The Mealla 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 ...

of the

Santa Bárbara Subgroup Santa Claus, also known as Father Christmas, Saint Nicholas, Saint Nick, Kris Kringle, or simply Santa, is a legendary figure originating in Western Christian culture who is said to bring children gifts during the late evening and overnigh ...

, part of the

Salta Group Salta () is the capital and largest city in the Argentine province of the same name. With a population of 618,375 according to the 2010 census, it is also the 7th most-populous city in Argentina. The city serves as the cultural and economic ce ...

in the

Salta Basin Salta Basin or Salta Rift Basin is a sedimentary basin located in the Argentine Northwest. The basin started to accumulate sediments in the Early Cretaceous (Neocomian) and at present it has sedimentary deposits reaching thicknesses of . The basin ...

in northwestern

Argentina Argentina (), officially the Argentine Republic ( es, link=no, República Argentina), is a country in the southern half of South America. Argentina covers an area of , making it the second-largest country in South America after Brazil, t ...

whose strata date back to the

Middle Middle or The Middle may refer to: * Centre (geometry), the point equally distant from the outer limits. Places * Middle (sheading), a subdivision of the Isle of Man * Middle Bay (disambiguation) * Middle Brook (disambiguation) * Middle Creek (d ...

Late Paleocene The Thanetian is, in the ICS Geologic timescale, the latest age or uppermost stratigraphic stage of the Paleocene Epoch or Series. It spans the time between . The Thanetian is preceded by the Selandian Age and followed by the Ypresian Age (part ...

of the

Paleogene The Paleogene ( ; also spelled Palaeogene or Palæogene; informally Lower Tertiary or Early Tertiary) is a geologic period and system that spans 43 million years from the end of the Cretaceous Period million years ago (Mya) to the beginning of ...

Description

The Mealla 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 ranging upward to

siltstone Siltstone, also known as aleurolite, is a clastic sedimentary rock that is composed mostly of silt. It is a form of mudrock with a low clay mineral content, which can be distinguished from shale by its lack of fissility.Blatt ''et al.'' 1980, ...

s with a basal

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 ...

bed. The formation

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 ...

overlies the

Yacoraite Formation The Yacoraite Formation is a largely Mesozoic geologic formation. The deposits of this formation mainly date from the Maastrichtian of the Upper Cretaceous, but the Cretaceous–Paleogene boundary (K–T boundary) runs right through this formation ...

and is overlain by the

Thanetian The Thanetian is, in the ICS Geologic timescale, the latest age or uppermost stratigraphic stage of the Paleocene Epoch or Series. It spans the time between . The Thanetian is preceded by the Selandian Age and followed by the Ypresian Age (part ...

Maíz Gordo Formation. The thickness of the formation ranges from .Narváez, 2009, p.22 The formation is the lowermost unit in the

, representing the post-rift phase of the

. The Mealla Formation was 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 ...

. Other parts of the formation contain freshwater

stromatolite Stromatolites () or stromatoliths () are layered sedimentary formations ( microbialite) that are created mainly by photosynthetic microorganisms such as cyanobacteria, sulfate-reducing bacteria, and Pseudomonadota (formerly proteobacteria). ...

s, interpreted as deposited in a shallow

lacustrine A lake is an area filled with water, localized in a basin, surrounded by land, and distinct from any river or other outlet that serves to feed or drain the lake. Lakes lie on land and are not part of the ocean, although, like the much larger ...

environment.Narváez, 2009, p.23 The basal conglomerate is thick, matrix-supported with 80% of the clasts coming from

quartzite Quartzite is a hard, non- foliated metamorphic rock which was originally pure quartz sandstone.Essentials of Geology, 3rd Edition, Stephen Marshak, p 182 Sandstone is converted into quartzite through heating and pressure usually related to tec ...

s from the

Cambrian The Cambrian Period ( ; sometimes symbolized Ꞓ) was the first geological period of the Paleozoic Era, and of the Phanerozoic Eon. The Cambrian lasted 53.4 million years from the end of the preceding Ediacaran Period 538.8 million years ag ...

