GSA QUATERNARY GEOLOGY AND GEOMORPHOLOGY DIVISION KIRK BRYAN AWARD: SOIL GEOMORPHOLOGICAL RESEARCH IN ARIDLANDS: THERE MIGHT BE A LITTLE DUST ON THE BOTTLE—IT’S ONE OF THOSE THINGS THAT GETS SWEETER WITH TIME

Mineralogic, chemical and numerical model-based studies of aridland soils have substantially increased the understanding of their formation. Supplemented by ecologic, geochronologic, paleoclimatologic and isotopic studies, soil geomorphological research provides important insights into the evolution of the associated, sparsely vegetated landscapes. The groundbreaking research of Leland Gile, Dan Yaalon and their colleagues showed that aridland soils do not form mainly via processes largely dominated by chemical weathering in soil moisture regime characterized by shallow leaching. Their strongly interdisciplinary research showed that the main source of calcium carbonate and silicate clay in aridland soil B horizons is dust. Studies of soils and desert pavements atop volcanic flows in the Cima volcanic field additionally showed that dust entrapment and translocation below surface clasts can also drive accretionary and inflation soil profile development (AIP) below a rising desert pavement. Contrasting markedly with the canonical A/B/C Dokuchaev profile, AIP is favored beneath pavements on stable geomorphic surfaces in aridlands. In environments where pavements cannot form, dust entrapping plants and increased plant density may also favor AIP. Hillslopes in aridlands are geomorphically less stable landforms, but they are excellent dust traps, and in favorable circumstances, AIP promotes the development of continuous, smooth soil and vegetated mantles of transport-limited hillslopes. Variation in rocktype and aspect (topoclimate), however, can strongly impact the spatial distribution and morphology of soils on aridland hillslopes, causing shifts in hillslope vegetation, runoff and erosion, changes that may culminate in the transformation of smooth hillslopes to steep detachment limited hillslopes. Soil geomorphologic research, and the conceptual framework provided by Jenny’s nearly century old, famous CLORPT equation, have provided fundamental contributions to soil landscape evolution; but the essential prerequisite of all research involving soil studies is the detailed description of soil morphology, descriptions that must reflect, or capture, subtle variations in parent material, the presence of buried soils, bioturbation and other processes that affect soil character.