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80-9 Cosmogenic and Numerical Modelling Constraints for Costilla Massif, New Mexico in the Southernmost Rocky Mountains Suggest Cold Local Climate and Presence of Holocene Cirque Glaciation

Session: Recent Advances in Glacial Geology, Geomorphology, and Chronology

Presenting Author:

Anthony Feldman

Authors:

Feldman, Anthony David¹, Sion, Brad², Anderson, Leif Stefan³, Brugger, Keith A.⁴

(1) Division of Earth and Ecosystem Sciences, Desert Research Institute, Las Vegas, NV, USA, (2) Division of Earth and Ecosystem Sciences, Desert Research Institute, Bountiful, UT, USA, (3) Department of Geology and Geophysics, University of Utah, Department of Geology and Geophysics, Salt Lake City, UT, USA, (4) Department of Geology, University of Minnesota, Morris, Morris, MN, USA,

Abstract:

Constraints on the spatial extents and timing of ice cap and valley glacier fluctuations in the Southernmost Rocky Mountains remain limited. The lack of such chronologies restricts our understanding of late Quaternary paleoclimatic evolution. Here, we examine the timing of ice cap and valley glacier advance and retreat in Long Valley and at State Line Peak Cirque at Costilla Massif in northern New Mexico. We couple cosmogenic ¹⁰Be exposure age results from 10 quartz monzonite boulders with energy-mass balance modelling to examine paleoclimatic conditions at the Last Glacial Maximum (LGM). Sampled boulder exposure ages range from 179 ± 11 to 4.6 ± 0.3 ka. These ages include the first ¹⁰Be age constraints indicating the presence of MIS-6 and post-Holocene climate optimum Neoglacial aged moraines within the Sangre de Cristo Range. Numerical modelling using an updated version of the Plummer-Phillips combined energy-mass balance approach is consistent with the presence of an ice cap covering Costilla Massif and a temperature diversion of -10.5°C during the LGM. Comparing annual surface mass balance to elevation suggests climatic similarities during the LGM to modern glaciers in semi-arid conditions such as Tuyuksu glacier in Khazakhstan. Together, our cosmogenic and modelling results are consistent with colder local climatic conditions and longer lasting glacial presence within the southernmost Rocky Mountains than previous cosmogenic dating and modelling results.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-10570

Cosmogenic and Numerical Modelling Constraints for Costilla Massif, New Mexico in the Southernmost Rocky Mountains Suggest Cold Local Climate and Presence of Holocene Cirque Glaciation

Description

Session Format: Oral

Presentation Date: 10/20/2025

Presentation Start Time: 10:45 AM

Presentation Room: HBGCC, 213AB

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