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

Abstract

The intercalation of silty units and coarsegrained units represented by conglomerates and breccia characterizes a Lower Miocene terrestrial sedimentary sequence in theNorth Croatian Basin, a part of the southwestern Pannonian Basin system. These sedi ments were previously interpreted as allu vial 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 micro textures 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.

How Was the Late Neogene Red Clay Formed in the Ordos Plateau (Northwest China)?

“…Throughout the Miocene and Pliocene, the Wei and Yellow rivers accumulated a substantial amount of detrital material [52,53,55], which did not reach the sea but rather served as the foundational material for the development of red clay in the Ordos Plateau. This pattern of aeolian sediment development is also observed in various regions, including the northern foothills of the Altun Shan in the northern Tibetan Plateau ( [47]; Figure 1), the Tajik Basin in the western Pamir Plateau (Wang et al, 2016b; Figure 1), the Pannonian Basin in the Carpathian Mountains [132], and the Pampas Plain east of the Andes [133]. Hence, the significant amount of detrital material delivered by the consistent seasonal rivers ensured the effective deposition of Late Miocene and Pliocene red clay in the Ordos Plateau.…”

Alluvial-Lacustrine-Marine Complex of Mount Medvednica: The Early Syn-Rift Deposition and Palaeogeography (Early to Middle Miocene, North Croatian Basin)

“…Contemporaneously, in the area of Mt. Papuk (see Figure 2) a hydrologically closed lake evolved (saline lake, Šćavničar et al, 1983;Pavelić et al, 2022b), towards which rivers flowed from the source located in the south-west (Pavelić et al, 2016(Pavelić et al, , 2022b. These palaeoflow directions indicate the prevalence of a transverse drainage system on the alluvial plain that probably formed due to successive normal faulting and the backstepping propagation (sensu Heward, 1978) of the main extensional fault towards the south-west, i.e.…”

Magneto-biostratigraphy and paleoenvironments of the Miocene freshwater sediments of the Sarajevo-Zenica Basin

“…The long-lived lake phases of all DLS basins are coeval with the transition to and peak of the MCO (17-15 Ma;Holbourn et al, 2005), implying that the paleoenvironments were affected by the MCO, and the transitional period towards the optimum. A subtropical climate with a strong seasonality in precipitation existed in SE Europe in the Burdigalian, marking the onset of the MCO (Jiménez-Moreno et al, 2009;Pavelić et al, 2016). In the Pag Basin, an increase in xerophilous pollen suggests a gradual warming and drying of the climate (~17-16 Ma) (Jiménez-Moreno et al, 2009).…”

“…The drier and warmer periods were most likely amplified by eccentricity cycles, which were recognized in alternating limestone and lignite intervals, in distal parts of DLS basins, for example in Pag and Gacko (Jiménez-Moreno et al, 2009;Mandic et al, 2011). In the Požega basin of the North Croatian lakes, wet periods with braided alluvial fan deposition alternated with arid periods marked by loess-like deposition and cycles in a salina-type lake (~18-16 Ma) (Pavelić et al, 2016;Pavelić and Kovačić, 1999;Šćavničar et al, 1983). In the Sarajevo-Zenica Basin, the first sign of a warmer climate was found at the base of the extensional basin phase, where the main coal seam yielded plant remains of moderate-warm deciduous forests (Pantić et al, 1966).…”