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Lange, Heinz (1975): Sedimentology of surface sediments from the continental shelf and slope off West Africa (Table 1) [dataset]. PANGAEA, https://doi.org/10.1594/PANGAEA.526931, Supplement to: Lange, H (1975): Herkunft und Verteilung von Oberflächensedimenten des westafrikanischen Schelfs und Kontinentalhanges. Meteor Forschungsergebnisse, Deutsche Forschungsgemeinschaft, Reihe C Geologie und Geophysik, Gebrüder Bornträger, Berlin, Stuttgart, C22, 61-84

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Abstract:
Samples from sutface sediments of the shell, continental slope, and adjacent deep sea regions off West Africa between 27° N and 15° N were investigated with respect to grain size distribution of the total samples, sand contents of the acid insoluble residues, carbonate content of the total samples, and the separate grain size fractions, specific surfaces, colours and mineralogical composition of the clay fractions.
The grain size distributions of the total samples of the sediments of the shelf and the continental slope off Spanish-Sahara are controlled mainly by biogenic components. The supply of terrigeneous material in this area is very low. At deeper parts of the continental slope and in the deep sea areas, the relative amounts of carbonate minerals in the sediments are considerably reduced. The prevailing sand contents of the upper slope changes into clay dominance.
On the shelf of Mauritania – represented by profiles extending down to 200 m water depth – the grain size is also controlled mainly by biogenic carbonates. Nevertheless, the admixture of fossil silicate components is important, too.
The southern parts of the area is investigated are located in a region influenced by sediments of the Senegal River, which especially control the contents of silt and clay. The silicate sands, predominately of quartz, are fossil and form a mixed sediment with younger deposits.
The carbonate contents of the different grain size fractions are formed either by sedimentation of carbonate and silicate particles of the respective grain size or by autochtonous disintegration of coarser sediment particles, as shown by the occurence of Mg-rich calcite and especially aragonite in the clay sized fraction.
In the northern parts of the area investigated, which have very minute terrigeneous supply, the latter mechanism is the dominant factor, controlling the carbonate contents of the fine grain sized fractions. In the vicinity of the mouth of the Senegal the carbonate contents are influenced by extremely high dilution with terrigencous silicates.
Mg-rich calcite and aragonite are produced preferentially in shallow slope and shelf areas up to 500 m of water depth.
The specific surfaces of the carbonate-free clay fractions indicate that the clay fractions of the shelfareas with little terrigenous supply consits of relatively coarser particles. Very fine particles are removed and transported towards the deep sea. Lateral differentiation of this kind was not observed in the area off Senegal. The high surface areas, characterizing the clay fractions of this region, are thought to be due to high montmorillonite contents as was found for deep seas sediments. The mineralogical composition of the clay fraction from the southern parts of the area is characterized by high kaolinite and montmorillonite contents, while in the northern illite is predominating. At least two types of montmorillionites are present: in areas influenced by the Senegal mostly one type was found, which could swell to 17; on the shelves and slopes of the other regions the montmorillonite-group is represented by a montmorillonite-mica-type mixed-layer mineral. A “glauconite”, found in the sand fraction, which had very similar properties to those of the montmorillonite-mica mixed-layer, is believed to be the source of this mixed-layer-type mineral.
Palygorskite is present in all samples out of range of the Senegal supply. It may be an indicator of eolian transported material. The occurence of rich palygorskit deposits in the arid hinterlands emphasizes the terrestrial origin.
Coverage:
Median Latitude: 20.158225 * Median Longitude: -17.054545 * South-bound Latitude: 15.265000 * West-bound Longitude: -22.625000 * North-bound Latitude: 27.078333 * East-bound Longitude: -14.666667
Date/Time Start: 1971-01-01T00:00:00 * Date/Time End: 1971-12-02T00:00:00
Minimum DEPTH, sediment/rock: m * Maximum DEPTH, sediment/rock: m
Event(s):
GIK12301-4  * Latitude: 27.078333 * Longitude: -15.066667 * Date/Time: 1971-10-30T00:00:00 * Elevation: -2906.0 m * Location: East Atlantic * Campaign: M25 * Basis: Meteor (1964) * Method/Device: van Veen Grab (VGRAB)
GIK12302-3  * Latitude: 26.003333 * Longitude: -14.666667 * Date/Time: 1971-10-30T00:00:00 * Elevation: -64.0 m * Location: East Atlantic * Campaign: M25 * Basis: Meteor (1964) * Method/Device: van Veen Grab (VGRAB)
GIK12303-2  * Latitude: 26.196667 * Longitude: -14.793333 * Date/Time: 1971-10-30T00:00:00 * Elevation: -151.0 m * Location: East Atlantic * Campaign: M25 * Basis: Meteor (1964) * Method/Device: van Veen Grab (VGRAB)
Parameter(s):
#NameShort NameUnitPrincipal InvestigatorMethod/DeviceComment
Event labelEvent
Latitude of eventLatitude
Longitude of eventLongitude
Elevation of eventElevationm
DEPTH, sediment/rockDepth sedmGeocode
Size fraction < 0.002 mm, clay<2 µm%Lange, Heinz
Size fraction < 0.002 mm, clay<2 µm%Lange, HeinzCarbonate content of the separate grain size fractions %
Size fraction 0.0063-0.002 mm, fine silt6.3-2 µm fU%Lange, Heinz
Size fraction 0.0063-0.002 mm, fine silt6.3-2 µm fU%Lange, HeinzCarbonate content of the separate grain size fractions %
10 Size fraction 0.020-0.0063 mm, medium silt20-6.3 µm mU%Lange, Heinz
11 Size fraction 0.020-0.0063 mm, medium silt20-6.3 µm mU%Lange, HeinzCarbonate content of the separate grain size fractions %
12 Size fraction 0.063-0.020 mm, coarse silt63-20 µm gU%Lange, Heinz
13 Size fraction 0.063-0.020 mm, coarse silt63-20 µm gU%Lange, HeinzCarbonate content of the separate grain size fractions %
14 Size fraction > 0.063 mm, sand>63 µm%Lange, Heinz
15 Size fraction > 0.063 mm, sand>63 µm%Lange, HeinzOf the silicatic residual
16 Size fraction > 0.063 mm, sand>63 µm%Lange, HeinzCarbonate content of the separate grain size fractions %
17 CarbonatesCarb%Lange, Heinz
18 Inner AreaInAream2/gLange, Heinz
19 Smectite (Intensity, 17Å)Sme I. 17ÅcpsLange, HeinzClay mineral not identified
20 Kaolinite+Chlorite (Intensity, 7Å)Kln+Chl I 7ÅcpsLange, HeinzClay mineral not identified
21 Illite (Intensity, 10Å)Ill I 10ÅcpsLange, HeinzClay mineral not identified
Size:
1121 data points

