of the archipelago. Access to these sections is by sea and many can only be studied in relatively calm weather. Geological mapping and section
measuring were done using a 22-foot boat, but largescale bulk fossil sampling was carried out by PPP expeditions of 6 to 12 persons using the research vessels
Benjamin and Urraca of the Smithsonian Tropical Research Institute.

The Upper Miocene Panama Canal Basin

(Text-fig.

2) sediments are observed in roadside exposures

from

Sabanita to Colon, and in coastal exposures from Colon to Gobea, about 40 km to the west. (Map 1). The
Gatun Formation was studied in numerous, often temporary, construction sites along or near Route 3, between Sabanita and Colon, along the road to the Payardi Oil Refinery, between Gatun and Margarita, and
around the Gatun Dam (Map ). Also included in this
study are a few localities at the mouths of rivers along
the north coast of Panama, between the Valiente Peninsula, Bocas del Toro, and Gobea (Maps 2,3).
The following account of the lithostratigraphy of the
southern Limon, Bocas del Toro, and Panama Canal
basins revises that of Coates et al. (1992) and Bottazzi

1

et al. (1994),

were exposed during our

sequent

work, often only tem-

(In-

cas del Toro Basin are mostly exposed along the coast,

tensive and very fossiliferous Plio-Pleistocene sections
field

Limon

11).

field

adding new information obtained in subwork, including new formal stratigraphic


Bulletin 357

20

CANAL BASIN

(5)

(3)

(4)

RIo
IndJo

^Ul

I

'-

.!.

J.

'^-

NORTH COAST PANAMA

(Undated Upper Miocene)

(3)

(4)

(1)

Toro
Point

Miguel de

la

Borda

Calzones
River

Boca de
Boca de
Concepcion Concepcion
East

(2)

West

10

11

Margarita-

Gatun

T^^":^'?^

Cretaceous
Volcanics

Text-figure 4.

—Correlation of measured

refer to sections in

Appendix B.

this

sections from the Panama Canal Basin and along the north coast of Panama. Numbers
volume. Lithologic patterns correspond to the lilhologic key in Appendix B.

The temporal range and formal nomenclature of
summarized in Text-figures 4, 5, and 6. The bases for the
age assignments are discussed by Aubry and Berggren
Appendix 1, (this chapter).
units.

mann,

this

volume) which

the stratigraphic sequences in the three basins are

ternet

site

. edu/'collinsl/.

Five stratigraphic sections were measured in the
Basin: 4 along the north coast of Pan-

Panama Canal
ama, 17

in the

Bocas del Toro Basin, and 13

Limon Basin (Appendix
in

Appendix A,

each section

in

numbers also

PPP number on

the

maps

volume), and stratigraphically on
Appendix B, (this volume). These PPP

link

all files

in the

PPP Database (Kauf-

also available at the in-

is

Currently, a

the litho-

and biostratigraphy

to refine the geochro-

nology.

in the

(this

parentheses

paleomagnetic sampling project is being completed on
the stratotypes of the Limon (McNeill et al., in press)
and Bocas del Toro groups that will be integrated with

ACKNOWLEDGMENTS

B, this volume). Fossil col-

lections are located by their

in

Many
PPP

people have helped

me

in the field since the

Jeremy Jackson, Laurie Collins,

Peter Jung, and Ann Budd, my colleagues on the
Steering Committee of the PPP, have been my most
started in 1986.


Lithostratigraphy: Coates

MA

21

SWAN CAY
VALIENTE PENINSULA
South

BASTIMENTOS

ISLAND

Valiente

ISLAND

(15)

ESCUDO DE
VERAGUAS

-o

(22/23)

^

(24)

Fish Hole

Reef Member
Short Cut

North

S/vvvsr

COLON

Solarte

Cay

Valiente
(12)

(11)

ISLAND

(18)

(16)

North

Nispero

Point

Point

West

South

Bruno

North

Bluff

Coast

South
Coast

Piedra

Roja
Point

East

wi/v^
(19)

(17)

North PointTiburon Point

Finger

Piedra Roja
Point West

Island
(14)

CAYO AGUA ISLAND

Plantain

Cay

4
11

Tdfo

Tobabe

Point

Point

(13)
]r-v"f-^1

12
liillliii

l

j

Valiente
Point

16

»S' i1fi?n'

i

17

18

Text-figure 5.

