Authigenic and detrital clay minerals as indicators of paleoenvironmental and postdepositional evolution in a Cretaceous–Cenozoic succession from Argentine Central Andes

WUNDERLIN, CECILIA A.; COLLO, GILDA; EZPELETA, MIGUEL; REINOSO CARBONELL, VIRGINIA V.; NÓBILE, JULIETA C.; CICCIOLI, PATRICIA L.; FAUDONE, SONIA

SEDIMENTARY GEOLOGY

ELSEVIER SCIENCE BV

Año: 2022 vol. 437

0037-0738

New X-ray diffraction (XRD) data, scanning electron microscopy (SEM) analysis, and X-ray energy dispersive spectrometry (EDX) microanalysis on clay minerals are presented for Cretaceous–Cenozoic sedimentary sections studied in the La Flecha and La Troya Sur creeks, located in the Argentine Precordillera. The characterization of clay mineral assemblages, including the discrimination of detrital and authigenic phases, allows inferences to be made about paleoclimatic and paleoenvironmental conditions as well as the post-sedimentary history of these foreland clastic sedimentary depocenters. Mineralogical analyses carried out in the Cretaceous Ciénaga del Río Huaco Fm. and the Cenozoic Puesto La Flecha, Vallecito, Vinchina, and Zapallar Fms. show the presence of illites, smectites, illite/smectite mixed-layer clays (I/S, with R0 and R1 ordering types), sporadic corrensite, and subordinate amounts of chlorite and kaolinite, among other non-clay phases, such as analcime and heulandite. Illite and chlorite are interpreted as detrital phases, reflecting the composition of the source area, and smectite, I/S R0 and R1, and corrensite are interpreted as authigenic phases developed in the matrix or as massive pore filling within the clastic levels. Compositional analyses allow for smectites to be characterized as di- and trioctahedral Mg-rich, and are interpreted as a product of the combination of two main controls: (1) that from the parent material (volcaniclastic material and magnesian silicates) and (2) that of the primary composition of pore fluids associated with alkaline lake systems. These smectites are precursors of prograde diagenetic phases developed under a low thermal regime (