**2. The pre‐Andean basement**

In Cordillera Oriental, the upper Neoproterozoic La Paya Formation basement unit contains low‐grade metamorphosed sandstones and mudstones [15, 16] that grade southward into schists, gneisses, and migmatites [17, 18] in the Sierra de Quilmes and Cumbres Calchaquíes (**Figures 2** and **3**).

Marine quartzites of the Meson Group are arranged in angular unconformity on top of the previous deposits [19] (middle to upper Cambrian).

The marine deposits of the Silurian‐Devonian basin are represented by deposits of an exten‐ sive marine platform environment whose greater thicknesses are developed east of the Cordillera Oriental [20].

The sedimentary succession that overlaps the Neoproterozoic to lower Paleozoic basement corresponds to the Cretaceous‐Paleogene strata of the Salta Group [21] and the Paleogene‐ Neogene strata of the Payogastilla Group and Orán Group.

The Salta Group, in Cordillera Oriental and Santa Bárbara System, is present in three subba‐ sins: Metán, Alemanía, and Pucará‐Brealito (**Figure 3**). The Salta Group deposits are divided into the following three subgroups (from base to top): Pirgua [22], Balbuena, and Santa Bárbara [23]. The Pirgua Subgroup is composed of sandstones, conglomerates, and siltstones at almost all localities and represents the syn‐rift fill. The Balbuena Subgroup, which accumulated dur‐ ing the Maastrichtian to Early Paleocene, represents the early postrift stage and is composed of white sandstones (Lecho Formation) and gray to yellow limestones in the upper part (Yacoraite Formation). The Santa Bárbara Subgroup consists of the Mealla, Maíz Gordo, and Lumbrera formations [23] and is dominated by fine‐grained red sandstone, siltstone, and green mudstone.

The Lumbrera Formation [23], which represents the uppermost part of the Salta Group (**Figure 2**) is composed of claystones and siltstones and is always reddish‐brown to red. In the Integrated Stratigraphy of the Cenozoic Andean Foreland Basin (Northern Argentina) http://dx.doi.org/10.5772/intechopen.69985 133

**Figure 3.** Geologic map of the region in southern Salta province, northwest Argentina. Adapted from [68, 69].

Lumbrera Formation, three units have been identified based on the contrasting characteristics of the facies groups: the lower Lumbrera Member, the *Faja Verde*, and the upper Lumbrera Member [24]. The lower part is fossil‐rich [25–27] and was dated to the lower to middle Eocene based on vertebrate associations [28]. The top of the Faja Verde is an omission surface that marks the beginning of the sedimentary foreland basin for some authors [4, 29–31].

A clear paraconformity is located between the Lumbrera II Formation and the Los Colorados Formation. In parts of the foreland basin, a paraconformity between Lumbrera II Formation and Río Seco Formation corresponds to a hiatus from lower Eocene to middle Miocene.

The Orán Group [32] includes the Paleogene and Neogene deposits, which, in the Salta and Jujuy provinces and surrounding areas, overlie on the Salta Group (Cretaceous‐Eocene, **Figure 2**). During the upper Neogene, several tectonic events related to the uplift of the Andes occurred and caused variations in the basins located to the east, consequently influencing the characteristics of the sediments, which can be divided into two sequences: the lower, Metán Subgroup, and the upper, Jujuy Subgroup (**Figure 2**).
