STABLE OXYGEN ISOTOPE ANALYSIS OF THE FRESHWATER GASTROPOD PACHYCHILUS SPP. AND ITS POTENTIAL USE FOR SEASONALITY STUDIES AT THE LOWLAND MAYA SITE OF PACBITUN, BELIZE
In the Maya lowlands, seasonal climate variation is principally expressed as cycles in rainfall, as opposed to air temperature, with pronounced rainy and dry seasons present. However, water temperature data collected from Roaring Creek and Barton Creek in the Cayo District of Belize, have revealed that there is, to a lesser extent, some seasonal water temperature variation that coincides with seasonal creek water δ18O variation observed in water samples collected on a bi-weekly basis from October 2010 to October 2011 in Roaring Creek. Creek water δ18O appears to reflect meteorological activity in the area, although the amplitude of this variation is less than that of the annual meteorological δ18O variation obtained from modeled IAEA data. This “flattening” of creek water δ18O seasonal variation may be a consequence of surface and groundwater mixing in the karstic landscape of western central Belize. Therefore, δ18O variation observed in the carbonate of jute shells may reflect both seasonal temperature variability and seasonal fluctuations in stream water δ18O.
Analysis of shell carbonate oxygen isotope variation has revealed strong sinusoidal δ18O variation in specimens collected live from the Cayo District of Belize. Currently, work is being conducted in order to compare shell carbonate oxygen isotope variation with stream water δ18O and temperature variation. In addition to the study of modern jute and their aqueous environments, a seasonality study of Middle Preclassic jute from Plaza B in the site core of Pacbitun will also be discussed.