49. high-resolution magnetic susceptibility and ...-data report volume magnetic susceptibility...
TRANSCRIPT
-DATA REPORT
Barron, J., Larsen, B., et al., 1991Proceedings of the Ocean Drilling Program, Scientific Results, Vol. 119
49. HIGH-RESOLUTION MAGNETIC SUSCEPTIBILITY AND CARBONATE RECORDS:SOUTHERN KERGUELEN PLATEAU1
Wolfgang U. Dorn2
ABSTRACT
High-resolution (5-cm interval) whole-core magnetic susceptibility measurements were made during ODP Leg 119for Sites 744 and 745, located on the Southern Kerguelen Plateau. The magnetic log of Hole 744B is completed by car-bonate analyses based on tightly spaced samples (7 samples per section; approximately 20-cm intervals). Initial resultsindicate an inverse relationship between susceptibility values and percent carbonate. The data sets represent a potentialbase for within-site hole cross-correlations and global paleoenvironmental studies.
INTRODUCTION
The logging of whole-core magnetic susceptibility (WCMS)has lately become an increasingly routine part among ODPshipboard measurements. Partially this is due to the fact thatthe shipboard susceptibility meter is user-friendly and allowssimple, rapid, and nondestructive measurements of completesections at relatively narrow intervals. Magnetic susceptibility isa function of the concentration and composition of magneticcomponents within the sediment, and thus WCMS logs reflectlithological variations (with possible exceptions in the presenceof bacterial magnetite or drilling contaminations). The useful-ness of magnetic susceptibility measurements as proxy indica-tors for paleoenvironmental changes has been well established(e.g., Thompson et al., 1980; Robinson, 1986, in press; Bloemen-dalet al., 1988a).
INSTRUMENTATION AND METHODSWCMS measurements were applied on split core sections re-
covered with the advanced piston corer (APC) from Holes744A, 744B, 744C, and 745B aboard JOIDES Resolution. TheAPC-drilled sections were measured using the Bartington In-struments M.S.I susceptibility meter at high-sensitivity (0.1)and low-frequency (0.47 kHz) settings (for details see Bloemen-dal et al., 1988b; Robinson, in press). The split core sectionswere pushed manually through the Bartington Instruments 80-mm inside-diameter loop-type susceptibility sensor and mea-surements were performed successively downcore, usually at 5-cm intervals. Section boundaries (tops and bottoms), as well asobviously disturbed section intervals, were not measured. Themeasurements were stored on floppy disks on the interfacedwork-station microcomputer.
Shore-based laboratory carbonate analyses were performedon tightly spaced (7 samples per section) shipboard samples of 5cm3 volume from Hole 744B. Calcium carbonate values weredetermined by applying both coulometric and spectrometrictechniques. The freeze-dried samples were pulverized with aswing-grinding mill and measured on either a StröhleinCOULOMAT 701 LI or LECO CS 244 carbonate analyzer. To
enhance accuracy, most values represent arithmetic means ofdouble or triple individual measurements. For the presentationof carbonate percentages vs. depth plots, original sample-depthassignments have been recalculated, taking into account drill re-covery exceeding 100%.
RESULTSMagnetic susceptibility logs of Site 744 are shown in Figure
1A through 1C divided into 20-m intervals for each hole. Rela-tively higher volume magnetic susceptibility values in the upper-most sections, between about 23 and 12 m below seafloor(mbsf) apparently correspond to a major lithological changewithin each hole; at 21.60, 21.25, and 23.00 mbsf (Barron, Lar-sen, et al., 1989) in Holes 744A, 744B, and 744C, respectively, ashift occurs from mainly diatom ooze to calcareous nannofossilooze sediments. In the deeper calcareous sedimentary unit, acomparison between WCMS log and high-resolution calciumcarbonate analyses for Hole 744B (Fig. 2) reveals an inverse re-lationship between carbonate percentages and magnetic suscep-tibility values. Such a relationship is attributed to fluctuationsin the ratio of biogenic to lithogenic components: if the amountof magnetic material within the sediment is assumed to remainconstant while the supply of biogenic carbonate varies, then, asa consequence of dilution, higher carbonate percentages shouldresult in lowered susceptibility values, and vice versa. Therefore,susceptibility curve variations in nannofossil sediments of Hole744B can reflect changes in the supply of calcium carbonate, aswell as increased lithogenic input or possible carbonate dissolu-tion. Individual results of the carbonate analyses are listed inTable 1.
