The relationship between carbonate facies, volcanic rocks and plant remains in a late Palaeozoic lacustrine system (San Ignacio Fm, Frontal Cordillera, San Juan province, Argentina)

BUSQUET, P.; MÉNDEZ-BEDIA, I.; GALLASTEGUI, G; COLOMBO, F.; CARDÓ, R.; LIMARINO, C.O.; HEREDIA, N.; CÉSARI, S.N.

INTERNATIONAL JOURNAL OF EARTH SCIENCES

SPRINGER

Lugar: Berlin; Año: 2013 vol. 102 p. 1271 - 1287

1437-3254

Abstract The San Ignacio Fm, a late Palaeozoic forelandbasin succession that crops out in the Frontal Cordillera(Argentinean Andes), contains lacustrine microbial carbonatesand volcanic rocks. Modification by extensivepedogenic processes contributed to the massive aspect ofthe calcareous beds. Most of the volcanic deposits in theSan Ignacio Fm consist of pyroclastic rocks and resedimentedvolcaniclastic deposits. Less frequent lava flowsproduced during effusive eruptions led to the generation oftabular layers of fine-grained, greenish or grey andesites,trachytes and dacites. Pyroclastic flow deposits correspondmainly to welded ignimbrites made up of former glassypyroclasts devitrified to microcrystalline groundmass,scarce crystals of euhedral plagioclase, quartz andK-feldspar, opaque minerals, aggregates of fine-grainedphyllosilicates and fiammes defining a bedding-parallelfoliation generated by welding or diagenetic compaction.