Farming for fossils

Fossil sites are generally the result of happy coincidence. It may be that this is the result of natural processes, when the sea or a river has eroded into cliffs of fossil bearing rocks. It could also be the result of human activity, where a quarry opened up for commercial reasons also happens to contain fossil-rich layers. However, it is rare for a fossil site to be made specifically for access to the fossils; and, when this does happen, access is usually restricted. However, there are exceptions. One of these is in the great Moroccan phosphate fields.

Fig. 1. Meadows of spring flowers conceal the fossil-rich rock just below the surface.

Strip mining for mineral phosphates is massive business in Morocco, providing the raw material for a vast proportion of the world’s phosphate fertiliser. Near the town of Khouribga, vast spoil heaps extend across the horizon and give an indication of the scale of the rock extraction going on behind them. These phosphate-bearing rocks are famous for their fossil content, and the cream and tan fossils from them can be seen for sale the world over. Unfortunately, access to the mines is very difficult and so, most of the time, collectors will have to satisfy themselves with what they can buy from dealers. While, purchasing specimens allows access to some really impressive finds, inevitably the fossils are out of context so their age is uncertain, and small and otherwise ‘unsellable’ fossils cannot be obtained. As some layers of the phosphatic deposits have several hundred minute shark and ray teeth in each kilo of sediment, just having access to the larger fossils for sale in shops means that a vast proportion of the fossils are unavailable to the collector. It is also just not the same as finding things yourself, with the excitement of discovery this brings.

Fig. 2. Sieving for Paleocene sharks’ teeth and other fossils in one of the pits scattered over the hillside.

Collecting fossils from the working mines is pretty much impossible, but one site is now available where this is not the case. In a small farm near Khouribga, Samir toils the ground for two rather different crops. As autumn wears on, beautiful purple flowers force their way up though the hard earth, each opening to reveal three golden strands of saffron. But the ground here yields more than the king of spices. The gentle slope of the hill conceals the entire thickness of the phosphorites, which lie just below the surface. In the past, one horizon within this hillside was mined in a complex of underground shafts, nowadays only revealed by small and obscure entrance tunnels. With a vast amount of work, one of these mine tunnels has been cleared, and the rocks within carefully searched. The soft, sandy phosphorite contains plenty of fossils here, just as on the surface. Skeletons of crocodiles, snakes and sharks have all been revealed within the mine, and smaller vertebrate fossils are present in their thousands, if the sediment is passed through a sieve. While the mine is impressive, it is not the end of the story, as a series of small excavations have revealed rocks of Cretaceous, Palaeocene and Eocene age, all rich in small fossils. The rocks are pretty much all phosphorites, but vary a lot in detail. Some of the beds have a very hard calcite cement, other levels have little or no calcite, and many readily break down into a loose sand of phosphatic ooids, nodules and fish bone shards. These very soft rocks can easily pass through a set of sieves – the coarse mesh catches the large sharks’ teeth and the finer fractions contain a huge range of tiny teeth and bones. After a bit of treatment with dilute acid to get rid of calcite ‘clots’, a vast number of tiny and stunningly preserved fossils are revealed under the microscope. A couple of kilos of the sieved residue can contain up to 20 species of sharks, rays and fish. With careful collecting, a number of discrete faunas can be collected, with fossils coming from rocks spanning over 15myrs, but totalling less that 15m thick.

Fig. 3. Samir shows off an early Eocene crocodile skeleton underground in the old phosphate mine.

Of course, every good farm has a farm shop and fossils from here and elsewhere in the phosphorites are meticulously prepared for sale; and unlike almost anywhere else in Morocco, there are no fakes to be seen. Instead, an amazing array of fossils from small sharks’ teeth to whole crocodiles and giant mosasaur skulls can be seen. While the saffron crop is very seasonal, the hope is that people coming here for the fossils will provide both a diversification for the farm and provide a valuable resource for fossil collectors.

Fig. 4. Detail of a piece of Upper Cretaceous phosphate rock, containing sharks’ teeth and fish bones.

In all, this must be the most civilised fossil site I have ever visited, with lots of fossil-rich rocks within a couple of hundred metres of each other, wonderful company, and water and sieves ready to use. If you want to visit this site, you can contact Samir at dunesouss@libero.it or using Facebook at Fossil Mosasaurus.

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