Morocco: The Trilobite’s Sahara Kingdom
In November 2021, we returned to Morocco for the sixth running of our ‘Trilobite’s Sahara Kingdom’ tour.
Day one – Arrival
The tour officially started today as we welcomed a small group of guests from the UK and the USA. Despite the shifting sands of travel restrictions and testing requirements, all participants successfully negotiated the tests and made their way to the traditional riad close to the Medina of Marrakech where we spent our first night.
Day two – Marrakech to Ouarzazate
Today was the first full touring day and we travelled over the High Atlas Mountains from Marrakech to Ouarzazate. We started off with a visit to the Sidi Rahhal agate & geoid quarry. Here we saw flood basalts from the so-called CAMP event, the initial rifting of the North Atlantic which led to a mass extinction at the end of the Triassic. The agates have formed by water precipitating SiO2 in vesicles (holes) left by gases that were in the magma. Agate is a cryptocrystalline form of silica which is mostly chalcedony. At our quarry, the larger vesicles also had pure quartz crystals on top of the agate with a void in the centre forming a geode. We then moved on to the Tiz n’Tichka strike slip fault which is exposed in a recent road cut, near the Col du Tichka – you can see James pointing to this in the photos below. Here red terrestrial Triassic sediments are seen adjacent to marine Cambrian sediments. The fault is one of the High Atlas Mountains main faults.
In the afternoon, having crossed the summit of the pass over the Atlas, we visited the Telouet salt mine on the old Marrakech-Ouarzazate-Timbuktu road. In its heyday (in the 11th century) the salt mined here was worth more than its weight in gold! The salt also occurs due to the rifting of the North Atlantic in the Triassic which flooded and dried out several times before the ocean finally opened. The mine also lies very close to the Triassic/ Jurassic boundary and has the same Triassic lavas in its vicinity as the Sidi Rahhal quarry. The last photo (below) shows a boulder of Jurassic limestone containing brachiopod fossils.
The Atlas Mountains are still not yet fully understood. As compression has occurred due to the collision of Africa with Europe, pre-existing extensional faults (which formed with the creation of the Atlantic) have reactivated as strike-slip and thrust faults and a transpressional regime. However, the amount of uplift is much greater than expected – perhaps there is also an unknown magma source beneath?
We then drove on through Cretaceous paleogene and Precambrian rocks before reaching Ouarzazate, our stop for the night.
Day three – Fezouata Shale Lagerstätte
Today we crossed the Anti-Atlas Mountains to reach Zagora. The real highlight of the day was to visit the Ben Moula diggings in the Fezouata Lagerstätte. The Lagerstätte is Lower Ordovician in age and features soft bodied preservation and some of the same fauna (such as Anomalocaridids and marrellomorphs) that is found in the Cambrian Burgess Shale of Canada. One of the photos below, for example, is the nose of the planktonic anomalocarid Aegirocassis benmoulai. The Lagerstätte was discovered by Mohamed Oussaid Ben Moula (known as Ben Said) during the winter of 1999-2000, and featured on the front cover of Nature in 2010. We were lucky enough to meet and talk with Ben Said’s son, Hassan.
Earlier in the day we had visited an Ediacaran aged (570ma) site with stromatolites, lava flows, tuff and ripples. The stromatolites grew around the shore of ponds in a volcanically active area. We saw distinctive ripples in a tuff layer (volcanic ash); this tuff layer buried older stromatolites, the pond water formed the ripples, and then later stromatolites formed above the tuff layer. The stromatolites form an amazing landscape and this surface has perhaps remained unaltered for the last 570 million years! This was followed by a multicoloured road cutting through Cambrian aged sediments. Additionally we visited a Lower Ordovician site called Ouled Slimane where giant trilobites have been found, shown in the photos below. This is the discovery site of the giant Dikelokephalinid trilobites and we saw the diggings where fossil miners had extracted specimens; we examined their discarded fragments.
