Publication Date:
2016-05-23
Description:
The coarse sediment fraction (〉63 μm) and benthic foraminiferal composition of Quaternary sediment cores from ODP LEG 112 Hole 680B (252.5 m water depth) were sampled from the upwelling area off Peru. High-resolution oxygen isotope stratigraphy based on analyses of the benthic foraminifera Bolivina seminuda allows a detailed reconstruction of the upwelling history since oxygen isotope Stage 16. Variations in the relative abundances of the benthic foraminiferal species Nonionella auris, Bolivina costata, and Bolivina seminuda document changes in fertility, which were found to be enhanced during interglacial Stages 1, 3, 5, 7, 9 and 11. Generally, bioturbated sediments are dominated by the genera Cassidulina, Epistominella, Gyroidina, Trifarina and Valvulineria. These benthic foraminifera are members of the ‘Undercurrent Fauna’, which is commonly associated with sediments that have a high terrigenous detrital component and a low organic carbon content (〈3 wt%). These sedimentary deposits are indicative of high near-bottom current velocities of the Peruvian Undercurrent and well oxygenated bottom waters (0.5 to 〉6 ml/l O2). The entire core interval investigated in Hole 680B appears to have been affected by the Peruvian Undercurrent. Generally, undercurrent-dominated sections were found to correspond with glacial oxygen isotope stages.
Type:
Book chapter
,
NonPeerReviewed
Format:
text
