Episodic preservation of pteropod oozes in the deep Northeast Atlantic Ocean: Climatic change and hydrothermal activity

Abstract

An up to 13 cm thick pteropod ooze covers the ocean floor of the Northeast Atlantic Ocean at Five stations between 44°N and 48°30′ N at around 25°W at water depths of between 2800 and 3200 m. Subsurface pteropod horizons occur at least at two different stratigraphic levels. Pteropod shells, both from the surface layers and from the subsurface horizons, are FeMn stained, with an intensity of staining that increases with age. AMS 14C ages of single pteropods are between 1700 yrs B.P. and the Present for the surface layer, and between 7600 and 3300 yrs B.P. for the upper horizon in the sediment. The Mn/Fe ratios of the pteropod coatings are between 0.24 and 0.40, indicating a hydrothermal source. Apparently, episodic pteropod preservations record pulses of hydrothermally derived, elevated Mn and Fe concentrations. We conclude that pteropod preservation is the combined result of episodic, climatically induced non-dissolution, and subsequent hydrothermally induced protective FeMn coating.