Day four – Alnif: trilobite capital of the world
Today we travelled from Zagora to Alnif; the latter is nicknamed ‘the trilobite capital of the world’. A highlight of the day was a visit to Ben Moula’s gallery/shop. Here we were able to see many beautiful fossils from the Fezouata Lagerstätte (we visited the Lower Ordovician diggings yesterday). The photos below include an unknown organism that has been sold to Harvard University, an unknown species of anomalocarid which contains a trilobite (Tremaglaspis sp.), in its stomach (this can be seen in the loose piece in the centre of the photograph), a fossil sponge, and four large Asaphid trilobites from the Ouled Slimane site that we visited the previous day. Earlier in the day we also visited a Silurian site called Seredrar, here a mass death assemblage of Orthoceras is quarried to make table tops and other furniture. Additionally we visited Jebel Tiskouine, where it is estimated over 15 million ‘mud-bug’ (Copocoryphe & Flexicalymene) trilobites have been mined from the Upper Ordovician Ktaoua Formation in the last 30 years. Finally we visited a Cambrian site where Cambropallas trilobites are extracted (shown in the photos below), before heading to Alnif to spend the night.
Day five – Devonian fossils
Today was the first of two days looking at the Devonian rocks in the Maider Basin – a paradise for trilobites! Our first stop of the day, after leaving our hotel in Alnif, was to visit Brahim’s fossil shop (pictured). After this, we moved on to the north side of Jbel Issoumour near Bou Dib. The rock age here is late Emsian – early Eifelian. Here we saw a trilobite horizon that had been mined for several kilometres. The horizon is called the Psychopyge horizon after the spectacular Pysychopyge elegans trilobite that is found in it; many other trilobite species are found in the horizon too. Underneath this hard limestone layer are many loose fossils that are eroded out of softer marls. Fossils we were able to examine included orthocones, trilobites, blastoids, bivalves, ammonoids and algae. Once we had spent some time looking at these fossils, we then journeyed to another Emsian site where the whole desert floor was made up of fossils and loose pieces of rock. Here we were able to see brachiopods, coral, crinoids, clams, sponges and goniatites. We stopped in the village of Fezzou for tea, where the local café owner showed us several goniatites (pictured).
We then visited a Pragian site called Atchana, where trilobites are mined from two trenches. These diggings yield the incredibly spinous Dicranurus monstrosus and other famous trilobites such as Scutellum, Cheirurus and Paralejurus. All of these trilobites are encased in a hard limestone and need many hours of preparation to reveal them. We then had a thrilling off-road drive across a smooth former lake bed to reach a remote desert oasis called Mherch where we spent the night at the Auberge Oasis Mherch (pictured).
Day six – Devonian mud mounds
Our first stop of the day was either a hydrothermal mud mound or a bioherm, named Guelb el Mherch, which grew in the Givetian epoch of the Devonian and stands 45m tall. It is made of limestone lined with a crystalline calcite and was formed by biota living around a seep of hot fluids. This means the existing desert surface is the paleo-seafloor of that time. Crinoids and corals are very abundant here and remains of placoderm fish have also been found. Our second stop was a much larger mud mound called Mrakib. At its base is the Drotops megalomanicus trilobite horizon; this is the largest phacopid trilobite. In the diggings were some remains of these trilobites and on the desert floor there were abundant brachiopods and corals. We then moved to a desert area near Jbel El Krabis, where we were able to see several different species of goniatites and bivalves. At lunchtime we stopped in a hamlet and had lunch with Youssef’s cousin, who is a trilobite preparator, and his family. We were able to watch his work and see some of the beautiful specimens he has prepared. Our next stop was the Gara Medouar erosional crater near Rissani. As well as being of geological and historical interest, the crater has featured in the films The Mummy and the Bond film, Spectre! We then moved on to Jbel Amelane where outcrops of ‘Erfoud Stone’ could be seen. This ornate limestone contains both orthoceras and the large ammonoid Gonioclymenia. This stone is used to make decorative table tops and basins in hotels. The outcrop has largely been mined away elsewhere. Before leaving the site, we were also able to get a distant view of the Eifelian-Givetian global stratotype GSSP (golden spike) (final photo below); this site is the internationally agreed reference site for the Givetian boundary, having originally been recognised in Belgium, prior to being moved here.
We then arrived in Merzouga, in the Erg Chebbi sand dunes, our base for the next three days.
