U.S. Department of the Interior

U.S. Geological Survey

U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1632

Multiproxy Record of the 

Last Interglacial (MIS 5e) off 

Central and Northern California, U.S.A., 

from Ocean Drilling Program Sites 1018 and 1020
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U.S. Geological Survey

Multiproxy Record of the 

Last Interglacial (MIS 5e) off 

Central and Northern California, U.S.A., 

from Ocean Drilling Program Sites 1018 and 1020

By R.Z. Poore, H.J. Dowsett, J.A. Barron, L. Heusser, A.C. Ravelo, and A. Mix

U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1632

Environmental and climatic conditions during the last interglacial 

(about 125,000 years ago) along the central and northern California 

coastal region are interpreted from study of marine cores

recovered by the Ocean Drilling Program.
U.S. DEPARTMENT OF THE INTERIOR

BRUCE BABBITT, Secretary

U.S. GEOLOGICAL SURVEY

CHARLES G. GROAT, Director

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON: 2000

Published in the Eastern Region, Reston, Va.

Manuscript approved for publication July 7, 2000.

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

does not imply endorsement by the U.S. Government.

For sale by

U.S. Geological Survey

Information Services

Box 25286, Federal Center

Denver, CO 80225

or call the toll-free telephone number

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Library of Congress Cataloging in Publication Data

Multiproxy record of the last interglacial (MIS 5e) off central and northern California, U.S.A., from Ocean

Drilling Program Sites 1018 and 1020 / by R.Z. Poore ... [et al.].

p. cm. — (U.S. Geological Survey professional paper ; 1632)

Includes bibliographical references.

1. Glacial epoch—California. 2. Paleoclimatology—California. 3. Paleoclimatology—Pleistocene. 4.

Paleoecology—California. 5. Paleoecology—Pleistocene. I. Poore, Richard Z. II. Ocean Drilling Program.

III. Series.

QE697.M7898 2000

551.69794—dc21 00–061785
CONTENTS

Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

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

Acknowledgments. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Materials and Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Chronology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

ODP Site 1020 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

ODP Site 1018 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Coastal Redwood and Upwelling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Millennial-Scale Cycles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Abrupt Events . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Summary and Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

References Cited . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

FIGURES

1. Map showing location of ODP Sites 1018 and 1020 and generalized position of the California Current

in the Pacific Ocean off California . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

2. Graphs showing oxygen-isotope records and chronology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

3–9. Graphs showing age and marine isotope stage plotted against—

3. Abundances of selected pollen taxa in samples from ODP Site 1020. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

4. Abundances of selected planktic foraminifer taxa in samples from ODP Site 1020 and 

sea-surface-temperature estimates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

5. The number of diatoms per traverse and abundances of selected diatom taxa in samples from 

ODP Site 1020 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

6. Globigerina bulloides abundance, reflectance, and calcium carbonate content in samples from 

ODP Site 1020 plus spectral analyses of reflectance data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

7. Abundances of selected pollen taxa in samples from ODP Site 1018, oxygen-isotope results from Uvigerina,

and sea-surface-temperature estimates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

8. Reflectance, magnetic susceptibility, and calcium carbonate content in samples from ODP Site 1018

plus spectral analyses of reflectance data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

9. Key environmental proxies from ODP Site 1020, core 1020D . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

TABLE

1. Calibration points used for age models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

III
CONVERSION FACTORS

IV CONTENTS

nanometer (nm)

micrometer (μm)

centimeter (cm)

meter (m)

kilometer (km)

cubic centimeter (cm3)

For temperature conversions from degrees Celsius (°C) to degrees Fahrenheit (°F), use the following:

°F = (1.8 °C) + 32

Length

0.0000000394

0.0000394

0.3937

3.281

0.6214

Volume

0.06102

inch

inch

inch

foot

mile

cubic inch

Multiply By To obtain
ABSTRACT

Marine microfossil and pollen assemblages, benthic

foraminifer δ18O, physical properties, and calcium carbonate content in sediments from Ocean Drilling Program

(ODP) Sites 1018 and 1020 off central and northern

California in the eastern North Pacific reveal strong links

between the marine and terrestrial environments during

marine isotope stage 5 (MIS 5) (~125,000 years ago). Our

multiproxy record indicates that at the beginning of the last

interglacial (MIS 5e), reduction in global ice volume,

increase in sea-surface temperature, and warming of air

temperature along the central and northern California coast

were synchronous within the resolution of our sampling

interval. The waters off the coast of northern California

(near ODP Site 1020) were strongly influenced by warm

central Pacific waters at the beginning of MIS 5e near the

maximum interglacial. The strong influence of central

Pacific waters resulted in less intense upwelling and more

zonal atmospheric circulation than exist under modern

conditions. Foraminifer assemblages from ODP Site 1018

are generally sparse and poorly preserved, but the assemblages that are present support interpretations based on

assemblages from ODP Site 1020.

Redwood became most abundant on the west coast of

North America after the peak interglacial, presumably as

coastal upwelling became more organized or persistent and

temperature cooled slightly. Variations in pollen records

are similar at ODP Sites 1020 and 1018, indicating that our

pollen data reflect regional-scale changes.

1U.S. Geological Survey, National Center, Mail Stop 955, 12201

Sunrise Valley Drive, Reston, VA 20192. Please e-mail comments to

rpoore@usgs.gov. 2U.S. Geological Survey, Mail Stop 910, 345 Middlefield Road,

Menlo Park, CA 94025. 3Lamont-Doherty Earth Observatory of Columbia University,

Palisades, NY 10964. 4Ocean Sciences Department, University of California, Santa Cruz,

CA 95064. 5College of Oceanic and Atmospheric Sciences, Oregon State

University, Corvallis, OR 97331.

Variations in physical properties, calcium carbonate

content, and diatom assemblages in sediments from ODP

Site 1020 appear to be related to changes in the dominance

of coastal versus open ocean upwelling. Evidence of

upwelling-related cycles of about 8,000 and 5,000 years

duration is present throughout much of the MIS 5 record

from ODP Site 1020. Two abrupt climatic coolings are

identified in MIS 5e, at ~126 ka and at ~119 ka.

INTRODUCTION

Many marine and terrestrial climate studies (for

example, Bond and others, 1997; Broecker, 1997) show

that millennial-scale cycles and abrupt changes are persistent in records of the last glacial interval and deglaciation.

Evidence is less clear for significant and periodic climate

variability during the last interglacial (marine isotope stage

(MIS) 5e = Eemian of the European continental record

(Shackleton, 1969)). Ice cores recovered from Greenland

yield conflicting records of climate variation during the last

interglacial. The Greenland Ice-core Project (GRIP) core

shows a number of abrupt severe cold events during the last

interglacial, indicating unstable and highly variable climate

conditions (Dansgaard and others, 1993; GRIP Members,

1993). However, analysis of the nearby Greenland Ice

Sheet Project 2 (GISP2) ice core showed a different pattern

for the early part of the last interglacial, and evidence of

major cool events observed in MIS 5e in the GRIP core

was not found in GISP 2 (Grootes and others, 1993). The

difference in the two records has motivated researchers to

evaluate more carefully climate variability of the last interglacial in a variety of environments.

Although many workers now believe that the Eemian

record of GRIP is distorted by flow deformation (for example, Grootes and others, 1993; Fuchs and Leuenberger,

1996), studies of the last interglacial in continental and

marine settings continue to reveal conflicting records of

climate variation. For example, analyses of Eemian pollen

sequences preserved in lake sediments from Germany and

France show evidence for a number of cold events and

1

Multiproxy Record of the 

Last Interglacial (MIS 5e) off 

Central and Northern California, U.S.A., 

from Ocean Drilling Program Sites 1018 and 1020

By R.Z. Poore,1 H.J. Dowsett,1 J.A. Barron,2 L. Heusser,3 A.C. Ravelo,4 and A. Mix5
thus suggest climate instability similar to that indicated by

the GRIP record (Field and others, 1994). Records in

marine cores from the Norwegian-Greenland Sea suggest

variable and unstable conditions, including significant

abrupt cold events during MIS 5e (Fronval and Jansen,

1996). However, a detailed pollen sequence from lake

sediments in the U.S. Pacific Northwest shows no evidence for strong climate variability during the last interglacial (Whitlock and Bartlein, 1997), and records from

marine cores with high accumulation rates from the North

Atlantic indicate stable climate conditions during MIS 5e

(McManus and others, 1994). Additional information on

the character and occurrence of natural climate variability during the last interglacial is needed to resolve these

differences.

