Abstract
AbstractExtensional plate boundaries are segmented by offsets that transfer extension between the ends of adjacent portions of the rift by linkage zones ranging in width from a few tens of kilometers to several hundreds of kilometers. However, the kinematics of linkage zones is poorly constrained as direct observations are difficult to make. Here we combine InSAR, seismicity, and structural geology data from the Afar rift to show that an active linkage zone currently connects the two offset Erta Ale and Tat Ali segments. The overall right‐lateral shear between the segments is accommodated primarily by oblique left‐lateral slip along faults subparallel to the rift segments but an active conjugate fault system with right‐lateral slip is also present. Our results provide the first direct observational evidence that offset rift segments during continental breakup can be linked by a shear zone composed of a conjugate set of oblique slip faults.
Highlights
During magma‐rich continental rupture, magmatic and tectonic activity is accommodated at the rift axis along distinct magmatic segments (Hayward & Ebinger, 1996)
Extension between offset rift segments is transferred through linkage zones whose geometry and kinematics affects the architecture of the plate boundary and may control ridge segmentation after breakup (Illsley‐Kemp et al, 2018; Wetzel et al, 1993)
Using a multidisciplinary set of structural, seismic, and InSAR data we observe the tectonic processes occurring in the Afrera Plain (AP) linkage zone between the Erta Ale (EA) and Tat Ali (TA) segments in northern Afar
Summary
During magma‐rich continental rupture, magmatic and tectonic activity is accommodated at the rift axis along distinct magmatic segments (Hayward & Ebinger, 1996). The extension is mainly focused in en echelon magmatic segments, similar in morphology and spacing to the segments observed along slow spreading mid‐ocean ridges (Hayward & Ebinger, 1996; Keir et al, 2009). Geophysical and geological observations of rifting episodes in Afar and Iceland have shown that spreading at the axial magmatic segments occurs through repeated diking (e.g., Dabbahu, 2005–2010 and Krafla, 1975–1984, Wright et al, 2012) fed by crustal magma chambers and normal faulting (Pagli et al, 2014; Wright et al, 2012). Our data show that left‐lateral oblique slip along ~N‐S oriented faults occurs, indicating that a nontransform zone of oblique tectonics achieves plate boundary linkage between the EA and TA rifts
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