Quaternary calcareous hard rocks and the associated sediments in the intertidal and offshore zones of Kuwait

Abstract

The geomorphological and petrographical characteristics of the Quaternary calcareous hard rocks in the offshore and intertidal zone of Kuwait, northern Arabian Gulf, were investigated. These rocks can be divided into three types, (1) submerged calcareous hard layers, (2) beachrocks and (3) lithified intertidal terraces. Submerged calcareous hard layers usually cover a submarine terrace about 15 m below present sea level. This hard rock is generally underlain by an uncemented oolitic sand and overlain by Holocene mud which reaches up to 13 m in thickness. Submerged calcareous hard layers are generally lithified allochemical limestone. Four types were recognized: biosparite, biomicrite, oosparite and oomicrite. Beachrocks outcrop over distances of several hundred metres along the coast of Kuwait. They are partially eroded by mechanical and biological processes. The field occurrences and petrography of the beachrocks vary from place to place. However, two main types were recognized: quartzitic and calcarenitic. The occurrence of each type is related to the nature of the coastal bedrock from which the framework grains of the beachrocks were derived. Lithified intertidal terraces are almost flat benches of hard calcareous layers which are petrographically similar to beachrock, but genetically different. They are developed as a result of intertidal lithification of the surficial part of the Quaternary semiconsolidated coastal terraced deposits. Textural and mineralogical investigations of the intertidal sands indicate that these sands are derived from the coastal deposits. High-energy waves are responsible for the good sorting of these sands along the southern coast.