SUBTIDAL FORAMINIFERAL ASSEMBLAGES OF THE WESTERN PART OF THE SHATT AL-ARAB DELTA, KUWAIT, ARABIAN GULF

Abstract

The foraminiferal fauna of the subtidal and tidal creek sediments of the western Mesopotamian shelf comprises 46 species including 0.17% Textulariina (agglutinated forms), 22.2% Miliolina (porcellaneous forms), 0.45% Lagenina and 77.1% Rotaliina. Cluster analysis of quantitative data on the distribution of tests of foraminiferal species in samples distinguished three assemblages related to major salinity variations and physiographic setting: 1) a tidal creek assemblage, including a typical Nonion association similar to that mentioned by Murray (1991) (found in low salinity areas), 2) an assemblage distributed over the eastern offshore of Bubiyan Island and around the island of Failaka, facing the open sea of the Mesopotamian shelf, including an atypical Nonion association with shallow shelf, subtidal faunal elements (found over regions of relatively “normal” Gulf salinities, but still affected by fresh-water influxes from Shatt Al-Arab), and 3) an assemblage distributed on the southern offshore region of Bubiyan Island and on the shore facing Kuwait Bay (found in relatively turbid waters with almost “normal” salinities), including an Ammonia / Asterorotalia association. The Nonion association, characterizes estuarine and lagoonal environments in coastal regions subjected to meso- or macrotidal regime. The Ammonia / Asterorotalia association is usually found in the Indian Ocean in shallow shelves with normal marine conditions and in sediments rich in organic carbon. The most stress resistant species in the studied fauna are those adapted to low salinities: Quinqueloculina poeyana , Pseudononion japonicum , Ammonia cf. aberdoveyensis and Ammonia elegans . They are conspicuously abundant in the tidal creeks. “Open marine” subtidal forms, which are less stress resistant, are Spiroloculina rotundata , Asterorotalia dentata and Challengerella bradyii. Both seem to favor Kuwait Bay.