In this report, we present results of a multiproxy study

of the record of the last interglacial contained in sediments

recovered at Ocean Drilling Program (ODP) Sites 1018

and 1020 off central and northern California on the west

coast of North America. The sites are located within the

influence of the southward flowing California Current

(fig. 1), which is an eastern boundary current that is sensitive to climate change (Lyle and others, 1992; Sancetta

and others, 1992; Gardner and others, 1997).

Upwelling is a major and highly variable feature of the

modern California Current. An annual shift in upwelling is

controlled by the seasonal migration of the North Pacific

High (NPH) (fig. 1). In summer (July–August), the NPH is

at its northern extent (lat ~38° N.), and equatorward winds

are most favorable for upwelling off northern California,

whereas in winter (February), the NPH is at its southern

limit (lat ~28° N.), and upwelling conditions are reduced

off northern California (for example, Huyer, 1983; Lyle,

Koizumi, Richter, and others, 1997). Upwelling can occur

off central and southern California at any time of the year

when winds are favorable. Most upwelling tends to be concentrated within 25 km of the coast, although open ocean

upwelling can occur due to development of jets within the

California Current and offshore curl in wind fields (Huyer,

1983; Sancetta and others, 1992). Substantial interannual

variability has been documented in the overall pattern of

upwelling. During anomalously warm years that are usually associated with El Niño events, southward transport of

water in the California Current and upwelling are diminished. Presumably, warmer sea-surface temperature intensifies the Aleutian Low and weakens the NPH, resulting in

decreased wind stress (see Pares-Sierra and O’Brien, 1989;

Lyle, Koizumi, Richter, and others, 1997, p. 6, fig. 4).

2 MULTIPROXY RECORD OF THE LAST INTERGLACIAL OFF CALIFORNIA, ODP SITES 1018 AND 1020

Figure 1. Location of ODP Sites 1018 and 1020 (large open circles) and generalized position of the

southward flowing California Current (broad arrow) in the Pacific Ocean off California. Small filled

circles show location of MULTITRACERS sediment traps of Lyle and others (1992): N = nearshore

site; M = midway site; G = gyre site. Core W8709A–8PC discussed in text was collected near site

M. Cores W8709A–13PC and W8709A–9BC discussed in text were collected at site N. Black shading on continental border shows modern distribution of coastal redwood forests (after Powell and

others, 1994). Inset map shows generalized locations of North Pacific High in winter (W) and summer (S) and of major surface currents. Figure modified from Sancetta and others (1992).

135° W

California

Oregon

0 100 200 300

California

Current

130° 125° 120° 45° N

40°

35°

PACIFIC OCEAN

1020

1018

S

W

G

M

N

California

 Current

Alaskan

Current

. .

.. . .

.

..

.

.

.

...

. ....

. .

.

. .

. ....

.

. .. . . .

... .

. .

. . ..

. .

.

.

.. .

 400 KILOMETERS 

0 100 200 300 MILES
Sediment accumulation rates in the MIS 5 sequences

recovered at ODP Sites 1018 and 1020 were rapid enough

(≥~10 cm/1,000 years) to resolve millennial-scale variations (Lyle, Koizumi, Richter, and others, 1997; Lyle and

others, in press). The sediments along the west coast of

North America contain marine microfossils and a significant terrigenous component, including well-preserved

pollen assemblages, that allow direct correlation of marine

and continental records (Heusser and Balsam, 1977;

Gardner and others, 1988; Sancetta and others, 1992). In

addition, extensive physical properties measurements

available from ODP 1018 and 1020 cores show distinct

quasi-periodic variations (Dowsett, 1999). Physical properties, such as magnetic susceptibility and density, can

reflect climate variations (Bloemendal and deMenocal,

1989; Thouveny and others, 1994; Rosenbaum and others,

1996; Moros and others, 1997). Thus, the sediments

recovered at ODP Sites 1018 and 1020 provide an opportunity to investigate climate variability during the last

interglacial and to test the relation of the variations in

physical properties records to several traditional climate

proxies.

ACKNOWLEDGMENTS

We thank Aaron McMahon and Christopher Tracey

(U.S. Geological Survey, USGS) for technical assistance

and Mitch Lyle (Boise State University) for access to samples from ODP Site 1020 and advanced copies of manuscripts in press. We appreciate constructive comments on

this manuscript by Mitch Lyle, Dan Muhs (USGS), and

two anonymous reviewers. The Ocean Drilling Program

provided samples. This work was supported by the Global

Change and Climate History Program of the U.S.

Geological Survey. The National Science Foundation provided partial support for L. Heusser.

MATERIALS AND METHODS

Site 1018 of Ocean Drilling Program Leg 167 is at lat

36.99° N., long 123.28° W., ~75 km west of Santa Cruz,

Calif., just south of the Guide Seamount in a water depth

of 2,477 m (fig. 1). The site is on a sediment drift that is

400 m above the adjacent sea floor. Four holes were cored

at Site 1018, recovering a Pliocene to Quaternary sequence

of siliciclastic to diatom and nannofossil clays and oozes.

Calcium carbonate content is low throughout the sequence,

usually ranging between 1 and 5 percent with occasional

peaks greater than 10 percent (Lyle and others, in press).

Minimum values occur in interglacial deposits. We

obtained a series of samples focusing on MIS 5e from Hole

1018C core 3 and Hole 1018D core 3 for foraminifer, isotope, and pollen analyses. Samples from Holes 1018C and

1018D are incorporated into a composite depth scale being

used by the ODP 167 scientific party (Lyle and others, in

press).

Site 1020 of ODP Leg 167 is at lat 41.00° N., long

126.43° W., on the east flank of the Gorda Ridge ~170 km

west of Eureka, Calif., in a water depth of 3,038 m (fig. 1).

The site is on a hill that is 50 m above the adjacent sea

floor. Four holes were cored at Site 1020, recovering a

Pliocene to Quaternary sequence of siliciclastic clay and

nannofossil clay with minor amounts of clayey nannofossil

ooze. Calcium carbonate content ranges between 1 and 20

percent (Lyle and others, in press). Minimum values occur

in interglacial deposits. Several sets of samples were analyzed from ODP Site 1020. One series of samples from

Hole 1020D core 2 focusing on MIS 5e was obtained for

foraminifer, isotope, and pollen analyses. Pollen data in

1020D core 2 are supplemented by 19 samples used for initial reconnaissance studies (Heusser, in press). A separate

set of samples from Hole 1020D core 2 and Hole 1020C

core 2 that includes all of MIS 5 was obtained from M.

Lyle and analyzed for diatoms. Samples from Holes 1020D

and 1020C are incorporated into a composite depth scale

(Lyle and others, in press).

Samples for foraminifer, pollen, and isotope analyses

were dried at <50°C, disaggregated in deionized water, and

wet sieved at 63 μm. The <63-μm fraction from initial wet

sieving was retained and used for pollen analyses. The use of

the <63-μm fraction for pollen census eliminates large

pollen grains (primarily conifers) from our census. However,

the other microfossils are so sparse that we adopted this procedure to maximize use of our samples and also provide

multiple proxies from single samples. All pollen samples

were processsed by using standard chemical procedures,

including the addition of known amounts of an exotic tracer

to calculate pollen concentration.

Taxonomic identification of pollen was based on the

use of modern pollen reference collections from western

North America. Pollen grains were identified to species

level when possible; otherwise, pollen and spores were

assigned to genera or higher rank (see Poore and others,

1999, for taxonomic categories used). Floral (terrestrial

pollen grains) counts average ≥130 specimens per sample. 

The >63-μm fraction was dried and then sieved into

two fractions: 63–150 μm and >150 μm. Samples with

abundant planktic foraminifers were mechanically split to

obtain subsamples of ~300 planktic specimens >150 μm

for faunal census. The entire >150-μm fraction was used

for the foraminifer census if <300 planktic foraminifers

were present. Sea-surface temperatures (SST’s) based on

planktic foraminifer assemblages were estimated by using

the modern analog technique (MAT) that incorporated a

revised modern core-top calibration data set that includes

core-top samples from the U.S. Pacific margin (Dowsett

and Poore, 1999).

