| OCR Text |
Show COLLEGE OF SOCIAL & BEHAVIORAL SCIENCE UNDERGRADUATE RESEARCH ABSTRACTS Vanessa Chavez Andrea Brunelle A -14,500 YEAR FIRE AND SEDIMENT HISTORY OF A DESERT WETLAND IN NEW MEXICO Vanessa Chavez (Andrea Brunelle) Department of Geography University of Utah Sediment samples from the archeological site at Boca Negra Wash, N e w Mexico were examined in order to construct a prehistoric fire history for the area. A -14,500 year fire record was reconstructed from sediments collected from trench 2 of this site using charcoal data and magnetic susceptibility. Radiocarbon dates in (Holliday et al. 2006) were available from depths below 43 c m from the surface and were used to construct an age model for the trench. Depths from a stratigraphic cross section in (Holliday et al. 2006) were used to create the lithostratigraphic column. This column illustrates the sediment type for different depths and ages of the trench, where older ages correspond with deeper depths. The magnetic susceptibility of sediment samples from this trench showed higher values in sandy layers, particularly where an unconformity was identified (fig 1).This observation is consistent with the higher magnetic readings associated with coarser grained, terrestrial deposits and serves as an indicator of aeolian activity and potentially high surface erosion. As a result of the unconformity, dates could not be modeled above 47 cm from the surface. Therefore, charcoal is represented as a concentration (particles/volume) for depths from 43 c m and as an accumulation rate (particles/cm2/yr) for depths from 47 c m from the surface. Findings from the fire reconstruction show that fire activity is insignificant until ~6900 years BP (fig. 1).This observation is consistent with data from multiple sites and is concurrent with the onset of the El Nino Southern Oscillation (ENSO), suggesting that ENSO plays s o m e part in controlling fire occurrence in desert wetlands (Brunelle et al., 2010). Information from Boca Negra Wash offers further insight in to understanding the relationship between fire and climate in desert environments and h o w these regimes m a y evolve with future climate change. Boca Negra Wash, N M References Brunelle, A., Minckley, T.A., Blissett, S., Cobabe, S.K., Guzman, B.L, 2010. A -8000 year fire history from an Arizona/ Sonora borderland cienega. Journal of Arid Environments 74475-481. Holliday, V, Huckell, B., Mayer, J.H., Forman, S.L., McFadden, L.D., 2006. Geoarcheology of the Boca Negra Wash area, Albuquerque basin, N e w Mexico, USA. Geoarcheology: An International Journal 21, 765-802. 90 |
