metamorphic rock, with granoblastic texture (minerals are in grains), with more than 75% quartz, resulting from the metamorphism of a sedimentary rock, as for example a quartzic sandstone. The original sedimentary structures of the sandstone are erased by the metamorphism.

Quaternary (2.5 Ma-Present)

last Period of the Cenozoic Era that includes the Pleistocene and Holocene Epochs. Its precise definition is still under discussion. It corresponds to an interval in the history of the Earth marked by repeated glaciations as well as by the evolution of Modern man. Landscapes, as we know today, were modelled during this period. Due to great climatic changes, namely glaciations, fauna and flora modified and great marine and terrestrial extinctions occurred, as the case of mammoths, mastodons, sabre-tooth tigers, among others (Upper Pleistocene).

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