A multi-proxy reconstruction of past erosion dynamics based on lake sediments from the northern Ecuadorian Andes

Lake sediments in mountain areas worldwide have been analysed to reconstruct erosion dynamics on local to regional scales. In the tropical Andes, an area of globally-relevant biodiversity hotspots and carbon sinks, long-term erosion patterns in response to climate and land use change are poorly known. In this study we examine the local erosion history as archived in a high-elevation (<3,700m asl) caldera lake north of Ecuador’s capital Quito. A multi-proxy approach was conducted on a 72 cm-long lake sediment core retrieved from Caricocha in the Mojanda Lake Region, including visual core description, X-ray fluorescence (XRF) core-scanning, magnetic susceptibility (MS), C/N and grain-size analyses. Two radiocarbon dates were combined with tephra-stratigraphy to derive a viable timeframe for sediment accumulation. Data obtained from XRF, MS, C/N and grain-size analyses were evaluated using multivariate statistical methods. Results from cluster and principal component analysis revealed at least 3 stratigraphic units alternating with at least 8 tephra layers. We will discuss a multi-proxy approach to identify different sedimentary environments, sources of material and underlying patterns in this volcanically active region. Including log-transformed element ratios of the XRF data we report on the challenges to disentangle proxies for past erosion dynamics from further palaeoenvironmental conditions, of relevance for future land use under climate change.