Intrabasinal and extrabasinal turbidite deposits: origin and distinctive characteristics According to its original conception, turbidites were related to re-sedimentation processes in deep waters. Basically, sediments initially stored in littoral/shallow marine environments were periodically transferred (or re-sedimented) into the inner basin by slope instability. Since these turbidites originate within the marine basin, the resulting sediment gravity flows could be considered intrabasinal turbidites. More recently, an increasing number of evidences show that turbidites commonly originates from the direct discharge from rivers in flood. These turbidites result from relatively dense turbulent suspensions entering the sea as hyperpycnal flows. Since these turbidites originate in the continent, they are extrabasinal turbidites. The deposits of intrabasinal and extrabasinal turbidites have several diagnostic features allowing a clear differentiation. Intrabasinal turbidites are surge-like flows, and commonly initiate with a cohesive debris flow that progressively dilutes and transform into a granular and finally a turbulent flow. On the contrary, extrabasinal turbidites are fully turbulent flows driven by a relatively dense and sustained river discharge. Depending on the grain-size of suspended materials, the resulting hyperpycnal flow can be muddy or sandy. Sandy hyperpycnal flows also can carry bedload, resulting in sandy to gravel composite beds with sharp to gradual internal changes, laterally associated with lofting rhythmites and abundant plant remnants. Muddy hyperpycnal flows are loaded by a suspension of silt and clay, and accumulate silty-clay graded beds with plant remnants and displaced marine microfossils. It is interpreted that most of the shales of the Los Molles and Vaca Muerta formations in the Neuquen Basin were accumulated in this way.