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Oman’s Awesome Geologic Beauties Exposed

by | May 16, 2024 | Oman | 0 comments

“To become more aware of landscapes is, in a sense, to share in the physical existence of the planet itself.”

Author unknown

Oman‘s awesome geology reads like an open book since there is little vegetation covering the mountains, so the rocks are fully exposed for study and enjoyment. As a geologist, I’m interested in every cool outcrop but it can overwhelm the lay person with talk of millions & billions of years plus complex movement of the earth’s tectonic plates.  Thus, I’ve tried to simplify the complex geologic history of Oman and focus on places that we visited over three weeks to give a sense of the dramatic scenery and fascinating story the rocks tell. There is so much more to the story, but for now, take a deep breath and absorb what you will.

Oman. Tectonics
Crisp view from road up to Balcony Hike showing a thrust fault in the upper right. I don’t know the name or age of these particular formations but sometimes it’s good enough to just enjoy the enormity and beauty of the mountains in all their glory.

A question to start our geologic journey – How does the geology of Oman affect the people?  Thinking about a question like that is one way to observe and enjoy the rocks and landscape of any country that you’re traveling through, so here we go.

Oman, located on the eastern margin of the Arabian plate, is adjacent to long-active plate boundaries in the Indian Ocean and the Gulf of Oman, so there’s been a lot of geologic action over a vast amount of time. 

Tectonic map of Oman and Arabian Plate and Iran.
Tectonic map of Oman & Samail Ophiolite. Also shows the thrust faults across from Oman in Iran to form the Zagros Mts., and to the west, the Red Sea rift zone splits Africa from the Arabian Plate.
From: Field Guide to the Geology of Northeastern Oman. Hoffman, G., et al. 2016

One result of that tectonic action over time is the uplift of the striking Al Hajar mountain range in the northeast of Oman, with the tallest peak of Jebel Shams at 9,000 ft. high. We circumnavigated the Al Hajar mountains beginning in the coastal capital, Muscat, then along the southern and northern flank of the mountains, shown on the map above in yellow for Samail Ophiolite.   

Famous Samail Ophiolite

Within 20 hours of landing in Muscat, we hiked a famous Samail ophiolite trail with a wonderful young Omani geologist, Anas.  This ophiolite sequence is a several kilometer thick slice of the upper mantle and oceanic crust from an ancient spreading zone, which was slowly thrust up and over the landmass of Oman from around 90 to 70 million years ago (Cretaceous).  It is the best and largest exposed ophiolite in the world, extending over 500 km! 

Samail Ophiolote. Oman. Muscat. Mutrah. Riham Trail
Hiking up the Riyam Ophiolite trail with old Muttrah below and the characteristic dark, ragged ophiolite hills surrounding the city.

Geologists from around the world visit Oman to study the ophiolite, as it offers an extensive glimpse into the rocks & minerals formed deep in the earth’s oceanic crust and upper mantle, formations that are rarely seen on the earth’s surface.  Thrusting of oceanic crust & mantle rocks on top of a continental mass is extremely uncommon as these dense formations are usually subducted, or thrust under the lighter continental crust.

Samail ophiolite.  Oman. Muscat. Dunite. Harzburgite
John & Anas, with ophiolite from the upper mantel composed of Dunite (light layers) & Harzburgite layers (dark layers). Chromite, copper and gold are found in these formations.

The sequence of ocean crust includes magnesium & iron rich gabbros, and a variety of volcanic rocks like sheeted dikes and pillow lavas, which erupted onto the ocean floor.  The upper mantle rocks, called dunite and harzburgite, are rich in minerals that form under great pressure and temperatures.  Historically important mineral deposits within the ophiolite include copper, chromite, platinum, nickel & gold.

Sharing our geologic view of the world on the trail.

The ancient name for Oman was Magan, which means copper.  Valuable copper deposits, critical for the development of the Bronze Age, were mined from the ophiolite five thousand years ago, catapulting Oman into the maritime trade network with Mesopotamia, India, Central Asia, and the east coast of Africa. The famous Sinbad the Sailor is thought to have been from the port town of Sohar as Omanis were long known for their navigational skills.

We were thrilled to get a personal tour of the ophiolite with Anas.  We climbed the trail up to where we could see the dark, red black ophiolite hills jut out into the sea where they divide and isolate different areas of greater Muscat, like old Muttrah where we stayed.  Each area has good bays and harbors, some with coral reefs that we explored.  In the evening, the rugged silhouettes of the ophiolite hills create a dramatic skyline in contrast to the white buildings of the city.

