science 

USGS

for a changing world

Time series analysis of physical properties from Ocean Drilling 

Program Sites 1018 and 1020, California Margin

Harry J. Dowsett

U.S. Geological Survey, 955 National Center, Reston, VA 20192

OFR99-134

This report is preliminary and has not been reviewed for conformity with U.S. Geological Survey editorial 

standards
INTRODUCTION

Analysis of climate indicators from several deep sea North Atlantic cores, European lakes 

and the GRIP ice core from Greenland suggest millennial scale climate variability is a 

component of earth's climate system during the last intergiaciai (marine oxygen isotope 

stage 5). The USGS is involved in a survey of high resolution marine records covering the 

last intergiaciai period (MISS) to further document the variability of climate and assess the 

rate at which climate can change during warm intervals.

This report documents the existence of millennial scale cycles and abrupt transitions 

within MIS5 in marine sequences from the California Margin (Ocean Drilling Program Leg 

167) using readily available and routinely generated physical property measurements.

MATERIALS

Ocean Drilling Program (OOP) Leg 167 consists of a series of drill sites along the 

California Margin of North America (Fig. 1). The 13 sites of Leg 167 are arranged in a 

series of depth and latitudinal transects to aid in study of the origin and development of 

the California Current and the Neogene paleoclimatic evolution of the eastern Pacific.

32

2B°1

24

128*W 124" 120° 116* 112"

Figure 1. Location map for Leg 167 drill sites along the California Margin of North America. Sites 1018 and 

1020 are discussed in this report.
Two sites, 1018 and 1020, were selected by the USGS Warm Climates Project because of 

their location, good core recovery, and relatively high sedimentation rates, which allow 

for discrimination of millennial scale events.

Site 1018 is located 36.99°N, 123.28° W, -75 km west of Santa Cruz, California, south of 

Guide Seamount, in 2477 meters of water. The site is on a sediment drift that rises 400 m 

above the adjacent sea floor. The sediments are characterized by olive gray clay with silt 

(Shipboard Scientific Party, 1997a).

Weight percent calcium carbonate is low and varies between 1 and 5% with minimum 

values occurring during interglacials (Lyle, Boden et al., 1997). A preliminary age model 

based upon benthic 818 0 suggests MISS extends from about 18 to 27 meters composite 

depth (mcd;the spliced depth scale produced by the Shipboard Scientific Party, 1997a)(C. 

Ravelo, personal communication, 1998). This age model suggests accumulation rates 

within MISS of-15cm ky 1 .

Site 1020 is located 41.00°N, 126.43°W on the east flank of the Gorda Ridge -170 km west 

of Eureka, California in 3038 m of water. The site is on a hill that rises 50 m above the 

surrounding sea floor. Site 1020 is ideally located to monitor the strong summer upwelling 

associated with the California current system (Shipboard Scientific Party, 1997b).

Calcium carbonate ranges between 1 and 20% and is highest during glacial intervals. 

Accumulation rates are estimated to be ~9 cm ky"1 and MISS should occur between -9.5 

and 15.2 mcd based upon 618 0 stratigraphy provided by A. Mix (personal communication, 

1998).

Physical properties were measured on Leg 167 sites as an aid for hole-to-hole correlation, 

to provide estimates of properties related to composition and consolidation history of 

sediments and to provide data for the calculation of synthetic seismograms.

Bulk density, magnetic susceptibility, natural gamma ray emission and P-wave velocity 

were measured on the multi sensor track (MST) on whole core sections. After being split, 

the archive half of all cores was used for non-destructive measurement of color 

reflectance and for recording digital color images.

Three physical properties (bulk density, magnetic susceptibility and color reflectance) 

were selected for time series analysis. The following descriptions of these properties 

were summarized from Lyle et al. (1997).

GRAPE bulk density. Whole round-core sections from Site 1018 and 1020 were logged 

with the Gamma-Ray Attenuation Porosity Estimator (GRAPE). This device measures the 

electron density which is related logarithmically to the gamma-ray attenuation. Electron 

density can be related to bulk density. GRAPE bulk density measurements were made at 

4-cm intervals on all Site 1018 and 1020 cores.

