Abstract Clay mineralogical and geochemical analyses (δ18Ocarb, and paired carbonate and organic matter carbon isotope), completed by the characterization of organic matter, have been performed on the Pliensbachian sediments exposed on the Rodiles section (Asturian Basin, Northern Spain). The objectives were to precise the Pliensbachian climate evolution at a relatively low paleolatitude of the Tethyan domain by comparison with previously published high-resolution clay mineralogical and geochemical data from the NW Tethyan domain (e.g. Paris Basin and Cardigan Bay Basin, West Wales). The clay mineral assemblages are dominantly composed of illite and illite-smectite mixed-layers (I–S) associated with minor proportions of chlorite and kaolinite. Smectites are not identified what may result either to their absence at the time of sedimentation or to their progressive illitization due to the burial diagenesis. Rock-Eval data show that organic matter reaching more than 5% in black-shale horizons is thermally mature with Tmax comprised between 444 and 454 °C indicating that the section is in the oil window and that the burial temperature reached or exceeded 80–90 °C. The low δ18Obulk values comprised between −3 and −6‰ clearly results from a diagenetic influence (thermal effect due to burial) but their fluctuations compared with δ18O measured on well-preserved belemnites guards show that the overall trend is however preserved. By comparison with higher latitude sedimentary basins, the most striking feature is the very small proportions of kaolinite (generally less than 5% while the proportions of this mineral reach 40% at higher paleolatitudes), except at the Pliensbachian/Toarcian transition, where the proportion of kaolinite increases significantly. Clay minerals likely originated from the erosion of the Iberian Massif located to the South of the Asturian Basin in a semi-arid climatic belt. This may explain the scarcity of kaolinite by comparison with sedimentary basins located at higher latitude influenced by more humid climate. The increasing proportions of kaolinite by the end of the Pliensbachian suggest southward expansion of the humid belt as a consequence of cooler temperatures and the establishment of steeper latitudinal gradients of temperature likely resulting from the formation of restricted polar ice cap. The main δ13C (on both 13Cinorg and 13Corg) Pliensbachian excursions including the negative excursion of the Sinemurian/Pliensbachian Boundary Event (SPBE) and the Late Pliensbachian positive excursion are well recognized.

中文翻译：

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Rodiles 部分（阿斯图里亚斯盆地，西班牙北部）侏罗纪（Pliensbachian-最下端 Toarcian）沉积物的粘土矿物学、有机质和稳定同位素（C、O）的成岩和环境控制

摘要 通过有机质表征完成的粘土矿物学和地球化学分析（δ18Ocarb，以及成对的碳酸盐和有机质碳同位素）已对 Rodiles 剖面（西班牙北部阿斯图里亚斯盆地）上出露的 Pliensbachian 沉积物进行。目标是通过与先前发布的来自 NW Tethyan 域（例如巴黎盆地和西威尔士的 Cardigan Bay 盆地）的高分辨率粘土矿物学和地球化学数据进行比较，来精确确定特提斯域相对较低古纬度的 Pliensbachian 气候演变。粘土矿物组合主要由伊利石和伊利石-蒙脱石混合层 (I-S) 组成，并伴有少量绿泥石和高岭石。蒙脱石没有被确定是什么原因可能导致它们在沉积时不存在或由于埋藏成岩作用而导致它们的逐渐伊利化。Rock-Eval数据显示，黑页岩层有机质达到5%以上为热成熟，Tmax在444～454℃之间，表明该剖面处于油窗内，埋藏温度达到或超过80～90℃ ℃。δ18Obulk 值介于 -3 和 -6‰ 之间，这显然是由成岩作用（埋藏引起的热效应）造成的，但与在保存完好的箭石护卫上测量的 δ18O 相比，它们的波动表明总体趋势得以保留。与高纬度沉积盆地相比，最显着的特点是高岭石的比例非常小（通常低于 5%，而这种矿物的比例在较高的古纬度地区达到 40%），除了在 Pliensbachian/Toarcian 过渡处，高岭石的比例显着增加。粘土矿物可能起源于位于阿斯图里亚斯盆地南部半干旱气候带的伊比利亚地块的侵蚀。这可能解释了高岭石稀缺的原因，与位于受更潮湿气候影响的高纬度沉积盆地相比。到 Pliensbachian 末期，高岭石比例的增加表明潮湿带向南扩张，这是由于温度变冷和建立更陡峭的纬度梯度的结果，这可能是由于形成受限的极地冰盖造成的。