Santana Formation
| Santana Formation Stratigraphic range: Cenomanian | |
|---|---|
 Fossil of a locust from the Santana Formation | |
| Type | Geological formation |
| Unit of | Araripina Group |
| Overlies | Crato Formation |
| Location | |
| Country |
 Brazil |
The Santana Formation is a geologic Lagerstätte (undisturbed fossil accumulation) in northeastern Brazil's Araripe Basin where the states of Pernambuco, Piauí and Ceará come together. The geological formation, named after the village of Santana do Cariri, lies at the base of the Araripe Plateau. It was discovered by Johann Baptist von Spix in 1819. The strata were laid down during the early Cretaceous, specifically during the early Cenomanian, about 92 million years ago, in a shallow inland sea. At that time, the South Atlantic was opening up in a long narrow shallow sea.
The Santana Formation earns the designation of Lagerstätte due to an exceedingly well preserved and diverse fossil faunal assemblage. Some 25 species of fossil fishes are often found with stomach contents preserved, enabling paleontologists to study predator-prey relationships in this ecosystem. There are also fine examples of pterosaurs, reptiles and amphibians, invertebrates (particularly insects), and plants. Even dinosaurs are represented: a new maniraptor was described in 1996. The unusual taphonomy of the site resulted in limestone accretions that formed nodules around dead organisms, preserving even soft parts of their anatomy. In preservation, the nodules are etched away with acid, and the fossils often prepared by the transfer technique.[1]
Local mining activities for cement and construction damage the sites. Trade in illegally-collected fossils has sprung up in the last decade, driven by the remarkable state of preservation and beauty of these fossils and amounting to a considerable local industry. An urgent preservation program is being called for by paleontologists.
In addition, the weathering of Santana Formation rocks has contributed soil conditions unlike elsewhere in the region. The Araripe Manakin (Antilophia bokermanni) is a very rare bird that was discovered only in the late 20th century; it is not known from anywhere outside the characteristic forest that grows on the Chapada do Araripe soils formed ultimately from Santana Formation rocks.
Crato Member
The Crato Formation has often historically been considered the lowest member of the Santana Formation (or, alternatively, the Araripina Formation). The Crato Member is the product of a single phase, where complicated sequence of sediment strata reflect changeable conditions in the opening sea. The age of this strata has been controversial, though most workers have agreed that it lies on or near the Aptian-Albian boundary, about 112 million years ago.[2]
The extent of the Crato unit and its relationship to the Santana Formation had long been ill defined. It was not until a 2007 volume on the unit by Martill, Bechly and Loveridge that the Crato Formation was given a formal type locality, and was formally made a distinct formation separate from the Santana, which is about 10 Ma younger.[2]
Notable taxa
Dinosaurs
Indeterminate remains of non-avian theropods, avialans, ornithischians, and possibly oviraptorosaurs have been found in Estado do Ceara, Brazil.[3]
| Dinosaurs and Birds of the Santana Formation | ||||
|---|---|---|---|---|
| Genus | Species | Presence | Notes | Images |
|
Angaturama[3] |
A. limai[3] |
Geographically present in Estado do Ceara, Brazil.[3] |
Spinosauridae. "Rostral portion of [a] skull."[4] Junior synonym of Irritator challengeri. |
|
|
I. challengeri[3] |
Geographically present in Estado do Ceara, Brazil.[3] |
Spinosauridae. "Partial skull."[4] | ||
|
M. asymmetrica[3] |
Geographically present in Estado do Ceara, Brazil.[3] |
|||
|
S. placidus[3] |
Geographically present in Estado do Ceara, Brazil.[3] |
"Partial postcranium."[5] | ||
Pterosaurs
| Pterodactyls of the Santana Formation | ||||
|---|---|---|---|---|
| Genus | Species | Presence | Description | Images |
|
Araripedactylus dehmi |
| |||
|
Araripesaurus castilhoi |
||||
|
Barbosania gracilirostris |
||||
|
Cearadactylus atrox |
||||
|
"Pricesaurus megalodon" |
||||
|
Santanadactylus brasilensis |
||||
|
Tapejara wellnhoferi |
||||
|
Thalassodromeus sethi |
||||
|
Tropeognathus mesembrinus |
||||
|
Romualdo Member |
|||
Turtles
| Turtles of the Santana Formation | ||||
|---|---|---|---|---|
| Genus | Species | Presence | Description | Images |
|
| ||||
See also
- List of fossil sites (with link directory)
- List of dinosaur-bearing rock formations
References
- ↑ Maisey, J.G., Rutzky, I., Blum, S. & W. Elvers (1991): Laboratory Preparation Techniques. In Maisey, j:G. (ed): Santana Fossils: An Illustrated Atlas, Tfh Pubns Inc.ISBN 0866225498. pp 99–103.
- ↑ 2.0 2.1 Martill, D.M., Bechly, G. and Loveridge, R.F. (2007). The Crato fossil beds of Brazil: window into an ancient world. Cambridge University Press. ISBN 0-521-85867-4, ISBN 978-0-521-85867-0
- ↑ 3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 3.10 3.11 3.12 Weishampel, David B; et al. (2004). "Dinosaur distribution (Early Cretaceous, South America)." In: Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds.): The Dinosauria, 2nd, Berkeley: University of California Press. Pp. 563-570. ISBN 0-520-24209-2.
- ↑ 4.0 4.1 "Table 4.1," in Weishampel, et al. (2004). Page 73.
- ↑ "Table 5.1," in Weishampel, et al. (2004). Page 114.
- ↑ Ross A. Elgin and Eberhard Frey (2011) A new ornithocheirid, Barbosania gracilirostris gen. et sp. nov. (Pterosauria, Pterodactyloidea) from the Santana Formation (Cretaceous) of NE Brazil Swiss Journal of Palaeontology (advance online publication) doi:10.1007/s13358-011-0017-4
External links
- Santana Formation fossils
- geol/jgs/1996/00000153/00000001/15310005 "A new crested maniraptoran dinosaur from the Santana Formation"
- American Museum of Natural History: Brazilian fossil fishes
- Maria Somália Sales Viana and Virgínio Henrique Lopes Neumann, "The Crato Member of the Santana Formation, Ceará State"
Further reading
- David A. Grimaldi (ed.) 1990. Insects from the Santana Formation, Lower Cretaceous, of Brazil, Bulletin of the American Museum of Natural History no. 195
- John G. Maisey (ed.) 1991. Santana Fossils - An Illustrated Atlas (T.H.F. Publ.)
- David M. Martill, 1993. Fossils of the Santana and Crato Formations, Brazil (Field Guide to Fossils no. 5) (The Palaeontological Association) ISBN 0-901702-46-3
- David M. Martill, Günter Bechly and Robert F. Loverridge (eds) 2007. The Crato Fossil Beds of Brazil: Window into an Ancient World (Cambridge University Press) ISBN 978-0-521-85867-0