In a presentation to the December meeting of the Qatar Natural History Group (www.qnhg.org), Dr Christian Strohmenger, who is ExxonMobil Research Qatar’s geological adviser and team lead for the Qatar Centre for Coastal Research, gave a lively description of the unique sabkha which he has studied along the Abu Dhabi coastline in the vicinity of Al-Qanatir Island and at the Mussafah Industrial Channel.

For the average Gulf citizen, the term ‘sabkha’ summons up nothing more than visions of dreary, saline stretches of desert wasteland beside the sea where nothing grows, no animals live, and where drivers have to take great care to avoid getting bogged down on their way to the beach.

But for the geologist, sabkha teems with life and interest. Sabkha deposits have formed all the way along the eastern coast of the Arabian Gulf. The coastline of the Gulf, explained Dr Strohmenger, is constantly changing, with the north-west wind relentlessly shifting millions of tonnes of loose sand. In south-western Qatar in the last 6,000 years, he said, the sand has moved and extended the coastline seaward by some 15km. Studying modern day examples of geologic examples can help geologists to interpret features that were deposited millions of years ago.

Geologists, said the speaker, divide the coastal area into supratidal sabkha, intertidal where the microbial mats otherwise known as stromatolites occur, and lowermost intertidal to shallow subtidal which includes shallow lagoon and tidal-channel belts. Radiocarbon dates from some of the microbial mat samples give an age range of around 6,000 years before present (BP) down to 900 years BP.

The effects of climate change and tectonic activity also dramatically alter the coastline of the Gulf. To illustrate this, Dr Strohmenger provided a graphical presentation of sea-level changes over the last 18,000 years in what is known as the ‘Flandrian transgression’. The presentation showed glaciers on the Zagros Mountains in cold periods. As the climate changed through a series of arid to wet periods, rivers, freshwater lakes, dune fields and green valleys in the Gulf were shown constantly shifting and changing. Sea level was 2 to 3m higher than today 6,000 years ago. Dr Strohmenger showed that at that time, Qatar was connected to the rest of Arabia by just a very narrow strip of land.

Sea levels have risen and fallen over the millennia, and a slight sea-level fall can result in the original carbonate deposits being replaced by gypsum and anhydrite. Fine crystalline dolomite has been found within the layers formed by ancient microbial mats or stromatolites. The stromatolites thrive in the intertidal zone where they receive the water they require but avoid the gastropods (i.e. snails) which feed off them in the subtidal zone. As a result of this, stromatolites are excellent indicators for research into past sea levels in the Gulf.

A recent find of interest was the remains of a huge humpback whale, dating to some 6,000 years BP, within tidal-channel deposits overlying an ancient microbial mat layer.

For the geologist, said Dr Strohmenger, the Abu Dhabi sabkha is a national treasure for the UAE, with its unique microbial dolomite formation. Stromatolites, a primitive form of life which produce oxygen, are the oldest colonial life on Earth, and if scientists ever find life on Mars, he suggested, it is likely to be in a similar form to stromatolites.

Rob Ross, chairman of the Qatar Natural History Group and research colleague of Dr Strohmenger, presented him with the QNHG speaker gift as a token of appreciation for his talk.