—Correlation of measured sections

volume. Lilhologic patterns as for Text-figure

4.

in the

Bocas del Tore Basin. Numbers

in

parentheses refer to sections

in

Appendix B,

this


Bulletin 357

22

1

LIMON
(38)

(37)

(35)

Lomas del
Mar Mbr
Empalme

t^^-^r-':^'-^

Cangrejos
Creek

Mbr.

Pueblo Nuevo
.Cernetery

(29)
(30)

Buenos Aires
Mbr.

•Bomba

Chocolate
River

Agua

tv^>..«>Xvi

River

(33/34)

^3

Quitaria

o

Vizcaya
River

Bananito
River

Santa
Rjta

(28)

(27)

Sandbox

Carbon
Dos
Text-figure 6.

—Correlation of measured

sections in the southern Linion Basin.

volume. Lithologic patterns as for Text-figure

nannofossils,

Don McNeill,

planktic

identifying calcareous

foraminifera,

and taking and

processing paleomagnetic samples, respectively, have
also spent

much

time in the field and even more in the

laboratory, integrating the litho-, bio-, and magneto-

To them all I owe a special debt of gratthank Dana Geary, Tom Cronin, Susan Kidwell, John Sutter, Claudia Johnson, Erie Kauffman, Simon Mitchell, Orangel Aguilera, Jorge Obando, and

stratigraphy.
itude.

I

in

parentheses refer to sections

in

Appendix B,

this

4.

constant field companions. Marie-Pierre Aubry, Bill

Berggren, and

Numbers

River

Jon Todd,

all

of

whom

provided valuable insights into

on various occasions. Valuable assistance in measuring sections and collecting samples
was also provided by Laurie Andersen, Mairi Best,
Pam Borne, John-Mark Coates, Tim Collins, Mat Cotton, Helena Fortunate, Antoine Herz, Ken Johnson,
Rene Panchaud, Stephen Rhodes, Jay Schneider and
Tom Stemann. My thanks are also due to Sebastian
Castillo, who guided my boat for many years, and to
Beatrice and Lucien Ferrenbach for constant logistical
field interpretations


Lithostratigraphy: Coaxes

help and wonderful hospitality throughout this project.
I

am

also very grateful for very helpful reviews

from

Mann and

Joe Hartman. This chapter could not
have been completed without the extraordinary conPaul

tribution of
is

my

research assistant Xenia Guerra. She

responsible for the locality

maps and

the conversion

my field notes into computer-drawn sections that
comprise Appendices A and B, and for drawing all the
text-figures. She undertook the task of checking that
2531 samples were properly recorded on all sections
and maps. She has accompanied me in the field to
of

process samples, edited the manuscript, and ensured
that I was always equipped with the appropriate field
maps, for all of which I am especially grateful. Lastly,
my profound thanks to Janet Coates, my wife, who
acted as my field assistant on numerous occasions, tolerated long absences on other occasions, helped organize many expeditions, and generally supported PPP
activities in so

many

ways.-

GEOLOGICAL SETTING
The Central American isthmus forms
margin of the Caribbean and

complex

lies at the

the western

center of a

intersection of the Pacific, Cocos, and

Nazca

and the small Panama
Microplate (Text-fig. 1). The dominantly oceanic Caribbean Plate lies between the North and South Amerplates with the Caribbean Plate

Its relative eastward motion, with respect
North and South American plates is accommodated by strike-slip faults to the north and in part to
the south (but now confounded by compression from

ican plates.
to the

the west-northwestward-moving South

American

bounded by the subduction zone
of the Lesser Antilles. The western margin of the Caribbean Plate is more complex; in the northern part of
the western margin, the Cocos Plate is in contact with
Plate). In the east,

it

is

the Caribbean Plate.

western margin, a

Nazca

In the southern portion of the

triple

junction brings the Cocos and

Panama MicroThe Panama Microplate appears to

Plates in contact with the small

plate (Text-fig.

