Relationships between pre-rift structure and rift architecture in Lakes Tanganyika and Malawi, East Africa

Versfelt, Joseph Winfield; Rosendahl, Bruce R.

doi:10.1038/337354a0

Cited by 185 publications

(134 citation statements)

References 17 publications

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“…These existing structures coupled with the extension orientation are ideal for localising strike-slip or transfer faults. As previously noted, the geometry of Fault 9 separating Faults 1 and 5 is reminiscent of regional-scale opposing half-graben separated by accommodation zones localised onto existing structures (e.g., Versfelt and Rosendahl, 1989), but occurs here at the basinscale. Not only, therefore, are existing earlier extensional structures important at the rift scale, they are important in determining the further differentiation and internal architecture of individual rift basins (Corti et al, 2007).…”

Section: The Role Of the Karoo Trend And Structural Inheritancementioning

confidence: 85%

“…The Nkhata basin is one of the three deep basins of the Malawi rift that accommodate >4 km sediment, and are connected across transfer, or accommodation, zones (Ebinger, 1987;Versfelt and Rosendahl, 1989;Ebinger et al, 1993). Existing structures of significance are the Ubendian Proterozoic mobile belt, known to have exerted strong influence on the location and orientation of the northern (Karonga) basin of the Malawi Rift (Rosendahl, 1987;King, 1994), and later Permian Karoo extensional basins onto which many basin separating accommodation zones are juxtaposed (e.g., Versfelt and Rosendahl, 1989) .…”

Section: Nkhata Basin Setting and Architecturementioning

confidence: 99%

“…Existing structures of significance are the Ubendian Proterozoic mobile belt, known to have exerted strong influence on the location and orientation of the northern (Karonga) basin of the Malawi Rift (Rosendahl, 1987;King, 1994), and later Permian Karoo extensional basins onto which many basin separating accommodation zones are juxtaposed (e.g., Versfelt and Rosendahl, 1989) . There are significant occurrences of Karoo sediments in a SW-NE graben to the east of the central basin of the Malawi Rift, and some deposits to the west suggesting this graben continues into the region occupied by Lake Nyasa (Figure 1b The north and central segments have been recognised by previous interpretations (e.g., Ebinger et al, 1987;Scholz, 1989;Soreghan et al, 1999;Contreras et al, 2000), separated by a relay ramp (Chilumba 'platform' Scholz, 1989) that is dissected by normal, preferentially SW-dipping faults (e.g., Soreghan et al, 1999).…”

Section: Nkhata Basin Setting and Architecturementioning

confidence: 99%

“…Past tectonic activity since the Proterozoic is responsible for inducing structural weakness in the lithosphere, which strongly influences the location and orientation of late-Cenozoic structures in both branches (Rosendahl, 1987;Versfelt and Rosendahl, 1989;.…”

Section: Introductionmentioning

confidence: 99%

“…The role of inherited structural fabrics, including PreCambrian mobile belts and Permian Karoo basins is well documented in determining the presentday structural configuration (e.g., Rosendahl, 1987;Versfelt and Rosendahl, 1989;Morley 1990;Morley et al, 1990;Corti et al, 2007).…”

Section: Introductionmentioning

confidence: 99%

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Implications of structural inheritance in oblique rift zones for basin compartmentalization: Nkhata Basin, Malawi Rift (EARS)

Mortimer

Paton

Scholz

et al. 2016

Marine and Petroleum Geology

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The Cenozoic East African Rift System (EARS) is an exceptional example of active continental extension, providing opportunities for furthering our understanding of hydrocarbon plays within rifts. It is divided into structurally distinct western and eastern branches. The western branch comprises deep rift basins separated by transfer zones, commonly localised onto pre-existing structures, offering good regional scale hydrocarbon traps. At a basin-scale, local discrete inherited structures might also play an important role on fault localisation and hydrocarbon distribution. Here, we consider the evolution of the Central basin of the Malawi Rift, in particular the influence of pre-existing structural fabrics.Integrating basin-scale multichannel 2D, and high resolution seismic datasets we constrain the border, Mlowe-Nkhata, fault system (MNF) to the west of the basin and smaller Mbamba fault (MF) to the east and document their evolution. Intra basin structures define a series of horsts, which initiated as convergent transfers, along the basin axis. The horsts are offset along a NE-SW striking transfer fault parallel to and along strike of the onshore Karoo 2 (Permo-Triassic) Ruhuhu graben. Discrete pre-existing structures probably determined its location and, oriented obliquely to the extension orientation it accommodated predominantly strike-slip deformation, with more slowly accrued dip-slip.To the north of this transfer fault, the overall basin architecture is asymmetric, thickening to the west throughout; while to the south, an initially symmetric graben architecture became increasingly asymmetric in sediment distribution as strain localised onto the western MNF. The presence of the axial horst increasingly focussed sediment supply to the west. As the transfer fault increased its displacement, so this axial supply was interrupted, effectively starving the south-east while ponding sediments between the western horst margin and the transfer fault. This asymmetric bathymetry and partitioned sedimentation continues to the present-day, overprinting the early basin symmetry and configuration. Sediments deposited earlier become increasingly dissected and fault juxtapositions changed at a small (10-100 m) scale. The observed influence of basin-scale transfer faults on sediment dispersal and fault compartmentalisation due to pre-existing structures oblique to the extension orientation is relevant to analogous exploration settings.

