DEPOSITIONAL ENVIROMENTS OF THE BIMA SANDSTONE OF THE YOLA ARM, BENUE TROUGH
DEPOSITIONAL ENVIROMENTS OF THE BIMA SANDSTONE OF THE YOLA ARM, BENUE TROUGH
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Date
2014-02-06
Authors
NUHU., KADAI SAMAILA
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Abstract
The Yola Arm of the Benue Trough is an elongate basin
approximately 210km long, and average 70km in width,, It
trends roughtly east-west, and was formed by sinistral
displacements of inherited transcurrent faults during the
Aptian-Albi an (Cretaceous)times.
A study of the sedimentary structures and depositional
motif of the Bima Sandstone, the oldest formation in the
Yola Arm, suggest deposition in alluvial fans,
1acustrine/f1oodplain, and f1uvial environments were
dominant.
The alluvial fans consist of unstratified coarse-grained
conglomerates on the southern margin, and parallel to
cross-stratified fine grained conglomerates on the
northern margin. The 1acustrine/f1oodplain depositional
environment is characterised by silts and shales with wavy
and lenticular bedding,mudcracks, and shale rip-up clasts.
The f1uvia1 environment is characterized by planar and
trough cross-bedded structures of unimodal vectors.
Bynsedimentary deformation structures in the basin's
axial deposits may suggest several tectonic causes, one
which is penecontemporaneous seismic activity at the basin
- margin faults.
The Yola Arm is considered a pull-apart basin for
the following reasons: (i)rapid facies changes from basin
margin to basin margin, (ii) migration of depocenter
causing over-lap of basement by the sediments, (iii) great
thickness of deposits estimated at 4.6km from geophysical
studies, (iv) complexity in sedimentary structures, and (v)
evidence of strike-slip movement
Description
A thesis submitted to the Postgraduate School,
Ahmadu Bello University, in partial fulfillment
of the requirements for the degree
of Master of Science in Sedimentology
Department of Geology,
Faculty of Science,
Ahmadu Bello University,
Zaria, Nigeria.
March
Keywords
DEPOSITIONAL,, ENVIROMENTS,, BIMA SANDSTONE,, YOLA ARM,, BENUE TROUGH