53. PHYSICAL AND MECHANICAL PROPERTIES OF THE BLACK … › 42_2 › volume › dsdp42pt2_53.pdf ·...
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53. PHYSICAL AND MECHANICAL PROPERTIES OF THE BLACK SEA'S PLIOCENE QUATERNARY SEDIMENTS (Sites 380 and 381) P. N. Kuprin, F. A. Stcherbakov, A. S. Poljakov, and V. G. Shlikov, Laboratory of Marine Geology, Geological Department of Moscow University, Moscow and M. P. Nesterova, A. J. Shevchenko, N. V. Turanskaja, and V. P. Kazakova, Analytical Laboratory of P. P. Shirshov Institute of Oceanology, Moscow INTRODUCTION The Pliocene Quaternary deposits recovered by deep sea drilling in the Black Sea make up a continuous section with a clearcut transition from unconsolidated sediment to rock. Distinction between them has never been clearly defined and can be expected only from studies on a great number of sections formed in various parts of the world oceans. Above all, they should be deposits resulting from continuous ac cumulation, free of any discontinuities; the Pliocene Quaternary deposits of the Black Sea meet this requirement almost ideally. Sediment is transformed into rock as a result of internal diagenesis under the influences of biochemical and geochem ical processes, pressure, and temperature; original properties such as strength, consistency, volume weight, etc., become transformed. Study of such features, "the physical and mechanical properties," can yield much qualitative and quantitative information as to the direction and intensity of the post depositional changes in each interval of the sedimen tary series. This was the chief aim of the present research. Our investigation of physical and chemical properties was conducted on material placed at our disposal by Leg 42B Scientist Co Chief, V. P. Neprochnov (Table 1). Ten monolith samples, expressly taken at Site 381, by onboard research group member, E. S. Trimonis, were 10 cm core pieces uncut along the longitudinal axis, and treated with paraffin to preserve humidity and natural texture. In addition, 50 wet samples, with a disturbed texture, recovered from various depths of Holes 38O/38OA, were studied. Several of these samples, recovered from greater depths (approximately 200 300 m), were nearly intact, enabling a wider set of physical and mechanical properties to be investigated. LITHOLOGICAL DESCRIPTION OF THE SECTION A study of the mineralogical composition of both larger sediment particles 0.1 0.05 cm in size and clay particles smaller than 0.001 mm was made. The former were sepa rated in a heavy liquid (Table 2) and then studied in an immersion liquid. Clay minerals were studied using an X ray diffractometer with Cuα radiation at voltage Uα = 33 kv, current intensity la = 10 ma, and slit width 1; 0.5; 0.25 mm. The specimens were prepared from (a) oriented particles, (b) glycerine treated, and (c) heated to 500°C for one hour. X ray diffraction patterns of these specimens are given in Figure 1 and Table 3. The percentage of each clay mineral was com puted from the diffraction patterns after Weaver (1967). The chemical composition of several samples typical of certain lithological types of deposits was studied as well. In particular, usual analysis techniques were applied to deter mine 10 elements represented by oxides and to estimate their content in weight percentages (Table 4). For some samples which did not contain enough material, only iron, man ganese, and titanium were determined with these techniques. In some samples, also poor in material, elements were de termined by X ray fluorescence analysis. For almost all samples, the Cor g . content and the CO2 content were determined by the Knopp method. The results are given in Table 5. From the CO2 content, CaC03 was later estimated in all samples. A group of samples distributed across the whole section was subjected to an analysis of amorphous silica content, which was measured in soda extract (Table 6). Ca and Mg determinations were carried out for a number of reference samples in hot muriatic extract (HC1 2.5%). The results, in percentage of the deposit mass, are given in Table 7. Com bined results are shown in Figure 2. The larger numbers in Figure 2 are arithmetic means of the content of a component in the pertinent interval. The deposits' contents in the figure are divided into four categories. The first of these charac terizes size distribution, the second refers to the mineralogy of larger silt particles, the third describes the contents of the main clay minerals, and the fourth indicates certain important properties of the chemical composition. Although our intervals largely coincide with those tenta tively fixed by the onboard group, our data suggest a some what different assessment of the individual components' contributions. In particular, the upper part of the section (up to 300 m thick) appears to be a typical terrigenous series, perhaps more finely dispersed than originally reported. These sediments are classified as silt clay. The wide range of size distribution suggests that they most likely accumulated in a deep sea basin. The series as a whole resembles the Neo Euxinian silts, occurring at the base of the continental slope of the South Crimea. The predominance of terrigenous clay matter here (primarily hydromica) masks the biogenic components, and the series as a whole cannot be referred to as diatomaceous ooze. At 350 meters sub bottom, deposits abruptly become en riched in carbonate; the series (from 350 650 m) can be described as carbonaceous clay. 1107
Transcript of 53. PHYSICAL AND MECHANICAL PROPERTIES OF THE BLACK … › 42_2 › volume › dsdp42pt2_53.pdf ·...
53. PHYSICAL AND MECHANICAL PROPERTIES OF THEBLACK SEA'S PLIOCENE-QUATERNARY SEDIMENTS
(Sites 380 and 381)
P. N. Kuprin, F. A. Stcherbakov, A. S. Poljakov, and V. G. Shlikov, Laboratory of Marine Geology,Geological Department of Moscow University, Moscow
andM. P. Nesterova, A. J. Shevchenko, N. V. Turanskaja, and V. P. Kazakova,
Analytical Laboratory of P. P. Shirshov Institute of Oceanology, Moscow
INTRODUCTION
The Pliocene-Quaternary deposits recovered by deep-seadrilling in the Black Sea make up a continuous section with aclearcut transition from unconsolidated sediment to rock.Distinction between them has never been clearly defined andcan be expected only from studies on a great number ofsections formed in various parts of the world oceans. Aboveall, they should be deposits resulting from continuous ac-cumulation, free of any discontinuities; the Pliocene-Quaternary deposits of the Black Sea meet this requirementalmost ideally.
Sediment is transformed into rock as a result of internaldiagenesis under the influences of biochemical and geochem-ical processes, pressure, and temperature; original propertiessuch as strength, consistency, volume weight, etc., becometransformed. Study of such features, "the physical andmechanical properties," can yield much qualitative andquantitative information as to the direction and intensity ofthe post-depositional changes in each interval of the sedimen-tary series. This was the chief aim of the present research.
Our investigation of physical and chemical properties wasconducted on material placed at our disposal by Leg 42BScientist Co-Chief, V. P. Neprochnov (Table 1). Tenmonolith samples, expressly taken at Site 381, by onboardresearch group member, E. S. Trimonis, were 10-cm corepieces uncut along the longitudinal axis, and treated withparaffin to preserve humidity and natural texture. In addition,50 wet samples, with a disturbed texture, recovered fromvarious depths of Holes 38O/38OA, were studied. Several ofthese samples, recovered from greater depths (approximately200-300 m), were nearly intact, enabling a wider set ofphysical and mechanical properties to be investigated.
LITHOLOGICAL DESCRIPTION OF THE SECTION
A study of the mineralogical composition of both largersediment particles 0.1-0.05 cm in size and clay particlessmaller than 0.001 mm was made. The former were sepa-rated in a heavy liquid (Table 2) and then studied in animmersion liquid. Clay minerals were studied using an X-raydiffractometer with Cuα radiation at voltage Uα = 33 kv,current intensity la = 10 ma, and slit width 1; 0.5; 0.25 mm.The specimens were prepared from (a) oriented particles, (b)glycerine treated, and (c) heated to 500°C for one hour. X-raydiffraction patterns of these specimens are given in Figure 1
and Table 3. The percentage of each clay mineral was com-puted from the diffraction patterns after Weaver (1967).
The chemical composition of several samples typical ofcertain lithological types of deposits was studied as well. Inparticular, usual analysis techniques were applied to deter-mine 10 elements represented by oxides and to estimate theircontent in weight percentages (Table 4). For some sampleswhich did not contain enough material, only iron, man-ganese, and titanium were determined with these techniques.In some samples, also poor in material, elements were de-termined by X-ray fluorescence analysis.
For almost all samples, the Corg. content and the CO2content were determined by the Knopp method. The resultsare given in Table 5. From the CO2 content, CaC03 was laterestimated in all samples.
