Late Quaternary paleoenvironments of an ephemeral wetland in North Dakota, USA: Relative interactions of ground-water hydrology and climate change
Catherine H. Yansa, W.E. Dean and E.C. Murphy
This study of fossils (pollen, plant macrofossils, stomata
and fish) and sediments (lithostratigraphy and geochemistry) from the Wendel
site in North Dakota, USA, emphasizes the importance of considering ground-water
hydrology when deciphering paleoclimate signals from lakes in postglacial
landscapes. The Wendel site was a paleolake from about 11,500 14C yr BP to
11,100 14C yr BP. Afterwards, the lake-level lowered until it became a prairie
marsh by 9,300 14C yr BP and finally, at 8,500 14C yr BP, an ephemeral wetland
as it is today. Meanwhile, the vegetation changed from a white spruce parkland
(11,500 to 10,500 14C yr BP) to deciduous parkland, followed by grassland at
9,300 14C yr BP. The pattern and timing of these aquatic and terrestrial changes
are similar to coeval kettle lake records from adjacent uplands, providing a
regional aridity signal. However, two local sources of ground water were
identified from the fossil and geochemical data, which mediated atmospheric
inputs to the Wendel basin. First, the paleolake received water from the melting
of stagnant ice buried under local till for about 900 years after glacier
recession. Later, Holocene droughts probably caused the lower-elevation Wendel
site to capture the ground water of up-gradient lakes.