LITHOSTRATIGRAPHY AND SEDIMENTOLOGICAL STUDIES OF THE ALBIAN TO CENOMANIAN SUCCESSIONS, PART OF MIDDLE BENUE TROUGH, NIGERIA
LITHOSTRATIGRAPHY AND SEDIMENTOLOGICAL STUDIES OF THE ALBIAN TO CENOMANIAN SUCCESSIONS, PART OF MIDDLE BENUE TROUGH, NIGERIA
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Date
2015-12
Authors
ISHAYA, Ephraim Dauda
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Abstract
The stratigraphy of the Albian to Cenomanian successions in the Middle Benue Trough comprises of the marine Asu River Group, the transitional Awe Formation and the continental Keana Formation. Previous authors regarded the Asu River Group to consist of the Arufu, Uomba and Gboko Formations which are lateral equivalent facies depending on the locality. Lithostratigraphic studies describes the marine Uomba Formation of the Asu River Group in the study area to comprise of fineto medium grained regularly bedded sandstones overlying massive shaly mudstones and dark grey to black fissile shales, no fossils observed due to the anoxic/reducing conditions at the time of deposition with low supply of nutrients. The heavy mineral suite is of moderate diversity comprising of euhedral zircon, tourmaline and magnetite suggesting an igneous source with few rounded grains indicating some degree of transport before deposition. The transitional Awe Formation comprises of grey to black shales, calcareous and micaceous shales, calcareous sandstones some occurring as nodules towards the top, fine to medium grained white sandstones and clays deposited in a shallow marine environment associated with tidal currents. Petrographic studies following the classification scheme, classify the sediments in this formation to comprise of quartz arenite and subarkoses. Current ripples are the major sedimentary structures observed; trace fossils thalassinoides also occur in the micaceous silty shales, bioclastic remains (bivalve) were seen especially in the calcareous sandstones suggesting deposition in oxidized nutrient rich environment. The heavy minerals suite is of low diversity dominant of euhedral light and colourless zircon with few rounded ones, brownish tourmaline and magnetite suggesting an igneous provenance while the rounded grains are of sedimentary (reworked sediment) provenance. This formation is cut by several mineralised veins rich in quartz and barite in some places. The continental Keana Formation occurs towards the northern part of the study area. Lithostratigraphic studies shows coarse grained massive sandstone occurring as parallel beds and in some places as boulders which indicate deposition in a deltaic environment under a high to moderate energy conditions (delta mouth bar). The heavy mineral suite comprises mainly of dominantly light and colourless euhedral zircon, brownish tourmaline and opaque minerals (magnetite) suggesting an igneous provenance while the rounded grains indicate a sedimentary source (reworked sediments).
Description
A THESIS SUBMITTED TO THE SCHOOL OF POSTGRADUATE STUDIES AHMADU BELLO UNIVERSITY, ZARIA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE AWARD OF A DEGREE OF MASTER OF SCIENCE IN GEOLOGY DEPARTMENT OF GEOLOGY, FACULTY OF SCIENCES, AHMADU BELLO UNIVERSITY, ZARIA, NIGERIA.
Keywords
LITHOSTRATIGRAPHY,, SEDIMENTOLOGICAL STUDIES,, ALBIAN,, CENOMANIAN SUCCESSIONS,, PART,, MIDDLE BENUE TROUGH,, NIGERIA.