The WCMS profiles for Hole 745B (Fig. 3) show a pro-nounced cyclicity on a scale of 1-2 m, especially distinct in theinterval from about 50 to 100 mbsf. The sequence recovered atSite 745 consists almost entirely of diatom ooze and diatoma-ceous clay, with practically no carbonate components. The dia-tomaceous sediments are characterized by alternations of varia-bly clay-rich zones. Variations of WCMS values are thus tenta-tively ascribed to fluctuations in the ratios of biogenic siliceouscomponents and clay content.
1 Barron, J., Larsen, B., et al., 1991. Proc. ODP, Sci. Results, 119: CollegeStation, TX (Ocean Drilling Program).
2 Hawaii Institute of Geophysics, University of Hawaii, Honolulu, HI 96822,U.S.A., and Geologisch-Palàontologisches Institut, Universitàt Kiel, D-2300 Kiel,Federal Republic of Germany (present address: Geologisch-Palàontologisches In-stitut und Museum, Universitàt Kiel, Olshausenstrasse 40, D-2300 Kiel, FederalRepublic of Germany).
ACKNOWLEDGMENTSI am grateful to J. Barron and J. Baldauf for encouraging
susceptibility and carbonate measurements. J. Tauxe providedvaluable technical assistance and interest during the shipboardanalyses. S. Mühlhan and C. Hensen helped perform the car-bonate analyses.
895
DATA REPORT-
Volume magnetic susceptibility (1CT6cgs)
20 40 60 80 100 0 20 40 60 80 10020
0 20 40 60 80 100 0 20 40 60 80 10060
Volume magnetic susceptibility (10"6cgs)
0 20 40 60 80 100 0 20 40 60 80 100 0 20 40 60 80 100 0 20 40 60 80 10060
Figure 1. Volume magnetic susceptibility logs of Holes 744A (A), 744B (B), and 744C (C). Logs are divided into 20-m intervals.
896
-DATA REPORT
Volume magnetic susceptibility (10"6cgs)
0 20 40 60 80 100 0 20 40 60 80 100
0
2
4
— 6
I 8 'sz 1 0
Φ 1 2
Q14
16
18
on -
i>
I
CFigure 1 (continued).
REFERENCES
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22
24
26
28
30
32
34
36
38
40
Rnl
i I i i i i i i ic/)(
•tinsnn S T. 1986 Th
Barron, J., Larsen, B., et al., 1989. Proc. ODP, Init. Repts., 119: Col-lege Station, TX (Ocean Drilling Program).
Bloemendal, J., Lamb, B., and King, J., 1988a. Paleoenvironmental im-plications of rock-magnetic properties of late Quaternary sedimentcores from the eastern Equatorial Atlantic. Paleocβanography, 3:61-87.
Bloemendal, J., Tauxe, L., Valet, J.-P., and Shipboard Scientific Party,1988b. High-resolution, whole-core magnetic susceptibility logs fromLeg 108. In Ruddiman, W., Sarnthein, M., et al., Proc. ODP, Init.Repts., 108: College Station, TX (Ocean Drilling Program), 1005-1013.
North Atlantic deep-sea sediments revealed by mineral-magneticmeasurements. Phys. Earth Planet. Inter., 42:22-47.
in press. Applications for whole-core magnetic susceptibilitymeasurements of deep-sea sediments: Ocean Drilling Program Leg115 results. In Backman, J., Duncan, R. A., et al., Proc. ODP, Sci.Results, 115: College Station, TX (Ocean Drilling Program).
Thompson, R., Bloemendal, J., Dearing, J. A., Oldfield, F., Rummery,T. A., Stober, J. C , and Turner, G. M., 1980. Environmental appli-cations of magnetic measurements. Science, 207:481-486
Date of initial receipt: 27 November 1989Date of acceptance: 4 June 1990Ms 119B-199
897
DATA REPORT.
Table 1. Calcium carbonate percentages of all samples analyzed from
Hole 744B.
Volume magnetic susceptibility
(10 ~6cgs)
CaCO.
0 20 40 60 80 100 o 20 40 60 80 100
Figure 2. Volume magnetic susceptibility log and percent calcium car-bonate curve of Hole 744B. Carbonate curve based on analyses listed inTable 1. Comparison reveals an inverse relationship between carbonatecontent and susceptibility values.
