Abstract

MURUAGA, Claudia M. Stratigraphy and tectosedimentary development of the Tertiary sediments in the Sierra de Hualfín area, southeastern margin of the Puna, Catamarca, Argentina. Rev. Asoc. Argent. Sedimentol. [online]. 2001, vol.8, n.1, pp.27-50. ISSN 1853-6360.

Tertiary sediments, outcropping around the Hualfín-Las Cuevas Range, Catamarca Province, Argentina (Fig. 1) reveal 3,000 m of alluvial continental clastic sediments. Previous work includes many studies of this area, mainly motivated by the exceptional mammalian fauna the sediments contain (Stahlecker, 1926 en Riggs y Patterson, 1939; Cabrera, 1937, 1944; Pascual y Odreman Rivas, 1971; Marshall et al., 1979; Marshall y Patterson, 1981; Butler et al., 1984; Allmendinger, 1986; Bossi et al., 1987, 1993, 1994; Flynn y Swisher, 1995; Gavriloff et al., 1998; Powell et al., 1998; Esteban y Nasif, 1999; Esteban et al., 1999). Detailed sedimentary facies analysis, provenance and compositional studies in sandstones and conglomerates, petrology and shale mineralogy and paleontologic studies were made in the sedimentary succession (Muruaga, 1998). The lithostratigraphic scheme and its correlation with other units defined for adjacent areas are shown in figure 2. In the study area, the Hualfín Formation is defined as the basal unit (Lower Cretaceous) of the tertiary sediments. The overlying formations belong to the Santa Maria Group (Middle Miocene to Pliocene), having a stratotype at the Santa Maria Valley (Bossi y Palma, 1982), including the Las Arcas, Chiquimil, Andalhuala and Corral Quemado Formations. The Chiquimil Formation is divided into three members in the Puerta de Corral Quemado-Villavil area, now formally named the Los Baños (lower), El Áspero (middle) and El Jarillal (upper) Members. Two sedimentation settings have been distinguished (Muruaga, 1998). The first, 3,500 m thick, dominated by braided river fluvial plain (Rio Villavil section, Fig. 3 and 4) and the other of 2,300 m thick, by alluvial fans and close to the basin border (El Durazno section, Fig. 5). The paleocurrents and provenance data (Table 3) indicate that the Puna block and Altohuasi-Culampajá and Papachacra Ranges were the source areas of the Neogene sediments in the Hualfín Basin. The sedimentary filling and tectonic characteristics allow the definition of an intracratonic basin (Klein, 1996), with the formation of asymmetric half-grabens on both sides of a lithospheric arch. Two tectonic stages were defined in the basin (Muruaga, 1998; Bossi et al., 1999, 2000; Muruaga y Bossi, 1999), an extensional stage and an inversion stage. During the extension phase, the accommodation space was produced by high-angle normal faulting. The Farallón Negro Complex (with a maximum date of 12 ± 2Ma, Linares y González, 1990) is part of the initial magmatism associated with rifting. Subsequently during the inversion stage, the deformation became clearly compressive after 3.5 Ma and the initial configuration of the basin was modified. Inversion of some preexistent fault planes and high-angle inverted faults were created at the borders of the basin, along which basement blocks thrust up onto the sedimentary succession. The evolution of the basin includes five stages. Stage 1 is represented by Hualfín Formation sheetflood regime sedimentation, strongly controlled by normal faulting (Fig. 9a). Stage 2, sediments include Las Arcas Formation and the three members of the Chiquimil Formation and correlate to the stage of maximum tectonic subsidence. The sedimentation is axial with well-developed channels and sporadic high flood conditions. The El Áspero Member is characterized by a dominant volcaniclastic sedimentary supply that enters the basin coming from the NW, with andesitic extrusive bodies (9.14 ± 0.02 Ma, Sasso, 1997) (Figs. 9 b, c and d). Stage 3 involves the thermal subsidence stage and is defined by the deposition of a thicker clastic succession (Andalhuala Formation) composed of proximal braided river facies. Stage 4 consists of the abrupt change to alluvial fans sequences (3.5 Ma) of the Corral Quemado Formation, related to the basin inversion. Finally, Stage 5, represented by Punaschotter, is the result of final uplift of the surrounding ranges and is dominated by coarse conglomerate facies.

Keywords : Stratigraphy; Upper Tertiary; Santa Maria Group; Rifting; Inversion.