Data

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Event

Latitude

Longitude

Elevation [m]

Depth sed [m]

<2 µm [%]

<2 µm [%]
(Carbonate content of the sepa...)

6.3-2 µm fU [%]

6.3-2 µm fU [%]
(Carbonate content of the sepa...)
10 
20-6.3 µm mU [%]
11 
20-6.3 µm mU [%]
(Carbonate content of the sepa...)
12 
63-20 µm gU [%]
13 
63-20 µm gU [%]
(Carbonate content of the sepa...)
14 
>63 µm [%]
15 
>63 µm [%]
(Of the silicatic residual)
16 
>63 µm [%]
(Carbonate content of the sepa...)
17 
Carb [%]
18 
InArea [m2/g]
19 
Sme I. 17Å [cps]
(Clay mineral not identified)
20 
Kln+Chl I 7Å [cps]
(Clay mineral not identified)
21 
Ill I 10Å [cps]
(Clay mineral not identified)
GIK12301-4 27.0783-15.0667-2906045.1543.2316.2146.0311.3432.8015.0933.1012.190.9080.9148.371.4313336
GIK12302-3 26.0033-14.6667-6400.2828.460.1035.170.0844.830.2268.6099.3250.5082.8082.136.6183547
GIK12303-2 26.1967-14.7933-15101.8840.090.7845.210.4750.101.8643.3095.0180.8838.3243244
GIK12304-2 26.2300-14.8100-19700.7944.520.3850.970.2764.321.3646.8097.2070.2064.0368.832.5143947
GIK12305-2 26.2850-14.8550-50101.5944.800.7465.810.6071.533.8443.4093.2341.1074.5580.044.0164440
GIK12306-2 26.3267-14.9283-74106.6847.703.7756.863.2746.7012.2039.7074.0718.8070.2368.339.0342838
GIK12307-3 26.4050-14.9617-1070042.1042.2815.5572.7710.5466.3017.9959.0013.8067.38134.0502426
GIK12308-2 26.6450-15.0533-2090033.5145.3013.0054.1011.4941.4018.0040.7023.612.4080.2855.363.0402832
GIK12309-1 26.8383-15.1100-2849039.4144.9514.9048.9811.5731.2021.5538.6012.570.3081.9547.479.0442624
GIK12310-1 23.4983-18.7167-3075035.5450.5314.6258.6010.3941.2016.5948.3022.850.9075.9756.878.0
GIK12311-1 22.3667-16.7883-4301.2840.320.5150.690.4059.032.1952.0095.6297.1017.2127.324.0263144
GIK12312-2 22.4333-17.0700-6200.7053.990.2664.740.1566.961.8497.0541.2094.3993.126.0104644
GIK12313-2 22.4750-17.1500-8200.8648.830.3454.890.2563.321.8748.3096.6745.8094.9592.516.0153847
GIK12314-1 22.5017-17.2233-10901.5948.570.6452.590.4559.803.1994.1251.9090.9191.621.085042
GIK12315-1 22.7083-17.1583-10900.7450.520.2954.370.2461.501.6150.6097.1261.4092.8591.719.095635
GIK12316-1 22.9250-17.1333-10900.5554.080.2757.250.2264.101.4152.1097.5450.4091.4792.122.085735
GIK12317-1 22.8617-17.1500-21400.1155.650.0557.100.0465.660.1499.6651.5098.6898.676231
GIK12318-1 22.4150-17.0000-5801.3249.450.3056.590.2458.202.7547.9095.3884.8084.0191.330.0124543
GIK12319-1 22.3667-16.7867-3800.6140.690.2755.040.2258.201.0766.0097.8496.6045.2150.337.0124246
GIK12320-1 22.5150-16.6317-3800.4242.620.1953.040.1663.000.6760.7098.5795.0061.1461.236.0104050
