Cerro Bola

Cerro Bola

The Cerro Bola Anticline is located in the Province of La Rioja north-western Argentina about 30 kilometres southwest of the town of Villa Union. The N-S trending west-vergent perclinal anticline is in the hanging wall to a thrust system that dips eastward at about 24°, related to the Late Tertiary to Quaternary Pampean Range orogenic deformation. The rocks (Guandacól Formation) comprise a deglacial succession deposited in the epicratonic Paganzo Basin during the Mid to Late Carboniferous, with several cycles of alternating fluvial-deltaic sediments, mass transport deposits and turbidites. The c. 1000 m thick succession overall has a shallowing-upward character, ending with Permian red-beds.

Well exposed mass transport deposits of seismic scale (≤140m thick) are characterized by the large allochthonous sand blocks derived from underlying fluvial-deltaic sediments, and ranging up to 100’s of meters in length and tens of meters in thickness. The underlying fluvial-deltaic sediments are deformed and grooved along the basal contact of the MTD. The MTDs are overlain by turbidites that are locally ponded in the surface relief. The extensively exposed turbidites include deposits of hybrid and transitional flow types in addition to more conventional turbidites.

A time-equivalent succession is exposed in La Peña Canyon, 100 km to the south of Cerro Bola, revealing spectacular sections through a series of mass transport deposits and ponded turbidites.  We have studied these remote outcrops since 2006, but they are now accessible new via road cuts.

 

Las Lajas

Las Lajas

The mid-Carboniferous (late Mississipian to early Pennsylvanian) Jejenes Formation is superbly exposed due to Neogene thrusting within the Eastern Precordillera of the Andes in San Juan Province, western Argentina.  This deglacial succession includes several hundred metres of turbidites with varying degrees of confinement within paleofjords and broader flooded paleovalleys. Lateral continuity of the exposures is exceptional. We are currently studying the architecture of these sheet systems, and their relationship to glacio-eustatic sea level changes.