Two-stage rifting in the Kenya rift: implications for half-graben models

Mugisha, Frank; Ebinger, C. J.; Strecker, Manfred R.; Pope, Denise S.

doi:10.1016/s0040-1951(97)00095-4

Cited by 49 publications

(40 citation statements)

References 23 publications

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“…Chapman and Brook, 1978;Hautot et al, 2000;Tiercelin et al, 2012) overlapped by volcanics (Elgayo and Samburu basalt, Uasin-Gishu, Sidekh and Tim phonolites) onlapping both sides of the previous early sedimentary basin with a clear flexural pattern (Baker, 1987;Chapman and Brook, 1978;Hautot et al, 2000;Mugisha et al, 1997). This period is also coeval with the first occurrence of volcanism (Kishalduga nephelinites; ≈ 16 Ma) in southern Kenya, in the area of the Upper Miocene Gregory Rift (Crossley, 1979;Crossley and Knight, 1981).…”

Section: A C C E P T E D Accepted Manuscriptmentioning

confidence: 90%

Deformation and sedimentary evolution of the Lake Albert Rift (Uganda, East African Rift System)

Simon

Guillocheau

Robin

et al. 2017

Marine and Petroleum Geology

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This study proposed a new reconstruction of the tectono-sedimentary evolution of the Lake Albert Rift based on a biostratigraphical, sedimentological and structural re-evaluation of the outcropping data and on an exceptional subsurface dataset.The infilling of the rift consists of lacustrine deposits wherein two major unconformities dated at 6.2 Ma and 2.7 Ma were characterized, coeval with major subsidence and climatic changes.Combined with the fault analysis, the evolution and distribution of the subsidence highlights a foursteps evolution of the rift after its initiation dated at 17.0 Ma.The first phase (17.0 -6.2 Ma) consists of low and diffuse extension associated with low accommodation rates ranging from 150 to 200 m/Ma. Restricted in the southern part of the basin, the depocenter location is poorly controlled by faults, meaning that the basin extension was potentially larger at this time.The second time interval (6.2 -2.7 Ma) shows an increase of accommodation rates with values reaching more than 800 m/Ma. These high rates combined with the location of the major depocenters down the bounding faults argue for a first true rifting phase.Between 2.7 Ma and 0.4 Ma, the accommodation rates decreases to reach less than 400 m/Ma and the individualization of major depocenters continue down the major fault in the southern, and northwestern parts of the basin.

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Section: A C C E P T E D Accepted Manuscriptmentioning

confidence: 90%

Deformation and sedimentary evolution of the Lake Albert Rift (Uganda, East African Rift System)

Simon

Guillocheau

Robin

et al. 2017

Marine and Petroleum Geology

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“…Mugisha et al (1997) suggested that Precambrian shear zones have influenced rift basin geometries and Mosley (1993) proposed that a network of these Proterozoic structures beneath the rift affects the magma plumbing and the rate of ascent and emplacement of magma bodies in the upper crust. Furthermore, Key et al (1989) identified joint systems that may have acted as magma conduits, as interpreted by Haug & Strecker (1995).…”

Section: Proterozoic Structuresmentioning

confidence: 99%

Influence of regional tectonics and pre-existing structures on the formation of elliptical calderas in the Kenyan Rift

Robertson

Biggs

Cashman

et al. 2015

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Calderas are formed by the collapse of large magma reservoirs and are commonly elliptical in map view. The orientation of elliptical calderas is often used as an indicator of the local stress regime; but, in some rift settings, pre-existing structural trends may also influence the orientation. We investigated whether either of these two mechanisms controls the orientation of calderas in the Kenyan Rift. Satellite-based mapping was used to identify the rift border faults, intra-rift faults and orientation of the calderas to measure the stress orientations and pre-existing structural trends and to determine the extensional regime at each volcano. We found that extension in northern Kenya is orthogonal, whereas that in southern Kenya is oblique. Elliptical calderas in northern Kenya are orientated NW-SE, aligned with pre-existing structures and perpendicular to recent rift faults. In southern Kenya, the calderas are aligned NE-SW and lie oblique to recent rift faults, but are aligned with pre-existing structures. We conclude that, in oblique continental rifts, pre-existing structures control the development of elongated magma reservoirs. Our results highlight the structural control of magmatism at different crustal levels, where pre-existing structures control the storage and orientation of deeper magma reservoirs and the local stress regime controls intra-rift faulting and shallow magmatism.