A group of samples distributed across the whole sectionwas subjected to an analysis of amorphous silica content,which was measured in soda extract (Table 6). Ca and Mgdeterminations were carried out for a number of referencesamples in hot muriatic extract (HC1 2.5%). The results, inpercentage of the deposit mass, are given in Table 7. Com-bined results are shown in Figure 2. The larger numbers inFigure 2 are arithmetic means of the content of a componentin the pertinent interval. The deposits' contents in the figureare divided into four categories. The first of these charac-terizes size distribution, the second refers to the mineralogyof larger silt particles, the third describes the contents of themain clay minerals, and the fourth indicates certain importantproperties of the chemical composition.
Although our intervals largely coincide with those tenta-tively fixed by the onboard group, our data suggest a some-what different assessment of the individual components'contributions. In particular, the upper part of the section (upto 300 m thick) appears to be a typical terrigenous series,perhaps more finely dispersed than originally reported.These sediments are classified as silt-clay. The wide range ofsize distribution suggests that they most likely accumulatedin a deep-sea basin. The series as a whole resembles theNeo-Euxinian silts, occurring at the base of the continentalslope of the South Crimea. The predominance of terrigenousclay matter here (primarily hydromica) masks the biogeniccomponents, and the series as a whole cannot be referred to asdiatomaceous ooze.
At 350 meters sub-bottom, deposits abruptly become en-riched in carbonate; the series (from 350-650 m) can bedescribed as carbonaceous clay.
1107
P. N. KUPRIN ET AL.
TABLE 1List of Samples Studied From Holes 380/380A and 381
Core
Hole
04579
1113151720222325272933363839
Hole
578
1012141618202226293336404345485256606671
Section
380
CC
ccccccccccccccccccccmop.CC
cccccccccccc
380A
CC
ccccccccccccccccccccccccccccccmop.CC
cccccccccc
Site 381
79
1013141922263133
ccmop.CC
ccmop.mop.CC
cccccc
ConditionDepth of the Sample
Below Sea NotFloor (m) Deformate Deformate
9.5 +38.0 +47.5 +66.5 +85.5 +
104.5 +123.5 +142.5 +161.5 +190.0 +209.0 +209.5 +237.5 +256.5 +275.5 +313.5 +342.0 +361.0 +370.5 +
380.0 - +399.0 +408.5 +427.5 +446.5 +465.5 - +484.5 +503.5 +522.5 - +541.5 +579.5 - +598.5 +636.5 +665.0 - +703.0 - +731.5 +741.0 - +778.5 - +817.0 - +855.0 - +893.0 +950.0 +997.5 - +
66.5 - +76.0 - +95.0 - +
123.5 - +124.0 - +171.0 - +199.5 - +237.5 - +285.0 - +304.0 - +
TABLE 2Percentage Content of Heavy and Light Minerals
in the 0.1-0.05 mm Fraction
In deeper horizons the deposits differ in that diageneticprocesses are more strongly pronounced, as expressed in aheightened pyritization and in irreversible aggregation ofclay particles, which affects the granulometric composition.Zeolites, which we believe to be authigenic, support thiscontention. Further, below 700 meters, biogenic components
Core
Hole04579
111517202223252729363839
Hole578
1012141629222629334043485256606671
Weightof the
Fraction0.1-0.05
380
0.60890.18350.76080.02540.01120.03751.31880.03380.07260.00530.08200.34430.03020.01160.16410.43450.0322
380A0.04290.15080.05340.62050.22570.01330.00820.02010.00490.17660.03700.01200.00790.05800.05190.07590.08470.18000.03480.0371
Site 3819
101314192631
0.11020.00460.21950.03130.10660.03440.2147
Weightof theHeavy
Minerals
0.00420.00850.03370.00070.00090.00060.02550.00090.0012ea. 3H.0.00270.0085ea. 3H.0.00020.00370.01650.0099
0.00200.00500.00120.01500.01340.00170.00060.00260.00140.00350.00860.0033ea. 3H.0.00190.00140.00110.0015ea. 3H.ea. 3H.ea. 3H.
0.0024ea. 3H.0.00710.00130.00730.00200.0012
Weightof theLight
Minerals
0.60470.17490.72710.02470.01030.03691.29330.03290.0714
0.07930.3358
0.01140.16040.41800.0223
0.04090.14580.05220.60550.21230.01660.00750.01750.00350.17310.02840.0087
0.05610.05050.07480.0832
0.1078
0.21240.03000.09930.03240.2135
Percentageof theHeavy
Minerals
0.694.694.432.768.041.601.932.661.65
3.292.47
1.722.253.80
30.75
4.663.322.252.425.94
12.787.32
12.9428.58
1.9823.2427.50
3.282.701.451.77
2.18
3.234.156.855.810.56
Percentageof theLight
Minerals
99.3195.3195.5797.2491.9698.4098.0797.3498.35
96.7197.53
98.2897.7596.2069.25
95.3496.6897.7597.5894.0687.2292.6887.0671.4298.0276.7612.50
96.7297.3098.5598.23
97.82
96.4795.8593.1594.1999.44
increase, primarily diatoms yielding both amorphous silicaand organic matter in individual layers, resulting most prob-ably from lesser accumulations of terrigenous material.
Our detailed lithological study suggests that the upper300-350 meters of Site 381 conforms in age and compositionto the 300 meters of upper terrigenous material at Holes380/380A.
Deposits in the lower part of Site 381 seem to have ac-cumulated as a result of slope processes. Because discon-tinuities are probable, if not recognizable in them, we virtu-ally disregarded them in the analysis of physical and mechan-ical properties.
1108
PHYSICAL AND MECHANICAL PROPERTIES
14.25 A
HOLE 380COREOCC
3.33 A
HOLE 380ACORE 40CC
3.24A
3.34 A Zeolite-Quartz
8.93 A
Figure 1. X-ray diffractograms of'the fraction less than 1 µmfrom sediments at Holes 380/380A.(A) oriented preparation; (B) with glycerine; (C) heated to 550°C.
1109
P. N. KUPRIN ET AL.
TABLE 3Percentage Composition of Different Clay Minerals(< 1 µm Fraction) From Holes 380/380A and 381
Hole
380380380380380380380380380380380380380A380A38OA380A380A380A380A380A380A380A380A380A381381381381381381381381381381
Core
0479
1115172227333639
58
14202629364045 mop526671
79
1013141922263133
Illite
64545563605057556057564851425351463842365 246523054814259464942414047
Composition (%) Clay Minerals,
Montmoril-lonite
1010
89
121215121630161411181211161316131940212611
913113311191913U
Mixed-LayerMinerals
102325131323152011_
3024262722253040304220
J .
203722153316
92830304030
Fraction < 1
Kaollnite
5456b7556546597
6368459455695544544
=µm
Chlorite
1197
988878487467534545328939785545
PHYSICAL AND MECHANICAL PROPERTIES
Despite attempts at unification (Inderbitzen, 1974; andothers), so far there is no unique approach to or strictlyelaborated techniques for determination of properties ofsedimentary units. It seems appropriate, therefore, to go intosome detail and describe the methods we have used.
The granulometric composition of all samples was deter-mined, using the conventional technique based on the parti-cles' settling rate in distilled water. To achieve the completedispersion of the specimen being prepared for analysis, a wetweighted amount was triturated in 6% sodium pyrophosphatesolution. Apart from standard granulometric fractions, thepercentage of under 0.22 µ colloid particles was computed.Such ultra-granulometric analysis was carried out for all the10 samples from Site 381 and for 24 samples from Site 380and Hole 380A. The results are given in Table 8.
According to the Institute of Oceanology classification, allSite 381 deposits are clay ooze (more than 70% of under0.01-mm particles). The 0.001-mm fraction accounts for atleast 45% and, sometimes 80%. Cores 13 and 33 wereexceptions; under the polarizing microscope, these samplescontained much carbonate. The maximum dispersity wasobserved in brownish or brown terrigenous ooze (Core 10),which contained 80.18% of clay particles (under 0.001 mm),and in diatom-sapropel deposits (Cores 22, 26), which con-tained 63.17% and 66.74% of clay particles. The ultra-granulometric investigation showed an average 50% of Site381 clay fraction to be colloid particles (under 0.22 µ. Theabsolute content of colloid particles in these samples variedfrom 14.53% to 47.03%. The maximum values were ob-served in high-clay deposits, i.e., colloids increased withrock dispersity. Yet, the relative content of under 0.22 µparticles did not always correlate with the sample's disper-
sity. For example, a lowered colloid content expressed aspercentage of the clay fraction (37% to 48%) was observed inhigh-dispersed clays with a heightened diatom skeleton con-tent (Cores 22-31), whereas the colloid maximum (64%) wasestablished in a terrigenous ooze sample (Core 14) containingfar less under 0.001 mm particles.
