[en] Three sets of experimental traps, which have been deployed for portions of two field years on Lake Michigan, provide useful data on the effect of design factors on the collection efficiency of traps in this environment. The data also suggest effects of seasonal limnological factors

[en] Results are reported from a study of the dynamics of silicon and the importance of biological utilization and recycling of this element in Lake Michigan

[en] We report the first detailed study of the paleomagnetism, U - Pb geochronology and major element geochemistry of Paleoproterozoic north-trending Marathon dykes north of Lake Superior. The paleomagnetic and geochemical results demonstrate that Marathon dykes can be divided into two subsets, one of normal magnetic polarity, the other of reverse polarity. Normal and reverse Marathon paleomagnetic poles, at 43^oN, 196^oE (dm = 9^o, dp = 7^o, number of dykes N = 16) and 51^oN, 175^oE (dm = 9^o, dp = 6^o, N 12), respectively, are statistically distinct and may indicate different ages of normal and reverse dyke emplacement. A U-Pb baddeleyite age of 2121_-7⁺¹⁴ Ma has been obtained at a normally magnetized Marathon paleomagnetic site. The reversely magnetized Marathon dykes are undated, but have a paleopole rather close to that of the reversely magnetized 2076_-4⁺⁵ Ma Fort Frances dykes and major element geochemical signatures as portrayed on Jensen plots that are identical to those of the Fort Frances swarm. Therefore, reverse Marathon and Fort Frances dykes could define a giant radiating dyke swarm focused south of Lake Superior, supporting models that associate these dykes with Paleoproterozoic rifting along the southern margin of the Superior Province. The Marathon and Fort Frances paleopoles continue a northwesterly trend in southern Superior Province paleopoles, which has recently been defined by results for 2216_-4⁺⁸ Ma Senneterre dykes and 2167 ± 2 Ma Biscotasing dykes. This trend contrasts with previous widely used polar wander paths for the same period that young in the opposite direction and illustrates the importance of collaborative studies of paleomagnetism and U - Pb geochronology. (author). 36 refs., 4 tabs., 10 figs

[en] During 1975, a sediment trap and current meter array was maintained at ANL station 75-5 in Lake Michigan. Samples collected at monthly intervals from these traps provided data at two depths which indicated considerable resuspension of surface sediment flocs, but only under the physical conditions of a relatively near-shore, high-energy environment. In order to establish whether resuspension is a general, lakewide phenomenon, even in lower energy environments, and whether its rate is variable in different regions of the lake, arrays of sediment traps were installed during 1976 at 5 stations across the southern basin of Lake Michigan. At four of the stations a current meter was located 1.5 m off bottom. Preliminary results are discussed

[en] Sediment entrapment rates determined from traps placed on the same mooring lines as current meters in Lake Michigan were plotted versus average kinetic energy density during periods when both sediment entrapment rate and current data were available. There is an indication that the sediment entrapment rates may be directly proportional to the available kinetic energy of the currents, which would be suspected in situations involving resuspension of sediment by the currents. The average direction of water motion at one meter at the bottom indicates that resuspended sediment will be transported toward the west

[en] The feasibility of using high resolution satellite imagery as an aid to defining the transport of particulate air pollution plumes and the determination of turbidities for widespread haze layers is discussed. Limitations of the technique are also noted

[en] During the 1976 field season, sediment traps and current meters were set out in the southern basin of Lake Michigan to study the relationship between suspended material and currents. The gross mineralogical and chemical characteristics of the bottom sediments at the locations of these experiments were determined

No abstract available

[en] The effects of cooling system intakes and discharges on Lake Michigan fishes are highly dependent on inshore species composition and spatial distribution which, in turn, are affected by natural hydrological conditions. Significant (5 to 10 C) short-term decreases in water temperature (due to upwelling) could cause cold shock in fish equilibrated to either ambient or plume temperatures; substantial changes in distribution due to avoidance or attraction responses; and resultant changes in susceptibility to impingement. The objectives of this study are to characterize the changes in fish species composition, density, and thermal distribution as a result of natural upwellings, and to relate these factors to intake and discharge effects. Day and night sampling was conducted in ambient (reference) and thermal plume waters near the Zion Nuclear Plant on four occasions between 17 July and 11 September 1975. Density-distribution patterns and species composition of fish were determined by means of gill nets, bottom trawls, seines, and a sonic fish locater

[en] An aircraft, a chartered boat, and a constant altitude balloon were used to study pollutant transformations over Lake Michigan in a Lagrangian frame of reference. The experiments were conducted during the summer under strong atmospheric stability where diffusion and dry deposition of pollutants can be neglected