The Upper Jurassic Garedu Red Bed Formation of the northern Tabas Block: elucidating Late Cimmerian tectonics in east-Central Iran

Abstract The Garedu Red Bed Formation (GRBF) of the northern Tabas Block (Central-East Iranian Microcontinent, CEIM) is a lithologically variable, up to 500-m-thick, predominantly continental unit. It rests gradually or unconformably on marine limestones Esfandiar Subgroup (Callovian–Oxfordian) and assigned Kimmeridgian–Tithonian. In lower part, it consists pebble- boulder-sized conglomerates/breccias composed limestone clasts intercalated with calcareous sandstones, litho-/bioclastic rudstones lacustrine carbonates. Up-section, sharp-based pebbly sandstones red silt-/fine-grained braided river origin predominate. Palaeocurrent data suggest principal sediment transport from west east lateral interfingering GRBF greenish marls Korond at eastern margin Block. Westwards, grades into playa deposits Magu Gypsum Formation. colours common calcretes arid semi-arid climatic conditions. onset deposition indicates major geodynamic change compressive tectonics Late Cimmerian Tectonic Event (LCTE), being strongest When traced southwards, same tectonic event expressed by extension, indicating shift in style along boundary fault between Lut blocks. complex Upper Jurassic facies distribution as well spatio-temporal changes regime block-bounding faults are explained counterclockwise vertical-axis rotation CEIM Kimmeridgian. block boundaries accommodated right-lateral strike slip, transpressional today’s transtensional southern segments faults. Rotation occurred within bracketing transcurrent continued Early Cretaceous, finally resulting opening narrow oceanic basins encircling CEIM. Palaeogeographically, part suite bed formations not only present CEIM, but also Sanandaj-Sirjan Zone (NW Iran), northeastern Iran beyond, inter-regional instability, uplift erosion under (semi-)arid conditions across Jurassic–Cretaceous boundary. Thus, even if our model successfully explains rotations, motions for basic cause LCTE still remains enigmatic.