Southwestern Iowa Research Articles

Comparative Precambrian Stratigraphy Along Mid-Continent Rift Trend: ABSTRACT

In 1983, leasing agents representing several major exploration corporations appeared in the Lake Superior district of northern Wisconsin, an area best known for its exposures of Duluth gabbro and Mellen black granite, and not for its hydrocarbon potential. The geologic column of interest is the 7,620 + m (25,000 + ft) thick sequence termed the Keweenawan Supergroup (Precambrian), a basal shale that has been Rb-Sr-age dated at 1,075 ± 50 billion years. Within the past decade, this sequence has been recognized as having been deposited in response to tensional processes resulting in the development of a rift system. This Mid-Continent rift is best outlined by gravity and can be traced from the Keweenawan Peninsula of Michigan across northern Wisconsin, Minneso a, Iowa, and Nebraska into northeastern Kansas, a distance of 1,290 km (800 mi). An organic-rich shale source unit is known in the Lake Superior area, where it creates intermittent subsurface oil seeps in the White Pine copper mine of Michigan. To the southwest along the trend of the rift, the extent of Keweenawan-equivalent sediments are masked by Paleozoic and younger sediments, increasing from a feather edge in central Minnesota to a reported 1,524 m (5,000 ft) in southwestern Iowa. In the mid-1960s, a natural-gas-storage drilling program centered on Dakota County, Minnesota, cored extensive thicknesses of Precambrian clastics, subsequently named the Solor Church Formation. This subsurface unit, together with surface exposures of the younger Hinckley Sandstone and Fond du Lac Formation, constitutes the Keweenawan section of Minnesota. Less is known of the Kewee awan-equivalent lithology of Iowa, where the Minnesota terminology is being used in geophysical studies of the Mid-Continent gravity high. Here, a late Precambrian red clastic sequence is known, apparently similar to that termed the Rice Formation in Kansas--a carbonate subordinate sequence of sandy shales and feldspathic sandstones. End_of_Article - Last_Page 1317------------

Seasonal Development and Color Morph Determination of the Yellowheaded Fireworm (Lepidoptera: Tortricidae)

The yellow headed fireworm, Acleris minuta (Robinson), has four discrete generations in southwestern Iowa: the overwintering gray color morph flies in April followed by the first-, second-, and third-generation flights of the orange color morph in late May, late June, and early August, respectively. The offspring of the third summer generation begin emerging as adults in mid-September. These gray moths overwinter and mate the following spring. Photoperiod triggers color morph determination. Repeated exposures of larvae to photophases of 12 h or less produce gray morph development and must begin not later than the fourth stadium.

Dynamic Simulation of Sediment Discharge from Agricultural Watersheds

ABSTRACT SOIL erosion and sediment transport from small agricultural watersheds in southwestern Iowa were estimated by applying a modified version of the SEDLAB simulation model. The effects of crop canopy, ground cover, and subsurface land use effects were represented by revised and newly developed functions. The results showed that the revised SEDLAB model will provide reasonably accurate estimates of the erosion and sediment discharge of upland agricultural watersheds for different hydrologic, vegetative, and cultural conditions. Tests with data from an adjacent watershed showed that the model may be transferred to similar uncalibrated watersheds.

The paleoecology of a “middle limestone member” (Leavenworth) of an upper Carboniferous (Stephanian) cyclothem midcontinent, U.S.A.

