Lohan Cura Formation
Encyclopedia
The Lohan Cura Formation is a geologic formation
with outcrop
s in the Argentine
provinces of Río Negro
, Neuquén
, and Mendoza
. It is the second oldest Cretaceous
terrestrial formation in the Neuquén Basin.
The Lohan Cura Formation unconformably
overlies the terrestrial La Amarga Formation
. In some places it also overlies the older marine Agrio and Bajada Colorada Formations of the Mendoza Group through the same unconformity. It is in turn overlain by the Candeleros Formation
of the Neuquén Group
, separated by another unconformity. The Lohan Cura correlates with the Rayoso Formation
in some areas.
Period: Early Cretaceous
Faunal stage
: late Aptian
through Albian
Absolute Age
: ~117 to ~100 mya
of roughly equal thickness.
The lower (and therefore older) of the two is the Puesto Quiroga Member, approximately 85 meters thick. The lowest sediments in this formation are conglomerates
, overlain by sandstone
s and siltstone
s. The upper two-thirds of the member consists mainly of shale
s.
The Cullín Grande Member is the upper member within the formation, about 92 meters thick, which contains numerous stream
channels in sandstone. By the top of the column, siltstones and clay
stones become dominant.
fossil
s have been recovered from the Cullín Grande Member of the Lohan Cura, including:
The rebacchisaurid Rayososaurus
comes from the correlating Rayoso Formation in this same area.
Geologic formation
A formation or geological formation is the fundamental unit of lithostratigraphy. A formation consists of a certain number of rock strata that have a comparable lithology, facies or other similar properties...
with outcrop
Outcrop
An outcrop is a visible exposure of bedrock or ancient superficial deposits on the surface of the Earth. -Features:Outcrops do not cover the majority of the Earth's land surface because in most places the bedrock or superficial deposits are covered by a mantle of soil and vegetation and cannot be...
s in the Argentine
Argentina
Argentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...
provinces of Río Negro
Río Negro Province
Río Negro is a province of Argentina, located at the northern edge of Patagonia. Neighboring provinces are from the south clockwise Chubut, Neuquén, Mendoza, La Pampa and Buenos Aires. To the east lies the Atlantic Ocean.Its capital is Viedma...
, Neuquén
Neuquén Province
Neuquén is a province of Argentina, located in the west of the country, at the northern end of Patagonia. It borders Mendoza Province to the north, Rio Negro Province to the southeast, and Chile to the west...
, and Mendoza
Mendoza Province
The Province of Mendoza is a province of Argentina, located in the western central part of the country in the Cuyo region. It borders to the north with San Juan, the south with La Pampa and Neuquén, the east with San Luis, and to the west with the republic of Chile; the international limit is...
. It is the second oldest Cretaceous
Cretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...
terrestrial formation in the Neuquén Basin.
The Lohan Cura Formation unconformably
Unconformity
An unconformity is a buried erosion 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 of time before deposition of the younger, but the term is used to describe...
overlies the terrestrial La Amarga Formation
La Amarga Formation
The La Amarga Formation is a geologic formation with outcrops in the Argentine provinces of Río Negro, Neuquén, and Mendoza. It is the oldest Cretaceous terrestrial formation in the Neuquén Basin....
. In some places it also overlies the older marine Agrio and Bajada Colorada Formations of the Mendoza Group through the same unconformity. It is in turn overlain by the Candeleros Formation
Candeleros Formation
The Candeleros Formation is a geologic formation that outcrops in Río Negro, Neuquén, and Mendoza provinces of Argentina. It is the oldest formation in the Neuquén Group and belongs to the Rio Limay Subgroup...
of the Neuquén Group
Neuquén Group
The Neuquén Group is a group of geologic formations found in Argentina. Rocks in the Neuquén Group fall within the Cenomanian to early Campanian stages of the Late Cretaceous Period, about 100 million to 80 million years in age...
, separated by another unconformity. The Lohan Cura correlates with the Rayoso Formation
Rayoso Formation
The Rayoso Formation is a geological formation in the Neuquén Province of Argentina whose strata date back to the Aptian stage of the Early Cretaceous. Dinosaur remains are among the fossils that have been recovered from the formation.-Vertebrate paleofauna:...
in some areas.
Age
Era: MesozoicMesozoic
The Mesozoic era is an interval of geological time from about 250 million years ago to about 65 million years ago. It is often referred to as the age of reptiles because reptiles, namely dinosaurs, were the dominant terrestrial and marine vertebrates of the time...
Period: Early Cretaceous
Cretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...
Faunal stage
Faunal stage
In chronostratigraphy, a stage is a succession of rock strata laid down in a single age on the geologic timescale, which usually represents millions of years of deposition. A given stage of rock and the corresponding age of time will by convention have the same name, and the same boundaries.Rock...