Oxygen-isotope analyses were done on the benthic

foraminifers Fontbotia wuellerstorfi and Uvigerina spp. In

general, three specimens of F. wuellerstorfi and five specimens of Uvigerina were used in each analysis. Isotopic

MATERIALS AND METHODS 3
4 MULTIPROXY RECORD OF THE LAST INTERGLACIAL OFF CALIFORNIA, ODP SITES 1018 AND 1020

3.0

3.5

4.0

4.5

Uvigerina 18O (

‰)

RMCD

2.5

3.0

3.5

12 13 14 15 16

F. wuellerstorfi 18O (

‰)

2.5

3.0

3.5

4.0

4.5

5.0

5.5

6.0

Uvigerina 18O (

‰)

17.5 20.0 22.5 25.0 27.5 30.0

RMCD

-1

-0.5

0

0.5

1

18O (normalized)

60 70 80 90 100 110 120 130 140

4 5a 5b 5c 5d 5e 6

4.22

5.1

5.0

5.31 5.3

5.4

5.5

6.0

6.2

5.3 5.4

5.5

6.0

4.22

5.1 5.31 5.33

5.4

5.5

6.0

5.33

AGE, IN THOUSANDS OF YEARS AGO

A

B

C

EXPLANATION

Uvigerina 18O

F. wuellerstorfi 18O

Figure 2. Oxygen-isotope records and chronology. A, Normalized oxygen-isotope record and

time scale for marine isotope stage (MIS) 5 (Martinson and others, 1987). Stage 6/Stage 5

boundary (Termination II) and Stage 5/Stage 4 boundary are from Martinson and others (1987).

Boundaries between substages within MIS 5 are from this study (see text for discussion). B,

Oxygen-isotope measurements on the benthic foraminifers Uvigerina and Fontbotia wuellerstorfi from this study of ODP Site 1020 plotted against revised mean composite depth (RMCD)

in meters (Lyle and others, in press). Arrows mark points on the isotope record that were correlated to the normalized record of Martinson and others (1987) and that were used to construct

the age model for this study. Event 5.0 (not shown in B above; see table 1) was established from

the Site 1020 oxygen-isotope record of Lyle and others (in press, fig. 6). C, Oxygen-isotope

measurements on Uvigerina from ODP Site 1018. Arrows mark points on the isotope record

used to construct the age model for this study. Data from 24 to 27 m RMCD are from this study.

Data from above 24 m RMCD and below 27.5 m RMCD are from Andreasen and others (in

press). Ages and depths used for the age models are listed in table 1; see text for discussion. 
analyses of samples from Site 1018 were conducted on a

PRISM micromass mass spectrometer at the University of

California, Santa Cruz (UCSC). Analytical precision is

±0.08‰ for oxygen standards. Analyses of samples from

Site 1020 were conducted at Oregon State University

(OSU) on a Finnigan MAT–251 stable isotope mass spectrometer. Analytical precision based on replicate analyses

of local calcite standards is ±0.08‰ for oxygen standards.

Additional details of analytical procedures were discussed

in Poore and others (1999). Isotopic values were calibrated via National Institute of Standards and Technology

(NIST) isotopic reference material NBS–18 and NBS–19

(UCSC) and NBS–19 and NBS–20 (OSU) to the Pee Dee

Belemnite scale maintained by the International Atomic

Energy Agency in Vienna (VPDB). Values are reported

relative to the VPDB standard in delta notation and

expressed in per mil.

Diatom samples (0.5–1 cm3

) were processed in hydrogen peroxide and hydrochloric acid. Strewn slides of the

residues were prepared. Except where preservation was

poor, at least 300 diatoms per slide were counted at a magnification of 1,250 during random traverses of the slides

by using the counting techniques of Schrader and Gersonde

(1978). Note that percentages of Chaetoceros spores are

calculated as percent of the total diatom assemblages

whereas percentages of all other taxa are calculated on a

Chaetoceros-free basis. This is done because Chaetoceros

spores dominate the diatom assemblages in all samples.

Isotopic results, discussion of taxonomic categories used

for faunal and floral census, and tables giving pollen,

foraminifer, and diatom census data were provided by

Poore and others (1999).

Bulk density, magnetic susceptibility, and color

reflectance records were examined for this study. Bulk

density and magnetic susceptibility were measured

onboard ship at 4-cm intervals by using the multisensor

track (MST) on whole core sections. Reflectance was

measured by the Oregon State University spectral reflectometer on split core surfaces. Methods and instruments

used to obtain these data are outlined in Lyle and others

(1997). Tables of physical property measurements are provided with the Initial Cruise Report on CD-ROM (Lyle,

Koizumi, Richter, and others, 1997).

CHRONOLOGY

We used the normalized oxygen-isotope record and

chronology of Martinson and others (1987) as the basis for

developing a time scale for this study. Dated features of the

normalized oxygen-isotope age model of Martinson and

others (1987) identified in our isotope records (fig. 2) were

used to create an age model and assign ages to individual

samples by assuming constant sediment accumulation rates

between control points (table 1). Our isotope data were

supplemented by isotope and carbonate data from Sites

1018 and 1020 (Lyle and others, in press), which were used

to help locate the MIS 6/MIS 5 boundaries at both sites.

The MIS 5/MIS 4 boundary (event 5.0) was derived from

the oxygen-isotope record for Site 1020 of Lyle and others

(in press, fig. 6). In order to facilitate discussion of our

results, we found it convenient to define the boundaries

between substages of MIS 5. Following the suggestion of

Shackleton (1969) for recognizing the boundary between

substages 5e and 5d, we place boundaries between substages of MIS 5 at the midpoint of the transition between

them (see fig. 2). According to our definition and the time

scale of Martinson and others (1987), the total duration of

MIS 5e is 14,000 years. The interval of warmest conditions

(normalized δ18O ≥0.5 in fig. 2) is ~9,000 years.

Table 1. Calibration points used for age models.

[RMCD, revised mean composite depth in meters; ka, thousand years ago]

Depth Age1

Event1 (RMCD) (ka)

Ocean Drilling Program Site 1018

4.22 18.49 64.09

5.1 20.49 79.25

5.31 22.69 96.21

5.33 23.89 103.29

5.4 24.89 110.79

5.5 26.05 123.82

6.0 27.20 129.84

Ocean Drilling Program Site 1020

5.0 9.85 73.91

5.3 13.00 99.38

5.4 14.00 110.79

5.5 15.20 123.82

6.0 15.73 129.84

6.2 16.17 135.10

1

Event terminology and ages from Martinson and others (1987).

RESULTS

ODP SITE 1020

All samples we examined from ODP Site 1020 yielded relatively well preserved pollen assemblages.

Occurrence and preservation of foraminifer and diatom

assemblages are variable. Sample resolution within MIS 5e

is ~1,000 years. Distributions of common pollen types are

shown in figure 3. Pine (Pinus), the most common pollen

type in the assemblages, decreases in abundance from MIS

6 into MIS 5e deposits to low but still significant values,

and then increases upsection into MIS 5d deposits. The

highest amounts of alder (Alnus), oak (Quercus), and

coastal redwood (Sequoia sempervirens) occur in MIS 5e

RESULTS 5
deposits. Percentages of spruce (Picea) and western hemlock (Tsuga heterophylla) vary throughout the sequence.

Oak and redwood show a distinct increase within MIS 5e

deposits to a broad abundance peak and then decrease dramatically into 5d deposits. Oak and redwood are present

throughout MIS 5d deposits in low abundances and then

increase slightly in MIS 5c sediments. There is a distinct

lag in the oak and redwood abundance peaks, with redwood peaking later in MIS 5e at the point where pine

begins to increase.

Planktic foraminifers are moderately well preserved in

many of our ODP Site 1020 samples but are usually few in

number, and most assemblages show effects of dissolution.

Distributions of common taxa of planktic foraminifers are

shown in figure 4. Left-coiling Neogloboquadrina pachyderma has minimum values within MIS 5e deposits and

then increases to maximum values in MIS 5d sediments.

Left-coiling N. pachyderma and right-coiling N. pachyderma s.l. (includes gradational forms between right-coiling

N. pachyderma and N. dutertrei) are inversely related.

Assemblages from MIS 5e include right-coiling N. pachyderma s.l. along with significant amounts of Globorotalia

inflata (lower part) and N. dutertrei (upper part) and varying amounts of Globigerina bulloides. In contrast, the

assemblages of MIS 5c consist almost exclusively of various amounts of left- and right-coiling N. pachyderma with

G. bulloides. Neogloboquadrina dutertrei and G. inflata

are essentially absent. 