This paper is devoted to the documentation of the lithological and paleontological parameters relative to deposition of the very thin (usually less than. 1 m thickness) Late Carboniferous limestone unit, the Leavenworth Limestone, extensively exposed in the American midcontinent. The Leavenworth Limestone has long been thought of as a classic example of pronounced lateral sediment homogeneity, and this study corroborates this claim. The Leavenworth outcrop belt is exposed from northern Oklahoma, across eastern Kansas, northwestern Missouri, and into southeastern Nebraska. No outcrops of Leavenworth Limestone are present in southwestern Iowa, but the results from two shallow core bores from this area have been incorporated in this study and complete a rock traverse of approximately 500 kms. Field relationships indicate that the Leavenworth Limestone exposures were essentially deposited parallel to what must have been the eastern shoreline of a Late Carboniferous epicontinental sea. Accordingly, it is shown that the Leavenworth was laid down within intermediate water depths on a slowly subsiding carbonate platform. The facies distribution indicates that the majority of Leavenworth locations (25) can be designated as a skeletal wackestone facies, with only four other locations, all restricted to the southern end of the outcrop belt, assigned to an oncolithic facies. This facies distribution pattern reflects increasing southward proximity to a paleo-highland source area. Still farther southward, beyond the basin margin, the Leavenworth Limestone, and all other thin Late Carboniferous limestones, lens-out and merge into the clastic wedge of the Vamoosa Formation of central and northern Oklahoma. Although the Leavenworth Limestone is unrecognizable per se within this clastic wedge, it does extend farther southward than any other Late Carboniferous unit. The Leavenworth Limestone contains remains of all major Late Paleozoic biotic groups, although none of the represented groups can be considered as occurring in great abundance. The foraminifers (agglutinated, silicified, smaller calcareous, and fusulinids) are perhaps the best represented faunal groups and show extensive lateral distribution patterns thought to reflect the overall Leavenworth lateral homogeneity. The algal assemblage is sparse, although it is characterized by consistent fragments of dasyclads and distinct types of algally coated-grains. Miscellaneous microfossils are represented by sponge spicules, holothurian sclerites, scolecodonts, “fish” remains, and conodonts, all of which occur in rather limited abundances and within spotty distribution patterns. Trace fossils occur mainly on the upper and lower bedding plane surfaces of the Leavenworth Limestone, and these consist ofChondrites, Asteriacites, and plowing trails attributed to gastropods. Throughout its thickness the Leavenworth Limestone shows abundant evidence of extensive organism burrowing and homogenization of the sediment. Many burrows are filled with distinctive fecal pellets associated with dispersed scolecodont remains. This association suggests an abundant original Leavenworth infauna composed primarily of marine worms. The megafauna retrieved from the Leavenworth is sparse and is dominated by a few groups of brachiopods and gastropods. It is thought that the delimiting factor responsible for the rather poor megafossil exploitation can be attributed to the dominantly muddy substrate, which most organisms find as a stress environment. The Leavenworth Limestone has always been thought of as the “middle limestone” member of MOORE's megacyclothem and as such was thought to represent deposition in waters that were “just awash”. Recent work by HECKEL, and his re-interpretation of cyclothem deposition in the midcontinental United States, suggests that the middle limestone member (Leavenworth) is the transgressive carbonate in a cyclothem overlain by fissile black shale now regarded as an offshore core shale that was deposited within the deepest waters of the cyclothem. This present interpretation of cyclothem deposition in the Late Carboniferous rocks of the midcontinantal United States seems best to explain the current observations.

Physical and Chemical Properties of Eroded Soil Aggregates

RAINFALL simulation was used to evaluate the characteristics of aggregates eroded from erosion plots on two loess soils in southwestern Iowa. The mean aggregate diameters (D50) for interrill erosion were 44 and 34 ^m for soils with 26% clay and 1.9% carbon and 22% clay and 0.8% carbon in their matrix, respectively. The D50 size increased as rilling occurred, but the percentage of increase was quite different for the soils. The D50 size increased by 91% for the soil with higher clay, whereas it increased by only 15% for the other soil. The eroded aggregates >50 ^m in diameter contained more clay and total nitrogen than did the aggregates <50 >im, when analyzed as a single fraction. The >50-/im aggregates were also enriched in clay and nitrogen when their contents were compared to those of the matrix soil. Enrichment was greater for interrill than for interrill plus rill erosion because of greater particle selectivity during the transport process. Equilibrium phosphorus concentration curves varied with aggregate size, suggesting that 250 to 50-jum aggregates are of greater importance in buffering soluble P levels and transporting labile P than larger aggregates...

In‐situ Measurement of Near‐surface Soil Strength by the Fall‐cone Device

AbstractThis study explored the use of the Swedish fall‐cone device for insitu measurements of shear strength near the surface of soils. A laboratory fall‐cone device was adapted for field use by replacing the original base and lengthening the cone stems. In‐situ strengths were measured on selected soils in southwestern Iowa and southeastern Nebraska. A small increase in water potential resulted in a large decrease in shear strength. A heavier cone gave a lower strength value than a lighter cone. The near‐surface strength of Sharpsburg soils in winter wheat fields was measured throughout the year. The strength immediately after fall planting was 10 to 20 kPa at about −3 kPa water potential. In the spring of 1980, largely because of consolidation from rainfall in the immediate post‐thaw period, the strength was 30 to 50 kPa. In contrast, the spring of 1981 was dry and consolidation did not occur; consequently, there was no increase in strength from that immediately after planting.

