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.