The Dorotea Formation is a geological

formation Formation may refer to: Linguistics * Back-formation, the process of creating a new lexeme by removing or affixes * Word formation, the creation of a new word by adding affixes Mathematics and science * Cave formation or speleothem, a secondary ...

in the Río de Las Chinas Valley of the

Magallanes Basin The Magallanes Basin or Austral Basin is a major sedimentary basin in southern Patagonia. The basin covers a surface of about and has a NNW-SSE oriented shape. The basin is bounded to the west by the Andes mountains and is separated from the Malv ...

Patagonia Patagonia () refers to a geographical region that encompasses the southern end of South America, governed by Argentina and Chile. The region comprises the southern section of the Andes Mountains with lakes, fjords, temperate rainforests, and ...

Chile Chile, officially the Republic of Chile, is a country in the western part of South America. It is the southernmost country in the world, and the closest to Antarctica, occupying a long and narrow strip of land between the Andes to the eas ...

whose strata date back to the

Campanian The Campanian is the fifth of six ages of the Late Cretaceous Epoch on the geologic timescale of the International Commission on Stratigraphy (ICS). In chronostratigraphy, it is the fifth of six stages in the Upper Cretaceous Series. Campani ...

Maastrichtian The Maastrichtian () is, in the ICS geologic timescale, the latest age (uppermost stage) of the Late Cretaceous Epoch or Upper Cretaceous Series, the Cretaceous Period or System, and of the Mesozoic Era or Erathem. It spanned the interv ...

of the

Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the younger of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''creta'', ...

.Dorotea Formation
at

Fossilworks Fossilworks is a portal which provides query, download, and analysis tools to facilitate access to the Paleobiology Database, a large relational database assembled by hundreds of paleontologists from around the world. History Fossilworks was cre ...

.org

Description

The Dorotea Formation was first described by Katz in 1963. The formation comprises

sandstone Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks. Most sandstone is composed of quartz or feldspar (both silicates ...

s with frequent

conglomerate Conglomerate or conglomeration may refer to: * Conglomerate (company) * Conglomerate (geology) * Conglomerate (mathematics) In popular culture: * The Conglomerate (American group), a production crew and musical group founded by Busta Rhymes ** C ...

lenses, concretionary levels and

claystone Mudrocks are a class of fine-grained siliciclastic sedimentary rocks. The varying types of mudrocks include siltstone, claystone, mudstone, slate, and shale. Most of the particles of which the stone is composed are less than and are too sm ...

s. The Dorotea Formation includes calcareous sandstones with abundant marine invertebrate and fragmentary vertebrate fossils. Hervé et al. (2004) obtained a maximum radiometric age of 67.4 ± 1.5 Ma from detrital

zircon Zircon () is a mineral belonging to the group of nesosilicates and is a source of the metal zirconium. Its chemical name is zirconium(IV) silicate, and its corresponding chemical formula is Zr SiO4. An empirical formula showing some of th ...

s contained in sandstones of the Dorotea Formation. The mudstones and

s of the formation were deposited in a

fluvial In geography and geology, fluvial processes are associated with rivers and streams and the deposits and landforms created by them. When the stream or rivers are associated with glaciers, ice sheets, or ice caps, the term glaciofluvial or fluv ...

environment Environment most often refers to: __NOTOC__ * Natural environment, all living and non-living things occurring naturally * Biophysical environment, the physical and biological factors along with their chemical interactions that affect an organism or ...

. The formation conformably overlies the Tres Pasos Formation and is

unconformably An unconformity is a buried erosional or non-depositional surface separating two rock masses or strata of different ages, indicating that sediment deposition was not continuous. In general, the older layer was exposed to erosion for an interval o ...

overlain by the

Lutetian The Lutetian is, in the geologic timescale, a stage (stratigraphy), stage or age (geology), age in the Eocene. It spans the time between . The Lutetian is preceded by the Ypresian and is followed by the Bartonian. Together with the Bartonian it ...

Bartonian The Bartonian is, in the ICS's geologic time scale, a stage or age in the middle Eocene Epoch or Series. The Bartonian Age spans the time between . It is preceded by the Lutetian and is followed by the Priabonian Age. Stratigraphic defin ...

Man Aike Formation.Goin et al., 2020, p.9 The thickness of the formation ranges from in the

Sierra Baguales Sierra Baguales or Sierra de los Baguales is a mountain range in the southernmost Andes. Sierra Baguales is a long east–west chain, secondary to the main chain of the Andes that lie further west. It lies along the border between Chile and Arge ...

in the north to in the eponymous Sierra Dorotea in the south.Otero et al., 2015, p.240

Fossil content

The following fossils were reported from the formation:Río de las Chinas Valley
at

.org * Amphibians ** Anura indet. ** Panchelidae indet. * Reptiles ** '' Aristonectes sp.'' ** '' cf. Yaminuechelys sp.''Alarcón Muñoz et al., 2020 ** Aristonectinae indet.Otero et al., 2015 ** Elasmosauridae indet. ** '' Stegouros elengassen'' ** Sauropoda indet. **

Enantiornithes The Enantiornithes, also known as enantiornithines or enantiornitheans in literature, are a group of extinct avialans ("birds" in the broad sense), the most abundant and diverse group known from the Mesozoic era. Almost all retained teeth and cl ...

indet. ** Megaraptoridae indet. **

Ornithurae Ornithurae (meaning "bird tails" in Greek) is a natural group which includes the common ancestor of '' Ichthyornis'', '' Hesperornis'', and all modern birds as well as all other descendants of that common ancestor. Classification Ernst Haeckel c ...

indet. **

Unenlagiinae Unenlagiinae is a subfamily of long-snouted paravian theropods. They are traditionally considered to be members of Dromaeosauridae, though some authors place them into their own family, Unenlagiidae, alongside the subfamily Halszkaraptorinae. ...

indet. ** Theropoda indet. ** Ornithischia indet. * Mammals ** '' Magallanodon baikashkenke''Goin et al., 2020 **'' Orretherium tzen'' ** Mammalia indet. * Fish ** '' Ischyrhiza chilensis'' ** '' Carcharias sp.'' ** Serratolamna indet. *

Insect Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body (head, thorax and abdomen), three pairs ...

s ** '' Dorotheus guidensis''Kuschel, 1959 *

Bivalve Bivalvia (), in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class of marine and freshwater molluscs that have laterally compressed bodies enclosed by a shell consisting of two hinged parts. As a group, biv ...

s ** '' Pterotrigonia cazadoriana''Otero et al., 2009 *

Ammonite Ammonoids are a group of extinct marine mollusc animals in the subclass Ammonoidea of the class Cephalopoda. These molluscs, commonly referred to as ammonites, are more closely related to living coleoids (i.e., octopuses, squid and cuttle ...

s ** '' Gunnarites sp.'' ** '' Pachydiscus aff. gollevilensis''

References

Bibliography

* * * * * {{cite LSA , last=Kuschel , first=G , year=1959 , title=Un curculionido del Cretácico Superior - primer insecto fósil de Chile , journal= Investigaciones Zoológicas Chilenas , volume=5 , pages=49-54 Geologic formations of Chile Upper Cretaceous Series of South America Cretaceous Chile Maastrichtian Stage of South America Campanian Stage Sandstone formations Shale formations Conglomerate formations Fluvial deposits Shallow marine deposits Formations Fossiliferous stratigraphic units of South America Paleontology in Chile Geology of Patagonia Formations

Description

Fossil content

See also

References

Bibliography