Palaeoenvironment,palaeoclimate and sea-level changes in the Shuaiba Lagoon during the late Holocene (last 3.6 ka),eastern Red Sea coast,Saudi Arabia

Abstract

Multi-proxy investigations of sediment lithology, geochemistry, benthic foraminifera, and δ¹⁸O and δ¹³C of Elphidium striatopunctatum were carried out on a sediment core SHUA3 (2.2 m long) spanning the last 3.6 ka and recovered from Shuaiba Lagoon, eastern Red Sea coast. Results showed that the interval before 1500 BC was deposited under supratidal to sabkha environments as indicated by the absence of benthic foraminifera and predominance of clastics enriched in terrestrial materials due to a relative lowering of sea level accompanied with arid conditions. From 1550 BC to the top of the core, the benthic species variations showed progressive depositional environmental changes from subtidal to intertidal conditions. Relative abundance of Sorites orbiculus co-varied with the reconstructed palaeo-tidal elevation, δ¹⁸O and δ¹³C values suggesting its sensitivity to climatic changes in the lagoon. δ¹⁸O and δ¹³C showed intervals of depletion at 350 BC, the beginning of the 1st millennium, AD 400 and AD 700 due likely to arid conditions that led to low evaporation and rapid water circulation. These are interleaved with intervals of enrichment at 150 BC, AD 200 and AD 600, due likely to warm conditions that led to high evaporation as testified also by changes in both palaeo-tidal elevation and Sorites orbiculus abundance. These proxies reached their highest and most prolonged levels during the AD 800–1550 interval, indicating warm conditions corresponding to the world ‘Medieval Warm Period’. Immediately after this period, the arid conditions of the ‘Little Ice Age’ prevailed throughout the AD 1550–1850 interval, and this was succeeded by the present warming conditions.