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Schrader, Hans-Jürgen (1972): Siliceous fossils in sediments of the Ibero-Moroccan shelf and adjacent deep sea plains. PANGAEA, https://doi.org/10.1594/PANGAEA.548410, Supplement to: Schrader, H-J (1972): Kieselsäure-Skelette in Sedimenten des ibero-marokkanischen Kontinentalrandes und angrenzender Tiefsee-Ebenen. Meteor Forschungsergebnisse, Deutsche Forschungsgemeinschaft, Reihe C Geologie und Geophysik, Gebrüder Bornträger, Berlin, Stuttgart, C8, 10-36

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Abstract:
Siliceous skeletons were investigated in two core profiles (9 cores), one off Cap de Sines, Portugal and the other off Cap de Mazagan, Morocco. Total number of skeletons was determined per gram of dried sediment at different core depths of the fraction
>21 µ. Results are compared with a core profile from the Arabian Sea.
Diatoms are of four groups: (A) marine-planktonic, B) marine-benthic, (C) freshwater and (D) Tertiary species (Trinacria e.g.). Species from groups (B), (C) and (D) are redeposited in all cores taken at a water depth of greater than 100 m.
Small numbers of Silicoflagellates and Radiolarians were found throughout the cores from the Ibero-Moroccan shelf. In the Arabian Sea core, Radiolarians were concentrated in distinct horizons in which Tertiary material was redeposited (40-50, 140-150,
250-260 cm).
The number of siliceous skeletons per gram of dried sediment decreases more or less rapidly with increasing depth in all cores. Whereas about 2500 skeletons were found in sediments close to the surface, approximately 100 skeletons only were found in deeper (>40 cm) layers. Deeper horizons with more than 100 specimens were interpreted as redeposited material. This sediment contained robust skeletons, resistant against dissolution, as well as benthic and Tertiary material.
The decrease of siliceous skeletons relative to core depth depends upon the sedimentation rate. Where the sedimentation rate is high, the opal dissolution zone extends down to 30-60 cm, where the sedimentation rate is low, it is located at 10-30 cm. Below these depths opals disappears. These zones also have approximately the same age (4000 years) everywhere. Siliceous skeletons dissolve differentially, first the Silicoflagellates disappear, second the Diatoms, third the Radiolarians, and fourth the Sponge Spicules.
Surface structure of skeletons from near the opal dissolution zones are similar to those of skeletons treated with NaOH.
Tertiary diatoms (Trinacria e. g.) and benthic diatoms (Campylodiscus e.g.) dissolve less rapidly than skeletons of modern planktonic diatoms (Coscinodiscus e.g.).
The time control of the opal dissolution zones appeared rather independent of various oceanic influences. No evidence was found for effects from upwelling either off Portugal or off Morocco. No difference in dissolution rates was recorded between the abyssal plains lying off these two areas. Likewise, there was no change in solution rates from Pleistocene to Holocene within either one of the abyssal plains. The Mediterranean outflow, which is enriched in dissolved silica, apparently had no effect on dissolution rates of siliceous skeletons in the sediment.
Coverage:
Median Latitude: 34.226840 * Median Longitude: -2.411017 * South-bound Latitude: 21.950000 * West-bound Longitude: -10.853000 * North-bound Latitude: 37.916000 * East-bound Longitude: 64.183300
Date/Time Start: 1967-01-17T14:00:00 * Date/Time End: 1967-02-07T10:54:00
Event(s):
M1048B * Latitude: 21.950000 * Longitude: 64.183300 * Elevation: -2835.0 m * Device: Gravity corer (Kiel type) (SL)
M8_004-2 (M8004B) * Latitude: 37.916000 * Longitude: -10.853000 * Date/Time Start: 1967-01-17T14:00:00 * Date/Time End: 1967-01-18T02:06:00 * Elevation: -4979.0 m * Recovery: 1.41 m * Location: North Atlantic Ocean * Campaign: M8 (Atlantische Kuppenfahrten 1967/1-3) * Basis: Meteor (1964) * Device: Kasten corer (KAL)
M8_008-3 (M8008C) * Latitude: 37.650000 * Longitude: -9.533000 * Date/Time Start: 1967-01-20T01:00:00 * Date/Time End: 1967-01-20T10:12:00 * Elevation: -1148.0 m * Recovery: 1.19 m * Location: North Atlantic Ocean * Campaign: M8 (Atlantische Kuppenfahrten 1967/1-3) * Basis: Meteor (1964) * Device: Kasten corer (KAL)
Size:
10 datasets

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Datasets listed in this publication series

  1. Schrader, H-J (1972): Absolute number of siliceous skeletons in sediment core M1048B, Arabian Sea (Table 11). https://doi.org/10.1594/PANGAEA.112568
  2. Schrader, H-J (1972): Absolute number of siliceous skeletons in sediment core M8_004-3, Ibero-Moroccan shelf (Table 2). https://doi.org/10.1594/PANGAEA.112569
  3. Schrader, H-J (1972): Absolute number of siliceous skeletons in sediment core M8_008-3, Ibero-Moroccan shelf (Table 5). https://doi.org/10.1594/PANGAEA.112570
  4. Schrader, H-J (1972): Absolute number of siliceous skeletons in sediment core M8_016-2, Ibero-Moroccan shelf (Table 7). https://doi.org/10.1594/PANGAEA.112571
  5. Schrader, H-J (1972): Absolute number of siliceous skeletons in sediment core M8_017-2, Ibero-Moroccan shelf (Table 8). https://doi.org/10.1594/PANGAEA.112572
  6. Schrader, H-J (1972): Absolute number of siliceous skeletons in sediment core M8_018-4, Ibero-Moroccan shelf (Table 9). https://doi.org/10.1594/PANGAEA.112573
  7. Schrader, H-J (1972): Absolute number of siliceous skeletons in sediment core M8_020-2, Ibero-Moroccan shelf (Table 10). https://doi.org/10.1594/PANGAEA.112574
  8. Schrader, H-J (1972): Absolute number of siliceous skeletons in sediment core M8_031-1, Ibero-Moroccan shelf (Table 6). https://doi.org/10.1594/PANGAEA.112575
  9. Schrader, H-J (1972): Absolute number of siliceous skeletons in sediment core M8_057-2B, Ibero-Moroccan shelf (Table 3). https://doi.org/10.1594/PANGAEA.112576
  10. Schrader, H-J (1972): Absolute number of siliceous skeletons in sediment core M8_058-2, Ibero-Moroccan shelf (Table 4). https://doi.org/10.1594/PANGAEA.112577