Paleomagnetic chronostratigraphy of Holocene Laguna Minucúa, Oaxaca, Mexico

Full-vector paleomagnetic secular variation (PSV) records have been recovered from two cores (MN1, MN2) collected from Laguna Minucúa, Oaxaca, Mexico. The sediments of Laguna Minucúa are laminated, probably varved, to within 15 cm of the sediment/water interface. They may become a key paleoclimate record for Southern Mexico. However, radiocarbon dating has been equivocal at estimating the age of the lake sediments (Goman et al., 2013). The PSV records from cores MN1 and MN2 are correlatable between them and have a distinctive pattern of variability that can be correlated to well-dated PSV records from the western USA. The PSV correlations establish that the longest core (MN2) extends back ∼4500 cal BP. Assuming the MN2 lamina are varves, their average thickness (1.2 mm) and core length provide an independent estimate of ∼4600 cal BP, not significantly different. One radiocarbon date with an age of 1120 ± 60 cal BP, occurs at a depth in core MN2 with an equivalent paleomagnetic age of 1140 ± 50 cal BP, again not significantly different. Therefore, our estimate is that the Laguna Minucúa sediments are varved and represent a remarkable, high-resolution repository of paleoclimate information for Southern Mexico for the last 4500 years.