GIK12321-1 22.8383-16.8667-15900.3949.490.1755.160.0963.000.8475.2098.5140.0069.9096.225.0
GIK12322-2 22.9033-17.1633-31600.1849.750.1556.220.1471.100.5674.0098.9726.0098.5297.9
GIK12323-1 22.9067-17.1850-41800.8950.200.3958.870.3666.201.5942.7096.7634.2089.7289.119.0185131
GIK12324-1 22.9150-17.2217-51401.6450.000.6053.250.5255.102.4832.3094.7564.0081.4981.827.0284527
GIK12325-2 22.9900-17.3283-768020.1048.717.4054.415.9645.6029.4529.5037.0821.3042.5254.231.0353629
GIK12326-3 23.0350-17.4100-1024027.8641.508.9952.6711.0543.1025.2628.4026.4611.6049.9340.849.0403228
GIK12327-2 23.1317-17.7350-2032040.0840.3920.2153.4313.2841.1015.8731.9010.572.9076.6344.540.0462925
GIK12328-1 21.1450-18.5733-2816046.9431.2715.7649.4113.1743.1015.8424.108.290.5079.4138.994.0
GIK12329-2 19.3717-19.9300-3314026.3347.1011.6741.969.7640.4016.3340.4035.912.1084.5762.294.0533413
GIK12330-1 16.7683-22.0167-3488027.7353.5711.4357.9310.1731.4015.6755.8035.001.7090.7265.387.066259
GIK12331-3 16.5483-21.9700-3568025.7752.4011.8159.799.8133.1015.5355.2037.082.7090.0264.184.0602911
GIK12332-2 16.1933-22.3450-1948021.6564.758.7563.9910.6753.8021.6374.0037.3083.70
GIK12334-2 16.1017-22.5867-72900.6064.910.4469.980.4577.401.2388.0097.2885.72
GIK12335-1 16.0867-22.6250-472013.1976.413.9877.296.7076.9017.4489.7058.6994.72
GIK12338-1 15.3167-17.0917-103011.9113.202.2427.141.7936.806.9629.2077.5053.0063.4564.577.058375
GIK12339-2 15.3433-17.1250-15106.5913.471.4724.430.9736.2011.4214.9079.5580.0051.2150.853.055378
GIK12340-3 15.3500-17.1867-20107.2315.321.8534.281.2951.5416.7815.4072.8529.8661.045469
GIK12341-2 15.3833-17.1967-32409.3515.682.6039.961.9647.7626.5112.0059.5857.0016.3015.863.050437
GIK12342-1 15.3833-17.2500-40505.7915.601.9845.011.5354.856.4535.0084.2568.2032.8428.555.056377
GIK12343-1 15.4000-17.2750-506013.9015.303.8441.453.5452.2240.1813.3038.7336.6016.4216.045.050437
GIK12344-1 15.2650-17.1833-725027.9114.626.7632.816.7735.6943.5716.6014.9852.9032.9419.954.057394
GIK12345-3 15.4800-17.3600-966038.7713.178.7129.269.8131.8034.0619.408.652.7021.6458.068257
GIK12346-1 15.5700-17.5450-1517048.9110.619.8821.4012.5719.8625.5521.103.0922.8261345
GIK12350-1 15.7083-16.7833-51031.569.785.3823.1114.1828.4148.3727.100.510.3034.0322.794.059392
GIK12351-1 16.0000-16.7250-68039.719.859.6220.0217.3125.7029.9627.703.400.6032.0326.485.064324
GIK12352-1 16.2783-16.6833-70037.7210.486.3324.4313.2429.1740.7139.102.000.9032.3823.385.062335
GIK12353-1 16.3883-16.6750-5506.7312.091.6526.802.1134.8219.5339.6069.9873.505.4412.273.055587
GIK12354-1 16.5800-16.6350-3901.8815.600.6014.300.3429.003.0034.6094.1896.506.889.160.053416
