NOAA/WDS Paleoclimatology - Elk Lake, Minnesota: Evidence for Rapid Climate Change in the north central United States

STUDY NOTES: Geochemical and paleontological data sets for sediments collected from Elk Lake, Minnesota. Sediments were sampled at two different temporal resolutions: 1. The entire varved section (10,200 years) was sampled at coarser resolution, generally 50-year composite samples; and 2. The last 1550 years of the varved record was sampled at contiguous 1-cm intervals, with an average temporal resolution of 5 years (see WDS-Paleo study 5473; https://doi.org/10.25921/ya60-jx62). These data were obtained from a piston core and a frozen box core collected by the U.S. Geological Survey in 1978, and supplemented by additional piston cores collected by the Limnological Research Center, University of Minnesota in 1982, 1983, and 1984. The composite geochemical and paleontological data sets for the last 10,000 years were obtained by splicing information from sections of the 1978, 1982, and frozen box core. The more detailed composite geochemical and paleontological data sets for the last 1550 years were obtained from samples originally taken from the 1983 and 1984 cores for sediment magnetic studies (Sprowl, 1985). Information about the location of Elk Lake, methods of coring, core splicing, construction of the varve chronology, and methods of analyses can be found in the following publications: Bradbury, J.P. and Dean, W.E., 1993, Geological Society of America Special Paper 276, doi: 10.1130/SPE276; Dean, W.E. et al., 1994, U.S. Geological Survey Open-File Report 94-578, doi: 10.3133/ofr94578; Sprowl, D.R., 1985, Ph.D. thesis: University of Minnesota, Minneapolis, 145 p. The Elk Lake Geochemical and Paleontological Data Set for the last 10,000 years consists of data files which contain information about diatoms, pollen, plant pigments, inorganic geochemistry, carbon and oxygen isotopes, and physical properties. The basic sampling scheme for inorganic geochemistry, mineralogy, plant pigments, and diatoms was contiguous 50-year composite samples, although in some instances this sampling scheme was modified, and for most analyses only every other sample collected was analyzed, resulting in a sample density of one 50-year composite sample every 100 years.. Twenty three samples were selected from the inorganic geochemistry sample set for analyses of carbon and oxygen isotopes and Rock-Eval pyrolysis hydrogen and oxygen indices. The basic sampling scheme for pollen and physical properties was a 0.5-cm3 sample centered on every 50th varve, but again not every sample was analyzed, and additional 0.5-cm3 samples were collected for pollen analyses in certain pollen-zone transitions. Regardless of the sampling scheme, each sample is indexed to the central varve in the series (e.g.. sample interval = varve 919 to varve 968 (50 years), sample index = varve 943). Because the Elk Lake paleontological and geochemical data are "centered" by varve number, they can be plotted directly as time-series although the time intervals are not constant. The first column in each of the data files contains the header" VARVE-YR", which indicates the varve number for the center of each sample. The columns with headers "TOP" and "BTM" in each of the data files indicate the distance (in mm) from the sediment-water interface to the top and the bottom of the sample interval. Data files obtained from temporally-sampled material include a column with the header "YR.INTVL", indicating the number of varve years contained in each sample interval.
ABSTRACT SUPPLIED BY ORIGINATOR: Records of past climate and environment derived from lake sediment records. Parameter keywords describe what was measured in this data set. Additional summary information can be found in the abstracts of papers listed in the data set citations.