Magnetic Susceptibility. Magnetic susceptibility was measured on the MST using a 

Bartington susceptibility meter MS1 with a 8 cm loop at low sensitivity (1 s measuring 

time). Sample periods were 4 s and sample intervals 4 cm.
Spectral Reflectance. The Oregon State University spectral reflectometer was used to 

make measurements of the relative spectral reflectance of Site 1018 and Site 1020 

sediments. Reflected light was measured in 10240.68-nm-wide bands ranging from 250- 

950 nm. These measurements were taken at 4- 6 cm intervals from both Site 1018 and 

1020. Raw data was converted to 4 50-nm-wide bands defined as ultraviolet (UV; 250-300 

nm}, blue (450-500 nm}, red (650-700 nm}, and near infrared (nlr; 850-900 nm}. The blue 

band was used for time series analysis.

ANALYSIS

GRAPE density, magnetic susceptibility and color reflectance data are plotted in Figures 2 

and 3 against composite depth. The MIS5 interval, defined by oxygen isotopic 

stratigraphy, is highlighted in gray. All three records at both sites show regular periodic 

variations as well as abrupt transitions occurring over several centimeters.

Spectral analysis of all three physical properties was performed for the MIS5 interval in 

each core using the SPECTRAL module of the ARAND1 software. Due to uncertainties in 

the age model and thus accumulation rates, all analyses were done in the depth domain 

and all data were sampled every 4 cm. The three physical properties from each site are 

displayed in the frequency domain in Figures 4 and 5.

At Site 1018, the GRAPE density data shows periodicity's of 21,23.5,26,32.8, and 38.5 cm. 

Magnetic susceptibility shows periodicity's of 21.9,25.3,28.6,33.9, and 40 cm. Color 

reflectance data show periodicity's of 21,25.3,28.6,33.9, and 44.4 cm. These periodicity's 

correspond to ~1500 to -2200 year cycles. Due to the 4 cm sample interval it is not 

possible to find cycles with periods less than about 1300 years.

Similar millennial scale variability is seen at Site 1020. Grape density data shows 21.7,24, 

29.9,37,41.2 and 50cm periodicity's. Magnetic susceptibility shows periodicity's of 21.3, 

24.7,27.7,33.9,39.2, and 45.5 cm. Color reflectance shows periodicity's of 22.2,29.9 and 

48.7 cm. These periodicity's correspond to 2300 to 5000 year cycles.

Allowing for uncertainties in the age model and minor fluctuations in accumulation rate 

within MIS5 at both sites, it seems likely that both sites are exhibiting a 2200 - 2300 year 

cyclicity.

1 The ARAND Software package is available from Philip Howell, Brown University Geological Sciences 

by contacting Philip_Howell@brown.edu
0.0 -,

GRAPE density

OOP SITE 1018 

Magnetic susceptibility Reflectance

100 200 300 400 500 1.5 1.6 1.7 1.8

GRAPE density (g/cm3) Magnetic Susceptibility (SI units)

i i i i i r i

7 8 9 10 11 12 13 14

Reflectance (%450-500 nm)

Figure 2. GRAPE density, magnetic susceptibility and color reflectance records from Site 1018. 

Gray box highlights MIS5 interval
GRAPE density

.5 1.6 1.7 1.8

GRAPE density (g/cm3)

OOP SITE 1020

Magnetic Susceptibility Reflectance

50 100 150 200 250 300 10

Magnetic susceptibility (SI units)

11 12 13

Reflectance (%450-500 nm)

Figure 3. GRAPE density, magnetic susceptibility and color reflectance records from Site 1020. Gray box highlights MISS interval
Sb

o o

rr Sh

n .