Three late‐glacial pollen and plant Macrofossil assemblages from Iowa

Abstract Late‐glacial pollen and plant macrofossil assemblages from the Brayton gravel pit in southwestern Iowa, Nichols silts in southeastern Iowa, and Summer Bog in northeastern Iowa indicate that a spruce‐larch forest was present between about 12,500 and 11,500 radiocarbon years before present (RCYBP). Some forest openings probably existed at Brayton and during the lower zone recognized at Sumner Bog, but not at Nichols. All Sites contain pollen of thermophilous species; macrofossils of Quercus rubra (northern red oak) and Corylus cornuta (beaked hazel) at Brayton and of Acer negundo (box elder) at Nichols indicate that some thermophilous plants were locally present. Fir trees were present in small numbers, but pine was absent.

Assessment of Potential for Fluid Hydrocarbons in Iowa: ABSTRACT

Iowa has traditionally been regarded with only passing interest by the petroleum exploration industry operating in the Mid-Continent. This has been primarily due to the lack of structural and stratigraphic information in the area of greatest oil potential, the southwest quarter of the state. Thick deposits of glacial drift and a thick, poorly understood Pennsylvanian section have obscured the character of underlying Paleozoic rock units and restricted exploration incentive and subsurface control in the area. Working with recently acquired geophysical and well-control data, the Iowa Geological Survey has constructed a series of structural and stratigraphic maps that suggest that the oil potential of the Forest City basin in southwestern Iowa should be reevaluated. Gravity and stratigraphic work along the northeast-trending Thurman-Redfield fault zone suggests vertical displacements of lower Paleozoic rocks of up to 1,000 ft (305 m). The abrupt termination of the large vertical component of the north-trending Humbolt fault against the Thurman-Redfield zone, and the recent recognition of left-lateral movement of the Humbolt fault in Nebraska and Kansas has led to speculation that transcurrent movement and associated structures could provide traps for oil migrating out of the basin. Stratigraphic mapping has also delineated a series of basins and uplifted areas throughout the Paleozoic column in Iowa, possibly associated with isostatic equilibration of the massive Keweenawan flood basalts of the Portage Lake Series, which forms the pronounced geop ysical feature known as the Mid-Continent geophysical anomaly. Details of these basins are not clear at this time, but the potential for stratigraphic traps associated with such features in this area should not be ignored. A series of maps and cross sections of the southwest quarter of Iowa has been prepared illustrating the results of recent and current studies. End_of_Article - Last_Page 683------------

Marital Satisfaction A s Perceived by Wives

This study was designed to determine the relative importance of specific sociological, economic, and psychological variables in explaining marital satisfaction. Data were collected from 163 two‐ parent families living in small towns in southwestern Iowa. Multivariate regression was used to analyze the data. The results of this study partially supported the general hypothesis that sociability and psychological factors would be more closely associated with marital satisfaction than would socioeconomic factors.The findings indicated that going places together as a family and marital decision making (jointly made by husbands and wives) regarding the best place for the family to live were positively related to marital satisfaction. On the other hand, borrowing and exchanging favors frequently with neighbors and frequency of money problems related to savings were negatively related to marital satisfaction.

Seasonal Runoff Losses of Nitrogen and Phosphorus from Missouri Valley Loess Watersheds

AbstractSeasonal losses of nitrogen and phosphorus in surface runoff were determined for a 7‐year period from three corn‐cropped watersheds in southwestern Iowa. Three seasonal periods were defined: fertilizer, seedbed, and establishment period from April through June (P1); reproduction and maturation period from July through November (P2); and residue period from December through March (P3).Most of the average annual total N and P losses were associated with the sediment portion of runoff and occurred during P1. The extreme susceptibility of the loess soils to erosion during P1 must be taken into account when designing conservation practices to control plant nutrient losses. Seasonal discharges of runoff, sediment, and nutrients were much lower from a level‐terraced watershed than from two contour‐farmed watersheds, which demonstrates the benefit of terracing in resource conservation.Average annual soluble N and P losses were quite low and never exceeded 1% of the annual fertilizer application. These losses were the highest during P3 from the contour‐farmed watersheds.Water and sediment weighted nutrient concentrations were the highest from the contour‐farmed watersheds during P3, when residues covered the soil surface. Leaching of soluble nutrients from the residue and the greater selectivity of the soil erosion process for the finer fractions of the soil (i.e., clay and organic material) during snowmelt runoff are probably the factors responsible.

