Basement highs and their influence on basin geometry and sediment distribution in the Chacopampean Plain, Argentina

Abstract

The Chacopampean Plain of the Andean foreland of northern Argentina hosts an important sedimentary record that spans from the Paleozoic era to the present day. This study focuses on the analysis of the structural and sedimentary evolution of three distinct phases of basin history: i) the development of the Paleozoic intracratonic Chacoparanaense Basin; ii) the formation of the Cretaceous Salta Rift Basin; and iii) the Cenozoic formation of the Andean Foreland Basin. A comprehensive analysis of 3655 km of recently released industry seismic-reflection lines and stratigraphic information retrieved from 18 exploratory wells was conducted, enabling an unprecedented view of the complex tectonic and depositional history of the Chacoparanaense Basin. This history is closely associated with variable geodynamic boundary conditions that influenced this region until today. The Paleozoic and Mesozoic stages of basin evolution were finally superseded by deposition of an eastward-thinning sediment wedge of Andean Foreland Basin strata related to Cenozoic Andean mountain building, which began during the Paleogene.The application of three-dimensional reconstruction techniques to the analysis of basin configurations through time has elucidated the significance of two prominent morphological structures in the subsurface, the Quirquincho and Pampeano-Chaque˜no highs. These topographic highs exerted a long-lasting influence on sediment dispersal and deposition. Both basement highs were subsequently uplifted and partially eroded during the late Paleozoic and early Mesozoic, but progressively buried by sediments. The two elevated regions are interpreted as part of a Paleozoic forebulge that was formed by long-wavelength flexural uplift during the Gondwanan orogeny.The modification of these structures and the overlying sedimentary cover occurred during Cretaceous regional extension, a regional tectono-magmatic event that led to the formation of the Salta Rift Basin. The fact that Cenozoic foreland-basin deposits cover the paleo-topography of the Quirquincho and Pampeano-Chaque˜no highs without notable interruption clearly shows that these sectors of the present-day foreland remained tectonically dormant during Cenozoic Andean shortening. This contrasts with adjacent areas of the foreland farther west thatrecord structural overprinting during contractional inversion of Cretaceous extensional structures. The presented results highlight the intricate and non-linear impact of crustal memory on the evolution of foreland basins.