La-Amarga-Formation

The La Amarga Formation is a lithostratigraphic formation, which is digested in Argentina. It is continental sedimentary rocks that can be dated to the Early Cretaceous ( Barremian to Lower Aptian ). The La Amarga Formation belongs to the Neuquén Basin and is the oldest continental formation of this sedimentary basin. It is particularly famous for its fossils wealth, which includes among others the remains of dinosaurs with.

Location

This formation was developed by Roll ( 1939) first described and named by Musacchio (1970). Type locality is Wadi La Amarga and the nearby northern slope of the China Muerta hill, about 70 km south of the Argentine province of Neuquen in Zapala. The La Amarga Formation is part of the Neuquén Basin and is underlain by the marine Agrio Formation and overlain by the continental Lohan Cura Formation. From both formations being separated unconformably ( by Sedimentationslücken ).

Construction

This formation reaches a thickness of about 159 meters. It is divided into three Subformationen ( eng. Member): the Puesto - Antigual member is located at the base with a thickness of approximately 29 meters. This Subformation consists of fluvial sandstones deposited a Zopfstromsystems. The mean Subformation forms of Bañados -de- Caichigüe Members with a thickness of about 21 meters, which consists of white to yellowish limestone is, alternating with black shales and greenish siltstones. The limestones were deposited lacustrine here ( in a lake ). The Piedra Parada members, the top Subformation decreases with a thickness of about 109 meters, more than two -thirds of the sequence and consists of light brown to reddish, fine to medium grained sandstones, which alternate with reddish and brown to greenish siltstones. The sediments of this Subformation were deposited by a river system, as well as for advice on how to waterlogging and soil formation ( paleosols ).

Fossils

The La Amarga Formation is particularly due to its wealth of fossil vertebrates of scientific importance. These fossils are mainly from the lower Subformation, the Puesto - Antigual members, and include the remains of sauropod, theropod dinosaurs and thyreophoren, crocodile relatives and mammals with a. Sauropods were represented with the Dicraeosauriden Amargasaurus, the original Diplodocoidea Zapalasaurus and the Titanosaurier Amargatitanis. More remains were representatives of the original Titanosauriformes and Rebbachisauriden be attributed. Thyreophore dinosaurs are represented by the fragmentary remains of a stegosaur - the so far only known from South America, Stegosaurus. Theropod dinosaurs are represented by the Abelisaurier Ligabueino; Also teeth have been found that can be attributed to a large Tetanuren. Crocodile Related occurred with the Mesoeucrocodylia Amargasuchus. Mammals are represented neuquenianus with the Cladotheria Vincelestes - here it is so far the only described from the Lower Cretaceous of South America mammal.