The opening and closure of marine gateways have been suggested to substantially affect ocean current circulations and global climatic changes. In the Miocene, the closure of the Tethyan Seaway, which connected the proto-Mediterranean Sea with the Indian and Atlantic Oceans, blocked thermohaline exchanges between them and possibly caused a major climate change in the Middle Miocene Climatic Transition. However, the timing, process, and forcing mechanism of the closure of this seaway are controversial. To address this question, we focus on the chronology and sedimentary facies of Miocene strata in the Zagros foreland basin in the Western Iranian Plateau. Based on magnetostratigraphy and biostratigraphy, we establish a chronology of 17 to 10 Ma for the studied Miocene strata and constrain the timing of the permanent closure of the northwestern segment of the Tethyan Seaway to 12.8 Ma. By comparison with global sea-level fluctuations, we suggest that middle Miocene marine transgressions and regressions in the studied region were mainly driven by global climatic change through its control on the growth and decay of ice sheets and thus sea level changes. Our detailed depositional sequence analysis exhibits 100-kyr Earth's eccentricity cycles of marine transgressions and regressions between 15.0 and 12.8 Ma implying they were controlled by astronomical factors. Moreover, the Tethyan Seaway experienced stepwise evolution changing from partially opened seaway, restricted marine connection, intermittent connections, to permanent closure in its northwestern segment during the early and middle Miocene.

有人建议打开和关闭海洋通道会严重影响洋流环流和全球气候变化。在中新世中，将原地中海与印度洋和大西洋连接起来的特提斯海道的封闭，阻止了它们之间的热盐交换，并可能导致了中新世中期气候变化。但是，关闭该航道的时间，过程和强迫机制存在争议。为了解决这个问题，我们关注伊朗西部高原Zagros前陆盆地中新世地层的年代学和沉积相。根据磁地层学和生物地层学，我们为研究的中新世地层建立了17到10 Ma的年代，并将特提斯海道西北段的永久性封闭时间限制为12.8 Ma。通过与全球海平面涨落进行比较，我们认为研究区域中的中新世海侵和海退主要是通过控制冰盖的生长和衰减以及全球海平面变化而受到全球气候变化的驱动。我们详细的沉积层序分析显示了100海里的地球偏心周期的海侵和15.0至12.8 Ma之间的回归，表明它们是受天文学因素控制的。此外，特提斯海道经历了逐步演变，从部分开放的海道，受限制的海洋联系，断续的联系，