Wind-aligned Drainage in Loess in Iowa

Analysis of stream valley alignment reveals that first-order valleys, which are formed entirely within Wisconsinan loess, show a strongly preferred orientation of N40-50 degrees W, within an otherwise random distribution. This alignment is present in NW, W Central, and Central Iowa. It is not apparent in S Iowa. In NE and E Iowa wind-aligned features change to a N60-70 degree W orientation. This is interpreted as wind-alignment of the low-order valleys within the loess, created by prevailing NW winds during or shortly after loess deposition. Higher order streams are controlled by the till landscape beneath the loess. The four directions of preferred orientation in these higher order valleys are coincident with till joints

Water Quality Monitoring (1988 to 1991) At The Iowa Academy of Science\u27s Parish Farm, Grundy County, Iowa

In May 1988 sampling was initiated to evaluate water quality in relation to management practices at Parish Farm, which is owned by Iowa Academy of Science. Initial results showed tile-line effluent to have high concentrations of nitrate-nitrogen (N03-N). Twelve monitoring wells were installed over a one year period to analyze shallow groundwater at the farm. The wells, tile lines, and surface water were sampled monthly, through October, 1991, and the water analyzed for N03-N and some pesticides. N03-N concentrations varied, related to landuse and management of adjacent areas. Greater N03-N concentrations were detected from row-cropped areas than in the restored wildlife-vegetation buffer strip and prairie areas. The greatest concentrations (up to 79 mg/L) were associated with greater amounts of fertilized corn in the cropping sequence. Concentrations of pesticides were dependent on various factors such as chemical properties, season, hydrologic events, and patterns of use. Atrazine was the pesticide most often detected and was present in 46% of the samples. Seven agricultural pesticides used on the farm were detected in water samples with a maximum detected concentration of 6.9 μ/gL (for alachlor). Pesticide and high N03-N concentrations were detected in wells beneath the restored natural vegetation buffer areas, probably as a result of groundwater transport from application areas upgradient. The data suggest that the buffer strips were not effective at removing N03-N or pesticides from the groundwater flowing through these areas. N03-N concentrations were high (often over 25 μg/L) during the study, in spite of improved N management on the farm. The high concentrations may be related to mobilization of excess residual N03-N that accumulated during the dry years prior to the monitoring

A Unique Exposure of Quaternary Deposits in Johnson County, Iowa

The Klein Quarry, in Johnson County, Iowa, exposes a unique section of Quaternary deposits. The section extends along the axis of a Late-Sangamon erosion surface. It is mantled by Wisconsinan loess: a 4-5m upper increment of Late-Wisconsinan loess and a thin increment (0.2 to 0.5m) of mixed loess and Wisconsinan-age pedisediment (\u27basal-loess sediments\u27). Some soil development has taken place in the basal-loess sediments (basal-loess paleosol), and this soil merges with the underlying Late-Sangamon Paleosol. The Late-Sangamon erosion surface is developed on Pre-Illinoian age deposits of the Wolf Creek Formation which include (from top to bottom) an upper basal till (the Aurora Till Member), a thin, laminated diamicton, and an underlying stratified fluvial sequence of sand, silt, and gravel. These overlie till of the Alburnett Formation which is locally preserved in low-relief sags on the underlying bedrock surface of Devonian Cedar Valley Limestone. Sedimentary structures, pebble fabrics, and stratigraphic relations suggest that: the stratified fluvial sequence originated as a proglacial fluvial outwash that evolved into a low-energy slackwater environment; the laminated diamicton was derived from glacial sediments which were resedimented and deposited in this slackwater environment; and this was followed by overriding of glacial ice and deposition of the basal till. The Late-Sangamon erosion surface is marked by a stone line and a relatively thin increment of associated pedisediment which overlies the stone line. Various hillslope components are exposed going down the Late-Sangamon paleohillslope. The erosion surface progressively truncates the Aurora Till Member, the laminated diamicton, and most of the stratified sequence of the Wolf Creek Formation. Properties of the stone line and pedisediment vary in a complex, but systematic way. The characteristics of the stone line and lowermost pedisediment vary downslope directly with textural variations in the different deposits underlying the erosion surface. The uppermost pedisediment, however, shows little relationship to the materials underlying the stone line. The upper, younger pedisediment has resulted from reworking older pedisediment and from transport of sediment from farther upslope. The greater transport distance and reworking results in greater sorting and a less direct relationship to local source materials. The Lare-Sangamon Paleosol formed on this paleohillslope, and is developed in the Late-Sangamon pedisediment, stone line, and the underlying Wolf Creek Formation deposits. Sedimentological variations in the pedisediment affect various paleosol properties. Thickness of the paleosol varies (1.8 to 2.3 m) directly with the thickness of pedisediment, becoming thicker down the paleoslope. The increase in paleosol thickness is also directly matched by an increase in B-horizon thickness. The pedologic and sedimentologic features indicate that the Late-Sangamon erosion surface - pedisediment - paleosol evolved slowly and systematically. Pedisediment muse have accumulated in the lower-slope positions at a slow enough rate that B-horizon soil development kept pace with sediment accumulation

