This study presents an integrated investigation of the Upper Triassic Potrerillos – Cacheuta lacustrine source rock in the Cuyo Basin of western Argentina. Data came from palynofacies analyses, organic petrography, Rock-Eval pyrolysis and mineralogical studies based on X-ray diffraction analyses. An 80 m thick outcrop section was studied and is interpreted to represent the transition from shallow-lacustrine sediments influenced by fluvial discharges (uppermost Potrerillos Formation) to the deposits of a deep, permanent lake (Cacheuta Formation). Three palynofacies were defined. Palynofacies I is characterized by shallowing-upward cycles with abundant woody material, and was deposited under an oxic, disturbed water column. Palynofacies II and III occur in laminated shales rich in amorphous organic matter (AOM) and freshwater algal material (Botryococcus) respectively, which were deposited under oxygen-depleted conditions. In general, the detrital material present suggests an input derived from fluvial discharges; however, interbedded tuffs altered to analcime and smectite suggest the transformation of vitric material in pyroclastic ash under saline to alkaline water conditions. Kerogen Types II/III and III with high total organic carbon values indicate a moderate oil- and gas-prone source rock whose thermal maturity varies from immature to the early oil window (T_max: 430-438 °C; vitrinite reflectance: 0.59-0.67 % VR_o; and thermal alteration index: 2-2⁺).

中文翻译：

---

湖相烃源岩粉相和有机地球化学：阿根廷中西部三叠纪库约盆地的 POTRERILLOS – CACHEUTA 烃源岩系统

本研究对阿根廷西部库约盆地上三叠统 Potrerillos – Cacheuta 湖相烃源岩进行了综合调查。数据来自孢粉相分析、有机岩相学、岩石评估热解和基于 X 射线衍射分析的矿物学研究。对 80 m 厚的露头部分进行了研究，并解释为代表受河流排放影响的浅湖沉积物（最上面的 Potrerillos 地层）到深层永久湖泊（Cacheuta 地层）沉积物的过渡。定义了三个孢粉相。孢粉相 I 的特点是浅层向上旋回，含有丰富的木质物质，并沉积在含氧、受干扰的水柱下。孢粉相 II 和 III 分别发生在富含无定形有机质 (AOM) 和淡水藻类物质 (Botryococcus) 的层状页岩中，这些页岩是在贫氧条件下沉积的。一般来说，存在的碎屑物质表明来自河流排放的输入；然而，互层凝灰岩转变为方沸石和蒙脱石，表明火山碎屑灰中的玻璃质物质在盐水条件下转变为碱性水条件。干酪根类型 II/III 和 III 具有较高的总有机碳值，表明其热成熟度从未成熟到早期石油窗口变化（_最高温度：430-438 °C；镜质体反射率：0.59-）。 0.67 % VR _o；热蚀变指数：2-2 ⁺ )。