Late Holocene environmental changes reconstructed from stable isotope and geochemical records from a cushion-plant peatland in the Chilean Central Andes (27°S): LATE HOLOCENE CUSHION PEATLAND RECORDS

A Late Holocene paleoenvironmental record was obtained from the Lagunillas cushion peatland (LP, 27 degrees 12 ' S, 69 degrees 17 ' W), located in the dry Puna of the western Central Andes. Ten radiocarbon dates build the chronology for the last 1800 cal a BP. Analyses of stable isotopes on cellulose (delta O-18(cell), delta C-13(cell)) and geochemical proxies on organic matter (delta C-13(OM), delta N-15(bulk), TOC, TN, LOI, T-535) were conducted to identify major paleoenvironmental changes in this record. Simultaneously, ambient water (delta O-18, delta H-2) and plant samples of the dominant species Oxychloe andina (delta O-18(cell), delta C-13(cell)) reveal insights into modern conditions. The record reveals distinct multi-centennial oscillations of peat layer thickness and delta O-18(cell). Decomposition, changes in the dominating plant species as well as in plant parts (leaves/roots) can be excluded as driving factors for these oscillations. Thus, delta O-18(cell) seems to be externally forced and reflects humidity changes. Around 470 cal a BP a distinct change towards increased humidity occurred, lasting during the Little Ice Age until about 70 cal a BP. Humid conditions prevailed between 1530 and 1270 cal a BP. Increasing delta O-18(cell) values since 30 cal a BP mark a trend towards again increased aridity.