| Popis: |
The discovery of siliceous speleothems in an outcrop of the Cerro Colorado Breccia (Sierras Australes, Buenos Aires province, Argentina) is reported in this work. The studies included morphological analysis by binocular loupe, mineralogy through X-ray diffraction and microbiological content by optical microscopy. The identified microforms were coralloid, popcorn and concentric stalactites-stalagmites (some with whiskers of gypsum), conical and cylindrical stalactites-stalagmites, microgours and flowstones. The predominant genesis was mainly associated with evaporation of water and capillarity, to a lesser extent to drip from fractures and laminar flows. The opal-A was identified through X-ray as well as the presence of quartz, plagioclase, hematite and muscovite. The significant amount of microorganisms (fungi, algae, diatoms, sporomorphs, charcoal and phytoliths) in the speleothems allowed to highlight the importance of biological phase in the development and evolution of these microforms. The reduced thickness, porous texture and pollen associations no older than the Last Maximum Glacial allowed us to infer that the studied speleothems are relatively recent. |
