黄土高原东缘晚全新世高精度高分辨率石笋古环境记录
作者简介:董进国(1978-),男,山西阳高人,讲师,博士研究生,主要从事第四纪年代学与环境演变研究。E-mail:dongjinguo1111@163.com
收稿日期: 2011-11-15
要求修回日期: 2012-02-09
网络出版日期: 2012-09-20
基金资助
国家自然科学基金项目(41102216、41002061)、HISPEC研究课题(NSC 100-2116-M-002-009)资助
An Absolute-dated High-resolution Palaeoclimate Record Between 4 400 and 150 a B.P. from Dragon Cave, Eastern Loess Plateau, China
Received date: 2011-11-15
Request revised date: 2012-02-09
Online published: 2012-09-20
Copyright
董进国 , 沈川洲 , 姜修洋 . 黄土高原东缘晚全新世高精度高分辨率石笋古环境记录[J]. 地理科学, 2012 , 32(9) : 1136 -1141 . DOI: 10.13249/j.cnki.sgs.2012.09.1136
The Dragon Cave (38°46´N, 113°16´E) is located at transition between semi-humid and semi-arid areas in the middle temperature zone of China. Here, mean annual temperature is 8ºC. Mean annual rainfall is 530mm and about 87% of annual precipitation falls in May-October. Dragon Cave is >600m long with an elevation of 1400m on the western slope of Taihang Mountain, near the eastern edge of Chinese Loess Plateau. Stalagmite L1 was collected 200m from the cave entrance in December 2010. It is about 200mm like a candle. A total of 5 sub-samples were measured by an inductively Multi-collection coupled plasma mass spectrometry on a Finnigan-NEPTUNE in the High-precision Mass Spectrometry and Environment Chang Laboratory, Department of Geosciences, National Taiwan University. The uncertainty of reported age is ± 2σ. A high-resolution oxygen isotope profile established with 190 oxygen isotope data, provides a continuous history of East Asian summer monsoon intensity for the period of 4400-150a B.P. (before AD1950). With a relatively stable boundary condition, we interpret the δ18O of speleothem calcite as most indicative of the amount of summer monsoon precipitation, although temperature and other factors might have some minor impact. Comparison of the record with previous published contemporaneous China stalagmite records shows that all δ18O records, characterized with increasing δ18O and declining summer monsoon precipitation trends over the late Holocene, generally follow insolation changes on millennial timescale. This long-term agreement supports that the solar insolation is the primary factor driving Asian summer monsoon. An unusual abrupt weak summer monsoon at 2550-2000a B.P. indicates a mega-drought event, supported by historic archives. The spectral analysis of δ18O time series yields a solar activity-related 106-yr periodicity. However, comparing to a weak solar activity at 2.7ka B.P., a 100-200-yr lag of the cave-inferred mega-drought event implies a complicated mechanism of short-term solar forcing on monsoon system.
Key words: late Holocene; stalagmite; weak monsoon event; Eastern Loess Plateau; solar activity
Fig.1 The location of Dragon Cave (solid square) and other Chinese caves图1 山西太行龙洞(黑色正方形)和其它研究点 |
Table 1 Uranium and Thorium isotopic compositions and 230Th ages for L1 stalagmite from Dragon Cave by MC-ICP-MS表1 龙洞石笋L1的MC-ICP-MS 测年结果 |
样品号 | 232Th | 238U | 230Th/232Th | δ234U | 230Th/238U | 未校正年龄 | 校正年龄 | δ234Uinitial |
---|---|---|---|---|---|---|---|---|
(×10-12) | (×10-9) | (×10-12)d | 测量值a | 活度比c | (a B.P.) | (a B.P.)c,e | 校正初始值b | |
L1-3 | 191±8 | 393.4±0.7 | 196±9 | 1478±6 | 0.0058±0.0001 | 192±3 | 187±4 | 1479±6 |
L1-48 | 4288±17 | 452.6±0.8 | 68±1 | 1419±5 | 0.0391±0.0005 | 1715±24 | 1612±57 | 1426±5 |
L1-120 | 262±9 | 415.3±0.8 | 1530±55 | 1600±5 | 0.0584±0.0002 | 2415±11 | 2408±11 | 1611±5 |
L1-169 | 356±8 | 430.6±0.9 | 1368±31 | 1584±6 | 0.0685±0.0003 | 2865±13 | 2856 ±14 | 1597±6 |
L1-191 | 883±7 | 400.2±0.9 | 711±7 | 1572±9 | 0.0949±0.0005 | 4029±26 | 4006±28 | 1590±9 |
注:a.δ234U = ([234U/238U]activity-1) x 1 000; b.δ234Uinitial校正初始值计算是依据公式δ234Uinitial = δ234Umeasured × eλ234*T; T 是校正年龄; c.[230Th/238U]活度计算为[230Th/238U]activity = 1-e-λ230T + (δ234Umeasured/1 000)[λ230/(λ230-λ234)](1-e-(λ230-λ234) T); 230Th,234U,及238U半衰期沿用Shen et al.的使用值[12]; d.标本[230Th/232Th] 测量值以原子数比值表示; e.校正年龄假设的初始230Th/232Th原子数比值为4±2×10-6; 年龄(a B.P.) 以相对公元1950年表示 |
Fig. 2 Monthly average precipitation, temperature and precipitation δ18O in 1970-2000 in Shijiazhuang (a) and Yushe (b)图2 石家庄市、榆社市1970~2000年月均降水量、气温与大汽降水δ18O值对比 |
Fig.4 Paleoclimate proxy records over the past 4 000 years [(a) Holocene drift ice record of core 52-VM29-291core in the North Atlantic; (b) atmospheric Δ14C record, (c) Dragon Cave δ18O record and(d) lake sediment redness record from Liupanshan Mountain]图4 北大西洋冰漂事件[28](a)与太阳活动[29](b)、山西龙洞记录(c)以及六盘山 天池记录的夏季风强度变化[3](d)对比 (点线方框表示2 600~2 000 a B.P.气候干旱事件; 灰色阴影区(上)表示北大西洋“2.8 ka冷事件”;图d灰色阴影表示季风降水变化,源于文献[3]) |
The authors have declared that no competing interests exist.
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