PERIODIC VARIATION IN NATURAL RADIOACTIVITY

OF LAKE BOUCHET SEDIMENTS

J. XANTHAKIS, I. LIRITZIS

Research Center for Astronomy and Applied Mathematics, Academy of Athens, Athens, Greece

and

R. B. GALLOWAY

Department of Physics, Edinburgh University, Edinburgh, Scotland

(Received 30 April 1992)

Abstract. Low level counting of alpha and beta particles has been carried out on a 5 long sediment core from the lake La Bouchet in France, spanning the past around 24000 years. A total of around 60 data points were spectrally analysed with the successive approximations method. Several whole or quasi-periodicities were located for the two radioactivity data sets, in different time intervals; for the alpha counting, periods of 1000~1200, 2000, 6000 and 24 000 years and for the beta counting periods of 1000, 3000, 4000, 8000 and 24 000 years were obtained. The non-stationarity nature of the obtained periods are discussed in relation to (a) palaeoclimatic fluctuations impact on mineral carrying natural radiosotopes partitioning of the sediment deposition of the last glacial and (b) other solar-terrestrial agents.

Introduction

Several proxy climatic time-series exist deriving from ocean (6180 on foramini- feras, carbonate content, palaeomagnetic), lake (palaeomagnetic) and cave (6180) sediments. Shackleton and Opdyke, 1976; Harmon, 1975; Berger, 1977, 1988; Creer et al., 1990). Here we offer another such a set of data, which is analysed for periodicity; alpha and beta particle counting of lake Bouchet sediments.

Data

The lake sediment core (B52) for lake Bouchet, France, was 5.86 m long spanning the last 30 000 years. The lake Bouchet is contained in a volcanic structure of the “maar” type (explosive crater of phreatomagmatic origin) the detrital sediment mineral consisting of weathered/eroded basalt flows and scoracious material. The dating is based on radiocarbon determinations and pollen diagrams (Creer et al., 1990).

Samples were those in plastic cubes of 2 cm side, which had been measured before by a magnetometer, taken in steps of approx. 2.5 ems. A total of around 60 data points were spectrally analysed (Xanthakis and Liritzis, 1991).

The rate of deposition of the mineral phase in the lake Bouchet sediments was extremely low, from about 0.25 to 0.33 mm/yr, in the lower parts (1.3 to 6 m) of

Earth, Moon and Planets 59, 191&200, 1992 0 1992 Kluwer Academic Publishers. Printed in the Netherlands

192 J. XANTHAKIS ET AL.

the core which were deposited in a cold climate, falling to 0.05 to 0.07 mm/yr in the upper about 1.3 m (post-wurm) levels.

Measurements

Alpha-counting of small sediment samples were performed with a ZnS (Ag) scintillator for time intervals between lo-60 ks and beta-particle counting with a plastic scinitillator NE 102 A for time intervals between lo-30 ks, both counters being appropriately calibrated. (Galloway and Liritzis, 1991; Liritzis and Gallo- way, 1982). The statistical errors were + 5% for alpha and + 2% for beta. The alpha and beta counting rates were then plotted against time-depth.

Periodic Analysis of the Radioactivity Data

Prompted by the periodical nature of various solar and terrestrial phenomena in short and long intervals (Table 3) an attempt was made to spectrally analyse the (Y- and P-radioactivity time series.

A) ALPHA RADIOACTIVITY

The a-log was first detrended by fitting a long sinusoidal term of 24 000 years (Figure 1). In the second half of the record a 6000 years periodic term seems to overlap the second half of the longer period. The mean alpha variation is given by:

a mean = 6 + 2.5 sin(2r/24 0OO)T + 0.9 sin 2~~/6000(T - 23 500) 23 500 - 11500 BP . (1)

The residuals (IV) from the subtraction of the above two periodic terms from the original data were subsequently fitted with sporadic (quasi-) periods. The compo- site spectrum is described by Equation (2):

W = al sin(2v/2000)T + a2 sin(2&200)T + a3 sin(2&OOO)T +

+ a4 sin(2r/500)T + us sin(271-/400)T + u6sin(2r/200)T,

where coefficients ai, i = 1 - 6, are given in Table I. Thus, the computed best fit to the data is given by Equation (3).

(2)

U camp. _

-amean+ w, (3)

where the fitted parameters are 57, the degrees of freedom 4, the standard devi- ation between measured and computed values t 0.37 and the significance 94%.

The revealed sporadic periods are; 24 000, 6000, 2000, 1200, 1000, 500, 400 and 200 years. The last two low periods are not reliable, they fall below the time resolution of the analysed series, which is around 300 years.

