A multi-proxy environmental and limnologic paleo-reconstruction of two lakes in Southern Saskatchewan recording the past 6,700 cal. years BP based on ostracods

Abstract

Paleoenvironmental and paleolimnological reconstructions are of great importance to understand future responses of the environment to climate change and environmental stress. Two lake archives, Deep Lake and St. Denis – Pond 1, are used to understand past environmental and limnological conditions in the northernmost part of the Great Plains of North America. Climatic conditions are inferred from the lake sediments and the ostracod assemblage for the Mid- to Late-Holocene (6,700 to 120 cal. yr BP). Mainly, dry conditions with shorter wetter conditions prevailed during the Mid-Holocene as suggested by the presence of a depositional hiatus from 6,302 to 4,366 cal. yr BP and evidences for wetter periods inferred from the bulk-sediment chemistry (Al, Si, K, Fe, K/Ti, Fe/Ti and Mn/Ti), the stable isotopes (ẟ18O, ẟ13C), and the trace element composition of the ostracod valves (Mg/Ca, U/Ca, Fe/Ca). The Late-Holocene displays overall centennial cyclicity fluctuations between wet and dry periods but mostly dry during the last 2,000 years. Both Deep Lake and St. Denis – Pond 1 records seem to respond to regional changes although the period between 2,714 and 1,691 cal. yr BP appear to be responding to local rather than regional forcings due to the moist signature that presents like some but not all the lakes in the northern Great Plains. Likewise, the Medieval Warm Period is recorded by the record of St. Denis – Pond 1, in which dry conditions were inferred.