Arroyo Truquicó, Ñorquín Department, Neuquén Province, Argentinai

Regional Level Types
Arroyo Truquicó	Creek
Ñorquín Department	Department
Neuquén Province	Province
Argentina	Country

An important Trigonias fossil concentration, belonging to the Agrio formation, Pilmatue Member, late Valanginian in the north of Neuquén, mineralized by chalcedony and opal.

Arroyo Truquicó is a classic locality where Bodenbender collected Early Cretaceous marine fossils in 1887 and 1888. These fossils were described and figured by Behrendsen (1892) including the first mention of the species ‘Trigonia’ transitoria Steinmann in the Neuquén Basin. The species was later transferred to the genus Steinmanella (Crickmay, 1930). The best outcrops are located between the Truquicó Creek and the northern flank of Cerro Pitrén, approximately 10 km southwest of the junction of the Truquicó Creek and the Neuquén River and 10 km southwest of Chos Malal.

Access is from State Road 6 off National Road 40 towards Estancia Truquicó and connecting to Route 30 for about 3 km. The Agrio Formation outcrops are widespread in this area, but only the lower part of the Pilmatué Member is well exposed, comprising approximately the lowest 180 m, and resting on the sandstones of the Mulichinco Formation. The studied beds encompass the same ammonoid subzones recorded in Cerro Caicayén. It is easy to correlate this section to Cerro Caicayén as the lithology and faunal successions are quite similar, even though the Caicayén section is thicker. A bed-by-bed section was logged and new Steinmanella material was collected. Ninety-seven specimens of Steinmanella caicayensis sp. nov. and six specimens of
S. curacoensis have been collected in this locality.

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