(Table T1) Stable oxygen and carbon isotopes of bulk carbonate from ODP Leg 207 sites

Stable isotopic values of 174 upper Campanian and Maastrichtian bulk carbonate samples from Demerara Rise, in the western tropical Atlantic (Ocean Drilling Program Leg 207, Sites 1257-1261), largely fall between 0 per mil and 2 per mil for d13C and between -2 per mil and -3 per mil for d18O. The relatively low values and high scatter of d13C values observed suggest secondary calcite with a remineralized organic carbon component was present in most to all samples analyzed. Oxygen isotopic data exhibit less scatter and values closer to those expected for contemporary sea-surface conditions than do carbon data. However, trends in d18O data at any one section do not correlate among sites using shipboard age estimates. Regardless of whether subsequent age estimates modify correlation among holes, diagenetic concerns will remain a significant complication in any efforts to study isotopic trends during the late Campanian-Maastrichtian at these sites.本数据集涵盖取自热带大西洋西部德梅拉拉海隆（大洋钻探计划第207航次，站位1257至1261）的174件上坎潘期与马斯特里赫特期块状碳酸盐样品的稳定同位素数据。其中d13C值大多介于0‰至2‰之间，d18O值则集中于-2‰至-3‰区间。观测到的d13C值相对偏低且离散度较高，表明本次分析的绝大多数乃至全部样品中均含有携带再矿化有机碳组分的次生方解石。相较于碳同位素数据，氧同位素数据的离散度更低，且其数值更接近现代海表环境的理论预期值。但基于任一剖面的d18O数据所呈现的变化趋势，无法通过船上年龄估算结果实现站位间的对比。无论后续的年龄修正是否能改善钻孔间的相关性，在研究该区域晚坎潘期-马斯特里赫特期的同位素变化趋势时，成岩作用带来的干扰都将是一项难以规避的重要难题。