Using Remote Sensing and GIS to Identify Magmatic Strain Accommodation: The Case Study of Mt Marsabit, Kenya

Abstract

Previous research has demonstrated that the morphology and linear arrays of extrusive volcanic features indicate the presence and orientations of the magmatic constructs that feed them. In extensional tectonic environments, like the East African Rift (EAR), trends of these subsurface dikes can be controlled by inherited lithospheric structures or by the direction of applied stress. Mapping extrusive volcanic features with remote sensing allows for detailed geo-spatial analysis that can reveal valuable data regarding the state of stress in the region or the presence of pre-existing fractures and other lithospheric structures. Mt Marsabit, Kenya (2.32°N, 37.97°E) is a basaltic shield volcano located on the eastern edge of the Turkana Depression in Northern Kenya. The Turkana Depression is a topographical low area of extensional deformation linking the Main Ethiopian Rift (MER) and the Kenya Rift, characterized by a very thin rifted lithosphere (50-60 km; Fishwick, 2010; Kounoudis et al., 2021). While there is typically a predominant north-south orientation of structural and volcanic features in the EAR, some features in east Turkana (e.g. the Dilo-Durkana, Mega, and Hurri Hills volcanic fields) demonstrate superficial NE-SW trends, oblique to the main rift trend. The monogenetic volcanic field situated on Mt Marsabit is no exception and hosts hundreds of tuff cones and maar craters exhibiting an apparent NE-SW trend. The cause of these trends is so far unknown. Here we present data from the mapping and analysis of extrusive volcanic features on Mt Marsabit in an effort to improve our understanding of the tectonic and structural controls on crustal magma transport in this off-axis region of rifting. Analysis of the morphology of these features is performed in ArcGIS Pro while alignments of these features are analyzed in MATLAB. Previously published geological maps are also examined. This volcanic field exhibits a strong northeast-southwest trend in both morphology and linear arrays. Similar trends are observed in other volcanic fields in the eastern extent of the Turkana Depression. The obliquely oriented dikes in these fields may be a result of a combination of controls: en-echelon deformation zones associated with a component of strike-slip deformation; and a rotation of the local stress field.