Wives' Perceptions of Marital Decision Making

The objective of this study was to determine the relative importance of socioeconomic and demographic, value and goal orientation, perception, sociability, and satisfaction variables in explaining marital decision making as perceived by wives. The sample con sisted of 163 nuclear families living in small towns in southwestern Iowa. Multivariate regression was used to analyze the data. The results of this study partially supported the general hypothesis that sociability and psychological factors would be more closely asso ciated with marital decision making than socioeconomic factors.The findings indicated that marital satisfaction, going places together as a family, and the family income were positively related to joint decision making. On the other hand, the wife's employment outside the home, seeing and visiting with friends from work, the wife's perception of income adequacy, not being able to meet large bills, and the wife's inclina tion toward authority versus equality in regard to education were negatively related to joint decision making.

Soil Nitrate‐nitrogen Determined by Coring and Solution Extraction Techniques

AbstractSoil‐coring and solution‐extraction sampling techniques were compared for determining the content of NO3‐N in the soil profile of a Monona silt loam (Typic Hapludoll) in southwestern Iowa. The NO3‐N content of the 3.05‐m profile, determined by solution extraction, was 28% lower in 1972, 8% higher in 1973, and 13% lower in 1974 than that determined by soil coring. The profile difference in NO3‐N content between the two sampling techniques was insignificant in 1973 and 1974 but was highly significant (1%) in 1972.

Erosion of the Tarkio Drainage System, 1845-1976

ABSTRACT HISTORIC and geologic evidence indicated that channel and gully erosion was nearly nonexistent when the loess-mantled Tarkio Basin of southwestern Iowa and northwestern Missouri was settled about 1845. The pattern of channel developmentgleaned from old land surveys, records from drainage districts, highway bridge surveys, and other documents-is related to the intensity of agriculture and is complexly linked to the general runoff regimen and to changes in soil-water content along channel boundaries. Some channel enlargement during the post-settlement period, 1845-1976, is quantified. Channel profile changes during recent years, 1939-1976, are reconstructed. The excessive scour in a channel reach of West Tarkio Creek is tentatively explained on the basis of geomorphic principles and differences in substrata erodibility.

Settlement-Subsistence Variability In The Glenwood Locality, Southwestern Iowa

Central Plains tradition settlement distribution in Southwest Iowa is poorly understood. Patterns of both nucleated and dispersed forms seem to be represented. The known distribution in the Glenwood locality is examined and an algorithm presented that could explain the existing variability. Initial locality occupants relied heavily on hunting and gathering with minimal horticulture during the Neoatlantic climatic episode. Isolated homesteads were an efficacious adaption. During the dryer Pacific climatic episode attendant reduction of natural resources forced intensified horticulture which eventuated a more nucleated settlement pattern.

DIROFILARIASIS IN IOWA COYOTES

(Dirofilaria immitis) were found in eight of 220 (3.6%) coyotes (Canis latrans) collected from fur buyers in Adams, Carroll, Cass, and Warren counties in southwestern Iowa. Infections ranged from one to 23 worms per coyote.

Frogs of the Rana pipiens Complex in the Northern and Central Plains States

The geographic distributions of three forms of the Rana pipiens complex were determined from samples of populations collected in South Dakota, Nebraska, Kansas, northwestern Missouri and western Iowa. A few samples from Minnesota and North Dakota were also examined. In most samples, the different forms can readily be identified morphologically. Calls were analyzed for the northern and western forms and were found to correlate with the expected morphotypes. The northern and western forms are sympatric along the Missouri, Elkhorn and Platte Rivers in southeastern South Dakota, eastern Nebraska and western Iowa. Probable hybrids, together with both parental types, were found at a number of localities in the zone of sympatry. The eastern form occurs in southeastern Kansas and is found in sympatry with the western form along a narrow zone of overlap. The results of this study are consistent with the interpretation that the three forms are specifically distinct. The northern, western and eastern forms correspond to Rana pipiens, R. blairi and R. sphenocephala of other authors. Until recently, leopard frogs of the Rana pipiens complex have usually been considered to be members of a single wide-ranging species with gene exchange occurring readily between adjacent populations. H-owever, considerable evidence has accumulated which indicates that the complex may actually consist of a number of largely allopatric populations which are maintaining separate genetic identities. McAlister (1962), utilizing a morphological analysis of adult characters, suggested that there are three distinguishable morphologic types in Texas. Post and Pettus (1966) reported two morphologically distinct forms of Rana pipiens in eastern Colorado. Mecham (1968) described two morphologically distinct forms sympatric in the White Mountains of eastern Arizona. Littlejohn and Oldham (1968), utilizing sound spectrographic analysis of mating calls of male frogs, reported four different call types from the south central United States. Three of these correspond to the three morphotypes described by McAlister (1962) and were designated as western, eastern and southern types. The western call type

