PALEOENVIRONMENTAL CHANGES DURING THE LAST 4000 YR IN THE TIGRAY, NORTHERN ETHIOPIA

In the Tigray region at the northern Ethiopian Highlands, paleoenviron mental reconstruction based on several infilled valley deposit sequenc es suggests that the past 4000 yr comprised three major wetter periods (ca. 4000-3500 yr B.P., 2500-1500 yr B.P., and 1000-960 yr B.P.), dur ing which soils were formed, and two degradation episodes (ca. 3500-25 00 yr B.P. and 1500-1000 yr B.P.), during which there was an increase of sediment yield from the slopes into the valleys. For the past 1000 yr, and in particular since the early 17th century, stratigraphic reco rds together with historic chronicles suggest increasing aridity. Alth ough difficulties arise in distinguishing between natural and human im pacts, particularly in a region with a long established agricultural b ackground, stratigraphical and proxy paleoclimatic data have indicated climate as the main controlling factor responsible for the environmen tal changes in the Tigray. (C) 1998 University of Washington.