南方红土磁性地层年代学研究进展

Magnetostratigraphy of the red soil sequences in southern China:Recent developments.

南方红土是中国分布最广的第四纪土状堆积,蕴含丰富的古气候、古地理以及古人类演化的信息。然而,南方红土地区长期高温多雨的气候造成许多定年材料的缺乏,导致其年代学研究进展比较缓慢。磁性地层学方法是一种适合于中、新生代海陆相沉积物定年的快捷、有效的方法,近年来南方红土的磁性地层年代学研究取得了很好的结果。文中比较系统地总结了近年来南方红土磁性地层年代学研究方面的进展。这些研究显示南方红土中的载磁矿物包括赤铁矿、磁赤铁矿、磁铁矿和针铁矿,其中磁铁矿和赤铁矿是特征剩磁的主要载体。磁性地层结果表明南方红土记录了Matuyama负极性时晚期至Brunhes正极性时早—中期的沉积,其沉积起始年龄不晚于Jaramillo正极性亚时,即早于1.1 Ma。这些磁性地层学结果为揭示南方红土记录的环境变化和中国南方亚热带地区早期人类演化提供了年代学基础。

The red soil is the most widely distributed Quaternary deposit in China,which contains a wealth of information on paleoclimate,paleogeography,and hominin evolution.However,because of the climatic conditions of high precipitation and warm temperature,which reduce the preservation of mammalian fossils and other dating materials,it is difficult to obtain precise stratigraphic ages in the red soil area.Magnetostratigraphy is a successful tool for dating both marine and terrestrial sediments.A series of magnetostratigraphic studies has been successfully conducted on the red soil sequences.This paper reviews magnetostratigraphic studies of the red soil sequences in southern China,some of which bear artifact stone tools.The red soils contain four magnetic minerals of goethite,maghemite,magnetite and hematite.Magnetite and hematite were identified as the main carriers of the characteristic remnant magnetizations.Paleomagnetic findings suggest that the red soil sequences in southern China span a period from the late Matuyama reverse chron to the early-middle Brunhes normal chron,and that the sequences began to accumulate no later than the Jaramillo age（that is,ca.1.1 Ma）.The magnetostratigraphies have significantly refined the chronology of the terrestrial red soil sequences in subtropical southern China,thus providing a robust chronological framework for deciphering Quaternary paleoenvironmental processes and probing early human evolution in subtropical eastern Old World.