Holocene sedimentation history of the shallow Kangerlussuaq lakes, West Greenland

Abstract

The sedimentation history and Holocene development of seven small and shallow closed-basin lakes in the continental Kangerlussuaq region of West Greenland was studied by detailed analysis of their sedimentary infill, chronology, and litho- and chronostratigraphy of sediment cores. The lakes are situated between the present-day Inland Ice margin and Sukkertoppen Iskappe and have generally simple basin morphometries. Accumulation and distribution of organic rich sediments indicate a rather regular lake infill since deglaciation. According to AMS ¹⁴C ages of basal organic sediments, start of organic infill in the lakes follows the general timing for deglaciation as defined by regional moraine chronostratigraphy, but include evidence for the diachronous development of individual lakes. Holocene accumulation rates of organic-rich sediments were rather constant over time, and the longest record extends back to ca. 10,500 cal yrs B.P. Floristic shifts in the first diatom record presented from this area record significant limnological changes, with relatively mesotrophic conditions prevailing throughout lake history. Results of high-resolution losson-ignition (LOI) analysis on diatomaceous and silt-rich organic sediments suggest a dominant lacustrine signal in these lakes. A characteristic sedimentary sequence occurs in all lakes investigated where highly variable LOI fluctuations show a close correlation between sites, well corroborated by radiocarbon ages. The results are discussed in the context of on-going investigations of the palaeoenvironmental and climatic record in the continental interior of West Greenland and present information on the environmental background, basin characteristics, sediment stratigraphy, and chronostratigraphy of the shallow Kangerlussuaq lakes.