Paleomagnetic Study of the Portage Lake Volcanics exposed in the Quincy Mine

A detailed paleomagnetic and rock-magnetic investigation was conducted on thirty six basaltic flows of the ~1095 Ma Portage Lake Volcanics. The flows were sampled along the East Adit of the Quincy Mine (Hancock, MI). Thirty two flows yielded well-defined primary magnetization directions carried by magnetite. A secondary magnetization component carried by hematite was also found in twenty nine flows. After correction for serial correlation between the flows, nineteen independent mean directions were calculated. The corresponding paleomagnetic pole is located at 25.5 °N, 182.1 °W (A95 = 3.5°). The new pole overlaps with the pole from the ~1087 Ma Lake Shore Traps suggesting a standstill of the North American plate during that time period. The low angular dispersion of virtual geomagnetic poles (S = 7.9°) suggests that the flows were erupted within a short time period, or that the strength of geomagnetic secular variation was lower than that of the recent field.

Observatory - Portage Lake

On verso: University of Michigan News Service; Ann Arbor, Michigan

Map of the Huron River Valley from Surveys made in 1908-1909 by G. S. Williams. 5119 [Portage Lake]

[Portage Lake, 1908: Map of the Huron River Valley Scanned in two parts and combined using PhotoShop CS6 PhotoMerge command]

Portage lake smelting works

Stereograph

Huron Stamp Mill, Portage Lake

Stereograph

Members of Bryant Walker Nature Club, standing outdoors, Portage Lake, 1919 or 1920

front, left to right: Wilbur MacAlpine, W.W. Newcomb, Bryant Walker, G. Sutton, H.B. Baker, Cecil Billington, A.G. Ruthven, Norman Wood, A.W. Andrews, A. Fenton Combs; Back, left to right: F.M. Gaige, Fred McCain

Application of Drifting Buoy Technologies for Coastal Watershed and Ecosystem, Ann Arbor, Michigan, June 5-7,2005: workshop proceedings

The Alliance for Coastal Technologies (ACT) Partner University of Michigan convened a workshop on the Applications of Drifting Buoy Technologies for Coastal Watershed and Ecosystem Modeling in Ann Arbor, Michigan on June 5 to 7,2005. The objectives of the workshop were to: (1) educate potential users (managers and scientists) about the current capabilities and uses of drifting buoy technologies; (2) provide an opportunity for users (managers and scientists) to experience first hand the deployment and retrieval of various drifting buoys, as well as experience the capabilities of the buoys' technologies; (3) engage manufacturers with scientists and managers in discussions on drifting buoys' capabilities and their requirements to promote further applications of these systems; (4) promote a dialogue about realistic advantages and limitations of current drifting buoy technologies; and (5) develop a set of key recommendations for advancing both the capabilities and uses of drifting buoy technologies for coastal watershed and ecosystem modeling. To achieve these goals, representatives from research, academia, industry, and resource management were invited to participate in this workshop. Attendees obtained "hands on" experience as they participated in the deployment and retrieval of various drifting buoy systems on Big Portage Lake, a 644 acre lake northwest of Ann Arbor. Working groups then convened for discussions on current commercial usages and environmental monitoring approaches including; user requirements for drifting buoys, current status of drifting buoy systems and enabling technologies, and the challenges and strategies for bringing new drifting buoys "on-line". The following general recommendations were made to: 1). organize a testing program of drifting buoys for marketing their capabilities to resource managers and users. 2). develop a fact sheet to highlight the utility of drifting buoys. 3). facilitate technology transfer for advancements in drifter buoys that may be occurring through military funding and development in order to enhance their technical capability for environmental applications. (pdf contains 18 pages)

The origin of a large (>3km) maar volcano by coalescence of multiple shallow craters: Lake Purrumbete maar, southeastern Australia

Lake Purrumbete maar is located in the intraplate, monogenetic Newer Volcanics Province in southeastern Australia. The extremely large crater of 3000. m in diameter formed on an intersection of two fault lines and comprises at least three coalesced vents. The evolution of these vents is controlled by the interaction of the tectonic setting and the properties of both hard and soft rock aquifers. Lithics in the maar deposits originate from country rock formations less than 300. m deep, indicating that the large size of the crater cannot only be the result of the downwards migration of the explosion foci in a single vent. Vertical crater walls and primary inward dipping beds evidence that the original size of the crater has been largely preserved. Detailed mapping of the facies distributions, the direction of transport of base surges and pyroclastic flows, and the distribution of ballistic block fields, form the basis for the reconstruction of the complex eruption history,which is characterised by alternations of the eruption style between relatively dry and wet phreatomagmatic conditions, and migration of the vent location along tectonic structures. Three temporally separated eruption phases are recognised, each starting at the same crater located directly at the intersection of two local fault lines. Activity then moved quickly to different locations. A significant volcanic hiatus between two of the three phases shows that the magmatic system was reactivated. The enlargement of especially the main crater by both lateral and vertical growth led to the interception of the individual craters and the formation of the large circular crater. Lake Purrumbete maar is an excellent example of how complicated the evolution of large, seemingly simple, circular maar volcanoes can be, and raises the question if these systems are actually monogenetic.

The ionic composition of surface waters in the English Lake District, related to bedrock geology, with some singular facts and speculation on the existence of mineral-rich groundwaters

This article is based on a survey of tarns conducted mainly in the summers of 1983 to 1985, plus a survey made in the winter of 1985, in which streams were sampled on the wide variety of rock-types occurring on the fringes of the Lake District. Differences in composition of major ions and their concentrations in the surface waters of Cumbria reflect the complex geological structure of the region. At altitudes above 300 m, on Borrowdale Volcanics and Skiddaw Slates, surface waters are derived from atmospheric precipitation, with additional inputs of some ions - especially calcium and bicarbonate - from catchment rocks and soils. In some of the low-lying large lakes on the fringes of the central fells, water composition is also dominated by inputs from upper catchments; examples are Wastwater, Ullswater and Haweswater. However in other lakes there is evidence (Derwentwater and Bassenthwaite Lake) of inputs from saline groundwater.

Quantitative PCR assay of sewage-associated Bacteroides markers to assess sewage pollution in an urban lake in Dhaka, Bangladesh

This paper aimed to assess the magnitude of sewage pollution in an urban lake in Dhaka, Bangladesh by using Quantitative PCR (qPCR) of sewage-associated Bacteroides HF183 markers. PCR was also used for the quantitative detection of ruminant wastewater-associated CF128 markers along with the enumeration of traditional fecal indicator bacteria, namely, enterococci. The number of enterococci in lake water samples ranged from 1.1 x 104 to 1.9 x 105 CFU/100 ml of water. From the 20 water samples tested, 14 (70%) and 7 (35%) were PCR positive for the HF183 and CF128 markers, respectively. The numbers of the HF183 and CF128 markers in lake water samples were 3.9 x 104 to 6.3 × 107 and 9.3 x 103 to 6.3 x 105 genomic units (GU)/100 ml of water, respectively. The high numbers of enterococci and the HF183 markers indicate sewage pollution and potential health risks to those who use the lake water for non-potable purposes such as bathing and washing clothes. This is the first study that investigated the presence of microbial source tracking (MST) markers in Dhaka, Bangladesh where diarrhoeal diseases is one of the major causes of childhood mortality. The molecular assay as used in this study can provide valuable information on the extent of sewage pollution, thus facilitating the development of robust strategies to minimise potential health risks.