engleski

New evidence of glaciation of the Medvednica Mt. southern foothills from 80-m “BGG” borehole in central part of Zagreb terrace (NW Croatia)

Zagreb terrace is a curious geomorphological feature which attracted attention of only a few geologists. Pilar (1877) was the first to interpret the terrace as a glaciogenic depositional body after discovery of conical-shaped and striated clasts in its central part. This interpretation was disputed by Gorjanović (1906, 1907, 1908), almost 30 yeas later, when all of Pilar’s samples were already lost. Gorjanović’s interpretation of the terrace deposits was of fluvial and marsh origin, which was not challenged until 2013 when first new evidence of Medvednica Mt. glaciation became available. In February-April of 2017 several geomechanical boreholes were drilled at the location of the new University buildings (“BGG”) in the central part of terrace at 171 m a.s.l.. They were completely cored and the deepest reached the depth of 80 m, but not the bedrock. The recovered cores revealed glaciogenic facies, some of which have not been documented in the study area before. The “BGG” core documents glaciogenic origin of the Zagreb terrace sediments, and confirms Piar’s 1877 hypothesis on glaciation of the Medvednica Mt. It also documents the provenance of debris from central Medvednica Mt., particularly its southern slope. The core also documents large thickness of glaciogenic sediments on the Zagreb terrace, which exceeds 80 m. Several alternating packages of subglacial lacustrine sediments with lodgment tills indicate several phases of ice-advance, and significant climate oscillations which have affected southern Central Europe and represent new evidence of the extent of the Pleistocene ice cap in SE Europe. However, the exact timing of the ice-advance and retreat periods is unknown at this stage of research, since no datable material was found so far.

diamicts, tills, Medvednica Mt., glacigenic debris

nije evidentirano