Innovations in Acheulean Biface Production at La Noira (Centre France): Shift or Drift Between 700 and 450 Ka in Western Europe?

The archaeological sequence of la Noira, in the Middle Loire Basin (Centre region, France) yielded two phases of occupation: ca 700 ka (stratum a) and ca 450 ka (stratum c). No site between these two dates has yet been discovered in the area, and this chronological period has thus been interpreted as a gap in settlement from MIS 16 to MIS 12. Here, we compare these two levels and track technological innovations or/and inventions during this time, based on the technological and morphometric comparison of the Large Cutting Tools (LCTs), applying a new method of analysis. We explore inter and intra-level variability in order to address the hypotheses of (1) the filiation over time of populations settling sporadically in the region or (2) the arrival of new populations from other European or extra-European areas. Stratum a presents mainly short shaping sequences on local millstone, taking advantage of natural slab geometry, and with special attention to tips, but with clear management of tool volume. Stratum c differs in that both local millstone and flints from distant sources show longer shaping sequences, the use of soft hammers for several series of removals, combined with final regularizing retouch on entire edges. The morphometric approach shows a morphological transition from oval to teardrop shapes for the thinnest tools. A technological filiation between strata a and c and between la Noira populations from MIS 16 and MIS 12 in this area has to be considered.

Eutrophication mitigation in rivers: 30 years of trends and seasonality changes in biogeochemistry of the Loire River (1980–2012)

Trends and seasonality analysis since 1980 and longitudinal distribution from headwaters to estuary of algal pigment, nitrate and phosphate were investigated in the eutrophic Loire River. The continuous decline of phosphate concentrations recorded since 1991 both in the main river and in the tributaries led to a significant reduction in algal biomass across the whole river system. While eutrophication remained lower in the main tributaries than in the Loire itself, they were found to contribute up to 45% to the total nutrient load of the main river. The seasonality analysis revealed that the river has always been under P limitation, explaining why reducing P inputs led to decreasing eutrophication in the whole Loire basin. The decline of seasonal amplitudes of algal pigments reduced the seasonal amplitude of phosphate and of daily variations of dissolved oxygen and pH but did not significantly affect the seasonal amplitude of nitrate. Thus, algal uptake responsibility on the summer nitrate loss seemed to be declining, questioning the exact role played by denitrification, terrestrial vegetation and fixed aquatic vegetation on the nitrogen cycle.