Geochemical and microfossil records from a late-Holocene sediment core from Laguna María Aguilar, Costa Rica

Keywords: Charcoal, pollen, stable carbon isotope, late-Holocene, paleovegetation
Session Type: Virtual Poster Abstract
Day: Sunday
Session Start / End Time: 2/27/2022 03:40 PM (Eastern Time (US & Canada)) - 2/27/2022 05:00 PM (Eastern Time (US & Canada))
Room: Virtual 27

Abstract

Charcoal, pollen, and geochemical analyses of lake-sediment cores provide proxy evidence of past environmental conditions and of prehistoric human disturbance to the landscapes. Pollen assemblages and geochemical data serve as indicators of anthropogenic and natural vegetation change while charcoal accumulation provides insights into past fires. This multi-proxy study focuses on a lake-sediment core recovered from Costa Rica. Laguna María Aguilar is a small (2.7 ha), moderately deep (6.9 m) freshwater lake located at an elevation of 770 m on the Atlantic slope of the Cordillera Central of Costa Rica. Laguna María Aguilar appears to be dammed by a volcanic mudflow associated with eruptions of the Hule crater or Volcán Congo. Three piston sediment cores were recovered from Laguna María Aguilar in 1988 for paleoenvironmental study; we focus here on a 4.7 m long core from the center of the lake. Radiocarbon dating of the sediment core indicates that it extends to ca. 3000 cal yr BP. We present analyses of 26 bulk sediment sub-samples for δ13C, δ15N, and C:N and compare these geochemical proxies with sediment organic content, pollen percentages, and microscopic charcoal concentrations, mainly from adjacent, co-eval samples. This work is the first stage in an ongoing analyses of compound-specific carbon and hydrogen stable isotope compositions of n-alkanes from the core that will yield further insight into paleovegetation and will document paleoprecipitation variability at the site during the late Holocene.