Petrology and Provenance of the Toro Negro Formation (Neogene) of the Vinchina Broken Foreland Basin (central Andes of Argentina)

CICCIOLI. P; MARENSSI, S.A; LIMARINO, C

JOURNAL OF SOUTH AMERICAN EARTH SCIENCES

PERGAMON-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 2014 vol. 49 p. 15 - 38

0895-9811

Detrital modes of sandstones and conglomerates of the Toro Negro Formation (Late Miocene-earlyPliocene) were used to analyze the evolution of the broken-foreland stage of the Vinchina Basin(28300e29000 S and 68300e68200 W) of NW Argentina. This basin located in the Western SierrasPampeanas is bounded to the west by the Precordillera and to the east by the Famatina System. Threesandstone petrofacies: plutonic-metamorphic, volcanic and mixed petrofacies and three conglomeratelithic associations: basement, sedimentary and volcanic lithic associations were recognized, allowing toestablish three source areas: Western Sierras Pampeanas (Toro Negro and Umango Ranges), CordilleraFrontal and Precordillera.During the Late Miocene, the Toro Negro Range (to the north) together with the Cordillera Frontal andPrecordillera (to the west) were the main sources for depositional sequences I and II (lower member ofthe Toro Negro Formation). On the contrary, during the latest Miocene-early Pliocene, DepositionalSequence III (upper member) exhibited a progressive increase in the supply from the eastern Precordillera(to the west) with additional material from the Umango Range to the south. Besides, evidenceof synchronic volcanism is recorded in the upper part of Depositional Sequence II and the lower part of Depositional Sequence III.The coexistence of the three source areas and the changing distribution patterns due to reaccommodationof sediment dispersal routes demonstrate that the evolution of this type of basin ismuch more complex than previously envisaged. Therefore, an integrated analysis using different tools(sedimentary facies, paleocurrent measurements, sandstone petrography and conglomerate composition)is needed for a clearer understanding of broken-foreland basins.