11 Future Voices in Geoscience- Undergraduate Research Posters

This session is for two-year college and four-year college and university students presenting research posters in any subdiscipline of geosciences. Posters and presentations will be judged for awards.

Monday, 18 May 2026
8:00 AM - 5:30 PM
Alvarado D/E

Using Physical Weathering of Quartz Grains to Identify Buried B Horizons in Hillslope Soils in the Sandia Mountains, New Mexico

Paper number: 11-10
Program: Technical Sessions
Time: 8:00 AM – 8:00 AM

Authors

Abstract

Hillslope colluvium in the foothills of the Sandia Mountains of New Mexico exhibit contrasting degrees of soil development. Most granitic slopes have pockets of colluvium with minimal soil development whereas granitic slopes with large occurrences of aplite dikes preserve thick well-developed soil profiles. The aplite dikes weather into blocky clasts that trap eolian sediment, an important flux into the hillslope soil system. The presence of buried B horizons, on aplite slopes, may indicate past climatic conditions that favored periods of enhanced colluviation. This study documents the physical weathering observed in quartz grains from aplite clasts buried in hillslope colluvium to determine if deeply buried clasts are more weathered. Clasts from B horizons were sampled from the backslope of a prominent aplite slope, at the depths: 0.4 m, 0.7 m and 1.1 m. One clast was sampled from the aplite dike at the top of the hillslope. Thin sections from clasts ranging from 5 to 20 cm were produced and photomicrographs of five representative quartz grains from each clast were used in this study.  Physical weathering is quantified by measuring crack length and crack area in large, 100 to 700 micron, quartz grains. The length and area of cracks were measured alongside total grain area using lines and polygons in ArcGIS Pro. Total crack length per grain area increased as soil depth increased. The average crack length to grain area ratio for the grains in the deepest and second deepest samples were 0.00953 µm-1 and 0.00673 µm-1, respectively. The average crack length to grain area ratio for grains in the uppermost clast (0.00228 µm-1), is very similar to that of those in the clast from the outcrop of the aplite dike ( 0.00220 µm-1). The degree of physical weathering in quartz grains suggests that aplite clasts buried more than 0.5 m have experienced more weathering and are likely from an older colluvial event. 

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

doi: 10.1130/abs/2026RM-410703

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