GIK12355-1 18.3350-16.2467-2500.2431.660.0838.900.0546.200.6158.5099.0299.104.0729.436.055387
GIK12356-1 18.3167-16.3200-4901.4921.980.7522.600.7335.6012.2327.1084.8079.4016.2518.8245125
GIK12357-1 18.3117-16.3550-6502.9925.851.3333.001.1437.6013.6722.8080.8772.6023.7728.325.0115633
GIK12358-1 18.3000-16.3833-7403.4425.391.401.0935.9412.0224.9082.0575.6035.4834.517.0344818
GIK12360-1 18.2833-16.4833-10603.0943.641.231.1430.008.6822.7085.8678.8025.7929.431.0275617
GIK12361-1 18.2800-16.5200-15608.2919.642.6028.932.2411.3017.2419.7069.6364.8034.2431.037.054379
GIK12362-1 18.2583-16.5867-218010.7217.553.1026.892.8637.7025.1617.5058.1660.5014.9921.141.0503911
GIK12363-1 18.5083-16.5967-20304.1920.391.5028.630.8913.7011.7512.2381.6781.008.7915.260319
GIK12364-1 18.5150-16.5433-14908.6122.212.8430.212.4832.5021.4822.1064.6064.2029.8829.840.0
GIK12365-1 18.5250-17.5150-10802.4024.030.7735.050.6437.801.3420.2094.8589.7024.9727.527.0
GIK12366-1 18.5333-16.4933-8901.6124.320.5232.830.4742.463.0725.7094.3391.608.2112.532.0
GIK12367-1 18.5217-16.4550-7003.3528.052.0942.652.0443.6012.9127.0076.6194.4014.3915.733.0
GIK12368-1 18.5517-16.4083-5601.5830.930.7448.970.6447.004.9326.4492.1189.3021.3831.932.0
GIK12369-3 18.5667-16.3550-4000.4028.050.1635.740.1141.170.5924.5498.7490.6038.0740.526.0343829
GIK12370-1 18.5833-16.2617-2000.3035.260.1242.750.0849.400.7548.5898.7594.8015.1964.140.0
GIK12371-2 18.7667-16.4200-4401.1432.350.5646.370.5248.012.7928.1194.9982.6033.1527.719.0
GIK12372-1 18.9283-16.4033-2801.5536.070.4651.830.5047.002.2140.7295.2895.806.9117.034.0373033
GIK12373-1 18.8933-16.4817-4801.8234.620.5750.600.6638.204.6827.1592.2791.505.807.647.0
GIK12374-2 18.8750-16.5183-6804.6430.531.5542.181.5742.9210.0740.7282.1783.5014.3620.238.0413821
GIK12375-2 18.8667-16.5367-10207.0228.512.4038.602.5238.499.9224.4578.0759.0031.2640.234.0
GIK12376-2 18.8283-16.6467-10003.4028.151.2742.551.0747.286.4624.8587.8073.6055.1558.037.0
GIK12377-1 18.8117-16.6600-15104.0127.201.7835.061.4451.7010.4225.4182.3567.9045.9453.035.0
GIK12378-1 18.7883-16.7117-20103.1725.931.3431.991.0634.069.2812.6585.1575.9021.0333.033.0
GIK12386-1 22.5617-16.9367-5901.4552.310.7057.890.5967.983.3793.8981.20104347
GIK12387-1 22.5650-16.9267-5800.1342.680.0551.000.0464.100.5799.2194.0038.6759.9
GIK12388-2 22.5083-16.8967-5701.1850.140.5257.870.3865.702.4954.8395.4482.8066.5265.4
GIK12389-1 22.5333-16.7033-4200.6340.590.3655.490.4879.001.2397.3064.61
GIK12390-1 22.6717-16.4600-3301.3338.230.7152.290.5960.706.7490.6382.8054.4953.0134740
GIK12391-1 22.7383-16.6500-4500.9645.250.4564.460.3368.903.1561.4495.1197.2014.5214.1