From Table 8 it is seen that only four samples (Cores 0,4,15, and 36) from Site 380 are silt-clay ooze. The clay fractionin silt-clay deposits varies between 22.39% and 35.76%.
Apart from the investigations described above, a specialmethod of granulometric analysis was used on all samples toassess the structure of the deposits. This was the so-calledmicro-aggregate analysis, which differs from the standardgranulometric method by specimen preparation. A wet-weighted amount was put into a 0.5 1 vessel with one-fifthdistilled water, and agitated for 2 hours. Subsequent fractio-nation was carried out as described above. A comparison ofthe results of granulometric and micro-aggregate analysisprovides a notion of the deposits' natural dispersity andaggregation. Aggregation was estimated by Kagr,the ratio of acertain fractions content (as estimated by granulometricanalysis) to its content (as estimated by micro-aggregateanalysis). Two aggregation ratios were calculated: one forthe less than 0.001 mm fraction (Ko.ooi) and the other for theless than 0.005 fraction (Ko.oos). The results are shown inTable 9, which shows that practically in all Black Sea de-posits, small aggregates less than 0.001 mm in size arepresent (Ko.ooi>l). Larger aggregates (Ko.oos>l) are mostlytypical of diatom-containing deposits, where they usuallyreach sand size dimensions. Larger aggregates resistant in awater medium are usually recorded in the lower part of thesection: Core 31, Site 381, and especially Cores 40-71, Hole380A. A higher Ko.oos is observed in some carbonate-enriched samples (Cores 13 and 33, Site 381; Core 33, Site380).
PHYSICAL PROPERTIES
We have grouped an important set of data on sediment androck properties under the general name of ' 'physical proper-ties." These include humidity, plasticity, specific weight,volume weight for various states of the sample, porosity, andsound propagation velocity in various directions (Table 9).Physical properties were studied in samples of disturbed andundisturbed structure.
Humidity
Natural humidity (We,%) was estimated as the water masscontained in the sediment or rock relative to the sediment orrock mass dried at 100°- 105°C to a constant value (expressedas percentage). The water content in a deposit depends on thegranulometric composition, dispersity, mineralogical com-position, and organic matter content of the sediment. A highnatural humidity, even at great depths, is associated with ahigh content of clay particles (<O.OOl), including muchmontmorillonite and mixed-layer units.
Plasticity
In comparing plasticity limits with natural humidity, acharacteristic of the deposits consistency is obtained. Claydeposits pass from one consistency form into another atcertain humidity values, referred to as characteristichumidities or limits.
1110
PHYSICAL AND MECHANICAL PROPERTIES
TABLE 4Chemical Composition of the Sediments From Holes 380/380A as Determined by
X-Ray Fluorescence Analysis
Core
Hole
513152022232527293336385-47-4
Hole
578
101214161822333643454860667580
Horizon
380
CC
29-4185-93
3 80 A
14-2931-47
SiO2
48.149.252.548.853.050.350.426.848.849.247.852.155.350.5
49.238.349.948.749.527.021.430.920.234.455.453.552.233.824.322.551.654.2
TiO2
0.480.680.600.660.700.680.680.292.780.630.550.690.660.57
0.730.510.650.620.550.260.240.320.200.370.750.400.360.440.260.260.790.74
A12°3
11.9517.512.415.915.515.316.18.92
15.115.312.416.614.312.9
17.212.416.114.013.59.148.85
10.57.23
11.316.811.810.016.87.957.0
15.715.4
Fe2O3
5.826.455.07.356.146.727.108.386.466.476.605.855.875.05
7.467.467.475.946.287.966.786.969.235.807.804.859.253.004.584.506.956.67
MnO
0.100.060.100.080.290.110.110.080.130.150.090.100.100.09
0.090.120.040.080.100.120.120.040.120.100.040.050.330.050.110.040.070.20
Percentage
MgO
3.153.144.052.853.443.612.752.473.282.682.863.303.744.35
2.752.912.132.933.402.352.371.951.532.061.871.701.662.384.517.052.413.27
CaO
9.605.579.407.704.946.826.252.408.057.957.886.404.958.15
4.4316.15.379.959.00
24.328.722.029.920.50.626.317.20
22.626.625.6
3.554.52
K2O
2.183.182.062.892.462.592.730.752.622.572.013.022.312.23
3.181.322.562.122.090.410.300.710.530.782.251.281.480.660.600.492.552.23
No2O
1.291131.290.821.351.281.271.511.251.271.790.951.321.53
2.532.271.441.952.412.352.312.451.602.451.882.522.042.372.082.441.741.94
P2°5
0.150.120.190.150.100.150.120.070.140.160.200.160.180.15
0.110.140.140.130.130.130.090.100.150.150.090.080.170.120.130.080.110.10
Lo.i
17.2012.2512.2013.1012.1212.312.526.813.513.617.310.7510.413.7
11.6217.5513.813.413.226.228.724.230.121.811.817.615.223.228.930.213.911.1
The upper plasticity limit (Wf,%),or the humidity percen-tage at which the deposit passes from plastic to liquid, wasmeasured using a cup. The lower plasticity limit (Wp,%),orthe humidity percentage at which the deposit passes fromplastic to solid, was measured by rolling out the specimen to astring until fissures first appeared. The difference of Wf andWP gave the plasticity number (MP). Site 380 data show thenatural humidity to be above the upper plasticity limit downto a depth of 40 meters, the deposits being in the latent fluidstate. At the depth of 250 to 300 meters the natural humidityis a few percent above the lower plasticity limit, falling belowit at about 500 meters where the deposits are no longerplastic. For several samples, the hygroscopic humidity(Wh,%) was computed as the difference between total andnatural humidity.
From plasticities, the consistency index was computed as
Specific Weight
Compaction K
K =
B =VWp
Clay deposits are divided by this value (Table 10).
was also computed.The specific gravity (y,g/cm3) was measured in paraffin oil
in a density bottle. Paraffin oil was used to prevent dissolu-tion of salts from the sample which might distort the results.Only data for monolithic samples from Site 381 were ob-tained (Table 1).
Volume WeightThe wet unit weight of the natural samples ( ,g/cm3) was
measured using 10 cm3 rings. Only monoliths from Site 381were investigated. For Holes 38O/38OA, onboard data wereused. Compaction and density of the deposits have beenfound to depend heavily on the composition. For example,the volume weight increase in the 300 to 700 meter interval is
1111
P. N. KUPRIN ET AL.
TABLE 5CO2 and C o r g a n i c (Knopp's Method)in Sediments From Holes 380/380A
Core Horizon
Hole 380
04
5-45
7-4799
11131517202223252729353636, CC3839
28.5-38.029-41
38.0-47.585-93
57.0-66.576.0-85.576.0-85.595.0-104.9
114.0-123.0133.0-142.5152.0-161.0180.5-190.0199.5-209.5209.0-218.5
—247.0-256.5266.0-275.5304.0-313.5323.0-323.5
351.5-361.0
Hole 380A
577.,8
101214i6182022262933364043454852566066CC717580
375.0-380389.5-399.0389.5-399.0399.0-408.5418.0-427.5431.0-446.5456.0-475.5475.0-484.5494.0-503.5573.0-522.5532.0-541.5570.0-579.5593.0-598.5631.0-636.5655.5-665.0693.5-703.0722.0-731.5741.0-750.0769.5-779.0807.5-817.0845.5-855.0883.5-893.0945.0-950.0
988.6-997.514-2947-65
co2
7.405.954.146.754.627.118.208.203.724.157.326.507.104.015.144.20
19.856.886.156.374.245.61
27.72
3.2011.2511.15
3.707.007.19
21.0723.0016.900.52
16.5116.0013.4715.300.200.175.909.50
15.3019.584.25
21.4023.3516.35
3.893.863.21
Corg
0.470.620.681.001.761.640.450.491.910.590.600.670.410.940.720.490.520.540.992.325.230.460.82
0.440.680.700.760.520.360.540.640.650.800.540.640.780.911.641.432.291.531.601.26
13.681.322.131.881.741.131.58
TABLE 6S i 0 2 amorphous Content in
Sediments From Holes380/380A
Core
Hole
04579
1113151720222325272933363839
Hole
578
10121416161820222629333640434548525660667171
Horizon
380
28.5-38.038.0-47.552.0-66.576.0-85.595.0-104.9
114.0-123.0133.0-142.5152.0-161.0180.5-190.0199.0-209.0209.0-218.5
247.0-256.5266.0-275.5304.0-313.5323.0-323.5
351.5-361.0
380A
375.0-380.0389.5-399.0399.0-408.5418.0-427.5437.0-446.5456.0-465.5475.0-484.5
494.0-503.5513.0-522.5532.0-541.5570.0-579.5593.0-598.5631.0-636.5655.5-665.0693.5-703.0722.0-731.5741.0-750.0769.5-779.0807.5-817.0846.5-855.0883.5-893.0945.0-950.0988.6-997.5988.6-997.5
SiO2
amorph
0.801.002.102.000.621.420.920.800.940.841.841.581.000.700.621.961.160.560.66
0.901.181.321.001.001.041.061.041.261.440.800.941.261.144.365.728.309.643.684.683.920.901.161.341.30
linked with a coarser composition and a carbonate enrich-ment of the deposit. Still, a general increase of the rocks'volume weight with increasing depth is traceable.
