(Table 1) Oxygen and carbon isotope data of bulk carbonate and foraminiferal species across the Cretaceous/Tertiary boundary at ODP Site 119-738

In low and middle latitudes, the Cretaceous/Tertiary boundary is marked by a sudden and pronounced decrease in d13C values of near-surface-water carbonates and a reduction in the surface-to-bottom d13C gradient. These isotopic data have been interpreted as evidence of a decline in surface-water productivity that was responsible for the extinction of many planktic foraminiferal species and other marine organisms at or near the K/T boundary. We present planktic and benthic foraminiferal isotopic data from two almost biostratigraphically complete sections at Ocean Drilling Program Site 738 in the antarctic Indian Ocean and at Nye Kløv in Denmark. These data suggest that planktic carbonate d13C values in high latitudes may not have decreased dramatically at the K/T boundary; thus, surface-water productivity may not have been reduced as much as in low and middle latitudes. Comparison of the records of Site 738 with those of ODP Sites 690 and 750 indicates a pronounced decline in d13C values of planktic and benthic foraminifera and fine-fraction/bulk carbonate ~200 000 yr after the K/T boundary. This reflects a regional shift in the carbon isotopic composition of oceanic total dissolved carbon (TDC) and correlates with a similar change in benthic foraminiferal d13C values at mid- and low-latitude Deep Sea Drilling Project Sites 527 and 577. This oceanographic event was followed by the ecosystem's global recovery ~500 000 yr after the K/T boundary. These data suggest that the environmental effects of the K/T boundary may have been less severe in the high-latitude oceans than in tropical and subtropical regions.

在中低纬度区域，白垩纪/第三纪（Cretaceous/Tertiary, K/T）界线以近地表水体碳酸盐的δ¹³C值显著突降，以及表层-底层δ¹³C梯度减小为典型特征。此类同位素数据曾被解读为表层水体生产力下降的佐证，而该生产力下降正是K/T界线前后诸多浮游有孔虫物种及其他海洋生物灭绝的关键诱因。本研究报道了两处近乎完整的生物地层剖面中的浮游与底栖有孔虫同位素数据：一处位于南极印度洋的大洋钻探计划（Ocean Drilling Program, ODP）738站位，另一处为丹麦的尼克洛夫（Nye Kløv）剖面。上述数据表明，高纬度海域的浮游碳酸盐δ¹³C值在K/T界线处或许并未出现大幅下降，因此其表层水体生产力的降低幅度可能不及中低纬度区域。将738站位的记录与ODP 690、750站位的记录进行对比后发现，在K/T界线之后约20万年，浮游与底栖有孔虫以及细粒组分/全岩碳酸盐的δ¹³C值均出现显著下降。这一现象反映了海洋总溶解碳（total dissolved carbon, TDC）碳同位素组成的区域性偏移，且与中低纬度深海钻探计划（Deep Sea Drilling Project, DSDP）527、577站位的底栖有孔虫δ¹³C值变化呈现显著相关性。此次海洋学事件之后，全球海洋生态系统在K/T界线之后约50万年迎来全面恢复。上述数据表明，K/T界线事件对高纬度海洋的环境影响程度，或许弱于热带与亚热带区域。