Stable oxygen isotope data of Globigerinoides ruber white and titanium intensity from sediment core GeoB6211-2

The South American summer monsoon (SASM) is the main source of precipitation for the most densely populated and agriculturally productive regions of tropical and subtropical South America. Here we investigate the impact of the Atlantic Multidecadal Oscillation (AMO) on the SASM using ~4500 yr long proxy records of the discharge variability of the La Plata River Drainage Basin (PRDB), subtropical South America. We measured the stable oxygen composition of planktic foraminifera (related to the extension of the PRDB plume), and Ti intensity in bulk sediment (related to the source of the terrigenous sediments) from a marine sediment core. Spectral and wavelet analyses of our records indicate an oscillation with period of ~64 yr. We conclude that the observed oscillation reflects variability in the SASM activity associated to the AMO. Sea surface temperature and atmospheric circulation anomalies triggered by the AMO would control the variability in SASM activity.

Cretaceous nannofossils of southeast France

The Aptian-lower Albian succession of the Vocontian Basin (SE France) consists of marine hemipelagic sediments including several black shale horizons. The latter are partly of regional and partly of global distribution. This sedimentary succession records the nannoplankton evolution of the Aptian-early Albian interval and thus provides an excellent opportunity to calibrate the calcareous nannofossil record with Tethyan ammonite and planktic foraminiferal biostratigraphy. The calcareous nannofossil biostratigraphy presented in this paper supports previous zonations, but it also provides a much higher resolution and thus improves the correlation of different black shale horizons on a supraregional scale. Up to 23 major (supraregionally significant) and minor (regionally significant) first and last occurrences of calcareous nannofossil taxa are recognized. Nannoconid abundances decrease rapidly in the upper Lower Aptian (nannoconid crisis I, NCI) and in the middle Upper Aptian (nannoconid crisis II, NCII). Both decreases correlate with carbonate-platform drowning events. The upper Lower Aptian interval above the NCI is characterized by high abundances of large specimens of Assipetra infracretacea and Rucinolithus terebrodentarius probably of supraregional significance. The uppermost Aptian-Lower Albian is characterized by high abundances of the calcareous nannoplankton taxon Repagulum parvidentatum, reflecting boreal influence on the Tethyan Realm. This suggests a temporary decrease in surface-water temperatures in the Vocontian Basin.