.

.

. . . A . .

. .

NATURAL RADlOACTlVlTY OF LAKE BOUCHET SEDIMENTS

! . . l .

.

:

.

I l

.

194 J. XANTHAKIS ET AL.

TABLE I

Coefficients of a’s and time intervals T for Equation 2

a1 T

1.50 21500-20 500, 8500-7500 -2.5 20 750-19 750

4 T

-3.0 9500-8500 -1.5 15 600-14 900

a3 T

1.00 16 900-16 400, 14 250-12 750 -1.5 12 500-12 000, 7250-5750,

6750-1250

a4 T

1.5 14 750-14 250

05 7

-1.5 18 350-18 150 -1.0 18 200-17 800

2.5 17 200-17 000, 14 950-14 750

a6 T

2.5 17 800-17 600 5.5 7500-7400

B) BETA RADIOACTIVITY

Similarly for the /?-log (Figure 2) the mean variation is

P mean = 0.125 + 0.075 sin(2r/24 OOO)( T - 24 000) ,

and the respective residuals

(4)

W = al sin(2&3000)T + az sin(2m/4000)T + a3 sin(25-/3000)T i

+ a4 sin(27r/lOOO)T + a5 sin(25-/400)T, (5)

where coefficients ai, i = 1 - 5, are given in Table II. Finally the computed curve is

P camp. _ - pm- + w, (6)

where the parameters used were 39, the degrees of freedom 16, the standard deviation between measured and computed values +- 0.0076 and the significance 94%.

The sporadic periods are 24 000, 8000, 4000, 3000, 1000 and 400 years. Both time series exhibit the long period of 24 000 years and the 1000 years, the

other differ.

NATURAL RADlOACTlVlTY OF LAKE BOUCHET SEDIMENTS 195

.

>

?

.

1

. .

. - . :

z - .

2

.

-J -* . . < . l . . . . ,i- - . 1 . . - . - -. -, * - - * k . 3 .

196 J. XANTHAKIS ET AL.

TABLE II

Coefficients a’s and time intervals T of Equation (5)

-0.03 18 500-10 500 0.02 5000-1000

a2 T

-0.03

a3

21500-19 500

T

0.02 14 000-12 000 -0.02 9700-5250

a4 T

-0.01 21500-20 000 0.06 16 000-13 500

a5 T

-0.06 8550-8350 0.04 7550-7350 0.02 7350-7150 0.03 15 200- 15 000

Discussion of the Periodicities Obtained

The fundamental period of 24 000 years and the quasi-periods between 400-8000 years in both radioactivity logs of lake Bouchet sediments reflect palaeoclimatic and probably palaeosolar activity variation. The rationale for this inference is implied by the mechanism which reflects the solar output-atmosphere (climate)- sedimentation continuum. That is, solar activity (solar wind, flares, magnetic field) causes atmospheric and climatic disturbances (clouds, precipitation, temperature variation, monsoon, glacials/interglacials) which in turn cause weathering (erosion, diagenesis) on surface rocks and the surficial geomorphological mosaic of a region, which subsequently cause proportional transportation of radioisotopes (in min- erals) in the deep parts of the ocean or lake (Liritzis and Galloway, 1992).

Consequently, the observed radiation dose per sedimentary stratum is antici- pated to vary in proportion to palaeoclimatic and palaeosolar activity.

According to the astronomical theory of palaeoclimates - a particular version of which is usually referred to as - the Milankovich theory - the long term variations in the geometry of the earth’s orbit and rotation are the fundamental causes of the comings and goings of Pleistocene ice ages or of the climate of the past 2 or 3 Myrs.

The periodic variations correspond to eccentricity ( - 95 Kyr), axial tilt (ob- liquity) - 41 Kyr and precession (19-23 Kyr) (Table III).

The higher term in the expansion of precession of equinoxes is the obtained 24 Kyr fundamental period the length of our record.