Nitrate Movement and its Distribution in the Soil Profile of Differentially Fertilized Corn Watersheds

AbstractNitrate movement within the 6.1‐m soil profile of a watershed in southwestern Iowa, fertilized at 448 kg N/ha per yr, resulted in a 720‐kg/ha increase in NO3‐N below the corn root zone during the 3‐year study. The NO3‐N concentration of the baseflow from the watershed increased during this period, indicating that some of the leached NO3‐N reached the ground water. The watershed fertilized at the recommended N rate (168 kg/ha per yr) did not increase the quantity of NO3‐N below the corn root zone; however, some NO3‐N leaching did occur.Between April 1971 and April 1974, the accumulation of NO3‐N in the profile of the excessively fertilized watershed moved from the 1.0‐ to 3.1‐m depth. Three‐fourths of NO3‐N movement occurred between June 1972 and April 1973 when 80 cm of precipitation caused 21 cm of percolation below the corn root zone (183 cm). The watershed fertilized with 168 kg N/ha per yr did not show any zones of significant NO3‐N accumulation in the soil profile at any of the sampling dates.The depth to the water table on the lowest contour sampled on the excessively fertilized watershed was 4.6 and 4.9 m in April 1973 and April 1974, respectively. The average NO3‐N concentration for these two sampling dates at the water table depth increased from 3.7 to 12.9 ppm. The average NO3‐N concentration at the water table depth on the normally fertilized watershed was 2.0 and 4.5 ppm in April 1973 and April 1974, respectively, with a water table depth of 3.0 m.

Sampling Procedures for Nitrogen and Phosphorus in Runoff

ABSTRACT THE nitrogen and phosphorus content of surface runoff from two watersheds in southwestern Iowa was analyzed for a 5-year period (1969-1973). Sampling procedures were evaluated for quantifying dis-charges of water-soluble N03-N, NH4-N, and inorganic P and sediment-associated Kjeldahl N and NaHC03-extractable P. The arith-metic mean nutrient concentration of samples collected during major runoff (defined as greater than 0.28 m3/sec), multiplied by the quantity of water or sediment discharged, compared favorably with a standard integration procedure for determining N and P discharges associated with surface runoff. Also, the arithmetic mean nutrient concentration of three samples collected during major runoff was adequate for determining storm discharges of water-soluble N03-N and NH4-N and of Kjeldahl N associated with sediment. Nitrate-nitrogen concentrations showed a progressive decrease from storm to storm, indicating that each storm should be sampled or an accounting made for this decrease to determine the storm quantity discharges of NO3-N during the cropping season. This storm-to-storm effect was not as evident for NH4-N, inorganic P, total Kjeldahl N, and NaHC03-extractable P, indicating that sampling of every event would not be required to determine cropping season quantity discharges of these nutrient con-stituents.

Quaternary Records of Microtus xanthognathus (Leach), the Yellow-Cheeked Vole, from Northwestern Arkansas and Southwestern Iowa

Quaternary Records of Microtus xanthognathus (Leach), the Yellow-Cheeked Vole, from Northwestern Arkansas and Southwestern Iowa

Quality of water discharged from two agricultural watersheds in southwestern Iowa

The quality of water discharged from a 157.5‐ha diversified conservation‐farmed watershed in southwestern Iowa was within acceptable limits for potable water except for the levels of ammonia, inorganic phosphorus, and coliform. Total coliform levels exceeded the established criteria on two occasions, and fecal coliform once during the 2‐year study. Nutrient concentration was high occasionally, but the nutrient quantities discharged from the watershed were low, the effectiveness of the level‐terrace system in controlling surface runoff and erosion thus being shown. Atrazine residue in the runoff and sediment was detected in only one sample. Even though several chlorinated hydrocarbon and organophosphate compounds had been applied to the watershed, none was detected in runoff or sediment. A comparison of the data from a 33.6‐ha contour‐farmed watershed with the data from the 157.5‐ha well‐planned conservation watershed showed the benefits and necessity of using some means of controlling runoff and erosion to prevent loss of agricultural chemicals that may degrade our surface waters.