From the volume weight of the wet undisturbed sampleand from natural humidity, the dry unit weight of the sample(δ,g/cm2) was computed, or the volume weight of the undis-turbed sample whose pores are filled with air. The expressionused was
δ =1+ 0.001 W.
Porosity
The porosity (n%) was computed using the expression
7-δn - 100%
Only data for Site 381 monoliths were obtained. Porosity wasestimated by sample humidity, assuming that all the pores arefilled with water. A comparison of porosity values computedby the two methods showed for the sediments concerned(upper part of Site 381) the humidity-based porosity to bemuch lower than that based on specific and volume weight.This suggests that much of the pore space in the sediments of
1112
PHYSICAL AND MECHANICAL PROPERTIES
Depthbelow
sea floor
Sediments'sdescription in thepreliminary report
Content of the same fractionsof the sediment (%)
0.1-0.05 <0.01mm
< 0.001mm
<0.22MKM
Kagr< 0.005
Composition of theparticles 0.1-00.5 mm ('
Kfeld-spar
FeS- Zeolites
Phosfrag.
Mineralogical compositionof the particles < 0.001 mm(%)
Illite MontMixedlayer
Chlor Zeolites
Some biogenic andchemogenic components (%)
C org CaCOJ MgO*
100-
200-
300-
400-
500-
600-
700-
800-
900-
1000-
1100-
-1200
Terrigeneous mudDiatomaceous mudSandy siltturbidites
24 73 32 15.4 1.3 31
Diatomaceous mudDolomitic marl
Calcareous ooze,varve, mud, marl 91 52 26.4 1.1
28 26
46
52 12 16 81.5
1.7 0.8
48 14 26
Slumping blockcalcareous material
57213
1.91.82
451.5
0.8 32
1.6
1.4
Diatomaceous clay,varve, marlCarbonate varve
29 21 74 43 15 31 3.20.7
2913.7 TIT
0.7Pebbly breccia
Laminated shalesCarbonate varve,marl, dolomite-richblack shales
12 86 30 13 4.33.3
5.0
0.60.87.90.61.6
1.2 1.7—6—
8.7
*SiO2
amorph
*Hclextracted
Figure 2. Changes in the content of some main components of Black Sea sediments, (a) large numbers represent averagecontent of component; (b) small numbers represent maximum content at certain horizons.
TABLE 7CaO and MgO (2.5% HOExtract) Content From
Holes 380/380A
Core CaO
Hole 380
513152022232527293338
Hole
578
1012141618223333364345454860
8.404.987.526.404.285.645.20
24.206.546.845.36
380A
3.8514.004.828.268.20
25.4529.3622.0830.4418.8018.860.605.746.426.38
19.4826.30
MgOHC1 extract
1.901.762.171.781.841.961.391.242.051.711.50
1.581.880.971.921.901.281.401.051.481.351.340.720.700.790.740.672.52
these horizons is filled with gas. The difference of the twoporosities falls to a minimum beginning from the depth of250 meters (Core 26, Site 381). For older deposits (fromHole 380A), only humidity-based porosity was estimated;for this, skeleton volume weight measured onboard and ournatural humidity measurement were used. On the basis ofporosity, the index of filtration (e) was computed for Site 381monoliths.
Sound Velocity
Sound velocity (VP, m/sec) was measured only in Site 381monoliths (Table 11); the sound wave propagation was inves-tigated both across (VP) and along (VP) the beddingplane. Ultrasonic seismoscopes with frequencies from 50 to100 kHz were used on samples 10 to 1 cm long. Given thevolume weight of wet ground ( ,g/cm3) and longitudinalwave velocity in it (VP), we computed the horizon's acousticstiffness (Δ VP) and the index of reflection
We have measured the sound velocity in natural samplesartificially compacted with a load of 1.5 kg/cm2.
Sound velocity thus grows after compacting the sample.If, before compacting the sample, water is strained through itunder the pressure of up to 30 (gradient), the sound velocitygrows nearly fourfold against that in the initial natural sam-ple. Compaction without straining raises the sound velocity amere twofold. Evidently, water strained at a pressure (up to30 gradient) removes more gaseous phase from the depositthan mere compaction can do. Gas in sediments not onlyreduces the sound velocity, but brakes their compactionduring subsidence.
1113
TABLE 8Grain-Size Distribution of the Sediments From Holes 380/380A and 381
CoreType ofAnalysis
Hole 380
0
4
7
9
11
15
17
22
27
33
36
39
Hole5
8
14
20
26
29
36
40
45
52
granulometricalmicroagregategranulometricalmicroagregategranulometricalmicroagregategranulometricalmicroagregategranulometricalmicroagregategranulometricalmicroagregategranulometricalmicroagregategranulometricalmicroagregategranulometricalmicroagregategranulometricalmicroagregategranulometricalmicroagregategranulometricalmicroagregate
380A
granulometricalmicroagregategranulometricalmicroagregategranulometricalmicroagregategranulometricalmicroagregategranulometricalmicroagregategranulometricalmicroagregategranulometricalmicroagregategranulometricalmicroagregategranulometricalmicroagregategranulometricalmicroagregate
> lmm%
_-----
------------
2.232.062.29--
_---—---—-—_---
7.61-
8.22_
12.26
1-0.5%
_-----——-—--———
2.07--—
2.234.115.26--
_————--——————--
1.88-
1.70—
4.67
0.5-0.25%
-------
------
2.22---
2.226.016.19
--
_—-------———_-_
1.50—
1.23-
3.66
0.25-0.1%
1.211.564.134.651.101.490.27—
0.891.303.142.550.450.930.106.86-
0.530.244.516.507.222.442.84
1.331.537.25
10.290.711.200.441.840.280.560.560.920.532.810.332.350.831.831.396.95
Analytical Data0.1-0.05
%
9.5911.623.544.171.313.380.580.641.204.10
20.8820.430.922.480.376.940.161.000.337.966.028.900.700.67
0.580.921.802.000.300.470.631.53-
0.200.490.850.651.420.631.830.551.132.724.10
0.05-0.01%
27.2726.8828.0228.65
5.5815.6528.1222.6211.7918.2629.3929.4922.8625.1611.9524.1115.3216.3615.9531.3227.4832.09
2.636.52
4.496.323.760.735.532.73
10.3711.3715.1317.137.526.374.602.744.336.306.458.97
11.7312.40
0.01-0.005%
9.477.867.925.189.58
69.9310.7511.799.30
26.389.23
12.3711.3515.9212.6315.6921.3224.0511.7916.006.909.11
25.0029.31
6.594.961.271.45
11.6013.086.666.80
15.2816.9711.93
12.721.044.255.83
12.0629.2364.5515.9525.55
0.005-0.001%
24.6337.6820.6338.9632.93
4.9728.3958.1329.9144.8014.9731.3026.5550.5633.5024.3533.5534.9832.0227.1317.8017.5948.5643.50
36.8139.5716.5218 6944.0348.8230.6534.2329.1057.9035.4042.4930.7328.2032.7927.6729.306.58
39.2924.79
< 0.001%
28.1314.4035.7618.3941.37
4.5831.896.82
46.915.16
22.393.86
37.874.95
41.4517.7629.6523.0839.676.40
23.1211.3520.6717.16
50.2046.7069.4066.8437.8333.7051.2544.2340.21
7.2444.1036.6563.2360.5856.0938.8033.645.79
28.925.62
< 0.22µmµ%
10.36
16.10
21.13
14.95
18.23
12.34
19.77
19.40
13.71
18.18
12.02
8.74
23.38
43.39
18.54
22.46
20.87
22.36
32.41
27.86
14.98
13.37
Calculatal Data
Content ofthe particles
<0.22µminthefraction < lµm