Mesón Group Mesón Group ( es, Grupo Mesón) is a Cambrian to Early Ordovician sedimentary formation located in the Argentine Northwest and nearby parts of Bolivia. The group members rest unconformably on top of the Ediacaran–Cambrian Puncoviscana Formati ...

, with the remainder of the clasts provenanced by the

Precambrian The Precambrian (or Pre-Cambrian, sometimes abbreviated pꞒ, or Cryptozoic) is the earliest part of Earth's history, set before the current Phanerozoic Eon. The Precambrian is so named because it preceded the Cambrian, the first period of th ...

Puncoviscana Formation Puncoviscana Formation ( es, Formación Puncoviscana) is a formation of sedimentary and metasedimentary rocks Late Ediacaran and Lower Cambrian age, estimated at between 700 and 535 Ma, that crop out in the Argentine Northwest. Most of the formati ...

and the quartzarenites of the

Santa Victoria Group Santa Claus, also known as Father Christmas, Saint Nicholas, Saint Nick, Kris Kringle, or simply Santa, is a legendary figure originating in Western Christian culture who is said to bring children gifts during the late evening and overnigh ...

. The conglomeratic section also contains

paleosol In the geosciences, paleosol (''palaeosol'' in Great Britain and Australia) is an ancient soil that formed in the past. The precise definition of the term in geology and paleontology is slightly different from its use in soil science. In geol ...

s.Sánchez & Marquillas, 2009, p.389 The pollen analysis performed by Quattrocchio et al. in 1997 indicated a phase of higher aridity during the deposition of the Mealla Formation.Narváez, 2009, p.172 The formation was initially described as

Riochican The Riochican ( es, Riochiquense) age is a period of geologic time (57.0–54.0 Ma) within the Paleocene and Eocene epochs of the Paleogene, used more specifically within the South American land mammal ages (SALMA). It follows the Peligran and pre ...

, and later as

Itaboraian The Itaboraian ( pt, Itaboraiense) age is a period within the Early Eocene geologic time (53.0–50.0 Ma) epoch of the Paleogene, used more specifically with South American land mammal ages (SALMA). It follows the Riochican and precedes the Cas ...

, but after the redefinition of the

Itaboraí Formation The Itaboraí Formation ( pt, Formação Itaboraí) is a highly fossiliferous geologic formation and LagerstätteKellner & Campos, 1999, p.399 of the Itaboraí Basin in Rio de Janeiro, southeastern Brazil. The formation reaching a thickness ...

Early Eocene In the geologic timescale the Ypresian is the oldest age (geology), age or lowest stage (stratigraphy), stratigraphic stage of the Eocene. It spans the time between , is preceded by the Thanetian Age (part of the Paleocene) and is followed by th ...

, the Mealla Formation is

Peligran The Peligran ( es, Peligrense) age is a period of geologic time (62.5–59.0 Ma) within the Paleocene epoch of the Paleogene, used more specifically with South American land mammal ages (SALMA). It follows the Tiupampan and precedes the Riochican a ...

to Riochican in age. The Mealla Formation is correlated with the

Río Loro Formation The Río Loro Formation is a geological formation of the Sierras Pampeanas in Tucumán Province Argentina whose strata date back to the Late Paleocene of the Paleogene, or Riochican in the SALMA classification. The formation has been deposited in ...

that crops out in the

Sierras Pampeanas The Sierras Pampeanas (also called Central Sierras or Pampas Sierras) (English: Pampas Mountains) is a geographical region of Argentina. The Sierras Pampeanas are a chain of mountains that rise sharply from the surrounding pampa region of ...

to the southeast of the Salta Basin.

Fossil content

The following fossils were reported from the formation:Mealla 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 * Mammals **

Notoungulata Notoungulata is an extinct order of mammalian ungulates that inhabited South America from the early Paleocene to the Holocene, living from approximately 61 million to 11,000 years ago. Notoungulates were morphologically diverse, with forms resem ...

