Crustal variability along the rifted/sheared East African margin: a review

Vormann, Maren; Jokat, Wilfried

doi:10.1007/s00367-021-00690-y

Cited by 10 publications

(7 citation statements)

References 38 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Sauter et al (2016, 2018) using marine gravity data suggest the ocean‐continent transition is delimited by the Seagap fault zone implying the DR cuts oceanic crust. Further south in the Mozambique Channel, Vormann and Jokat (2021b), Vormann et al (2020) using velocity depth functions, suggest that the oceanic crust between 40.4°E and 40.9°E continues to 16.5°S (Figure 1). Eastwards to the DR, stretched continental crust links the DR to Madagascar.…”

Section: Regional Settingmentioning

confidence: 96%

“…Dashed and bold blue lines represent the inferred plate boundaries between Rovuma microplate, Somalian plate and Tanzania craton. Dashed orange boundaries represent the inferred ocean‐continent transition boundary based Ségoufin et al (2004), Sauter et al (2018) and Vormann and Jokat (2021b) reconstructions. Dotted‐dashed red line represent the Davie fracture zone, respectively, as by Klimke and Franke (2016) and Sinha et al (2019).…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Architecture, structural and tectonic significance of the Seagap fault (offshore Tanzania) in the framework of the East African Rift

Iacopini¹,

Tavani²,

Pentagallo³

et al. 2022

Basin Research

View full text Add to dashboard Cite

The Southeastern portion of the East African Rift System reactivates Mesozoic transform faults marking the separation of Madagascar from Africa in the Western Indian Ocean. Earlier studies noted the reactivation of the Davie Fracture Zone in oceanic lithosphere as a seismically active extensional fault, and new 3D seismic reflection data and exploration wells provide unprecedented detail on the kinematics of the sub-parallel Seagap fault zone in continental/transitional crust landward of the ocean-continent transition. We reconstruct the evolution of the seismically active Seagap fault zone, a 400-km-long crustal structure affecting the Tanzania margin, from the late Eocene to the present day. The Seagap fault zone is represented by large-scale localized structures affecting the seafloor and displaying growth geometries across most of the Miocene sediments. The continuous tectonic activity evident by our seismic mapping, as well as 2D deep seismic data from literature, suggests that from the Middle-Late Jurassic until 125 Ma, the Seagap fault acted as a regional structure parallel to, and coeval with, the dextral Davie Fracture Zone. The Seagap fault then remained active after the cessation of both seafloor spreading in the Somali basin and strike-slip activity on the Davie Fracture Zone, till nowaday. Its architecture is structurally expressed through the sequence of releasing and restraining bends dating back at least to the early Neogene. Seismic sections and horizon maps indicate that those restraining bends are generated by strike-slip reactivation of Cretaceous structures till the Miocene. Finally based on the interpretation of edge-enhanced reflection seismic surfaces and seafloor data, we shows that, by the late Neogene, the Seagap fault zone switched to normal fault behaviour. We discuss the Seagap fault's geological and kinematic significance through time and its current role within the microplate system in the framework of the East African rift, as well as implications for the evolution and re-activation of structures along sheared margins. The newly integrated datasets reveal the polyphase deformation of this margin, highlighting

show abstract

Section: Regional Settingmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

Architecture, structural and tectonic significance of the Seagap fault (offshore Tanzania) in the framework of the East African Rift

Iacopini¹,

Tavani²,

Pentagallo³

et al. 2022

Basin Research

View full text Add to dashboard Cite

show abstract

“…4). The Davie Ridge continental crustal sliver of Vormann & Jokat (2021) extends from just south of the Sakalaves Seamounts to north of Paisley Seamount (also see Fig. 1).…”

Section: How and When Did The Ancestors Of Madagascar's Land‐vertebra...mentioning

confidence: 99%

“…The shaded contour intervals have 1000‐m spacings: dark blue is −1000 m and below, white is −1000 to 0 m, pale green is 0 to +1000 m, and khaki is +1000 m and above. Note the Davie Ridge continental sliver of Vormann & Jokat (2021; see Figs 3 and 4), while the border between Mozambique and Tanzania meets the coast at c . 10.5° S. DSDP, Deep Sea Drilling Project; Smt, Seamount.…”

