Soil formation in Indian Mounds built from different parent materials in northeast Iowa

http://www.worldcat.org/oclc/550329

Geologic Overview, Description of Map Units, and Correlation Chart for the Surficial Geologic Materials Maps of the Letts Quadrangle, Iowa and the Blanchard Island Quadrangle, Illinois - Iowa

Includes Table of Contents, background, brief geologic history, description of map units, Figure 1, Acknowledgements, and references.https://ir.uiowa.edu/igs_ofm/1153/thumbnail.jp

Surficial geologic materials of the Blanchard Island Quadrangle, Illinois-Iowa

https://ir.uiowa.edu/igs_ofm/1003/thumbnail.jp

Surficial geologic materials of the Letts Quadrangle, Iowa

https://ir.uiowa.edu/igs_ofm/1000/thumbnail.jp

Karst Development in Northeastern Iowa

Karst landforms of northeastern lowa have developed on Silurian and Ordovician carbonate rocks through processes of dissolution and collapse. The karst areas are characterized by rapid infiltration, direct runoff into sinkholes, underground drainage through solution-enlarged fractures, bedding planes and caves, and groundwater discharge at springs. Mechanically induced karst is found along the Silurian Escarpment and in close proximity to major valleys, but the majority of northeastern Iowa\u27s karst features are solutional in origin. Collapse of rock and surficial deposits into solutional openings in underlying rock pose safety and engineering problems in the area. The direct connection of surfacewaters with shallow bedrock aquifers through sinkholes, swallows in streams, and rapid infiltration has resulted in degradation of the groundwater quality, posing possible health hazards to inhabitants of this region. These environmental problems can be reduced through recognition of the hazards posed by the presence of karst and through reasoned approaches to land management

Quaternary loess-paleosol sequences as examples of climate-driven sedimentary extremes

Loess is a widespread, wind-transported, silt-dominated deposit that contains geologic archives of atmospheric circulation and paleoclimate on continents. Loess may cover as much as 10% of the Earth’s land surface. It is composed mainly of quartz, feldspars, and clay minerals, with varying amounts of carbonate minerals. The geochemistry of loess differs from region to region, depending on source materials, but all loess is very high in SiO2 with lesser amounts of other major elements. Trends in loess downwind from source areas include systematic decreases in thickness and amounts of sand and coarse silt, and increases in amounts of fine silt and clay. Loess particle size also varies at a given locality over time within individual depositional packages. This variability may be a function of changing wind strengths, different source sediments, or some combination of the two. The classical concept of loess is that it is a product of glacial grinding, with subsequent entrainment by wind from outwash deposits. However, it is now known that other processes contribute to silt particle formation, including frost shattering, salt weathering, fluvial and colluvial comminution, eolian abrasion, and ballistic impact. Much debate has taken place over the concept of “desert” (nonglaciogenic) loess, which is widespread in some regions but of limited distribution elsewhere. Nevertheless, glacial silt production probably exceeds the amount of silt generated by all other processes. Much of the loess in or adjacent to deserts may be inherited silt-sized particles from siltstone, mudstone, shale, and volcanic ash. In many regions, loess is near dune fields or eolian sand sheets. A question that arises from this geographic assocation is whether or not eolian sand and loess should be considered facies of the same depositional unit. There are regions such as China where these deposits are interbedded, which supports the facies concept. In other regions, such as North America, detailed geochemical and isotopic analyses show that the majority of loess particles were derived from a different, and more distant source than eolian sand. Key to understanding loess stratigraphy and interpreting environments of the past is the recognition of buried soils (paleosols). Ancient soils can be recognized by their distinctive morphological features and by vertical changes in particle size, chemistry, and mineralogy. Paleosols represent past periods when loess sedimentation rates decreased to zero or slowed significantly. Thus, loess and their interstratified soils represent end members of a continuum of sedimentary extremes: high rates of sedimentation yield relatively unaltered loess in the stratigraphic record, whereas low or episodic rates of sedimentation commonly leave a record of buried soils. The shift between these sedimentary extremes is preserved in the long-term glacial-interglacial record of the Quaternary. Although it is now known that not all eolian silt is glaciogenic, in almost all loess regions, eolian sedimentation rates were much higher during glacial periods than during interglacial periods. Drier, colder climates, a decreased intensity of the hydrologic cycle, stronger or more-persistent winds, increased sediment supply, decreased vegetation cover, and increased sediment availability all probably contributed to the sedimentary “extreme” of rapid loess accumulation during the last glacial period. The present interglacial period represents an opposite sedimentary “extreme” of minimal loess sedimentation and i

Surficial geologic materials of the Des Moines Lobe of Iowa, Phase 7: Osceola County

https://ir.uiowa.edu/igs_ofm/1039/thumbnail.jp

Surficial geologic materials of the Des Moines Lobe of Iowa, Phase 6: Dickinson and Emmet Counties

https://ir.uiowa.edu/igs_ofm/1033/thumbnail.jp

Surficial geologic materials of the Des Moines Lobe of Iowa, Phase 7: Clay County, Iowa

https://ir.uiowa.edu/igs_ofm/1038/thumbnail.jp