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Featured article from geoscience journal

Elsevier, Amsterdam
Geomorphology, 2013, Vol 197, p. 190-196
Comment on “Sandstone caves on Venezuelan tepuis: Return to pseudokarst?” by R. Aubrecht, T. Lánczos, M. Gregor, J. Schlögl, B. Smída, P. Liscák, Ch. Brewer-Carías, L. Vlcek, Geomorphology 132 (2011), 351–365
Abstract:

In the recent work of Aubrecht et al. (2011) the presence of “unlithified or poorly-lithified beds” of sands in the quartz-sandstone stratigraphic succession is proposed as a key factor for speleogenesis in the Venezuelan tepuis.In this comment we observe that in the cited work the geologic history of the region, in terms of sedimentation environment, diagenesis and low grade burial metamorphism, has not been considered. Furthermore, the peculiar “pillar flow” columns that Aubrecht et al. describe as a proof of the unlithification are lacking in many other different cave systems in the same area.

Four critical points are discussed: the burial metamorphism of the Mataui Formation, the significance of the Schmidt Hammer measurements, the cave morphologies and the role of SiO2 dissolution. Finally we suggest that weathering, in its wider significance, is probably the triggering process in speleogenesis, and there is no need to invoke a differential diagenesis of the sandstone beds. ©