Equatorial East African Rainfall and Drought Data: Readme file --------------------------------------------------------------------- NOAA Paleoclimatology Program and World Data Center A - for Paleoclimatology --------------------------------------------------------------------- NOTE: PLEASE CITE ORIGINAL REFERENCE WHEN USING THIS DATA!!!!! NAME OF DATA SET: Equatorial East African Rainfall and Drought Data LAST UPDATE: 1/2000 (Original Receipt by WDCA Paleo) CONTRIBUTORS: Dirk Verschuren, Kathleen R. Laird, and Brian F. Cumming IGBP PAGES/WDCA CONTRIBUTION SERIES NUMBER: 2000-010 SUGGESTED DATA CITATION: Verschuren, D., Laird, K.R., and Cumming B.F., 2000, Equatorial East African Rainfall and Drought Data, IGBP PAGES/World Data Center A for Paleoclimatology Data Contribution Series #2000-010. NOAA/NGDC Paleoclimatology Program, Boulder CO, USA. ORIGINAL REFERENCE: Verschuren, D., K. R. Laird, and B. F. Cumming, 2000, Rainfall and drought in equatorial east Africa during the past 1,100 years. Nature, No.6768, v403, pp410-414, January 27, 2000. METHOD REFERENCES: Line, J. M., C. J. F. ter Braak, and , H. J. B. Birks, 1994, WACALIB version 3.3: A computer program to reconstruct environmental variables from fossil assemblages by weighted averaging and to derive sample-specific errors of prediction. J. Paleolimnol. 10, 147-152. Gasse, F., S. Juggins, and L. Ben Khelifa, 1995, Diatom-based transfer functions for inferring hydrochemical characteristics of African paleolakes. Palaeogeogr., Palaeoclimatol., Palaeoecol. 117, 31–54. Verschuren, D., 1997. Taxonomy and ecology of fossil Chironomidae (Insecta, Diptera) from Rift Valley lakes in central Kenya. Arch. Hydrobiol. Suppl. 107, 467–512. Verschuren, D., 2000. Reconstructing East African lake-level fluctuations during the past 1800 years from sediment stratigraphy in a submerged crater basin. J. Paleolimnol. (in press). FUNDING SOURCE: US National Science Foundation DEB 93-20324, ATM 95-31222 GEOGRAPHIC REGION: Equatorial East Africa PERIOD OF RECORD: AD 880-1993 LIST OF FILES: Readme.verschuren2000.txt (this file), naivasha.chironomidsalinity.xls, naivasha.diatomsalinity.xls, naivasha.lakelevel.xls (Microsoft Excel format), naivasha.chironomidsalinity.txt, naivasha.diatomsalinity.txt, naivasha.lakelevel.txt (tab-delimited ASCII format). DESCRIPTION: Equatorial East African Rainfall and Drought Data Crescent Island Crater, Lake Naivasha, Eastern Rift Valley, Kenya LATITUDE/LONGITUDE: 00 45.81' S, 36 24.48' E BATHYMETRY/ELEVATION: 1.95 km2, 15.35 meter water depth (08/1993), 1885 m a.s.l. Crescent Island Crater is a partially submerged crater basin in Lake Naivasha, which itself is only 6 meter deep (08/1993), has an open-water surface area of ~135 km, and drains 2,378 km2 of the dry Rift Valley floor and moist adjacent highlands. CHRONOSTRATIGRAPHY: Sediment age at depth (~AD 880 to 1993) is based on linear interpolation between 15 dated horizons including the sediment surface, fossil evidence of three documented outbreaks of an exotic water fern, three stratigraphic markers correlated to equivalent horizons in a Pb-210 dated sediment core, and eight AMS C-14 dates on terrestrial plant macrofossils. Radiocarbon dates were converted to calender years using the bidecadal calibration curve of Stuiver and Reimer (1993: Extended C-14 data base and revised CALIB 3.0 C-14 age calibration program, Radiocarbon 35, 215–230). When conversion yielded non-unique calendar ages, a 4th-order polynomial regression of the 15 dated horizons was used to determine the relative probability of alternative calender ages. Three additional, out-of-sequence C-14 dates recovered from carbonate muds between 506 and 572 cm core depth were omitted from the chronology on the basis that they may be derived from older deposits reworked during lake lowstands. Files naivasha.diatomsalinity.xls and naivasha.diatomsalinity.txt. Lake Naivasha, Crescent Island Crater diatom-inferred salinity VARIABLE NAMES AND UNITS: depth in core (cm); sediment age (yr AD); conductivity (mS/cm) DESCRIPTION OF DATA: variations in lake-water salinity (conductivity, in mS/cm) inferred from percent abundance of fossil diatom taxa in 151 horizons at 4-cm core intervals; nine data points corresponding with diatom-mat lithology were omitted from the final data series. Files naivasha.chironomidsalinity.xls and naivasha.chironomidsalinity.txt. Lake Naivasha, Crescent Island Crater chironomid-inferred salinity VARIABLE NAMES AND UNITS: depth in core (cm); sediment age (yr AD); conductivity (mS/cm) DESCRIPTION OF DATA: variations in lake-water salinity (conductivity, in mS/cm) inferred from percent abundance of fossil chironomid taxa in 151 horizons at 4-cm depth intervals; two intervals contained insufficient core material for chironomid analysis. Files naivasha.lakelevel.xls and naivasha.lakelevel.txt. Lake Naivasha, Crescent Island Crater lake-level fluctuations VARIABLE NAMES AND UNITS: core depth (cm); time (year AD); lake depth (m) DATA PRECISION: a) historical lake-level record (AD 1883-1993): better than 0.5 m; b) reconstructed lake-level record (~ AD 880-1883): reported values are semi-quantitative, based partly on historical calibration of the composition of profundal sediments and partly on arguments following from site-specific hydrology and physical limnology; see Method Reference DESCRIPTION OF DATA: variations in the water depth (m) of Crescent Island Crater, Lake Naivasha derived from staff gauge readings of lake-surface elevation (AD 1883-1993) or reconstructed from sedimentological characteristics of profundal sediments (~AD 880-1883)