37
45
51
47
39
5
52
47
46
46
52
42
47
63
49
44
52
51
51
50
45
46
K agreg.for parti-cles < lµm
1.95
1.94
9.03
4.68
9.09
5.80
7.65
2.33
1.28
6.20
2.04
1.20
1.07
1.04
1.12
1.16
5.55
1.20
1.04
1.45
5.81
5.15
< 0.005mm%
52.7652.0856.3957.3514.30
9.5560.2864.6576.8249.9637.3635.1664.4255.5174.9542.1163.2058.0671.6933.5340.9228.94
69.2360.66
87.0186.2785.9285.5381.8682.5281.9078.4669.3165.1478.5079.1496.9688.7888.8866.4762.9412.3768.2130.41
K agreg.for parti-cles <5µm
1.01
1.00
7.78
1.00
1.54
1.06
1.16
1.78
1.09
2.14
1.41
1.14
1.01
1.00
1.00
1.04
1.06
1.00
1.10
1.34
5.09
2.24
KU
PF
WH>
PHYSICAL AND MECHANICAL PROPERTIES
O
00 0
co c
(Nq
1 00 u
oq o
so
oo oo oo oo ON ON SO
COSO00
co
r-
q
so
oCO
oq
z> oo r
D 00 0
m
IO
q
-» r» c-) rf *-
TJ-
O
CO
r\ σ\ e
fs oo r
lθ
so
00
*1^H
0 TJ• C
- fS f
o ON r
ooso
coCO
IO
ONCO
ff> VO M 5\CO <O σ•i Oo ò •<fr ON f^
<N oo ro •<toò ö rò ON
o t-~
CO rj• CO SO
I °) I - 1
TtTj•-Hooocooor—•^•ONiooo•<a•sor~-oooooot~-
C1^ t,~] ^ f f/ T—i Cf\ ^H ^H ^Q CO \Q ^^1 f «• r*»» ^H QQ f" . 1/^ i H ^J"
f S r*— f θ \ Q T-H O*\ (y^ fNj
t 5 O^ ^N O^ ™ co 00 ^ c^
r^ cn rs <N ^H <N rö
00 ^D ^D •J" i • f *O ^^ "^ • " t*** <N C l CS ^O '" & t • *--* 00• I
c^i >o ^o ^^ r o r* i p r**- ^^ ^H ^ \ f > f• • f*««, ^^ •*^ (—) fv) i/^r***• c^ r^ • c^ *™H r**~ oo t o ~ c * co c^ vo c* ov ^o r * ^o r***
o - ö « d '
I I l < n MI I I I I I I I I I I
I I I I I I I I I I
I I I I
o <u u α>
JS Λ ^ cβ60
ε «oo
9? <u ^ < u ^ i > S?<o S ^ t j ° θ a j 6 0 ^ ö ß • J 60
M ) § 6 θ 5 6 0 § 6 θ g 6 θ g 6 θ 5 6 0 § 6 0 § 6 0• 3 θ 3 o " 3 θ 3 o • 3 θ 3 o 3 o 3 o 3 o 3 o
2 .H § .a I .a § .a § .H « .a § .S § S 2 S § •§M H i i i i c « i i E i > o S M C i i i ) E s i i C M E a i i E i ! i ) ε
Filterability was measured in more samples than thosetaken for sound propagation measurement. For two Site 381monolith samples it was measured experimentally, using adevice for investigation of compression properties. A ringholder with the sample, 2 cm high and 25 cm2 in section, wasplaced under a piston, locked in a fixed position. Water wasfed into the sample from below. The pressure gradient variedfrom 0 to 30. The time of the lowering of the water level in thefeeder vessel was registered. Standard formulas were thenused to compute the filterability (Table 12).
MECHANICAL PROPERTIES
Another major group of sediment and rock qualities com-prises data referred to as " mechanical properties.'' These areindicators characterizing a sample's response to variousmechanical actions. The core of this group of properties ismade up of various strength indicators (Table 13).
Measured were: compressive strength (δ, kg/cm2), severalalternatives of shear strength (7, kg/cm2), and plastic strength(Pm, kg/cm2).
In addition, the samples were subjected to compressionand deformation tests.
The plastic strength (Pm, kg/cm2) was measured using acone (which had the angle of 45° for loose deposits, and 30°for denser deposits) on the Rebinder plastometer and on thedevice described by Amelina and Shchukin (1970). It wasmeasured both for the force directed normally and for thatparallel to the bedding plane. The ratio of the two values gavethe anisotropy coefficient (Kanis).
In order to measure the shear strength with the two-planeshear method, parallelepipeds of 1 cm2 square cross-section(S) and a length (1) of 2.5-3.0 cm were cut out of themonolithic samples (Site 381). A 1 cm2 punch was used toeject a cube from the sample. In this manner, the two-planeshearing was performed. The force applied to the punch wasfed through a spring to the recorder, which traced the curveshowing the variation of deformation (ΔL) relative to thepressure (P). From these curves (Figure 3), the maximumshear stress (r max, kg/cm2) and the minimum steady shearstress (T min, kg/cm2) were computed according to the expres-sion
T =•
2S
r max was measured both parallel (T max | | ) and normal (r max 1)to the bedding plane. The ratio of the two values, r maxi/rmax II , characterizes the deposit's anisotropy. The unconfinedcompression (σ,kg/cm2)was measured on the same device,but using a different sample shape, i.e., 20-25 cm high and10-15 cm across. The measurement procedure was the sameas above. Compressive stress was computed as
The stress which destroyed the sample was taken to be thecompressive strength. It too was measured on the forceparallel and normal to the bedding plane. From the shearstress and the axial compression, the elastic modulus, E
1115
P. N. KUPRIN ET AL.
σ.T. kg/cm2
1.0
0.5
1.0
1.0
0.5
2.0
1.5
1.0
0.5
1.0
0.5
2.0
1.5
1.0
0.5
381-7-CC-66.5
2 3
381-9-TOP-76.0
1 = 19.6 mm-£= 1C)~9mm
381-10-CC-95.0
••"£ = 19.7 mm
£=10.6 mm
381-13-CC-123.5
L = 19.7 mm
L = 10.2 mm
2 3
381-14-TOP-124.0
L= 10.3 mm L = 22 mm
2 3
381-19-TOP-171.0
£ = 22.1 mm
• L= 10.2 mm
1 2 3
381-22-CC-199.5
... L= 19.6mm
L= 10.1 mm
i i i
1.5
1.0
0.5
102
1.5
1
0.5
381-26-CC-237.5
L = 19.5 mm
•£=10.0 mm
2 3
381-31-CC-285.0
L = 19.7 mm
L= 10.4 mm
2 3
381-33-CC-304.0
•L= 19.0 mm•L= 10.0 mm
The deformation's curvesof the samples from Sites381 and 380A
= 1 ; = 2;
T,kg/cm2 = 3; σ,kg/cm2 = 5;
£,mm = 4; i , m m = 6.
380A-5-CC-380.0
£ mm
L= 18.5 mm
i i i i
13
14
15
380A-20-CC-522.5
9.6 mm
2 3
380A-26-CC-579.5
£ = 9.8 mm
2 3
381A-40-CC-783.0
L= 10.4 mm
Figure 3. Shear test information curves of samples from Site 381 and Hole 380A. (1) solid curve showing relation betweenshear stress and absolute deformation; (2) dotted curve showing relation between compressive stress and absolute defor-mation; (3) shear stress (T) in kg/cm?; (4) length of sample (L) in mm; (5) compressive stress (a) kg/cm^; (6) absolutedeformation (&) in mm.
was computed, where 1 is the deformation ratio 1
4r2 - n
The period preceding the shear was regarded as the process ofthe sample's elastic deformation under compression.
In attempting to elucidate the nature of the strength proper-ties of the Black Sea deposits under investigation, weemployed the data of analyses to evaluate the strength of theindividual contact between particles (Pi, dynes). The evalua-tion was based on the globular model of a dispersed porousbody proposed by Shchukin et al. (1970). On this model, thestrength of the individual contact between particles isPi = Pc/X where Pc is the tensile strength estimated as
P = σG+10"
where r is the radius of the particles, or micro-aggregates,which, by way of convention, are assumed to be spherical,and n is the sample's porosity.
