Geoarchaeology as a tool to understand ancient navigation in the northern Persian Gulf and the harbour history of Siraf

Abstract

Historical texts and archaeological studies attest to the maritime and trade importance of the Persian Gulf since the Sassanid Empires. Nonetheless, there is a paucity of data regarding ancient navigation and the reasons for a shift in m aritim e trade from the western (e.g. Shatt-al-Arab) to eastern (Siraf) Persian Gulf by the Abbasid dynasty. For som e scholars, Siraf was occupied between 360 and 977 CE, after which tim e an earthquake entrained the dem ise of the city. However, it is unclear when Siraf was founded and how natural navigation conditions changed for ocean-going vessels in harbours of the NW Persian Gulf. To address this knowledge gap, we here present new geoarchaeological data from Siraf. Two anthropogenic facies were detected in drilled cores. They suggest that Siraf dates back to 2 BC-317 CE. After a hiatus, a second occupation phase began during the reign of Shapur II. Relative Sea-Level (RSL) fluctuations, climate change and Persian Gulf bathymetry all affected the possible nautical accessibility of this ancient Persian harbour. A fall in RSL, leading to a shortening of navigable water columns and amplified summer-time Shamal wind from 550 CE onwards possibly led to a loss in the im portance of Shatt-al-Arab and other ports in the western Persian Gulf. It appears to have m ade Siraf the best alternative for seafarers. According to the wind regimes, the best time for arrival and departure from Siraf was August and October, respectively. RSL rise and increasing coastal erosion during the winter-tim e Shamal winds led to the degradation of harbour potentialities and was possibly at the origin of econom ic decline and poorly adapted harbour works at Siraf during a 150-year period between 850 and 1000 CE.

Late Holocene relative sea‐level fluctuations and crustal mobility at Bataneh (Najirum) archaeological site, Persian Gulf, Iran

“…RSL reduction led to the deposition of the second brackish facies at 123 cm. By this time, accessibility to the northwest ports had been restricted via Ras‐e‐Motaf and the unique morphological shape of Shatt‐al‐Arab palaeo‐delta (Pourkerman et al, 2020). Navigation through Ras‐e‐Motaf became dangerous after the onset of summer time NW Shamal wind during ca.…”

“…The Zagros tectonic setting and halokinesis control the Persian Gulf basin and its coastal morphology. According to Pourkerman et al (2020) classification, the Persian Gulf coast can be subdivided into three morphological zones with different tide levels: (i) gently sloping marshland coasts with permanent rivers (Zone 1); (ii) diapiric uplifting coastal salt domes (Zone II) and (iii) rocky coasts with steep coastal slopes (Zone III) (Figure 1 and Table 1).…”

“…(a) The Persian Gulf bathymetry, coastal geomorphological classification and major structural elements of the Zagros fold‐and‐thrust belt (modified after Berberian, 1995; Hassanpour et al, 2020; Jahani et al, 2017; Jiménez‐Munt et al, 2012; Pourkerman et al, 2020). HZF, High Zagros Fault; MFF, Mountain Front Flexure; MZF, Main Zagros Fault; NFS, Nezamabad Fault system.…”

“…Without consideration of the main physical parameters, involving maritime navigation and port facilities, such as wind and surface current regimes, RSL history, climate changes and tectonic settings, it is not possible to fully grasp maritime trade and ancient harbours. Therefore, multidisciplinary geoarchaeological studies of ancient harbours and maritime structures help to understand the role of palaeoenvironmental changes in maritime trade activities and ancient civilisations (e.g., Benjamin et al, 2017; Marriner, Kaniewski, et al, 2017; Marriner & Morhange, 2007; Marriner, Morhange, et al, 2017; Marriner et al, 2010; Morhange et al, 2001; Pourkerman et al, 2020; Vacchi et al, 2020). The most important ancient harbours in the Persian Gulf were located on the Iranian coast until the 20th century AD (Potter, 2009).…”

“…The most important ancient harbours in the Persian Gulf were located on the Iranian coast until the 20th century AD (Potter, 2009). Coastal cabotage and the location of ancient harbours in the Persian Gulf were partly controlled by RSL changes, coastal morphology, the meteo‐marine context (e.g., Shamal winds) and sea‐surface currents (Pourkerman et al, 2020).…”