Structural and U-Pb detrital zircon geochronologic constraints on the origin of the Condrey Mountain Schist, California - Oregon

The Condrey Mountain Schist (CMS) of the Klamath Mountains (northern California and southern Oregon) represent low grade oceanic and terrigenous sediments thrust beneath higher grade ophiolitic rocks of the Rattlesnake Creek Terrane (RCT). This study presents new U-Pb detrital zircon dates from the CMS, and from the possibly correlative basin rocks of the Galice Formation and accretionary rocks of the South Fork Mountain Schist. The Galice Formation yields a maximum depositional age of ca. 152 Ma with prominent date distributions of ca. 150-200 Ma (39% of analyzed grains), 200-600 Ma (1%), 600 - 1000 Ma (2%), and 1000-3200 Ma (58%). The South Fork Mountain Schist yields a detrital zircon age spectrum with a maximum depositional age of ca. 135 Ma, and prominent age distributions of ca. 120-200 Ma (28.5% of analyzed grains), 200-600 Ma (24%), 600-1000 (8.5%), and 1000-2850 (39%). An interior unit of the CMS has a maximum depositional age of ca. 136 Ma and contains detrital zircon age distributions within 136 to 200 Ma (24% of analyzed grains), 200 to 600 Ma (27.5%), 600 to 1000 Ma (10%), 1000 to 2300 Ma (38.5%). Structural, petrographic, and detrital zircon geochronologic similarities between the CMS and SFMS suggest a common provenance. Kinematic indicators within the Condrey Mountain shear zone, a shallowly dipping ductile structure separating the CMS from the RCT, suggest that the CMS was transported eastward during prograde metamorphism and exhumed during top-to-the-east normal faulting. A tonalitic intrusion from the exterior unit of the CMS yields an inferred igneous emplacement age of ca. 172 Ma. These relations indicate that the exterior CMS was tectonically emplaced at least 37 Myr prior to deposition of the interior CMS --Abstract, page iii

On the world-wide circulation of the deep water from the North Atlantic Ocean

Above the deeper waters of the North Atlantic that have entered from the circumpolar flow, convection in the Labrador Sea and overflow from the Mediterranean, Norwegian, and Greenland seas combine at mid-depth and circulate in the subarctic cyclonic gyre, and flow southward along the western boundary into the South Atlantic. Because of the nature of these sources the mid-depth waters of the North Atlantic are the warmest, most saline, highest in oxygen and lowest in silica of any of the mid-depth waters of the World Ocean. They have been called the North Atlantic Deep Water.In the Atlantic these characteristics have vertical extremes that separate the inflowing water from the far south into an upper and a lower layer (Reid et al., 1977). These characteristics are so strong that their patterns trace much of the large-scale circulation. Lateral extremes in these tracers extend southward along the western boundary of the Atlantic Ocean. They turn offshore near 50S and eastward with the circumpolar flow. The tracers indicate that some of the eastward flow turns northward along the western boundaries in the Indian and Pacific oceans, but the lateral extreme remains strong enough to give a clear signal all the way to the Drake Passag

The lead and zinc deposits in the sedimentary rocks of East Tennessee and Southwest Virginia

In its geographic and geologic relations this area forms a part of the Appalachian province, which extends from the Atlantic Coastal plain on the East to the Mississippi lowlands on the West and from Central Alabama to Southern New York. All parts of the region thus defined have a common history recorded in its rocks, its geologic structure and its topographic features --Geography, page 1

Deep circulation within the Argentine Basin

The total transport in the South Atlantic Ocean (Fig. 1) consists of an anticyclonic gyre that reaches from the equator to about 50°S, and south of 40°S two cyclonic turns from the Circumpolar Current and Weddell Sea, west and east of the anticyclonic gyre. This figure has been changed very slightly between 40°S and 50°S from the figure shown in Reid (1994)..