Sedimentary, Mineralogy and Biofacies of Holocene deposits of Al-Hammar and Al-Hewaiza marshes near Qurna

Abdalrazak A., Albadran B., Pournelle J.

The southern part of Mesopotamia is an important area, it is considered as an ambiguous environment during the Quaternary period. Two sites were chosen for boreholes in the southern part of Mesopotamia on both sides of the Tigris River before its confluence with the Euphrates River north Qurna. Site one is on the east side of Al-Hammar marsh, site two is on the west side of Al-Hewaiza marsh. The sampling was carried out during October 2014 and February 2015.  Sedimentology, mineralogy and fauna analyses were done to a depth about 3 – 3.5m in order to distinguish the paleoenvironments during the Holocene period. Results of grain size analysis indicate five textures; Silt, Silty sand, Sandy silt, Mud, and Clay. Silt percentage is dominant in the sediments of all the sites. Mineral analysis shows that the minerals are; Calcite, Quartz, Dolomite, Feldspar and Gypsum, Calcite is a dominant mineral in the area of the study. The clay minerals in the area of the study are; Kaolinite, Illite, Montmorillonite, Chlorite, Palygorskite and mixed layers of Montmorillonite – Chlorite, and Illite – palygorskite. According to fauna assemblages, three Biofacies were identified on every site. In site one, a light gray layer of 5cm in thickness at depth 252 – 257cm contains a lot and diversity of fauna assemblage, clay percentage is 97% and calcite percentage is 75%, considered this layer belongs to marine transgression during 6000 yrs. B.P based on fauna assemblages. Few numbers of fauna assemblages indicate a freshwater environment and large numbers indicate brackish, Tidal flat, Lagoonal and shallow marine environments. The sea – level of the Arabian Gulf was 3m above present level according to Lambeck (1996), when 2m added to 3m because the ground level of the area was 2m below the actual level due to the tectonic or depositional reasons, the sea – level of the Arabian Gulf, after adding 5m to the actual level, covers the area of study and go much further than that.