Ranquil Formation | |
---|---|
Stratigraphic range: Miocene– Pliocene | |
Type | Geological formation |
Underlies | Tubul Formation |
Overlies | Lebu Group |
Lithology | |
Primary | Conglomerate with clay and silt matrix, breccia, sandstone, siltstone, mudstone |
Other | Conglomerate with sand matrix |
Location | |
Coordinates | 37°36′S 73°42′W / 37.6°S 73.7°W |
Approximate paleocoordinates | 37°54′S 71°24′W / 37.9°S 71.4°W |
Region | Bío Bío Region |
Country | Chile |
Type section | |
Named for | Caleta Ranquil |
Named by | Juan Tavera |
Year defined | 1942 |
The Ranquil Formation ( Spanish: Formación Ranquil) is a Miocene and Pliocene sedimentary formation located in Arauco Province in south–central Chile, including outcrops in Mocha Island. The formation has its greatest thicknesses in the south-west, where its sediments were largely deposited in marine conditions. It overlies unconformably sedimentary formations of the Paleocene- Eocene Lebu Group. [1] The formation is part of the fill of Arauco Basin which is a sedimentary basin that extends south of Concepción. [2]
Macrofossils of the formation are similar to those of Navidad ( 34° S) and Lacui Formations ( 43° S), two nearby Miocene marine formations. [3]
The base of the Ranquil Formation is the so-called "main unconformity", which is thought to have been formed by erosion during a period of tectonic inversion. [4]
The formation was first defined in 1942 by Juan Tavera. [1]
The formation has been subdivided into five units, with the lowermost being made up of sandstone and shale, and the second lowest one being made up of a conglomerate. The middle unit is made up of mudrock and massive sandstone. At some places the middle unit is overlain by a unit made up of sandstone with thin layers of conglomerate and sandstone that has been bioturbated. The uppermost unit include a breccia and the so-called Huenteguapi sandstone. [2] The sediments of Huenteguapi sandstone evidences that a megatsunami struck the coast of south–central Chile in the Pliocene, [2] which has been linked to the hypothetical Eltanin impact.
The Ranquil Formation contains the following trace fossils: Zoophycos, Chondrites, Phycosiphon, Nereites missouriensis, Lockeiasiliquaria, Parataenidium, Ophiomorpha, Rhizocorallium and possibly also Psammichnites. [5]
Ranquil Formation | |
---|---|
Stratigraphic range: Miocene– Pliocene | |
Type | Geological formation |
Underlies | Tubul Formation |
Overlies | Lebu Group |
Lithology | |
Primary | Conglomerate with clay and silt matrix, breccia, sandstone, siltstone, mudstone |
Other | Conglomerate with sand matrix |
Location | |
Coordinates | 37°36′S 73°42′W / 37.6°S 73.7°W |
Approximate paleocoordinates | 37°54′S 71°24′W / 37.9°S 71.4°W |
Region | Bío Bío Region |
Country | Chile |
Type section | |
Named for | Caleta Ranquil |
Named by | Juan Tavera |
Year defined | 1942 |
The Ranquil Formation ( Spanish: Formación Ranquil) is a Miocene and Pliocene sedimentary formation located in Arauco Province in south–central Chile, including outcrops in Mocha Island. The formation has its greatest thicknesses in the south-west, where its sediments were largely deposited in marine conditions. It overlies unconformably sedimentary formations of the Paleocene- Eocene Lebu Group. [1] The formation is part of the fill of Arauco Basin which is a sedimentary basin that extends south of Concepción. [2]
Macrofossils of the formation are similar to those of Navidad ( 34° S) and Lacui Formations ( 43° S), two nearby Miocene marine formations. [3]
The base of the Ranquil Formation is the so-called "main unconformity", which is thought to have been formed by erosion during a period of tectonic inversion. [4]
The formation was first defined in 1942 by Juan Tavera. [1]
The formation has been subdivided into five units, with the lowermost being made up of sandstone and shale, and the second lowest one being made up of a conglomerate. The middle unit is made up of mudrock and massive sandstone. At some places the middle unit is overlain by a unit made up of sandstone with thin layers of conglomerate and sandstone that has been bioturbated. The uppermost unit include a breccia and the so-called Huenteguapi sandstone. [2] The sediments of Huenteguapi sandstone evidences that a megatsunami struck the coast of south–central Chile in the Pliocene, [2] which has been linked to the hypothetical Eltanin impact.
The Ranquil Formation contains the following trace fossils: Zoophycos, Chondrites, Phycosiphon, Nereites missouriensis, Lockeiasiliquaria, Parataenidium, Ophiomorpha, Rhizocorallium and possibly also Psammichnites. [5]