1).

canism and seismicity. In

ama Microplate border

Nazca and Pan-

contrast, the

south of Panama,

relatively

is

aseismic and without active volcanoes (Text-fig.

The oceanic

crust of the

Panama Microplate

1).

typical

is

of the widespread basalt plateau that underlies much

of the rest of the Caribbean Plate (Burke, 1988; Burke
et al.. 1978;
trast to

crust

Case

et al, 1990).

This

is in

northern Central America, where

striking con-

much

of the

older continental material (Donnelly el ah,

is

Younger volcanic deposits are found only along
margin of the isthmus adjacent to the volcanic arc associated with the subduction of the Cocos
1990).

the western

Plate.

Northern Central America consists of

Maya

1) the

Terrane, underlying Chiapas and Yucatan in southern

Mexico, Belize, and Guatemala north of the Motagua
River; and 2) the Chortis Terrane, which forms the rest
of Guatemala, El Salvador, Honduras, and Nicaragua
(Text-fig. 1). In the Maya and Chortis terranes, the
isthmus is broad, formed of continental crust, and has
a geologic history extending back to the early Paleozoic. For reviews of the geological history of northern
Central America, see Dengo (1985), Donnelly (1992),
Donnelly et al. (1990), Coates (1997), and references
therein.

Southern Central America, the focus of
includes the

Panama Microplate

book,

this

(see papers in

Mann,

1995, for recent reviews), which encompasses most of
Costa Rica and Panama but also includes part of northwestern Colombia (Text-fig. 1 ). The geology of northwestern Colombia has been reviewed by Duque-Caro
(1990a, b), and the rest of the region by Escalante
(1990), Mann (1995), Seyfried and Hellmann (1994),
and Coates and Obando (1996).
Three major tectonic movements dominated the late

Neogene tectonic evolution of the southern Central
American isthmus (Kolarsky et al, 1995; Coates and
Obando, 1996). The first was convergent tectonics of
the eastern Pacific subduction zone, the primary driv-

ing force creating the southern isthmus by forming a

have formed by northward escape from compression
of the South American and Cocos/Nazca plates, which
created its northern border, the North Panama Deformed Belt. Much of Central America lies either on

manifested

the trailing western edge of the Caribbean Plate or

to

on

23

volcanic arc with associated fore- and back-arc basins

(Astorga

et al.,

1991). During the

itself as

Miocene

the arc

an extensive archipelago stretching

South America.

Panama Microplate but a portion lies on the southwestern comer of the North American Plate (Text-fig.

The second tectonic movement, initiated about 4-3
Ma, was the shallow subduction of the Cocos Ridge,

1).

a lighter and relatively thick welt of oceanic crust

the

Since their formation in the Miocene, the two Pa-

impinged on Central America with
The Cocos Plate, with relative
northeasterly motion, is subducting vigorously under
Central America as far south as the Costa Rica-Panama border so that this region is a zone of active vol-

cific

plates have

different

motions.

ing from the Cocos hot spot (Meschede, oral

trail-

commun.,

1998). This hard-to-subduct ridge rapidly elevated the

Talamanca Range

in particular (Text-fig.

southern isthmus in general (de Boer et

rigan et
1995).

al.,

The

1990; Collins et

al.,

al..

1),

and the

1988; Cor-

1995; Kolarsky et

elevation of the Talamanca

al.,

Range probably