Curved structures and interference fold patterns associated with lateral ramps in the Eastern Cordillera, Central Andes of Argentina

摘要

The conspicuous curved structures located at the eastern front of the Eastern Cordillera between 25° and 26° south latitude is coincident with the salient recognized as the El Creston arc. Major oblique strike-slip faults associated with these strongly curved structures were interpreted as lateral ramps of an eastward displaced thrust sheet. The displacement along these oblique lateral ramps generated the local N-S stress components responsible for the complex hanging wall deformation. Accompanying each lateral ramp, there are two belts of strong oblique fault and folding: the upper Juramento River valley area and El Brete area.On both margins of the Juramento River upper valley, there is extensive map-scale evidence of complex deformation above an oblique ramp. The N-S striking folds originated during Pliocene Andean orogeny were subsequently or simultaneously folded by E-W oriented folds. The lateral ramps delimiting the thrust sheet coincident with the El Creston are salient are strike-slip faults emplaced in the abrupt transitions between thick strata forming the salient and thin strata outside of it. El Creston arc is a salient related to the pre-deformational Cretaceous rift geometry, which developed over a portion of this basin (Metan depocenter) that was initially thicker. The displacement along the northern lateral ramp is sinistral, whereas it is dextral in the southern ramp. The southern end of the Eastern Cordillera of Argentina shows a particular structure reflecting a pronounced along strike variations related to the pre-deformational sedimentary thickness of the Cretaceous basin. © 2005 Published by Elsevier B.V.