The Fezouata Formation or Fezouata Shale is a geological formation in

Morocco Morocco (),, ) officially the Kingdom of Morocco, is the westernmost country in the Maghreb region of North Africa. It overlooks the Mediterranean Sea to the north and the Atlantic Ocean to the west, and has land borders with Algeria t ...

which dates to the

Early Ordovician The Ordovician ( ) is a geologic period and system, the second of six periods of the Paleozoic Era. The Ordovician spans 41.6 million years from the end of the Cambrian Period million years ago (Mya) to the start of the Silurian Period Mya. ...

.Fezouata Formation
at Fossilworks.orgFezouata Shale
at Fossilworks.orgLower Fezouata Formation
at Fossilworks.orgUpper Fezouata Formation
at Fossilworks.org It was deposited in a marine environment, and is known for its exceptionally preserved fossils, filling an important preservational window beyond the earlier and more common Cambrian Burgess shale-type deposits.

Biota

Over 1,500 non- mineralized specimens, representing 50 distinct taxa that have a composition similar to earlier Burgess Shale type biotas, have been recovered from the formations in addition to a less abundant shelly fauna. The make-up of the community varies significantly through the stratigraphic sequence, with both abundances and faunal composition changing as time progresses. Small (1–3 mm wide) burrows are present in the sediment, but major burrowing is absent; this may suggest a paucity of oxygen in the water or sediment. Particularly notable is the presence of

bryozoa Bryozoa (also known as the Polyzoa, Ectoprocta or commonly as moss animals) are a phylum of simple, aquatic invertebrate animals, nearly all living in sedentary colonies. Typically about long, they have a special feeding structure called a ...

and

graptolite Graptolites are a group of colonial animals, members of the subclass Graptolithina within the class Pterobranchia. These filter-feeding organisms are known chiefly from fossils found from the Middle Cambrian ( Miaolingian, Wuliuan) through t ...

s, forms that are absent in the Cambrian period. Diverse

echinoderm An echinoderm () is any member of the phylum Echinodermata (). The adults are recognisable by their (usually five-point) radial symmetry, and include starfish, brittle stars, sea urchins, sand dollars, and sea cucumbers, as well as the s ...

s indicate a normal range of salinity, and the overall shelly assemblage is not significantly different from the normal shelly fauna expected in open Ordovician waters. The non-mineralized cohort contains a range of forms familiar from the Burgess Shale:

Demosponges Demosponges (Demospongiae) are the most diverse class in the phylum Porifera. They include 76.2% of all species of sponges with nearly 8,800 species worldwide (World Porifera Database). They are sponges with a soft body that covers a hard, ...

, lobopods, barnacles, annelids, radiodonts (e.g. ''

Aegirocassis ''Aegirocassis'' is an extinct genus of radiodont arthropod belonging to the family Hurdiidae that lived 480 million years ago during the early Ordovician. It is known by a single species, ''Aegirocassis benmoulai''. Van Roy initiated scientifi ...

''), possible

halkieriid The halkieriids are a group of fossil organisms from the Lower to Middle Cambrian. Their eponymous genus is ''Halkieria'' , which has been found on almost every continent in Lower to Mid Cambrian deposits, forming a large component of the smal ...

marrellomorph Marrellomorpha are an extinct group of arthropods known from the Cambrian to the Early Devonian. They lacked mineralised hard parts, so are only known from areas of exceptional preservation, limiting their fossil distribution. The best known me ...

s, paleoscolecid worms, naraoiids, skaniids as well as the expected ''problematica''. Other Ordovician oddballs are also present, including

mitrate Mitrates are an extinct group of stem group echinoderms, which may be closely related to the hemichordates. Along with the cornuta, cornutes, they form one half of the Stylophora. Morphology The organisms were a few millimetres long. Like the e ...

s, machaeridians, cheloniellids and

xiphosura Xiphosura () is an order of arthropods related to arachnids. They are more commonly known as horseshoe crabs (a name applied more specifically to the only extant family, Limulidae). They first appeared in the Hirnantian ( Late Ordovician). Curr ...

ns in abundance.

