Rare earth elements in the ornithogenic sediments from the Maritime Antarctic: A potential new palaeoecology proxy

Abstract

The ornithogenic sediments in the maritime Antarctic are good archives for studying the changes of historical penguin population. Rare earth elements (REEs) along with biological and lithophile elements in two lacustrine sediment cores (Y2 and Y4) influenced by penguin droppings were analyzed with the aim of evaluating their potential as a new palaeoecological proxy. The relative concentrations of REEs in the two cores show dramatic changes, and the average REE contents are 71.21 ± 11.56 (n = 37) and 37.18 ± 10.64 (n = 18) for Y2 and Y4, respectively. The REE light/heavy content ratios (L/H) are 4.48 ± 0.59 for Y2 and 4.70 ± 0.62 for Y4, very close to the mean ratio of four pure guano samples. The chondrite-normalized REE patterns in the Y2 and Y4 sediments significantly influenced by penguin droppings are characteristic of more fractionation, obviously negative Ce anomalies and positive Er anomalies, likely imprinting the REE signal of guano input. The total REE concentration has a statistically significant negative correlation with the levels of guano-derived bio-elements and a positive correlation with the levels of Sc and Al mainly originated from weathered soils. The calculated proportion of guano-derived REE based on two-member mixing equation has a change pattern consistent with that of the historical penguin population size, previously reconstructed from bio-element concentrations in the sediments. These results suggest that the non-crustal signature of REE in the ornithogenic sediments may provide a new palaeoecological proxy for studying the palaeoecological processes of Antarctic penguins on a large time scale.