The purpose of this paper is to document results of pore size analyses of rocks from the Astarte River Formation, central Baffin Island, for use in interpreting ground electromagnetic surveys that have been conducted in the central Baffin region. Results are presented for pore size distribution analyses of four black graphitic shale samples subjected to mercury injection porosimetry measurements. These measurements are essential for the electrical mechanism analysis of these samples. Porosity values are compared to those typical of mudstone or crystalline rocks.
Electrical resistivity measurements previously made on graphitic shale samples from the Astarte River Formation on Baffin Island indicate that they display weak to strong anisotropic characteristics, with low and high resistivities in the directions parallel & perpendicular to foliation respectively. The purpose of the study described in this paper is to determine the electrical conductivity mechanisms that resulted in those characteristics. Study methods included electrical resistivity and porosity measurements, graphite thin-section analysis, and scanning electron microscopy. Resistivity-related factors examined in the study include pore-fluid connectivity, the presence of graphite, and the insulating quality of quartz grain layers.
This paper presents results from a Quaternary mapping project conducted in two areas of central mainland Nunavut that were located beneath the Keewatin Ice Divide during the last glaciation. Field work included surficial mapping, regional-scale till sampling, stratigraphic studies, and ice-flow indicator surveys. The paper summarizes the findings related to ice flow directions, patterns, and the sequence of flow events in the two map areas. Preliminary interpretations are offered of the ice flow record from the oldest recognized ice-flow events to the most recent flows.
As the importance and dependence of specific mineral commodities increase, so does concern about their supply. The United States is currently 100 percent reliant on foreign sources for 20 mineral commodities and imports the majority of its supply of more than 50 mineral commodities. Mineral commodities that have important uses and face potential supply disruption are critical to American economic and national security. However, a mineral commodity's importance and the nature of its supply chain can change with time; a mineral commodity that may not have been considered critical 25 years ago may be critical today, and one considered critical today may not be so in the future. The U.S. Geological Survey has produced this volume to describe a select group of mineral commodities currently critical to our economy and security. For each mineral commodity covered, the authors provide a comprehensive look at (1) the commodity's use; (2) the geology and global distribution of the mineral deposit types that account for the present and possible future supply of the commodity; (3) the current status of production, reserves, and resources in the United States and globally; and (4) environmental considerations related to the commodity's production from different types of mineral deposits. The volume describes U.S. critical mineral resources in a global context, for no country can be self-sufficient for all its mineral commodity needs, and the United States will always rely on global mineral commodity supply chains. This volume provides the scientific understanding of critical mineral resources required for informed decisionmaking by those responsible for ensuring that the United States has a secure and sustainable supply of mineral commodities.
Many challenges, including climate change, face the Nation¿s water managers. The Intergovernmental Panel on Climate Change (IPCC) has provided estimates of how climate may change, but more understanding of the processes driving the changes, the sequences of the changes, and the manifestation of these global changes at different scales could be beneficial. Since the changes will likely affect fundamental drivers of the hydrological cycle, climate change may have a large impact on water resources and water resources managers. The purpose of this interagency report is to explore strategies to improve water management by tracking, anticipating, and responding to climate change. Charts and tables.
