Tectono-thermal evolution of a long-lived segment of the East African Rift System: Thermochronological insights from the North Lokichar Basin, Turkana, Kenya

Boone, Samuel C.; Kohn, Barry P.; Gleadow, Andrew; Morley, Christopher; Seiler, Christian; Foster, David A.; Chung, Ling

doi:10.1016/j.tecto.2018.06.010

Cited by 22 publications

(17 citation statements)

References 131 publications

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“…The presence of a top basement erosional unconformity and large decreases in paleotemperature (~80–90 °C), as indicated by t‐T reconstructions, are consistent with erosional denudation as the mechanism for observed cooling. A similar period of denudational cooling, both in timing and character, has been observed in low‐temperature thermochronology studies performed throughout much of East Africa (e.g., Boone, Seiler, et al, ; Boone, Kohn, et al, ; Foster & Gleadow, , , ; Noble et al, ; Torres Acosta et al, ). This pervasive period of cooling has been interpreted as recording denudation of the Anza rift margin and adjacent hinterlands during the development of the NW‐SE trending, Cretaceous‐early Paleogene graben (e.g., Foster & Gleadow, ).…”

Section: Thermal History Modelingsupporting

confidence: 57%

“…30 Ma (Morley et al, ). By the Oligocene, EARS‐related extension had begun with the development of the ~N‐S trending Lokichar and Lothidok basins in the Turkana Depression (Boone, Kohn, et al, ; Morley, Stone, et al, ). Both the early onset of volcanism and rift basin formation in the Turkana Depression were likely associated with the region's preattenuated lithosphere, thermomechanically modified during earlier Cretaceous‐early Paleogene Anza‐South Sudan rifting and/or Eocene plume impingement (e.g., Ebinger et al, ; Morley, Stone, et al, ).…”

Section: Tectonic Implicationsmentioning

confidence: 99%

“…While the EARS is primarily composed of a narrow (~100 km) corridor of middle‐late Miocene aged grabens and half‐grabens, active deformation in the BRZ is diffused over a much broader region (as wide as ~300 km) in a series of basins and ranges that extends into the Turkana Depression of northern Kenya (Baker et al, ; Davidson & Rex, ). Moreover, field mapping, structural geology, and thermochronological studies suggest that EARS extensional deformation began earlier in the Turkana Depression (late Paleogene) and BRZ (early Miocene) than in the Main Ethiopian Rift (MER) and Kenyan Rift to the north and south (Balestrieri et al, ; Boone, Kohn, et al, ; Ebinger et al, , ; Morley et al, , Morley, Stone, et al, ; Pik et al, ; Woldegabriel & Aronson, ). Unlike the MER and Kenyan Rift, where volcano‐tectonic activity is well documented, the evolution of the BRZ is, by comparison, poorly constrained due to a relative scarcity of geological observations and subsurface data.…”

Section: Introductionmentioning

confidence: 99%

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Tectonothermal Evolution of the Broadly Rifted Zone, Ethiopian Rift

et al. 2019

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The Broadly Rifted Zone (BRZ) of southern Ethiopia is a long-lived and structurally complex segment of the East African Rift System. However, due to poor surface exposure of early synrift strata and a dearth of subsurface data, the evolution of the BRZ remains poorly understood. We present new apatite (U-Th-Sm)/He and augmented apatite fission track low-temperature thermochronology data from the Beto and Galana basin boundary fault systems to constrain the tectonothermal evolution of the western and eastern BRZ, respectively. Time-temperature reconstructions suggest that East African Rift System-related extension began concurrently across the BRZ in the early Miocene (20-17 Ma), at least 6 Myr prior to faulting in the Main Ethiopian Rift further north. Increased time-temperature resolution provided by multithermochronometer analyses reveals contrasting along-strike spatiotemporal variations in Beto and Galana margin cooling histories, which appear to mirror the disparate structural geometries of their basin-bounding normal fault arrays. Longitudinal contrasts in basin architecture and rift-related cooling histories across the BRZ may reflect the region's heterogeneous distribution of preexisting basement fabrics, namely, the presence of a previously reported N-NNE trending Neoproterozoic suture zone beneath the eastern BRZ. Its influence may explain both the development of long, curvilinear faults and the gradual basinward migration of strain exhibited by the easternmost BRZ, absent further west. The anomalous evolution of the BRZ compared to the greater Ethiopian Rift, both in its earlier onset and its wider deformation zone, likely results from its inheritance of preattenuated lithosphere, thermomechanically modified by earlier Cretaceous-Paleogene Anza-South Sudan rifting and/or Eocene plume impingement.

