Vegetation, glacier, and climate changes before the global last glacial maximum in the Isla Grande de Chiloé, southern Chile (42° S)

Abstract

Climatic and vegetation features of the mid-latitudes of the Southern Hemisphere before the global Last Glacial Maximum (gLGM) are still a matter of discussion. The signatures of Marine Isotope Stage (MIS) 3 show strong variability at the poles that has not yet been resolved at lower latitudes. This work discusses one of the first terrestrial records that reflects the vegetation, glacier, and climate conditions in southern South America during this period. The stratigraphic, palynological, and geomorphological features of the Punta Pihuío, Río Huicha, Punta Pirquén and Punta Detico sites (41–42° S) on the Isla Grande de Chiloé (southern Chile) are described and discussed. Glacially sourced sediment intercalated with peat soils constrained by single-grain feldspar (SGIR50) luminescence and radiocarbon (14C) dating show that the Late MIS 5 and the MIS 3 were periods of high environmental variability at these locations. Pollen records from peat layers indicate an open forest with conifers, Nothofagus and thermophilic elements, such as Myrtaceae, representing interstadial conditions that were abruptly interrupted by glacial expansions during stadials. High variability between arboreal and herbaceous taxa is also interpreted as environmental instability. Moreover, we show that the Patagonian Ice Sheet (PIS) reached full glacial extent during Early to Middle MIS 3, as is also observed in other Southern Hemisphere glacier records on both sides of the Pacific Ocean. Our data support that millennial-to multi-millennial-scale climate changes characterized the pre-gLGM not only at the poles, but also at the southern mid-latitudes.