The rate of iron oxide enrichment in arid zone alluvial fan soils measured by mineral magnetic techniques

Rates of iron oxide enrichment of soils on a segmented alluvial fan in southern Tunisia are examined. Mineral magnetic and chemical characteristics of soils developed on two dated relict segments and on contemporary alluvium suggest that the rate of Fe-oxide enrichment was more rapid in the Holocene (2.6 X 10(-8) g g(-1) yr(-1) over the last 5000 years) than in the Pleistocene (1.91 X 10(-9) g g(-1) yr(-1) over the previous 45000 years), Thus, Fe-oxide concentration may be used to determine an ordinal chronology of some geomorphological surfaces in drylands, but rates of enrichment cannot be assumed to be uniform over time. (C) 1997 Elsevier Science B.V.