英国曼彻斯特大学Lauren K. O’Connor及其课题组取得一项新突破。他们研究出白垩纪-古近纪界线后的最初的30 k.y.里，年平均气温稳步下降。这一研究成果发表在2023年3月22日出版的国际学术期刊《地质学》上。

该课题组人员研究了加拿大萨斯喀彻温省(古北纬约55°)的两个地点的泥炭化石，其中的支链四醚类脂(brGDGT)的分布，生成了一个高分辨率(千年)的年平均气温(MAAT)记录，该记录跨越了白垩纪最后约4 k.y.和古近纪最初的约30 k.y.。研究表明年平均气温的范围在16到29°C之间，在古近纪的第一个千年达到最高值。最早的古近纪平均温度约为25°C—维持或增强了白垩纪晚期的温度—随后在约30 k.y. 中普遍冷却至约20°C。

研究数据中显示，没有明显的边界后突然变冷 (例如，“撞击冬季” ) 或突然变暖，这意味着如果发生这种现象，其持续时间相对较短(即低于千年尺度)。此外，没有明显的长期影响或火山活动导致的变暖。观测到的温度变化范围远远大于同期海洋代用记录得出的温度变化范围。因此，他们的发现更恰当地限定了这段关键时期陆地温度变化的幅度和持续时间，这是非鸟类恐龙灭绝和哺乳动物崛起的主要背景。

据介绍，白垩纪-古近纪(K-Pg)分界线标志着显生宙第五次大规模物种灭绝之一。在不同的时间尺度上，气候系统对火石的撞击和大规模的火山活动的反映方式备受争议。

附：英文原文

Title: Steady decline in mean annual air temperatures in the first 30 k.y. after the Cretaceous-Paleogene boundary

Author: Lauren K. O’Connor, Emily Dearing Crampton-Flood, Rhodri M. Jerrett, Gregory D. Price, B. David A. Naafs, Richard D. Pancost, Paul McCormack, Aris Lempotesis-Davies, Bart E. van Dongen, Sabine K. Lengger

Issue&Volume: 2023-03-22

Abstract: The Cretaceous-Paleogene (K-Pg) boundary marks one of the five major mass extinctions of the Phanerozoic. The ways in which the climate system responded to a bolide impact and extensive volcanism at this time over different time scales are highly debated. We used the distribution of branched tetraether lipids (brGDGT) from fossil peats at two sites in Saskatchewan, Canada (paleolatitude ~55°N), to generate a high-resolution (millennial) record of mean annual air temperature (MAAT) spanning the last ~4 k.y. of the Cretaceous and the first ~30 k.y. of the Paleogene. Our study shows that MAATs ranged from 16 to 29 °C, with the highest value in the first millennia of the Paleogene. The earliest Paleogene averaged ~25 °C—maintaining or enhancing warmth from the latest Cretaceous—followed by a general cooling to ~20 °C over the following ~30 k.y. No abrupt postboundary cooling (e.g., an “impact winter”) or abrupt warming is evident in our data, implying that if such phenomena occurred, their duration was relatively short-lived (i.e., sub-millennial-scale). Further, no long-term impact- or volcanism-driven warming is evident. The range of temperature change observed is considerably greater than that derived from marine proxy records over the same time interval. Our findings therefore more properly place bounds on the magnitude and duration of temperature change on land during this critical interval—the main setting for the demise of nonavian dinosaurs and the rise of mammals.

DOI: 10.1130/G50588.1

Source: https://pubs.geoscienceworld.org/gsa/geology/article-abstract/doi/10.1130/G50588.1/621218/Steady-decline-in-mean-annual-air-temperatures-inredirectedFrom=fulltext