OSL DATING OF LACUSTRINE DEPOSITION IN VALLE TOLEDO; NEW MEXICO

The Jemez Mountains of north central New Mexico are the relic of a volcanic system that catastrophically erupted ~1.2 million years ago. Following the eruption the volcano collapsed forming the Valles caldera. Over time several lakes have formed within and drained from the caldera, including Valle Toledo. The volcanic geology of the Jemez Mountains has been studied extensively, however, the evolution of its lakes is only partially known. The timing of lake initiation can generally be determined by the relations of lake deposits to dated volcanic eruptions, but the duration of the lakes is poorly constrained. The lacustrine sediments deposited within the caldera have been identified as potentially containing significant climate records for the southwestern United States. Determining the chronology of these lakes, including their longevity, will be important to unraveling the climatic history.

The primary objective of this research is to establish a geochronology for one of the transient lakes, Valle Toledo, in the northern moat of the caldera. Exposed sediments record the transition from lacustrine to fluvial environments as the eastern part of an extensive lake filled with sediment. This study will present OSL dating results obtained from four samples of lacustrine and fluvial sediment collected from a 7 meter stratigraphic section. It will also help demonstrate the potential of OSL dating to provide a meaningful geochronology for lacustrine deposition within the caldera.