Chacarilla Formation

{{Infobox rockunit

| name = Chacarilla Formation

| image =

| caption =

| type = Geological formation

| period = Tithonian

| age = Oxfordian-Aptian
~{{fossil range|160|120}}

| prilithology = Sandstone, shale

| otherlithology =

| namedfor = Quebrada de Chacarilla

| namedby =

| region = Tarapacá Region

| country = {{CHL}}

| 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 Characilla}}) 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.{{in lang|es}} [http://www.monumentos.cl/monumentos/santuarios-de-la-naturaleza/quebrada-chacarilla Quebrada de Chacarilla] - Consejo de Monumentos Naturales de Chile

Description

File:Stratigraphic column - Chacarilla Formation, Chile.jpg

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.

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.Rubilar Rogers et al., 2008, p.177 The top of the formation is not younger than Aptian.Moreno et al., 2012, p.75

Fossil content

File:Dinosaur tracksite - Chacarilla Formation, Chile.jpg

Fossil stegosaur, sauropod and theropod tracks and fossil flora have been reported from the formation.Weishampel et al., 2004, pp.517-607

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).Moreno et al., 2012, p.77 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}}.Moreno et al., 2012, p.79

Additionally, in the Jurassic part of the formation, fossil flora was reported, containing fossils of Posidonomya, Perisphinctes,Leonardi, 1994, p.65 Baiera sp., Brachyphyllum sp., Cladophlebis sp., Dictyophyllum sp., Equisetites sp., Nilsonia sp., Pterophyllum sp., Ptilophyllum sp., Taeniopteris sp., and Filicales.[https://paleobiodb.org/classic/displayCollResults?collection_no=29505 Quebrada Juan de Morales] at Fossilworks.org

References

= 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=http://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 }}

Chacarilla Formation

Description

Fossil content

See also

References

= Bibliography =

Further reading