Lebu Group

{{Infobox rockunit

| name = Lebu Group

| image =

| caption =

| type = Stratigraphic group

| period = Eocene

| age = Paleocene–Eocene

| prilithology = Shale, sandstone, siltstone, mudstone

| otherlithology = Coal

| namedfor = Lebu

| namedby =

| region = Bío Bío Region

| country = Chile

| coordinates = {{coord|37.6|S|73.7|W|display=inline,title}}

| paleocoordinates = {{coord|40.1|S|64.2|W|display=inline}}

| unitof =

| subunits = Millongue Formation
Trihueco Formation
Boca Lebu Formation
Curanilahue Formation

| underlies = Ranquil Formation

| overlies = Quiriquina Formation

| thickness =

| extent = Arauco Basin

| area =

| map = {{Location map+ | Chile

| relief = 1

| width = 250

| float = center

| places =

{{Location map~ | Chile

| lat_deg = -37.6

| lon_deg = -73.7

| mark = Orange pog.svg

| marksize = 12

}}

| map_caption =

}}

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.{{cite book|last=García A.|first=Floreal|chapter=Estratigrafía del Terciario de Chile Central |date=1968|title=El Terciario de Chile Zona Central |editor-last=Ceccioni |editor-first=Giovanni |location=Santiago de Chile |publisher=Ediorial Andrés Bello|language=es}}

Description

The group is made up of four formations, from youngest to oldest these are: Millongue Formation,{{refn|name=note 1|group=note|What was previously known as Caleta Viel Formation is now considered to be the roof Millongue Formation.{{cite conference |url=http://biblioserver.sernageomin.cl/opac/DataFiles/12993_v3_S10_009.pdf |archive-url=https://web.archive.org/web/20160818064247/http://biblioserver.sernageomin.cl/opac/DataFiles/12993_v3_S10_009.pdf |url-status=dead |archive-date=August 18, 2016 |title=Implicancias estratigráficas del primer registro de Notofagadites en el Paleógeno de la Cuenca de Arauco, Región del Bío-Bío, Chile |last1=Palma-Heldt |first1=S. |last2=Quinzio |first2=L.A. |last3=Bonilla |first3=R. |last4=Cisterna |first4=K. |date=2009 |location=Santiago, Chile |conference=XII Congreso Geológico Chileno |language=es }}}} Trihueco Formation, Boca Lebu Formation and Curanilahue Formation.

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.{{cite journal|last1=Becerra|first1=Juan|last2=Contreras-Reyes |first2=Eduardo |last3=Arriagada |first3=César |title=Seismic structure and tectonics of the southern Arauco Basin, south-central Chile (~ 38°S) |journal=Tectonophysics|date=2013|volume=592|pages=53–66 |doi=10.1016/j.tecto.2013.02.012|bibcode=2013Tectp.592...53B }}