Sea-surface-temperature (SST) estimates for winter

and summer seasons derived from planktic foraminifer

assemblages are also shown in figure 4. The warmest SST

estimates derive from MIS 5e samples at levels containing

the warm-water taxa G. inflata and Globigerinoides ruber

and minimum values of the polar form left-coiling N.

pachyderma. Assemblages are sparse and poorly preserved

in samples dated at ~124 to 119 ka, and only a few quantitative SST estimates were possible over that interval. The

maximum summer SST estimates for MIS 5e at Site 1020

are as much as 4°C warmer than our modern core-top calibration values, whereas winter maximum SST estimates

for MIS 5e are near modern values (see Dowsett and Poore,

1999). Our planktic foraminifer SST estimates compare

well with alkenone-based paleotemperature estimates for

MIS 5e at Site 1020. The alkenone results indicate that

6 MULTIPROXY RECORD OF THE LAST INTERGLACIAL OFF CALIFORNIA, ODP SITES 1018 AND 1020

30 40 50 60 70 80

PINE (%)

100

110

120

130AGE (ka)

0 5 10 15 0 5 10 15 20 25

WESTERN HEMLOCK (%)

0 5 10 15

ALDER (%)

0 5 10 15 20

OAK (%)

0 5 10 15 20

REDWOOD (%)

5c

5d

5e

6

MIS ODP SITE 1020

SPRUCE (%)

Figure 3. Age and marine isotope stage plotted against abundances (in percent) of selected pollen taxa in samples from ODP Site 1020.
average SST’s during the maximum interglacial were about

2°C above modern values (Kreitz and others, in press). The

maximum winter SST estimates for MIS 5e at ODP Site

1020 are similar to Holocene winter SST estimates derived

from alkenone and radiolarian data from piston core

W8709A–8PC (Prahl and others, 1995) collected nearby

(fig. 1).

The foraminifer SST estimates indicate that winter

temperatures during MIS 5d were ~8°C–10°C colder than

the modern winter temperature. Alkenone and radiolarian

data from core W8709A–8PC suggest that winter SST’s

during the last glacial maximum were 4°C–5°C below

modern temperatures (Prahl and others, 1995). It seems

unlikely that winter SST’s off northern California during

MIS 5d would be colder than winter SST’s during the last

glacial maximum. Additional work is required to resolve

the apparent discrepancy between our MIS 5d winter SST

estimates and the last glacial maximum SST estimates of

Prahl and others (1995). The few samples yielding enough

foraminifers to provide SST estimates for MIS 5c indicate

temperatures several degrees warmer than MIS 5d temperatures but below peak temperatures of MIS 5e.

Diatom abundance and preservation are highly variable

in MIS 5 sediments of ODP Site 1020 (fig. 5). Assemblage

data are reported only for samples containing ≥10 diatoms

per traverse. The abundance of the Chaetoceros spores is calculated for the entire diatom assemblage, whereas the abundances of the other taxa are calculated on a Chaetoceros-free

basis. Chaetoceros spores are always common to abundant.

On a Chaetoceros-free basis, Thalassionema nitzschioides

and Stephanopyxis spp. are the most common taxa.

Inspection of figure 5 reveals that Chaetoceros and T. nitzschioides vary inversely throughout the record and show distinct cycles in deposits of MIS 5b and MIS 5a and parts of

MIS 5d. The relation between these two taxa is less clear in

MIS 5e. Chaetoceros spores first appear in MIS 5e sediments at relatively low abundances and then increase in

abundance towards MIS 5d deposits.

Stephanopyxis spp. increases in abundance from MIS

5e into MIS 5d sediments and shows distinct abundance

cycles in MIS 5b and 5a and the lower part of MIS 4. The

Stephanopyxis minima in MIS 5b and MIS 5a coincide

with intervals of high diatom abundance as measured by

the diatoms/traverse index and peaks in T. nitzschioides.

Stephanopyxis is a shelf indicator, and its abundance variations in deepwater sediments are sometimes interpreted as

an off-shelf transport index. Gardner and others (1988)

studied cores off northern California and related increased

abundance of Stephanopyxis spp. in glacial deposits to

enhanced downslope transport during glacial periods.

Hemphill-Haley and Fourtanier (1995) suggested that

increased numbers of Stephanopyxis spp. at ODP Site 893

in the Santa Barbara Basin were due to selective dissolution of more delicate diatoms. However, they also observed

a correspondence between increased Stephanopyxis spp.

and increased benthic and reworked diatoms in glacial

deposits, which suggests enhanced downslope transport.

Pseudoeunotia doliolus, which is a warm-water taxon

indicative of the central Pacific water mass, occurs in significant amounts only in the lower diatom-bearing samples

of MIS 5e. Roperia tesselata, which is a temperate form,

becomes an important component of the assemblages

deposited during MIS 5a. Thalassiosira pacifica, which is

a cooler water subpolar form, occurs in MIS 5d deposits

and is common to abundant in MIS 5b deposits and portions of the MIS 5a record. Note that R. tesselata and T.

pacifica show alternating abundance peaks in sediments

deposited in the MIS 5b to 5a interval, suggesting cycles on

the order of 5,000 years long. The temperature record of

MIS 5 suggested by the diatom assemblages is consistent

with the temperatures indicated by foraminifer assemblages and isotope data. Warmest SST’s are indicated within early MIS 5e. Cooler SST’s in late MIS 5e and much

cooler SST’s in MIS 5d were followed by increasing SST’s

in MIS 5c that were not as warm as SST’s in MIS 5e, as

evidenced by the lack of P. doliolus in the assemblages.

Cooler SST’s prevailed in MIS 5b, and SST’s were variable

during MIS 5a.

For ODP Site 1020, magnetic susceptibility and

reflectance values show similar structure for sediments

deposited in MIS 5e to 5c, but very large changes in susceptibility values for sediments deposited near the end and

beginning of MIS 5 tend to obscure the correlation (see

Dowsett, 1999). The wet-bulk density of the sediments as

measured by the Gamma Ray Attenuation Porosity

Evaluator (GRAPE) system also shows high-frequency

variations, but the variations are not systematically related

to the other physical properties. The reflectance record

shows the clearest pattern of variation, with well-defined

cycles having a period of ~8,000 years (fig. 6). Cycles of

~5,000 years are evident over some intervals (MIS 5e to 5d

and MIS 5a to MIS 4). Spectral analyses show higher frequency variations at 3,000 and 2,200 years (fig. 6). Several

prominent maxima in carbonate content coincide with

reflectance peaks; for example, see the carbonate peaks in

figure 6 centered at ~81 ka and 112 ka. Minor carbonate

peaks at ~94 ka and 102 ka also match reflection maxima.

However, a peak in reflectance within MIS 5e corresponds

to a carbonate low.

The abundance of the foraminifer Globigerina bulloides shows a negative correlation with the reflectance

record (note that the scale for G. bulloides in fig. 6 increases to the left). Globigerina bulloides is typically a species

of transitional to subpolar water masses (Kipp, 1976); it is

also an indicator of upwelling in many areas (for example,

Prell and Curry, 1981; Sautter and Thunell, 1991; Hui-Ling

and others, 1997). We infer that some of the G. bulloides

abundance fluctuations are related to the intensity of offshore upwelling and that, at ODP Site 1020, the 8,000- and

5,000-year cycles in reflectance during MIS 5 contain an

RESULTS 7
8 MULTIPROXY RECORD OF THE LAST INTERGLACIAL OFF CALIFORNIA, ODP SITES 1018 AND 1020

MIS

5c

5d

5e

6

ODP SITE 1020

100

110

120

130

0 25 50 75 0 20 40 60 0 10 20 0 25 50 0 10 20 0 1 3 4 5 2 0 5 10 15 0 2.5 5 7.5 10 12.5 15 17.5 20

AGE (ka)

N. pachyderma(lc) (%)

N. pachyderma(rc) (%)

N. dutertrei (%) G. bulloides (%) Gr. inflata (%) Gl. ruber (%) T. quinqueloba (%) SST (°C)

Warm month SST

Cold month SST

Modernwarmmonth

Moderncoldmonth

Figure 4. Age and marine isotope stage plotted against (1) abundances(in percent) of selected planktic foraminifer taxa in samples from ODPSite 1020 and (2) sea-surface-temperature (SST) estimates based on themodern analog technique (MAT) for Site 1020 samples. N. pachyderma(lc) = left-coiling Neogloboquadrina pachyderma. N. pachyderma (rc) =

right-coiling N. pachyderma and transitional forms between right-coiling 

N. pachyderma and N. dutertrei. G. bulloides = Globigerina bulloides.

Gr. inflata = Globorotalia inflata. Gl. ruber = Globigerinoides ruber. T.quinqueloba = Turborotalita quinqueloba. Modern warm month and coldmonth SST’s are shown by vertical dashed lines on the SST plot. TheSST estimate lines are dashed where samples are sparse.
RESULTS