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“…1a) based on seismic reflection data [Mugisha et al, 1997;Hautot et al, 2000]. The seismic reflection data document an early (as of yet undated) stage of tectonically controlled basin subsidence beneath the Neogene Kerio Basin followed by regional thermal basin subsidence and sedimentation within a sag basin [Morley et al, 1992;Mugisha et al, 1997;Morley, 1999a;Hautot et al, 2000]. Thermo-chronological and geophysical evidence for protracted subsidence in this sag basin is corroborated by regional pinch-outs of fluvial and organic-rich lacustrine sediments exposed along the Elgeyo Escarpment [Morley et al, 1992;Mugisha, 1997;Ego, 1994;Renaut et al, 1999] and the regional extent and thickness of the overlying <14.5 Ma phonolites that cover the present-day eastern and western rift shoulders [Lippard, 1973].…”

Section: Eocene Through Middle Miocene Monotonic Slow Cooling or Rehementioning

confidence: 99%

Cenozoic extension in the Kenya Rift from low‐temperature thermochronology: Links to diachronous spatiotemporal evolution of rifting in East Africa

et al. 2015

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Key points: Data and modeling show Paleogene and middle Miocene cooling episodes  Cooling episodes separated by stable conditions, slow exhumation or subsidence  Extension pattern is compatible with random rift initiation above a plume This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process which may lead to differences between this version and the Version of Record. Please cite this article as doi: 10.1002/2015TC003949 ©2015 American Geophysical Union. All rights reserved. AbstractThe cooling history of rift shoulders and the subsidence history of rift basins are cornerstones for reconstructing the morphotectonic evolution of extensional geodynamic provinces, assessing their role in paleoenvironmental changes, and evaluating the resource potential of their basin fills. Our apatite fission-track and zircon (U-Th)/He data from the Samburu Hills and the Elgeyo Escarpment in the northern and central sectors of the Kenya Rift indicate a broadly consistent thermal evolution of both regions. Results of thermal modeling support a three-phased thermal history since the early Paleocene. The first phase (~65-50 Ma) was characterized by rapid cooling of the rift shoulders and may be coeval with faulting and sedimentation in the Anza Rift basin, now located in the subsurface of the Turkana depression and areas to the east in northern Kenya. In the second phase, very slow cooling or slight reheating occurred between ~45 and 15 Ma as a result of either stable surface conditions, very slow exhumation, or subsidence. The third phase comprised renewed rapid cooling starting at ~15 Ma. This final cooling represents the most recent stage of rifting, which followed widespread flood-phonolite emplacement and has shaped the present-day landscape through rift shoulder uplift, faulting, basin filling, protracted volcanism, and erosion. When compared with thermochronologic and geologic data from other sectors of the East African Rift System, extension appears to be diachronous, spatially disparate, and partly overlapping, likely driven by interactions between mantle-driven processes and crustal heterogeneities, rather than the previously suggested north-south migrating influence of a mantle plume.

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Two-stage rifting in the Kenya rift: implications for half-graben models

Cited by 49 publications

References 23 publications

Deformation and sedimentary evolution of the Lake Albert Rift (Uganda, East African Rift System)

Deformation and sedimentary evolution of the Lake Albert Rift (Uganda, East African Rift System)

Influence of regional tectonics and pre-existing structures on the formation of elliptical calderas in the Kenyan Rift

Cenozoic extension in the Kenya Rift from low‐temperature thermochronology: Links to diachronous spatiotemporal evolution of rifting in East Africa

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