Abstract Detailed palynologic and lithostratigraphic studies of outcrop sections on the western flank of the Merida Andes in Western Venezuela were undertaken to establish a framework for interpreting and correlating regional and local unconformities from the outcrop to subsurface data. The Upper Cretaceous to lower Paleogene section of the Maracaibo Basin consists of laterally continuous rock units attributed to the Mito Juan and Barco/Catatumbo formations, which are characterized by marine sediments deposited relatively close to shore. The continuity of plant and dinoflagellate species across the Cretaceous-Paleogene boundary in this area may have potential significance to K/Pg studies elsewhere. The lower to upper Paleogene Los Cuervos, Mirador, and Carbonera formations were predominantly deposited in non-marine environments, though palynologic and stratigraphic data from each unit show the variable influence of marine and lacustrine conditions. A new chronostratigraphic framework for the study area (the “Venezuelan Composite Standard”) was developed based on first and last appearances of spores, pollen, and dinoflagellates, and three pollen acme events and calibrated to the latest time scale. Graphic correlation plots of the most complete outcrop sections at Rio Lobaterita, Rio Lora, and Rio Chama indicate the presence of significant hiatuses in time, due to erosion and non-deposition (or a combination of the two) reflecting the complex structural and depositional history of the southeastern Maracaibo Basin. A regionally significant upper Paleocene to lower Eocene unconformity, as well as several local and regional intra middle Eocene unconformities appear to have been caused by a drop in base level (sea level plus structural uplift) forming incised valleys over much of the study area. Unconformities are also present in the upper middle Eocene to Oligocene and represent ravinement surfaces caused by transgressive marine reworking of pre-existing units. These surfaces are often marked by the presence of dinoflagellates within the upper Eocene Carbonera Formation. Depositional environments during much of the Upper Cretaceous to Paleogene succession vary from fluvial-floodplain to marginal marine, with newly noted periods of widespread lacustrine deposition in all geologic units. Temporal differences between similar Paleogene lithostratigraphic units in northeastern Colombia and southwestern Venezuela are likely due to the influence and timing of structural events on regional and local depositional environments.

中文翻译：

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委内瑞拉西部梅里达安第斯山脉（马拉开波盆地）上白垩统和古近系露头剖面的孢粉地层学和岩石地层学

摘要 对委内瑞拉西部梅里达安第斯山脉西侧露头剖面进行了详细的孢粉学和岩石地层学研究，以建立一个框架，用于解释和关联从露头到地下数据的区域和局部不整合面。Maracaibo 盆地上白垩纪至下古近系部分由横向连续的岩石单元组成，这些岩石单元归因于 Mito Juan 和 Barco/Catatumbo 地层，其特征是沉积在相对靠近海岸的海相沉积物中。该地区白垩纪-古近纪边界上植物和鞭毛藻物种的连续性可能对其他地方的 K/Pg 研究具有潜在意义。从下到上古近纪 Los Cuervos、Mirador 和 Carbonera 地层主要沉积在非海洋环境中，虽然来自每个单元的孢粉学和地层数据显示了海洋和湖泊条件的可变影响。研究区的新年代地层框架（“委内瑞拉综合标准”）是根据孢子、花粉和鞭毛藻的首次和最后一次出现以及三个花粉顶点事件开发的，并校准到最新的时间尺度。Rio Lobaterita、Rio Lora 和 Rio Chama 最完整的露头剖面的图形相关图表明，由于侵蚀和非沉积（或两者的组合），反映了复杂的构造和沉积历史，因此存在明显的时间中断马拉开波盆地东南部。具有区域意义的上古新世至下始新世不整合面，以及几个局部和区域中始新世内不整合面似乎是由基准面下降（海平面加上构造隆起）在大部分研究区域形成下切山谷引起的。不整合也存在于中始新世至渐新世中，代表了由海侵海洋改造预先存在的单元造成的沟壑表面。这些表面通常以上始新世 Carbonera 地层中甲藻的存在为标志。上白垩纪到古近纪序列的大部分沉积环境从河流泛滥平原到边缘海相各不相同，所有地质单元都有新发现的广泛湖泊沉积时期。