Late Holocene environmental changes reconstructed from stable isotope and geochemical records from a cushion‐plant peatland in the Chilean Central Andes (27°S)

Abstract

ABSTRACT A Late Holocene paleoenvironmental record was obtained from the Lagunillas cushion peatland (LP, 27°12′S, 69°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 (δ 18 O cell , δ 13 C cell ) and geochemical proxies on organic matter (δ 13 C OM , δ 15 N bulk , TOC, TN, LOI, T 535 ) were conducted to identify major paleoenvironmental changes in this record. Simultaneously, ambient water (δ 18 O, δ 2 H) and plant samples of the dominant species Oxychloe andina (δ 18 O cell , δ 13 C cell ) reveal insights into modern conditions. The record reveals distinct multi‐centennial oscillations of peat layer thickness and δ 18 O 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, δ 18 O 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 δ 18 O cell values since 30 cal a BP mark a trend towards again increased aridity.