The upper Batinah Complex, Oman: allochthonous sediment sheets above the Semail ophiolite

Abstract

The upper Batinah Complex consists of allochthonous sedimentary sheets that structurally overlie both the Semail ophiolite and its cover of mélange (lower Batinah Complex). Sequences represent a former sedimentary transition across the outer part of a passive Mesozoic continental margin. From proximal to distal, units include redeposited quartzitic sandstones and shallow-water limestones, large carbonate buildups floored by Triassic mafic lavas, and pelagic radiolarites or hemi-pelagic calcilutites also underlain by Triassic mafic lavas. Sheets of these upper Batinah Complex sequences were emplaced onto the upper surface of the Semail ophiolite in Late Cretaceous time, during or soon after the advance of the Semail Nappe onto the Arabian margin. Emplacement was along subhorizontal fault zones, with sheets of distal facies followed by successively more proximal sheets. Structural style suggests a low overburden during deformation, with ductile flow of argillaceous material but more brittle behavior of other lithologies. Large recumbent folds are present. Fold orientations imply sheet transport from between northeast and southeast.We conclude that the Batinah sheets represent part of the passive margin to a continental mass originally northeast of the main Arabian margin, but which is no longer present. We favour high-level gravity emplacement of Batinah sheets, and argue against trench accretion as an emplacement mechanism for either the sheets or the Semail Nappe itself.