3 Paleo-climate and -ecosystems of the Southwest and High Plains: From the Paleozoic to the Quaternary

Many Phanerozoic climates and ecosystems serve as potential analogues for the future; others highlight the Earth system response to tectonic and climatic forcings. We invite abstracts that probe the paleoclimate/ecosystems of the US Southwest

Monday, 18 May 2026
9:00 AM - 12:00 PM
Alvarado C

A Million-Year Long Record of Climate and Environmental Change from Central Arizona: The Stoneman Lake Project

Paper number: 3-4
Program: Technical Sessions
Time: 10:20 AM – 10:40 AM

Authors

Abstract

The Stoneman Lake Arizona Drilling Project (STL) recovered two deep lacustrine sediment cores (80m in composite) that provides a long paleoclimatic and paleoenvironmental record for the southern rim of the Colorado Plateau for the last million years. The record is uniquely suited for reconstructing the nature of over 20 glacial-interglacial cycles in the American Southwest including the terrestrial hydrologic and ecosystem responses to the mid-Pleistocene transition. A Bayesian age model for the core is derived from 15 radiocarbon dates and tephrochonology of ashes from the Yellowstone (Lava Creek B) and Long Valley, California (Bishop Tuff) calderas. Middle to late Pleistocene glacial maxima are correlated with deep lake facies containing well-preserved bedding, boreal pollen taxa (e.g. Picea) and lower bulk density and magnetic susceptibilities (MS). Interglacial periods are associated with shallower water deposits containing banded to massive siliciclastic sediment, the alga Phacotus, authigenic calcite and higher density and MS values. Prior to the mid-Pleistocene (MPT) transition, smaller amplitude changes in the lake environment with a lack of deep water facies suggest milder and drier glacial conditions compared to those of the post-MPT interval. The STL record suggests that southwestern North America saw a significant intensification of glacial conditions (colder and wetter) following the MPT. A detailed pollen analysis correlated with sedimentary facies analysis shows significant climate and ecosystem variability between glacial and interglacial periods and also shows significant variability within post-MPT glacial periods and post-MPT interglacial periods. Glacial periods are characterized by higher percentages of arboreal pollen and interglacials by higher percentages of non-arboreal pollen and more abundant charcoal, however, the individual taxa that make up these sums vary from glacial (interglacial) stage to glacial (interglacial) stage. This variability is likely due to a combination of different climatic forcing factors (local insolation variability, atmospheric CO2) and antecedent plant community conditions.

Geological Society of America Abstracts with Programs. Vol. 58, No. 4

doi: 10.1130/abs/2026RM-410704

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