HEAVY MINERAL ANALYSIS OF NIGER DELTA SEDIMENTS

Heavy minerals from the Niger River and down core ditch cuttings permit us to test varying hypotheses to establish the provenance of Niger Delta sediments. The sediments are being analysed using petrography, U-Pb zircon age dating and single grain Geochemistry of garnets and tourmalines.

The Niger River, which extends for 4180 km and drains an area of about 2 million km², is generally believed to the principal source of sediments of the Niger Delta. However, there are published suggestions (e.g. Iloeje, 1981) that drainage to the Niger Delta may have been radically different in the past, coming principally from the present-day Benue River

Hypothesis one postulates that an ancient upper Niger system rose in the Guinea Highlands, flowed NE and emptied into inland lakes and marshes in Mali. In Quaternary time, a completely separate, lower Niger system developed, flowing southeast-ward and cutting its valley head-wards; this captured the other river and drained off the lake through to the Atlantic Ocean, leaving only shallow pools, marshes, swamps and alluvial and lake deposits to mark where it once existed while most of the sediments that originated before the capture and subsequent elongation of the Niger system remained trapped in the inland lakes. Hypothesis two suggests that the Benue, a far older river, related to Cretaceous rifting of the Gondwana supercontinent, is the actual source of most of the sediments of the Niger Delta as it has continuously delivered sediments unhindered to the delta through time. Thus, the argument is prompted: what is the actual contribution of River Niger to the development of the Niger Delta.

The various hypotheses have profound implications for prediction of reservoir sand composition in the Niger Delta.