{{Short description|Chilean geologic formation}} {{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<br/>Trihueco Formation<br/>Boca Lebu Formation<br/>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.<ref name=Garcia1968>{{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=Editorial Andrés Bello|language=es}}</ref>
== 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.<ref>{{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 }}</ref>}} Trihueco Formation, Boca Lebu Formation and Curanilahue Formation.<ref name=Garcia1968/>
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.<ref name=Garcia1968/><ref name=Becerraetal2013>{{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 |hdl=10533/238054 |hdl-access=free }}</ref>
== Notes == {{Reflist|group=note}}
== References == {{reflist}}
{{Sedimentary formations and groups in Chile}}
Category:Geologic groups of Chile Category:Paleocene Series of South America Category:Eocene Series of South America Category:Paleogene Chile Category:Danian Stage Category:Selandian Stage Category:Thanetian Stage Category:Ypresian Stage Category:Lutetian Stage Category:Bartonian Stage Category:Shale groups Category:Sandstone groups Category:Siltstone groups Category:Mudstone groups Category:Coal groups Category:Geology of Biobío Region