Parángula Formation

Parángula Formation
Stratigraphic range: Oligocene–Miocene PreꞒ Ꞓ O S D C P T J K Pg N
Holotype of Barinasuchus arveloi, recovered from the Parángula Formation
Type	Geological formation
Underlies	Río Yuca Formation
Overlies	El Mene Formation
Thickness	550–1,600 m[1]
Lithology
Primary	Sandstone
Other	Shales, claystones
Location
Approximate paleocoordinates	9°18′N 66°06′W / 9.3°N 66.1°W / 9.3; -66.1
Region	Barina, Portuguesa
Country	Venezuela
Type section
Named for	Quebrada Parángula
Named by	Mackenzie, 1937
Parángula Formation (Venezuela)

The Parángula Formation is a lithostratigraphic unit in the states of Barinas and Portuguesa^[2] in Venezuela. It was deposited from the Oligocene to the Miocene.^[3][1]

The Parángula Formation was first published about by A. N. Mackenzie in 1937, who used the name in reference to a series of sandstones, conglomerates, and mottled clays from the Parángula ravine.^[4] In 1946, a further description of the formation's geology was published by R. A. Liddle.^[5] In 1960, a thorough description of the stratigraphy of the Parángula Formation was published by G. R. Pierce. Pierce attempted to emend the name of the formation, renaming it to the Parángulo Formation,^[6] though this was unsuccessful.^[1]

The lowermost layers of the Parángula Formation, those overlying the "El Mene" Formation, were deposited in the Oligocene epoch,^[1] whereas the uppermost layers, those underlying the Río Yuca Formation, were deposited in the Miocene.^[1][2] The surface layers of the Parángula Formation consist predominantly of coarse lenticular conglomerates, fine-grained sandstones deposited in massive layers, limonites, and mudstones, which may be red, reddish-brown, brown, or purple in colour. The layer immediately below the surface is similar but lacks conglomerates. Below that is a layer of basal sandstone, with certain elements, such as the presence of small amounts of glauconite, which suggest influence from marine sediments. Upper layers show a gradual increase in sand deposition, a likely result of debris accumulated from the uplifting of the Andes.^[1]

The uppermost strata of the Parángula Formation were likely deposited in a brackish environment.^[1] Certain portions of the upper Parángula Formation, such as the Tucupido River site^[2] (sometimes interpreted as part of the overlying Río Yuca Formation^[1]) show signs of fluvial (river) deposition.^[2] The Lexico Estratigrafico de Venezuela suggests that the depositional environment of the upper Parángula Formation was partly marine and may have sported mangrove swamps.^[1]

The Parángula Formation preserves a number of microfossils, many suggested to have been reworked from middle Eocene strata.^[1] Fragmentary remains from small mammals, turtles, and caimans have been reported from the upper strata.^[1][2] Two named taxa from different localities are found in the Parángula Formation, both from the upper Miocene.^[2] One is a ground sloth, Pseudoprepotherium venezualanum, recovered on the banks of the Tucupido River in Portuguesa;^[1][2] the other is a species of very large sebecid crocodyliform, Barinasuchus arveloi,^[2] whose type specimen was recovered near a tributary of the Rio Masporro River during the construction of a road, and which was largely destroyed in the process.^[7]