Sedimentological, geochemical, and paleontological investigations of the coastline of northeastern Oman have provided the authors with an in-depth insight into Holocene sea levels and climate conditions. The spatial distribution and species assemblage of mangrove ecosystems are analyzed. These ecosystems are sensitive to changes in sea level and precipitation and thus reflect ecological conditions. The close proximity to archaeological sites allows us to draw conclusions regarding human interaction with the mangrove ecosystems. Our interdisciplinary inquiry reveals that the mangrove ecosystems along the east coast of Oman collapsed ~6000 cal yr BP on a decadal scale. There is no sedimentological evidence for a mid-Holocene sea-level highstand. The ecosystem collapse was not caused by sea-level variation or anthropogenic interferences; rather, it was the consequence of reduced precipitation values related to a southward shift of the Intertropical Convergence Zone. This resulted in a decrease of freshwater input and an increase in soil salinity. Further, the aridification of the area caused increased deflation and silting up of the lagoons.

In the original publication of Decker et al. (2020), Figures 6, 7, and 8 were incorrectly labelled. The correct figures and their captions are reproduced below: Figure 6. The shell midden south of Ras ar Ru'ays showing the underlying fluvial deposits. The stars mark the 14 C dates of molluscs; the blue triangle indicates the D-GPS measured height a msl.

No abstract

In this paper, we demonstrate how subfossil mangrove wood can be used to elucidate the timing of past tsunami events. Although tsunamis generated by submarine earthquakes along the Makran subduction zone in the Arabian Sea are not unusual, rigorous age documentation is generally lacking. The best known is the only instrument-recorded tsunami, which affected the coastlines of Iran, Pakistan, India, and Oman in November 1945. Eyewitness accounts of the effect along the Oman coastline assert that this tsunami was not destructive. However, a 25-cm-thick shell layer in the lagoon adjacent to the city of Sur was attributed to the 1945 tsunami, although dating of the shell deposit proved difficult, and the radiocarbon dates of mollusk shells were regarded as unreliable. Here, we reinterpret the age of this tsunamigenic layer based on the new discovery of parallel-oriented woody axes in the sedimentological context of the tsunami shell layer in the Sur lagoon. The woody axes were analyzed anatomically and identified as pertaining to the gray mangrove Avicennia. Radiocarbon dating of the wood (905–722 cal BP), along with sedimentological investigations, suggests that the deposition of the woody axes should be attributed to an older tsunami event that occurred ca. 1000 years ago, which has been documented at other locations along the Arabian Sea coastline. From this, we conclude that mangroves grew in this lagoon at that time. Very little is known about ancient mangrove distribution in this region and, so far, no records have been provided for this time window at this site. We also deduce that the tsunami event that occurred one millennium ago must have been substantially more severe than the one in 1945. More accurate dating of tsunamigenic events will aid in calculating the recurrence intervals and magnitude of tsunamis generated along the Makran subduction zone.