Ranquil Formation
| 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. The formation is part of the fill of Arauco Basin which is a sedimentary basin that extends south of Concepción.
Macrofossils of the formation are similar to those of Navidad (34° S) and Lacui Formations (43° S), two nearby Miocene marine formations.
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.
The formation was first defined in 1942 by Juan Tavera.