One of the major environmental and biotic turnovers of the Phanerozoic occurred at the Cretaceous-Paleogene (K-Pg) boundary, being the focus of countless scientific studies that addressed the timing, causes and consequences of this global event. Paleoenvironmental conditions that preceded the K-Pg boundary, however, have been less studied, especially at low latitudes. In order to help reconstructing late Maastrichtian marine environments along the equatorial South American margin, we apply micropaleontological and geochemical techniques to a stratigraphic core that recovered the Colón Formation in northern Colombia. Low abundance foraminiferal assemblages were overall dominated by benthic taxa (Maastrichtian local biozones Siphogenerinoides bramletti and Ammobaculites colombiana), and the planktonic species Guembelitria cretacea. Ostracod assemblages were mainly composed of the genera Veenia, Cytherella, Paracypris, and Cythereis. Calcareous nannofossils were typical of Upper Cretaceous low-latitude successions, with low abundance and diversity assemblages dominated by Micula staurophora, Kamptnerius magnificus and Cervisiella operculata. Sediment elemental ratios (Zr/Rb, Fe/Ca and Sr/Ba), as well foraminiferal, ostracod and nannofossils assemblages, indicate a shallowing upward trend, characterized by a transition from inner platform settings to sublittoral conditions. Input of terrigenous sediments and weathering intensity also increased upward in the section, probably related to the uplift pulses of the Andean orogeny. Proportions of benthic infauna, as well the V/Cr ratio and the distribution of redox-sensitive trace metals (Ni, Cu) along the core, mostly indicate suboxic bottom water conditions in the Colón Formation.

显生宙的主要环境和生物周转之一发生在白垩纪-古近纪 (K-Pg) 边界，是无数科学研究的焦点，这些科学研究解决了这一全球事件的时间、原因和后果。然而，在 K-Pg 边界之前的古环境条件研究较少，尤其是在低纬度地区。为了帮助重建赤道南美边缘的马斯特里赫特晚期海洋环境，我们将微古生物学和地球化学技术应用于在哥伦比亚北部恢复了科隆组的地层核心。低丰度有孔虫组合总体上以底栖类群为主（马斯特里赫特当地生物区 Siphogenerinoides bramletti和Ammobaculites colombiana) 和浮游物种Guembelitria cretacea 。介形类群主要由Veenia属、Cytherella属、Paracypris属和Cythereis属组成。钙质超微化石是上白垩统低纬度序列的典型特征，以Micula staurophora、Kamptnerius magnificus和Cervisiella operculata为主的低丰度和多样性组合. 沉积物元素比（Zr/Rb、Fe/Ca 和 Sr/Ba），以及有孔虫、介形虫和超微化石组合，显示出逐渐变浅的上升趋势，其特征是从内部平台设置过渡到沿岸条件。该段陆源沉积物输入量和风化强度也向上增加，可能与安第斯造山运动的抬升脉冲有关。底栖动物的比例，以及 V/Cr 比和沿岩心的氧化还原敏感微量金属（Ni、Cu）的分布，主要表明 Colón 组的低氧底水条件。