NATURAL RADIOACTIVITY OF LAKE BOUCHET SEDlMENTS 191

TABLE III

Some periodicities in solar-planetary proxy climatic parameters (in Kyrs)

Time Intervals Parameters <l-1.5 2-3 3-4 4-5 6-8 10-12 19-24 -40

Radioactivity alpha 0.4 2 6 24

0.5 1.0 1.2 0.4 1.0

beta 3 4 8 24

Obliquity 41 Precession 19-23 Berger (1989) Foraminifera 2.3 4.6 10 CY80 11.2 (from deep-sea 12.5 cores) Hays et al. (1976); Kominz et al. (1979); Berger (1977, 1988); Xanthakis et al. (1992) Greek Archaeomagnetic Intensity Xanthakis-Liritzis (1991)

0.2, 0.5 4 8 0.7, 1.0 1.4

c-14 0.2 2 Neftel et al. 0.4-0.5 (1981) 0.7, 1.0

Aurora Sunspots 0.2 Liritzis (1990)

Solar System Orbital Dynamics 0.2-0.6 2.2 3.34 6.67 (Harmonics) 1.1

The other (quasi-) periodicities have been found in other solar-terrestrial phe- nomena and are summarised in Table III.

An attempt will be made to attribute to these phenomena a causal relationship: should such a geophysical connection exist the obtained periodicities may be explained. Harmonics of the obliquity and precessional periodicitties as quasi- periods of 10 200 + 1200, 4600 * 3000, 2300 ‘-t- 200 have been found by Pestiaux et al. (1987) in 6r80 of planktonic and benthic foraminifera on an Indian ocean core, with MESA and lagged correlation spectrum analysis.

Also, a detailed spectrum analysis (MESA, Autocorrelation, FFT, successive approximations) on Greek archaeomagnetic intensities has revealed periodicities of approx. 8000, 4000, 1400, 1000, 700, 500, and 200 years, and almost similar periods were obtained from analysis of palaeointensity data (lake Windermere, Britain) for the last 9000 years (Xanthakis and Liritzis, 1991).

198 J. XANTHAKIS ET AL.

Apart from the long periods, the other periods do not persist through the data record, but exhibit a sporadic quasiperiodic character and superimpose on each other.

On the other hand, radiocarbon variation in the atmosphere during the past 8000 years exhibit a variety of periods whose spectra appear to fluctuate in intensity: 2000 ? 500, approx. 1000, 700, 400-500, and 200 years the last being most signifi- cant (Neftel et al., 1981; Sonett, 1984; Suess, 1980). Attribution of these periods to a cosmic-ray modulation due to a periodic solar activity variation (Stuiver and Quay, 1980) or even to exoheliospheric signals (Sonett, 1984) is assumed.

Moreover, aurora1 and sunspot numbers have been spectrally analysed and significant periodicity of 200 years and shorter ones have been quoted (Liritzis, 1990).

The many common periodicities found in several solar-terrestrial phenomena (e.g., sunspot numbers, C-14, geomagnetic intensity, tree-rings, “Be, 180 both in polar-ice, and even thermoluminescent signal in ocean sediments) may offer an interpretation for the possible causes of climate changes; considering mainly the potential impact of a past and present variable sun, which exhibits long ( > 1000 years) and short-term periodicities.

There has been reported, also, long and short term rhythmicity in terrestrial landforms and deposits (soil cycles). The agents which influence the duration of these periods are glacial-interglacial cycles, slope, fluvial systems stability, tectonic movements, hydrological regimes, precipitation of calcareous tuff in lake history, sedimentation supply, (see selected papers in Rampino et al., 1987).

Climatic periodicity in &‘O, radioactivity of sediments, rainfall, to mention a few, can be associated with observed phases of multiple solar-terrestrial par- ameters, and this association alone is capable to signify a causal relationship, amounted to the recognition that climatic changes are forced by factors outside the normal terrestrial atmosphere and its dynamic system.

Last, but not least the impact of planets, especially the large ones Saturn, Jupiter and Uranus (the former two possess 86% of the entire solar system’s angular momentum) should not be neglected. According to Fairbridge (pers. communi- cation to IL) the key to the exact periodicity is in the harmonics and resonances of fundamental tones based on orbital dynamics of the Sun and planets; displaying spectral peaks of solar cycle and of C-14 flux in 9600 year dendrochronologic series. Such fundamental tones are indicated by Fairbridge to be 6672 and 93 418 years, while resonances occur mainly at 3rd and 7th tones, thus producing harmon- ics almost resembling our obtained periods.

However, the apparent network of periodicities, found here and elsewhere, reinforces the complicated behaviour of dynamical (orbital, pulsed forcing) solar- planetary system, the observed modulation being a secondary product of self- organization of Earth’s response.

NATURAL RADIOACTIVITY OF LAKE BOUCHET SEDIMENTS 199

Conclusions

The obtained periods though not persistent rather reflect palaeoclimatic changes, judging by the mechanism of radioactivity partitioning in lake/ocean sediment- ation, mentioned ealier. In particular, the similarity of radioactivity variation with other solar-terrestrial phenomena reinforces the causal relationship between Sun- Atmosphere-Earth, which is, however, regulated by complex rhythmicity due to the complicated behaviour that characterizes the systems.

