Fauna Assemblages and Depositional Environment of Recent Deposits in Al-Salhiya Island, Southeastern Part of Basrah Governorate, Southern Iraq

The present study was carried out to give a clear view of the sedimentological characteristics, and to identify the types of faunal assemblages in Al-Salhiya Island. The results showed two types of sediment texture: Sandy silt deposits and Silt deposits. Sandy silt deposits are dominant at most depths in the study area. The graphic mean size of the sediments indicated that the sediments are soft and reflect the nature of the sedimentation environment, which was calm and had a low transport capacity. Also, the statistical size parameters of the sediments indicated that the region is under the influence of marine tidal environments, shallow brackish marsh environments, and fresh marsh-fluvial environments. This study dealt with the fauna assemblages. It is revealed through the distribution and spread of these groups that the most important species identified for Foraminifera are Ammonia beccarii, Ammonia tepida, and Eliphidium inertum, whose prevailing presence together and in most of the depths indicated brackish-shallow water environment, with varying temperatures and estuarine environments. Also, the species Quinqueloculina poyana and Spirocolina laevigata are identified. One species of Ostercoda was identified: Cyprideis torosa. The presence of this type indicates a shallow, lower estuarine-marine environment. This study identified 8 species of the Gastropoda, most of which live in lower estuarine-marine environments. This indicated that the area was affected by tidal currents and marine progress due to its proximity to the coastline of the Shatt al-Arab. Also, this study showed two types of Pelecypoda that are widely distributed and common in all depths, their presence together with the Gastropod and Pelecypoda debris reflects the effectiveness of tidal currents in transporting them to the area.