T221 Sedimentary Archives of Mountain Building from the Fault-Scarp to the Range-Front: Interpreting Colluvial Wedge and Alluvial Fan Systems

Wednesday, 18 October 2023
8:00 AM - 12:00 PM
321

USING LUMINESCENCE DATING, COSMOGENIC DATING, AND SOIL STRATIGRAPHY TO PROVIDE CONTEXT FOR PALEOCLIMATE ARCHIVES FROM LAMINATED PEDOGENIC CARBONATE RINDS, CAPITOL REEF NATIONAL PARK REGION, UTAH (USA)

Paper number: T221-5
Program: Technical Sessions
Time: 9:00 AM – 9:15 AM

Authors

Abstract

Southern Utah (USA) contains numerous Quaternary terraces (e.g., debris flows, strath terraces) containing laminated pedogenic carbonate rinds. Recent work has shown that these rinds can be used as a paleoclimate archive via their carbon and oxygen isotope composition. However, the context in which these rinds developed is critical for record interpretation. To provide context we use a multi-disciplinary approach to investigate landscape evolution in southern Utah and assess (1) variability in local and regional terrace histories and (2) how landscape evolution may have influenced rind formation.

We excavated four pits on New Home Bench and Notom Bench, from which we are developing rind records. Both surfaces are diamicts modified by eolian input and accumulation of calcite and gypsum. The surface horizons (≈0 to 50 cm) are dominated by fine sand, silt, and little carbonate accumulation (≤ Stage I) which, based on luminescence dating, accumulated between 2.5–8.5 ka. The next horizons (≈50 to 90 cm) have more gravel (25 to 50%) and carbonate accumulation (Stage II+) accumulated over 9–23 ka. The lack of gravel in surface horizons is consistent with soil inflation by dust. These eolian ages match those of Canyonlands, Mesa Verde, and Black Mesa, supporting the established regional framework.

Below 90 cm, soil horizons have pervasive carbonate accumulation (Stages III to IV) before returning to relatively lower carbonate accumulation (Stage II; below about 170 to 200 cm). The primary calcium source for pedogenic carbonate is likely dust. Importantly, demonstrate that significant carbonate accumulation took place over 10s–100s ka, supporting prior regional inferences based on soil stratigraphy and cosmogenic dating (McFadden, 2013, Marchetti et al., 2005; Huth et al., 2019). Our minimal basal ages support laminated rind records covering 100s ka in common Quaternary environments. In turn, the youngest ages suggest a persistent source of calcium dust for rind formation. We conclude that rind records covering 10–100s ka should be common and will therefore provide new opportunities for inter-archive comparison.

Geological Society of America Abstracts with Programs. Vol. 55, No. 6

doi: 10.1130/abs/2023AM-394180

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