The Trans-Argentine Corridor (central Argentina): an upper Cretaceous intracontinental rifting associated to the Gondwana break-up.

ROSSELLO, E. ; LÓPEZ DE LUCHI, M. G.

Mendoza

Simposio; Gondwana 12 Geological and biological heritage of Gondwana; 2005

Academia Nacional de Ciencias

The Cretaceous Trans-Argentine corridor is recognised in the central part of western Argentina by the alignment of deep and narrow N-S trending Late Cretaceous continental rifts (Macachín, General Levalle, Gigante, Pagancillo, Campo del Arenal, Salinas, depocenters). In some places are associated with coeval within-plate alkaline volcanism. Basins are typically steeply dipping hemi-grabens with characteristic rift-like sedimentary sequences, which are controlled by strongly uplifted Proterozoic or Pre-Carboniferous peneplanized basement blocks that crop out at the Sierras Pampeanas. Towards the northern extreme, the corridor is represented by the southernmost branch of the three ones that made up the Cretaceous Salta basin rift (which evolved from a triple point and shows Pacific connections through Perú,Bolivia Towards the south this belt evidences links, albeit segmented by the Alto Interserrano, with both the Colorado basin (via the Macachín basin) and the Salado< basin (via the Junín basin), located on the Atlantic border of the South America. Alkaline volcanism is developed from the Salta basin to the south of the Sierras Pampeanas Orientales (Eastern Pampean Ranges). These rocks are either interlayered in the intracratonic basins or exposed as isolated small volcanic cones with bear no relation with Cretaceous sediments. From north to south some examples of this volcanic activity are found at Quebrada Las Conchas (Salta), Río Belen (Catamarca), Los Condores hill at Sierras de Córdoba and in southern Sierras de Córdoba and San Luis. At the Salta basin, the Las Conchas alkaline magmatism is represented by basanites whereas at Río Belén, Catamarca, the (131.0 ± 4.0 Ma). La Puerta de San José basalt is interlayered in a continental pile and constituted an isolated expression of within-plate alkaline magmatism that could either indicate a new Cretaceous depocenter or belong to an 200 km inferred extension of the present southern border of the Salta Basin. In the Sierras Pampeanas Orientales at Córdoba, Los Condores rocks are basanites to basaltic trachyandesites. The Late Cretaceous-Early Tertiary strongly alkaline volcanism (nefelinites, mellilitites and minor leucitites) that appears as isolated hills at the south of the Sierras Pampeanas of San Luis and Córdoba (La Garrapata, La Madera and Chaján hills) and as very restricted outcrops in the basement of the Sierra de San Luis, indicate low degree of partial melting of a deep mantellic sources, the ascent of those melts have been adscribed to processes related with the Atlantic ocean aperture . The intracratonic location of the corridor suggest a strong control by regional crustal weakness zones which could have allowed the ascent of mantellic-source melts like those that are represented by the basic alkaline magmas.The Trans-Argentine Corridor was near to divide the South American plate into two subordinate plates: the Western and Eastern.All the depocenters depict more or less aligned troughs that integrate an almost continuous intracratonic submeridional rifting that cut through the entire Argentina (from the Atlantic border of the Buenos Aires province to the Puna).This deep depocenter belt is related in both time and space with the Atlantic aperture because it could be considered as the result of a Late Cretaceous aborted intracontinental extension. Some subsurface surveys of the structures and the external architecture of the horizontal and vertical sections of the infillings indicate transcurrent features. The Andean reactivation of older discontinuities affected the entire in the case under study, the listric normal faultings, specially those that controlled the western flank of the depocenters were inverted. The intensity of these inversions in the basement blocks of the Andean foreland increases towards the west.