Lower Paleozoic deep-water facies of the Medfra area, central Alaska: A section in <i>Geologic studies in Alaska by the U.S. Geological Survey, 1997</i>

Abstract

Cover. The Mint River is one of many drainages in the northwestern Seward Peninsula that provide surface runoff and sediment load into Lapp Lagoon and the Bering Sea. Recent geochemical studies (see article by Parnow and others, this volume) indicate that stream sediments collected from some drainages in this area contain anomalous concentrations of arsenic and tin, reflecting the presence of known tin-bearing granites and associated mineral deposits in this area. Although detrital arsenic and tin may be naturally entering the nearshore marine environment, the data suggest that solution transport of metals is extremely insignificant. This publication is also available online at: http://g ree nwood.c r.usgs.gov /pu b/ppa pers/p 1614/ Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not imply endorsement by the U.S. Government The eight papers that follow continue the series 1 of U.S. Geological Survey (USGS) reports on investigations in the geologic sciences in Alaska. The series presents new and sometimes preliminary findings that are of interest to earth scientists in academia, government, and industry; to land and resource managers; and to the general public. Reports presented in Geologic Studies in Alaska cover a broad spectrum of topics from all parts of the State ( fig. 1), which serves to emphasize the diversity of USGS efforts to meet the Nation's needs for earth-science information in Alaska. Library of Congress Cataloging-in-Publication DataThe papers in this volume are organized under the topics Resources, Geologic Framework, and Environment and Climate. Such an organization is intended to reflect the scope and objectives of USGS programs currently active in Alaska. Resource papers include one that presents detailed observations from a Mississippian Zn-Pb-Cu-Ag occurrence in the Brooks Range (Werdon). Mineralogic, chemical, and isotopic data provide the basis for a proposed relationship between this vein-breccia deposit and the shale-hosted massive sulfide deposit type, which includes the active Red Dog mine in the western Brooks Range. Also included under the topic of Resources is a paper that presents geochemical and isotopic data from the Greens Creek and Woewodski Island volcanogenic massive sulfide deposits in southeastern Alaska (Newberry and Brew). The depositional environment and sedimentological setting of Tertiary coal beds in the Matanuska and Susitna Valleys is the focus of a third paper under the topic of Resources (Flores and others).Geologic Framework studies provide background information that is the scientific basis for present and future studies of the environment, mineral and energy resources, paleoclimate, and hazards in Alaska. One paper presents the results of sedimentologic and paleontologic comparisons of lower Paleozoic, deep-water-facies rock units in central Alaska (Dumoulin and others). The authors show which of these units are likely to correlate with one another, suggest likely source regions, and provide a structural r...

Lower Silurian conodonts from the Shine Jinst region, southwestern Mongolia

“…In more recent global zonation schemes (Cramer et al, 2011; Melchin et al, 2012), there is a degree of uncertainty concerning the correlation of the expansa Zone to the graptolite zonation, although it is still found to span the Rhuddanian-Aeronian boundary. Pseudolonchodina expansa has also been reported from Canada (Zhang and Barnes, 2002), Alaska (Dumoulin et al, 1997), Estonia (for references, see Männik and Malkowski, 1998), Poland (Männik and Malkowski, 1998), Russia (Männik et al, 2009), Australia (Simpson and Talent, 1995), and Spain (Sarmiento et al, 1994).…”