Uncovering a landscape buried by the super-eruption of Toba, 74,000 years ago: A multi-proxy environmental reconstruction of landscape heterogeneity in the Jurreru Valley, south India

The Youngest Toba Tuff (YTT) eruption similar to 74 ka is the largest volcanic event to occur during the last two million years. This paper presents a high resolution landscape reconstruction for the Jurreru Valley, south India, immediately prior to this eruption. Primary ash fall deposits have sealed the pre-Toba surface of the Jurreru Valley, and subsequent deposition of remobilised ash has helped preserve this horizon. These primary YTT deposits provide an isochron that allows for the study of palaeoenvironmental conditions across a 25,000 m(2) area in the Jurreru Valley, permitting the reconstruction of the pre-Toba landscape. Sixty sites with exposed primary ash deposits have been recorded as part of a Total Station survey, twelve of which have been subject to detailed stratigraphical study. This has enabled a reconstruction of the topography of the buried surface in the Jurreru Valley. Stable isotope and phytolith analyses are used to explore diversity across this buried landscape, indicating that the ratio of C-3 to C-4 plants varies with regard to changes in topographic height in the landscape of up to similar to 5 m. High levels of spatial heterogeneity within these proxy data are indicated by this study, highlighting the risks of extrapolating regional palaeoenvironmental sequences from vertically sampled sedimentary sections, which may well reflect highly localised influences of topography and geomorphology. (C) 2011 Elsevier Ltd and INQUA. All rights reserved.