Sponsored by the Geomorphology Specialty Group
Association of American Geographers 102nd Annual Meeting
Chicago, Illinois, March 7-11.
Soil Geography and Geomorphology I: Geomorphic applications
Paper Session 3416
Thursday, 3/9/06, from 1:00 PM - 2:40 PM
Geomorphology Specialty Group
Randy Schaetzl - Michigan State University
Randy Schaetzl - Michigan State University
1:00 PM Author(s):
*Donald L. Johnson, Prof. Emeritus - University of Illinois
Diana N. Johnson, Geoscience consultant - University of Illinois
Abstract Title: Healing the Wounds of Occam’s Razor: A Process-Biodynamic Way Forward in Pedology and Soil- Geomorphology
An inscription in the National Academy of Sciences in Washington D.C. reads: “To science, pilot of industry, conqueror of disease, multiplier of the harvest, explorer of the universe, revealer of nature’s laws, eternal guide to truth.” How might this statement apply to soil studies? Soil studies constitute two over-lapping domains: a broad soil science - a ‘pilot of industry’ and ‘multiplier of the harvest’, and a narrower pedology - more a ‘revealer of nature’s laws’ and ‘guide to truth’. Pedology treats the nature and genesis of soil, whereas soil science encompasses soil mapping and classification, agrology, agronomy (applications of soil-crop sciences to management-crop production), agrobiology, agrochemistry, plant-crop genetics, land valuations, extension-outreach, agricultural engineering, etc. Pedology is more narrowly pure science oriented, soil science more broadly utilitarian. Theory-wise, pedology has long languished under a soil science utilitarian-conceptual device — the five factors (‘clorpt’) approach to map, classify, valuate, and “explain” soils. While it has greatly aided soil science, this device — supremely attractive in parsimonious plan — has wounded pedology because its genetic-interpretive domain is limited by its factorial tenets. It provides an environmental lens for broadly assessing soilscapes, not assessing dynamic soil processes. Once mapped and classified, soils become static elements, which — while societally useful, misrepresents their true biodynamic nature. To heal these wounds, process biodynamics should be stressed as first genetic principles in pedology and soil-geomorphology. A processbiodynamic approach, with supporting genetic language, provides a way forward and fosters a fresh array of interpretive options.
Keywords: biodynamics, soil science, geomorphology, pedology, biomantle, pedogenic models
- 1:20 PM Author(s):
*John B. Anderton, PhD - Northern Michigan
Abstract Title: Landforms, Soils, and Archaeology in the Pictured Rocks National Lakeshore, Alger County, Michigan: A Preliminary Report
Recently, a three-year project was begun in the Pictured Rocks National Lakeshore to identify, map, and when possible, date landforms that have potential to contain significant evidence of prehistoric archaeological occupations. To date, archaeological survey within the Lakeshore has resulted in the identification of 35 archeological sites, the majority of which are historic Euro-American occupations. Unfortunately, however, the prehistoric Native American occupation of the Pictured Rocks is far less well-known. The presence of considerable ground cover has hindered archeological inventory at Pictured Rocks. Archaeological survey must be accomplished with labor-intensive closeinterval shovel testing in order to expose surface and subsurface prehistoric materials. The potential to miss evidence of small prehistoric occupations is considerable. Analysis of existing soil maps and remote sensing imagery has identified several ancient shorelines, which previous studies in the region have identified as high probability areas for archaeological sites. Use of the POD Index as a dating technique for landform surfaces also suggests a chronology of landscape evolution that is useful for accurate future archeological study at Pictured Rocks by focusing efforts on components of the prehistoric landscape that actually have potential to contain intact evidence of early human occupation and use of the Lake Superior shore. When completed, this study will enable future archeological research in the Lakeshore to better understand and focus upon those specific areas of the Pictured Rocks that have actual potential to contain intact prehistoric data, and will also assist NPS personnel in making informed accurate cultural resource management decisions.
