Since 2012, we have investigated a stratigraphic section encompassing the late Eocene–earliest Oligocene interval at Shapaja (Tarapoto area, Peruvian Amazonia, ca. 7°S), through paleontological and geological fieldwork. The measured sedimentary series (120 m-thick [West] plus 90 m-thick [East]), assigned to the upper member of the Pozo Formation, records fluvial micro-conglomeratic lenses intercalated with floodplain and evaporite-rich fine red deposits, estuarine/coastal-plain tidally-influenced fine sandstones, and oxbow lake nodule-rich blue clays. This sedimentary shift coincides locally with the demise of the large Eocene coastal-plain wetland known as Pozo System. The late Eocene–early Oligocene Shapaja section was extensively sampled for chemostratigraphy (δ¹³C on dispersed organic matter and pedogenic carbonate nodules), which in turn allowed for refining the location of the Eocene-Oligocene Transition (EOT) and other climatic events recognized at a global scale (i.e., Oi-1 and Oi-1a). The section has yielded nine fossil localities with plant remains (leaves, wood, charophytes, and palynomorphs), mollusks, decapods, and/or vertebrates (selachians, actinopterygians, lungfishes, amphibians, sauropsids, and mammals), documenting ~130 distinct taxa. Four localities of the upper member of the Pozo Formation at Shapaja predate the EOT, one is clearly within the EOT, while four are earliest/early Oligocene in age. The small leaf impressions found along the Shapaja section could be indicative of dry and/or seasonal conditions for this region throughout and after the EOT. Monkeys, indicative of tropical rainforest environments, are only recorded in a latest Eocene locality (TAR-21). Two biotic turnovers are perceptible in the selachian, metatherian, and rodent communities, well before the EOT [~35–36 Ma] and a few hundred thousand years after the EOT [~33 Ma]. The latter turnover seems to be primarily related to a global sea-level drop (ichthyofauna: marine-littoral elements replaced by obligate freshwater taxa) and/or the onset of a drier and more seasonal climate in early Oligocene times (terrestrial components). Changes in the structure of the Shapaja paleocommunities were mostly driven by the flexural subsidence during the late Eocene, and then globally driven by the earliest Oligocene climatic deterioration.

自2012年以来，我们通过古生物学和地质野外调查研究了Shapaja（塔拉波托地区，秘鲁亚马逊河，约7°S）晚始新世至最早的渐新世的地层。分配给Pozo组上部的测得的沉积系列（西120m厚，东90m厚）记录了河流微砾岩晶状体，这些晶状体中夹有泛洪平原和富含蒸发岩的细红色沉积物，河口/沿海平原受潮汐影响的细砂岩和牛弓湖结节丰富的蓝色粘土。这种沉积位移与大面积始新世沿海平原湿地被称为Pozo系统的消亡相吻合。在晚始新世，渐新世早期Shapaja部分被广泛用于化学地层取样（δ ¹³C代表分散的有机物和成岩的碳酸盐结节），这反过来又有助于完善始新世-渐新世过渡带（EOT）的位置以及在全球范围内公认的其他气候事件（即Oi-1和Oi-1a）。该部分已产生9个化石产地，其中有植物残骸（叶子，木材，生叶植物和古生物），软体动物，十足纲动物和/或脊椎动物（石斑鱼，放线翅目动物，肺鱼，两栖动物，蜥脚类动物和哺乳动物），记录了约130种不同的分类单元。Shapaja的Pozo地层上部成员的四个位置早于EOT，其中一个显然位于EOT内，而四个则是最早/早期的渐新世。沿Shapaja断面发现的小叶片痕迹可能表明该区域在整个EOT期间和之后都处于干燥和/或季节性条件。猴子 指示热带雨林环境的记录仅记录在最新的始新世地区（TAR-21）中。在塞拉奇人，海龟人和啮齿动物群落中，可以感知到两种生物更新，分别是在EOT之前[〜35-36 Ma]和EOT之后的几十万年[〜33 Ma]。后者的营业额似乎主要与全球海平面下降有关（鱼鳞鱼：海洋沿海的元素被专性淡水生物分类所替代）和/或在渐新世早期（地面成分）开始出现干燥和更多的季节性气候。Shapaja古群落的结构变化主要由始新世晚期的弯曲沉降驱动，然后在全球范围内由最早的渐新世气候恶化驱动。在塞拉奇人，海龟人和啮齿动物群落中，可以感知到两种生物更新，分别是在EOT之前[〜35-36 Ma]和EOT之后的几十万年[〜33 Ma]。后者的周转量似乎主要与全球海平面下降（鱼鳞鱼类：海洋沿岸要素被专性淡水生物分类所替代）和/或渐新世早期（地面成分）更干燥，季节性气候增多有关。Shapaja古群落的结构变化主要由始新世晚期的弯曲沉降驱动，然后在全球范围内由最早的渐新世气候恶化驱动。在塞拉奇人，海龟人和啮齿动物群落中，可以感知到两种生物更新，分别是在EOT之前[〜35-36 Ma]和EOT之后的几十万年[〜33 Ma]。后者的周转量似乎主要与全球海平面下降（鱼鳞鱼类：海洋沿岸要素被专性淡水生物分类所替代）和/或渐新世早期（地面成分）更干燥，季节性气候增多有关。Shapaja古群落的结构变化主要由始新世晚期的弯曲沉降驱动，然后在全球范围内由最早的渐新世气候恶化驱动。后者的周转量似乎主要与全球海平面下降（鱼鳞鱼类：海洋沿岸要素被专性淡水生物分类所替代）和/或渐新世早期（地面成分）更干燥，季节性气候增多有关。Shapaja古群落的结构变化主要由始新世晚期的弯曲沉降驱动，然后在全球范围内由最早的渐新世气候恶化驱动。后者的营业额似乎主要与全球海平面下降有关（鱼鳞鱼：海洋沿海的元素被专性淡水生物分类所替代）和/或在渐新世早期（地面成分）开始出现干燥和更多的季节性气候。Shapaja古群落的结构变化主要由始新世晚期的弯曲沉降驱动，然后在全球范围内由最早的渐新世气候恶化驱动。