The Fezouata Formation or Fezouata Shale is a geological formation in Morocco which dates to the Early Ordovician . 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 . The fauna of this geological unit is often described as the Fezouata biota , and the particular strata within the formation which exhibit exceptional preservation are generally termed the Fezouata Lagerstätte .
20-401: 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. Major burrowing
40-463: A 1.1 kilometres (0.68 mi)-thick column of rock that spans the Tremadocian and Floian epochs. Two stratigraphic intervals of the formation are fossiliferous: the lower is Late Tremadocian and sits 260 to 330 metres (850 to 1,080 ft) above the base of the formation; the upper, at 570 to 620 metres (1,870 to 2,030 ft), is mid-Floian in age. The Lagerstätten were first identified in
60-409: A few centimeters long. The body of synziphosurine composed of a prosoma covered by a dome-like carapace (prosomal dorsal shield) and an opisthosoma with usually unfused 9-11 segments expressed by tergites . With the exception of Pseudoniscus and Pasternakevia , the last 3 opisthosomal segments precede the spine-like telson are specialized into a narrow postabdomen (pretelson), while
80-554: A higher proportion of brachiopod and trilobite fossils. Nevertheless, there are quite a few exceptions which contradict these broad rules. Many sites record diverse deep-water ecosystems protected from both storms and insufficient oxygen. Numerous species of echinoderms and other invertebrates coexist at these localities, even if one echinoderm species outnumbers other fossils at any given time. Large Rhopalocystis species, Macrocystella , Plasiacystis , and Balantiocystis are common components of these assemblages. Fezouata reconstructs
100-880: A range of forms familiar from the Burgess Shale: Demosponges , lobopods , barnacles , annelids , radiodonts (e.g. Aegirocassis ), possible halkieriids , marrellomorphs , paleoscolecid worms, nektaspids , skaniids as well as the expected problematica . Other Ordovician oddballs are also present, including mitrates , machaeridians , cheloniellids and xiphosurans in abundance. The fossiliferous strata were deposited just above storm wave base (offshore to lower shoreface transition), at between 50 and 150 metres (160 and 490 ft) 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,
120-597: A whole is over 1,000 metres (3,300 ft) thick, only two intervals, 25 metres (82 ft) and 15 metres (49 ft) 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 graptolite zones respectively. The fossils occur within an area of 500 square kilometres (190 sq mi), in southeast Morocco's Draa Valley , north of Zagora . Stratigraphically productive layers are found through
140-548: Is not present, but there are small (1-3 mm wide) burrows in the sediment, which may indicate that there is not enough oxygen in the water or sediment. Particularly notable is the presence of bryozoa and graptolites , forms that are absent in the Cambrian period. Diverse echinoderms 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
160-529: Is the deposition of economically important metals in the formation of ore bodies or " lodes " by various process. The first scientific studies of this process took place in the English county of Cornwall by J.W.Henwood FRS and later by R.W. Fox, FRS . The term can also refer to the process by which waterborne minerals, such as calcium carbonate ( calcite ), iron oxide ( hematite or limonite ) or silica ( quartz ), replace organic material within
180-673: The Fezouata Biota remain unnamed and undescribed. These include synziphosurines , xiphosurans (horseshoe crabs), eurypterids , chasmataspidids , phyllocarids , ostracods , a canadaspidid , a leanchoiliid , a cheloniellid ( Eoduslia ?), a possible retifaciid , and a lepadomorph barnacle . Many echinoderm species of the Fezouata Biota remain unnamed and undescribed. These include representatives of chauvelicystids , other cornutes , anomalacystitids , mitrocystitids , eocrinoids , rhenopyrgids , and somasteroids . Fezouata stylophoran fossils include soft tissue preserved among
200-469: The assemblage is dominated by benthic organisms. 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 , and tin; this aspect of the fossil preservation is very similar to that at Chengjiang . Non-mineralized appendages are often preserved. While the formation as
