POTENTIAL PALEOCLIMATE INDICATORS: COMPOSITIONS OF DETRITAL PYROXENE AND ILMENITE IN RIVER NILE AND NILE DELTA SEDIMENTS

摘要

The River Nile drainage basin collects heavy minerals from three petrologically and tectonically distinct source terranes. Amphibolite- and granulite-grade metamorphic rocks of the Central African Province feed the White Nile. Alkali and tholeiitic basalts of the Ethiopian Highlands are the sediment source for the Blue Nile and Atbara Rivers. Heterogeneous igneous and metamorphic rocks of the Red Sea Hills supply clastic sediments to currently dry river beds, termed wadis. Both detrital pyroxene and ilmenite from the three terranes are compositionally distinct. Therefore, detrital pyroxene and ilmenite grains from these source areas might be useful as provenance indicators of Nile delta sediments and paleoclimate indicators for northern Africa. Microprobe analyses of detrital ilmenite grains from a core through Nile delta sediments suggest periodic pulses of sediment input from the Red Sea Hills over the last 8,000 years.