Southeastern Section - 62nd Annual Meeting (20-21 March 2013)

Paper No. 2
Presentation Time: 8:00 AM-5:30 PM


MILLER, Thomas E.1, WINTER, Amos2, BURNETT, Allison3, KELLY, Megan3 and BREITENBACH, Sebastian4, (1)Department of Geology, University of Puerto Rico, Mayaguez, PR 00681, (2)Department of Marine Sciences, University of Puerto Rico, Mayagüez, Mayagüez, PR 00681, (3)Department of Earth Sciences, University of Minnesota, Minneapolis, MN 55455, (4)Climate Geology, ETHZ Geologisches Institut, NO G 55 Sonneggstrasse 5, Zurich, ch-8092, Switzerland,

The Maya Mountains of Belize/Guatemala are located at an uncommonly active center of speleothem collection for paleoclimate. In a narrow, N/S 100 km traverse, six stalagmites from four caves have been dated and analyzed for 18O and 13C isotopes. These range from modern to almost 13 kyBP (five overlapping to some extent in age), growing in caves developed in the Cretaceous Campur Formation limestones, and offer an opportunity to compare isotope values from different caves in close proximity, as well as between stalagmites in the same cave.

The center of the traverse is the Xibalba cavern (400am asl), where the GUXI-1 speleothem was collected in 2007. It has produced a continuous record of the past 1000 years, showing four rainfall regimes (assuming δ18O as a rainfall proxy, influenced by the amount effect of the tropics) of increasing precipitation to ~1450 when an intense drought occurred until ~1650, followed by recovery to a wetter climate, then a gradual decline in the recent 200 years.

Macal Chasm is 25 km north at 520 m asl, with similar mean rainfall of ~155 cm/y. It also shows increasing rainfall after 1000 AD, and recent historical declines, but the severe drought of the Little Ice Age [LIA] is almost absent. The other two caves at either end of the traverse are located in much wetter environments (250-300 cm/y), located on the windward/Caribbean side of the mountains: the southernmost is Yok Balum at 340 m which shows the post-1000 AD rain increase, and the severe drought of the LIA, but the dry interval starts almost a century prior to that of Xibalba. Historical rainfall has also been declining. The records of ATM at the north do not overlap well with each other in time, and are short.

No clear pattern is shown by the δ18O of the caves in terms of either altitude/temperature or annual rainfall: The Xibalba values range from -4 ‰ to -2.75‰ VPDB, and that of Macal Chasm -5 to-4‰. The lower and wetter Yok Balum and ATM are -4 to -3‰ and -5 to-3‰ respectively.