Mesón Group ( es, Grupo Mesón) is a

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 ago ...

to Early Ordovician

sedimentary Sedimentary rocks are types of rock that are formed by the accumulation or deposition of mineral or organic particles at Earth's surface, followed by cementation. Sedimentation is the collective name for processes that cause these particles ...

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 secondar ...

located in the Argentine Northwest and nearby parts of

Bolivia , image_flag = Bandera de Bolivia (Estado).svg , flag_alt = Horizontal tricolor (red, yellow, and green from top to bottom) with the coat of arms of Bolivia in the center , flag_alt2 = 7 × 7 square p ...

. The group members rest

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 ...

on top of the Ediacaran–Cambrian

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 form ...

. According to G.F. Aceñolaza, the Mesón Basin the

sedimentary basin Sedimentary basins are region-scale depressions of the Earth's crust where subsidence has occurred and a thick sequence of sediments have accumulated to form a large three-dimensional body of sedimentary rock. They form when long-term subside ...

in which the Méson Group was deposited was located between the Arequipa and

Río de la Plata Craton The Rio de la Plata Craton (RPC) is a medium-sized continental block found in Uruguay, eastern Argentina and southern Brazil. During its complex and protracted history it interacted with a series other blocks and is therefore considered importan ...

Stratigraphy

The Mesón Group comprises three formations: Chahualmayoc Formation at the top, Lizoite Formation at the base and

Campanario Formation Campanario Formation ( es, Formación Campanario) is a Miocene geological formation in the high Andes of Central Chile and northern Neuquén Province Neuquén () is a province of Argentina, located in the west of the country, at the northern en ...

in-between. The group is composed of

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, siltstones and

limestone Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms whe ...

s.Grupo Meson Quartzite Fm., Sapagua (Humamuaco), Argentina
at Fossilworks.org

Fossil content

The group has provided fossils of: ;Trilobites * '' Asaphellus sp.'' * '' Notopeltis sp.'' ;Other * '' Macrocystella sp.''

References

* F. G. Acenolaza. 1986. El genero ''Macrocystella'' (Cystoidea) en el Tremadociano de Salta y Jujuy. Actas del IV congreso Argentino de paleontologia y bioestratigrafia - Simposio: Bioestratigrafia del Paleozoico Inferior. Ed. A. Cuerda. 1:133-137 {{DEFAULTSORT:Meson Group Geologic groups of South America Geologic formations of Argentina Geologic formations of Bolivia Ordovician System of South America Cambrian System of South America Ordovician Argentina Ordovician Bolivia Cambrian Argentina Cambrian Bolivia Tremadocian Sandstone formations Shale formations Limestone formations Shallow marine deposits Cambrian southern paleotemperate deposits Ordovician southern paleotemperate deposits Fossiliferous stratigraphic units of South America Paleontology in Argentina Paleontology in Bolivia Geology of Jujuy Province Geology of Salta Province Geology of Tucumán Province Formations

Stratigraphy

Fossil content

References

Further reading