Late-glacial and Holocene palaeoenvironmental change in the central Strait of Magellan, southern Patagonia

Abstract

High-resolution palaeoenvironmental data for the Wisconsin Late-glacial and early Holocene is provided from two sites, Puerto del Hambre and Estancia Esmeralda II, in the central section of the Strait of Magellan, southern Chile. Palaeoecological and lithostratigraphical evidence is correlated with other palaeoenvironmental data from the Magellan region using 14C dating and tephrochronology. The oldest record, from Puerto del Hambre, commences at 14,470 14C yr bp (17,330 cal. yr bp), following retreat of the Magellan glacier. Climatic warming after that time is indicated by ice retreat from the central section of the Strait of Magellan and palynological evidence. However, mean annual temperature continued to be cooler than present until c. 10,300 14C yr bp (12,270–12,110 cal. yr bp). The Magellan environment was relatively humid between c. 14,100 and c. 12,550 14C yr bp (16,910 and 15,170–14,410 cal. yr bp). At c. 12,550 14C yr bp, there was a sharp decrease in effective moisture. Levels of humidity fluctuated, but remained relatively low until c. 10,300 14C yr bp. This period of cool and drier climate is contemporary with a significant glacier advance dated to between c. 12,700 and 10,300 14C yr bp (15,330 and 12,270–12,110 cal. yr bp), which would have produced an enhanced rainshadow effect. Around 10,300 14C yr bp a shift to warmer conditions occurred. Between c. 10,300 and 8550 14C yr bp (12,270–12,110 and 9530 cal. yr bp) an extreme arid phase is recorded, which led to an increase in fires. At c. 8550 14C yr bp an increase in available moisture allowed the eastward spread of Nothofagus forest. At 8265 14C yr bp (9270–9160 cal. yr bp) there was a relative rise in sea level in the Strait of Magellan. This marine incursion lasted until 3970 14C yr bp (4420 cal. yr bp), reaching its maximum around c. 6450 14C yr bp (7420–7340 cal. yr bp).