Bog deposits in the Winsor Creek drainage basin, southern Sangre de Cristo Mountains, New Mexico contain a high-resolution record of Pleistocene to Holocene glacial activity. Sediment cores were recovered from an alpine bog (elevation 3,100 m) behind a Pinedale age moraine, 2 km from a high-elevation (-3600 m) cirque. Three cores reached glacial talus and consist of -6 meters of finely laminated to coarsely laminated lake clays, grading into gyttja. Superimposed on this long-term, lake-bog transition record are many distinct coarse-grained detrital packages punctuating times of rapid environmental change.
Accelerator mass spectrometry (AMS) carbon dating, sedimentology, variations in rock magnetic properties of the sediment, and organic carbon properties reveal six distinct periods of glacial/ periglacial activity often correlative with detrital sand deposition. These include a late Pleistocene Pinedale glacial termination (> 12,120 14C yr 14 B.P.), a Younger Dryas cirque glaciation (-10,100 C yr B.P.), an early Neoglacial periglacial event (-4,900 14C yr B.P.), a middle Neoglacial cirque glaciation (3,700 14C yr B.P.), and periglacial activity during late Neoglacial (2,800 14C yr B.P.) and Little Ice Age time (-120 14C yr B.P.). The age model from these cores indicates an increase in depositional rates immediately following glacial events, and a prolonged period of reduced deposition rates during the mid-Holocene warm period. Cold events documented in these cores correlate with times of reduced ice rafting events in the North Atlantic Ocean suggesting that these climatic changes were likely hemispheric in their extent.
The extreme southern position of this glaciated range and the absence of correlative glacial conditions in the more northerly, higher elevation, San Juan Mountains of Colorado suggest a climatic discontinuity exists. Modern differential effects of summertime land surface heating on atmospheric temperatures could explain this apparent paradox. A similar strong climatic gradient during the late Holocene would have led to contrasting climatic responses in the San Juan and the southern Sangre de Cristo Mountains. A summer temperature threshold is postulated to have existed between these two ranges, allowing small glaciers to grow on the periphery and not in the central part of the northern Colorado Plateau.
Earth and Planetary Sciences
Level of Degree
Department of Earth and Planetary Sciences
First Committee Member (Chair)
Peter J. Fawcett
Second Committee Member
John W. Geissman
Third Committee Member
Fourth Committee Member
Laura J. Crossey
Dept. of Earth and Planetary Sciences at UNM, New Mexico Geological Society, Colorado Scientific Society, grant from National Science Foundation to Dr. Fawcett
Armour, Jake. "A Late Pleistocene and Holocene High-Resolution Glacial and Paleoclimate Record from the Southern Sangre de Cristo Mountains, Northern New Mexico." (2002). https://digitalrepository.unm.edu/eps_etds/291