Los Rastros Formation
| Los Rastros Formation | |
|---|---|
| Stratigraphic range: Carnian | |
| Type | Geological formation |
| Unit of | Agua de la Peña Group |
| Underlies | Ischigualasto Formation |
| Overlies | Chañares Formation |
| Thickness | Up to 1,000 m (3,300 ft) |
| Lithology | |
| Primary | Claystone, sandstone |
| Other | Mudstone |
| Location | |
| Coordinates | 29°06′S 69°06′W / 29.1°S 69.1°W |
| Approximate paleocoordinates | 45°48′S 34°54′W / 45.8°S 34.9°W |
| Region | La Rioja Province San Juan Province |
| Country | Argentina |
| Extent | Ischigualasto-Villa Unión Basin |
  Los Rastros Formation (Argentina) | |
The Los Rastros Formation is a Ladinian to Carnian fossiliferous formation of the Agua de la Peña Group in the Ischigualasto-Villa Unión Basin in northwestern Argentina. Fossil theropod tracks,[1] as well as many insects, fossil fish of Myriolepis,[2] bivalves and crustaceans and flora have been reported from the formation.
Description
The formation overlies the Chañares Formation (and/or the Ischicuca Formation), and is overlain by the Ischigualasto Formation.[3] The formation belongs to the Agua de la Peña Group of the Ischigualasto-Villa Unión Basin, where it is exposed in the Ischigualasto Provincial Park, a World Heritage Site in Argentina.[4] The up to 1,000 metres (3,300 ft) thick formation of claystones, mudstones and sandstones was deposited in a deltaic to lacustrine environment during the first post-rift sequence in the basin.[3][5]
A CA-TIMS U-Pb zircon age of 234.47 ± 0.44 Ma from the lower Los Rastros Formation was published in 2020. The acquired age demonstrates that most of the overlying lacustrine strata within the basin were deposited during or after the Carnian Pluvial Event (CPE) that lasted from 237 to 227 Ma approximately.[6]
Fossil content
The following fossils among others have been recovered from the formation:[5]
- Fish
- Challaia elongata (Class Actinopterygii, Order Palaeonisciformes, Family Acrolepidae; formerly assigned to the genus Myriolepis) [7]
- Gualolepis carinaesquamosa (actinopterygian; possibly a member of the family Peipiaosteidae, making it a relative of sturgeons and paddlefish)[7]
- Rastrolepis latipinnata (actinopterygian) [7]
- Rastrolepis riojaensis (actinopterygian) [7]
- Insects
Blattoptera (cockroaches and their relatives)
- Argentinoblatta herbsti[8]
- Argentinoblattula revelata[9]
- Condorblatta lutzae[8]
- Hermosablatta crassatella
- Hermosablatta pectinata[10]
- Lariojablatta chanarensis[11]
- Mancusoblatta pulchella[12]
- Pulchellablatta nana[13]
- Samaroblatta corrientesina[13]
- Samaroblatta gualoensis[14]
- Triassoblatta argentina[11]
Coleoptera (beetles and their relatives)
Hemiptera (true bugs and their relatives)
Unknown
- Crustaceans
- Bivalves
- Flora
- Ichnofossils
See also
- List of dinosaur-bearing rock formations
- Chañares Formation
- Santa Maria Formation
- Omingonde Formation
References
- ^ Weishampel et al., 2004, pp. 517-607
- ^ a b c d e f g h i j Leonardi, 1994, p.20
- ^ a b Aceituno Cieri, 2015, p.60
- ^ Kent et al, 2014, p.7959
- ^ a b Los Chañares at Fossilworks.org
- ^ Mancuso et al., 2020
- ^ a b c d Lopez-Arbarello et al, 2006
- ^ a b Martins Neto et al., 2005, p.5
- ^ Martins Neto et al., 2005, p.16
- ^ Martins Neto et al., 2005, p.10
- ^ a b Martins Neto et al., 2005, p.12
- ^ Martins Neto et al., 2005, p.8
- ^ a b Martins Neto et al., 2005, p.14
- ^ Martins Neto et al., 2005, p.13
- ^ Leonardi, 1994, p.21
Bibliography
- Geologic formations of Argentina
- Triassic System of South America
- Triassic Argentina
- Carnian Stage
- Shale formations
- Sandstone formations
- Deltaic deposits
- Lacustrine deposits
- Ichnofossiliferous formations
- Ischigualasto-Villa Unión Basin
- Fossiliferous stratigraphic units of South America
- Paleontology in Argentina
- Geology of La Rioja Province, Argentina
- Geology of San Juan Province, Argentina