Jeff Heikoop Fraser Goff R. Scott Anderson L. Donohoo-Hurley John William Geissman Giday WoldeGabriel Craig D. Allen Catrina M. Johnson Susan J. Smith Julianna Fessenden-Rahn Barry S. Kues Shari A. Kelley Virgil W. Lueth Peter J. Fawcett 2007 <div>A long-lived middle Pleistocene lake formed in the Valle Grande, a large moat valley of the Valles caldera in</div><div>northern New Mexico, when a post-caldera eruption (South Mountain rhyolite) dammed the drainage out of the caldera. The</div><div>deposits of this lake were cored in May 2004 (GLAD5 project, hole VC-3) and 81 m of mostly lacustrine silty mud were</div><div>recovered. A tentative chronology has been established for VC-3 with a basal tephra Ar-Ar date of 552 +/- 3 ka, a correlation</div><div>of major climatic changes in the core with other long Pleistocene records (deep sea oxygen isotope records and long Antarctic</div><div>ice core records), and the recognition of two geomagnetic field polarity events in the core which can be correlated with globally</div><div>recognized events. This record spans a critical interval of the middle Pleistocene from MIS 14 (552 ka) to MIS 10 (~360 ka), at</div><div>which time the lacustrine sediments filled the available accommodation space in the caldera moat. Multiple analyses, including</div><div>core sedimentology and stratigraphy, sediment density and rock magnetic properties, organic carbon content and carbon isotope</div><div>ratios, C/N ratios, and pollen content reveal two glacial/interglacial cycles in the core (MIS 14 to MIS 10). This record includes</div><div>glacial terminations V and VI and complete sections spanning interglacials MIS 13 and MIS 11. In the VC-3 record, both of</div><div>these interglacials are relatively long compared with the intervening glacials (MIS 14 and MIS 12), and interglacial MIS 13 is</div><div>significantly muted in amplitude compared with MIS 11. These features are similar to several other mid-Pleistocene records.</div><div>The glacial terminations are quite abrupt in this record with notable changes in sedimentation, organic carbon content, C/N</div><div>ratios and watershed vegetation type. Termination V is the largest climate change evident in this part of the middle Pleistocene.</div><div>The glacial inceptions tend to be more gradual, on the order of a few thousand years.</div> application/pdf en New Mexico Geological Society Two middle Pleistocene glacial-interglacial cycles from the Valle Grande, Jemez Mountains, northern New Mexico text