{{Short description|Geologic formation in Chile}} {{Infobox rockunit | name = Chacarilla Formation | image = | caption = | type = Geological formation | period = Tithonian | age = Oxfordian-Aptian<br />~{{fossil range|160|120}} | prilithology = Sandstone, shale | otherlithology = | namedfor = Quebrada de Chacarilla | namedby = | region = Tarapacá Region | country = Chile | coordinates = {{coord|20.6|S|69.1|W|display=inline,title}} | paleocoordinates = {{coord|21.5|S|36.1|W|display=inline}} | unitof = | subunits = | underlies = Cerro Empexa Formation | overlies = ''not exposed'' | thickness = min. {{convert|1100|m|ft|abbr=on}} | extent = Tarapacá Basin | area = | map = {{Location map+ | Chile | relief = 1 | width = 200 | float = center | places = {{Location map~ | Chile | lat_deg = -20.6 | lon_deg = -69.1 | mark = Green-blue pog.svg | marksize = 12 }} }} | map_caption = }} The '''Chacarilla Formation''' ({{langx|es|Formación Chacarilla}}) is an Oxfordian to Early Cretaceous geologic formation of the Tarapacá Basin in northern Chile, close to the border with Bolivia. The marine and fluvial formation preserves several dinosaur trackways and has been declared a Natural Sanctuary ({{langx|es|Santuario de la Naturaleza}}) in 2004.<ref name=CMN>{{in lang|es}} [http://www.monumentos.cl/monumentos/santuarios-de-la-naturaleza/quebrada-chacarilla Quebrada de Chacarilla] - Consejo de Monumentos Naturales de Chile</ref>
== Description == thumb|left|200px|Stratigraphic column of the formation The formation comprises a sequence of rhythmically alternating shales and red sandstones with a minimum thickness of {{convert|1100|m|ft}}. The lower part of the formation was deposited under marine conditions and the upper part in a meandering river floodplain and point bar environment. Paleocurrent analysis demonstrated a flow direction towards the west, northwest and west-northwest.<ref name=Rubilar2008_p177/>
The formation contains ichnofossils of theropods and ornithopods, occurring in the Early Cretaceous upper part of the formation, which is marked by an angular unconformity, overlain by volcanic and clastic rocks of the Late Cretaceous to Early Paleocene Cerro Empexa Formation.<ref name=Rubilar2008_p177>Rubilar Rogers et al., 2008, p.177</ref> The top of the formation is not younger than Aptian.<ref name=Moreno2012_p75>Moreno et al., 2012, p.75</ref>
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== Fossil content == left|thumb|300px|Dinosaur tracksite of the Chacarilla Formation Fossil stegosaur, sauropod and theropod tracks and fossil flora have been reported from the formation.<ref name="dinosaurdistribution">Weishampel et al., 2004, pp.517-607</ref>
The fourteen trackways of the Chacarilla III tracksite consist of 76 individual footprints. Two of the trackways consist of large ornithopod footprints (average footprint length {{convert|39|cm|in}} and average width {{convert|32|cm|in}}). Two other trackways consist of small theropod footprints (less than {{convert|25|cm|in}} long).<ref name=Moreno2012_p77>Moreno et al., 2012, p.77</ref> The other ten trackways were made by large theropods (footprint length more than {{convert|30|cm|in}}). The large theropod tracks are tri− and tetradactyl, mesaxonic, and have lengths and widths between {{convert|31|to|65|cm|in}} and {{convert|21|to|46|cm|in}}, respectively. Nearly all digit impressions possess claw marks, but they lack clear impressions of digital pads. The stride length varies between {{convert|230|and|307|cm|ft}}. The speed of the dinosaurs leaving the tracks is estimated at {{convert|4|to|7|km/h|mph}}.<ref name=Moreno2012_p79>Moreno et al., 2012, p.79</ref>