9

5a

5b

5c

5d

5e

6

MIS ODP SITE 1020

110

120

130

AGE (ka)

4

100

70

80

90

0 50 100 150 20 30 40 50 60 70 80 90 0 20 40 60 80 0 5 10 15 0 5 10 15 0 1 2 3 4 5 6 0 5 10 15 20 25 0 20 40 60 80

Chaetoceros (%) T. nitzschioides (%) P. doliolus (%) A. tabularis (%) R. tesselata (%) T. pacifica (%) Stephanopyxis (%) # DIATOMS/

TRAVERSE

Figure 5. Age and marine isotope stage plotted against (1) the number ofdiatoms per traverse and (2) abundances (in percent) of selected diatomtaxa in samples from ODP Site 1020. Abundances of diatom taxa are plotted only for samples having ≥10 specimens per traverse (at magnification

of x 1,250). The abundance of the Chaetoceros spores is calculated for

the entire diatom assemblage, whereas the abundances of the other taxaare calculated on a Chaetoceros-free basis. Chaetoceros = Chaetocerosspores. T. nitzschioides = Thalassionema nitzschioides. P. doliolus =Pseudoeunotia doliolus. A. tabularis = Azpeitia tabularis. R. tesselata =Roperia tesselata. T. pacifica = Thalassiosira pacifica.
10 MULTIPROXY RECORD OF THE LAST INTERGLACIAL OFF CALIFORNIA, ODP SITES 1018 AND 1020 MIS 5a5b5c 5d5e ODP SITE 1020 110 120

130

AGE (ka)

4

100

70

80

90

G. bulloides (%)

30 10

8

REFLECTANCE

(% 450–500 nm)

6 10 12 14 10 0 5 15

(wt %) CaCO3

COLOR REFLECTANCE

FREQUENCY

SPECTRAL DENSITY

8,000

4,900

3,000

2,200 years

80% LEVEL

CONFIDENCE INTERVAL

.000 .0050 .0100 .0150 .0200 .0250 .0300 .0350 .0400 .0450 .0500

132.0

113.2

94.34

75.50

56.67

37.84

19.01

.1727

50

Figure 6. Age and marine isotope stage plotted against (1) Globigerina bulloides abundance (in percent), (2) reflectance, and (3) calcium carbonate(CaCO3) content (in weight percent) in samples from ODP Site 1020 plus

spectral analyses of reflectance data. Note that the scale for the abundance ofG. bulloides increases to the left. Calcium carbonate measurements are fromLyle and others (in press). Reflectance data are from Lyle, Koizumi, Richter,and others (1997). Reflectance values are reported in percentage of reflectedlight from 450 to 500 nm. The power spectrum shows color reflectance datain the frequency domain. The spectrum was calculated by using theBlackman-Tukey method (Jenkins and Watts, 1968) on a linearly detrendedsequence sampled every 300 years. Peaks in spectral density occur at 2,200,3,000, 4,900, and 8,000 years.
DISCUSSION 11

upwelling signal. High values of reflectance generally indicate dominance of coastal upwelling and increased carbonate content of the sediments, whereas low values of

reflectance indicate dominance of offshore upwelling and

decreased carbonate content of sediments. Our interpretations are consistent with the conclusion of Lyle and others

(in press) that millennial-scale cycles in calcium carbonate

content in cores from the California margin reflect changes

in calcium carbonate production by plankton, not dissolution. Thus, the physical properties of ODP Site 1020 sediments contain a climatic signal, but the signal is not a simple glacial-interglacial signal.

ODP SITE 1018

Sediments deposited near the beginning of MIS 5e

through MIS 5c were examined from ODP Site 1018; sample resolution within MIS 5e ranges from ~300 to 600

years. Pollen assemblages are relatively well preserved

(fig. 7). Pine decreases from >50 percent of the pollen

assemblage at the base of MIS 5e deposits to values <30

percent within MIS 5e and then increases upsection into

MIS 5d deposits. Pine is usually dominant in the remainder

of the pollen assemblages except for an interval deposited

within MIS 5c. Spruce occurs in trace amounts except in

the lower deposits of MIS 5e. Alder is present only in trace

abundances in MIS 5e sediments (Poore and others, 1999).

Oak is consistently present in our Site 1018 samples with a

distinct short maximum in MIS 5e and broad maxima in

MIS 5d and MIS 5c. In general, the oak increases in MIS

5d and 5c correspond to decreases in pine (fig. 7).

Redwood is abundant only in MIS 5e sediments and shows

a well-defined maximum just above the short oak abundance peak. Thus, the sequence of oak maxima followed by

redwood maxima in MIS 5e observed at ODP Site 1020 is

present in the record from ODP Site 1018.

Planktic foraminifers were generally sparse and poorly

preserved in MIS 5 samples from ODP Site 1018. Only a

few samples had ≥50 specimens in the >150-μm fraction,

and most were barren or nearly barren of foraminifers.

Although foraminifer assemblages are sparse, a few of the

assemblages in the sequence provided SST estimates within

acceptable statistical parameters (see Dowsett and Poore,

1999), and samples from the lower part of the section contained sufficient numbers of the benthic foraminifer

Uvigerina for isotopic analyses (figs. 2, 7). The distribution

of common taxa in samples containing at least 50 specimens

was presented by Poore and others (1999). In general,

foraminifer assemblages from samples at the base of MIS 5e

deposits are dominated by left-coiling Neogloboquadrina

pachyderma, whereas the few assemblages higher in the

MIS 5e record are dominated by right-coiling N. pachyderma with important contributions from N. dutertrei,

Globigerina bulloides, and Globorotalia inflata.

The warmest SST estimates for MIS 5e at Site 1018

are from samples that are dated at about 125 ka and that

have δ18O values for Uvigerina spp. that approach but do

not reach the minimum values seen for MIS 5e (fig. 7). The

summer SST estimates are about 2°C warmer than our

modern core-top calibration values (see Dowsett and

Poore, 1999) and are consistent with, but are about 2°C

below, the warmest SST estimates for MIS 5e samples

from ODP Site 1020. Planktic foraminifer assemblages at

younger MIS 5e levels with minimum Uvigerina δ18O values are sparse and highly dissolved. Thus, SST estimates

derived from these samples probably underestimate the

maximum SST temperatures during MIS 5e at ODP Site

1018.

Variations in the reflectance and magnetic susceptibility records from ODP Site 1018 closely correspond (fig. 8).

Inspection of figure 8 shows cycles on the order of 10,000

years and 5,000 years, and spectral analyses reveal higher

frequency cycles of 3,300, 2,500, 2,200, and 1,900 years.

However, the cycles do not show a clear relation to carbonate content of the sediments. The most prominent peak

in carbonate content is centered at ~116 ka and corresponds to a low in the reflectance record. It is likely that

carbonate values from ODP Site 1018 are too low to

strongly influence the physical properties of the sediments.

Alternatively, the carbonate signal could indicate differences between conditions and processes at ODP Sites

1020 and 1018. Note that prominent carbonate peaks for

samples from Sites 1020 and 1018 do not coincide (compare figs. 6 and 8). We cannot interpret the environmental

significance of the reflectance and magnetic susceptibility

data from ODP Site 1018 at this time. However, comparison of figures 6 and 8 demonstrates that care must be taken

in inferring environmental conditions from physical properties records. Relations between proxy data and environmental conditions obtained in a specific core or depositional system may not necessarily be valid in other cores or

systems.

DISCUSSION

The data from ODP Sites 1018 and 1020 show strong

links between the marine and terrestrial environments.

Previous studies demonstrated that the pollen in marine

sediments along the U.S. Pacific margin reflects vegetation

of the adjacent coastal areas (for example, Heusser and

Balsam, 1977; Gardner and others, 1988; Sancetta and others, 1992; Heusser, 1998). Redwood-dominated coniferous

forests with spruce and hemlock distinguish the presentday natural coastal vegetation of northern California.

Inland in drier settings, oak woodland and grassland occur

and, at higher elevations in the Coast Range, montane

forests are present with pine, evergreen oaks, fir (Abies),

Douglas fir (Pseudotsuga menziesii), and mountain hemlock (Tsuga mertensiana) (Barbour and Major, 1977).

