Paper short abstract:

Geological proxies (environmental magnetism and geochemistry) have been used in reconstructing environmental change at Kilombe, Kenya. Both have proven valuable for evaluating long term trends.

Paper long abstract:

The paucity of organic remains at Kilombe necessitates the use of geological proxies (environmental magnetism and geochemistry) in reconstructing environmental change. Both proxies have proven valuable for evaluating long-term trends in climate via in intensity of chemical weathering and pedogenesis Sediment dynamics in both terrestrial and marine environments can be assessed by rock-magnetic and granulometric approaches. While traditional grain size analysis by either sieving, use of settling tubes or coulter laser diffraction mainly provides information on composition and transport, the magnetic mineral assemblages can also reveal to a greater degree the weathering conditions in the sediment source area. Here, we combine both methods to investigate the Quaternary sediments surrounding the main Acheulean occurrences at Kilombe which are shown to have been affected by dissolution.

This paper presents the results of a novel approach in quantifying the effects of dissolution on specific particle size fractions of bulk sediment samples at Kilombe using magnetic measurements. Results reveal a significant reduction in concentration of magnetite and loss of the superparamagnetic component across the < 2 micron fraction, and the progressive formation of the iron sulphide greigite from coarser to finer particle size fractions. Overall, results suggest that an increase in sediment accumulation rates resulting in rapid burial conditions is responsible for the dissolution in the Kilombe sediments which in turn may be linked to increased rates of erosion under much wetter conditions. These very much localised conditions are coeval with much wetter but highly variable climates across the Central Rift ca. 1 Ma.