Section: Introductionmentioning

confidence: 99%

The colonisation of Madagascar by land‐bound vertebrates

Ali

2023

Biological Reviews

View full text Add to dashboard Cite

Despite discussions extending back almost 160 years, the means by which Madagascar's iconic land vertebrates arrived on the island remains the focus of active debate. Three options have been considered: vicariance, range expansion across land bridges, and dispersal over water. The first assumes that a group (clade/lineage) occupied the island when it was connected with the other Gondwana landmasses in the Mesozoic. Causeways to Africa do not exist today, but have been proposed by some researchers for various times in the Cenozoic. Over‐water dispersal could be from rafting on floating vegetation (flotsam) or by swimming/drifting. A recent appraisal of the geological data supported the idea of vicariance, but found nothing to justify the notion of past causeways. Here we review the biological evidence for the mechanisms that explain the origins of 28 of Madagascar's land vertebrate clades [two other lineages (the geckos Geckolepis and Paragehyra) could not be included in the analysis due to phylogenetic uncertainties]. The podocnemid turtles and typhlopoid snakes are conspicuous for they appear to have arisen through a deep‐time vicariance event. The two options for the remaining 26 (16 reptile, five land‐bound‐mammal, and five amphibian), which arrived between the latest Cretaceous and the present, are dispersal across land bridges or over water. As these would produce very different temporal influx patterns, we assembled and analysed published arrival times for each of the groups. For all, a ‘colonisation interval’ was generated that was bracketed by its ‘stem‐old’ and ‘crown‐young’ tree‐node ages; in two instances, the ranges were refined using palaeontological data. The synthesis of these intervals for all clades, which we term a colonisation profile, has a distinctive shape that can be compared, statistically, to various models, including those that assume the arrivals were focused in time. The analysis leads us to reject the various land bridge models (which would show temporal concentrations) and instead supports the idea of dispersal over water (temporally random). Therefore, the biological evidence is now in agreement with the geological evidence, as well as the filtered taxonomic composition of the fauna, in supporting over‐water dispersal as the mechanism that explains all but two of Madagascar's land‐vertebrate groups.

show abstract

“…Klimke and Franke (2016) found no evidence for the DFZ in their seismic study offshore northern Mozambique and Tanzania. This 300 km zone is frequently characterized as "transitional crust" (Vormann & Jokat, 2021), neither clearly continental nor oceanic. In the Reclus databases we have tried to provide more granularity by hypothesizing what that "transitional crust" represents (Section 5).…”

Section: The Davie Deformational Zone (Ddz)mentioning

confidence: 99%

Reclus, a New Database for Investigating the Tectonics of the Earth: An Example From the East African Margin and Hinterland

Markwick

Paton²,

Mortimer

2021

Geochem Geophys Geosyst

View full text Add to dashboard Cite

Observational data are fundamental to scientific advancement. Recently many governments and research bodies have made their data, and the data obtained through their funding, open to the public. This has proved invaluable for furthering our understanding of the Earth system. Primary data, including Landsat imagery (NASA Landsat Program, 2000), radar (SRTM: Shuttle Radar Topography Mission), and the results of the DSDP and ODP drilling programs, provided by the US Government are amongst the most important contributions to Earth sciences available. Other countries, notably Australia, Canada, New Zealand, and Norway, make industry acquired potential field, seismic, and well data available after a specified duration of time. For tectonics, there are a range of digital data sets now available, including the following: plate models (

show abstract

Crustal variability along the rifted/sheared East African margin: a review

Cited by 10 publications

References 38 publications

Architecture, structural and tectonic significance of the Seagap fault (offshore Tanzania) in the framework of the East African Rift

Architecture, structural and tectonic significance of the Seagap fault (offshore Tanzania) in the framework of the East African Rift

The colonisation of Madagascar by land‐bound vertebrates

Reclus, a New Database for Investigating the Tectonics of the Earth: An Example From the East African Margin and Hinterland

Contact Info

Product

Resources

About