Laura Fielding

PhD student

Research Overview

My study aims to document the palaeodrainage history of the Nile River, in particular the time of transition from a small locally sourced drainage network to the initiation of an extensive Nile catchment, by conducting a provenance study of the well-dated Nile cone sediments. The identification of specific source inputs into the Nile cone has important implications for the prediction of reservoir quality and connectivity in hydrocarbon reservoirs.

Presently, the Nile river drains as far south as south of Lake Victoria, with the White Nile draining largely cratonic basement rocks of Archean to Proterozoic age and the Blue Nile draining continental flood basalts and Neoproterozoic basement in Ethiopia. However, the timing of catchment expansion to its current extent is highly debated. There are a number of proposed palaeodrainage reconstructions, two of which are:

A) The Blue Nile did not connect with the main (lower) Nile until the Late Messinian, and the White Nile at 0.5 Ma. In their model, the pre-Messinian Nile cone sediments are locally derived, from the Red Sea Hills (Issawi and McCauley 1992).

B) The Blue Nile and Atbara have been connected to the main (lower) Nile since the Oligocene, a time of large scale regional uplift and volcanism in the Ethiopian Highlands; the river has followed a similar course to the present day (Burke and Wells 1989).

The palaeo-Nile cone sediments provide a unique archive of the river's highly debated palaeodrainage history. Our first objective was to characterise each possible source area (Ethiopian flood basalts, Archean craton and the Neoproterozoic basement rocks and Phanerozoic cover sequences of the Red Sea Hills). We adopted a multidisciplinary approach involving petrography, geochemistry and isotope studies in order to identify the occurrence (if any) of these sources in the delta core samples.

Single grain techniques such as heavy mineral, petrographic, U/Pb rutile and Lu/Hf zircon analyses support the hypothesis of Blue Nile and/or the Red Sea Hills contributing detritus to the Nile delta since at least the Oligocene with very little input from the White Nile. U-Pb zircon studies have revealed the presence of 20-30 Ma zircons in both the modern river sediments from the Ethiopian Highlands (derived from sources such as the Lake Tana rhyolites) and the Nile Delta core from the early Miocene to present day. This infers a connection between the main Nile and the Blue Nile since at least the early Miocene. More recent analytical work continues to scrutinise the Egyptian Western Desert as a possible source area with samples being studied from Gilf Kebir and Gebel Uweinat.

Field Season: Ethiopia
Fielding, L. 01/2012
Data set/Database