Cave Sediments from the Infilled Cave Near Divača

Abstract

South of Divača a cave previously completely filled with yellow fluvial clastic sediments was exposed on the eastern edge of the motorway in 1997. The cross-section of the cave was app. 6 m high, with a few metres of ceiling above it. In view of the knowledge available back then, it could be assumed that applying the palaeomagnetic method was the only way to undertake the dating of these sediments. The passage exhibited yellow layers of fluvial cave sediments ranging from sand and silt to loam, while a layer of red loam was present on top of the profile. Several different textures were evident in the profile which intersected the entire cave, with cross-stratification prevailing, while other erosion surfaces were also visible and divided the profile in individual sequences. All sediments in the cave underwent heavy ferritization, especially along the fissures which formed in the sediment due to their drying or shifting on account of subsidence or tectonics. Certain parts of the profile were also heavily cemented with calcite, namely in the form of randomly positioned irregular bodies. In terms of their mineral composition, the sediments found in the cave are weathered remains of the Eocene flysch as attested by the high content of quartz and the presence of feldspars. The cave was formed in the Palaeocene limestone and is of unknown age. In view of the results obtained, its formation can be linked with the period when the sea level declined drastically, and with the development of deep karst in the Mediterranean and its vicinity upon the Messinian Event. The infilling of the cave can be related to the rapid rise of the sea level and the resulting lowering of the gradient as the Mediterranean Basin filled up again. According to the results obtained, this supposedly happened 5.2 million years ago.