According to the globular module, the individual contact isconsidered coagulative a t l 0 5 < P i < 1 0 3 dynes, conden-sative at 10 4 < Pi < 10 2 and crystallizing at Pi > 10 2
dynes.The investigation of the deformation properties of Site 381
deposits included measuring the volume variation of thesample drying under natural conditions. A ring (h = 2.8 cm,d = 1.5 cm) was used to cut out of the monolith a sample of agiven volume Vi. The sample was dried out at room tempera-ture, and its volume, V2, was measured. The volume shrin-kage was computed as
Here σ is the compressive strength, and the divisor is con-nected with the sample's plasticity; x is the number of con-tacts per cross-section unit, estimated from
v r v 2 100.
1116
PHYSICAL AND MECHANICAL PROPERTIES
TABLE 9Physical Properties of Sediments From Holes 380/380A and 381
Core Horizon
Hole 3S0
04579
11
1315172022
2325272933363839
0-9528-3838-47.557-66.576-85.5
95.0-104.5114-123133-142.5152-161
180.5-190199.5-209
209-218.5228-237.5247-256.5
266.0-275304-313.5323-332342-351
351.5-361
Hole 380A
578
1012141618202226293336404345485256606671
375-380389-399399-408413-423437447450-466475-485494-504513-522532-542570-580593-599631-637656-665694-703722-732741-754770-779808-817846-855884-893945-950988-998
Site 381
79
1013141922
26313333
57-66.576-85.5
855-950114-123.5
123.5-133171-180.5195-199.5223-237.5275-285.0264304
We
(%)
53.9953.3845.9157.1038.4343.8940.4930.7530.4433.9739.2041.6346.2128.0127.0426.4038.3230.7444.55
30.0830.3847.9332.5528.1331.0428.5428.3327.9424.1326.5433.1332.5138.9750.2948.6431.6534.1929.1444.5923.8030.9623.55
49.4646.7151.5728.2139.4743.1454.1361.3950.8441.6939.98
Wt
(%)
40.3852.8358.5271.0447.6666.4154.9534.5048.0047.0756.8843.8952.9946.0343.2659.9547.9637.7146.77
54.3848.0556.4142.9242.9146.5344.8845.0556.5248.3950.2155.0654.1263.9481.1270.7579.0254.9851.08
36.8641.4550.00
59.4755.4763.7844.7044.9055.0181.6584.0070.1551.2554.87
Wp
(%)
22.1528.3929.4141.4826.8338.6629.0821.6926.3724.7632.3927.1428.8426.6231.6734.1628.1325.1131.49
26.5426.3231.1024.4125.2126.2127.8026.1431.1525.6326.7030.8332.0446.1549.4951.6151.5238.0635.16
25.1727.5733.16
34.1831.8737.3525.9024.9530.7545.0943.7045.1254.4331.71
Mp
18.2324.4429.1129.5620.8327.7525.8712.8121.6322.3124.4916.7524.1519.4011.5925.7919.8312.6015.28
27.8421.7325.3118.5117.7020.3217.0818.9125.3714.7023.5124.2322.0822.7931.6319.1427.5015.9215.92
11.6913.8816.84
2624
261920245940311723
Wh
(%)
5.695.267.002.213.734.216.646.924.031.482.51
Δ(g/cm3)
1.581.641.631.581.71
1.811.711.881.701.701.791.571.832.081.761.932.091.92
1.841.871.951.931.942.01
2.022.002.001.971.982.011.841.791.771.661.851.861.892.412.071.91
1.611.591.491.911.701.601.621.601.611.811.79
δ(g/cm3)
2.772.592.832.562.752.672.692.582.672.602.54
δ
(g/cm2)
1.071.080.981.491.221.121.050.991.031.281.28
η%y• δ
6158654256586162615150
rß>δ We
535051
4248485761595351
KwWe/Wn
0.870.870.781.000.860.830.930.980.961.001.00
e
1.591.401.890.921.251.381.561.611.591.030.98
B
1.751.020.570.530.560.190.440.710.190.410.280.870.720.07
-0.40-0.30
0.510.450.85
0.130.190.660.450.160.240.040.12
-0.13-0.10-0.010.090.02
-0.320.03
-0.16-0.72-0.31-0.38
-0.110.68
-0.57
0.530.620.550.120.730.520.280.440.380.430.35
Kd
-0.74-0.020.430.470.440.810.560.290.810.590.910.130.280.931.401.300.490.550.15
0.870.810.340.560.840.760.960.881.121.101.010.910.981.320.971.161.721.311.38
1.110.321.57
0.400.370.470.870.270.490.710.570.620.560.65
Vp1
(m/sec)
570366342980420370550560930
VpII
(m/sec)
480358358
1030355300730805
1050
Kan
0.840.981.051.050.850.821.331.441.13
Cop
0.80
0.54
0.87
0.63
0.900.87
0.77
0.78
0.90
0.680.380.250.570.470.340.560.660.67
-0.50
In that the large volume shrinkage of the Core 22 sample islinked with its peculiar composition, one can say in generalthat below the depth of 250 meters, the volume shrinkage issmall (Table 14).
Rather curious data have been obtained from flocculationexperiments on the samples. Two cubic centimeter wetspecimens were taken from each sample. The cubes were puton a metal net with 1-cm meshes, the net placed on a supportin a vessel and saturated with distilled water. For 17 days,observations were made.
The results of these tests are given in Table 15. The data forSite 381 and Hole 380A are grouped so that they characterizea common section of deposits from the depth of approxi-mately 60 meters sub-bottom down to almost 1000 meters.
The test showed that down to about 300 meters sub-bottom, the sample in distilled water becomes completelydistorted.
Above this level, except at about 100 meters, the entireunderlying series of deposits are destroyed in distilled water,whereas below it the beds are distorted but not destroyed.Still lower, in the 300-800 meter interval, the water sampleinteraction produces distortion but not destruction. Samplesof rocks from under 800 meters were virtually unaffected bywater.
The samples' natural textures were also investigated. Bytexture we refer to the spatial arrangement (orientation) ofstructural elements, independent of their size, i.e., unit parti-cles , aggregates, microblocks, etc., of which the sediment orthe rock is composed. Both meso- and microtexture werestudied.
The mesotexture, or the orientation of the structural ele-ments larger than 1 to 5 µ was examined under the opticalmicroscope. Polished sections were prepared from orientedsamples dried at room temperature. Only monolith samples
1117
P. N. KUPRIN ET AL.
TABLE 10Classification of Clay
Deposits by ConsistencyIndex
SolidSemi-solidTight-plasticSoft-plasticFluid-plasticFluid
B <O0 < B < 0.25
0.25 < B < 0 . 50.5 <B < 0.750.75 < B < 1
B > 1
TABLE 11Sound Velocity Changes of Two Samples From Site 381 Under
Different Compactions and Load
Sound VelocityAfter StrainingWater Through
Sample andCompacting it
Under 1.5 kg/cm2,(m/sec)
1320
Sample
381-9-top381-19-top
Sound Velocityin Sample Before
Compaction(m/sec)
366370
Sound VelocityAfter Compaction
With a Load of1.5 kg/cm2, Without
Straining WaterThrough Sample
(m/sec)
620_
TABLE 12Filtration Coefficient of the Same Samples as in Table 11,
Under Varying Pressure Gradients
Coefficient of Filtration(cm/sec)
SamplePressure gradient
30Pressure gradient
0
InitialPressureGradient
381-14-top381-19-top
0.340.40
1010
,-7,-7
0.22 100.30 10
10.5-0.7
from Site 381 were studied. Carbonate-enriched deposits(Cores 13, 14, and 33) had no orientation. All the remainingSite 381 samples had an oriented mesotexture, expressed insimultaneous extinction of the clay mass in crossed nicols.However, the orientations differed. In the samples fromCores 7, 9, 10, and 19, the orientation diverged from thebedding plane more than at 40°-45°. In one of these samples,nearly vertical fissure channels, 0.016-0.03 mm across, wereobserved. Pyrite globule accumulations were present insidethem. At great depths (Cores 22, 26, and 31), clay matterparticles are oriented in a plane near to that of bedding.
TABLE 13Mechanical Properties of the Sediments From Hole 380A and Site 381
Core
Hole 381
7
9
10
13
14
19
22
26
31
33cep.33memm.
