USING CRYPTOTEPHRA TO IMPROVE AGE MODELS OF SEDIMENTARY RECORDS: GEOCHEMICALLY FINGERPRINTING LAKE MALAWI TEPHRA
Cryptotephra from the Lake Malawi cores were recovered using an HCl wash, sieves, and a series of density separation. Electron microprobe analysis with wavelength-dispersive spectrometry (EMPA-WDS) was used to geochemically fingerprint tephra. Of the three cryptotephra layers found from hole 1C, one layer was geochemically fingerprinted as tephra from the Youngest Toba Tuff (YTT) eruption (75 ka, Toba caldera, Indonesia), a source ~7,300 km from hole 1C. The discovery of the YTT ash in Africa extends the known distal extent of ash from the Toba supereruption from ~4,300 km to ~7,300 km, and demonstrates the feasibility of finding cryptotephra beyond the known distal extent of eruptions to improve age models in sedimentary records.