**Integrated Stratigraphy of the Cenozoic Andean Foreland Basin (Northern Argentina) Foreland Basin (Northern Argentina)**

**Integrated Stratigraphy of the Cenozoic Andean** 

DOI: 10.5772/intechopen.69985

Claudia Inés Galli, Ricardo Narciso Alonso and Lidia Beatriz Coira and Lidia Beatriz Coira Additional information is available at the end of the chapter

Claudia Inés Galli, Ricardo Narciso Alonso

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/intechopen.69985

#### **Abstract**

The stratigraphic and sedimentologic characteristics of Cenozoic deposits in north‐west‐ ern Argentina represent important tectono‐sedimentary constraints on the evolution of the Andean foreland basin in this region. This nonmarine unit unconformably rests on the top of the postrift deposits of the middle Eocene Lumbrera Formation (Santa Bárbara Subgroup, Salta Group) or on older deposits. Eocene‐Pliocene paleoenvironmental changes were the direct result of changes in the tectonic setting and accommodation space. This study describes the results of an integrated analysis of the middle‐upper Eocene to Plio‐ Pleistocene deposits filling the basins of the Cordillera Oriental. Fluvial deposits associ‐ ated with different topographic slopes characterize the basins that formed in the Central Andes of north‐western Argentina due to Cenozoic tectonic convergence. The forma‐ tion of these basins led to the development of continental sedimentary environments, including an ephemeral fluvial system with aeolian dune fields; a sandy braided fluvial system; a playa lake; a sinuous gravelly sandy fluvial system with lagoons; and lagoons and marshes. These basins, which were probably connected during the first stage of their development, are characterized by different subsidence histories, sedimentary paleoen‐ vironmental evolution patterns, topographic slopes, provenances, and paleocurrent directions, resulting in different tectono‐sedimentary histories.

**Keywords:** Andean foreland basin, Payogastilla Group, Orán Group, provenance, stratigraphy, sequence stratigraphic, magnetostratigraphy

## **1. Introduction**

The two‐dimensional elastic model of the evolution of foreland basins, which proposes that the thrust load and the sedimentary load produce a wide deflection in the lithosphere [1, 2],

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2017 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

**Figure 1.** Satellite image of regional location of Cenozoic foreland basin.

has been widely applied to foreland basins [3–9]. These models show that the tectonic activity and the evolution of the fold and thrust belt are the drivers of subsidence in the associated foreland basins [10]. Sediment redistribution, autocyclic sedimentary processes, and eustatic baseline changes are important factors affecting the basin characteristics [2].

The main elements of "foreland basin systems" result from the accommodation created by the bending of the crust in response to the topographic load of the fold and thrust belt. This widely applied model includes four depozones: wedge‐top, foredeep, forebulge, and back bulge [6].

Another model in the northern Argentina, the "broken foreland basin," describes basins that form in retroarc zones that are largely influenced by basement structures. In these basins, the accommodation develops mainly along reactivated and inverted structures, thereby giving rise to relatively restricted basins with variable and laterally limited connections [10].

The clastic deposits of the Middle Eocene‐Pliocene are excellent examples of the Cenozoic foreland basin, which is associated with Andean orogeny [11, 12] that evolved into intermon‐ tane basins (**Figures 1** and **2**). In north‐western Argentina, the Cenozoic sediments reflect the passage of a "rift" basin during the Eocene. These deposits are associated with the Salta Group and the Andean foreland basin, which comprises extensive basins in which the Payogastilla

**Figure 2.** Stratigraphic chart of the units from Calchaquí basin and Orán basin.

**Figure 1.** Satellite image of regional location of Cenozoic foreland basin.

130 Seismic and Sequence Stratigraphy and Integrated Stratigraphy - New Insights and Contributions

bulge [6].

has been widely applied to foreland basins [3–9]. These models show that the tectonic activity and the evolution of the fold and thrust belt are the drivers of subsidence in the associated foreland basins [10]. Sediment redistribution, autocyclic sedimentary processes, and eustatic baseline changes are important factors affecting the basin characteristics [2]. The main elements of "foreland basin systems" result from the accommodation created by the bending of the crust in response to the topographic load of the fold and thrust belt. This widely applied model includes four depozones: wedge‐top, foredeep, forebulge, and back Group (Valle Calchaquí) and the Orán Group (Lerma Valley, Sianca Valley, Santa Bárbara System, and Sierra de Zapla) accumulated (**Figures 1** and **2**).

The structural evolution of the Andean foreland basin was mainly controlled by the inver‐ sion of the extensional basins of the Cretaceous rift of the Salta Group, which overlaps with the general migration of the deformation toward the foreland. Some authors describe this as "broken foreland basin," a view with widespread consensus today [13, 14], while others refer to it as a "foreland basin system" [6, 7].

The Cenozoic Andean foreland basin provides an excellent opportunity to define the rela‐ tionships between tectonism and sedimentation because its geologic history is closely linked to the tectonic activity over the evolution of the river system in the basin. In this study, the paleoenvironmental characteristics, the types of contacts between units, the provenance of the deposits, and the geochronologic and paleomagnetic ages of the stratigraphic units in each basin are presented. The integration of these data has improved our understanding of the basin evolution during the Andean orogeny.
