Explanatory Information for
Geochemical and Paleontological Data Sets
for Elk Lake, Minnesota

	The attached printed listings and the accompanying disk contain geochemical and 
paleontological data sets for sediments collected from Elk Lake, Minnesota and 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.  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., editors, 1993, Elk Lake Minnesota:  Evidence for rapid 
climate change in the north-central United States:  Boulder, Colorado, Geological 
society of America Special Paper 276, 336 p.
Dean, W. E., Bradbury, J. P., Anderson, R. Y., Bader, L. R., and Dieterich-Rurup, K., 
1994, A high-resolution record of climatic change in Elk Lake, Minnesota for the 
last 1500 years:  U. S. Geological Survey Open-File Report 94-578, 127 p.
Sprowl, D.R., 1985, The paleomagnetic record from Elk Lake, Minnesota, and its 
implications [Ph.D. thesis]: University of Minnesota, Minneapolis, 145 p.

Last 10,000 years

	The Elk Lake Geochemical and Paleontological Data Set for the last 10,000 years 
consists of 8 data files which contain information about diatoms, pollen, plant pigments, 
inorganic geochemistry, carbon and oxygen isotopes, and physical properties.  Sampling 
methods and explanatory information pertinent to each data file are presented below.  
Due to the width of some of the data records, which exceed the width of common ASCII-
files, the data files are presented in Lotus (Release 2) spreadsheet format.
	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 8 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.  
	Varve thickness data for Elk Lake are compiled in Allen, B. D. and Anderson, R. 
Y., 1990, Varve Thickness Time-Series, Elk Lake, Minnesota: Data submitted to NGDC.  
Individual thickness measurements (in mm) for 10,224 individual varves are contained in 
a file called "elkvarve.dat".  

Elk Lake Pollen Data File

File Name: elkpolln.wk1
File Size: 36,995 bytes
Sampling Method: 0.5 cm3 sample every 50 varves; not every sample was analyzed, and 
additional samples were collected and analyzed at certain pollen-zone transitions 
Investigator:  Cathy Whitlock, Department of Geography, University of Oregon, Eugene, 
OR 97403.

Data file contains relative percentage of palynomorphs.  Abbreviations for taxa in 
column headers are explained in a file called "elkpolln.txt".  

Elk Lake Diatom Date File

File Name:  elkdiatm.wk1
File Size: 109,308 bytes
Sampling Method: 50-year composite samples; not every sample was analyzed
Investigator: J. Platt Bradbury, U.S. Geological Survey, Federal Center, Denver, CO 
80225

Data file contains relative percentage of diatoms.  Abbreviations for taxa in column 
headers are explained in a file called "elkdiatm.txt". 

Elk Lake Geochemistry Data File

File Name: elkgeoch.wk1
File Size: 76,886 bytes
Sampling Method: 50-year contiguous composite samples; not every sample was 
analyzed
Investigator: Walter E. Dean, U.S. Geological Survey, Federal Center, Denver, CO 
80225

Data file contains results of geochemical analysis for various compounds and elements.  
Headers indicate percentages or concentrations parts per million (ppm) bulk dry weight 
of the various compounds or elements using standard chemical symbols.  The first four 
columns of geochemical data (T-C% through T-S% [%total sulfur]) were obtained using 
a LECO elemental analyzer.  Concentrations of Al, Fe, Ti, Mn, and all  data expressed in 
ppm were analyzed by inductively coupled plasma emission (ICP) . Concentrations of 
Mg and Na were determined by atomic absorption spectroscopy (aa).  Replicate analyses 
of the same sample are indicated with an asterisk (*) in column 5 (header = 
"REP.SMPLS"). 
 
Elk Lake X-Ray Fluorescence Data File
                                 
File Name: elkxrf.wk1
File Size: 39,115 bytes
Sampling Method:  50-year contiguous composite samples; not every sample was 
analyzed
Investigator: Walter E. Dean, U.S. Geological Survey, Federal  Center, Denver, CO 
80225

Data file contains results of geochemical analyses of Si, Al, Fe, Ca, K, Ti, and Mn by X-
ray fluorescence (XRF) spectroscopy.  Results are expressed as percentages of the 
elements and or their respective oxides.  Replicate analyses of the same sample are 
indicated with an asterisk (*) in column 5 (header = "REP.SMPLS").

Elk Lake Mineralogy Data File

File Name: elkminer.wk1
File Size: 23,280 bytes
Sampling Method:  50-year contiguous composite samples; not every sample was analyze 
Investigator: Walter E. Dean, U.S. Geological Survey, Federal Center, Denver, CO  
80225

Data file contains X-ray diffraction (XRD) relative peak heights (in mm) for calcite, 
quartz, dolomite, feldspar, aragonite, and rhodochrosite.  For the two column containing 
peak heights for feldspar, "fspar27" = orthoclase, and "fspar28" = plagioclase.

Elk Lake Physical Properties Data File
 
File Name: elkphysp.wk1
File Size: 21,243 bytes
Sampling Method:  0.5 cm3 sample every 50 varves
Investigator: Walter E. Dean, U.S. Geological Survey, Federal Center, Denver, CO  
80225

Data file contains values of dry bulk density (g/cc) and water content (%).  Replicate 
analyses of the same sample are indicated with an asterisk (*) in column 5 (header = 
"REP.SMPLS").

