The Huqf – Oman.

Here in UK over the last couple of days it has been quite warm. It is probably what was called summer when I last lived here, but you wouldn’t think so listening to the dire prognostications coming from the various news outlets.

This is what hot looks like:

The Huqf – Oman. from my files.

See this link from the Geological Society of Oman:  The Huqf.

The Huqf Uplift

Contribution by Alan Heward for the Geological Society of Oman: 

The Huqf area is a special one for geologists because there are rocks to look at from almost all of Oman’s geological history. This is possible because of the Huqf’s location near the eastern edge of the Arabian Plate which has kept it up-lifted through long periods of geological time.
 
The oldest rocks in the area are dated using mineral isotopes at about 730 million years. These are basement rocks, a type of granite, which formed deep within the earth’s crust from molten rock. Granite is a type of igneous rock. As the years went by, the basement rocks became covered in layers and layers of rocks, each layer being younger than the one before. These rocks that are made up of lots of fragments of weathered rock or shell fragments, are sedimentary rocks. Often they have fossils or features which give clues about how they formed.
 
The Huqf area has not always been a desert. At one time, about 300 million years ago, the rocks show evidence that ice sheets covered the area. At other times, it was under a shallow tropical sea. The layers left behind by these seas often contain fossils, but the fossils vary a great deal over time. The oldest fossils are mound structures made by mats of algae, which are called stromatolites. Younger fossils include wonderful tropical shells, such as the rudists bivalve. At yet another time, the area was fairly arid, but with big rivers flowing through. Fossil soils and trees occur in these layers. Each type of climate left behind its own particular pattern of layers of rocks which geologists interpret by looking at what goes on today in places with a similar environment.
 
In the 1950s, geologists began to study and map the region. They used their understanding of the fossils and rock layers present in the Huqf to help them drill for oil at Fahud, Ghaba and Haima. They found that the rock layers which produce oil from deep below the ground, are the same as those that can be seen at the surface in the Huqf area. So when oil company geologists want to understand the characteristics of the layers of rocks that make up an oil or gas reservoir, they often visit the rocks in the Huqf. Other geologists and students from Sultan Qaboos University and other universities around the world also visit this area with its fascinating geology.

Tawi Atayr: A sinkhole located in Al-Qarā Mountains Dhofar (more).

More from Tawi Atayr – unfortunately it was the wrong time of day, so shadows in the sinkhole were very dark. It was also before the monsoon hits, so everything is brown & tinder dry.
The metal rusted & broken frame seen on the last image, was for taking water from the bottom of the sinkhole during the summer months. During severe monsoon periods, this place can fill with water, then join the deluge that pours down Wadi Darbat towards the sea; such as when Cyclone Mekunu caused flash flooding earlier this year.

Getting there & seeing the place was great fun (even if rather precarious when venturing near the edge and away from the installed viewing area)  but needs must for photography, as long as one is sensible.

Tawi Atayr: A sinkhole located in Al-Qarā Mountains Dhofar.

 

Two images of a water run-off channel that drops into the Tawi Atayr sinkhole. The one on the right diffused, because I liked the look when printed. On the left I used a lens that has a slight softness around the edges: not everything needs to be ultra sharp.

Tawi Atayr: A sinkhole located in Al-Qarāʾ Mountains Dhofar.

The name roughly translated from Arabic means the “well of the birds” appropriate because it is populated by many birds whose song can be heard seemingly from all directions, when approaching the area of this sinkhole.
Its surface measurement is approximately 130m in a NE-SW direction and about 90m in NW-SE direction with a vertical depth of around 210m. Halfway down it narrows to an almost circular hole of about 60m in diameter.
Opinions differ as to its formation, either erosion exacerbated by fissures opened when the rock freezes or a collapsed cave system.
At the bottom there is a cave passage in a north-eastern direction, located at groundwater level and half-filled with water. To my knowledge, this passage has not yet been explored, it is possible that it leads to Wadi Darbat and the sea which is only 10km to the south.

Al-Hajar Mountains.

Al-Hajar Mountains.

The Al Hajar stretch for about 700 km across the north of the country and rise to over 3,000m (Jebel Shams – mountain of sun) from the coastal plain. Sediments at the core were mainly laid down during the Late Permian to Late Cretaceous in the Tethys ocean basin that had resulted from the break-up of Gondwana.
The Arabian Plate collided with and pushed against the Iranian Plate, resulting in mountains chiefly made of Cretaceous limestones and ophiolites.

Rock outcrops in the Al Hajar Mountains, the Huqf and Dhofar span about 825 million years and includes at least three periods when the country was covered by ice.
Oman, located at the south-east corner of the Arabian plate, is being pushed slowly northward, as the Red Sea grows wider. The Al Hajar Mountains and valleys of Musandam are dramatic reminders of this: Oman is fairly quiescent tectonically but the Musandan experiences occasional tremors as the Arabian Plate collides with the Eurasian Plate (I remember coming back from holiday & finding bathroom tiles all over the floor from one of these tremors).

During the Cretaceous Period Oman was located adjacent to a subduction zone and a portion of the upper mantle along with overlying seafloor volcanic rocks were thrust over the continental crust. This obducted sequence of ultramafic to mafic rocks is the Semail Ophiolite complex. The ophiolite is locally rich in copper and chromite ore.

The interior plains of Oman are of young sedimentary rocks, wadi gravels, dune sands and salt flats. Beneath them is a several kilometre thick stack of older sedimentary rocks that host the country’s hydrocarbon resources.

Links for most of this come from – Encyclopædia Britannica & Wikipedia.

 

Erosion.

ErosionRillenkarren – Erosion of rock during Oman’s wetter phase.

The technical description from my geology book says:

Rillenkarren.- Are forms of dissolution on the surface of the rocks that consist of small channels separated by sharp crests configuring a network of tight more or less parallel gullies next to each other. Its Genesis is linked to the dissolution of the rock by the sheet of water that forms on it as a local run-off.