Jabal Madmar

September 2005 (English only)

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Compiled following the GSO excursion on 29-30 September

How to get there: See maps above. Follow the highway to Nizwa and turn left (south) to Salalah. Some 68 km from the Highway fly-over, opposite a small mosque, take the gravel track to the left (22 39' 16.4" N // 57 33' 12.3" E). There are some signs that this area can be used as a shooting range. Turn south again at the next big junction (Jabal Madmar is now right in front) @ 22 39' 55.2" N // 57 34' 36.6" E. You will now pass the Jabal at the left side and that's where the access road starts at 22 26' 53.5" N // 57 39' 23.7" E (marked junction2madmar). Take care, the access road has some large and deep erosional gullies. When you see the tower you are at the end. Walk around and you may find the abanded Jabal Madmar borehole in a piece of concrete.

Many of us have seen these whalebacks driving south to Salalah with Adam as the last outpost of civilisation, more like the last sentries of the Mountains before the vast flatness of the interior gravel desert of Oman. They are true anticlines, arranged in a wide arch, the kind of things that geologist like to poke holes in as Thesinger already observed in the late 50’s while traveling on camel through Oman.

Jabal Madmar, dominating the horizon just east of Adam, has one of these holes, well Madmar-1, drilled by PDO in 1989. It found a bit of gas in difficult reservoir and that left the rest of the anticlines essentially untouched by an industry that was focused mainly on oil. They have great value as analogs for the deeper buried carbonate oil fields like Fahud and Natih. The outcrops are near 100%, revealing not only the rocks (carbonates of the Natih Formation), but also their systematic fractures and faults.

On the northern flank of Jebel Madmar several wadis cut deeply into the Natih Fm and allow detailed examination of the fracture distribution in various carbonate lithologies.

Jabal Madmar provides a complete section though the older Natih depositional cycles. A bit of walking and you can sniff  the Natih E source rocks. With a pair of good eyes or helped by binoculars, the larger scale rock successions and geometries reveal that the: platform carbonates are certainly not layer-cake.

Jabal Madmar is an elongate dome with long axis oriented WSW – ENE. Folding occurred probably during the Tertiary, late Eocene to Miocene, coinciding with the main compressional phase of the Zagros event farther to the North and may be related to the formation of Jebel Akhdar (Hanna, 1996). The line of hills (including Jebels Salakh, Qusaybah and Nihada to the West of Jebel Madmar formed above a deep detachment (e.g. 5 to 8 km below surface) possibly utilising the Ara Salt (late Pre-Cambrian to Cambrian) as an “easy-slip” horizon. Jebel Salakh forms a box fold with a steep southern limb. Thrusts are known from both North and South flanks on these folds.

Jebel Madmar is asymmetric in cross-section, the northern limb dipping some 30, the southern limb overturned in places

Jabal Madmar, panoramic view from the north. Notice the plunging axis to both the east (left) and the west (right).

Interpretation Madmar cross section

The access road to the drill site of Madmar-1 is easily accessible and the view on top is great. If you want to appreciate the size of one of these anticlines there is nothing better but to stand on top and see the rocks dipping to all sides.
View to the southwest from the crest of the anticline

<- Abandoned Jabal Madmar-1well


Watch tower at the end of the road, near the drill site of Jabal Madmar-1


FIELD GUIDE TO JEBEL SHAMS & JEBEL MADMAR AREAS AAPG FIELD EXCURSION FAULTS AND FRACTURES IN CARBONATES  1st – 3rd November 2002 Field guide prepared by Jack Filbrandt, Henk Droste, Salim al Mahruqi PDO, Samir Hanna SQU, Pascal Richard SEPTAR


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@ J. Schreurs November 2005