engleski

Drip hydrology recognized in speleothem architecture

Characterisation of the karst aquifers and associated processes that are essential for the interpretation of palaeoclimate speleothem proxy records requires observation of relationship between precipitation and cave discharge which reflects in speleothem architecture. Ten stalagmites were recovered from 5 caves located in Croatian part of the Dinaric karst: Modrič Cave (MOD ; Dalmatian coast), Strašna peć Cave (SP ; Dugi otok Island), Lokvarka Cave (LOK ; mountainous Gorski Kotar region), Nova Grgosova Cave (NG ; central Croatia) and Manita peć Cave (MP ; seaward side of Velebit Mountain). Within them, ten drip sites were monitored in terms of drip rates and isotopic composition, seven of them covering sites of collected speleothems. After 1-2 years of monitoring we compared speleothem fabrics visible on polished halves with drip intensities i.e. discharge type, showing different, but indicative relations. MOD speleothems covered with drip logging showed relatively homogenous petrography in accordance with very stable seepage flow. In NG cave, regardless of discharge regime, practically completely homogenized dripwater produces speleothems with very homogenous internal structure indicating relatively uniform deposition without visually observable hiatuses. LOK speleothems, which contain substantial portion of detritus and periodically interrupted growth, depict fracture flow very responsive to the surface events. MP speleothems keep records of aquifer evolution which led to variations in water supply i.e. possible shift from seepage to fracture flow upon the flowpaths widening, while SP speleothem probably recorded seismotectonic event which might have changed flow pattern noticeable in changed calcite fabrics. However, although the macroscopically observed growth pattern can provide provisional insight in hydrological behaviour, the most confident interpretation would arise from detailed micropetrography. The research was funded by the University of Zadar (project Reconstruction of the regional palaeoclimate change – speleothem records from the North Dalmatia (Croatia)) and Croatian Science Foundation (project HRZZ-IP-11-2013-1623 Reconstruction of the Quaternary environment in Croatia using isotope methods).

cave, drip hydrology, speleothem architecture, Croatia

nije evidentirano