Frane Marković

Early Miocene European loess: A new record of aridity in southern Europe

The intercalation of silty units and coarse-grained units represented by conglomerates and breccia characterizes a Lower Miocene terrestrial sedimentary sequence in the North Croatian Basin, a part of the southwestern Pannonian Basin system. These sediments were previously interpreted as alluvial sediments, where the silty units would reflect deposition on a floodplain. However, in this study, we show new results that support a different interpretation of the genesis of the silty units. The units, which vary in thickness between 6 and 180 cm, are mostly composed of structureless loose silt. They are brownish yellow to yellowish brown in color and do not contain fossils. Scanning electron microscopy indicated that quartz grains show fracture faces, conchoidal fractures, V-shaped percussion marks, linear steps, and conchoidal crushing features. Such microtextures together with the macroscopic characteristics of the silt units indicate that they were deposited by wind. Therefore, this study reports the first occurrence of Miocene loess outside of China. Silt-sized particles were probably produced by salt-weathering processes on salina-type lake flats during long arid periods. Alluvial deposition was controlled by a more humid climate, so the intercalation of eolian silty units with alluvial conglomerates and breccias reflects alternation of arid and more humid periods in the early Miocene. This agrees with regional paleoclimate studies that show cyclicity in the climate, with a dry cycle and orbital-scale climate variability controlling paleoenvironmental and sedimentary changes in the area during the early Miocene.

Topography controlling the wind regime on the karstic coast: late Pleistocene coastal calcareous sands of eastern mid-Adriatic, Croatia

Aeolian dunes controlled by regional climate have been formed in many coastal areas of the Mediterranean Sea during the Quaternary. Generally, they are formed under a landward-blowing wind, and comprise numerous reworked penecontemporaneous shallow-marine carbonate grains. Along the eastern mid-Adriatic Sea, late Pleistocene aeolian and alluvial sands occur as isolated patches in karstic depressions on several islands and the Pelješac Peninsula. At most localities, the sands consist of a mixture of mostly carbonate rock fragments and siliciclastic material. A higher proportion of shallow-marine bioclasts was found only at one locality. The terrestrial material was transported to the coastal area by at least two rivers: paleo-Cetina and paleo-Neretva River, and was subsequently reworked and transported by wind, resulting in aeolian deposition. Sandy units of various thicknesses exhibiting sharp erosional bedding planes and cross-bedding are interpreted as representing aeolian dunes and sand sheets controlled by a complex wind regime. The mineralogical composition at almost all localities indicates near-river flood plains as the main sand source. Although the area was affected by strong winds blowing landward and parallel to the coast, they significantly deviated due to the local topography produced by the tectonically deformed and karstified carbonate basement. In this way, the late Pleistocene aeolian deposits on the mid-Adriatic islands differ from deposits from most Quaternary Mediterranean coastal aeolian belts, as they contain very small quantities of penecontemporaneous shallow-marine carbonate grains and were deposited by winds blowing in varying directions instead of prevailing landward-blowing winds.