Abstract

Jurassic turbidite strata in the Neuquén basin of Argentina illustrate some important points regarding the application of sequence stratigraphy in tectonically active basins. The Neuquén basin occupied a backarc setting during the Jurassic and had a complex topography generated by extensional fault structures. Two second-order sequences formed in response to relative changes of sea level during the Early to Middle Jurassic. A sequence boundary generated by tectonic inversion and basin desiccation temporally separates the two second-order sequences. Turbiditic strata within the sequences show different depositional styles, spatial distributions, and sediment supply patterns, suggesting that development of the sequence boundary represented a significant basin reorganization event. In the first sequence, during Pliensbachian time, the location and style of turbidite deposition were controlled by basin-floor topography related to extensional fault systems. Sediment transport was primarily fault parallel along graben systems. From the Aalenian to early Callovian fault relief was less significant, and clastic systems prograded northward. By contrast, in the second sequence, upper Callovian and Oxfordian turbiditic strata are restricted to a relatively small area within the northern part of the study area, and there was significant east-west sediment transport. Although Jurassic turbiditic strata in the Neuquén basin have been interpreted in a sequence stratigraphic context as third-order and higher lowstand deposits, we believe there is insufficient evidence to justify any interpretation of timing with respect to relative changes of sea level.

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