نتایج جستجو برای: cretaceous rocks
تعداد نتایج: 30195 فیلتر نتایج به سال:
calcareous nannofossil assemblages recovered from a long, continuous section have been described from the sarayan region in lut block in east iran. the marine upper cretaceous sediments of this section yield medium diverse and well-preserved calcareous nannofossil assemblages. a structural analysis of upper cretaceous calcareous nannofloras has revealed 30 nannofossil species. a revised zonatio...
The Sungun copper porphyry deposit is hosted by a Tertiary magmatic complex in the Azarbayjan province , northwestern Iran. The Sungan mine in its southern and eastern parts is limited by early Miocene volcanic and by Late Cretaceous limestone rocks in northern and eastern parts respectively . The Sungun deposit is associated with a suite of porphyritic granitoids and late dikes intrudi...
The Mississippi Valley Type Pb-Zn ore deposits of northern Semnan could be classified as 1) Eram Series in north-west of Shahmirzad and 2) Shahmirzad Series in south and east of Shahmirzad. The host rocks of these mineralizations are Cretaceous carbonates and fawlts have a major role in controlling hypogene ore formation. Age, mineralogy and structural evidences of both series show a resemblanc...
Subseafloor mixing of reduced hydrothermal fluids with seawater is believed to provide the energy and substrates needed to support deep chemolithoautotrophic life in the hydrated oceanic mantle (i.e., serpentinite). However, geosphere-biosphere interactions in serpentinite-hosted subseafloor mixing zones remain poorly constrained. Here we examine fossil microbial communities and fluid mixing pr...
chaldoran area in nw of iran has mesozoic oceanic crust basement. the studied rocks of this region can be divided into three groups: ophiolitic gabbros and pillow lavas, ophiolitic volcanoclastics and eocene lava flows. ophiolitic mafic rocks show continental volcanic arc natures and eocene lava flow shows oib-like nature. during the mesozoic,the chaldoran region was situated in the active cont...
The classic Neotethyan Ankara Melange formed within the Triassic-Eocene İzmir-Ankara-Erzincan ocean (‘N Neotethys’), bordered in central Anatolia by Kırşehir and Tauride-Anatolide continental units to south discontinuous Sakarya continent northwest. Farther north, separate Intra-Pontide probably remained partly open until early Cenozoic. developed via phases of intra-oceanic accretion (mainly p...
We report the first evidence for a nesting colony of mesozoic birds on Gondwana: a fossil accumulation in Late Cretaceous rocks mapped and collected from within the campus of the National University of Comahue, Neuquén City, Patagonia (Argentina). Here, Cretaceous ornithothoracine birds, almost certainly Enanthiornithes, nested in an arid, shallow basinal environment among sand dunes close to a...
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