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Section: The Role Of the Karoo Trend And Structural Inheritancementioning

confidence: 85%

Section: Nkhata Basin Setting and Architecturementioning

confidence: 99%

Section: Nkhata Basin Setting and Architecturementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Implications of structural inheritance in oblique rift zones for basin compartmentalization: Nkhata Basin, Malawi Rift (EARS)

Mortimer

Paton

Scholz

et al. 2016

Marine and Petroleum Geology

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Hierarchical segmentation of the Malawi Rift: The influence of inherited lithospheric heterogeneity and kinematics in the evolution of continental rifts

et al. 2015

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We used detailed analysis of Shuttle Radar Topography Mission-digital elevation model and observations from aeromagnetic data to examine the influence of inherited lithospheric heterogeneity and kinematics in the segmentation of largely amagmatic continental rifts. We focused on the Cenozoic Malawi Rift, which represents the southern extension of the Western Branch of the East African Rift System. This north trending rift traverses Precambrian and Paleozoic-Mesozoic structures of different orientations. We found that the rift can be hierarchically divided into first-order and second-order segments. In the first-order segmentation, we divided the rift into Northern, Central, and Southern sections. In its Northern Section, the rift follows Paleoproterozoic and Neoproterozoic terrains with structural grain that favored the localization of extension within well-developed border faults. The Central Section occurs within Mesoproterozoic-Neoproterozoic terrain with regional structures oblique to the rift extent. We propose that the lack of inherited lithospheric heterogeneity favoring extension localization resulted in the development of the rift in this section as a shallow graben with undeveloped border faults. In the Southern Section, Mesoproterozoic-Neoproterozoic rocks were reactivated and developed the border faults. In the second-order segmentation, only observed in the Northern Section, we divided the section into five segments that approximate four half-grabens/ asymmetrical grabens with alternating polarities. The change of polarity coincides with flip-over full-grabens occurring within overlap zones associated with~150 km long alternating border faults segments. The inherited lithospheric heterogeneity played the major role in facilitating the segmentation of the Malawi Rift during its opening resulting from extension. Key Points:• Segmentation of the Malawi Rift is studied using SRTM DEM and magnetic data • The rift is hierarchically divided into first-order and second-order segments • Lithospheric heterogeneity controls firstand second-order segmentation

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Basement structure and its influence on the structural configuration of the northern North Sea rift

et al. 2017

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The northern North Sea rift basin developed on a heterogeneous crust comprising structures inherited from the Caledonian orogeny and Devonian postorogenic extension. Integrating two‐dimensional regional seismic reflection data and information from basement wells, we investigate the prerift structural configuration in the northern North Sea rift. Three seismic facies have been defined below the base rift surface: (1) relatively low‐amplitude and low‐frequency reflections, interpreted as pre‐Caledonian metasediments, Caledonian nappes, and/or Devonian clastic sediments; (2) packages of high‐amplitude dipping reflections (>500 ms thick), interpreted as basement shear zones; and (3) medium‐amplitude and high‐frequency reflections interpreted as less sheared crystalline basement of Proterozoic and Paleozoic (Caledonian) origin. Some zones of Seismic Facies 2 can be linked to onshore Devonian shear zones, whereas others are restricted to the offshore rift area. Interpreted offshore shear zones dip S, ESE, and WNW in contrast to W to NW dipping shear zones onshore West Norway. Our results indicate that Devonian strain and ductile deformation was distributed throughout the Caledonian orogenic belt from central South Norway to the Shetland Platform. Most of the Devonian basins related to this extension are, however, removed by erosion during subsequent exhumation. Basement shear zones reactivated during the rifting and locally control the location and geometry of rift depocenters, e.g., in the Stord and East Shetland basins. Prerift structures with present‐day dips >15° were reactivated, although some of the basement shear zones are displaced by rift faults regardless of their orientation relative to rift extension direction.

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Relationships between pre-rift structure and rift architecture in Lakes Tanganyika and Malawi, East Africa

Cited by 185 publications

References 17 publications

Implications of structural inheritance in oblique rift zones for basin compartmentalization: Nkhata Basin, Malawi Rift (EARS)

Implications of structural inheritance in oblique rift zones for basin compartmentalization: Nkhata Basin, Malawi Rift (EARS)

Hierarchical segmentation of the Malawi Rift: The influence of inherited lithospheric heterogeneity and kinematics in the evolution of continental rifts

Basement structure and its influence on the structural configuration of the northern North Sea rift

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