Planktonic assemblages during sapropel S5 deposits in the Urania Basin

A micropaleontological study of planktonic assemblages on the partially laminated sapropel S5 (late Pleistocene, marine isotope stage (MIS) 5e) was performed in two piston cores from Urania Basin area (eastern Mediterranean, west of Crete): UM94PC16 and UM94PC31 recovered during a PALEOFLUX Project Cruise. The abundance of Florisphaera profunda indicates the development of a deep chlorophyll maximum (DCM) before the anoxic condition at bottom were established, whereas patterns of upper photic zone coccoliths suggest extreme oligotrophy in surface water. The short appearance of Globorotalia scitula and the presence of Globigerinoides ruber in the lower part of sapropel testify to a thermal stratification, also recorded by changes in primary producers. During G. scitula occurrence, diatoms, mainly represented by Pseudosolenia calcar-avis, appear and bloom because of their capability in using nutrients from DCM. Scanning electron microscope analyses performed on selected intervals from UM94PC16 show that the sapropel is organized in microlaminae mostly composed by siliceous microfossils. In particular, sapropel S5 could be related to an enhanced nutrient availability in the lower-middle part of the photic zone, stratified conditions, and a higher continental input.

Late Miocene to Holocene planktonic foraminifers from ODP Leg 108 holes

Planktonic foraminifers were examined from 27 holes situated at 12 separate sites in the tropical Atlantic. The sites are located in various environments, including areas of upwelling, areas affected by cool currents, areas of strong dissolution, and areas that show little dissolution in warm-water settings. Paleomagnetic results were variable at these sites, but accumulation rate curves have been produced by combining the existing paleomagnetic data with the available microfaunal data. Determinations of the ages of the planktonic foraminifer datums from these accumulation rate curves show some species to be strongly diachronous, while others provide good stratigraphic markers. The warmest water sites with the least dissolution show the most complete ranges of species.

Oxygen and carbon isotopes of planktic foraminifera and ageprofile datum description at DSDP Hole 69-504

A detailed oxygen isotope record (resolution: about 2500 years) has been obtained for the Pleistocene sediments at Hole 504. Preliminary measurements made deeper in the section suggest that at least the upper Pliocene section is also amenable to detailed stable isotope work. The record for the middle Pleistocene resembles that obtained previously from piston cores in the western equatorial Pacific, although the superior resolution of this high-accumulation-rate site reveals a greater amplitude of isotope variation than previously observed. The record for the lower Pleistocene reveals variation that is both greater in amplitude and higher in frequency than apparent from previously analyzed piston cores. The site provides the best material recovered to date for the study of the evolution of climatic variability during the past few million years.