Core, section,interval (cm)
1H-1, 0-11H-1, 16-171H-1,46-471H-1,63-641H-1, 94-951H-1, 114-1151H-1, 136-1371H-2, 0-11H-2, 16-171H-2, 46-471H-2, 63-641H-2, 94-951H-2, 114-1151H-2, 136-1371H-3, 0-11H-3, 16-171H-3, 46-471H-3, 63-641H-3, 94-951H-3, 114-1151H-3, 136-1371H-4, 0-11H-4, 16-171H-4, 46-471H-4, 63-641H-4, 94-951H-4, 114-1151H-4, 136-1371H-5, 0-11H-5, 16-171H-5, 46-471H-5, 63-641H-5, 94-951H-5, 114-1151H-5, 136-1371H-6, 0-11H-6, 16-171H-6, 46-471H-6, 63-641H-6, 94-951H-6, 114-1151H-6, 136-1371H-7, 0-11H-7, 16-171H-7, 46-472H-1, 0-12H-1, 16-172H-1, 46-472H-1, 63-642H-1, 94-952H-1, 114-1152H-1, 136-1372H-2, 0-12H-2, 16-172H-2, 46-472H-2, 63-642H-2, 94-952H-2, 114-1152H-2, 136-1372H-3, 0-12H-3, 16-172H-3, 46-472H-3, 63-642H-3, 94-952H-3, 114-1152H-3, 136-1372H-4, 0-12H-4, 16-172H-4, 46-472H-4, 63-642H-4, 94-952H-4, 114-1152H-4, 136-1372H-5, 0-12H-5, 16-172H-5, 46-472H-5, 63-64
Depth(mbsf)
0.000.160.460.630.941.141.361.501.661.962.132.442.642.863.003.163.463.633.944.144.364.504.664.965.135.445.645.866.006.166.466.636.947.147.367.507.667.968.138.448.648.869.009.169.469.509.669.96
10.1310.4410.6410.8611.0011.1611.4611.6311.9412.1412.3612.5012.6612.9613.1313.4413.6413.8614.0014.1614.4614.6314.9415.1415.3615.5015.6615.9616.13
CaCO3
(%)
16.327.333.125.735.934.27.714.925.524.728.638.241.947.150.557.159.058.657.556.760.561.067.160.164.261.658.861.561.959.159.157.255.252.154.850.138.832.822.331.934.540.337.637.543.035.621.236.339.529.427.033.133.739.732.834.324.027.039.941.340.219.526.018.423.925.126.843.312.113.213.37.84.52.32.21.40.8
Core, section,interval (cm)
2H-5, 94-952H-5, 114-1152H-5, 136-1372H-6, 0-12H-6, 16-172H-6, 46-472H-6, 63-642H-6, 94-952H-6, 114-1152H-6, 136-1373H-3H-3H-3H-3H-3H-3H-
1, 0-11, 16-171, 46-471, 63-641, 94-95I, 114-1151, 136-137
3H-2, 0-13H-2, 16-173H-2, 46-473H-2, 63-643H-CC, 1-24H-4H-4H-4H-4H-4H-
1,0-1, 46-47, 63-64
1, 94-95I, 114-1151, 136-137
4H-2, 0-14H-2, 16-174H-2, 46-474H-2, 63-644H-2, 94-954H-2, 114-1154H-2, 136-1374H-3, 0-14H-3, 16-174H-3, 46-474H-3, 63-644H-3, 94-954H-3, 114-1154H-3, 136-1374H-4, 0-14H-4, 16-174H-4, 46-474H-4, 63-644H-4, 94-954H-4, 114-1154H-4, 136-1374H-5, 0-14H-5, 16-174H-5, 46-474H-5, 63-644H-5, 94-954H-5, 114-1154H-5, 136-1374H-6, 0-14H-6, 16-174H-6, 46-474H-6, 63-644H-6, 94-954H-6, 114-1154H-6, 136-1374H-7, 0-14H-7, 16-174H-7, 46-474H-7, 63-645H-5H-5H-5H-5H-5H-1
, 1-2, 20-21, 47-48, 94-95, 114-115, 136-137
5H-2, 1-25H-2, 16-175H-2, 47-48
Depth(mbsf)
16.4416.6416.8617.0017.1617.4617.6317.9418.1418.3619.0019.1619.4619.6319.9420.1420.3620.5020.6620.9621.1321.3921.5021.9622.1322.4422.6422.8623.0023.1623.4623.6323.9424.1424.3624.5024.6624.9425.1325.4425.6425.8626.0026.1626.4626.6326.9427.1427.3627.5027.6627.9628.1328.4428.6428.8629.0029.1629.4629.6329.9430.1430.3630.5030.6630.9631.1331.0131.2031.4731.9432.1432.3632.5132.6632.97
CaCO3
(%)
0.00.90.50.40.21.50.20.00.11.02.30.45.75.96.16.04.21.92.1
67.984.60.30.00.30.10.00.20.20.30.0
63.40.5
70.270.970.872.975.182.679.071.570.579.981.181.089.280.085.681.675.075.377.279.679.286.070.588.686.370.070.678.883.682.785.788.076.174.480.879.683.788.893.589.788.090.193.089.3
-DATA REPORT
Table 1 (continued).