Samail Ophiolite. Muscat. Mutrah. Oman. Tectonics
Dark low ragged hills of the Samail Ophiolite envelop old Muttrah harbor along the coast.

Hawasina Sediments on top of the Ophiolite

The Hawasina formation is composed of shallow to deep ocean sedimentary deposits that were deposited on top of the ocean crust from the late Permian to late Cretaceous time.  Hawasina sediments were thrust up onto the Arabian continent concurrently with the ophiolite, then folded underneath the ophiolite.

Neothetys Ocean, Oman geology, Samail Ophiolite
Reconstruction of what the seafloor looked like back in the Cretaceous Era. The blue seafloor is the Hawasina Basin with its sedimentary deposits. The Samail Ophiolite is a slice of the brown mantle and green oceanic crust at the mid ocean ridge. Both were thrust up and over the Oman continental crust.
(From Field Guide to the Geology of Northeastern Oman)

Hawasina sediments now form low hills of thinly layered multi-colored chert (quartz) beds tilted, folded and faulted into striking shapes and angles, beautifully exposed in road cuts and low hills.

“Mother of all outcrops” – folded radiolarian chert beds of the Hawasina Formation. (Photo from Field Guide to Geology of NE Oman.)

Hawasina Formation. Oman. Tectonics
Near vertical multi-colored layers of the Hawasina Formation.
Hawasina Formation, Oman, near vertical tilting.
Tilted and faulted Hawasina Formation outcrop.

Eocene Limestone of Wadi Shab and Tiwi

Younger than the ophiolite, and south of Muscat along the Omani coast, near shore ocean deposits of the Eocene Seeb limestone are exposed. We visited two gorgeous wadis, Wadi Shab & Tiwi, that cut through yellow-brown Seeb limestone cliffs that were deposited in shallow, warm ocean waters between 55 to 34 million years ago. The sea was rich in marine life and one can find fossils of coral, clams and sea slugs in the layers.  The sea floor sediments were eventually uplifted high above current sea level and now form towering walls that enclose the two wadis.  Both wadis provide precious year-round water sources that make their way down to the sea. 

Towering Seeb formation limestone walls of Eocene age in Wadi Tiwi. A splendid place to car camp! We were told you can camp anywhere and no one will both you.
Eocene Seeb Limestone walls of Wadi Shab, the more narrow canyon.
Eocene Seeb Limestone with highly weathered gray and brown Ophiolite below at wadi level in Wadi Tiwi.

Al Hajar Mountains and the Balcony Trail

Oman is blessed with the Al Hajar mountain range which provides the people with life-giving waters and food that supports their culture and economy.  The high mountains act as a rain magnet and flowing water erodes deep wadis or gorges, some with year-round water.  Numerous springs emanating from limestone walls provide precious waters that feed lush gardens and abundant oases throughout northern Oman.  I was struck by how many oases we drove by, some huge, many small, some in wadis & mountains, others in the plains a distance from the mountains that are watered by ancient falaj or canal systems that feed date palms, bananas and mangoes.  Our host in Misfah had over 35 species of date palms in his small mountain farm.  

Misfah.  Oman.  falaj.  Oasis

Spring fed Falaj in foreground waters 35 species of date palms and other crops in this well tended mountain valley farm.

Ahmet in his Misfah garden with date palms in valley below. Note titled limestones off the south flanks of the folded Al Hajar mountains.

Misfah oasis date palms Oman

The Al Hajar Mountain range is folded into a broad tent-shaped fold, and the highest peak, Jebel Shams is over 9,000 ft.  On both flanks of the mountain are exposed tilted, shallow to deep oceanic limestone layers that are Triassic to Cretaceous in age (older than the ophiolite). The Ophiolite was thrust on top of the limestone but it eroded off the top and flanks of Al Hajar mountains over time, thus exposing the limestone and older rocks below.  See photo below to view this “Window” into the layers of the mountain due to erosion over vast amounts of time.

Geologic Cross section through Al Hajar Mountains, Oman, Jebel Akdar Peak
Cross section of Al Hajar Mountains. Note green Samail Ophiolite on right side and small green area on left side. The mountain is folded into the Jebe Akhdar Anticline, then the top and sides were eroded so the older rocks below are exposed in the crest of the mountains, presenting a “window” into the layers below. (From: Field Guide to the Geology of Northeastern Oman, G. Hoffman, et. al.)

