华南地区新生代木乃伊化木化石研究进展

Progress on the study of mummified fossil woods from the Cenozoic of South China

中国木化石资源虽然很丰富,但研究程度相比叶片化石要低得多,且主要集中在中国北部和西南地区,研究领域大多局限于分类学方面,而木化石分析与古气候、古生态等领域的交叉和系统研究还很少。大多数情况下木化石的保存方式都为石化或矿化保存,而木乃伊化保存的木化石则非常罕见。木乃伊化保存的化石在植物分类、系统演化及古气候研究等方面具有独特而重要的价值。近年来,本团队在华南地区发现大量木乃伊化保存的新生代木化石,它们分别产自广西南宁盆地晚渐新世邕宁组、广西桂平盆地中新世二子塘组以及广东茂名盆地晚更新世地层中。本文总结了这些木乃伊化保存的木化石的研究进展,包括多样性组成、古植被、古气候及古生态等特征,并对木兰属、蒲桃属和枫香属的植物地理史进行了讨论。综合分析植物群组成特征和木材生长轮以及木化石中具有气候指示意义的解剖结构特征,推测广西南宁盆地晚渐新世时期生长着常绿(少数落叶)阔叶林,为温暖湿润的亚热带季节性气候;广西桂平盆地中新世时期生长着常绿—落叶、阔叶—针叶混交林(阔叶为主),为温暖湿润的亚热带气候;广东茂名盆地晚更新世生长着常绿—落叶、阔叶—针叶混交林,为温暖湿润的亚热带至热带季风气候。这是中国低纬度地区首次系统研究木乃伊化保存的木化石,为新生代植物群的系统演化和古环境分析等提供了重要的木化石依据。

Although fossil woods are abundant in China,they are not as well-studied as fossil leaves.In addition,reports on these fossil woods are mainly focused on specimens from the north and southwest of China and are limited to their taxonomy.Studies on other aspects related to these fossil woods,such as their paleoclimatic and paleoecological implications are relatively rare.In most cases,these fossil woods are petrified or mineralized.Mummified fossil woods are very scarce.These mummified specimens have a unique and important value for the study of their taxonomy,phylogeny,and paleoclimate.Recently,a large number of mummified fossil woods were discovered and collected from the Cenozoic of South China,including the late Oligocene Yongning Formation of the Nanning Basin,and the Miocene Erzitang Formation of the Guiping Basin,Guangxi,and the Late Pleistocene sediments of the Maoming Basin,Guangdong.This paper summarizes the progress on the study of these mummified fossil woods,including the composition,paleovegetation,paleoclimate and paleoecology of the floras,as well as the phytogeographical history of Magnolia L.,Syzygium Gaertn.,and Liquidambar L.Based on the floristic composition of the flora,the growth rings and other anatomical characteristics of the woods,it was suggested that there is an evergreen(with a few deciduous) broad-leaved forest in a warm and humid subtropical seasonal climate during the late Oligocene in Nanning Basin of Guangxi;an evergreen-deciduous,broad-coniferous mixed forest in a warm and humid subtropical climate during the Miocene in the Guiping Basin,and an Guangxi;evergreen-deciduous and broad-coniferous mixed forest in a warm and humid subtropical to tropical monsoon climate in the Late Pleistocene of Maoming Basin,Guangdong.This report represents the first comprehensive study on the mummified fossil woods from low-latitude areas of China.The results,provide an important basis for the study of the evolution of the Cenozoic floras and their paleoenvironments.