Thus, in areas off central and northern California, pine is

generally an indicator of cooler or glacial conditions, and
12 MULTIPROXY RECORD OF THE LAST INTERGLACIAL OFF CALIFORNIA, ODP SITES 1018 AND 1020 5c 5d5e

6

MIS ODP SITE 1018

100

110

120

130

0

AGE (ka)

SST (°C)

Warm month SST

Cold month SST

Moderncoldmonth

Modernwarmmonth

0 5 10 15 20 5 4.5 4 3.5 3 2.5

Uvigerina O (

‰) 18

0 10 20 30 40 10 20 30 0 10 10 20 30 40 50 60 70

PINE (%) OAK (%) REDWOOD (%) SPRUCE (%)

Figure 7. Age and marine isotope stage plotted against (1) abundances (in percent) of selected pollen taxa in samples from ODP Site 1018, (2) oxygen-isotope results from

Uvigerina, and (3) sea-surface-temperature (SST) estimates based on the modern analog technique (MAT) for samples from ODP Site 1018. Modern warm month and cold

month SST’s are shown by vertical dashed lines on the SST plot. 
DISCUSSION 13

5a

5b

5c

5d

5e

MIS

ODP SITE 1018

110

120

130

AGE (ka)

4

100

70

80

90

8

REFLECTANCE

(% 450–500 nm)

12 10 0 5 15

(wt %) CaCO3

COLOR REFLECTANCE

FREQUENCY

SPECTRAL DENSITY

10,000

3,300

5,000

2,500

2,200

1,900 years

80% LEVEL

CONFIDENCE INTERVAL

.000 .0050 .0100 .0150 .0200 .0250 .0300 .0350 .0400 .0450 .0500

164.4

140.9

117.5

93.98

70.51

47.04

23.56

.0911

7.5 10 12.5 15 17.5 20

MAGNETIC

SUSCEPTIBILITY

7 9 10 11

Figure 8. Age and marine isotope stage plotted against (1) reflectance, (2)magnetic susceptibility, and (3) calcium carbonate (CaCO3) content (in

weight percent) in samples from ODP Site 1018 plus spectral analyses ofreflectance data. Reflectance and magnetic susceptibility data are from Lyle,Koizumi, Richter, and others (1997). Reflectance values are reported in percentage of reflected light from 450 to 500 nm. Calcium carbonate measurements are from Lyle and others (in press). The power spectrum shows colorreflectance data in the frequency domain. The spectrum was calculated byusing the Blackman-Tukey method (Jenkins and Watts, 1968) on a linearlydetrended sequence sampled every 400 years. Peaks in spectral density occurat 1,900, 2,200, 2,500, 3,300, 5,000, and 10,000 years.
14 MULTIPROXY RECORD OF THE LAST INTERGLACIAL OFF CALIFORNIA, ODP SITES 1018 AND 1020

oak is an indicator of warm conditions. Redwood is an

indicator of increased moisture and moderated summer

coastal temperature related to coastal fog, which is, in turn,

related to coastal upwelling (Sancetta and others, 1992;

Heusser, 1998).

The data from marine and terrestrial proxies at ODP

Site 1020 show clear evidence for rapid warming at the

beginning of MIS 5 (fig. 9). Warming of coastal air temperatures is indicated by the decrease in pine and increase

in oak pollen. The foraminifer MAT SST values show

warming at the same time that oak pollen increases.

Reduction in global ice volume is indicated by the decreasing δ18O values for benthic foraminifers. Plots of δ18O values for Uvigerina spp. and F. wuellerstorfi show the same

structure, and either can be used to identify MIS 5e and 5d

(fig. 9). The δ18O scales in figure 9 have been adjusted so

that the smallest values from the two taxa coincide. Note

that the values become offset by about 0.25‰ at the larger

values in MIS 5d, suggesting that fractionation between

Uvigerina spp. and F. wuellerstorfi may be nonlinear.

Maximum values for oak coincide with minimum values for pine and benthic δ18O. We assume that values of

δ18O for benthic foraminifers from Site 1020 largely

reflect global ice volume; therefore, the sequence deposited in MIS 5e indicates that reduction in global ice volume,

increases in SST’s, and warming of air temperatures along

the coast were all synchronous within the resolution of our

sampling interval. Minima in δ18O and maxima in SST’s

and coastal air temperatures coincide.

In MIS 5e deposits of Site 1020, the maximum in oak

pollen is followed by a maximum in redwood pollen. The

redwood maximum occurs as isotope and pine values are

beginning to increase and as SST’s are beginning to

decrease. Following results from studies of modern surface

sediment samples and sediment traps, we infer that the

variations in pollen abundance in our marine samples

reflect variations in abundance of vegetation on the adjacent coastal regions (Heusser and Balsam, 1977; Gardner

and others, 1988; Sancetta and others, 1992; Heusser,

1998). Thus, maximum development of redwood forests

occurred after the peak interglacial as temperatures cooled

slightly and presumably as coastal upwelling became more

organized or persistent (see discussion below).

The data from ODP Site 1018 are less complete but

show a similar pattern (see fig. 7). Pine abundance and benthic isotope values decrease upsection in the MIS 5e

record. Within 5e deposits, an oak maximum is followed by

a redwood maximum. The oak maximum coincides with

the minimum values in pine and benthic δ18O. The few

SST estimates available indicate that an increase in oak and

warming of surface waters coincide. The redwood maximum clearly follows the maximum in oak and corresponds

to the beginning of the increase in pine abundance. At Sites

1020 and 1018, the lag between oak and redwood maxima

is ~2,000–3,000 years.

The sequence and timing of pollen and marine proxy

events at ODP Site 1018 match those of the correlative

events at ODP Site 1020. Thus, while conditions along the

California margin have been highly variable in detail during glacial-interglacial transitions (Gardner and others,

1997), it appears that during the last interglacial, the major

terrestrial vegetation changes and links between marine

and terrestrial temperature changes along the northern and

central California coastal area were in phase. A similar

sequence of oak pollen maximum followed by redwood

pollen maximum has been documented for the Holocene

marine sediments off northern California (Sancetta and

others, 1992) and for marine sediments from older

Pleistocene interglacials recorded at Sites 1018 and 1020

(Heusser, in press; Heusser and others, in press). Thus, the

lag between oak and redwood maxima observed in the MIS

5e sections from ODP Sites 1020 and 1018 appears to be

typical of late Pleistocene interglacial records in this area.

In general, the transition from glacial to interglacial

conditions should favor increased upwelling intensity

along the coast of central and northern California. During

glacials, the large ice sheet on the North American continent results in a high-pressure cell over the continent that

deflects the jet stream to the south and also causes the summer North Pacific High to be weaker and move south and

west of its modern position (COHMAP, 1988; Lyle and

others, 1992; Bartlein and others, 1998). These changes

reduce or eliminate the northerly winds that drive

upwelling along the coast (for example, Lyle and others,

1992, fig. 15). During deglaciation, the melting of the ice

sheet allows a progressive change back to the modern configuration, and upwelling should increase.

Our results indicate that development of upwelling

during deglaciation is more complex in detail. Figure 9

shows that the microfossil assemblages deposited in the

warmest part of MIS 5e at ODP Site 1020 contain

Globorotalia inflata along with the diatom Pseudoeunotia

doliolus. Both of these taxa decline rapidly in the upper

part of the MIS 5e record, as does the warm-water

foraminifer Globigerinoides ruber (fig. 4). Globorotalia

inflata is typical of Pleistocene interglacial assemblages of

the central Pacific water mass (Poore, 1999), as is P. doliolus (Sancetta and others, 1992). In addition, diatoms are

sparse in sediments deposited during the earliest part of

MIS 5e. When diatoms first occur in MIS 5e deposits, the

assemblages with P. doliolus have relatively low values of

the coastal upwelling indicator Chaetoceros and relatively

high values of the offshore upwelling indicator

Thalassionema nitzschioides (fig. 5). Diatoms are better

preserved and Chaetoceros becomes more abundant in

sediments deposited toward the end of MIS 5e, indicating

increased influence of upwelling (fig. 9). The diatom and

planktic foraminifer assemblages indicate strong influence

of warm central Pacific waters at ODP Site 1020 during

the warmest part of MIS 5e, and they probably indicate
DISCUSSION 15 30 40 50 60 70 PINE (%)

100

110

120

130

AGE (ka)

0 5 10 15 20

OAK (%)

