Soil-Geomorphology and the Reconstruction of Landscapes of the Past

Utilizing a fundamentally uniformitarian approach, geoscientists have long used modern soils to understand buried soils (or “paleosols”) and to reconstruct the past, much as modern species of plants and animals are used in paleontology and paleobotany. Biologists realized, however, that one-to-one comparisons are overly simplistic and, for plants and animals that evolved over deep time, inadequate. Accordingly, they applied broader perspectives with an ever increasing understanding of biological processes. Soil-geomorphology can also be utilized to better understand the applications and limitations of using gross morphological characteristics of modern soils as keys to reconstructing past landscapes. For example, increased understanding of stable-C and -O composition of pedogenic carbonate in modern soils is being used to infer the composition of and changes in past biotic communities and the Earth's atmosphere as well as estimates of paleotemperature and paleoaltitudes. A variety of processes (erosion, compaction, post-burial alterations) are also well known for hindering or complicating an accurate interpretation of buried soils. An underappreciated aspect of soil genesis prior to burial that may hamper reconstruction of buried soils and landscapes is equifinality, the development of similar pedologic features by multiple possible pathways. Recent soil-geomorphic research combined with other research illustrates how some features of contemporary soils reflect equifinality. For example, argillic horizons form under a wide variety of environments. Infiltration of dust is a particularly important component of pedogenic equifinality as illustrated in the upbuilding of cumulic A horizons, rates of clay accumulation in argillic horizons, rates and magnitude of carbonate accumulation in calcic horizons, and depth to calcic horizons.