te ,-, 

g te

Wo

88

88

Figure 4. Results of spectral analysis of GRAPE and 

magnetic susceptibility data from MIS5 interval of Site 1018.
117.5

93.98

70.51

47.04

23.56

.0911 

Freq 

Period

for 95 lags en 215 values at At = 4.000 95% lerel CI

Color Reflectance

.000 .0050 .0100 .0150 .0200 .0250 .0X0 .0350 .0400 

200.0 100.0 66.£7 50.00 40.00 33.33 28.57 25.00 

Frequency vs. Spectral Density (Log Y-axis) Data file: 1018_Reflectance

OOP LEG 167, SITE 1018

.0450

22.22

.0500

20.00

Figure 4 continued. Results of spectral analysis of color 

reflectance data from MISS interval of Site 1018.
mrdwidth for 100 lags on 284 values at ft =4.000 80% level CI

44.00

37.91

31.82

25.73

19.65

13.56

7.469

166.3

142.8

119.3

95.81

72.32

48.82

25.33

1.833 

Freq 

Eeriod

GRAPE Density

1.381 

Freq .000 

Eeriod

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

200.0 100.0 66.67 50.00 40.00 33.33 28.57 25.00 22.22 

Freqiercy vs. $iectral Density (Log Y-axis) Data file: 1020J31ME 

OCP LH3 167, SITE 1020

.0500

20.00

Bandwidth for 100 lags on 284 values at ft. =4.000 80% level CI

Magnetic Susceptibility

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

200.0 100.0 66.67 50.00 40.00 33.33 28.57 25.00 22.22 

Freqiency vs. EJpectial Density (log Y-axis) Data file: 1020_fiacpetic 

OCP LEG 167, SITE 1020

.0500

20.00

O

a

LLI

s

2E 

m o

2mts«

0) T3 

Q. -^ 

(O ^

(O 

S

0)

O)C3

il E
for 100 legs on 282 ralues at At = 4.000 80% level CI

132.0

113.2

94.34

75.50

56.67

37.84

19.01

Color Reflectance

.1727 

Freq 

Period

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

200.0 100.0 66.67 50.00 40.00 33.33 28.57 25.00 22.22 

Hrecpeicy vs. Spectral Daisity (log Y-axis) Eata file: 1020_jreflectcnce 

OOP IEG 167, SITE 1020

.0500

20.00

Figure 5 continued. Results of spectral analysis of color 

reflectance data from MIS5 interval of Site 1020.
10

SUMMARY AND CONCLUSIONS

The results of time series analysis are useful in two ways. First, these data provide 

evidence for millennial-scale climate variability in records along the western North 

American margin essentially identical in frequency to cycles found in records from the 

North Atlantic region. This indicates that millennial-scale climate variability during the 

last interglacial is possibly a global and not regional feature.

The results of this study can also be used to structure a sampling program that will 

capture the high frequency variability exhibited by the physical property data. This will 

allow a smaller number of samples to be analyzed for traditional paleoclimate proxies 

(benthic and planktonic foraminifers, diatoms and pollen.

ACKNOWLEDGEMENTS

This paper benefited from many discussions with Dick Poore and John Barren. I am 

grateful for the isotopic data and age models provided by Cristina Ravelo and Alan Mix 

and the physical property data provided by the Ocean Drilling Program. Aaron McMahon 

provided technical assistance. This work was supported by the USGS Global Change and 

Climate History Program.

REFERENCES

Lyle, M., Boden, P., Heusser, L, Pike, J., and Mix, A., 1997. A detailed window on climate 

change in Northern California. JOI/USSAC Newsletter, 10(3): 1-4.

Lyle, M., Koizumi,!., Richter, C., et al.f 1997. Proceedings of the Ocean Drilling Program, 

Initial Reports, 167: College Station, Texas.

Shipboard Scientific Party, 1997a. Site 1018. In Lyle, M., Koizumi, I., Richter, C., et al., 

Proceedings of the Ocean Drilling Program, Initial Reports, 167: College Station Texas, 

311-352.

Shipboard Scientific Party, 1997b. Site 1020. /nLyle, M., Koizumi, I., Richter, C., etal., 

Proceedings of the Ocean Drilling Program, Initial Reports, 167: College Station Texas, 

389-429.