地理学报

地理学报 ›› 2019, Vol. 74 ›› Issue (11): 2371-2384.doi: 10.11821/dlxb201911013

• 气候变化与生态环境 • 上一篇    下一篇

青海喇家遗址土壤序列及史前山洪泥流灾难释光测年研究

炊郁达1,黄春长1(),庞奖励1,周亚利1,张玉柱2,郭永强3,王海燕1,赵琪琪1   

  1. 1. 陕西师范大学地理科学与旅游学院,西安 710062
    2. 西北大学城市与环境学院,西安 710127
    3. 中国科学院、水利部成都山地灾害与环境研究所,成都 610041
  • 收稿日期:2018-12-20 修回日期:2019-07-01 出版日期:2019-11-25 发布日期:2019-11-01
  • 作者简介:炊郁达(1993-), 男, 陕西宝鸡人, 硕士生, 主要从事土地利用与全球变化研究。E-mail: cuanyuda@snnu.edu.cn
  • 基金资助:
    国家自然科学基金项目(41771110);国家自然科学基金项目(41801060);国家重点研发计划(2017YFC1502501);陕西省教育厅专项科研计划(17JK0770)

OSL dating of the pedo-stratigraphic sequence and the prehistoric flash floods and mudflows over the Lajia Ruins of Qinghai Province

CUAN Yuda1,HUANG Chunchang1(),PANG Jiangli1,ZHOU Yali1,ZHANG Yuzhu2,GUO Yongqiang3,WANG Haiyan1,ZHAO Qiqi1   

  1. 1. School of Geography and Tourism, Shaanxi Normal University, Xi'an 710062, China
    2. College of Urban and Environmental Science, Northwest University, Xi'an 710127, China
    3. Institute of Mountain Hazards and Environment, Chinese Academy of Sciences, Chengdu 610041, China
  • Received:2018-12-20 Revised:2019-07-01 Published:2019-11-25 Online:2019-11-01
  • Supported by:
    National Natural Science Foundation of China(41771110);National Natural Science Foundation of China(41801060);National Key R&D Program of China(2017YFC1502501);Special Research Project of Education Department of Shaanxi Provincial Government(17JK0770)

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摘要：

位于青藏高原东北部边缘的青海民和官亭盆地喇家遗址,保存着全新世环境变化、人类活动、复杂地表过程演变与突发性灾难事件的记录。关于其史前群发性灾难的成因及发生年代问题,争议颇多,受到国内外学术界和媒体的广泛关注。经过多年来深入彻底的调查研究,在上喇家村南侧、喇家遗址北部区域首次发现完整连续的晚更新世晚期以来黄土—土壤地层剖面。在详尽的土壤与沉积学观察和层次关系分析的基础上,系统性采集样品,进行了光释光测年。由此在黄河第二级阶地风成黄土与黑垆土类土壤为主的区域,建立起了喇家遗址土壤沉积物地层序列与年代框架。结果表明,该剖面从12000 a BP堆积发育至今,从下至上的层序为晚更新世马兰黄土顶部（L1-1）、全新世早期过渡性黄土（Lt）、全新世中期古土壤（S0）、近代黄土（L0）与现代土壤层（MS）。其中在全新世中期古土壤黑垆土层（S0）之内,OSL年龄3960-3650 a BP期间,发现有3层红色粘土质泥流沉积层插入,记录了3次大规模山洪泥流溢出沟槽、在平坦的阶地表面扩散沉积、掩埋齐家文化聚落而成灾的事件。综合多种断代方法结果,确定这3期山洪泥流灾难性事件分别发生在3850 a BP、3800 a BP、3600 a BP左右。其中第一场山洪泥流在阶地表面大范围扩散过程当中,覆盖了喇家遗址东部区域。这就充分表明,来自于官亭盆地北部第三系红层丘陵沟壑区的暴雨山洪泥流过程,与同时期发生的若干次大地震,共同毁灭了喇家遗址齐家文化聚落的东部区域。这些研究成果,对于深入探讨官亭盆地环境变化与人地关系演变规律、准确理解喇家遗址的形成、史前人类活动、突发性灾难及其毁灭过程问题,具有重要的科学意义。

关键词: 喇家遗址, 史前灾难, 泥流事件, 地层序列, 释光测年

Abstract:

Environmental change and human-land relationship evolution over the Qinghai-Tibet Plateau are the frontiers of global change science. The Lajia Ruins in the Guanting Basin situated in the northeast margin of the Qinghai-Tibet Plateau has preserved many records of the Holocene environmental change, human activities, complex surface process evolution and abrupt catastrophic events. Therefore, the Lajia Ruins has received extensive attention from scientists from different fields, and has also attracted attention from world media. It is still quite controversial about the causation and age of the prehistoric catastrophe. After extensive field works over the years, a complete pedo-stratigraphy profile of soil and sediments has been found in the northern part of the Lajia Ruins. On the basis of field pedo-sedimentological observation and description, as well as physic-chemical analysis and OSL dating on the soil and sediment samples taken from the profile, a pedo-stratigraphic sequence and related chronology have been established in the Lajia Ruins. The results show that the profile has been developed from 12000 a BP. The pedo-stratigraphic sequence includes the Late Pleistocene Malan loess (L1-1), Holocene transitional loess (Lt), the Middle Holocene palaeosol (S0), the recent loess (L0) and the modern topsoil (MS). The Middle Holocene palaeosol (S0) is separated by three layers of red clay, which were deposited by large flash floods and mudflows during 3960-3650 a BP. These catastrophic events occurred at about 3850 a BP, 3800 a BP and 3600 a BP, respectively. The first mudflow event overflowed the gully channel and spread over a large area on the Yellow River terrace, and covered the eastern part of the large settlement of the Qijia Culture at 3850 a BP. All these facts indicate that the Lajia Ruins was destroyed by earthquakes in combination with large flash floods and mudflows coming along the gullies that originated from the hills of the Tertiary Red Formation. These results are very important in understanding environmental change and human-land relationship evolution, formation of the settlement of the Qijia Culture, pre-historical human impact and causation of catastrophe in the Guanting Basin.

Key words: Lajia Ruins, prehistoric catastrophe, mudflow event, stratigraphic sequence, OSL dating