Whole-rock oxygen and carbon isorope record across the Cretaceous/Tertiary boundary in ODP Hole 130-807C

Whole-rock d18O analyses of the Paleogene and Upper Cretaceous succession at Ocean Drilling Program Hole 807C suggest the presence of hiatuses between 876.95 and 894.47 mbsf and between 1138.82 and 1140.94 mbsf. The d13C data show a pronounced positive excursion between 1130 and 1180 mbsf that corresponds to the positive d13C values characteristic of the Paleocene. Despite the stratigraphic breaks in the section, the d18O data show a systematic increase between 1360 mbsf and the hiatus between 876.95 and 894.47 mbsf, which is consistent with previous suggestions of long-term climatic cooling through the Paleogene. The Cretaceous/Tertiary transition is apparently complete in this section and is of remarkable thickness. The expanded nature of this portion of the succession is probably the result of secondary depositional processes. High-resolution sampling across this boundary may reveal detailed structure of the d13C decline associated with the extinctions that mark the termination of the Cretaceous.

针对大洋钻探计划（Ocean Drilling Program, ODP）807C钻孔所揭露的古近系与上白垩统地层序列开展的全岩δ¹⁸O（whole-rock d18O）分析结果表明，在海底以下米数（meters below seafloor, mbsf）876.95至894.47米以及1138.82至1140.94米深度区间存在沉积间断（hiatus）。其δ¹³C（d13C）数据显示，1130至1180米海底以下米数深度区间存在显著的正同位素漂移，该特征与古新世典型的δ¹³C正值特征高度吻合。尽管该地层剖面存在地层间断，δ¹⁸O数据仍呈现出自1360米海底以下米数深度至876.95至894.47米沉积间断区间的系统性升高趋势，这与此前提出的古近纪长期气候变冷假说一致。该剖面中的白垩纪-第三纪界线近乎完整，且厚度可观；这套地层的展宽特征大概率为次生沉积作用改造所致。对该界线开展高分辨率采样，或可揭示与白垩纪末灭绝事件相关的δ¹³C下降的精细结构。