Core, section,interval (cm)
5H-2, 63-645H-2, 96-975H-2, 114-1155H-2, 136-1375H-3, 1-25H-3, 16-175H-3, 47-485H-3, 63-645H-3, 94-955H-3, 114-1155H-3, 136-1375H-4, 1-25H-4, 16-175H-4, 47-485H-4, 63-645H-4, 94-955H-4, 114-1155H-4, 136-1375H-5, 1-25H-5, 16-175H-5, 47-485H-5, 63-645H-5, 94-955H-5, 114-1155H-5, 136-1375H-6, 1-25H-6, 16-175H-6, 47-485H-6, 63-645H-6, 94-955H-6, 114-1155H-6, 136-1375H-7, 1-25H-7, 16-175H-7, 47-485H-7, 63-645H-7, 91-926H-1, 71-736H-1, 93-956H-1, 113-1156H-1, 136-1386H-2, 0-16H-2, 16-176H-2, 45-466H-2, 72-746H-2, 94-956H-2, 114-1156H-2, 138-1406H-3, 0-16H-3, 16-176H-3, 45-466H-3, 72-746H-3, 94-956H-3, 114-1156H-3, 138-1406H-4, 0-16H-4, 16-176H-4, 45-466H-4 72 746H-4, 94-956H-4, 114-1156H-4, 138-1406H-5, 0-16H-5, 16-176H-5, 45-466H-5, 72-746H-5, 94-956H-5, 114-1156H-5, 138-1406H-6, 0-16H-6, 16-176H-6, 45-466H-6, 72-746H-6, 94-956H-6, 114-1156H-6, 138-1407H-1, 0-1
Depth(mbsf)
33.1333.4633.6433.8634.0134.1634.4734.6334.9435.1435.3635.5135.6635.9736.1336.4436.6436.8637.0137.1637.4737.6337.9438.1438.0638.5138.6638.9739.1339.4439.6439.8640.0140.1640.4740.6340.9141.2141.4341.6341.8642.0042.1642.4542.7242.9443.1443.3843.5043.6643.9544.2244.4444.6444.8845.0045.1645.4545.7245.9446.1446.3846.5046.6646.9547.2247.4447.6447.8848.0048.1648.4548.7248.9449.1449.3850.00
CaCO3
(%)
90.195.493.788.691.783.691.590.489.189.885.888.792.488.290.184.985.583.688.683.092.883.578.275.278.078.470.870.461.773.366.070.775.580.885.185.576.688.187.387.387.986.289.585.682.785.182.988.093.194.491.392.790.883.589.790.189.591.790.592.690.795.088.591.392.692.894.995.592.792.987.692.691.690.990.792.590.0
Core, section,interval (cm)
7H-1, 16-177H-1,46-477H-1, 63-647H-1, 94-957H-1, 114-1157H-1, 136-1377H-2, 0-17H-2, 16-177H-2, 46-477H-2, 63-647H-2, 94-957H-2, 114-1157H-2, 136-1377H-3, 0-17H-3, 16-177H-3, 46-477H-3, 60-617H-3, 94-957H-3, 114-1157H-3, 136-1377H-4, 0-17H-4, 16-177H-4, 46-477H-4, 60-617H-4, 94-957H-4, 114-1157H-4, 136-1377H-5, 0-17H-5, 16-177H-5, 46-477H-5, 60-617H-5, 94-957H-5, 114-1157H-5, 136-1377H-6, 0-17H-6, 16-177H-6, 46-477H-6, 60-617H-6, 94-957H-6, 114-1157H-6, 136-1377H-7, 0-17H-7, 16-177H-7, 43-447H-7, 60-618H-1, 0-18H-1, 16-178H-1, 46-478H-1, 63-648H-1, 94-958H-1, 114-1158H-1, 136-1378H-2, 0-18H-2, 16-178H-2, 46-478H-2, 63-648H-2, 94-958H-2, 114-115
Otl-Z, 1 JU- ijl
8H-3, 0-18H-3, 16-178H-3, 46-478H-3, 63-648H-3, 94-958H-3, 114-1158H-3, 136-1378H-4, 0-18H-4, 16-178H-4, 46-478H-4, 63-648H-4, 94-958H-4, 114-1158H-4, 136-1378H-5, 0-18H-5, 16-178H-5, 46-478H-5. 63-64