Acknowledgement

We are thankful to Prof. Rhodes Fairbridge for encouragement and useful corre- spondence.

References

Berger, A.: 1977, ‘Support for the Astronomical Theory of Climatic Change’, Nature 268, 44-4.5. Berger, A.: 1988, ‘Milankovich Theory and Climate’, Review of Geophysics 26(4), 624-657. Berger, A.: 1989, ‘Pleistocene Climatic Variability at Astronomical Frequencies’, Quaternary Intern.

2, 1-14. Creer, K. M., Blunk, I. and Thouveny, N.: 1990, ‘Climatic and Geomagnetic Influences on the Lac

du Bouchet Palaeomagnetic SV Record Through the Last 110 000 Years’, Phys. Earth Planet. ht. 64(2-4) 314-339.

Galloway, R. B. and Liritzis, Y.: 1990, ‘Scattering Correction in Beta Dosimetry by Beta Particle Counting’, Nuclear Tracks Radiat. Meas. 18(1/2), 239-247.

Hays, J. D., Imbrie, J. and Shackleton, N.: 1976, ‘Variations in the Earth’s Orbit: Pacemaker of the Ice-Ages’, Science 194: 1121-1132.

Harmon, R. S.: 1975, Ph.D. thesis, McMaster University, Hamilton, Canada. Kominz, M. A. i Heath, G. R., Ku, T. L. and Pisias, N. G.: 1979, ‘Bruhnes Time Scales and the

Interpretation of Climatic Change’, Earth and Planet. Sci. Lett. 45, 394-410. Liritzis, I. and Galloway, R. B.: 1992, ‘Solar-Climatic Effects on Radionuclidic Partitioning in

Lake/Ocean Sediments: First Results’, in preparation, Liritzis, Y.: 1990, ‘Evidence for Periodicities in the Aurora1 Occurrence Frequency since 300 AD and

their Implications’, PAGEOPH, 133(2), 201-211. Liritzis, Y. and Galloway, R. B.: 1982, ‘A Comparison of Two Techniques for the Determination of

the p-Dose Rate in Ceramics for Thermoluminescence Dating’, Nucl. Instr. Methods, 192, 555-558. Neftel, A., Oeschger, H. and Suess, H. E.: 1981, ‘Secular Non-Random Variations of Cosmogenic

Carbon-14 in the Terrestrial Atmosphere’, Earth Plan. Sci. Letts. 56, 127-147. Pestiaux, P., Duplessy, J. C. and Berger, A.: 1987, ‘Palaeoclimatic Variability at Frequencies Ranging

from 104 Cycle Per Year to 1O-3 Cycle Per Year. Evidence for Non-Linear Behaviour of the Climate System’, Climate, History, Periodicity and Predictability (Rampino M. R. et al., Eds.), Van Nostrand Reinhold Co, New York, 285-299.

Rampino, M. R. et al. (Eds.): 1987, Climate: History, Periodicity and Predictability, Van Nostrand Reinhold Co, New York, pp. 588.

Shackleton, N. J. and Opdyke, N. D.: 1976, ‘Oxygen-Isotope and Palaeomagnetic Stratigraphy of Pacific Core V28-239, Late Pliocene to Latest Pleistocene’, Geolog. Sot. America Memoirs 145, 449-464.

Sonett, C. P.: 1984, ‘Very Long Solar Periods and the Radiocarbon Record’, Rev. Geophys. Sp. Phys. 22(3), 239-254.

Stuiver, M. and Quay, P. D.: 1980, ‘Changes in Atmospheric Carbon-14 Attributed to a Variable Sun’, Science 207, 11-18.

200 J. XANTHAKIS ET AL.

Suess, H. E.: 1980, ‘The Radiocarbon Record in Tree Rings of the Last 8000 Years’, Radiocarbon 22(2), 200-209.

Xanthakis, J. and Liritzis, I.: 1991, ‘Geomagnetic Field Variation as Inferred from Archaeomagnetism in Greece and Palaeomagnetism in British Lake Sediments Since 7000 BC’, Vol. 53, Academy of Athens, pp. 222.

Xanthakis, J., Liritzis, I. and Tzanis, E.: 1992, ‘Periodic Variation of aI80 from V28-239 Pacific Ocean Deep-Core’ Andes Geophysicae Cl32 (in abstract form), EGS conf. Edinburgh, 6-10 April ‘92.