Abstract

Due to their location at the southern margin of the Arid Diagonal, only a limited number of archives in the western Central Andes of Chile is capable for paleoclimate investigations. High-altitude cushion peatlands are potentially suitable to fill this gap despite their heterogenic stratigraphies representing past geomorphodynamics, especially for the Late Holocene. We investigated a 4 m sediment profile from the Lagunillas cushion peatland (LP, 27'12' S, 69 degrees 17 W), located in the dry Puna of the Western Central Andes. Directed by Electrical Resistivity Tomography (ERT) measurements, sediment cores were recovered at the deepest point of the investigated valley section. In total, 10 radiocarbon samples were used to build the age-depth model resulting in a sediment chronology spanning the last 1800 cal. yr BR Core stratigraphy and ERT data were applied to allow insights into the sedimentary environment. Geochemical (X-ray fluorescence) and sedimentological (grain size) analyses were conducted to identify significant changes in sedimentation dynamics during the Late Holocene. Grain size analyses were investigated on 24 samples from peat layers as well as from stratigraphical sections characterized by allochthonous sediments. In combination with the results of the XRF measurements, evidence for changes in geomorphodynamic processes during the last 1800 cal. yr BP could be revealed. Our data disclose that investigations of heterogenic peat stratigraphies could also provide promising inferences about paleoclimatic changes. Within the Lagunillas record, stable phases of peat accumulation alternate with phases dominated by clastic material input. A stable phase of peat accumulation prevailed from 1750 cal. yr BP until about 1250 cal. yr BP and was followed by a phase with unstable conditions from 1250 to 980 cal. yr BP. During the Medieval Climate Anomaly (MCA) between 980 to 620 cal. yr BP, drier conditions prevailed at Lagunillas peatland, while shorter humid periods favored peat accumulation between 620 to 560 cal. yr BR Higher precipitation amounts were evident during the Little Ice Age (LIA) from 560-160 cal. yr BR During the period from 160 cal. yr BP to recent times, a higher frequency of changes between peat accumulation and clastic layers occurred, presumably due to a decreasing trend in precipitation.