Abstract
A new shallow multichannel seismic survey was carried out in the Llancanelo Lake region (Southern Mendoza Province, Argentina), in order to complete and extend previously surveyed seismic sections. The new seismic data allowed to double the already existing data. The obtained information was correlated with seismic and stratigraphic data from the industry. In this way it was possible to depict the major Neogene-Quaternary sedimentary-volcanic sequences and the regional evolution of a tectonic-volcanic basin located in a key region at the eastern foot of the Andes cordillera. This research is settled on early studies that comprised seismic works reaching depths of 600-700 m as well as geoelectric and electromagnetic surveys reaching the uppermost 80-100 m of the sequences. The obtained results indicate the presence of three major sedimentary units separated by conspicuous seismic horizons SR1, SR2 and SR3, respectively considered as representing the late Mesozoic transition from marine to continental deposition, the beginning of the Cenozoic basaltic volcanism, and the change from dominantly sedimentary to dominantly volcanic processes at the base of the Quaternary. The resulting stratigraphic scheme reveals increasing volcanic (basaltic layers) intercalations with depth that accommodate to the geometry of the depocenter.
Highlights
The area of Llancanelo lake, southeast of Malargüe city, at the eastern foot of the Andes in the Province of Mendoza, central-western Argentina (Fig. 1a) is located in the southern tip of an intermountain sedimentary basin of tectonic origin (Tunuyán half graben) and in the northern part of a very extensive back-arc volcanic field (Payenia)
The obtained results indicate the presence of three major sedimentary units separated by conspicuous seismic horizons SR1, SR2 and SR3, respectively considered as representing the late Mesozoic transition from marine to continental deposition, the beginning of the Cenozoic basaltic volcanism, and the change from dominantly sedimentary to dominantly volcanic processes at the base of the Quaternary
The obtained scheme was correlated with deep seismic obtained from the industry, and the whole stratigraphic picture was interpreted on the basis of the well know regional stratigraphy
Summary
The area of Llancanelo lake, southeast of Malargüe city, at the eastern foot of the Andes in the Province of Mendoza, central-western Argentina (Fig. 1a) is located in the southern tip of an intermountain sedimentary basin of tectonic origin (Tunuyán half graben) and in the northern part of a very extensive back-arc volcanic field (Payenia). The area represents a key location at the boundary between the three major geological provinces in the region, Main Cordillera, Payenia and Neuquén Basin, in a place very close to the north-western limit of Patagonia This geotectonic framework conditioned the regional geological history and the evolution of Llancanelo lake, which responded to a complex interaction among endogen (tectonism, volcanism) and exogenous (climate, sedimentary processes) factors. In the last decade the research team which the authors of the present contribution belong to, conducted shallow and low- to middlepenetration geoelectric and shallow seismic studies These studies, supported by surface and subsurface geological samplings (short hand-drillings) were applied for the first time in the study area with the objective of defining the Neogene-Quaternary succession of sedimentary and volcanic rock sequences and depicting the geological factors involved in the recent evolution of the region (Violante et al, 2010; De la Vega et al, 2012; Osella et al, 2015). The correlation of our seismic data with the deep geological and geophysical information obtained by the industry, allowed a much better understanding of the regional geological evolution, and to fit the seismic-stratigraphic units into a chronostratigraphic scheme using the formal stratigraphic nomenclature known for the region as defined by Nullo et al (2005)
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