Fawcett 1 Two Middle Pleistocene Glacial-Interglacial Cycles from the Valle Grande, Jemez Mountains, northern New Mexico

• Main Authors: Peter J. Fawcett Jeff Heikoop, John W. Geissman, Giday Woldegabriel, Craig D. Allen, Catrina M. Johnson, Susan J, Julianna Fessenden-rahn
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Antarctic; Valles; Antarc*; ice core
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.544.4682; http://www2.nau.edu/envsci/faculty/ScottAnderson/docs/106_NMGS manuscript 2007.pdf

A long-lived middle Pleistocene lake formed in the Valle Grande, a large moat valley of the Valles Caldera in northern New Mexico, when a post-caldera eruption (South Mountain rhyolite) dammed the drainage out of the caldera. The deposits of this lake were cored in May 2004 (GLAD5 project, hole VC-3) and 81 m of mostly lacustrine silty mud were recovered. A tentative chronology has been established for VC-3 with a basal tephra Ar-Ar date of 552 +/- 3 kyr, a correlation of major climatic changes in the core with other long Pleistocene records (deep sea oxygen isotope records and long Antarctic ice core records), and the recognition of two Fawcett 2 geomagnetic field polarity events in the core which can be correlated with globally recognized events. This record spans a critical interval of the middle Pleistocene from MIS 14 (552 kyr B.P.) to MIS 10 (~360 kyr B.P.), at which time the lacustrine sediments filled the available accommodation space in the caldera moat. Multiple analyses, including core sedimentology and stratigraphy, sediment density and rock magnetic properties, organic carbon content and carbon isotope ratios, C/N ratios, and pollen content reveal two glacial/interglacial cycles in the core