Research about North Dakota, South Dakota, Montana

USGS2019

Study design and methods for a wetland condition assessment on U.S. Fish and Wildlife Service fee-title lands in the Prairie Pothole Region of North Dakota, South Dakota, and Montana, USA

The U.S. Fish and Wildlife Service (FWS) manages wetlands and grasslands for wildlife habitat throughout the central North American Prairie Pothole Region (PPR). PPR wetlands, or potholes, are widely recognized as critical habitats for North American migratory waterfowl, waterbirds, and other wildlife. Potholes also provide other ecosystem services such as carbon sequestration, flood mitigation, filtration of pollutants, groundwater recharge, nutrient retention, and recreational opportunities. Wetland condition assessments have been completed nationally at coarse scales, but focused, regionwide assessments of the biological condition of potholes managed by the FWS are lacking. Therefore, FWS personnel require information pertaining to the biological condition and status of wetlands on FWS fee-title lands in the PPR to support management, restoration, and acquisition efforts. The biological condition of wetlands typically is reflected by their plant communities, and these communities correspond to past and current management and anthropogenic disturbances; thus, plant communities are a suitable surrogate of wetland condition. This report describes the study design, selection of sample sites, and field survey methods for a wetland condition assessment for FWS fee-title lands in the PPR of North Dakota, South Dakota, and Montana. Various spatial databases were gathered (for example, National Wetlands Inventory) to identify and assess potholes on FWS fee-title lands and to facilitate the selection of study sites. A spatially balanced, site-selection process resulted in the inclusion of 125 temporarily and 125 seasonally ponded potholes distributed across the area of interest; the first 100 for each classification were considered the primary study sites, whereas the remaining 25 were considered an oversample to replace those deemed not appropriate for sampling by field crews. Study sites were within native prairie and reseeded grasslands on FWS National Wildlife Refuges and Waterfowl Production Areas and are distributed among the primary physiographic subregions of the PPR: the Glaciated Plains, Missouri Coteau, and Prairie Coteau; a small number of sites also are within the Lake Agassiz Plain and Turtle Mountains. Site assessment protocols, vegetation survey methods, data analyses, and condition categories (for example, poor, good, very good) for the wetland assessment are based on the North Dakota Rapid Assessment Method and an Index of Plant Community Integrity developed for potholes. Results of the wetland condition assessment will aid FWS staff in assessing past and current management and help to identify priority areas for future management and acquisition.

North Dakota, South Dakota, Montana↗

USGS1980

Composition and properties of the Pierre Shale and equivalent rocks, northern Great Plains region

The Pierre Shale and equivalent rocks of Late Cretaceous age consist in the east-central Dakotas of several hundred feet of offshore-marine shale and minor marl; in west-central Montana near the sediment source the equivalents of the Pierre Shale consist of several thousand feet of volcanic-rich and mostly nonmarine sediments; and in the area between, both types of rock are separated by tongues of nearshore-marine siltstone and sandstone that mark three major transgressions of the sea across the area. The major-, minor-, and trace-element composition was determined for 226 samples of these rocks, and the mineralogical composition was determined for 1,350 samples. Slurry pH, Atterberg limits, and grain and bulk densities were determined on some samples. The arithmetic mean, in percent, and standard deviation (in parentheses) of major and minor elements, mostly in shale and siltstone and excluding the 23 chemically analyzed bentonite samples, are as follows: SiO2 60.8 (7.9) Al2O3 14.4 (2.5) Fe2O3 3.4 (1.4) FeO 1.1 (1.2) MgO 2.2 (1.0) CaO 2.7 (0.48) Na2O 1.1 (0.56) K2O 2.4 (0.57) H2O- 3.2 (1.3) H2O+ 4.3 (1.2) TiO2 0.58 (0.12) P2O5 0.14 (0.073) S 0.37 (1.1) F 0.71 (0.15) Cl 0.16 (0.024) CO2 2.1 (7.0) C, organic 0.94 (1.8) The mean and standard deviation of minerals as determined by X-ray methods, excluding bentonite samples, is as follows: clay minerals, 53 (20); quartz, 24 (13); cristobalite, 1 (5); potassium-feldspar, 1 (2); plagioclase, 6 (7); anorthite content from 20 to 40 percent; calcite, 5 (14); dolomite, 4 (7); organic matter, 1 (2); and sparsely scattered gypsum, jarosite, pyrite, zeolites, augite, siderite, and probably minor amounts of hydrated iron-manganese (Fe-Mn) oxides. The mean and standard deviation of the clay-mineral fraction is as follows: mixed-layer illite-smectite, 70 (20); illite, 16 (9); chlorite, 3 (6); and kaolinite, 9 (13). The mixed-layer clay, except in the Montana disturbed belt, is a random interlayering of 20 to 60 percent illite-type layers, about 35 percent beidelite-type layers, and the remainder montmorillonite-type layers; chlorite or vermiculite layers are rare. Most bentonite differs from shale in its small quartz content, rarely more than a few percent, in the more calcic composition and hightemperature thermal state of its plagioclase, and in its rare kaolinite, near absence of chlorite, and lack of illite-either free or mixed layered with smectite. Bentonite commonly consists of more than 90 percent smectite in which montmorillonite is interlayered with a smaller amount of beidellite. The clay-mineral composition of marine rock, including proportions of layers in the dominant illite-smectite, averages about the same as in the nonmarine rock, though in the latter the composition is more variable. The average content of major chemical constituents also is closely similar, partly because the large clay content of fine-grained offshore-marine shale is balanced by the small clay content of nearshore-marine siltstone and sandstone. In addition, the alumina and alkalic elements in an average of 10 percent more clay in marine rock are partly balanced by these constituents in the 5 percent more feldspar in nonmarine rock. Much of the observed regional and stratigraphic variation in maj or constituents is the result of the three major east-west migrations of the depositional sites of nearshore-marine sandstone and siltstone. Dolomite is found almost exclusively in relatively coarse-grained rock, particularly in nearshore-marine siltstone where diagenetic dolomite is expected, but it is found almost as frequently in nonmarine siltstone. Amounts of minor constituents are nearly equal in marine and nonmarine rocks, except that pyrite and consequently sulfur are relatively sparse in nonmarine rock. Average amounts of organic matter found in marine and nonmarine rocks are nearly identical. However, organic matter in nonmarine rock occurs almost entirely in volumetric

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