Influence of tectonics and neotectonics on the morphogenesis of the peak karst of Halong Bay, Vietnam

In northeast Vietnam, the karst of Halong Bay is characterized by very active neotectonics. The directional distribution of fracturing of the calcareous rocks is characterized by the influence of two major fault zones: the Red River fault zone (N140) and the Tan-Lu fault zone (N050). Karst development was favoured by intense fracturing, according to these two major directions, and reactived during recent tectonics by a compressional regime with sigma 1 N070, followed by an extensional regimes with ol near to EW that led to significant vertical movement. These tectonics, coupled with intense erasion, led to genesis and evolution of the spectacular morphology of this peak karst. (C) Elsevier, Paris.