Miocene Sedimentary Characteristics and Provenance Analysis in the Lurestan-Khuzestan Region,Southern Iran
[Objective]The collision of the Arabian-Eurasian Plates led to the formation of the Zagros orogenic belt and related foreland basin. The gradual filling of the Zagros foreland basin resulted in the retreat of the Neo-Tethys Ocean in the Zagros region,which caused the transition from the marine to terrestrial environments. This process pro-vides the chance to explore the demise of the Neo-Tethyan Ocean in the Middle East.[Methods]In this study,we conducted detailed stratigraphy,sedimentology,sandstone petrography,and detrital zircon U-Pb age determination on the Miocene sedimentary strata in the Lurestan and Khuzestan regions of the Zagros Mountains in southern Iran,which provide new constraints on the filling of the Zagros foreland basin and the regression process of the Neo-Tethys Ocean in the Zagros region.[Results]The Agha Jari Formation in the Lurestan region is characterized by large-scale,medium-to-thick layered sandstones interbedded with mudstones. Sedimentary environment analysis suggests that it has been formed in a fluvial environment. The sandstone petrography shows a significant number of metamor-phic clasts. Combined with the detrital zircon U-Pb age peak of Jurassic～170 Ma,the Agha Jari Formation in the Lurestan region is found to be derived from the Sanandaj-Sirjan zone to the north. The Agha Jari Formation in the Khuzestan area is a large set of thick mudstone beds,thick mudstone interbedded with sandstone,thick sheeted sandstone interbedded with mudstone,and sand-mudstone interbeds. The sedimentary environment analysis shows that it has been formed in a transitional deltaic environment. The sandstone modal composition indicates that the clasts of the sedimentary rocks occurred. The detrital zircon ages show Mesozoic ages,comparable with the Zagros Fold-and-Thrust Belt. Thus,they have been mainly recycled from the sedimentary strata in Zagros Fold-and-Thrust Belt. Based on the underlying Gachsaran-Mishan Formations,which are composed of shallow marine limestone and evaporite,the Agha Jari Formation represents the regional youngest marine sedimentation,recording the transition from the marine to the terrestrial environments. The calcareous nannofossil analysis from the underlying Mishan For-mation yield the youngest age of the Early Miocene. Considering the other biostratigraphic studies,the age of the Agha Jari Formation is constrained to be no earlier than the Miocene. Therefore,based on the sedimentary and bio-stratigraphic studies on the Agha Jari Formation in the Khuzestan region,the demise of the Neo-Tethyan Ocean in the Zagros region has been constrained by no earlier than the Miocene,with a trend from the northwest to the southeast.[Conclusions]Combined with regional paleogeography and provenance analyses on the Miocene strata in the Zagros orogenic belt,the gradual uplift of the Zagros orogenic belt occurred after the Arabia-Eurasia collision. The uplifted Zagros orogenic belt has been eroded to provide the clastic materials for the Zagros foreland basin. As a result,the re-gression of the Neo-Tethys Ocean in the Zagros region is controlled by the continual filling in the foreland basin. This paleogeography of northwest-southeast regression of the Neo-Tethyan Ocean existed no later than the Early Miocene.
Neo-Tethyan OceanZagrosAgha Jari Formationsedimentary environmentregression
万方数据
维普
