Abstract
SUMMARY The present-day tectonics of the southern Red Sea region is complicated by the presence of the overlapping Afar and southern Red Sea rifts as well as the uncertain kinematics and extent of the Danakil block in between. Here we combine up to 16 yr of GPS observations and show that the coherent rotation of the Danakil block is well described by a Danakil-Nubia Euler pole at 16.36°N, 39.96°E with a rotation rate of 2.83 deg Myr–1. The kinematic block modeling also indicates that the Danakil block is significantly smaller than previously suggested, extending only to Hanish-Zukur Islands (∼13.8°N) with the area to the south of the islands being a part of the Arabian Plate. In addition, the GPS velocity field reveals a wide inter-rifting deformation zone across the northern Danakil-Afar rift with ∼5.6 mm yr–1 of east–west opening across Gulf of Zula in Eritrea. Together the results redefine some of the plate boundaries in the region and show how the extension in the southern Red Sea gradually moves over to the Danakil-Afar rift.
Highlights
The tectonics in Afar and its surrounding regions of the southern Red Sea and Gulf of Aden is dominated by the Arabia–Nubia– Somalia ridge–ridge–ridge triple junction
The Oligocene to present tectonic evolution of the triple junction has involved several phases of spreading-centre reorganization that have led to the formation and isolation of microplates (Cochran 1983; Courtillot et al 1987; Acton et al 1991; Manighetti et al 2001a; Bosworth 2015), similar to what has been observed at other divergent plate boundaries like the East Pacific Rise and the Pacific– Nazca–Antarctic triple junction (Anderson-Fontana et al 1986; Engeln et al 1988)
The main difficulties include (1) that the plate boundary deformation is broadly distributed over hundreds of kilometres rather than being focused at sharp boundaries (CNR & CNRS 1975; Hayward & Ebinger 1996), (2) that parts of the Nubia–Arabia Plate boundary in the Red Sea are buried under thick salt deposits (Frazier 1970; Carbone et al 1998), (3) that small transform fault offsets along with incipient structures characterize the Red Sea spreading centre and the Nubia–Arabia–Somalia Plate boundaries, respectively (Chu & Gordon 1998; Ebinger et al 2010), (4) lack of continuous geodetic observations and (5) that many tectonic
Summary
The tectonics in Afar and its surrounding regions of the southern Red Sea and Gulf of Aden is dominated by the Arabia–Nubia– Somalia ridge–ridge–ridge triple junction It is the only place on Earth allowing for inland observations of all evolution stages of a divergent plate boundary: from the continental rifting to the onset of an oceanic ridge Models aiming to describe the present-day kinematics of the Danakil block include progressive tearing (Courtillot 1980), ’crank-arm’ tectonics (Sichler 1980; Souriot & Brun 1992; Collet et al 2000) and microplate models (Barberi & Varet 1977; Acton et al 1991; Eagles et al 2002; McClusky et al 2010; Schettino et al 2016) that consider rigid rotation of the block about a single Euler pole (Fig. 2). The results from Schettino et al (2016) indicate migration of the Danakil-Nubia Euler pole (∼390 km since 4.6 Ma), their plate boundary configuration and Euler pole
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