Basement-cover interaction in the mountain front of the Northern Neuquén fold and thrust belt (37°10’ – 37°40’ S), Argentina

TURIENZO, MARTÍN; SÁNCHEZ, NATALIA; LEBINSON, FERNANDO; PERALTA, FLORENCIA; ARAUJO, VANESA; IRASTORZA, AINARA; DIMIERI, LUIS

JOURNAL OF SOUTH AMERICAN EARTH SCIENCES

PERGAMON-ELSEVIER SCIENCE LTD

Año: 2020 vol. 100

0895-9811

The deformation front of the Neuquén fold and thrust belt (~37°30′S) comprises kilometer-scale basementinvolved anticlines, related to development of the Las Yeseras and Pampa Tril thrust systems, connected with awide frontal syncline. The interpretation of more than 70 seismic lines led to the construction of a time-structure map at top of the Cuyo Group (Middle Jurassic), which shows a structural high east of the Tromen volcano produced by the superposition of thick-skinned structures. Moreover, data from 35 oil wells constrain the alongstrike variations in structural reliefs. The structural relief of the Las Yeseras anticline increase from north tosouth, between ~1000 m and 2000 m, while the structural relief of the Pampa Tril anticline reaches its maximum height of 3700 m in the north and decreases southwards to only 1600 m height and then disappears. Threestructural cross-sections based on surface and subsurface information show the overall structural style dominated by north-trending basement-involved anticlines, with subhorizontal backlimbs and maximum structural reliefs around 3-4 km, associated with thick-skinned thrust systems and without significant participation of inverted normal faults. Calculated thick-skinned shortenings are ~8.3 km (14.8%) in the north and ~4 km (7.8%) in the south, which principally reflects the decreasing displacement of the Pampa Tril thrust system. Along-strike structural changes were locally controlled by WNW transfer zones that can be interpreted as SSWdipping preexisting normal faults with minor positive inversion. Thin-skinned structures that form oil fields atdepth are genetically associated with the thick-skinned thrust systems, thus the understanding of basement-cover interaction in the mountain fronts will aid to future hydrocarbon explorations and to comprehend the mechanisms of Andean mountain building.