Impact of hydrothermal activity on carbonate fossils in bottom sediments of the tropical Atlantic

• Published in: Oceanology (Washington. 1965) 2015-02, Vol.55 (1), p.100-111
• Main Authors: Gablina, I. F., Dmitrenko, O. B., Os’kina, N. S., Khusid, T. A., Popova, E. A.
• Format: Article
• Language: English
• Subjects: Bottom sediments; Carbonate sediments; Earth and Environmental Science; Earth Sciences; Foraminifera; Fossils; Geochemistry; Geological time; Holocene; Marine; Marine Geology; Mineral composition; Oceanography; Pleistocene; Tropical environments; Vertical distribution
• ISSN: 0001-4370; 1531-8508
• DOI: 10.1134/S0001437015010051

The chemical and mineral composition of the bottom sediments, as well as the assemblages of carbonate planktonic and benthic fossils (nannoplankton, foraminifers), were analyzed in two cores obtained in the North Atlantic within the Peterburgskoe hydrothermal ore field and beyond its limits. Their sections include the Upper Pleistocene and Holocene sediments with the boundary between them located at the depth of 20 cm. It is established that planktonic fossils (foraminifers and nannoplankton) reflect the replacement of subtropical conditions in the Late Pleistocene by tropical environments in the Holocene. It is shown that hydrothermal fluids significantly affect biogenic carbonate sediments in the ore formation zone of the Peterburgskoe field (core 33L159) resulting in dissolution of microfossils and their replacement by hydrothermal material. Their transformation patterns and vertical distribution indicate the influx of diffuse acid solutions to sediments from below. In background sediments constituting the core 33L148 section located 5 km away from the ore field, microfossils exhibit good preservation through its entire length. The sediments from the basal part of the section demonstrate the slight influence of the aggressive acid medium reflected in the disappearance of pteropod remains and changes in the abundance and taxonomic composition of benthic foraminifers and nannofossils. These data may be used as a criterion for defining potential nearby active hydrothermal sources.