Matching conjugate volcanic rifted margins: 40Ar/39Ar chrono-stratigraphy of pre- and syn-rift bimodal flood volcanism in Ethiopia and Yemen

Ukstins, Ingrid; Renne, Paul R.; Wolfenden, E.; Baker, Joel A.; Ayalew, Dereje; Menzies, Martin

doi:10.1016/s0012-821x(02)00525-3

Cited by 231 publications

(150 citation statements)

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“…South of ∼ 7°N border fault stratigraphy shows that faulting was well established by ∼ 18 Ma (Bonini et al, 2005;Ebinger et al, 1993;WoldeGabriel et al, 1990). Between 7°N and 10°N, however, syn-rift growth of sedimentary and volcanic sequences, constrained by fission track thermochronology on exposed basement, indicates that rapid growth of border faults may have started somewhat later, between 6 and 11 Ma (Abebe et al, 2010;Bonini et al, 2005;Ukstins et al, 2002;Wolfenden et al, 2004) (Fig. 2).…”

Section: Rift Initiationmentioning

confidence: 99%

“…Simplified structural map of southern Afar and northern Main Ethiopian rift (modified after Keir et al, 2011b). Annotated dates showing the age of the onset of rifting estimated from 40 Ar/ 39 Ar dates on synrift volcanic rocks Ukstins et al, 2002;Wolfenden et al, 2004Wolfenden et al, , 2005. Thin gray lines are Pliocene age faults, and thin black lines are Quaternary-Recent faults along the rift axis.…”

Section: Rift Initiationmentioning

confidence: 99%

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The development of extension and magmatism in the Red Sea rift of Afar

et al. 2013

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Despite the importance of continental breakup in plate tectonics, precisely how extensional processes such as brittle faulting, ductile plate stretching, and magma intrusion evolve in space and time during the development of new ocean basins remains poorly understood. The rifting of Arabia from Africa in the Afar depression is an ideal natural laboratory to address this problem since the region exposes subaerially the tectonically active transition from continental rifting to incipient seafloor spreading. We review recent constraints on along-axis variations in rift morphology, crustal and mantle structure, the distribution and style of ongoing faulting, subsurface magmatism and surface volcanism in the Red Sea rift of Afar to understand processes ultimately responsible for the formation of magmatic rifted continental margins. Our synthesis shows that there is a fundamental change in rift morphology from central Afar northward into the Danakil depression, spatially coincident with marked thinning of the crust, an increase in the volume of young basalt flows, and subsidence of the land towards and below sea-level. The variations can be attributed to a northward increase in proportion of extension by ductile plate stretching at the expense of magma intrusion. This is likely in response to a longer history of localised heating and weakening in a narrower rift. Thus, although magma intrusion accommodates strain for a protracted period during rift development, the final stages of breakup are dominated by a phase of plate stretching with a shift from intrusive to extrusive magmatism. This late-stage pulse of decompression melting due to plate thinning may be responsible for the formation of seaward dipping reflector sequences of basalts and sediments, which are ubiquitous at magmatic rifted margins worldwide.

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Section: Rift Initiationmentioning

confidence: 99%

Section: Rift Initiationmentioning

confidence: 99%

The development of extension and magmatism in the Red Sea rift of Afar

et al. 2013

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“…The initiation of rifting in Afar occurred between 31 and 29 Ma (Hofmann et al, 1997;Ukstins et al, 2002), with initial extension thought to be accommodated by large-scale border faults (Wolfenden et al, 2005). In northern Afar, strain localized to north-northwest-southsoutheast (NNW-SSE)-trending 10-30-km-wide 60-100-km-long axial volcanic segments between 25 and 20 Ma (Hayward and Ebinger, 1996;Wolfenden et al, 2005).…”

Section: Geological Settingmentioning

confidence: 99%

Local Earthquake Magnitude Scale andb‐Value for the Danakil Region of Northern Afar

Illsley‐Kemp¹,

Keir²,

Bull³

et al. 2017

Bulletin of the Seismological Society of America

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The Danakil region of northern Afar is an area of ongoing seismic and volcanic activity caused by the final stages of continental breakup. To improve the quantification of seismicity, we developed a calibrated local earthquake magnitude scale. The accurate calculation of earthquake magnitudes allows the estimation of b-values and maximum magnitudes, both of which are essential for seismic-hazard analysis. Earthquake data collected between February 2011 and February 2013 on 11 three-component broadband seismometers were analyzed. A total of 4275 earthquakes were recorded over hypocentral distances ranging from 0 to 400 km. A total of 32,904 zero-to-peak amplitude measurements (A) were measured on the seismometer's horizontal components and were incorporated into a direct linear inversion that solved for all individual local earthquake magnitudes (M L ), 22 station correction factors (C), and 2 distance-dependent factors (n, K) in the equation M L logA− logA 0 C. The resultant distance correction term is given by − logA 0 1:274336 logr=17 − 0:000273r − 17 2. This distance correction term suggests that attenuation in the upper and mid-crust of northern Afar is relatively high, consistent with the presence of magmatic intrusions and partial melt. In contrast, attenuation in the lower crust and uppermost mantle is anomalously low, interpreted to be caused by a high melt fraction causing attenuation to occur outside the seismic frequency band. The calculated station corrections serve to reduce the M L residuals significantly but do not show a correlation with regional geology. The cumulative seismicity rate produces a b-value of 0:9 0:06, which is higher than most regions of continental rifting yet lower than values recorded at midocean ridges, further supporting the hypothesis that northern Afar is transitioning to seafloor spreading.Electronic Supplement: List of all local earthquakes used in the study with calculated local magnitudes and associated magnitude error.

