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Diester, Lieselotte (1972): Late pleistocene and holocene sedimentation in the central and eastern Persian Gulf. PANGAEA,, Supplement to: Diester, L (1972): Zur spätpleistozänen und holozänen Sedimentation im zentralen und östlichen Persischen Golf. Meteor Forschungsergebnisse, Deutsche Forschungsgemeinschaft, Reihe C Geologie und Geophysik, Gebrüder Bornträger, Berlin, Stuttgart, C8, 37-83

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The sandfraction of the sediment was analysed in five cores, taken from 65 m water depth in the central and eastern part of the Persian Gulf.
The holocene marls are underlayn by aragonite muds, which are probably 10-11,000 years old.
1. The cores could be subdivided into coarse grained and fine grained layers. Sorting is demonstrated by the following criteria:
With increasing median values of the sandfraction
- the fine grained fraction decreases within each core;
- the median of each biogenic component, benthonic as well as planktonic, increases;
- the median of the relict sediment, which in core 1179 was carried upward into the marl by bioturbation, increases;
- the percentages of pelecypods, gastropods, decapods and serpulid worms in the sandfraction increase, the percentages of foraminifera and ostracods decrease;
- the ratios of pelecypods to foraminifera and of decapods to ostracods increase;
- the ratios of benthonic molluscs to planktonic molluscs (pteropods) and of benthonic foraminifera to planktonic foraminifera increase (except in core 1056 and 1179);
- the ratio of planktonic molluscs (pteropods) to planktonic foraminifera increases;
- the globigerinas without orbulinas increase, the orbulinas decrease in core 1056.
Different settling velocities of these biogenic particles help in better understanding the results : the settling velocities, hence the equivalent hydrodynamic diameters, of orbulinas are smaller than those of other globigerinas, those of planktonic foraminifera are smaller than those of planktonic molluscs, those of planktonic molluscs are smaller than those of benthonic molluscs, those of pelecypods are smaller than those of gastropods.
Bioturbation could not entirely distroy this “grain-size-stratification".
Sorting has been stronger in the coarse layers than in the finer ones. As a cause variations in the supply of terrigenous material at constant strength of tidal currents is suggested. When much terrigenous material is supplied (large contents of fine grained fraction) the sedimentation rates are high: the respective sediment surface is soon covered and removed from the influence of tidal currents. When, however, the supply of terrigenous material is small, more sandy material is taken away in all locations within the influence of terrigenous supply.
Thus the biogenic particles in the sediment do not only reflect the organic production, but also the influence of currents.
2. There is no parameter present in all cores that is independently variable from grain size and can be used for stratigraphic correlation. The two cores from the Strait of Hormus were correlated by their sequences of coarse and fine grained layers.
3. The sedimentation rates of terrigenous material, of total planktonic and benthonic organisms and of molluscs, foraminifera, echinoids and ophiuroids are shown in table 1 (total sediment 6.3-75.5 cm/1000 yr, biogenic carbonate 1.9-3.6 cm/1000 yr). The sedimentation rates of benthonic organisms are nearly the same in the cores of the Strait of Hormus, whereas near the Central Swell they are smaller.
In the upper parts of the two cores of the Strait of Hormus sedimentation rates are higher than in the deeper parts, where higher median values point to stronger reworking.
4. The sequence of coarse and fine grained intervals in the two cores of the Hormus Strait, attributed to variations in climate, as well as the increase of terrigenous supply from the deeper to the upper parts of the cores, agrees with the descriptions in the literature of the post Pleistocene climate as becoming more humid.
The rise of sea level is sedimentologically not measurable in the marly sediments - except perhaps for the higher content of echinoids in the lower part of core 1056. These may be attributed to the influence of a migrating wave-base.
5. The late Pleistocene aragonite mud is very fine grained (> 50%< 2 p) and poor in fossils (0.5-1.8%) biogenic particles of total sediment. The sand fraction consists almost entirely of white clumps, c. 0.1 mm in diameter (1177), composed of aragonite needles and of detrital minerals with the same size (1201). The argonite mud was probably not formed in situ, because the water depth at time of formation was at most 35 m at least 12 m.
The sorting of the sediment (predominance of the fine grained sand), the absence of larger biogenic components and of pellets, c. 0.2-0.5 mm in diameter, which are typical for Recent and Pleistocene locations of aragonite formation, as well as the sedimentological conditions near the sampling points, indicate rather a transport of aragonite mud from an area of formation in very shallow waters.
Sorting as well as lenticular fabric in core 1201 point to sedimentation within the influence of currents. During alternating sedimentation - and reworking processes the aragonitic matrix was separated from the silt - and sand-sized minerals. The lenses grade into touches because of bioturbation.
6. In core 1056 D2 from Hormus Bay the percentages of organic carbon, total nitrogen and total carbonate were determined. With increasing amounts of smaller grain sizes the content of organic matter increases, whereas the amount of carbonate decreases. The amounts of organic carbon and of nitrogen decrease with increasing depth, probably due to early-diagenetic decomposition processes.
Most of the total nitrogen is of organic origin, only about 10% may well be inorganically fixed as ammonium-nitrogen. In the upper part of the core the C/N-ratio increases with increasing depth. This may be connected with a stronger decomposition of nitrogen-containing organic compounds. The general decrease of the C/N-ratios in the lower part of the core may be explained by the relative increase of inorganically fixed ammonium-nitrogen with decreasing content of organic matter.
Median Latitude: 26.762333 * Median Longitude: 55.679917 * South-bound Latitude: 26.316667 * West-bound Longitude: 52.093000 * North-bound Latitude: 27.516000 * East-bound Longitude: 56.913333
Date/Time Start: 1965-04-11T00:00:00 * Date/Time End: 1965-04-14T00:00:00
GIK01177 (M1_355B 01177-C) * Latitude: 27.516000 * Longitude: 52.093000 * Date/Time: 1965-04-11T00:00:00 * Elevation: -65.0 m * Recovery: 2.53 m * Location: Persian Gulf * Campaign: M1 (IIOE - International Indian Ocean Expedition) * Basis: Meteor (1964) * Method/Device: Kasten corer (KAL)
GIK01201 (M1_379) * Latitude: 26.900000 * Longitude: 56.800000 * Date/Time: 1965-04-14T00:00:00 * Elevation: -64.0 m * Location: Persian Gulf * Campaign: M1 (IIOE - International Indian Ocean Expedition) * Basis: Meteor (1964) * Method/Device: Gravity corer (Kiel type) (SL)
IOE1056 (M1056D) * Latitude: 26.316667 * Longitude: 56.913333 * Elevation: -65.0 m * Location: Indian Ocean * Campaign: M1 (IIOE - International Indian Ocean Expedition) * Basis: Meteor (1964) * Method/Device: Gravity corer (GC)
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