Depth(mbsf)
50.1650.4650.6350.9451.1451.3651.5051.6651.9652.1352.4452.6452.8653.0053.1653.4653.6053.9454.1454.3654.5054.6654.9655.1055.4455.6455.8656.0056.1656.4656.6056.9457.1457.3657.5057.6657.9658.1058.4458.6458.8659.0059.1659.4359.6059.5059.6659.9660.1360.4460.6460.8661.0061.1661.4661.6361.9462.146D \(\Di. JU
62.5062.6662.9663.1363.4463.6463.8664.0064.1664.4664.6364.9465.1465.3665.5065.6665.9666.13
CaCO3
(%)
85.985.691.392.089.589.589.283.274.873.291.791.584.175.972.066.164.167.165.867.666.965.578.080.583.282.883.383.484.081.781.377.481.586.687.085.485.785.182.179.874.154.451.678.988.190.587.893.094.590.888.692.593.594.794.282.188.083.8Q-5 QOJ .7
80.378.884.582.569.755.877.677.982.175.869.240.252.372.078.077.578.079.4
Core, section,interval (cm)
8H-5, 94-958H-5, 114-1158H-5, 136-1378H-6, 0-18H-6, 16-178H-6, 46-478H-6, 63-648H-6, 94-958H-6, 114-1158H-6, 136-1378H-7, 0-18H-7, 16-178H-7, 46-478H-CC, 0-19H-1, 0-19H-1, 16-179H-1,46-479H-1, 64-659H-1, 94-959H-1, 114-1159H-1, 136-1379H-2, 0-19H-2, 16-179H-2, 46-479H-2, 64-659H-2, 94-959H-2, 114-1159H-2, 136-1379H-3, 0-19H-3, 16-179H-3, 47-489H-3, 64-659H-3, 94-959H-3, 114-1159H-3, 136-1379H-4, 0-19H-4, 16-179H-4, 46-479H-4, 64-659H-4, 94-959H-4, 114-1159H-4, 136-1379H-5, 0-19H-5, 16-179H-5, 46-479H-5, 64-659H-5, 94-959H-5, 114-1159H-5, 136-1379H-6, 0-19H-6, 16-179H-6, 46-479H-6, 64-659H-6, 94-959H-6, 114-1159H-6, 136-1379H-CC, 0-19H-CC, 16-17
Depth(mbsf)
66.4466.6466.8667.0067.1667.4667.6367.9468.1468.3668.5068.6668.9669.0369.0069.1669.4669.6469.9470.1470.3670.5070.6670.9671.1471.4471.6471.8672.0072.1672.4772.6472.9473.1473.3673.5073.6673.9674.1474.4474.6474.8675.0075.1675.4675.6475.9476.1476.3676.5076.6676.9677.1477.4477.6477.8678.0078.16
CaCO3
(%)
83.385.782.679.672.677.079.478.683.086.186.685.979.581.883.888.088.789.087.484.288.889.089.388.580.988.785.092.292.588.894.093.990.893.093.289.192.693.392.591.391.989.690.887.692.287.690.793.092.892.191.592.092.993.292.489.691.292.3
899
DATA REPORT-
Volume magnetic susceptibility (10"6cgs)
0 20 40 60 80 100i i i
0 20 40 60 80 100 0 20 40 60 80 100 0 20 40 60 80 10060
Volume magnetic susceptibility (10"6cgs)
0 20 40 60 80 100 0 20 40 60 80 100J I I L
0 20 40 60 80 100i i i i i i i
0 20 40 60 80 100
Figure 3. Volume magnetic susceptibility log of Hole 745B, divided into 20-m intervals.
900
-DATA REPORT
Volume magnetic susceptibility (10~6cgs)
0 20 40 60 80 100 0 20 40 60 80 100 0 20 40 60 80 100160
Figure 3 (continued).
901