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“…A trachyte near the base of the section produced a weighted phlogopite isochron age of 30.92 ± 0.11 Ma (Ukstins et al 2002). Overlying ignimbrites gave sanidine isochron ages of 30.16 ± 0.13, 29.61 ± 0.12, and 29.68 ± 0.15 Ma, while overlying basalts yielded 29.34 ± 0.15, 25.1 ± 0.2, and 25.0 ± 0.2 Ma plagioclase isochron ages.…”

Section: Afar and The Ethiopian Plateaumentioning

confidence: 99%

Early magmatism in the greater Red Sea rift: timing and significance

Bosworth¹,

Stöckli

2016

Can. J. Earth Sci.

103

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Throughout the greater Red Sea rift system the initial late Cenozoic syn-rift strata and extensional faulting are closely associated with alkali basaltic volcanism. Older stratigraphic units are either pre-rift or deposited during pre-rupture mechanical weakening of the lithosphere. The East African superplume appeared in northeast Africa ϳ46 Ma but was not accompanied by any significant extensional faulting. Continental rifting began in the eastern and central Gulf of Aden at ϳ31-30 Ma coeval with the onset of continental flood volcanism in northern Ethiopia, Eritrea, and western Yemen. Volcanism appeared soon after at Derudeb in southern Sudan and at Harrats Hadan and As Sirat in Saudi Arabia. From ϳ26.5 to 25 Ma a new phase of volcanism began with the intrusion of a dike field reaching southeast of Afar into the Ogaden. At 24-23 Ma dikes were emplaced nearly simultaneously north of Afar and reached over 2000 km into northern Egypt. The dike event linked Afar to the smaller Cairo mini-plume and corresponds to initiation of lithospheric extension and rupture in the central and northern Red Sea and Gulf of Suez. By ϳ21 Ma the dike intrusions along the entire length of the Red Sea were completed. Each episodic enlargement of the greater Red Sea rift system was triggered and facilitated by breakthrough of mantle-derived plumes. However, the absence of any volumetrically significant rift-related volcanism during the main phase of Miocene central and northern Red Sea -Gulf of Suez rifting supports the interpretation that plate-boundary forces likely drove overall separation of Arabia from Africa.Résumé : Dans l'ensemble du grand système du rift de la mer Rouge, les strates initiales syn-rifting et l'extension par failles d'âge cénozoïque tardif sont étroitement associées à un volcanisme basaltique alcalin. Les unités stratigraphiques plus anciennes précèdent la formation du rift ou ont été déposées durant l'affaiblissement mécanique de la lithosphère qui a précédé la rupture. Le superpanache est-africain est apparu dans le nord-est de l'Afrique à ϳ46 Ma, mais n'était pas accompagné d'une importante déformation par failles. Le rifting continental a commencé dans l'est et le centre du golfe d'Aden à ϳ31-30 Ma, en même temps que le début du volcanisme continental de plateau dans le nord de l'Éthiopie, en Érythrée et dans l'ouest du Yémen. Le volcanisme est apparu peu après à Derudeb, dans le sud du Soudan, et aux Harrats Hadan et As Sirat, en Arabie saoudite. À partir de ϳ26,5-25 Ma, une nouvelle phase de volcanisme a débuté avec l'intrusion d'un essaim de dykes allant du sud-est d'Afar jusque dans l'Ogaden. À 24-23 Ma, des dykes ont été mis en place presque simultanément au nord d'Afar et s'étalant sur plus de 2000 km jusque dans le nord de l'Égypte. L'intrusion de dykes a relié Afar au mini-panache plus petit du Caire et correspond au début de la distension et de la rupture lithosphériques dans le centre et le nord de la mer Rouge et le golfe de Suez. À ϳ21 Ma, l'intrusion de dykes sur toute la longueur de ...

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Matching conjugate volcanic rifted margins: 40Ar/39Ar chrono-stratigraphy of pre- and syn-rift bimodal flood volcanism in Ethiopia and Yemen

Cited by 231 publications

References 38 publications

The development of extension and magmatism in the Red Sea rift of Afar

The development of extension and magmatism in the Red Sea rift of Afar

Local Earthquake Magnitude Scale andb‐Value for the Danakil Region of Northern Afar

Early magmatism in the greater Red Sea rift: timing and significance

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