The timing, two-pulsed nature, and variable climatic expression of the 4.2 ka event: A review and new high-resolution stalagmite data from Namibia

QUATERNARY SCIENCE REVIEWS

卷:186

Review

Railsback, L. Bruce¹  Liang, Fuyuan²  Brook, G. A.³  Voarintsoa, Ny Riavo G.^1,8  Sletten, Hillary R.^1,9  Marais, Eugene⁴  Hardt, Ben⁵  Cheng, Hai^6,7  Edwards, R. Lawrence⁷ 

[1] Univ Georgia, Dept Geol, Athens, GA 30602 USA

[2] Western Illinois Univ, Dept Geog, 1 Univ Circle, Macomb, IL 61455 USA

[3] Univ Georgia, Dept Geog, Athens, GA 30602 USA

[4] Gobabeb Res & Training Ctr, POB 953,Walvis Bay, Gobabeb, Namibia

[5] MIT, Dept Earth Atmospher & Planetary Sci, 77 Massachusetts Ave, Cambridge, MA 02139 USA

[6] Xi An Jiao Tong Univ, Coll Global Environm Change, Xian 710049, Shaanxi, Peoples R China

[7] Univ Minnesota, Dept Earth Sci, Minneapolis, MN 55455 USA

[8] Hebrew Univ Jerusalem, Inst Earth Sci, Edmond J Safra Campus, Jerusalem, Israel

[9] Shell Explorat & Prod Co, Houston, TX 77079 USA

关键词: Holocene;    Paleoclimatology;    Africa;    Speleothems;    4.2 ka event;    Namibia;    Stalagmite;    Paleoclimate;    Inter-tropical convergence zone;   

DOI  :  10.1016/j.quascirev.2018.02.015

来源: Elsevier

【 摘 要 】

The climatic event between 4.2 and 3.9 ka BP known as the 4.2 ka event is commonly considered to be a synchronous global drought that happened as one pulse. However, careful comparison of records from around the world shows that synchrony is possible only if the published chronologies of the various records are shifted to the extent allowed by the uncertainties of their age data, that several records suggest a two-pulsed event, and that some records suggest a wet rather than dry event. The radiometric ages constraining those records have uncertainties of several decades if not hundreds of years, and in some records the event is represented by only one or two analyses. This paper reports a new record from Stalagmite DP1 from northeastern Namibia in which high Th-230/Th-232 activity ratios allow small age uncertainties ranging between only 10-28 years, and the event is documented by more than 35 isotopic analyses and by petrographic observation of a surface of dissolution. The ages from Stalagmite DP1 combine with results from 11 other records from around the world to suggest an event centered at about 4.07 ka BP with bracketing ages of 4.15 to 3.93 ka BP. The isotopic and petrographic results suggest a two pulsed wet event in northeastern Namibia, which is in the Southern Hemisphere's summer rainfall zone where more rain presumably fell with southward migration of the Inter-Tropical Convergence Zone as the result of cooling in the Northern Hemisphere. Comparison with other records from outside the region of dryness from the Mediterranean to eastern Asia suggests that multiple climatic zones similarly moved southward during the event, in some cases bringing wetter conditions that contradict the notion of global drought. (C) 2018 Elsevier Ltd. All rights reserved.

【 授权许可】

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