0 5 10 15 20

REDWOOD (%)

5c

5d

5e

6

MIS

ODP SITE 1020

Continental Vegetation Coastal Waters

Coastal

Upwelling Warm Month SST Global Ice Volume

4.5 4.0 3.5 3.0

Uvigerina 18

20 40 60 80 0 5 10 15 0 10 20

Chaetoceros (%) P. doliolus (%) Gr. inflata (%)

5 10 15 20

SST (°C)

Modernwarmmonth

F. wuellerstorfi 18O (‰)

3.50 3.25 3.00 2.75 2.50 2.25

O (‰)

Figure 9. Age and marine isotope stage plotted against key environmental proxies from ODP Site 1020, core 1020D. Continentalvegetation: pollen data are from figure 3. Coastal waters: plankticforaminifer data are from figure 4 (Gr. inflata = Globorotaliainflata), and diatom data are from figure 5 (P. doliolus =Pseudoeunotia doliolus). Coastal upwelling: diatom data are from 

figure 5 (Chaetoceros = Chaetoceros spores). Global ice volume:oxygen-isotope data for benthic foraminifers Uvigerina and

Fontbotia wuellerstorfi are from figure 2; the δ18O scales in figure

9 have been adjusted so that the smallest values from the two taxacoincide. Warm month sea-surface-temperature (SST) estimates:the SST estimates are from figure 4.
that atmospheric circulation was more zonal than it is

today. A more modern circulation pattern with stronger or

more persistent coastal upwelling and maximum development of redwood forests did not develop until later in the

interglacial, at ~121 ka.

The record of the last deglaciation in piston cores off

of southern Oregon shows a similar pattern. Sancetta and

others (1992) found that in cores W8709–9BC and

W8709A–13PC (fig. 1), P. doliolus reached maximum values in Holocene sediments dated at between 10 and 7 ka.

Chaetoceros was common in the early Holocene and continued to increase into the late Holocene, reaching maximum values after P. doliolus declined in abundance.

Sancetta and others (1992) concluded that the abundance

of P. doliolus, combined with the relatively low abundance

of Chaetoceros in the early part of the Holocene, reflects

warmer waters and reduced upwelling compared to modern

or late Holocene conditions.

Model simulations (COHMAP, 1988; Bartlein and

others, 1998) of the last deglaciation suggest development

of strong summer northerly winds and thus upwelling

along the U.S. northwest Pacific coast during the deglacialglacial transition and into the early part of the interglacial.

Our results from MIS 5e and the record of Sancetta and

others (1992) show that strong upwelling off the U.S.

northwest Pacific coast develops in the middle to late part

of interglacials, not in the early part as suggested by the

model simulation.

In the modern ocean, El Niño events result in warmer

surface waters along the coast of California. The warmer

temperatures coincide with diminished southward oceanic

transport and reduced upwelling along the California margin, presumably due to weakening of the North Pacific

High (see Pares-Sierra and O’Brien, 1989; Lyle, Koizumi,

Richter, and others, 1997, fig. 4). Coastal upwelling and

associated high productivity off central California are

reduced during El Niño events (Chavez, 1996). Our results

suggest that the response of the California Current to maximum interglacial warming and El Niño events is similar.

Warming of surface waters above modern values results in

reduced or less persistent coastal upwelling and lower productivity compared to modern conditions.

The diatom assemblages from ODP Site 1020 suggest a

complex and variable history of upwelling throughout all of

MIS 5. As noted above, abundant Chaetoceros spores are

indicative of summer coastal upwelling, and Thalassionema

nitzschioides is a proxy for upwelling at the edge of the

coastal zone and the central water mass (offshore

upwelling) (Sancetta and others, 1992). These two taxa are

common in all our samples from Site 1020 that have

diatoms. Chaetoceros spores show an increase in abundance

from MIS 5e deposits into MIS 5d deposits and T. nitzschioides shows a decrease through the same interval (fig. 5),

indicating an overall trend towards increasing coastal

upwelling from the latter part of MIS 5e into MIS 5d.

These taxa show an inverse correlation and distinct

cycles over much of the rest of MIS 5. For example, abundance variations between 95 and 87 ka have a simple correlation coefficient (r2

) of –0.64. Inspection of figure 5

indicates that cycles of about 5,000 years are especially

well developed in MIS 5a and 5b and are possible in MIS

5d. We interpret these cycles as changes in the influence of

coastal versus offshore upwelling at Site 1020 through

time. Offshore upwelling tends to be strongest during transitions between substages. Above the middle part of MIS

5c (~100 ka), there is a strong inverse correlation between

percent Thalassionema nitzschioides and percent

Stephanopyxis spp. (r2 between 95 ka and 74 ka = –0.76).

This relation is interpreted to reflect variations in the

amount of pelagic diatom deposition (T. nitzschioides) versus downslope transport of slope species (Stephanopyxis

spp.). In general, during MIS 5b and 5a, trends in percent

Chaetoceros closely parallel those of Stephanopyxis spp.,

suggesting that downslope transport may have played an

important role in the deposition of Chaetoceros during the

early part of MIS 5.

COASTAL REDWOOD AND UPWELLING

Summer upwelling, because of its influence on the

generation of coastal fog, is required for the development

of extensive coastal redwood forests. The abundance of

Chaetoceros in the record from ODP Site 1020 indicates

that coastal upwelling was well developed in parts of MIS

5e, 5d, 5b, and 5a. We have limited data from MIS 5c, but

we infer that coastal upwelling occurred during some or all

of MIS 5c because upwelling was clearly developed during

parts of MIS 5e and 5a. However, redwood pollen remains

at very low levels in our samples from MIS 5d and 5c

deposits at Site 1020 (fig. 9). The low abundance of oak

and high abundance of pine in our assemblages in MIS 5d

and 5c deposits from Site 1020 indicate that the climate

was too cold for redwood forests to re-occupy large areas

along the northern California coast during MIS 5c. This

interpretation is consistent with our maximum SST estimates for MIS 5c that are several degrees cooler than

Holocene or MIS 5e temperatures.

The record from ODP Site 1018 is more complicated.

At Site 1018 (fig. 7), oak pollen shows broad abundance

increases in sediments deposited during MIS 5d and MIS

5c that approach peak MIS 5e values. In addition, pine

abundance declines to near MIS 5e levels in a number of

samples from MIS 5c deposits. The pollen data suggest that

warm coastal air temperatures occurred during parts of

MIS 5d and 5c and that temperatures during MIS 5c

approached MIS 5e conditions. We also infer that coastal

upwelling must have been active during parts of MIS 5d

and 5c because we have evidence for coastal upwelling

from ODP Site 1020. However, redwood pollen remains at

very low background levels throughout our MIS 5d and

16 MULTIPROXY RECORD OF THE LAST INTERGLACIAL OFF CALIFORNIA, ODP SITES 1018 AND 1020
MIS 5c assemblages. We conclude that extensive redwood

forests developed along the coast of northern and central

California only during short intervals following interglacial

maxima when optimal temperature and upwelling conditions for their growth developed. Coastal redwood forests

declined during cooler or warmer climatic conditions.

MILLENNIAL-SCALE CYCLES

Inspection of the physical properties records and spectral analyses establishes the presence of strong cycles having frequencies of ~8,000 and 5,000 years in sediments

from ODP Site 1020 and 10,000 and 5,000 years in sediments from ODP Site 1018 (figs. 6 and 8). In addition,

spectral analyses reveal several higher frequency cycles,

including cycles of ~3,000 years and ~2,200 years in both

records. Our data, however, do not show clear evidence for

the ~1,500-year cycle that is persistent in Holocene and

glacial intervals of the North Atlantic (Bond and others,

1997).

We conclude, however, that our study cannot be used

to rule out the presence of the ~1,500-year cycle in MIS 5

records of the California margin. The persistent North

Atlantic cycles are greatly subdued in the Holocene record

compared to cycles in deposits from glacial intervals and,

in addition, the North Atlantic cycles were not observed in

all proxies (Bond and others, 1997). The Holocene cycles

of ~1,500±500 years in the North Atlantic are best developed in ice-rafting indices based on type and abundance of

lithic grains and are not reflected in planktic foraminifer

isotope records nor are they convincing in abundance variations of foraminifers such as left-coiling N. pachyderma

that are typically used as paleoceanographic indicators.

We conclude that the poor preservation of microfossils in

our samples, especially in the high-accumulation-rate

sequence of ODP Site 1018, and the lower accumulation

rate of the better preserved record at ODP Site 1020 preclude recognition of cycles with frequences less than

~2,000 years.

