An organic geochemical investigation combined with sequence stratigraphy was performed in the Ceará Basin, an offshore basin located in Northeastern Brazil. The information available from 30 well logs (gamma-ray, resistivity, density), besides geochemical (TOC, and pyrolysis indexes) and isotopic (δ¹³C) data, aided the preparation of a dataset for this study. The application of sequence-stratigraphic methods helped classify and correlate seismic and organic facies. Four key petroleum source-rock units were identified, from the oldest to the youngest: (1) Mundaú Formation – top of the Rift Sequence (Berriasian-Aptian); (2) Paracuru Formation – Breakup Sequence (Aptian-Albian); (3) Itapajé Member of the Ubarana Formation – Continental Drift Sequence (Albian-Turonian), and (4) Uruburetama Member of the Ubarana Formation – Continental Drift Sequence (Turonian-Maastrichtian). The geochemical characteristics of the Mundaú Formation (high total organic carbon (TOC), hydrogen index (HI), relative hydrocarbon potential (RHP = (S1 + S2)/TOC)) point to a typical transgressive sequence. Six transgressive-regressive (T-R) cycles were recognized in the entire Paracuru Formation. The best geochemical marker is related to the top of the Paracuru Formation. This stratigraphic unit can be correlated to a major anoxic event and is the best source rock of this basin. Evaporitic facies found in this top section, maximum RHP values (anoxic conditions), and maximum flooding surfaces related to transgressive events characterize this interval. Moreover, the wide spatial cover of organic-rich rocks, carbon isotopic data, and the recognition of favorable characteristics for anoxia in other basins of the Equatorial Margin are suggestive of the Aptian-Albian Oceanic Anoxic Event (OAE-1b) occurring in the Ceará Basin. The Ubarana Formation represented by the Uruburetama Member and the Itapajé Member yields the least promising source rocks. However, high TOC values suggest the occurrence of the late Cenomanian–early Turonian Oceanic Anoxic Event (OAE-2), when organic-rich strata started to deposit in deep-water regions. The predominance of a regressive interval in the Uruburetama Member points to oxic or sub-oxic conditions. Additionally, the correlations between the Brazilian Equatorial Margin and its African counterpart, and the organic geochemical characterization allied to the definition of depositional systems for these regions proved to be useful for oil exploration.

在巴西东北部的近海盆地塞阿拉盆地进行了有机地球化学调查和层序地层学研究。除了地球化学（TOC，和热解索引）和同位素可从30个测井记录（伽马射线，电阻率，密度），所述信息（δ ¹³C）数据，有助于本研究的数据集的准备。层序地层学方法的应用有助于对地震和有机相进行分类和关联。从最老到最年轻，确定了四个关键的石油烃源岩单元：（1）Mundaú组–裂谷序列的顶部（贝里斯-阿普特人）；（2）帕拉库鲁组-分手序列（阿普特－阿尔比亚）；（3）Ubarana编队的Itapajé成员-大陆漂移序列（Albian-Turonian），以及（4）Ubarana编队的Uruburetama成员-大陆漂移序列（Turonian-Maastrichtian）。Mundaú组的地球化学特征（高总有机碳（TOC），氢指数（HI），相对烃势（RHP =（S1 + S2）/ TOC））指向典型的海侵序列。在整个帕拉库鲁组中识别出六个海侵一退（ＴＲ）循环。最好的地球化学标志物与帕拉库鲁组的顶部有关。该地层单元可能与主要的缺氧事件有关，是该盆地最好的烃源岩。在该顶部发现的蒸发相，最大RHP值（缺氧条件）以及与海侵事件有关的最大洪泛面是该间隔的特征。此外，富含有机物的岩石，碳同位素数据的广泛空间覆盖以及对赤道边缘其他盆地缺氧的有利特征的认识表明，塞阿河地区发生了阿普天一阿尔比洋缺氧事件（OAE-1b）。盆地。由Uruburetama成员和Itapajé成员代表的Ubarana地层产生的前景最差的烃源岩。但是，较高的TOC值表明发生了晚切诺曼尼亚–土伦早期海洋缺氧事件（OAE-2），这时富含有机物的地层开始沉积在深水区域。Uruburetama成员的回归间隔占主导地位，表明有氧或亚缺氧状态。此外，事实证明，巴西赤道裕度与非洲赤道裕度之间的相关性，以及与这些地区的沉积系统定义相关的有机地球化学特征，对石油勘探很有用。