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Alternating Lacustrine-Marsch Sedimentation and Subaerial Exposure Phases During Quaternary: Prečko, Zagreb, Croatia

West of Zagreb, within an area of 6 ha, four untils dodallig 60 m thickness have been recognized on the basis of core analysis, geological mapping, geophysical measurements in exploaration Wells and laboratory analyses. The deepest situated unit (Unit I) accumulated during the Lower Pleistocene. It is interpreted to have formed by accumulation of loess mixed with local Materials (loessoid). Unit II is considered to be Middle Pleistocene in age. While in its lower and middle part fluviatile-lacustrine sediments are recognized, in the upper part aeolian material contributed to the composition of the sediments. This unit is overlyin by Unit III which is considered to be Upper Pleistocene in age. The composition of the unit is dominated by material of loess origin, and is interpreted to have formed in a marshy environment. The youngest unit (Unit IV) is composed of holocene fluviatile sediments. The upper parts of Units I, II and III display palaeosol features indicating that were subejected to the action of soil forming processes during phases of subaerial exposure. These occured as a result of lake/marsh infilling wihch happened during the cold and dry glacials and probably lasted during the older periods of interglacials. Resumption of shallow and quiet water invironments during the younger periods of interglacials is congruous with the increased influence of humidity. The formation of both, specific sedimentary environments and phases of subaerial exposure was also influenced by differently displayed neotectonic activity which was only partly compensated for by sedimentation and denudation respectively.

Pleistocene; holocene; Limnic; Paludal and fluviatile deposits; loessoid; Palaeoclimate; Palaeosol; Conditional marker horizon Q'; Prečko; Zagreb

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