Monday, 20 January 2014

Sun, Sand and Sabkhas by Clive Mitchell

Me [BGS Industrial Minerals Specialist
Clive Mitchell] sampling dune sand
The BGS have worked in the United Arab Emirates (UAE) for over 10 years, in which time we have produced new geological maps for the whole country and also studied the mineral resources, urban geology and geohazards. The UAE is only the second country in the world to have fully contiguous digital geological map coverage (the first country was the UK and the BGS did both!). For my part I have lead several projects on the limestone and dimension stone resources. All of the maps and reports are available from the UAE Ministry of Energy which is based in Abu Dhabi.
Burj Khalifa framed by the Emirates
Towers, Dubai

I recently spent 10 days in the UAE to undertake some fieldwork and silica sand sampling for a glass company. Just before this I took part in the MENA Mining conference in Dubai. MENA is the Middle East and North Africa region. Reading the opening address from H.E. Dr Matar Al Neyadi, Undersecretary at the Ministry of Energy, I was surprised to learn that this region covers an area of over 11 million km2 and has a population of 317 million (larger than Europe with less than half the population). MENA is not well known for its mineral production with little in the way of metal production. It is relatively well known for its production of industrial minerals such as phosphate, gypsum and potash. What I found encouraging was the presence of representatives from Egypt, Libya and Iraq, all there to promote their natural resources and reiterate that their countries are ‘open for business’. 


BGS Geologist Andy Farrant
After four days in Dubai it was definitely time to get out of Dodge and head off west to the desert. I was working with my BGS colleague, Andy Farrant, an experienced mapping geologist who lead the work to map the western part of the UAE. Read about our work on the BGS Geological mapping in the United Arab Emirates pages. Our base was the charming Dhafra Beach Hotel in Jebel Dhanna (about 350km west of Dubai) complete with air con (vital), dehumidifier (even more vital!) and a friendly lizard. Incidentally, yes there is a beach by the hotel but its attraction is diminished somewhat by the presence of the nearby oil refinery at Ruwais. 

Zeugen - dune sandstone with gypcrete cap rock
Our mission was to find silica sand suitable for glass production (no further details I’m afraid as this was a commercial job). Suffice it to say we visited lots of localities with promising looking quartz-rich sandstone and sand deposits.

It was great to get out of the office and back to real geology for a change. Dusted off my hand lens, GPS and sampling gear. Along the way I was introduced to some of the UAE’s hidden gems. Such as the Zeugens standing proud over the Sabkhas, fossil bone beds stuffed full of bones, oyster shell and turtle carapace, and the 8 million year old elephant tracks in Miocene limestone pavement. Wow! 

8 million year old elephant tracks in
Miocene limestone pavement
One strong feature, apart from sand dunes, is the presence of Sabkhas. These are found everywhere where water has interacted with the surface. Salt is dissolved from the ground, brought to the surface by the intense evaporation and deposited as large crystals which disrupt the surface forming a strange buckled landscape.

Back to the sand! Dunes are everywhere getting progressively more quartz rich and larger as we worked our way south away from the coast. Modern dunes overlay quaternary palaeodunes which in turn overlay Miocene palaeodunes. All formed from the same sand worked and reworked from that blown inland from the Arabian Gulf when the sea levels were lower or deflated from older Miocene rocks. Ultimately the quartz sand came from the mountainous highlands of Saudi Arabia where rivers brought it down into the Arabian Gulf around 8 million years ago.

'Camel Jam' on the road to the Liwa, Al Gharbia, UAE
How could I forget the camels?! These are the pride and joy of the local Emiratis who jealously guard them from vantage points in their 4x4s. I would imagine moving your camels over sand dunes would be very slow. Hence we were treated to frequent ‘Camel Jams’ on the roads.

One blessed relief, the desert is too dry for most insects and we were free of these usual field work pests!


Whoever said desert geology is boring, surely it’s all just sand isn’t it? Well, there is plenty of exposure in the interdune areas which are surprisingly free of modern dune sand. In addition, in the same way that Eskimos are claimed to have over 100 words for snow, the BGS have managed a dozen for sand! Aeolian sand, low dunes, sand sheet, ribbed sand sheet, dune ridge, Barchan dunes, Mega-Barchan dunes, Zibars dunes, palaeo dunes (carbonate- or quartz-rich), star dunes and beach ridge deposits (I’ve probably missed some out!).


Etihad Rail line, Al Gharbia, UAE
One last note, this region of the UAE is currently witnessing the rapid construction of a very large infrastructure project. Etihad Rail is putting in place a rail line that will not only link all the major cities in the UAE, it will also link the UAE with Bahrain, Kuwait, Qatar, Oman and Saudi Arabia (Gulf News 29 October 2013). It is incredible to learn that this network will be completed by 2018!

Clive Mitchell
Twitter@CliveBGS

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