The Role of the Evaporite in the Peruvian Foreland Structural Style (North Ucayali)

In the North Ucayali basin, HC reserves have been already found but the structural style is rather complex due to the variability of the sedimentary covers and the presence of inherited structures. The risk of undercharge of the prospects due to a timing problem exists. A calibration of the erosion at the top of the various structures published by Bertolotti and Moretti (2009) indicated that the tertiary structures have different ages. Although the importance of the Paleozoic depot centres and faults in localizing has been largely published, a major role of the early Mesozoic evaporitic pillows was only recently proposed although seismic data evidences these pillows that influence the thrust geometry. Such behaviour of the evaporites is similar with the one observed in other compressive fronts. However, in the classical example of compressive front above salt layer, the evaporite forms either the main decollement level (as in the Zagros). In the north Ucayali basin, the salt pillows are isolated rather flat bodies, there are also deeper decollement levels. We have designed analogue models to discuss the influence of the depth and continuity of the salt pillows on the structure style.