Stepwise Closure of the Tethyan Seaway and Its Impact on Earth System Interactions During the Cenozoic
Introduction: A Key Period for Earth System Studies
The Cenozoic era stands out as a pivotal geological period characterized by profound transformations in the lithosphere, hydrosphere, atmosphere, and biosphere. It witnessed the rapid rifting of the Gondwana Supercontinent, the opening and closing of oceanic straits, the reorganization of oceanic and atmospheric circulations, the transition from a greenhouse to an icehouse climate, and the rapid succession of flora and fauna. These dynamics make the Cenozoic an ideal era for exploring the coupling between Earth’s various spheres. In this review, we focus on the Tethyan Seaway, examining its closure process, timing, and its cascading effects on the biosphere, ocean circulation, and atmosphere from an Earth system science perspective.
Closure Time and Process of the Tethyan Seaway
The Tethyan Seaway, a critical marine passage connecting the Indian Ocean, the proto-Mediterranean, and the Atlantic, underwent a stepwise closure from the Oligocene to the late Middle Miocene (34–12.8 Ma). During the Oligocene, the Tethyan Seaway effectively connected low-latitude regions, facilitating the exchange of waters between the Indian Ocean, the proto-Mediterranean, and the Atlantic. By the early Miocene (21–19 Ma), as the African-Arabian Plate converged with the Eurasian Plate, the connectivity of the Tethyan Seaway diminished by 90%. The Mid-Miocene Climate Optimum (17–15 Ma) was marked by a coastal lagoon-dominated environment with occasional shallow marine intercalations. From 15 to 12.8 Ma, the seaway transitioned to a predominantly continental environment with brief, periodic marine incursions exhibiting a quasi-100,000-year cycle. By 12.8 Ma, the Tethyan Seaway had permanently closed.
Impact on the Biosphere
The closure of the Tethyan Seaway had significant implications for the biosphere. Marine invertebrates such as gastropods and echinoderms gradually migrated from the proto-Mediterranean to the Indian Ocean and the Western Pacific as the seaway closed. For mammals, while sporadic migrations between Africa-Arabia and Eurasia occurred in the early Miocene, large-scale two-way migrations became prominent after 18–17 Ma. This was due to the Tethyan Seaway’s transition to a coastal lagoon environment, which no longer acted as a significant barrier. African primates, proboscideans, hyraxes, and tubulidentates migrated to Eurasia, while Eurasian carnivores, rhinos, pigs, ruminants, lagomorphs, and certain rodents migrated to Africa.
Impact on Ocean Circulation
The closure of the Tethyan Seaway altered ocean circulation. Warm, saline waters from the low-latitude Tethys Sea, which previously infused the Atlantic and southern Indian Ocean, were reduced. This reduction diminished the meridional heat transport from low latitudes to the southern high latitudes, contributing to the expansion of the East Antarctic ice sheet and cooling of Antarctica.
Impact on Atmospheric Circulation
The retreat of the Tethyan Seaway and its subsequent closure, along with the uplift of the Iranian Plateau, influenced atmospheric circulation, particularly the South Asian monsoon. Geological records indicate that the South Asian monsoon strengthened between 15 and 13 Ma, coinciding with the permanent closure of the Tethyan Seaway, leading to enhanced upwelling along the Arabian coast and intensified monsoon systems.
Conclusion
The closure of the Tethyan Seaway, driven by tectonic convergence of the Arabian and Eurasian Plates and modulated by sea-level fluctuations, had far-reaching impacts on Earth’s biosphere, ocean circulation, and atmosphere. This case study underscores the intricate interactions between Earth’s deep and surface processes, highlighting the importance of studying seaway dynamics in understanding global environmental change.
Authors: Jimin Sun¹,²*, Jingeng Sha³, Shiqi Wang⁴
¹ Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China
² College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
³ Nanjing Institute of Geology and Paleontology, Chinese Academy of Sciences, Nanjing 210008, China
⁴ Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing 100044, China
*Corresponding author: E-mail: jmsun@mail.iggcas.ac.cn
Citation: Sun J M, Sha J G, Wang S Q. Stepwise closure of the Tethyan Seaway and its impact on the Earth’s multi-sphere interactions during the Cenozoic. Chinese Science Bulletin, 2024, 69(2): 184–199. doi: 10.1360/TB-2023-0154
doi: 10.1360/TB-2023-0154
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