220-488: The body of an organism that has died and was buried by sediments. Mineralization may also refer to the product resulting from the process of mineralization. For example, mineralization (the process) may introduce metals (such as iron) into a rock. That rock may then be referred to as possessing iron mineralization. Synziphosurina Synziphosurina is a paraphyletic group of chelicerate arthropods previously thought to be basal horseshoe crabs ( Xiphosura ). It
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#1732772761989240-400: The entire the formation, small Rhopalocystis species dominate "meadow"-like ecosystems in shallow waters impacted by storms. In the youngest layers of the formations, diploporites usurp this niche. Conversely, stylophorans are opportunistic colonizers of deeper low-oxygen seabeds in some intervals of the Araneograptus murrayi zone. Echinoderms are uncommon at intermediate depths, which have
260-1055: The formation: a third species of Pseudoangustidontus , an aegirocassisine, and a sediment-sifting hurdiid. Baltograptus minutus zone? The largest trilobite individuals in the Fezouata Formation tend to inhabit deep oxygenated waters with minimal influence from storms or larger predators. ?Baltograptus jacksoni zone ?Cymatograptus protobalticus zone Upper Fezouata ?Cymatograptus protobalticus zone, ? Baltograptus jacksoni zone Upper Fezouata Upper Fezouata Baltograptus minutus zone Baltograptus minutus zone ?Cymatograptus protobalticus zone ?Cymatograptus protobalticus zone, ? Baltograptus jacksoni zone ?Baltograptus jacksoni zone ?Baltograptus jacksoni zone Rhabdinopora flabelliformis anglica zone Upper Fezouata Baltograptus minutus zone ?Cymatograptus protobalticus zone, ? Baltograptus jacksoni zone Baltograptus minutus zone ?Baltograptus jacksoni zone Upper Fezouata ?Cymatograptus protobalticus zone, ? Baltograptus jacksoni zone Many arthropods of
280-683: 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. 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
300-576: The region. This also provided more space for the establishment of a distinctive South Polar ecosystem dominated by eocrinoids, mitrates, solutans, and eventually diploporites. Hunnegraptus copiosus zone, ? Baltograptus jacksoni zone ? Baltograptus jacksoni zone ? Cymatograptus protobalticus zone, ? Baltograptus jacksoni zone ? Baltograptus jacksoni zone ? Baltograptus jacksoni zone ? Baltograptus jacksoni zone ? Baltograptus jacksoni zone ? Cymatograptus protobalticus zone Mineralization (geology) In geology , mineralization
320-688: The remaining wider segments referred to as preabdomen. A reduced anteriormost tergite (microtergite) originated from the first opisthosomal segment is observable at least in some genera. Most synziphosurines are possibly blind, with only a few species showing possible (e.g. Weinbergina opitzi ) or clear (e.g. Legrandella lombardii ) evidences of lateral compound eyes on their carapaces. Evidences of appendages are scarce, fragmentary known from Anderella parva , Camanchia grovensis and Venustulus waukeshaensis while exceptionally well-documented in Weinbergina opitzi . The prosoma possess
340-472: The skeletal elements, helping to unravel controversial details of their anatomy and ecology. Specific echinoderm species may form dense fossil beds in some layers of the formation, a phenomenon which is particularly common in the mid-late Tremadocian ( Araneograptus murrayi graptolite zone). Most echinoderm beds are dominated by only a few species, often representatives of stylophorans or the eocrinoid Rhopalocystis , with few other animal fossils. Through nearly
360-557: The uneven nature of the Cambrian-Ordovician transition of echinoderm faunas. Cosmopolitan Late Cambrian hallmarks (such as cornute stylophorans) maintain their abundance in oxygen-poor areas, while newer groups (crinoids, diploporites, asterozoans) make inroads into more oxygenated waters. The rarity of carbonate platforms and hard substrates in the Gondwanan area delayed the diversification of crinoids and edrioasteroids in
380-512: 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.' After and subsequent literature: Apart from the three named species of Fezouata radiodonts, three other unnamed species occur in
400-550: Was later identified as a grade composed of various basal euchelicerates, eventually excluded from the monophyletic Xiphosura sensu stricto and only regarded as horseshoe crabs under a broader sense ('Xiphosura' sensu lato ). Synziphosurines survived at least since early Ordovician to early Carboniferous in ages, with most species are known from the in-between Silurian strata. While Weinbergina and Willwerathia being exceptionally large, most synziphosurines are small arthropods with body length ranging only about
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