Depositional setting

Middle Ordovician South Polar paleogeography - 460 Ma

The fossiliferous strata were deposited just above storm wave base (offshore to lower shoreface transition), at between water depth. Organisms were likely buried in situ. Because of its placement above storm wave base, storms would have mobilized sediment that could be quickly deposited, trapping animals and leading to their preservation. Consequently, the assemblage is dominated by benthic organisms.

Preservation

Fossils of the Fezouata Formation, which are usually squashed flat (although some do retain some degree of their original three-dimensionality) are often coated with a dusting of

pyrite The mineral pyrite (), or iron pyrite, also known as fool's gold, is an iron sulfide with the chemical formula Fe S2 (iron (II) disulfide). Pyrite is the most abundant sulfide mineral. Pyrite's metallic luster and pale brass-yellow hue giv ...

, and tin; this aspect of the fossil preservation is very similar to that at

Chengjiang Chengjiang (; earlier Tchinkiang) is a city located in Yuxi, Yunnan Province, China, just north of Fuxian Lake. Administrative divisions Chengjiang City has 2 subdistricts and 4 townships. ;2 subdistricts * Fenglu () * Longjie () ;4 towns C ...

. Non-mineralized appendages are often preserved. While the formation as a whole is over thick, only two intervals, and thick, provide exceptional preservation. Both of these intervals are located near the top of the lower formation, corresponding to the ''Araneograptus murrayi'' and ''Hunnegraptus copiosus''

zones respectively.

Location and stratigraphy

The fossils occur within an area of , in southeast Morocco's

Draa Valley :''Dra is also the abbreviation for the constellation Draco.'' The Draa ( ber, Asif en Dra, ⴰⵙⵉⴼ ⴻⵏ ⴷⵔⴰ, ary, واد درعة, wad dərʿa; also spelled Dra or Drâa, in older sources mostly Darha or Dara) is Morocco's longest ...

, north of Zagora. Stratigraphically productive layers are found through a -thick column of rock that spans the

Tremadocian The Tremadocian is the lowest stage of Ordovician. Together with the later Floian Stage it forms the Lower Ordovician Epoch. The Tremadocian lasted from to million years ago. The base of the Tremadocian is defined as the first appearance of the ...

and

Floian The Floian is the second stage of the Ordovician Period. It succeeds the Tremadocian with which it forms the Lower Ordovician epoch. It precedes the Dapingian Stage of the Middle Ordovician. The Floian extended from to million years ago. The ...

epochs. Two stratigraphic intervals of the formation are fossiliferous: the lower is Late Tremadocian and sits above the base of the formation; the upper, at , is mid-Floian in age.

History

The Lagerstätten were first identified in the late 1990s when a local fossil collector, Ben Moula, showed some of the finds to a PhD student who was then working in the area.

IUGS geological heritage site

In respect of the 'exceptional fossil preservation bridging the Cambrian Explosion and the Great Ordovician Biodiversification', the International Union of Geological Sciences (IUGS) included the 'Ordovician Fezouata Shale Fossil Site at Jbeltizagzaouine' in its assemblage of 100 'geological heritage sites' around the world in a listing published in October 2022. The organisation defines an IUGS Geological Heritage Site as 'a key place with geological elements and/or processes of international scientific relevance, used as a reference, and/or with a substantial contribution to the development of geological sciences through history.'

Paleobiota

After and subsequent literature:

Arthropods

Echinoderms

Molluscs

Conodonts

Other animals

References

{{Burgess Shale type preservation Geologic formations of Morocco Ordovician System of Africa Lower Ordovician Series Tremadocian Floian Shale formations Paleontology in Morocco First 100 IUGS Geological Heritage Sites