Benthic foraminiferal number of specimens in Cretaceous samples of various DSDP and ODP Sites (Table 2)

Benthic foraminifera from 24 DSDP/ODP sites were investigated to assess their global horizontal and vertical distribution in the deep-sea environment at the end of the Cretaceous period. The samples analyzed are from the late Maastrichtian and within the planktic foraminiferal Abathomphus mayaroensis Zone from a wide range of oceans and paleolatitudes, including the low-latitude Sites 10 and 384 (Atlantic Ocean), 47, 171, 305, and 465 (Pacific Ocean), the mid-latitude Sites 20, 111, 356, 363, 516, 525, 527, 548, and 605 (Atlantic Ocean), 216, 217, and 758 (Indian Ocean), and the high-latitude Sites 208 (Pacific Ocean), 689,698,700,738 and 750 (Southern Ocean). Correspondence analysis, based on the 75 most common taxa, shows a clear biogeographic trend along the first correspondence axis by arranging the sites in paleolatitudinal order. The assemblages from the Tethyan Realm (i.e., low latitudes) are marked by abundant heavily calcified buliminids (such as Bulimina incisa, B. trinitatensis, B. velascoensis, and Reussella szajnochae) and Aragonia spp., whereas high-latitude faunas are characterized by abundant Alabamina creta, Gyroidinoides quadratus, and Pullenia coryelli. The results indicate that the faunas at low and high latitudes, respectively, were influenced by quite different environmental conditions. This is based on the much higher abundance of infaunal morphotypes at low and mid latitudes compared to high latitudes, suggesting that the biogeographic trend found in the data set coincides with the trophic regime at the various sites. The results also provide support for the hypothesis that postulates two simultaneous sources and mechanisms for deep-water formation during the Late Cretaceous, including warm, saline deep water produced by evaporation at low (equatorial) latitudes in contrast to the formation of cold deep waters at high (southern) latitudes.本研究对24个深海钻探计划（DSDP）/大洋钻探计划（ODP）钻孔站位的底栖有孔虫（Benthic foraminifera）展开调查，旨在评估白垩纪末期深海环境中底栖有孔虫的全球水平与垂直分布格局。本次分析的样品采集自马斯特里赫特阶晚期，且处于浮游有孔虫（planktic foraminifera）马亚罗阿巴特姆有孔虫（Abathomphus mayaroensis）带地层范围内，涵盖了多大洋与不同古纬度区域：包括低纬度站位10、384（大西洋），47、171、305、465（太平洋）；中纬度站位20、111、356、363、516、525、527、548、605（大西洋），216、217、758（印度洋）；以及高纬度站位208（太平洋），689、698、700、738、750（南大洋）。 基于75个优势分类群开展的对应分析（correspondence analysis）显示，将站位按古纬度顺序排列后，沿第一对应轴可呈现出清晰的生物地理分布趋势。特提斯域（Tethyan Realm，即低纬度区域）的有孔虫组合以丰富的厚壳布利敏有孔虫类群（如Bulimina incisa、B. trinitatensis、B. velascoensis及Reussella szajnochae）和Aragonia属物种为典型特征；而高纬度动物群则以大量产出的Alabamina creta、Gyroidinoides quadratus及Pullenia coryelli为标志性特点。 研究结果表明，低纬度与高纬度区域的底栖动物群分别受到截然不同的环境条件调控。该结论基于如下证据：相较于高纬度区域，低、中纬度区域的内栖形态类群丰度显著更高，这表明本数据集揭示的生物地理趋势与各站位的营养供给状况相匹配。此外，本研究结果还支持晚白垩世存在两种同步存在的深水形成作用机制与来源的假说：即低纬度（赤道区域）通过蒸发作用形成的暖盐水深水，与高纬度（南部区域）形成的冷深水。