Being the main oil-bearing basin of Argentina, the Neuquén Basin contains a well-documented stratigraphic record of continental and marine sedimentation during the Jurassic and Cretaceous in the western margin of Gondwana. Marine sedimentation started in the Early Jurassic with the deposition of the offshore to prodelta shales of the Los Molles Formation, the basal unit of the Cuyo Group. A palynological study of outcrop samples of the Los Molles Formation at two localities, Puente Picún Leufú, southern Neuquén Basin, and Cordillera del Viento, central basin area, is presented. The palynological evidence allows inferring two different palaeoceanographic contexts during the deposition of the Los Molles Fm. At Puente Picún Leufú and the lower part of the Cordillera del Viento localities, the record of acritarchs and prasinophytes suggests a stratified water column, suboxic-to-anoxic bottom conditions, and a reduced salinity within the photic zone, associated with a marginal marine environment under restricted oceanic circulation. These conditions would have last at least until the Early Bajocian. Conversely, at the middle and mainly the upper part of Cordillera del Viento locality, the predominance of dinocysts in the assemblages indicates a hydrographically unstable shelf (non-stratified water mass column) with well-oxygenated bottom waters developed under open-marine settings with non-restricted oceanic circulation. The abundance and diversity of dinocyst assemblages are comparable with those observed in the Late Callovian Lotena Formation. These evidences suggest an open oceanic circulation due to the establishment of different seaways in the Neuquén Basin, during the final accumulation of the Los Molles Formation (Early Callovian).

中文翻译：

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基于孢粉学数据，对内乌肯盆地 Los Molles 组（早至中侏罗世）古环境框架的新贡献

作为阿根廷的主要含油盆地，内乌肯盆地在冈瓦纳大陆西部边缘的侏罗纪和白垩纪期间包含有据可查的陆相和海相沉积地层记录。海相沉积始于侏罗纪早期，Los Molles 组的近海至前三角洲页岩沉积，是 Cuyo 组的基础单元。介绍了两个地点（内乌肯盆地南部的 Puente Picún Leufú 和盆地中部地区的 Cordillera del Viento）Los Molles 组露头样品的孢粉学研究。孢粉学证据允许在 Los Molles Fm 沉积期间推断出两种不同的古海洋学背景。在 Puente Picún Leufú 和 Cordillera del Viento 地区的下部，acritarchs 和 prasinophytes 的记录表明分层水柱、低氧到缺氧的底部条件以及光区内盐度降低，这与受限海洋环流下的边缘海洋环境有关。这些条件至少会持续到早期巴约西亚。相反，在 Cordillera del Viento 地区的中部和主要是上部，组合中 dinocysts 的优势表明水文不稳定的陆架（非分层水体柱），在开放海洋环境下开发的底部水体充氧良好，非- 受限制的海洋环流。dinocyst 组合的丰度和多样性与在晚 Callovian Lotena 组中观察到的相当。