Field evidence for flank instability,basal spreading and volcano-tectonic interactions at Mt Cameroon,West Africa |
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| Authors: | Lucie Mathieu Matthieu Kervyn Gerald G J Ernst |
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| Institution: | 1.Volcanic and Magmatic Processes Group,Dublin Trinity College,Dublin,Ireland;2.Mercator & Ortelius Research Centre for Eruption Dynamics, Department of Geology and Soil Sciences,Ghent University,Ghent,Belgium;3.Laboratoire Magmas et Volcans, Blaise Pascal Université,Clermont-Ferrand,France;4.Physical Geography Department of Geography,Vrije Universiteit Brussels,Brussels,Belgium;5.12 allée du chevalier de Louville,Saint Jean de Braye,France |
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| Abstract: | The Mt Cameroon volcano is the highest and most active volcano of the Cameroon Volcanic Line. Little geological information
is available for improving the understanding of the structure of this large volcanic system and its relationship to regional
tectonics. After reviewing the tectonic evolution of the region, the analysis of a Digital Elevation Model and results from
a field campaign dedicated to mapping geological structures in the summit area and at the SE base of Mt Cameroon are presented.
Mt Cameroon is a lava-dominated volcano with long steep (over 30°) flanks. It is elongate parallel to its well defined rift
zone. The summit plateau is bordered by 10 m high cliffs formed by summit subsidence along normal faults. Geological profiles
were measured along rivers cutting through a topographic step at the SE base of Mt Cameroon. This step is associated with
deformed Miocene sediments from the Douala basin that are overlain by volcanic products. Weak sediments of this area are deformed
by 050°–060° and 020°–030° trending asymmetrical folds verging toward the SE, and thrusts faults related to the spreading
of the volcano over its mechanically weak substratum. Combined remote sensing and field observations suggest that spreading
is accommodated by summit subsidence and flanks sliding. Both slow spreading movements and catastrophic collapses of the steep
flanks are interpreted to result from complex interactions between the growing edifice, repeated dyke intrusions, the weak
sedimentary substratum and tectonic structures. |
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