RECONSTRUCTING FIRE USING MACROSCOPIC CHARCOAL ABUNDANCES IN PLIOCENE FLUVIOLACUSTRINE SEDIMENTS IN THE TERUEL BASIN, SPAIN

Mediterranean-type climates (MTCs) have long been of interest to scientists due to high biodiversity and unusual precipitation regime. MTCs are unique in that precipitation mostly occurs during the winter (in some locations spring and fall months) and the summers are typically dry. On the Iberian Peninsula the MTC may have developed during the Pliocene when pollen records showed a gradual shift from mostly subtropical vegetation to dominance of drought tolerant taxa during global cooling. Projected future climate changes pose a risk as winter climatic shift from subtropical to MTCs can give us more insight into the future climate and ecosystems of the Mediterranean Basin.

Paleoclimate studies can provide insight into how global warming might affect the Iberian climate. Charcoal records can be useful indicators of fire regimes along with pollen and hydroclimate proxies might help us understand climate-ecosystem relationships. Here we present charcoal abundances over the Mid-Pliocene -Early Pleistocene period in samples of fluvial and lacustrine sediments retrieved from the Villabla Alta section, Teruel Basin, in the Iberian Peninsula. We found that there is a gradual increase in the charcoal count leading up to the M2 glaciation 3.3 million years ago which suggests increasing fire activity during this time. As a result, we hypothesize that an increase in charcoal counts coinciding with global cooling could indicate decreased summer rainfall, consistent with long-term vegetation change and our own unpublished paleosol carbonate oxygen isotope data. It is also possible that global cooling resulted in an increase in Iberian winter rainfall, denser vegetation, more fuel, and thus greater fire activity, but it is not clear that woody vegetation density was winter rainfall-limited at this time. Therefore, we favor the interpretation that intensified summer drought increased east-central Iberian fire activity during Pliocene global cooling at approximately the same time that drought-tolerant vegetation was gradually replacing subtropical ecosystems.