Additionally, in the Jurassic part of the formation, fossil flora was reported, containing fossils of ''Posidonomya'', ''Perisphinctes'',<ref name=Leonardi1994_p65>Leonardi, 1994, p.65</ref> ''Baiera sp.'', ''Brachyphyllum sp.'', ''Cladophlebis sp.'', ''Dictyophyllum sp.'', ''Equisetites sp.'', ''Nilsonia sp.'', ''Pterophyllum sp.'', ''Ptilophyllum sp.'', ''Taeniopteris sp.'', and Filicales.<ref name=FWChacarilla>[https://paleobiodb.org/classic/displayCollResults?collection_no=29505 Quebrada Juan de Morales] at Fossilworks.org</ref>
== See also == * List of dinosaur-bearing rock formations ** List of stratigraphic units with ornithischian tracks *** Stegosaur tracks * Arcabuco Formation, contemporaneous ichnofossil-bearing formation in Colombia * La Puerta Formation, contemporaneous ichnofossil-bearing formation in Bolivia * Baños del Flaco Formation, contemporaneous ichnofossil-bearing formation in central Chile
== References == {{reflist|20em}}
=== Bibliography === * {{citation |last=Leonardi |first=Giuseppe |year=1994 |title=Annotated Atlas of South America Tetrapod Footprints (Devonian to Holocene) with an appendix on Mexico and Central America |url=https://www.researchgate.net/publication/309643073 |publisher=Ministerio de Minas e Energia - Companhia de Pesquisa de Recursos Minerais, Geological Service of Brazil |pages=1–248 |accessdate=2019-03-25}} * {{citation |last1=Moreno |first1=K. |last2=De Valais |first2=S. |last3=Blanco |first3=N. |last4=Tomlinson |first4=A.J. |last5=Jacay |first5=J. |last6=Calvo |first6=J.O. |year=2012 |title=Large theropod dinosaur footprint associations in western Gondwana: Behavioural and palaeogeographic implications |url=https://www.app.pan.pl/archive/published/app57/app20100119.pdf |journal=Acta Palaeontologica Polonica |volume=57 |pages=73–83 |doi=10.4202/app.2010.0119 |accessdate=2019-03-08}} 50px Material was copied from this source, which is available under a [https://creativecommons.org/licenses/by/4.0/ Creative Commons Attribution 4.0 International License]. * {{citation |last1=Rubilar Rogers |first1=David |last2=Moreno |first2=Karen |last3=Blanco |first3=Nicolás |last4=Calvo |first4=Jorge O. |year=2008 |title=Theropod Dinosaur Trackways from the Lower Cretaceous of the Chacarilla Formation, Chile |url=https://www.andeangeology.cl/index.php/revista1/article/view/V35n1-a09/415 |journal=Revista Geológica de Chile |volume=35 |pages=175–184 |accessdate=2019-03-08}} * {{citation |last1=Weishampel |first1=David B. |author2-link=Peter Dodson |last2=Dodson |first2=Peter |author3-link=Halszka Osmólska |last3=Osmólska |first3=Halszka |year=2004 |title=The Dinosauria, 2nd edition |url=https://books.google.com/books?id=vtZFDb_iw40C |publisher=Berkeley: University of California Press |pages=1–880 |accessdate=2019-02-21 |isbn=0-520-24209-2 |author1-link=David B. Weishampel }}
== Further reading == * C. G. Oliver and C.A. Menéndez. 1968. Geología de la Quebrada Juan de Morales, Tarapacá, Chile y su flora Jurásica. Terceras Jornadas Geologicas Argentinas 163–171 * R. J. Dingman and C. Galli O. 1965. Geology and ground-water resources of the Pica area, Tarapacá Province, Chile. United States Geological Survey Bulletin 1189:1-113
{{Geology of Chile}}
Category:Geologic formations of Chile Category:Lower Cretaceous Series of South America Category:Jurassic System of South America Category:Late Jurassic South America Category:Mesozoic Chile Category:Aptian Stage Category:Barremian Stage Category:Hauterivian Stage Category:Valanginian Stage Category:Berriasian Stage Category:Tithonian Stage Category:Kimmeridgian Stage Category:Oxfordian Stage Category:Sandstone formations Category:Shale formations Category:Fluvial deposits Category:Ichnofossiliferous formations Category:Fossiliferous stratigraphic units of South America Category:Paleontology in Chile Category:Geology of Tarapacá Region Category:National Monuments of Chile