NOAA/WDS Paleoclimatology - Yok Balum Cave, Belize 2000 Year Stalagmite Stable Isotope Data

STUDY NOTES: The YOK-I stalagmite was collected in June 2006 approximately 50 m from the eastern cave entrance. Carbonate was actively precipitating on the tip of this 606.9-mm-long stalagmite when it was harvested. Forty 230Th dates constrain the age of incremental growth in the upper 444.3 mm of YOK-I (Table S2). XRD analysis indicates that the carbonate in the upper 415 mm is pure aragonite and not affected by secondary alteration. The stable isotope climate record presented here therefore comes from the upper 415 mm, while the lower stalagmite section is less suitable for stable isotope studies and was not included in this investigation. Over 4,200 d18O and d13C measurements were performed on the upper 415 mm of the YOK-I stalagmite dated between 40 BC and AD 2006. These samples were continuously milled at 0.1 mm increments and, depending on growth rate changes in YOK-I, the temporal resolution of the isotopic data fluctuates from 0.01 and 3.68 yrs/0.1 mm with an average resolution of 0.49 yrs/0.1 mm. The available data indicate that fluctuations in rainfall intensity are reflected in the d18O record.
ABSTRACT SUPPLIED BY ORIGINATOR: The role of climate change in the development and demise of Classic Maya civilization (300 to 1000 C.E.) remains controversial because of the absence of well-dated climate and archaeological sequences. We present a precisely dated subannual climate record for the past 2000 years from Yok Balum Cave, Belize. From comparison of this record with historical events compiled from well-dated stone monuments, we propose that anomalously high rainfall favored unprecedented population expansion and the proliferation of political centers between 440 and 660 C.E. This was followed by a drying trend between 660 and 1000 C.E. that triggered the balkanization of polities, increased warfare, and the asynchronous disintegration of polities, followed by population collapse in the context of an extended drought between 1020 and 1100 C.E.