Elk Lake Isotope Data File

File Name: elkisotp.wk1
File Size: 6829 bytes
Sampling Method:  50-yr composite samples selected from the geochemistry sample set
Investigator: Walter E. Dean, U.S. Geological Survey, Federal Center, Denver, CO  
80225

Data file contains the results of analyses for organic carbon, hydrogen index (mg 
hydrocarbons/g organic carbon), and oxygen index (mg CO2/g organic carbon) using a 
Rock-Eval pyrolysis analyzer, as well as values for ratios of the stable isotopes of carbon 
and oxygen expressed as per mil shifts relative to the PDB marine carbonate standard.  
C-isotope ratios were measured in both organic carbon and bulk CaCO3.

Elk Lake Plant Pigment Data File

File Name: elkpig.wk1
File Size:  13,208 bytes
Sampling Method:  50-yr composite samples selected from the geochemistry sample set
Investigator:  Jon E. Sanger, Department of Botany-Microbiology, Ohio Wesleyan 
University, Delaware OH 43015

Data file contains the results of percent weight loss on ignition (LOI) at 550 and 900 
degrees C, and analyses for total chlorophyll, total carotenoids, epiphasic carotenoids, 
hypophasic carotenoids, and bacterial chlorophyll.  Pigment concentrations are expressed 
as spectrophotometer absorbance units per gram of organic matter (=%LOI-550) 

	Originally submitted to NGDC by Bruce D. Allen and Roger Y. Anderson, 26 
November, 1990.  Modified by Walter E. Dean and J. Platt Bradbury, 17 November, 
1994.

Last 1550 Years

	The Elk Lake Geochemical and Paleontological Data Set for the last 1550 years 
consists of 5 data files which contain information about varve thickness, gray scale 
density, concentrations of organic carbon and CaCO3, X-ray diffraction mineralogy, 
inorganic geochemistry, and diatoms.  The data were originally published as appendixes 
in the USGS Open-File Report 94-578 cited above.  Sampling methods and explanatory 
information pertinent to each data file are presented below.  Due to the width of some of 
the data records, which exceed the width of common ASCII-files, the data files are 
presented in Lotus (Release 2) spreadsheet format.
	The basic sampling scheme for carbon analyses, mineralogy, and diatoms was 
contiguous 1-cm composite samples with an average of 5 varves per sample.  For 
inorganic geochemistry, the sampling interval was contiguous 2-cm composite samples 
with an average of 10 varves per sample.  The first two columns in each of the four 
analytical data files are labeled "Varve Yr BP" and "Varve Yr AD" and contain the 
midpoint of each 1-cm or 2-cm sample in varve years before 1984 and years AD, 
respectively.

Varve Thickness and Gray Scale Data File

File Name:  ofr1varv.wk1
File Size:
Sampling Method:  Varve thickness (in mm) and gray-scale density ranging from 0 
(white) to 255 (black) were measured on scanned images of the cores.
Investigator:  Roger Y. Anderson, Department of Earth and Planetary Sciences, 
University of New Mexico, Albuquerque, NM 87103

Carbon Data File

File Name:  ofr2carb.wk1
File Size:  
Sampling Method:  1-cm contiguoous composite samples
Investigator:  Walter E. Dean, U.S. Geological Survey, Federal Center, Denver,. CO  
80225

Data file contains measured concentration (percent dry weight of sample) of total carbon 
and inorganic carbon.  File also contains percentages of organic carbon, calculated as the 
difference between total carbon and inorganic carbon), and CaCO3, calculated as % 
inorganic C/0.12.

X-ray Diffraction Mineralogy Data File

File Name:  ofr3xray.wk1
File Size:  
Sampling Method:  1-cm contiguoous composite samples
Investigator:  Walter E. Dean, U.S. Geological Survey, Federal Center, Denver,. CO  
80225

Data file contains X-ray diffraction (XRD) relative peak heights (in detector counts) for calcite, 
quartz, dolomite, feldspar, and rhodochrosite.  For the two column containing peak heights for 
feldspar, "FELDSPAR27" = orthoclase, and "FELDSPAR28" = plagioclase.

Inorganic Geochemistry Data File

File Name: ofr4elem.wk1
File Size: 
Sampling Method: 2-cm contiguous composite samples
Investigator: Walter E. Dean, U.S. Geological Survey, Federal Center, Denver, CO 
80225

Data file contains results of geochemical analysis for various elements measured by inductively 
coupled plasma emission (ICP) spectroscopy.  Headers indicate percentages or concentrations 
parts per million (ppm) bulk dry weight of the various elements using standard chemical 
symbols.  

Diatom Data File

File Name: ofr5diat.wk1
File Size: 
Sampling Method: 1-cm contiguous composite samples
Investigator:J. Platt Bradbury, U.S. Geological Survey, Federal Center, Denver, CO 
80225

Data file contains relative concentration of diatoms in number of specimenns per millimeter of 
treansect across a microscope slide.  Abbreviations for taxa in column headers are explained in a 
file called "ofr5diatm.txt".  

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