OSL dating of a lacustrine to fluvial transitional sediment sequence in Valle Toledo, Valles caldera, New Mexico

Quaternary lacustrine deposits exist within several valleys in the Valles caldera in northcentral New Mexico . These deposits contain potentially valuable paleoclimatic records . We report OSL ages for a section of unconsolidated Quaternary sediments exposed in the southwest part of Valle Toledo within Valles caldera . The sequence represents the transition over time from lacustrine to fluvial deposition at the site . We present a stratigraphically coherent depositional chronology for the Valle Toledo section consistent with the available radiocarbon constraint based on analysis of bootstrapped dose distributions derived from data collected by IRSL MAAD procedures . The ages suggest the existence of a late Pleistocene lake in Valle Toledo from at least 48 .5 ka to ~44 ka, which is consider ably younger than age interpretations based on correlation to a >500 ka rhyolite dam across San Antonio Creek . This study helps to emphasize the need for additional research to decipher the geologic history of the intra-caldera lakes as well as to correlate the records of climate and environmental change among the lacustrine deposits within Valles caldera .