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首页> 外文期刊>Facies >Radiolarian productivity linked to climate conditions during the Pliensbachian-Aalenian in the Kermanshah Basin (West Iran)
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Radiolarian productivity linked to climate conditions during the Pliensbachian-Aalenian in the Kermanshah Basin (West Iran)

机译：Kermanshah盆地（伊朗西部）Pliensbachian-Aalenian时期与气候条件相关的放射虫生产力

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摘要

The 40-m-thick Pliensbachian-Aalenian succession in Kermanshah (Kermanshah Basin; West Iran) includes three main radiolarian-bearing deposits: sponge spicule-radiolarian limestones, cherts, and pyroclastic deposits. Sedimentological and ichnological analyses of these facies reflect the different mechanisms of nutrient supply and proliferation of radiolarians. Pliensbachian p.p.-early Toarcian sponge spicule-radiolarian limestones with low proportions of radiolarians and scarce bioturbation (Chondrites) reflect low radiolarian productivity and accumulation in oxygen-deficient bottom waters. Their deposition was linked to the Pliensbachian-early Toarcian long-term warming, when the greenhouse-warm climate mode led to weak thermohaline circulation, stratified waters, and a well-developed pycnocline. However, a higher proportion of radiolarians is found in intercalated discrete pyroclastic deposits and in limestone beds located on top of coarsegrained internal wave deposits. These pulses of radiolarian productivity are related to an input of nutrients to surface waters due to volcanic eruptions and currents generated by internal waves propagating along the pycnocline. In contrast, middle Toarcian-Aalenian cherts with abundant radiolarians and ubiquitous bioturbation (Thalassinoides) were deposited in oxygenated bottom waters. High radiolarian productivity was related to the long-term middle Toarcian-Aalenian cooling trend and the greenhouse-cool climate. Biosiliceous production was linked to upwelling currents transporting cold deep waters rich in nutrients, which were driven by west-trending monsoon winds.
机译：Kermanshah（Kermanshah盆地;伊朗西部）的40 m厚的Pliensbachian-Aalenian演替包括三个主要的放射l虫矿床：海绵状针radi放射状石灰石，石和热碎屑矿床。这些相的沉积学和鱼类学分析反映了放射虫养分供应和扩散的不同机制。 Pliensbachian p.p.早期的Toarcian海绵针状-radiolarian石灰石的放射虫比例低且生物扰动稀少（Chondrites）反映放射虫的生产力低，并且在缺氧的底水中积累。它们的沉积与普林斯巴赫式-早于Toarcian的长期变暖有关，当时温室温暖的气候模式导致热盐环流薄弱，分层的水域和发达的比诺克林。但是，在层状不连续碎屑碎屑矿床和粗粒内波矿床顶部的石灰岩层中发现了更高比例的放射虫。放射虫生产力的这些脉冲与由于火山喷发和沿火山道传播的内波产生的水流向地表水输入养分有关。相比之下，具有丰富的放射虫和普遍存在的生物扰动（Thalassinoides）的Toarcian-Aalenian中型石沉积在含氧的底水中。放射虫的高生产率与长期中Toarcian-Aalenian降温趋势和温室凉爽气候有关。生物硅质的生产与上升流流动有关，上升流输送着富含营养的冷深水，这些深水是由西风季风推动的。

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