Detailed field-structural mapping of Neoproterozoic
basement rocks exposed in the Wadi Yiba area, southern
Arabian Shield, Saudi Arabia illustrates an important
episode of late Neoproterozoic transpression in the southern
part of the Arabian-Nubian Shield (ANS). This area is
dominated by five main basement lithologies: gneisses,
metavolcanics, Ablah Group (meta-clastic and marble units)
and syn- and post-tectonic granitoids. These rocks were
affected by three phases of deformation (D1–D3). D1 formed
tight to isoclinal and intrafolial folds (F1), penetrative foliation
(S1), and mineral lineation (L1), which resulted from
early E-W (to ENE-WSW) shortening. D2 deformation
overprinted D1 structures and was dominated by transpression
and top-to-the-W (−WSW) thrusting as shortening
progressed. Stretching lineation trajectories, S-C foliations,
asymmetric shear fabrics and related mylonitic foliation, and
flat-ramp and duplex geometries further indicate the inferred
transport direction. The N- to NNW-orientation of both “insequence
piggy-back thrusts” and axial planes of minor and
major F2 thrust-related overturned folds also indicates the
same D2 compressional stress trajectories. The Wadi Yiba
Shear Zone (WYSZ) formed during D2 deformation. It is
one of several N-S trending brittle-ductile Late Neoproterozoic
shear zones in the southern part of the ANS. Shear
sense indicators reveal that shearing during D2 regionalscale |
