Late Holocene precipitation variability recorded in the sediments of Reloncavi Fjord (41 degrees S, 72 degrees W), Chile

Abstract

We present reconstructions of late Holocene changes in the source of organic matter and siliceous export production in the Relocanvi Fjord (41 degrees S, 72 degrees W), Northern Chilean Patagonia, based on organic carbon content, delta C-13(org), N/C ratio, diatom assemblages and biogenic silica contents from three sediment cores. The age models are based on a combination of Pb-210 profiles, AMS C-14 dating, and on the first occurrence of the diatom Rhizosofenia setigera f. pungens, as a stratigraphic marker in the fjords. The cores span the last 300 to 700 yr. Diatoms dominate the siliceous assemblages in the three cores (98% on average). Our results suggest that precipitation seasonality in the region of Reloncavi was high in CE 1300-1400 and CE 1700-1850, with a clear decreasing trend since CE 1850. The latter trend is in agreement with instrumental records and tree-ring reconstructions. These fluctuations seem to be associated with the Southern Annular Mode (SAM).