Lake Malawi Biogenic Silica Data: Readme file
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              World Data Center for Paleoclimatology, Boulder
                                and 
                   NOAA Paleoclimatology Program
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NOTE: PLEASE CITE ORIGINAL REFERENCE WHEN USING THIS DATA!!!!!

NAME OF DATA SET: Lake Malawi Biogenic Silica Data
LAST UPDATE: 10/2003 (Extension of record length for cores M98-1PG and M98-2PG)  

CONTRIBUTOR: Thomas C. Johnson, Large Lakes Observatory,
University of Minnesota - Duluth.

IGBP PAGES/WDCA CONTRIBUTION SERIES NUMBER: 2001-017

SUGGESTED DATA CITATION: Johnson, T.C., et al., 2001,
Lake Malawi Biogenic Silica Data, IGBP PAGES/World Data Center 
for Paleoclimatology Data Contribution Series #2001-017.  
NOAA/NGDC Paleoclimatology Program, Boulder CO, USA. 

ORIGINAL REFERENCES:  Johnson, T.C., Barry, S.L., Chan, Y., and 
Wilkinson, P., 2001, Decadal record of climate variability 
spanning the last 700 years in the southern tropics of East Africa,
Geology, v. 29, No. 1, p. 83-86, January 2001.

DeMaster, D.J., 1979, The marine budgets of silica and Si32 [Ph.D.
Dissertation thesis], Yale University.

GEOGRAPHIC REGION: East Africa
PERIOD OF RECORD: 1454-1996 AD

FUNDING SOURCES:  U.S. National Science Foundation, Grant ATM-9709291. 

LIST OF FILES: 
Readme-Malawi.txt (this file), 
M93-1SB.xls, M93-2SB.xls, M98-10MC.xls, 
M98-11MC.xls, M98-1PG.xls, M98-2PG.xls,
(Microsoft Excel Format),
M93-1SB.txt, M93-2SB.txt, M98-10MC.txt, 
M98-11MC.txt, M98-1PG.txt, M98-2PG.txt 
(Tab-delimited ASCII format).

DESCRIPTION:  
The data are biogenic silica (as % SiO2) versus age from six cores 
in the north basin of Lake Malawi, at the southern end of the 
East African Rift Valley.  The chronology is based on a combination 
of varve counts and Pb-210 geochronology, all tied to stratigraphic 
correlations of certain marker beds that can be traced among the 
six cores.  Positions of the cores are based on GPS navigation.  
Biogenic silica analyses were done using the time series digestion 
technique of Demaster (DeMaster, 1979).  The precision is ±1% SiO2.  

Data is presented in columns for depth in core, % biogenic silica (Bsi), 
and year, based on varve counts and, in two cores, Pb-210 activity.  
Pb-210 analyses and age assignments were done by Dr. Paul Wilkinson, 
Dept. of Fisheries and Oceans, Winnipeg, using alpha spectrometry.

These data show strong evidence of this part of tropical Africa
responding to the Little Ice Age, and are presented in Johnson et al.,
2001.  Data were generated in the period from 1998 to 2000.

Note: The Pb-210 chronology for M98-10MC assumes the core top was 1998.  
However stratigraphic correlations with M98-11MC indicate that the core 
top is missing the top ca. 4 cm, or 18 years.  The correlation is in 
layer H1, situated at about 10 cm in 11 MC and at 7.5 cm in 10 MC.