Hole 380/
5
14
20
26
40
Depth BelowSea Floor
(m)
57.066.576.085.585.595.0
114.0123.5123.5133.0171.0180.5195.0199.5228.0237.5275.0285.0294.0
304.0
380.0
460.0
518.0
575.0
700.0
Direction ofthe Measurement
1
II1
II1
1!1
1!1
II1
r
1
II1
II1
II1
II1
II
1
ili
tl1
II1
IIi
II
σKg/cm2
0.651.030.220.280.370.211.431.210.300.181.060.461.681.560.950.865.473.421.90
1.97
6.7510.6
EKg/cm2
48371818434224291610323286
1046479
1591 1847
84
330170
maxKg/cm2
0.440.460.170.250.120.300.980.440.180.230.480.291.200.761.050.432.041.801.211.36
3.650.652.163.805.055.054.103.325.104.12
^minKg/cm2
0.240.130.090.100.090.250.460.390.130.100.36
0.530.420.810.290.900.720.800.65
1.310.501.520.663.322.922.781.341.001.08
Kr
0.96
0.68
0.40
2.23
0.78
1.66
1.58
2.44
1.13
1.23
5.62
0.57
1.00
1.23
1.24
PmKg/cm2
1.240.980.720.850.900.922.751.600.500.600.981.263.123.321.751.506.503.60
KPm
1.27
0.85
0.98
1.72
0.83
0.78
0.94
1.17
1.81
X(quantity
of contactsin cm2)
0.15 109
0.63 108
0.73 109
0.21 108
0.21 108
0.36 108
0.21 109
0.16 109
0.3 108
0.92 107
0.38 108
P lpower
of the in-dividualcontact(dyne)
6.5 10~4
4.7 10"4
5.4 10"5
7.0 10"3
1.4 ; 10" 3
2.7 10~3
1.1 10~3
0.79 10"3
2.1 10~2
2.6 10~2
2.5 10~2
2.4 10" 2
1118
TABLE 14Volume Shrinkage of
Site 381 Samples
Sample
381-7, CC381-9, top381-10, CC381-13, CC381-14, top381-19, top381-22, CC381-31, CC
Volume Shrinkage
29.932.233.56.2
25.118.131.8
4.5
The microtexture was investigated by the X-ray techniquesand scanning electron microscope. The specimens for thescanning electron microscope were specially prepared topreserve their natural state, according to the procedure de-scribed by Osipov (1974). Vacuum sublimation drying wasused to preserve the deposit's natural texture. A 16-mm-wide, 5-mm-high specimen of undamaged structure andnatural humidity was cut from the monolith. For quick freez-ing, the specimen was immersed for 15-30 seconds in isopen-tane, cooled in liquid nitrogen to 150°-160°C. After instantfreezing, the specimen was transferred to a refrigerator with avacuum chamber and dried out. The sublimation drying at-40°-45°C and 10 atm vacuum continued for 24 to 36 hours.A cut perpendicular to the bedding plane was investigated.Displaced fragments and particles were removed from thesplit surface with adhesive tape applied to it several times.The results are presented on photographs (Figure 4). Thephotographs, as well as the samples themselves, are orientedperpendicularly to the bedding plane. Regrettably, no quan-tification of the structure and the texture has been carried outon the photographs. We believe, however, that they providevisual qualitative information on the sizes and interaction ofthe structural elements—particles, aggregates, andmicroblocks—on the sizes and distribution in the sample ofthe pores and microfissures, etc. Although only a few sam-ples were investigated, the photographs indicate an altera-tion, with depth, of the texture and structure of thePliocene-Quaternary Black Sea clays. From the 200-300meter interval on (Site 381, Cores 22 and, especially, 31), theclay particles lie closer together, with the loose large-porousstructure becoming increasingly monolithic and compact.The sample taken from the depth of 700 meters (Core 40,Hole 380A) is noteworthy. It is rich in diatom skeletons andamorphous, icicle-shaped or tallow-like cement. The cementfills the interstitial pore space and the microfissures, reinforc-ing the sample. Its source may have been amorphous silicafrom dissolved diatom skeletons. The sample's photographsalso show a lot of spherical cristobalite particles (Figure 5).
From X-ray study, a quantitative estimate of the samples'microtexture has been obtained. The clay particles' orienta-tion was studied on n X-ray diffractometer with CuαK-αradiation, Uα= 35 kv, la = 10 ma. Two samples, preparedas described above, were investigated for a quantitativeevaluation of the orientation degree. One sample served tocharacterize the bedding plane, and the other, the perpen-dicular section. The surfaces were flattened and polishedthoroughly. On the diffraction pattern, the first-order 001basal reflections of clay minerals and reflections 010 werefixed. From the ratio of the integral intensities (I) of these
PHYSICAL AND MECHANICAL PROPERTIES
TABLE 15Flocculation of Samples From Hole 380A and Site 381
in Distillate Water
SampleInterval
(m) Time and Character of the Flocculating
381-7, CC
381-9-top
381-13, CC
381-14-top
381-19-top
381-22, CC
381-26, CC
381-31, CC
38OA-5, CC
380A-12, CC
380A-14, CC
380A-18, CC
380A-20, CC
380A-26, CC
380A-36, CC
380A-40, CC
380A-52,CC
380A-56, CC
380A-71, CC
66.5
76.5
123.5
124.0
171.0
199.5
237.5
285.0
380.0
446.5
465.5
503.5
522.5
579.5
665.0
703.0
817.0
855.0
997.5
Sample was destroyed absolutely andpenetrated through the net in 1 hour30 minutes
Sample was destroyed absolutely andpenetrated through the net in 2 hours30 minutes
Sample was destroyed after 16 hoursbut it did not penetrate through thenet after 17 days
Sample was destroyed and penetratedthrough the net after 1 hour 40 minutes
Sample was destroyed and penetratedthrough the net after 2 hours
Sample was deformed during 1 hour40 minutes but did not completelypenetrate the net after 17 days
Sample was destroyed after 2 hoursand penetrated through the net after12 hours
Sample was cracked after 17 days, butwas not destroyed and penetratedthrough the net
Sample penetrated incompletely throughthe net during 12 hours
Sample was destroyed after 16 hours,but it did not completely penetrate thenet after 17 days
Sample was cracked after 16 hours, butit was not deformed and penetratedthrough the net after 17 days
Sample was destroyed after 16 hours,but it did not penetrate through the netafter 17 days
Sample was cracked after 16 hours, butit was not deformed and penetratedthrough the net after 17 days
Sample was cracked and slightly deformedand did not penetrate through the netafter 17 days
Surface of the sample was crackedslightly, but it was not deformed after17 days
Sample cracked along the plane of thesedimentation after 16 hours, but it wasnot deformed after 17 days
Surface of the sample was somewhatsoaked, but essentially did not changeafter 17 days
Sample was essentially unchanged after17 days
Sample was essentially unchanged after17 days
reflections, the orientation coefficient was determined foreach sample as Kor = Iooi/Ioio. From the data for the twosamples, the orientation degree of each monolith investigatedwas determined as
K
1119
P. N. KUPRIN ET AL.
Figure 4. Photos of samples from Site 381 and Hole 380 with the original (natural) texture after the vacuum dry sublimation.(A) Core 7, CC, Site 381 × 8000. (B) Core 19 top, Site 381 X 5000. (C) Core 22, CC, Site 381 X 5000. (D) Core 22, CC,Site 381 × 5000. (E) Core 5, CC, Site 381 X 5000. (F) Core 5, CC, Hole 380A X 10,000. (G) Core 56, CC, Hole 380A X200. (H) Core 56, CC, Hole 380A X 10,000. (I) Core 71, CC, Hole 380A X 150. (J) Core 71, CC, Hole 380A X 1500.
where Kor is the orientation coefficient of the sample cut outparallel to the bedding, and Korl is the orientation coefficientof the sample cut out perpendicular to the bedding.
For a maximum orientation of the particles in the planeparallel to the bedding, Cor = 1, and in that perpendicular to
it, Cor 0. When orientation is random, Cor = 0.5. In thetopspart of Site 381, down to the depth of 200 meters, theorientation degree is mostly less than 0.5, i.e., the clayparticles are predominantly oriented in a plane perpendicularto the bedding. Beneath that depth, Cor everywhere is more
1120
PHYSICAL AND MECHANICAL PROPERTIES
Figure 5. Cristobalite and Siθ2 amorphous in the samples from Core 40, CC and Core 20, CC, Hole 380A. (A)Core 40, CC X 1000. (B) Core 20, CC X 2000. (C) Core 40, CC × 5000. (D) Core 40, CC X 15,000. (E) Core20, CC × 7000.