Day seven – Dinosaurs and minerals
Today we were in the Merzouga area of Morocco, at the edge of the Sahara Desert. We started the day with a stop at the Erg Chebbi dunes where we were examined not only the dunes, but also fugerite, which is formed when lighting strikes the sand and fuses it into glassy tubes. We then went to the Kem Kem diggings where over 80 different Cretaceous vertebrate taxa have been found. These include crocodiles, pterosaurs, scherorhynchid sharks, lung fish, bony fish, turtles, snakes, lizards and amphibians. Perhaps most famously of all though, these beds have revealed dinosaurs; the beds have a very high ratio of carnivorous to herbivorous dinosaurs. It is thought the shifting deltaic conditions were not good for the plants, and instead the food chain was based on the aquatic creatures. Predatory dinosaurs found in the Kem Kem include Carcharodontosaurus, Deltadromeous and, most famously, Spinosaurus. Spinosaurus teeth are abundant here. Fossil miners dig into treacherous tunnels to extract material. We were able to meet one of the miners and examine the specimens that he had found. We then moved on to the Filon 12 mineral mine. This mine started life as a haematite mine, and is now a mine solely for mineralogical specimens. Minerals found here include vanadinite, goethite and haematite. We were taken on an underground tour by local guide Moha @mohamezane
Next, we visited the Silurian (Pridoli) and we saw Scyphocrinites crinoids. These amazing crinoids were pelagic and floated under a bladder or ‘lobolith’ (shown in the photos below). After this, we had further stops, firstly to see Orthoceras in a bed of earliest Devonian and secondly to see a Ludlow (mid-Silurian) bed with a mass assemblage of Orthoceras. This Orthoceras layer is quarried elsewhere to produce table tops and ornaments. All of these Orthoceras and crinoid beds were very close to each other, tilted in a syncline. One of the photos below shows two of our group standing on an outcrop of Silurian orthoceras limestone that has been cut by faulting.
Day eight – In and around Erfoud
Today was spent in the Erfoud area and our first stop of the day was Hamar Laghdad, also known as the Kes Kes; this name is derived from the name of the cooking pots which cous cous is cooked in, to which the site bears a resemblance. This is one of the best known Devonian sites in Morocco. There are 40 or more carbonate mounds in a 7km line which formed on a volcano as hydrothermal mud mounds. They have been exposed by erosion and are seen sitting on their paleosurface. Corals and trilobites used to be very abundant but have been heavily collected.
After the Kes Kes we visited Erfoud Quarry. The Devonian (Famennian) limestone here contains Orthoceras and the ammonoid Gonioclymenia, which is made into table tops, basins and ornaments in the Erfoud “Orthoceras factories”. The outcrop is now mostly destroyed with just blocks of stone remaining. We stopped for a picnic lunch at a late Devonian trilobite site; one of our group found a beautiful rolled phacops here. After this stop we visited a nearby Silurian (Pridoli) Scyphocrinites Limestone horizon. Here the crinoids are commercially mined in bellpits; these pits descend 11 metres straight down with earth steps cut into the shaft walls. Adjacent to the crinoid bed we saw a Silurian (Ludlow) mined bed of Orthoceras which is also turned into ornaments in the Erfoud factories.
Finally we explored Erfoud city, where we visited an Orthoceras factory and saw how Orthoceras limestone is made into table tops and much more. We also saw magnificent crinoid and trilobite fossils. We then visited the Tahiri Museum. Here we saw some amazing Drotops trilobites that had been completely removed from their rock matrix (pictured below). After this, we returned to Merzouga for a third and final night, taking a sunset camel ride before dinner!
Days nine & ten – the road back to Marrakech
We spent the final two full days of the tour driving back from Merzouga to Marrakech. We stopped at the stunning Todra Gorge, where we saw impressive folding and faulting. This is caused by the collision of Africa and Europe thrusting Jurassic sediments over Eocene and Cretaceous sediments. This thrust fault forms a sudden increase in relief and is the start of the High Atlas Mountains. The gorge follows a smaller fault which is at right angles to this large thrust fault. The over-thrusted Jurassic sediments are heavily folded and, in the gorge, their bedding planes are vertical. After the gorge we had lunch in a restaurant before proceeding on to Ouarzazate where we spent the night.
The next morning we visited the World Heritage Site of Ait Ben Haddou, an impressive kasbah built in the 11th century. It has featured in several movies, such as Gladiator, Jewel of the Nile, Lawerence of Arabia and Jesus of Nazareth. We then crossed over the High Atlas pausing to admire the views. We stopped at another restaurant for lunch, arriving back in Marrakech in the mid-afternoon.
Day eleven – departure
After a fabulous journey across some amazing terrain, seeing some truly wonderful palaeontological and geological sites, some of our group were able to add on a city tour with local guide, Mustafa. We all then went our separate ways and returned home.
Huge thanks are due to Youssef who, once again, provided excellent driving services and local guiding.