The Açu Formation is an

Early Cretaceous The Early Cretaceous (geochronology, geochronological name) or the Lower Cretaceous (chronostratigraphy, chronostratigraphic name) is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 143.1 ...

(

Albian The Albian is both an age (geology), age of the geologic timescale and a stage (stratigraphy), stage in the stratigraphic column. It is the youngest or uppermost subdivision of the Early Cretaceous, Early/Lower Cretaceous epoch (geology), Epoch/s ...

) geologic

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 Potiguar Basin in

Ceará Ceará (, ) is one of the 26 states of Brazil, located in the Northeast Region, Brazil, northeastern part of the country, on the Atlantic Ocean, Atlantic coast. It is the List of Brazilian states by population, eighth-largest Brazilian State by ...

, northeastern

Brazil Brazil, officially the Federative Republic of Brazil, is the largest country in South America. It is the world's List of countries and dependencies by area, fifth-largest country by area and the List of countries and dependencies by population ...

. The formation comprises coarse-grained

sandstone Sandstone is a Clastic rock#Sedimentary clastic rocks, clastic sedimentary rock composed mainly of grain size, sand-sized (0.0625 to 2 mm) silicate mineral, silicate grains, Cementation (geology), cemented together by another mineral. Sand ...

s deposited in a fluvio-

deltaic A river delta is a landform, archetypically triangular, created by the deposition of the sediments that are carried by the waters of a river, where the river merges with a body of slow-moving water or with a body of stagnant water. The creati ...

environment. The Açu Formation, belonging to the Apodi Group, has provided fossils of an indeterminate

rebbachisaurid Rebbachisauridae is a Family (biology), family of sauropod dinosaurs known from fragmentary fossil remains from the Cretaceous of South America, Africa, North America, Europe and possibly Central Asia. Taxonomy In 1990 sauropod specialist Jack M ...

Description

The Açu Formation was deposited in a

passive margin A passive margin is the transition between Lithosphere#Oceanic lithosphere, oceanic and Lithosphere#Continental lithosphere, continental lithosphere that is not an active plate continental margin, margin. A passive margin forms by sedimentatio ...

setting, overlying the Alagamar Formation and is overlain by the Jandaíra Formation. In the petroleum producing Potiguar Basin, the formation is a

reservoir rock A petroleum reservoir or oil and gas reservoir is a subsurface accumulation of hydrocarbons contained in porous or fractured rock formations. Such reservoirs form when kerogen (ancient plant matter) is created in surrounding rock by the presenc ...

.Maraschin et al., 2010, p.87

Fossil content

The following fossils were reported from the formation:Açu Formation
at

Fossilworks Fossilworks was 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 cr ...

.org

Dinosaurs

Sauropods

Theropods

Crocodylomorphs

Fish

Crustaceans

Molluscs

Bivalves

Gastropods

Echinoderms

Plants

Bibliography

* *

References

{{DEFAULTSORT:Acu Formation Geologic formations of Brazil Lower Cretaceous Series of South America Cretaceous Brazil Albian Stage Sandstone formations Deltaic deposits Fluvial deposits Reservoir rock formations Paleontology in Brazil Environment of Ceará Landforms of Ceará Northeast Region, Brazil