Abstract A Wenlock (Silurian) sedimentary continuous sequence was sampled in the Dornes region (Central Iberian Zone, Portugal) to characterize the organic matter type using different microscopic analyses (organic petrology and palynofacies). Total organic carbon (TOC) was also determined. Samples are part of Foz da Serta Formation and correspond to mudstone, punctually with sandstone, rich in organic matter (mean TOC value of 5.1%). Whole rock samples showed a dominance of non-granular graptolites (lath- and blocky-shape) and solid bitumen. Lath-shape graptolites display the characteristic segmented structure. In the blocky-shape graptolites, the fusellar layers of the graptolite wall are well marked and are an important distinctive feature. Foz da Serta graptolites are optically anisotropic as well as the solid bitumen. Non-granular graptolite's maximum reflectance varies from 1.43 to 3.94% and solid bitumen maximum reflectance oscillates between 1.09 and 2.22%. Vitrinite reflectance equivalent was calculated using Bertrand and Malo's equation (values between 1.97 and 3.72%) denoting a post-mature stage for the organic matter. No relation was established with confidence between graptolite maximum reflectance and solid bitumen maximum reflectance. The palynofacies study confirmed not only the presence of graptolite and solid bitumen but also amorphous material derived from graptolite. Under transmitted white light, graptolite features were not noticed. To improve the palynofacies characterization, reflected white light was used on slides, thus exposing distinctive graptolite features. The different lights and preparation types used allowed a better characterization of the organic matter present in Foz da Serta Formation samples, mainly the graptolites. The use of reflected white light, in the palynofacies study, proved to be extremely important in the description of the graptolite features.

中文翻译：

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多恩地区志留纪层序研究（葡萄牙中部伊比利亚地区）：有机岩石学和孢粉相的贡献

摘要 在多恩地区（葡萄牙伊比利亚中部）对文洛克（志留纪）沉积连续层序进行采样，以使用不同的显微分析（有机岩石学和孢粉相）表征有机质类型。还测定了总有机碳 (TOC)。样品是 Foz da Serta 组的一部分，对应于泥岩，准时含有砂岩，富含有机质（平均 TOC 值为 5.1%）。全岩样品显示出以非粒状笔石（板条状和块状）和固体沥青为主。板条状笔石表现出特有的分段结构。在块状笔石中，笔石壁的胞体层明显地被标记，是一个重要的显着特征。Foz da Serta 笔石与固体沥青一样具有光学各向异性。非颗粒笔石的最大反射率在 1.43% 到 3.94% 之间变化，固体沥青最大反射率在 1.09% 和 2.22% 之间波动。使用 Bertrand 和 Malo 方程（值介于 1.97 和 3.72% 之间）计算镜质体反射当量，表示有机物质的后成熟阶段。笔石最大反射率和固体沥青最大反射率之间没有可信的关系。孢粉相研究不仅证实了笔石和固体沥青的存在，而且还证实了笔石衍生的无定形材料。在透射白光下，未注意到笔石特征。为了改善孢粉相特征，在载玻片上使用反射白光，从而暴露出独特的笔石特征。使用的不同光线和制备类型可以更好地表征 Foz da Serta 地层样品中存在的有机物质，主要是笔石。在孢粉相研究中，反射白光的使用被证明在描述笔石特征方面极为重要。