*** '' Archaeogaia macachaae'' ***

Henricosborniidae Henricosborniidae is a family of extinct notoungulate mammals known from the Late Paleocene to Middle Eocene of Argentina, Bolivia and Brazil. The name honors U.S. paleontologist Henry Fairfield Osborn. Description Henricosborniidae is a gr ...

**** '' Simpsonotus major''Pascual et al., 1978 **** '' S. praecursor'' * Reptiles ** Pelomedusidae indet. ** '' Sebecus ayrampu'' *

Pollen Pollen is a powdery substance produced by seed plants. It consists of pollen grains (highly reduced microgametophytes), which produce male gametes (sperm cells). Pollen grains have a hard coat made of sporopollenin that protects the gametop ...

Aquifoliaceae ''Ilex'' (), or holly, is a genus of over 570 species of flowering plants in the family Aquifoliaceae, and the only living genus in that family. ''Ilex'' has the most species of any woody dioecious angiosperm genus. The species are evergreen o ...

*** '' Gemmatricolpites subsphaericus''Narváez, 2009, p.134 **

Haloragaceae Haloragaceae (the watermilfoil family) is a eudicot flowering plant family in the order Saxifragales, based on the phylogenetic APG system. In the Cronquist system, it was included in the order Haloragales. Description The Haloragaceae are ...

*** '' Myriophyllumpollenites sp.''Narváez, 2009, p.109 ** Oenotheraceae *** '' Corsinipollenites menendezii''Narváez, 2009, p.108 **

Pandanaceae Pandanaceae is a family of flowering plants native to the tropics and subtropics of the Old World, from West Africa through the Pacific. It contains 982 known species in five genera, of which the type genus, ''Pandanus'', is the most important, w ...

*** '' Pandaniidites texus'' **

Salicaceae The Salicaceae is the willow family of flowering plants. The traditional family (Salicaceae ''sensu stricto'') included the willows, poplar, aspen, and cottonwoods. Genetic studies summarized by the Angiosperm Phylogeny Group (APG) have greatly ...

*** '' Rousea patagonica''Narváez, 2009, p.171 **

Ulmaceae The Ulmaceae () are a family of flowering plants that includes the elms (genus ''Ulmus''), and the zelkovas (genus ''Zelkova''). Members of the family are widely distributed throughout the north temperate zone, and have a scattered distribution ...

(''

Phyllostylon ''Phyllostylon'' is a genus of plant in family Ulmaceae. Species include: * ''Phyllostylon brasiliense'' Capan. ex Benth. & Hook.f. * ''Phyllostylon orthopterum ''Phyllostylon orthopterum'' is a species of plant in the family Ulmaceae. It is ...

'') *** '' Verrustephanoporites simplex''Narváez, 2009, p.115

References

Bibliography

* * * * {{cite LSA , last=Pascual , first=R. , first2=M.G. , last2=Vucetich , first3=J. , last3=Fernández , year=1978 , title=Los primeros mamiferos (notoungulata, henricosborniidae) de la Formacion Mealla (Grupo Salta, subgrupo Santa Barbara) : sus implicancias filogeneticas, taxonomicas y cronologicas , journal=

Ameghiniana ''Ameghiniana'' is a peer-reviewed scientific journal covering palaeontology published by the Asociación Paleontológica Argentina. It is named after the 19th century Italian Argentine palaeontologist Florentino Ameghino. The discovery of many di ...

, volume=15 , pages=366-390 Geologic formations of Argentina Paleocene Series of South America Paleogene Argentina Selandian Stage Thanetian Stage Peligran Riochican Sandstone formations Siltstone formations Conglomerate formations Fluvial deposits Lacustrine deposits Formations Fossiliferous stratigraphic units of South America Paleontology in Argentina Geology of Jujuy Province

Description

Fossil content

See also

References

Bibliography