Constraining the timing of Arabia-Eurasia collision in the Zagros orogen by sandstone provenance (Neyriz, Iran)

The Zagros orogen, formed by the collision of the Arabian and Eurasian continental margins, represents one of the largest and richest oil and gas provinces in the world. The Zagros fold-thrust belt records collision and convergence along the Neotethys suture zone. By coupling field observations, sandstone modal analysis, U-Pb zircon dating, and Hf isotopic data from the Upper Cretaceous to Pliocene sedimentary succession of the Neyriz region, this paper documents several major provenance changes that allow us to propose a refined scenario for the Zagros orogeny. An ophiolitic complex dated by detrital-zircon U-Pb geochronology as ca. 95 Ma provided detritus to Upper Cretaceous-Paleocene strata deposited along the northeastern margin of the Arabian lower plate (ophiolite provenance). Yet, on the southwestern margin of the Eurasian upper plate, upper Paleocene-lower Eocene strata indicate provenance from Mesozoic magmatic rocks yielding zircons dated as ca. 240 Ma and 170 Ma as well as the recycling of clastic rocks. Since the early Miocene, the sedimentary basin located on the Arabian plate received both ophiolitic detritus and magmatic-arc, recycled clastic, and axial-belt metamorphic detritus from Eurasia. U-Pb ages of detrital zircons reflect polyphase magmatism at 170 Ma, 95 Ma, and 40 Ma on the Eurasian active margin. Our results indicate that progressive accretion, uplift, and exhumation of the Zagros orogen was well under way by the beginning of the Miocene in the Neyriz region. Literature data from adjacent regions suggest that the Arabia/Eurasia collision may have occurred diachronously and later in the Kermanshah and Lurestan areas to the north.

Supplemental Material: Constraining the timing of Arabia-Eurasia collision in the Zagros orogen by sandstone provenance (Neyriz, Iran)

Table S1: Detrital zircon U-Th-Pb age and Th/U ratio result from Cenozoic sandstones of Zagros Orogeny.

Supplemental Material: Constraining the timing of Arabia-Eurasia collision in the Zagros orogen by sandstone provenance (Neyriz, Iran)

Table S1: Detrital zircon U-Th-Pb age and Th/U ratio result from Cenozoic sandstones of Zagros Orogeny.

The Nowdan anticline of the Zagros orogen as a geoheritage ‘window’ into the late Mesozoic–Cenozoic evolution of the African–Arabian continental margin

Geological heritage can contribute to our understanding of the long-term evolution of important sectors of our planet. Cretaceous–Neogene rocks (chiefly carbonates) crop out in the Nowdan anticline of the Zagros orogen. Field investigations have permitted the establishment of 10 key localities (stratigraphical reference sections) that represent these rocks within this anticline, which is a single large geosite. The formations are related to the main phases in the evolution of the northeastern sector of the African–Arabian continental margin. For instance, carbonate rocks of the Asmari Formation mark changes in the affinity of the study area, from the African–Arabian plate to only the Arabian plate, separated in conjunction with Red Sea rifting during the Oligocene. Information on the palaeogeographical changes is really precious to geoscientists and geotourists alike, and contributes to the great value of the Nowdan anticline geosite. Evidence from the latter, as well as from a few other places (i.e., the Mountainous Adygeya geodiversity hotspot in Russia, the North Coast of São Paulo in Brazil and the possible Gondwanan geopark in Namibia) illustrates the necessity of distinguishing a palaeomapping subtype in palaeogeographical characterisation of geological heritage.