The Cenomanian-Turonian Eagle Ford Formation is a widespread organic-rich mudrock in Texas and northern Mexico. The economic significance of this unit for oil and gas production in USA has led to numerous investigations documenting its lithological and geochemical variability. Comparatively little is known about facies distribution and source rock potential of this unit in Mexico. Here, we studied a section of the Eagle Ford Formation in the central part of the Sabinas basin. In order to evaluate the lateral continuity of the Eagle Ford Formation, and more specifically to gain understanding of the paleoenvironmental drivers of organic matter deposition and the hydrocarbon source source rock potential of this unit, we combined lithological, gamma-ray spectrometric, petrographic and organic geochemical data.

Vertical distribution of main lithologic units and gamma-ray signal of the Eagle Ford Formation of the studied section match those documented in several sites from Texas, with the shale-dominated, bentonite-rich succession of the lower Eagle Ford showing the higher gamma-ray values, and the limestone-dominated succession of the upper Eagle Ford exhibiting moderate-high gamma ray values. Th/K and U/Th ratios suggest that the organic-rich lower Eagle Ford was deposited mainly during a warmer and more humid period, probably related to a sub-humid regional climate phase during the Cenomanian-Turonian global warming event, and under anoxic/dysoxic marine environments. Furthermore, a higher abundance of radiolarians indicates its deposition under nutrient-rich surface water conditions induced by upwelling currents. In contrast, these ratios support a less humid climate and oxic/dysoxic conditions during the accumulation of the upper Eagle Ford. Nevertheless, fluctuations of bottom water oxygen are evidenced by the occurrence of high TOC contents and bioturbated levels. Although TOC values throughout the Eagle Ford Formation point to a poor to very good source rock potential, both equivalent vitrinite reflectance (%VReq) and T_max values indicate that the organic matter is overmature and has an exhausted hydrocarbon generation capability.

Cenomanian-Turonian Eagle Ford地层是得克萨斯州和墨西哥北部普遍存在的富含有机物的泥岩。在美国，该装置对石油和天然气生产的经济意义导致了许多调查研究，证明了其岩性和地球化学变异性。关于该单元在墨西哥的相分布和烃源岩潜力的了解相对较少。在这里，我们研究了Sabinas盆地中部的Eagle Ford组的一部分。为了评估Eagle Ford组的横向连续性，更具体地说，是为了了解有机质沉积的古环境驱动力和该单元的烃源岩势，我们将岩性，伽马射线能谱，岩石学和有机相结合地球化学数据。

研究断面的伊格尔福特组的主要岩性单元的垂直分布和伽马射线信号与得克萨斯州多个地点的记录相符，较低的伊格尔福特的页岩为主，富膨润土的演替显示出较高的伽马射线值，以及鹰礁（Eagle Ford）上部以石灰岩为主的阶跃，表现出中等至较高的伽马射线值。Th / K和U / Th比率表明，富含有机物的较低的Eagle Ford主要在较温暖和潮湿的时期沉积，这可能与Cenomanian-Turonian全球变暖事件中的亚湿润区域气候阶段有关，并且处于缺氧状态。 /缺氧的海洋环境。此外，较高的放射性弧菌表明其在上升流诱发的富含营养的地表水条件下沉积。相比之下，这些比率在上鹰福特（Eagle Ford）的堆积过程中支持了较不潮湿的气候和有氧/低氧条件。然而，高TOC含量和生物扰动水平的出现证明了底部水氧的波动。尽管整个Eagle Ford地层的TOC值都表明烃源岩潜力差到非常好，但等效镜质体反射率（％VReq）和T_最大值表明有机物过早并且具有耗尽的烃生成能力。