Introduction
Jebel Hafeet mountain rises nearly 1300 m above sea level to the south of Al Ain. Tourits can enjoy one of the most beautiful and scenic mountain roads. Along the road you will find several parking places with wonderful view to surrounding country.
As a geocacher, you will enjoy several caches along the route. And of course this earth cache will give you some basic understanding of the geology behing it. The mountain is eroded such way that composing layers and different geological features can be easily observed at the surface. The earth cache will bring you to two different spots to show you three different geological features.
Geological overview
During the Palaeocene and Oligocene (65-23 million years ago) sea levels rose and fell several times. The coastal region was periodically covered with warm tropical waters. Limestone was formed from microscopic shells of plants and animals in shallow waters of the Tethys sea. After that the area became tectonically more stable but it began to separate from Africa along the Red Sea Rift about 25 million years ago and is still moving northwards at an average rate of 5 cm per year. As it moved north and was pushed under Eurasia the collision caused large scale folding of the limestones.
The limestones were folded in such way that it formed anticline type of fold. It is arch-like convex shape. Anticlines have such sequence of rock layers that become progressively older toward the center of the fold.
The Jebel Hafeet is large tertiary anticline about 26 km long and 4-5 km wide, extending from north to south. The mountain is asymmetric and in the eastern part is much steeper than the west side.
Stage 1 - N 24 05.878 E 055 45.499
At this stage you will have nice view on the green Mubazzarah valley. The valley lies to the west from the stage 1.
Look at south-east direction. You will see the limestone clif just behind the road. When you look at the clif details, you will notice dark-colored layers, very similar to limestone. This mineral is called dolostone, and it contains very high quantities of magnesium, which is why it is darker in color. There is a bit of controversy about it because although it is well-known how limestone forms, there are no clear modern environments where dolostone forms, as can be seen here, in very large and thick layers.
Questions to answer at stage 1
(1) There is information table at the stage. How many paragraphs are there (count the black dots) ?
(2) Can you guess which processes formed the valley through which you can see the green Mubazzarah ?
(3) What is width (bottom up) of dolostone layer in clif to south east from stage ?
Stage 2 - N 24 04.544 E 055 46.367
Numumilites are a type of foraminifera, or single-cell marine animals, shaped much like dirham coins and usually tiny in size. Ancient nummilites grew very large, however, and the ones you can find in cross-section here are actually the size of dirhams. They lived in shallow marine environments and are common in the limestones of the United Arab Emirates. At the stage 2 you can find limestone outcrop created during the road construction. Limestone here contains also other types of fossiles.
Questions to answer at stage 2
(4) At this stage you are approx. 90km from the nearest coast, and at the height of approx. 950 meters above sea level. What processes caused the marine fossils to move to this location ?
Tasks
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Sources of information and references:
http://www.wikipedia.org/
Geologic Featuresof the United Arab Emirates, Benjamin Jodan