Paleohydraulic Analysis of the Lower Part of Hasawnah Formation, Libya

By

 G. Mayouf¹, B. Turner²

(1) Petroleum Research Centre, Tripoli, Libya (2) University of Durham, Durham, United Kingdom

 Palaeohydraulic analysis has proved useful in reconstructing a variety of flow parameters in meandering and braided river systems, mainly with a view to comparing the flow variables with modern rivers of broadly similar scale. However, these flow parameters have been estimated for individual bars or a relatively small number of representative bars for a specific reach of the river system, and no attempt has been made to continuously monitor flow variables through time in a thick, cyclically deposited braided river system. These variables not only provide clues to how flow variables changed through time but also whether they show any pattern or cyclically which may be related to allocyclic or authocyclic factors affecting deposition and flow conditions in that particular part of the river system.

Palaeo flow parameters of ancient river systems have been estimated using three main approaches: (1) these based on the dimensions of sedimentary structures, most notably cross-bed generated by the river system and how these related to the water depths and flow velocities; (2) those based on textural analysis of cross beds and their relationship to flow velocities; (3) those based on cross bedding measurements and the sinuosity of the channel.

In this study we have used palaeohydraulic analysis based on the mean thickness of cross bedded units with in individual, vertically-stacked fining up ward cycles with in th lower part of the Cambrian Hasawnah Formation in the Ghadames Basin of western Libya, in order to estimate flow depth and flow velocity, both with in individual cycles and through out the suction, which was deposited by a sandy braided stream.