New age controls on the tephrochronology of the southernmost Andean Southern Volcanic Zone, Chile

The chronology of over 50 tephra layers preserved in a lake sediment core from Laguna La Trapananda (LLT) in the southern portion of the Andean Southern Volcanic Zone (SSVZ), Chile, is constrained by new radiocarbon age determinations, which span the period from late Pleistocene glacial retreat to the late Holocene. The tephra are correlative with tephra previously described from other lake cores in the region and are attributed to explosive eruptions of the SSVZ volcanoes Mentolat, Hudson, Macá, and potentially Cay. The new age determinations are used to estimate the ages of the >50 tephra in the LLT core, as well as those from the other previously described lake cores in the area, by a Bayesian statistical method. The results constrain the frequency of explosive eruptions of the volcanic centers in the southernmost SSVZ. They indicate that there was essentially no increase in the rate of eruptions from late-glacial to recent times due to deglaciation. They also provide isochrones used to constrain the depositional histories of the small lacustrine systems within which they were deposited and they provide a tephrochronologic tool for other paleoclimatic, paleoecologic, archaeologic and tephrochronologic studies in central Patagonia.