干旱区生态环境知识资源中心

The climate during the Cretaceous Period represented one of the "greenhouse states" of Earth’s history. Significant transformation of climate patterns and a mass extinction event characterised by the disappearance of dinosaurs occurred across the Cretaceous-Palaeogene boundary. However, most records of this interval are derived from marine sediments. The continuous and well-exposed red strata of the Nanxiong Basin SE China) provide ideal material to develop continental records. Considerable research into strati-graphic, palaeontological, chronologic, palaeoclimatic, and tectonic aspects has been carried out for the Datang profile, which is a type section of a non-marine Cretaceous-Palaeogene stratigraphic division in China. For this study, we reviewed previous work and found that 1) the existing chronological framework of the Datang profile is flawed; 2) precise palaeoclimatic reconstruction is lacking because of the limitations of sampling resolution e.g. carbonate samples) and/or the lack of efficient proxies; and 3) comparisons of climate changes between marine and continental records are lacking. To resolve these problems, detailed field observations and sampling, as well as environmental magnetic and rare earth element REE) measurements, were carried out. The results show that 1) more accurate ages of the Datang profile range from 72 to 62.8 Ma based on a combination of the most recently published radiometric, palaeontological, and palaeomagnetic ages; 2) there is considerable evidence of palaeosol generation, which indicates that the red strata formed in a long-term hot, oxidising environment that lacked underwater conditions; 3) haematite was the dominant magnetic mineral in the red strata, and the variation trend of magnetic susceptibility was consistent with the oxygen isotope records from deep-sea sediments, which indicates that the content of haematite was controlled by the global climate; and 4) the palaeoclimate changes from 72 to 62.8 Ma in the Nanxiong Basin were consistent with global patterns and can be divided into three stages: a relatively hot and wet stage during 72-71.5 Ma, a cool and arid stage during 71.5-66 Ma, and a relatively hot and wet stage again during 66-62.8 Ma with a notable drying and cooling event at 64.7-63.4 Ma. Moreover, there are several sub-fluctuations during each stage. This work provides basic information for further palaeoclimate reconstructions with a higher resolution and longer timescales for the Cretaceous to Palaeocene in the Nanxiong Basin and may even help to test ocean-land climate interactions in the future.