ABRUPT EVENTS

We see evidence for two abrupt cooling events in MIS

5e. One event occurred at ~126 ka and is marked best by

the rebound in pine pollen abundance that is superimposed

on an overall trend of declining pine abundance at ODP

Sites 1020 and 1018 (figs. 3 and 7). The rebound to higher

pine abundance is seen in more than one sample in both

cores, and oak and redwood show a corresponding reversal

in their trend towards increasing values at the same levels.

The foraminifer assemblages and resulting SST estimates

for ODP Site 1020 also show a brief cooling event associated with the pine rebound. The summer SST estimates

show a sharp decline of 5°C (fig. 4).

The second abrupt cooling occurred near the end of

MIS 5e at ~119 ka. The event is expressed in the pollen

record from ODP Site 1020 by the drop in oak and redwood abundances from near peak interglacial levels down

to background levels within 1,000 to 2,000 years (fig. 3).

Foraminifer assemblages also show indications of cooling

at this level with SST estimates dropping by 3°C between

samples dated at 118 and 117 ka (fig. 4). Redwood pollen

from Site 1018 shows a decline from 30 percent of the

assemblage to 15 percent of the assemblage between 119

and 118 ka (fig. 7).

The pollen records from these cores are noisy, but we

consider the cooling events at ~126 ka and ~119 ka to be

reliable signals and not spurious events. Pollen evidence

for the events occurs at the same levels in both cores, and,

at ODP Site 1020, the cooling is also indicated by the

foraminifer data. Thus, it is unlikely that the events can be

explained by counting errors, burrowing, or some other

type of reworking (Crowley, 1999). The event at ~119 ka

represents a rapid cooling associated with the end of MIS

5e and the start of the transition to MIS 5d. The event at

126 ka occurred early in MIS 5e and appears to have been

a brief cool pulse just prior to maximum interglacial conditions. The event at 126 ka is thus similar in timing to the

brief cooling event at 8 ka in the early part of the Holocene

(Alley and others, 1997).

SUMMARY AND CONCLUSIONS

Analysis of several marine climate proxies and pollen

in cores from ODP Sites 1018 and 1020 reveals a close

linkage between marine and terrestrial climate change during the last interglacial. Changes in global ice volume,

coastal SST’s, and coastal air temperature as indicated by

benthic foraminifer isotope values, planktic foraminifer

assemblages, and pollen assemblages from the same samples coincide. During the early warming of MIS 5e, warm

central Pacific waters moved closer to the California margin, atmospheric circulation was more zonal, and coastal

upwelling was reduced. Optimum conditions for development of redwood forests along the central and northern

California coast were confined to a short interval just after

the maximum warming of MIS 5e when coastal upwelling

became well organized or persistent and ocean and atmospheric temperatures were still warm but below maximum

interglacial levels. Substantial redwood forests were not

reestablished along the coast during MIS 5c or MIS 5a

even though coastal upwelling was present. Reflectance

values for sediments from ODP Site 1020 generally correlate with calcium carbonate contents and show cycles of

about 8,000 to 5,000 years that are linked to variations in

upwelling. High values of reflectance represent dominance

of coastal upwelling and increased carbonate content of the

sediments, whereas low values of reflectance represent

SUMMARY AND CONCLUSIONS 17
dominance of offshore upwelling and decreased carbonate

content of sediments. Reflectance values for sediments

from ODP Site 1018 are not clearly correlated with sediment carbonate variations. The relation between physical

properties and climate proxies is complicated and likely

varies depending on the depositional setting.

The poor preservation of microfossils in these cores

precludes recognition of the cycles having frequences less

than ~2,000 years recorded in Holocene sediments of the

North Atlantic. Pollen records from ODP Sites 1020 and

1018 are supported by foraminifer assemblages from Site

1020 and indicate two abrupt cooling events at about 126

ka and 119 ka within MIS 5e.

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REFERENCES CITED 19
Selected Series of U.S. Geological Survey Publications

Books and Other Publications

Professional Papers report scientific data and interpretations 

of lasting scientific interest that cover all facets of USGS investigations and research.

Bulletins contain significant data and interpretations that are of 

lasting scientific interest but are generally more limited in 

scope or geographic coverage than Professional Papers.

Water-Supply Papers are comprehensive reports that present 

significant interpretive results of hydrologic investigations of 

wide interest to professional geologists, hydrologists, and engineers. The series covers investigations in all phases of hydrology, including hydrogeology, availability of water, quality of 

water, and use of water.

Circulars are reports of programmatic or scientific information 

of an ephemeral nature; many present important scientific 

information of wide popular interest. Circulars are distributed 

at no cost to the public.

Fact Sheets communicate a wide variety of timely information 

on USGS programs, projects, and research. They commonly 

address issues of public interest. Fact Sheets generally are two 

or four pages long and are distributed at no cost to the public.

Reports in the Digital Data Series (DDS) distribute large 

amounts of data through digital media, including compact discread-only memory (CD-ROM). They are high-quality, interpretive publications designed as self-contained packages for viewing and interpreting data and typically contain data sets, 

software to view the data, and explanatory text.

Water-Resources Investigations Reports are papers of an 

interpretive nature made available to the public outside the formal USGS publications series. Copies are produced on request 

(unlike formal USGS publications) and are also available for 

public inspection at depositories indicated in USGS catalogs.

Open-File Reports can consist of basic data, preliminary 

reports, and a wide range of scientific documents on USGS 

investigations. Open-File Reports are designed for fast release 

and are available for public consultation at depositories.

Maps

Geologic Quadrangle Maps (GQ’s) are multicolor geologic 

maps on topographic bases in 7.5- or 15-minute quadrangle 

formats (scales mainly 1:24,000 or 1:62,500) showing bedrock, 

surficial, or engineering geology. Maps generally include brief 

texts; some maps include structure and columnar sections only.

Geophysical Investigations Maps (GP’s) are on topographic 

or planimetric bases at various scales. They show results of 

geophysical investigations using gravity, magnetic, seismic, or 

radioactivity surveys, which provide data on subsurface structures that are of economic or geologic significance.

Miscellaneous Investigations Series Maps or Geologic 

Investigations Series (I’s) are on planimetric or topographic 

bases at various scales; they present a wide variety of format 

and subject matter. The series also incudes 7.5-minute quadrangle photogeologic maps on planimetric bases and planetary 

maps.

Information Periodicals

Metal Industry Indicators (MII’s) is a free monthly newsletter that analyzes and forecasts the economic health of five 

metal industries with composite leading and coincident 

indexes: primary metals, steel, copper, primary and secondary 

aluminum, and aluminum mill products.

Mineral Industry Surveys (MIS’s) are free periodic statistical 

and economic reports designed to provide timely statistical data 

on production, distribution, stocks, and consumption of significant mineral commodities. The surveys are issued monthly, 

quarterly, annually, or at other regular intervals, depending on 

the need for current data. The MIS’s are published by commodity as well as by State. A series of international MIS’s is also 

available.

Published on an annual basis, Mineral Commodity Summaries is the earliest Government publication to furnish estimates 

covering nonfuel mineral industry data. Data sheets contain 

information on the domestic industry structure, Government 

programs, tariffs, and 5-year salient statistics for more than 90 

individual minerals and materials.

The Minerals Yearbook discusses the performance of the 

worldwide minerals and materials industry during a calendar 

year, and it provides background information to assist in interpreting that performance. The Minerals Yearbook consists of 

three volumes. Volume I, Metals and Minerals, contains chapters about virtually all metallic and industrial mineral commodities important to the U.S. economy. Volume II, Area Reports: 

Domestic, contains a chapter on the minerals industry of each 

of the 50 States and Puerto Rico and the Administered Islands. 

Volume III, Area Reports: International, is published as four 

separate reports. These reports collectively contain the latest 

available mineral data on more than 190 foreign countries and 

discuss the importance of minerals to the economies of these 

nations and the United States.

Permanent Catalogs

“Publications of the U.S. Geological Survey, 1879–1961”

and “Publications of the U.S. Geological Survey, 1962–

1970” are available in paperback book form and as a set of 

microfiche.

“Publications of the U.S. Geological Survey, 1971–1981” is 

available in paperback book form (two volumes, publications 

listing and index) and as a set of microfiche.

Annual supplements for 1982, 1983, 1984, 1985, 1986, and 

subsequent years are available in paperback book form.