Fezouata Formation
The Upper and Lower Fezouata formations of Morocco are Burgess Shale type deposits dating to the Lower Ordovician.[1] In the fossilized fauna were numerous organisms previously thought to have died out after the mid-Cambrian.[2] The discovery proves conclusively that the Burgess Shale biota did not go extinct in the Cambrian.
Biota
Over 1500 non-mineralized Burgess Shale types, representing 50 taxa, have been recovered from the formations. There are also a less abundant shelly fauna.[1] The make-up of the community varies significantly through the stratigraphic sequence, with both abundances and faunal composition changing as time progresses.[1] 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.[1]
Particularly notable is the presence of bryozoa and graptolites,[1] forms that are absent in the Cambrian period. Various 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.[1]
The non-mineralized (soft-bodied) fossils contains a range of forms familiar from the Burgess Shale. Other Ordovician oddballs are also present, including cheloniellids and horseshoe crabs in abundance.[1][3]
Geology
Depositional setting
The fossiliferous strata were deposited in quiet, deep waters, below the influence of wave action in all but the fiercest of storms. Such storms, or similar high-energy events, would have mobilized sediment that could be quickly deposited, trapping animals and leading to their preservation.[1] Consequently, the assemblage is dominated by benthic organisms.[1]
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, and tin; this aspect of the fossil preservation is very similar to that at Chengjiang.[1] Non-mineralized appendages are often preserved.[1]
Location
The fossils a span an area of 500 km2, in southeast Morocco's Draa Valley, north of Zagora. Fossils are found are found through a 1.1 km-thick column of rock that spans the two lowest epochs of the Ordovician.[1]
History
The lagerstätten were first identified in the late 1990s[4] when a local fossil collector, Ben Moula, showed some of the finds to a PhD student who was then working in the area.[5]
Fezouata Formation Media
- Middle Ordovician South Polar paleogeography - 460 Ma.png
South Polar paleogeography of the Middle Ordovician, 460 Ma
- 20191205 Aegirocassis benmoulai Aegirocassis benmoulae.png
Reconstruction of Aegirocassis benmoulai (Aegirocassis benmoulae in original description), an ordovician hurdiid/peytoiid radiodont (stem-
- Pseudoangustidontus.jpg
Reconstruction of Pseudoangustidontus duplospineus gen. et sp. nov.
- Asaphellus stubbsi, Lower Ordovician, Fezouata Formation, Morocco - Houston Museum of Natural Science - DSC01496.JPG
Exhibit in the Houston Museum of Natural Science, Houston, Texas, USA. Photography was permitted in the museum without restriction.
Fossil of trilobite Basilicus (Asaphidae). Took the picture at Teylers Museum, Haarlem
Colpocoryphe grandis fossil, in a practical laboratory of the Faculty of Sciences of the University of A Coruña.
Exhibit in the National Museum of Nature and Science, Tokyo, Japan. Photography was permitted in the museum without restriction.
- USNM PAL 536866 Eoharpes sp.jpg
Catalog number USNM PAL 536866, an Eoharpes sp. trilobite specimen from the Paleobiology collections at the Smithsonian Institution National Museum of Natural History in Washington, D.C. The specimen dates to the Ordovician and was collected in Morocco.
- Geragnostus mediterraneus CRF.jpg
A Geragnostus mediterraneus trilobite, Order Agnostida, Family Metagnostidae, 6mm measured along the axis, collected at the St.Chinian Formation, France, from the Middle Ordovician
References
- ↑ 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 1.11 Van Roy P. et al. 2010. Ordovician faunas of Burgess Shale type. Nature 465: 215–218. [1]
- ↑ (BBC News) Victoria Gill, "Fossil find resolves ancient extinction mystery": accessed 13 May 2010
- ↑ Cheloniellids are an extinct group of arthropods.
- ↑ Van Roy, P (2008). "Exceptionally preserved faunas from the Lower Ordovician of the Anti-Atlas, Morocco" in First international Conference and Exhibition, Marrakech, Morocco. .
- ↑ Jones, Nicola 2010. Weird wonders lived past the Cambrian. Nature News 465 [2]