Biological Indicators Reveal Small-Scale Sea-Level Variability During MIS 5e (Sur, Sultanate of Oman)

Abstract

In this study we aim to document various coastal notches in Sur Lagoon (Oman) and interpret them regarding their use as sea-level indicator. We also unravel any short-term sea-level fluctuations, which are potentially preserved within the trace fossil assemblages of some of the notches. The oldest paleo notches stem from the last interglacial sea-level highstand of MIS 5e. This is concluded from cosmogenic nuclide dating of the fanglomerate bedrock in Sur Lagoon as presented in this study. All outcrops of paleo notches around Sur Lagoon were investigated in regards to the faunal distribution and notch shape. Furthermore, the absolute elevation of the notches and biological markers relative to msl were measured with a differential GPS.The bioerosional notch occurs at the same height around Sur Lagoon indicating that the area remained tectonically stable over the last 125 kyr. According to the elevation of the notch-apex, msl was 3.93 ± 0.12 m higher than today during the last interglacial. The distribution of boring and bioconstructing organisms relative to the notch shape displays at least one phase of short-term sea-level rise subsequent to the notch formation. The beachrocks that are associated with the bioerosion notches in Sur Lagoon show a larger grainsize than any sediment that is deposited in the lagoon nowadays. This, in combination with the occurrence of exceptionally high and deep abrasion notches, indicates that the coastline was more openly exposed and thus experienced a higher wave energy during the notch formation.

Collapse of Holocene mangrove ecosystems along the coastline of Oman

“…Differential movement of the lithosphere during the Quaternary along the Omani coastline is reported by Hoffmann et al (2013). Falkenroth et al (2020) identified a coastal notch in Sur, associated with the last interglacial sea-level highstand, at an elevation of 3.9 m, and confirm the tectonic stability of this area. The elevation of the paleo-shoreline testifies to differential crustal movement, as the coastal area north of Sur shows uplift for at least 800 ka (Mattern et al, 2018; Moraetis et al, 2018; Hoffmann et al, 2020).…”

“…Evidence for last interglacial shorelines in the area is published by Falkenroth et al (2020), where a coastal notch in Sur is described. This notch mapped at an elevation of 3.93 ± 0.12 m a msl correlates well with the deltaic sediments in Al Haddah that are found between 0 and 4 m a msl and those in As Sulayb that are mapped at approximately 1.8 m a msl.…”

The World Atlas of Last Interglacial Shorelines (version 1.0)

“…On the other side of the Arabian Peninsula, in the Gulf of Oman and the Persian Gulf, the only data inserted in WALIS 1.0 are those related to MIS 5a/5c proxies (Thompson and Creveling, 2021b). However, potential MIS 5e sea-level proxies are reported in the literature from Oman (Falkenroth et al, 2020(Falkenroth et al, , 2019, United Arab Emirates, Qatar (Williams and Walkden, 2002), and Iran (Oveisi et al, 2007;Pirazzoli et al, 2004). These stud-ies must be screened to gauge whether valid sea-level index points can be inserted in the subsequent versions of WALIS.…”

The World Atlas of Last Interglacial Shorelines (Version 1.0)

“…On the other side of the Arabian peninsula, in the Gulf of Oman and the Persian Gulf, the only data inserted in WALIS 1.0 are those related to MIS 5a/5c proxies (Thompson and Creveling, 2021b). However, potential MIS 5e sea-level proxies are reported in the literature from Oman (Falkenroth et al, 2020(Falkenroth et al, , 2019, United Arab Emirates, Qatar (Williams and Walkden, 2002), and Iran (Oveisi et al, 2007;Pirazzoli et al, 2004). These studies must be screened to gauge whether valid sea-level index points can be inserted in the subsequent versions of WALIS.…”