The State of Silurian
نویسنده
چکیده
The geological sciences demand close international cooperation as wel as a rigorous and clearly understood language of words. Nowhere is this more keenly felt than in stratigraphy where, despite the luxury of long philosophical discussions on rocks versus time, many feel a sense of urgency about attempts to achieve a standard global chronostratigraphy. The now wel-known pioneer work of the international committee on the Sil uri an -Devonian Boundary took 12 years to complete, though ntinns about this this was a pioneering exercise. level were also found to have been
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Early Silurian (Llandovery) Trilobite fauna from
The aim of this study is to analyze the assemblage of trilobites in the Silurian sequences of Iran by exploring stratigraphic section of the Silurian Niur Formation (Asadli section). Based on comprehensive field studies and laboratory investigations three Trilobite genera were identified in the study area including Calymene blumenbachii, Gravicalymene convolva, Dalmanites brevigladiolus </...
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The upper part of Shirgesht (UPS) and lower part of Niur (LPN) formations (Ordovician-Silurian) consist of sandstone, shale and limestone, respectively. The petrography and geochemical analysis conducted to evaluate provenance of siliciclastic deposits in order to understand the paleogeography of Central Iran during the Early Paleozoic time. This study shows that quartz and K-feldspar are the m...
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This area is located in Derenjal Mountains, 60Km northwest of Tabas in central Iranian structural zone. The igneous rocks occur as plutonic with composition of olivine-gabbro, gabbro, diorite and monzodiorite in Kalshaneh Formation with Middle Cambrian age and as the extrusive rocks with composition of olivine basaltic lavas in lower part of Niur Formation with Silurian age. Petrographical and ...
متن کاملLand animals in the silurian: arachnids and myriapods from shropshire, England.
A new assemblage of arthropod cuticles from Upper Silurian rocks in Shropshire, England, includes at least two centipedes and a trigonotarbid arachnid. This unequivocal terrestrial fauna from the Silurian constitutes the earliest direct record of land animals. The presence of predatory arthropods suggests that complex terrestrial ecosystems were in place by the late Silurian (414 x 10(6) years ...
متن کاملState of Michigan Department of Conservation Gerald E. Eddy, Director Geological Survey Division William L. Daoust, State Geologist Information on Michigan Silurian Oil and Gas Pools
Michigan's first commercial oil field was discovered at Port Huron, St. Clair County, in 1886. By 1910, 21 shallow wells had been completed in the Dundee formation at depths of about 500 to 650 feet. In 1910 the daily production from this field amounted to about 10 barrels of oil per day, all of which was used locally in the manufacture of lubricants. However, it was not until 1925 when the Sag...
متن کاملCharacteristics of tectono-magmatic alkali gabbros in northern Fathabad, Zarand (NW Kerman): based on the pyroxene mineral chemistry
Fathabad area is located in northwest of the city of Zarand (Kerman province) in the Posht-e-Badam block of the central Iran structural zone. The Ordovician–Silurian gabbroic stocks have intruded into volcanic-sedimentary rocks of the Rizu series. The gabbros are mainly composed of clinopyroxene, kaersutite, plagioclase and biotite. Electron microprobe analyses demonstrate that the clinopyroxen...
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