Lithologic Composition and Stratigraphy of Quaternary Sediments in the Area of the Jakuševec Waste Depository (Zagreb, Northern Croatia)

Abstract

In the area covered by the ÒJaku¹evecÓ waste depository, to adepth of 101 m, six lithological units were determined based on fieldworkand laboratory geologic-geophysical investigations. It was discoveredthat the silty-clayey units (units 1, 3 and 5) are covered bysandy-gravely (units 2 and 4) and gravely ones (unit 6), respectively.These units constitute the sediments of the Middle and Upper Pleistocene and Holocene and are separated by erosional unconformities.The Pleistocene gravels are predominantly of quartz-quartzite compo -sition, while the Holocene ones are composed of carbonate cobblesand pebbles. In contrast, the sands exhibit a fairly uniform mineralcomposition throughout the column. The Pleistocene silt and clay aremostly composed of muscovite-illite and quartz with lesser amountsof chlorite, kaolinite and smectite. There is a difference in compositionof this fraction in unit 6, where the quartz, calcite and dolomiteparticles prevail and smectite and illite/smectite are absent. Unit 3 ischaracterised by the goethite content. The Pleistocene layers wereformed in a lacustrine-marshy environment while the Holocene sediments are fluviatile. This sedimentary sequence is interrupted byoccasional terrestrial phases, or drying-up periods, dependent on thepalaeoclimate conditions, particularly the interchange of cold and dryglacials with the warmer and more humid interglacial stages.