Keywords: Shorelines, Archaeology, Soils
- 1:40 PM Author(s):
*Bradley E. Suther - University of Georgia Department of Geography
David S. Leigh - University of Georgia Department of Geography
Abstract Title: Soil Chronosequence of the Little River Valley, Atlantic Coastal Plain, North Carolina
A soil chronosequence of alluvial terraces in the Coastal Plain of North Carolina examines morphological, mineralogical, and chemical properties. The study area is 3 km wide and contains at least five Quaternary terraces and a modern floodplain along the Little River, which drains 800 km2 of the Sandhills of the upper Coastal Plain. Ages for the terraces are provided by opticallystimulated luminescence (OSL) dating. Entisols occur on floodplains formed in late Holocene sediment and have 10YR 5/4 C horizons that contain 1 to 4 % clay and a clay mineral assemblage of >50% kaolinite, with smaller proportions of hydroxy-interlayered vermiculite (HIV), smectite, and quartz. Inceptisols occur on the lowest terrace (T1) in 12.0 ± 2.9 ka sediments and have Bw horizons that are 10YR 5/6, 0.25 m thick, and contain 2 to 4 % clay and >50 % kaolinite, with smaller proportions of HIV and quartz. Soils on T2 - T5 are Ultisols formed in 17.4 ± 4.5 to 93.9 ± 15.9 ka sediments with Bt horizons that become progressively redder, higher in clay content, and deeper with increasing age, culminating with 7.5YR hues, 25 to 30 % clay, >1 m B horizon thickness, and equal proportions of kaolinite and gibbsite. Parameters including B horizon dithionite- and oxalate- extractable Fe and total chemistry of the
Keywords: Atlantic Coastal Plain, chronology, chronosequences, clay mineralogy, North America, North Carolina, optically-stimulated luminescence, leistocene, Quaternary, soils, terraces, Ultisols, United States
- 2:00 PM Author(s):
*David S. Leigh - University of Georgia Department of Geography
Abstract Title: Holocene Landscape Evolution and Soils in the Raven Fork Valley, Southern Blue Ridge Mountains, USA
Colluvial and alluvial stratigraphy, pedology, and numerical ages are presented for soils in the lower three kilometers of the valley of Raven Fork, a mountain stream draining 194 km^2 of high relief (1.3 km) terrain of the Southern Blue Ridge Mountains in western North Carolina. Lower hillslopes, alluvial/colluvial fans, and alluvial bottomlands (first terrace and floodplain) are described. Standard methods for subsurface investigations (core holes, excavation units, exposures) are used in conjunction with extensive archeological excavations. Soil-age relationships are established from radiocarbon and luminescence ages, cultural chronologies, and relative dating techniques. Results show a distinct progression of pedogenic alteration over the last 11,000 years for alluvial deposits (floodplain and terrace) with an incipient argillic horizon marking the maximum pedogenic expression in the oldest alluvium (8,000- 11,000 BP). Hillslope deposits are less distinct in terms of their age relationships, but tend to exhibit numerous buried A horizons. The geochronology indicates episodic periods of rapid sedimentation that may be correlated with climate and land use changes.
Keywords: Appalachian, sediment, colluvium, hillslope, terrace, archeology
- 2:20 PM Author(s):
*David J. Brown - Montana State University, Bozeman
Shannon A. Mahan - USGS, Denver
Abstract Title: Dambo geography, geomorphology and soil formation in Uganda
Dambos? seasonally saturated, channelless valley floors?serve as important hydrologic, fertility and geochemical reservoirs throughout Central and Southern Africa. Yet little is known about the formation of dambos. For this study on weathered granitic gneiss in central Uganda, we characterized 1st and 2nd order dambo transects in detail (grain-size analysis, clay mineralogy, color and carbon). Proximal VNIR diffuse reflectance spectroscopy was used to estimate soil properties elsewhere in the catchment. Sandy sedimentary strata marking highenergy fluvial events at ~ 35, 33, 16, 10.4, 8.5-8.3, and 5.9 ka (cal yr BP) were dated using Optically Stimulated Luminescence (OSL). Most of these events were correlated with relatively wet periods in the regional climate record, often in temporal proximity to rapid climate change. The abundance of secondary smectites in lower dambo positions and the persistence of saprolite micas indicate high dambo soil solution [Si(OH)4] due to catenary weathering and leaching of silica from upland areas. Soil morphology, grain-size analysis, mineralogy and optical dating suggest that dambo seepage zones or “bottoms” mark relic channels, with the most recent channel incision correlated to the global “8.2 ka” event. Dambo margins are more stable, with sands dated at ~ 35 ka lying just 24 m away from a relic channel. Evidence from this study suggests that dambos are shaped through the interaction of (i) hillslope sediment erosion and deposition; (ii) episodic channel flow and sediment transport; and (iii) upland weathering and leaching leading to geochemical enrichment in dambo soils.
Keywords: wetland, catena, Late Quaternary, VNIR spectroscopy, clay mineralogy, East Africa
Session Description: This series of three special paper sessions are co-sponsored by the Coastal and Marine Geography (CoMa) and Geomorphology specialty groups. The research presented in the paper sessions cover a broad spectrum of spatial and temporal scales within aeolian geomorphology.