Gondwana Paleolandscapes: Long-Term Landscape Evolution, Genesis, Distribution and Age

• Main Author: Rabassa, Jorge Oscar
• Format: Article in Journal/Newspaper
• Language: English
• Published: Univ Estadual Paulista-unesp
• Subjects: Gondwana; Paleosuperficies; Mesozoico; Areas Cratónicas; https://purl.org/becyt/ford/1.5; https://purl.org/becyt/ford/1; Antarctic; The Antarctic; Antarc*; Antarctica; Ice Sheet
• Online Access: http://hdl.handle.net/11336/12738

The concept of “Gondwana Landscape” was defined by Fairbridge (1968) as an “ancestral landscape” composed of “series of once-planed remnants” that “record traces of older planation” episodes, during the “late Mesozoic (locally Jurassic or Cretaceous)”. This has been called the “Gondwana cyclic land surface” in the continents of the southern hemisphere, occurring extensively in Australia, Southern Africa and the cratonic areas of South America. Remnants of these surfaces are found also in India, in the northern hemisphere and it is assumed they have been preserved in Eastern Antarctica, underneath the Antarctic ice sheet which covers that region with an average thickness of 3,000 meters. These paleolandscapes were generated when the former Gondwana super-continent was still in place and similar tectonic conditions in its drifted fragments have allowed their preservation. Remnants of equivalent surfaces, though of very fragmentary condition, have been described in Europe and the United States. These Gondwana planation surfaces are characteristic of cratonic regions, which have survived in the landscape without being covered by marine sediments over extremely long periods, having been exposed to long-term sub-aerial weathering and denudation. Their genesis is related to extremely humid and warm paleoclimates of “hyper-tropical” nature, with permanently water saturated soils, or perhaps extreme paleo-monsoonal climates, with seasonal and long term cyclic fluctuations, from extremely wet to extremely dry. Deep chemical weathering is the dominant geomorphological process, with the development of extremely deep weathering profiles, perhaps of up to many hundreds of meters deep. The weathering products are clays, kaolinite, pure quartz and other silica form sands, elimination of all other minerals and duricrust formation, such as ferricretes (iron), silcretes (silica) and calcretes (calcium carbonate). Annual precipitation in these periods would have been higher than 10,000 mm, with extremely high, mean annual ...