Geocheinical studies of sediments from the gulf of paria, venezuela; and the Atlantic ocean north of the Faeroe islands

Abstract

Section 1 is concerned with the geochemistry of sub-samples taken from a suite of 5 piston cores collected over the southern part of the Iceland-Faeroes Rise in the North Atlantic Ocean. The samples were taken in 1968 during Cruise No. 14 of the R.V. Meteor of the Deutsches Hydrographisches Institut. The Iceland-Faeroes Rise appears to have acted as a barrier, resulting in a high proportion of terrigenous material in the sediment accumulating on the eastern side. The sediment east of the Rise contains a relatively high proportion of material derived from a source area which includes metamorphic rocks. True marine sedimentation, i.e., precipitation of CaC0(_3), becomes important in the stations west of the Rise. Iceland appears to have overprinted the sediments by the introduction of volcanic glass, the greater proportion of which occurs in the cores east of the Rise. The distribution of volcanic debris may have resulted in part from the prevailing westerly winds. Bottom currents flowing westwards over the Rise appear to have carried either the fine fraction of the volcanic glass or its alteration products into the Atlantic Basin. Section 2 deals with the geochemistry and mineralogy of a suite of sediment samples collected from the Boca Vagre estuary on the southern margin of the Gulf of Paria. These sediments were collected in 1963 during Cruise 55 of the R.V. Chain, of Woods Hole Oceanographic Institution. Variation in the major element geochemistry and mineralogy are studied in the light of earlier works on the geochemistry and sedimentation rates in the area. The results indicate a distinct change in sedimentation over the pro-delta region, which is reflected in the amount of resistant material in the sediment, and also in the amount, and possibly the composition of the hydrolysate fraction. Variations in pH, and sedimentation rate noted by earlier workers, are reflected in the carbonate content, which shoves an increase out into the Gulf. Changes observed in the minor element population are consistent with an increase in the content of the hydrolysate fraction. The proportion of illite and montmorillonite in the hydrolysate fraction would appear to be constant, from evidence provided by the results of Factor Analysis.