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Section: Thermal History Modelingsupporting

confidence: 57%

Section: Tectonic Implicationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Tectonothermal Evolution of the Broadly Rifted Zone, Ethiopian Rift

et al. 2019

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“…are about 40-60°C/km in many other rifts (e.g., Barnard et al, 1992;Ren et al, 2002;Ranalli and Rybach, 2005;Boone et al, 2018). We thus propose that a paleo-geotherm of about 50-60°C/km at the end of the Triassic is reasonable.…”

Section: Conceptual Model Of Permian Crustal Thinningmentioning

confidence: 60%

Tectono-sedimentary evolution of a rift system controlled by Permian post-orogenic extension and metamorphic core complex formation (Bidarray Basin and Ursuya dome, Western Pyrenees)

et al. 2019

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HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés. Distributed under a Creative Commons Attribution-NonCommercial-NoDerivatives| 4.0 International License

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“…The age of rifting is diachronous and spans the time period between the Eocene and the present day; there is a general easterly and southerly younging in both rift-basin and volcanic activity ( Fig. 3; Morley et al, 1992Morley et al, , 1999aVetel, 2005;Vetel and Le Gall, 2006;Boone et al, 2018b). Some basins or stages in basin development are filled primarily by basement-derived coarse clastics and lacustrine shales, while other basins or stages in basins are dominated by lavas and pyroclastic and volcaniclastic deposits (Boschetto et al, 1992;Morley et al, 1999a;Vetel and Le Gall, 2006;Fig.…”

Section: ■ Geological Backgroundmentioning

confidence: 99%

Early syn-rift igneous dike patterns, northern Kenya Rift (Turkana, Kenya): Implications for local and regional stresses, tectonics, and magma-structure interactions

Morley

2020

Geosphere

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Four areas (Loriu, Lojamei, Muranachok-Muruangapoi, Kamutile Hills) of well-developed Miocene-age dikes in the northern Kenya Rift (Turkana, Kenya) have been identified from fieldwork and satellite images; in total, >3500 dikes were mapped. Three areas display NNW-SSE– to N-S–oriented dike swarms, with straight, radial, and concentric patterns in zones <15 km long, and indicate NNW-SSE to N-S regional maximum horizontal principal stress (SHmax) directions in the early to middle Miocene. Individual dikes are typically <2 m wide and tens to hundreds of meters long and have accommodated <2% extension. In places (Loriu, Lojamei, Lokhone high), dikes trend at a high angle to the rift trend, suggesting some local influence (e.g., overpressured magma chamber, cracked lid–style dike intrusions over a sill or laccolith, preexisting fabric in basement) on orientation, in addition to the influence from regional stresses. Only a minor influence by basement fabrics is seen on dike orientation. The early- to middle-Miocene dikes and extrusive activity ended a long phase (up to 25 m.y.) of amagmatic half-graben development in central Kenya and southern Turkana, which lay on the southern edge of the early (Eocene–Oligocene) plume activity. The Miocene dike sets and extension on major border faults in Turkana contrast with larger, more extensive arrays of dikes in evolved systems in the Main Ethiopian Rift that are critical for accommodating crustal extension. By the Pliocene–Holocene, magmatism and intrusion along dikes had become more important for accommodating extension, and the tectonic characteristics began to resemble those of rift basins elsewhere in the eastern branch of the East African Rift.

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Tectono-thermal evolution of a long-lived segment of the East African Rift System: Thermochronological insights from the North Lokichar Basin, Turkana, Kenya

Cited by 22 publications

References 131 publications

Tectonothermal Evolution of the Broadly Rifted Zone, Ethiopian Rift

Tectonothermal Evolution of the Broadly Rifted Zone, Ethiopian Rift

Tectono-sedimentary evolution of a rift system controlled by Permian post-orogenic extension and metamorphic core complex formation (Bidarray Basin and Ursuya dome, Western Pyrenees)

Early syn-rift igneous dike patterns, northern Kenya Rift (Turkana, Kenya): Implications for local and regional stresses, tectonics, and magma-structure interactions

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