Karst and caves in the Bihor Mountains - ITIM

altitude of the discharge point changed and in order tokeep pace with the rapid downward progress of CrăiasaValley, the cave stream now begins the incision of floorin the Scientific Reserve and Passage 6, transformingthe gallery into canyons (Fig. 7d, 5 & 6).• During the Pleistocene, speleothem deposition in theupper passages was extremely active, while in theScientific Reserve several filling and reactivatingphases occurred as consequences of the outsideclimate variations. In the last interglacial, the amount ofsediments was so large that it blocked the drainage toPassage 6, thus causing in almost complete filling ofthe Scientific Reserve and redirecting the flow through"Emil Racoviţă and Bones passages. This hypothesisis sustained by the presence of massive speleothemsand clastic deposits that cover the floor of "EmilRacoviţă" Passage in its upstream sector, as well as theaccumulation of fossils in Bones Passage.• The reactivation of the drainage between the ScientificReserve and Huda de la Chişcău Cave marks thebeginning of clastic sediments removal from theScientific Reserve. The underground stream deepenedits bed in its own alluvia. It is considered that during theWürm glacial period the cave bears entered andhibernated in the cave, using Huda de la Chişcău Caveas access point.• The last stage of evolution of Urşilor Cave took place inthe Atlantic phase, characterized by a large amount ofprecipitations. The Scientific Reserve was completelyfilled with sediments in the lowermost part, and at thesame time the entrance in the Huda de la Chişcău Cavewas blocked, leading to the complete isolation of thecave until 1975.