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首页> 外文期刊>Bulletin de la Societe Geologique de France >Radiolarian biostratigraphic constraints for latest Jurassic-earliest cretaceous submarine volcanic activity in the tethyan oceanic realm of the sevan ophiolite (Armenia)
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Radiolarian biostratigraphic constraints for latest Jurassic-earliest cretaceous submarine volcanic activity in the tethyan oceanic realm of the sevan ophiolite (Armenia)

机译：Sevan蛇绿岩（亚美尼亚）的特提斯海洋领域中最新侏罗纪最早的白垩纪海底火山活动的放射虫生物地层学限制

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摘要

Biostratigraphic constraints for the sedimentary cover of the ophiolites preserved in Armenia are of key importance for the palaeogeographic and geodynamic reconstruction of the greater area between Eurasia and the South-Armenian block, which is a micro-continent of Gondwanian origin. We present here radiolarian data obtained from radiolarites that are intercalated in a sequence of mafic volcanic rocks on the northern flank of the Dali valley (east of Lake Sevan), which is considered to be part of the Sevan ophiolite. Mafic sills and dykes with well-preserved igneous textures are probably part of the same sequence. The pseudomorphosis of primary phases indicates that the igneous rocks are strongly affected by alteration in the greenschist faciès condition. The plagiogranites that are present in this locality appear to be intrusive into the mafic sequence. The radiolarian assemblages extracted from radiolarian cherts intercalated in the mafic volcanic rocks are dated as latest Tithonian-Late Valanginian; they contain metric rounded blocks of oolitic limestones with crinoid fragments, suggesting that these shallow water limestones slid during the Jurassic/Cretaceous transition into a rugged oceanic floor in which radiolarian ooze accumulated.
机译：亚美尼亚保存的蛇绿岩沉积盖层的生物地层学限制对于欧亚大陆和南亚美尼亚地块之间的较大区域的古地理和地球动力学重建至关重要，南亚美尼亚地块是冈瓦纳人的微大陆。我们在这里展示从放射虫岩获得的放射虫数据，这些放射虫岩插在大理谷北部侧面（塞凡湖以东）的一系列镁铁质火山岩中，被认为是塞凡蛇绿岩的一部分。具有良好保存的火成质地的基性基岩和堤坝可能是同一序列的一部分。初级相的假变形表明，绿岩岩相条件的变化强烈影响了火成岩。在该位置存在的斜长花岗岩似乎侵入了铁镁铁质层序。从插在镁铁质火山岩中的放射状石提取的放射状体组合是最新的Tithonian-Late Valanginian。它们包含带有卵泡状碎片的公制圆形石灰石块，表明这些浅水石灰石在侏罗纪/白垩纪过渡到崎radio的洋底期间发生了滑动，放射虫的软泥在此积聚​​。

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