One favorite day during our stay in the small village of Misfah on the flank of the Al Hajar mountains was hiking the Balcony Trail, which contours above the Grand Canyon of Oman. The wadi deep below this trail cuts a narrow gorge with cliffs higher than 3000 ft in some places. The gorge cuts through the entire Jurassic – Cretaceaous limestone sequence and creates a dramatic scene reminiscent of the American Southwest.  An old abandoned village lay in the wadi far below and at the end of the Balcony trail, a small group of old, abandoned stone houses, built under large alcoves cut back into the cliff walls, are remnants from peoples who survived with their goat herds and terraced gardens fed by a spring. 

Egyptian vulture Oman Balcony trail
Egyptian Vulture enjoying the thermals over Grand Canyon of Oman
An Omani and his canyon
An Omani and his canyon. Balcony trail contours at left.

Jebel Misht and Beehive Tombs

As we approached the early Bronze Age Beehive Tombs of Al Ayn in eastern Oman, the stunning Jebel Misht, one of Oman’s “exotic” coral reef, island limestone formations, rose in the distance.  This towering hunk of rock looms over thinly bedded, folded Hawasina sediments.  Twenty one Beehive tombs were built from easily cleaved, thin Hawasina rock layers.  These tombs are some of the best preserved early Bronze Age sites in Oman and reflect the wealth of the area at the center of copper mining, thus the ancient name of Magan ( 3rd millennium BC).

Jebel Misht, a massive “ limestone exotic” and it was an island before smashing into the continent
Jebel Misht, a massive “ limestone exotic”. It was an island before smashing into the continent along with the ophiolite sequence.
Looking west from Balcony Hike road.
Bee hive tombs. Twenty one Bee Hive tombs perched on low hill with Jebel Misht
Twenty one Bee Hive tombs perched on low hill with Jebel Misht looming in background.
John claimed his tomb.
John claimed his tomb.
 Hawasina formation used to build the Bee Hive tombs.
Hawasina formation makes easy to break blocks used to build the Bee Hive tombs.
Jebel Misht in Oman

The almost vertical rock face of Jebel Misht is about 3300 ft high and the name in Arabic translates to “Comb Mountain” due to its clearly visible serrated top. We were mesmerized by this outcrop, and I constantly stopped the car for another amazing shot as we drove a pleasant meandering and deserted two-lane road after leaving the tombs. 

Towering Jebel Misht with lower Hawasina sediments hills and lush oasis.
Side view of Jebel Misht.  Can see the serrated crest like a cockscomb.
Side view of Jebel Misht. Can see the serrated crest like a cockscomb.

Last day on the Road

On our last day driving, we passed through more rugged, low, dark hills of the Samail ophiolite at the base of the northern side of the Al Hajar mountains and then took a short detour up the wide, deep Wadi Khurus.  This impressive wadi cuts through massive tilted limestone of the Al Hajar mountains and the views were stunning. 

A hodgepodge of ophiolite and I don’t know what the lighter formation is at the top, while cruising down the road.
The depth and breadth of Wadi Khorus on north flank of Al Hajar mountains
The depth and breadth of Wadi Khorus on north flank of Al Hajar mountains.
Titled limestone layers of Wadi Khorus
Titled limestone layers of Wadi Khorus on left of road.
Notice how wide the wadi is in the canyon
Notice how wide the wadi is in the canyon, then it widens even more as it exits the canyon walls.
Beautiful new mosque up Wadi Khorus
Beautiful new mosque up Wadi Khorus serves the towns built on the sides of the wadi.

With this exploration of Wadi Khurus, we both felt satiated with our first geologic and cultural tour of northern Oman and headed towards Muscat for the end of our journey and return home. Three weeks is a short time but we got an initial feel for the geologic story of this new country, and it was fun to take it all in as we explored the countryside, graciously aided by the geologic field guide given to me by Anas, a perfect gift.

Quite the change. We walked to this modern outdoor restaurant center for our last night in Oman and enjoyed a nice meal outside and good people watching.

That’s all for now, see you on down the road.

Sidenote – As we left Wadi Khurus gorge and crossed over the wadi onto the road to Muscat, we noted the size of the wadi as it spreads out into the more open valley, and that the water must roar from the gorge during heavy rains. In fact, just two weeks after we returned home, a huge storm dumped heavy rain on Oman, and the Wadi Khurus system raged and flooded, causing several deaths and much damage …. the power of water in the moment and then over time.

References – 

  • Field Guide to the Geology of Northeastern Oman, G. Hoffman, M. Meschede, A. Zacke, M. Al Kindi, Borntraeger Science Publishers, 2016.    Anas gifted me the book and it described the geology at specified notable geologic sites.
    •  I saw this book and other geology books for sale in a small shop next to Nizwa souk, along with bird, plant & history books. Should be able to find in Muscat.
  • Google Oman geology, Samail ophiolite for professional articles on the geology.  

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