Abstract Title

The Geomorphology of the Ten Mile Terrace, Boise, Idaho

Additional Funding Sources

This project is supported by the National Institute of General Medical Sciences of the National Institutes of Health under Award No. R25GM123927.

Abstract

Our project objective is to reconstruct the geomorphology of the Ten Mile Terrace. The Ten Mile Terrace (1.7 Ma) is the oldest of the nine Boise River terraces. Located in the northwest corner of the Western Snake River Plain and between the Snake River on the south and the Boise River on the north. This poster presents the initial observations and interpretations of analyses performed on a 30-meter exposure of the Ten Mile Terrace. Based on high-resolution surface-from-motion drone imagery and samples collected along two transects of the 30-meter exposure, we identify six depositional units where sediments cycle through a fining upward sequence. The methodology include hand textures of soils, soil particle distribution based on percent by sample weight for sand, silt, and clay, geochemical analyses using pXRF (portable x-ray fluorescence) and XRD (x-ray diffraction), and measuring cobble sizes and using Stoke’s settling rate to determine deposition distance. The composition of the sediment clasts and absence of basaltic materials suggest the sediments are composed of recycled material sourced from the Atlanta lobe of the Idaho Batholith that underlies the Boise River basin. Work remaining on this study includes dating of the six depositional units and the sampling and geochemical analyses of the alluvial fans and deposits on the north side of the Boise River Valley to compare with the Ten Mile Terrace sediments. Additionally, we plan to collect thermosimagery of the 30-meter exposure to determine if stratigraphic sequences can be discerned using remote thermal techniques.

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The Geomorphology of the Ten Mile Terrace, Boise, Idaho

Our project objective is to reconstruct the geomorphology of the Ten Mile Terrace. The Ten Mile Terrace (1.7 Ma) is the oldest of the nine Boise River terraces. Located in the northwest corner of the Western Snake River Plain and between the Snake River on the south and the Boise River on the north. This poster presents the initial observations and interpretations of analyses performed on a 30-meter exposure of the Ten Mile Terrace. Based on high-resolution surface-from-motion drone imagery and samples collected along two transects of the 30-meter exposure, we identify six depositional units where sediments cycle through a fining upward sequence. The methodology include hand textures of soils, soil particle distribution based on percent by sample weight for sand, silt, and clay, geochemical analyses using pXRF (portable x-ray fluorescence) and XRD (x-ray diffraction), and measuring cobble sizes and using Stoke’s settling rate to determine deposition distance. The composition of the sediment clasts and absence of basaltic materials suggest the sediments are composed of recycled material sourced from the Atlanta lobe of the Idaho Batholith that underlies the Boise River basin. Work remaining on this study includes dating of the six depositional units and the sampling and geochemical analyses of the alluvial fans and deposits on the north side of the Boise River Valley to compare with the Ten Mile Terrace sediments. Additionally, we plan to collect thermosimagery of the 30-meter exposure to determine if stratigraphic sequences can be discerned using remote thermal techniques.