A Farmdalian Pollen Diagram From East-Central Iowa

Pollen analysis of the Butler Farm buried peat in east-central Iowa suggests that a spruce-pine forest grew in the area during the Farmdalian Substage. Pine decreased and spruce increased in dominance as the peat accumulated. Radiocarbon dates indicate that the peat was deposited from 28,800 to 22,750 RCYBP. It is overlain by late Wisconsinan loess and underlain by a Sangamon paleosol developed on Illinoian till. The regional pollen data suggest a general cooling trend through Farmdale time

A late-glacial pollen sequence from northeastern Iowa : Sumner Bog revisited

https://ir.uiowa.edu/igs_tis/1002/thumbnail.jp

A Mid-Wisconsinan Pollen Diagram From Des Moines County, Iowa

Core samples of peat from beneath Wisconsinian loess in Des Moines County, Iowa, were analyzed for pollen. The pollen sequence, dating from 24,900 to 28,720 RCYBP (radiocarbon years before present), was divided into 2 zones based on relative pollen percentages and pollen concentration. Zone B, at the base of the peat, is dominated by Pinus and Picea and is interpreted to represent a closed-coniferous forest, comparable to the modern boreal forest. Zone A, at the very top of the peat, is marked by the decline of Pinus and the increased importance of Picea. This is a regional event which marks the change to the late-glacial Picea forest which was devoid of Pinus

Geologic Overview of the Paleozoic Plateau Region of Northeastern Iowa

Steep slopes, varied slope aspects, and entrenched stream valleys carved into Paleozoic-age rocks provide the geologic framework for the unique and diverse ecology of northeastern Iowa. Differential weathering and erosion of these variable rock types resulted in irregular surface slopes in a multi-stepped, high-relief landscape. Additionally, solution of carbonate bedrock produced karst topography, cavern systems, ice caves, cold-air drainage, and perennial groundwater springs. The so-called Driftless Area in Iowa was glaciated repeatedly in Pre-Illinoian time, and should not be called Driftless. The name Paleozoic Plateau for this physiographic region more accurately describes some of its special aspects and also incorporates the much larger region of distinctive physiography and ecology referred to by biologists. Although the bedrock geology provides the framework for this unique region, the high relief is a product of more recent geologic history. Evidence from studies of the upland Quaternary stratigraphy and erosional history, the development of the karst system, and the fluvial deposits in the stream valleys reveal a complex Pleistocene history. Stream erosion since the last episode of glaciation (ca. 500,000 years before present) produced the deeply dissected landscape. Current research suggests that the major episode of deep-valley incision occurred during the Wisconsinan. Numerous late-Wisconsinan terraces stand 12-25 m above the present streams. A large portion of northeastern Iowa\u27s rugged terrain is remarkably young

Site evaluation, design, operation, and installation of home sewage systems in Iowa

The demand for on-site waste treatment systems for dwellings not served by sewer systems continues to grow in Iowa. On-site systems, when properly designed and maintained, provide a viable means of treating septic tank effluent. A research project was initiated at Iowa State University to provide information for solving problems associated with design, location, and maintenance of on-site systems in Iowa. This publication is designed to report the results of the interdisciplinary research and provide information for sanitarians, extension personnel, and contractors on waste treatment systems.https://lib.dr.iastate.edu/specialreports/1083/thumbnail.jp

Geology of the Loess Hills Region

The narrow ridges and steep bluffs which extend in a narrow band along the Missouri Valley form the Loess Hills region. These bluffs stand in sharp contrast to the flat-lying Missouri River floodplain. The unique ridge forms are composed of thick accumulations of late Wisconsinan wind-blown silt (loess). Older Quaternary deposits as well as Cretaceous and Pennsylvanian bedrock outcrop beneath the loess in the region. The intricate texture of the topography results from the combined effects of eolian deposition, fluvial erosion, and mass-wasting. Physical properties of loess allow it to maintain nearly vertical faces when exposed. These properties also produce special problems: slope instability, severe gullying, and high erosion races. The high relief and rough terrain provide slope aspects which vary widely in exposure to sun, wind, and moisture. These factors have produced a mosaic of microenvironments noted for their unusually xeric ecology