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Publication Details
AFRICAN RESEARCH NEXUS
SHINING A SPOTLIGHT ON AFRICAN RESEARCH
earth and planetary sciences
Environmental changes and the rise and fall of civilizations in the northern horn of africa: An approach combining δd analyses of land-plant derived fatty acids with multiple proxies in soil
Geochimica et Cosmochimica Acta, Volume 111, Year 2013
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Description
The domains of the ancient polities D'MT and Aksum in the Horn of Africa's highlands are a superior natural system for evaluating roles of environmental change on the rise and fall of civilizations. To compare environmental changes of the times of the two polities, we analyzed stable hydrogen isotopic ratios (δD) of land-plant derived fatty acids (n-C26-30) and other proxies from soil sequences spanning the Holocene from the region. Three results suggest that trends in δD values unambiguously reflect changes in rainfall. First, increases in δD coincide with dry periods inferred from studies of eastern African lakes. Second, changes in δD values were parallel among sections during overlapping time intervals. Third, consideration of vegetation history did not alter directions of trends in δD values over time. By unambiguously recording precipitation, the δD values also enhanced interpretations of proxies that are affected by both climate and land clearing.Both D'MT (ca 2750-2350calyBP) and the Aksumite (ca 2100-1250calyBP) rose during wetter intervals of the drier part of the Holocene (after ca 6000calyBP). Analyses of charred matter indicated that fire had been a common agent of land clearing in all sites. The influence of climate on fire varied, however. Prior to the emergence of D'MT, δD values were correlated with C4:C3 plant ratios estimated from δ13C values. There are no C4 trees and precipitation may have been the main influence on canopy openness. After ca 4300calyBP, there was no significant relationship between δD and C4:C3 plant ratios suggesting that factors such as fire influenced canopy openness regardless of climate. Furthermore, the impact of land clearance differed between sites and between D'MT and the Aksumite's times. In one site, the interval from 3550calyBP to the decline of D'MT had several anomalies that suggested dramatic increases in thermal severity of fire and human impact. Among these were a large contribution of charred matter to a high% total organic carbon that low hydrogen and oxygen indices suggest was severely altered by other factors than humification. These results support hypotheses about the rise of civilizations being favored by specific climatic conditions but suggest that patterns of land clearing differed during the declines of D'MT and the Aksumite. © 2012 Elsevier Ltd.
Authors & Co-Authors
Terwilliger, Valery J.
United States, Lawrence
University of Kansas
France, Paris
Insu - Institut National Des Sciences de L'univers
France, Orleans
Le Studium Loire Valley Institute for Advanced Studies
Eshetu, Zewdu
Ethiopia, Addis Ababa
Addis Ababa University
Disnar, Jean Robert
France, Paris
Insu - Institut National Des Sciences de L'univers
Jacob, Jérémy
France, Paris
Insu - Institut National Des Sciences de L'univers
Adderley, W. Paul
United Kingdom, Stirling
University of Stirling
Huang, Yongsong
United States, Providence
Brown University
Alexandre, Marcelo
Brazil, Sao Cristovao
Université Fédérale de Sergipe
Fogel, Marilyn Louise
United States, Washington, D.c.
Carnegie Institution of Washington
Statistics
Citations: 17
Authors: 8
Affiliations: 8
Identifiers
Doi:
10.1016/j.gca.2012.10.040
ISSN:
00167037
Research Areas
Environmental