Late Oligocene–Miocene provenance evolution of the Mahneshan Basin, NW Iran: An upper-plate tectonostratigraphic record of the Arabia-Eurasia collision

The Mahneshan Basin in northwest Iran preserves a >6 km-thick syn-orogenic sedimentary succession that records the late Cenozoic evolution of the Arabia-Eurasia collision. We integrate sandstone petrography, detrital zircon U Pb geochronology, and strontium isotope stratigraphy from the Lower Red, Qom, and Upper Red formations to reconstruct the sediment provenance history. Detrital zircon data indicate that the Lower Red Formation records continental deposition from the latest Oligocene to the earliest Miocene. Its lower part was derived from Precambrian basement rocks of the Takab Complex in the Sanandaj-Sirjan belt, whereas the upper part (22.2 ± 0.4 Ma) was mostly sourced from Eocene arc volcanic rocks, marking the first provenance shift. The overlying Qom Formation (19.6–19.4 Ma) records shallow-marine sedimentation with continued arc-related input. A second provenance shift occurred at the Qom to Upper Red Formation transition in the Burdigalian, reflecting an increased contribution from recycled crustal and sedimentary sources. The third provenance shift occurs in the middle Upper Red Formation (Serravallian), with renewed Miocene magmatic input and continued recycling of older crustal sources. Combined with published lower- and upper-plate tectono-stratigraphic data, our study documents a polyphase regional tectonic evolution involving: (i) latest Oligocene uplift and exhumation of the upper plate (Sanandaj-Sirjan Zone), near the plate suture; (ii) regional Oligo-Miocene subsidence with marine flooding reaching NW Iran in the early Burdigalian, followed by regional rapid transgression within the Burdigalian, coupled with localized upper-plate volcanism; and (iii) onset of widespread deformation, uplift, and exhumation from the middle Miocene.