1121
P. N. KUPRIN ET AL
than 0.5 but not more than 0.67. The further variation of theorientation degree could be tracked for greater depths onsamples from Hole 380A which retained their natural struc-ture. The results are given in Table 9. They indicate theorientation at about 400 meters (Site 381, Core 5) to be high,sometimes reaching 0.80. With increasing depth, the clayparticles have a tendency for a greater orientation degree inthe bedding plane. Against this background of continuousgrowth, horizons of a lowered orientation occur. The devia-tions are associated with the lithology of the deposits con-cerned. In coarser material, clay particles are less oriented.Judging by the lithological description of the sites, the pre-sence of carbonate matter has the same effect. No drop in Coris observed in diatom-containing or amorphous silica-cemented samples.
Scanning electron microscope studies confirm and vis-ualize the growing orientation in the bedding plane of the clayparticles with increasing depth, below 199-meter interval(Core 22, Site 381).
DISCUSSION
Having examined all the data obtained on the physical andmechanical properties of the deposits under study, we con-structed a composite section for Holes 38O/38OA and 381.The top part (approximately down to 300 m sub-bottom) ofthis section is based on specially preserved Site 381 samples,and the lower parts, on Hole 380A. The samples of thesection's bottom part proved lithified enough to have retainedtheir natural state.
From the data on the physical and mechanical properties ofthe deposits features were chosen that visibly varied down thesection and clearly illustrated a tendency. These featuresproved to be the mechanical properties of the deposits,namely the strength indicators, and the rock's soaking de-gree. Figure 6 presents these parameters.
Figure 6 clearly shows breaks in the physical and mechani-cal properties which are zones or intervals of various stagesof compaction or lithification. The zones or intervals arebased on all of the data on the physical and mechanicalproperties shown in the tables and appendices.
At the top of the section, the zone of most recent deposits,has properties typical of unlithified sediments. It extendsdown to at least 200 meters sub-bottom. Its main feature isthat all the overlying sediments have a shear strength (r) notmore than 1 kg/cm2. Except for several horizons, the same istrue of other strength indicators. The sediments in the upper200-meter zone also have a high soaking degree. For the mostpart they are destroyed by water; at least all are stronglydistorted. Typically, their humidity always exceeds the upperplasticity limit. Together with a high porosity, this fact corre-lates with a low orientation degree in the bedding planeobserved for the sediment's clay particles. Owing to a highporosity, humidity, and gas content, the upper 200-meterdeposits have the lowest sound velocities.
Because we lacked samples from the uppermost horizons,no reliable subdivision of the series into intervals of differentlithification degrees was possible. Yet, at least two sub-zonesappear to be discernible in the upper 200 meters by physicaland mechanical properties, the boundary between them beingnear the depth of 90 meters. This boundary is indicated by thesoaking degree in Figure 6. Indeed, while all sediment sam-
ples occurring above 90 meters were fully destroyed bydistilled water, several horizons occur below that depthwhere they are just heavily distorted. A boundary at 90meters seems to be indicated also by the variation of certainother physical and mechanical indicators, given in tables andappendices.
Beneath 200 meters, an approximately 100-meter-thicktransient zone is singled out, apparently comprising a seriesof deposits where several horizons have rock properties whilethe others remain essentially unlithified sediments. The zoneis clearly indicated in the diagrams of the vertical variation ofthe characteristics of the deposits' strength, where the zonecorresponds to the part of the diagrams occupied by valuesfluctuating around 1 kg/cm2.
In the transient zone, other indicators sometimes approachvalues characteristic of rocks. For example, humidity comesclose to the lower plasticity limit, making the deposits highlyelastic.
Sharp increase of compression strength, shear strength,etc., occurs at the depth of 300 meters below the sea floor.Even though the compressive and shear strengths in indi-vidual horizons vary strongly, the values never fall below 2kg/cm2. Other rock properties also undergo a dramaticchange. This is conspicuous in the rock texture, where theorientation of clay particles parallel to the bedding is mar-kedly increased. Porosity and humidity are reduced accord-ingly, which, in turn, raises the velocity of sound wavespropagating in the deposit having these properties. The baseof the 300-meter-thick series likewise clearly shows, by thesoaking degree, that the underlying deposits soaked onlyslightly; the reaction to distilled water quickly dwindlesfurther down the section. For these reasons, the depositsoccurring underneath 300 meters can be considered to be truerock. From this level downward, the variation of all physicalproperties changes slowly, although that of mechanical prop-erties (strength) continues.
Thus, in the section of the Black Sea deposits under inves-tigation, a zone is distinctly identifiable, in which the de-posits are largely unconsolidated, and have not been sedi-ment lithified. The zone embraces a thick interval from 200to 300 meters beneath the sea floor. It is here that the majorchange takes place in the sediment. Apparently, the underly-ing cause is a basic alteration of the spatial arrangement ofparticles (from random to ordered) and a major strengtheningof the structural bonds (strength of individual contact) be-tween them. In the upper 200-meter series, the random dis-tribution of particles leads to a high porosity and humidity.The solid phase-pore water system is largely balanced hydro-statically, weakening the influences of the overlying watercolumn pressure and of the sediment series. With time andcontinuing deposition of sediment, the particles slowly be-come oriented and gradually come closer together. Eventu-ally, the pressure of the overlying water and sediment beginsto act mostly on the framework of the mass, or its solidparticles. As a result, they become oriented parallel to bed-ding planes, thereby further sharply reducing porosity andhumidity. Meanwhile, as the particles come closer to oneanother, their structural bonds grow stronger (individual con-tact strength). In all likelihood, these are the processes takingplace in the transient zone.
The heightened strength of the rocks beneath 300 meterslargely stems from diagenetic processes. First of all, the level
1122
PHYSICAL AND MECHANICAL PROPERTIES
Depthbelow
sea floor
σ(kg/cm2)
0 1 2 3 4 5 6
T max(kg/cm2)
1 2 3 4 5
TJT.Pm
(kg/cm2)0 1 2 3 4 5 6
Reaction withThe distill, water
0
100-
200-
300-
400-
500-
600-
700-
800
900
1000-
full destruction
partly deformationpartly destruction *- <-
IS. o
there is no destruc-tion, only cracksand deformation,decrease of tough
light deformationchange of tough
there are nochangespractically
Figure 6. Changes in the mechanical (deformative) properties of the deposits from Site 381 and Hole 380A and their reactionwith the distillate water downsection.
coincides with a marked increase in carbonate content, a partof the carbonate being obviously recrystallized and function-ing as cement. Without this, the lower boundary of thetransient zone might well have been somewhat lower than300 meters. Another cementing element is amorphous silica,or cristobalite, formed from diatom skeletons dissolved in analkaline medium. This cementing gains in importance below650-700 meters, giving rise to the irreversible aggregation ofcolloid and subcolloid particles, the high compressive andshear strength (up to 6 kg/cm2), and virtually complete loss ofcapacity for soaking. The latter property warrants referring tothe clay rocks at the section's bottom as argillites. Below 700meters the Black Sea deposits can be considered as a regionwhere intensive catogenetic alteration of rocks begins.
The investigation illustrates a continuous section of themarine sediments' alteration through a transition zone intorocks, in which early and middle stages of catagenesis arerecorded.
REFERENCES
Amelina, E. A. andShchukin, E. D., 1970. Study of regularities offormation of contacts in porous dispersed structures: Kolloid.zhurn., v. 32, no. 6.
Inderbitzen, A. L., 1974. Deep-sea sediments. Physical andmechanical properties: New York (Plenum Press) p. 477-488.
Osipov, V. I., 1974. Preparation of clay specimens for microtex-ture investigations: Vestnik Moskovskogo universiteta, ser.Geologiya, no. 6.
Shchukin, E. D., Amelina, E. A., Yusupov, R. K., andRebinder,P. A., 1970. Evaluation of the strength of individual contactsbetween microcrystals in porous dispersed bodies: DAN SSSR,v. 191, p. 1037.
Weaver, Ch., 1967. Role of clay minerals in sediments. In: Osnov-nye aspekty geokhimii nefti: Moscow (Mir Publishers).
1123
