Lebu Group

Lebu Group
Stratigraphic range: Paleocene–Eocene
Type	Stratigraphic group
Sub-units	Millongue Formation Trihueco Formation Boca Lebu Formation Curanilahue Formation
Underlies	Ranquil Formation
Overlies	Quiriquina Formation
Lithology
Primary	Shale, sandstone, siltstone, mudstone
Other	Coal
Location
Coordinates	37°36′S73°42′W / 37.6°S 73.7°W / -37.6; -73.7
Approximate paleocoordinates	40°06′S64°12′W / 40.1°S 64.2°W / -40.1; -64.2
Region	Bío Bío Region
Country	Chile
Extent	Arauco Basin
Type section
Named for	Lebu
Lebu Group (Chile)

Lebu Group is stratigraphic unit of Arauco Basin in south-central Chile. The group consists of a sequence of four formations, of both marine and nonmarine origin, deposited between the Early Paleocene and Middle Eocene. ^[1]

Description

The group is made up of four formations, from youngest to oldest these are: Millongue Formation, ^{[note 1]} Trihueco Formation, Boca Lebu Formation and Curanilahue Formation. ^[1]

The Eocene Millongue Formation is composed of shale and siltstone of both marine and continental origin. Its top is marked by an unconformity, the so-called “main unconformity” of Arauco Basin, which is thought to have formed by erosion during a period of tectonic inversion. ^{[1] [3]}

Notes

1. What was previously known as Caleta Viel Formation is now considered to be the roof Millongue Formation. ^[2]

References

1. García A., Floreal (1968). "Estratigrafía del Terciario de Chile Central". In Ceccioni, Giovanni (ed.). El Terciario de Chile Zona Central (in Spanish). Santiago de Chile: Ediorial Andrés Bello.
2. Palma-Heldt, S.; Quinzio, L.A.; Bonilla, R.; Cisterna, K. (2009). Implicancias estratigráficas del primer registro de Notofagadites en el Paleógeno de la Cuenca de Arauco, Región del Bío-Bío, Chile (PDF). XII Congreso Geológico Chileno (in Spanish). Santiago, Chile. Archived from the original (PDF) on August 18, 2016.
3. Becerra, Juan; Contreras-Reyes, Eduardo; Arriagada, César (2013). "Seismic structure and tectonics of the southern Arauco Basin, south-central Chile (~ 38°S)". Tectonophysics . 592: 53–66. Bibcode:2013Tectp.592...53B. doi:10.1016/j.tecto.2013.02.012. hdl: 10533/238054 .