: late Aptian
Aptian
The Aptian is an age in the geologic timescale or a stage in the stratigraphic column. It is a subdivision of the Early or Lower Cretaceous epoch or series and encompasses the time from 125.0 ± 1.0 Ma to 112.0 ± 1.0 Ma , approximately...
through Albian
Albian
The Albian is both an age of the geologic timescale and a stage in the stratigraphic column. It is the youngest or uppermost subdivision of the Early/Lower Cretaceous epoch/series. Its approximate time range is 112.0 ± 1.0 Ma to 99.6 ± 0.9 Ma...
Absolute Age
Geochronology
Geochronology is the science of determining the age of rocks, fossils, and sediments, within a certain degree of uncertainty inherent to the method used. A variety of dating methods are used by geologists to achieve this, and schemes of classification and terminology have been proposed...
: ~117 to ~100 mya
Composition
The Lohan Cura Formation contains two membersGeologic unit
A geological unit is a volume of rock or ice of identifiable origin and age range that is defined by the distinctive and dominant, easily mapped and recognizable petrographic, lithologic or paleontologic features that characterize it....
of roughly equal thickness.
The lower (and therefore older) of the two is the Puesto Quiroga Member, approximately 85 meters thick. The lowest sediments in this formation are conglomerates
Conglomerate (geology)
A conglomerate is a rock consisting of individual clasts within a finer-grained matrix that have become cemented together. Conglomerates are sedimentary rocks consisting of rounded fragments and are thus differentiated from breccias, which consist of angular clasts...
, overlain by sandstone
Sandstone
Sandstone is a sedimentary rock composed mainly of sand-sized minerals or rock grains.Most sandstone is composed of quartz and/or feldspar because these are the most common minerals in the Earth's crust. Like sand, sandstone may be any colour, but the most common colours are tan, brown, yellow,...
s and siltstone
Siltstone
Siltstone is a sedimentary rock which has a grain size in the silt range, finer than sandstone and coarser than claystones.- Description :As its name implies, it is primarily composed of silt sized particles, defined as grains 1/16 - 1/256 mm or 4 to 8 on the Krumbein phi scale...
s. The upper two-thirds of the member consists mainly of shale
Shale
Shale is a fine-grained, clastic sedimentary rock composed of mud that is a mix of flakes of clay minerals and tiny fragments of other minerals, especially quartz and calcite. The ratio of clay to other minerals is variable. Shale is characterized by breaks along thin laminae or parallel layering...
s.
The Cullín Grande Member is the upper member within the formation, about 92 meters thick, which contains numerous stream
Stream
A stream is a body of water with a current, confined within a bed and stream banks. Depending on its locale or certain characteristics, a stream may be referred to as a branch, brook, beck, burn, creek, "crick", gill , kill, lick, rill, river, syke, bayou, rivulet, streamage, wash, run or...
channels in sandstone. By the top of the column, siltstones and clay
Clay
Clay is a general term including many combinations of one or more clay minerals with traces of metal oxides and organic matter. Geologic clay deposits are mostly composed of phyllosilicate minerals containing variable amounts of water trapped in the mineral structure.- Formation :Clay minerals...
stones become dominant.
Paleontology
Numerous tetrapodTetrapod
Tetrapods are vertebrate animals having four limbs. Amphibians, reptiles, birds and mammals are all tetrapods; even snakes and other limbless reptiles and amphibians are tetrapods by descent. The earliest tetrapods evolved from the lobe-finned fishes in the Devonian...
fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
s have been recovered from the Cullín Grande Member of the Lohan Cura, including:
- several turtleTurtleTurtles are reptiles of the order Testudines , characterised by a special bony or cartilaginous shell developed from their ribs that acts as a shield...
s (including 2 species of Prochelidella) - rebbachisaurid sauropods
- possible titanosaurian sauropods (including AgustiniaAgustiniaAgustinia is a genus of sauropod dinosaur from the Early Cretaceous Period of South America. Like all known sauropods, it was quadrupedal and herbivorous. Although some sauropods are known to have body armor, Agustinias armor was unique even among sauropods...
and LigabuesaurusLigabuesaurusLigabuesaurus is a genus of dinosaur from the Early Cretaceous . It was a basal titanosaurid sauropod which lived in what is now Argentina. The type species, Ligabuesaurus leanzai, was described by Jose Bonaparte, Gonzalez Riga, and Sebastián Apesteguía in 2006, based on a partial skeleton...
)
The rebacchisaurid Rayososaurus
Rayososaurus
Rayososaurus is a genus of plant-eating sauropod dinosaur of the superfamily Diplodocoidea. It was found in the Rayoso Formation, in Patagonia, Argentina and lived about 99 million years ago . The type species is R...
comes from the correlating Rayoso Formation in this same area.
| Dinosaur Dinosaur Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of... s of the Lohan Cura Formation |
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|---|---|---|---|---|
| Genus | Species | Presence | Notes | Images |
Agustinia Agustinia Agustinia is a genus of sauropod dinosaur from the Early Cretaceous Period of South America. Like all known sauropods, it was quadrupedal and herbivorous. Although some sauropods are known to have body armor, Agustinias armor was unique even among sauropods... |
A. ligabuei |
Geographically located in the provincia de Nequen, Argentina. |
"Dorsal sacral and caudal neural arches, hindlimb elements, [and] osteoderms." |
 |