Universität zu Köln

Wagner, Bernd ORCID: 0000-0002-1369-7893, Wennrich, Volker ORCID: 0000-0003-3617-1963, Viehberg, Finn, Junginger, Annett ORCID: 0000-0003-3486-0888, Kolvenbach, Anne, Rethemeyer, Janet, Schaebitz, Frank ORCID: 0000-0003-3879-9308 and Schmiedl, Gerhard (2018). Holocene rainfall runoff in the central Ethiopian highlands and evolution of the River Nile drainage system as revealed from a sediment record from Lake Dendi. Glob. Planet. Change, 163. S. 29 - 44. AMSTERDAM: ELSEVIER SCIENCE BV. ISSN 1872-6364

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Abstract

A 12 m long sediment sequence was recovered from the eastern Dendi Crater lake, located on the central Ethiopian Plateau and in the region of the Blue Nile headwaters. 24 AMS radiocarbon dates from bulk organic carbon samples indicate that the sediment sequence spans the last ca. 12 cal kyr BP. Sedimentological and geochemical data from the sediment sequence that were combined with initial diatom information show only moderate change in precipitation and catchment runoff during that period, probably due to the elevated location of the study region in the Ethiopian highlands. Less humid conditions prevailed during the Younger Dryas (YD). After the return to full humid conditions of the African Humid Period (AHP), a similar to 2 m thick tephra layer, probably originating from an eruption of the Wenchi crater 12 km to the west of the lake, was deposited at 10.2 cal kyr BP. Subsequently, single thin horizons of high clastic matter imply that short spells of dry conditions and significantly increased rainfall, respectively, superimpose the generally humid conditions. The end of the AHP is rather gradual and precedes relatively stable and less humid conditions around 3.9 cal kyr BP. Subsequently, slightly increasing catchment runoff led to sediment redeposition, increasing nutrient supply, and highest trophic states in the lake until 1.5 cal kyr BP. A highly variable increase in clastic matter indicates fluctuating and increasing catchment runoff over the last 1500 years. The data from Lake Dendi show, in concert with other records from the Nile catchment and the Eastern Mediterranean Sea (EMS), that the Blue Nile discharge was relatively high between ca. 10.0 and 8.7 cal kyr BP. Subsequent aridification peaked with some regional differences between ca. 4.0 and 2.6 cal kyr BP. Higher discharge in the Blue Nile hydraulic regime after 2.6 cal kyr BP is probably triggered by more local increase in rainfall, which is tentatively caused by a change in the influence of the Indian Ocean monsoon.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Wagner, Bernd UNSPECIFIED orcid.org/0000-0002-1369-7893 UNSPECIFIED Wennrich, Volker UNSPECIFIED orcid.org/0000-0003-3617-1963 UNSPECIFIED Viehberg, Finn UNSPECIFIED UNSPECIFIED UNSPECIFIED Junginger, Annett UNSPECIFIED orcid.org/0000-0003-3486-0888 UNSPECIFIED Kolvenbach, Anne UNSPECIFIED UNSPECIFIED UNSPECIFIED Rethemeyer, Janet UNSPECIFIED UNSPECIFIED UNSPECIFIED Schaebitz, Frank UNSPECIFIED orcid.org/0000-0003-3879-9308 UNSPECIFIED Schmiedl, Gerhard UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-190655
DOI:	10.1016/j.gloplacha.2018.02.003
Journal or Publication Title:	Glob. Planet. Change
Volume:	163
Page Range:	S. 29 - 44
Date:	2018
Publisher:	ELSEVIER SCIENCE BV
Place of Publication:	AMSTERDAM
ISSN:	1872-6364
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language AFRICAN HUMID PERIOD; EASTERN MEDITERRANEAN SEA; LATE PLEISTOCENE; CLIMATE-CHANGE; VEGETATION RESPONSE; SAPROPEL FORMATION; CATCHMENT-AREA; WATER-LEVEL; AEGEAN SEA; NORTHERN Multiple languages Geography, Physical; Geosciences, Multidisciplinary Multiple languages
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/19065