Resolving the chronology of recent lake sediments: an example from Devils Lake, North Dakota

Abstract

Devils Lake is a closed, saline lake in North Dakota; it is typical of lake basins in the Great Plains Region, where windy conditions and fluctuating water-levels disturb sediment and confound chronostratigraphy. Pollen analysis and 2mpb dating of two cores collected from bathymetrically contrasting embayments demonstrate (1) how certain agriculture-related pollen types differ in their value as chronostratigraphic markers, (2) how pollen and 2mpb stratigraphies can be reconciled to determine the approximate depth of sediment mixing, and (3) the importance of coring-site selection, especially in lakes with unstable sedimentary conditions.

Paleolimnological Evidence of Terrestrial and Lacustrine Environmental Change in Response to European Settlement of the Red River Valley, Manitoba and North Dakota*

“…Overall, the pollen successions we observe in Horseshoe and Salt lakes agree well with the pollen successions from Lake Louise, Manitoba (Brooks and Grenier, 2001), Devils Lake (Jacobson and Engstrom, 1989) and Waubay Lake (Shapley et al, 2005), North Dakota. The pre-settlement period is dominated by the herbaceous taxa of Ambrosia, Artemisia, and Gramineae at Horseshoe Lake and by Ambrosia, Chenopodiineae and Artemisia at Salt Lake.…”

“…3-4 in Medioli and Brooks, 2003). This pattern of nonlinear sedimentation pattern may explain why 210 Pb dating was unsuccessful, and is supported by Jacobson and Engstrom's (1989) (Burbidge and Schröder-Adams, 1999), is the most abundant taxa in Zone I. This suggests oligotrophic lake conditions during the pre-settlement period.…”

“…In Zone I the pollen assemblage consists of abundant tree pollen (Quercus: 30-40% and Ulmus: 5-9%) similar to the tree taxa observed in the modern Red River riparian forest. Herbaceous pollen (Gramineae:~5%, Ambrosia: 7-12%, Artemisia: 4-9% and Chenopodiineae: 1-4%) are also present, and represent a tall grass prairie habitat (Jacobson and Engstrom, 1989). The beginning of Zone II is marked by a decline in tree pollen (mainly Quercus and Ulmus) and an associated rise in herbaceous pollen (e.g., Gramineae, especially cereal grasses, Tubulifloreae and Ligulifloreae), as well as weed species (Ambrosia, Artemisia and Chenopodiineae).…”

“…3A, 4A) in the North American mid-west. Jacobson and Engstrom (1989) report the arrival of Salsola in North Dakota by 1888-1891. Once the plant arrived at the Red River, it would have spread quickly downstream and throughout the watershed.…”

“…Limnological studies in the eastern Canadian and American prairies have broadened the understanding of the deglacial history of the Northern Great Plains (Last, 1982(Last, , 1983(Last, , 1999Last et al, 1994;Last, 1981, 1983) and on Holocene climatic changes (Henderson and Last, 1999;Tackman et al, 1999;Todd et al, 1999aTodd et al, , 1999b, particularly with respect to aridity (Anderson et al, 1993;Bradbury and Dean, 1993;Bradbury and Dietrich-Rurup, 1993;Brugam, 1993;Lemmen and Vance, 1999;Nuhfer et al, 1999;Whitlock et al, 1999). Only a handful of studies, however, have documented recent changes during the last few centuries, dealing with eutrophication (Burbidge and Schröder-Adams, 1998;Torigai et al, 2000), shoreline submergence (Nielsen, 1999), vegetation change from tall grass prairie to agricultural landscape (Brooks and Grenier, 2001;Jacobson and Engstrom, 1989) and increased sedimentation (Brooks and Grenier, 2001;De Boer, 1994;Shapley et al, 2005).…”