## 2 Geological Setting  
The Tunjice Hills are located in the central part of Slovenia (Figure 1a). Structurally, the area represents the western margin of the tectonic unit of the Neogene PBS and is surrounded by the tectonic units of the Southern Alps, Eastern Alps, and the Dinarides. The juncture of these tectonic units with the still-active Sava fault in the north [49] represents a structurally and geodynamically complex area. North of the Tunjice Hills, the Southern Alps consist largely of Triassic carbonate rocks, mainly limestones, and also dolomites, shales, and sandstones with tuffs [50; 51]. North of the Southern Alps, the Upper and Lower Austraoalpine units of the Eastern Alps occur, consisting of low- to ultrahigh-grade metamorphic rocks [20; 52; 53]. The units are part of a large ALCAPA mega-unit [19]. The Oligocene volcanic and volcaniclastic rocks of the Smrekovec volcanic complex are located northeast of the Tunjice Hills [54]. To the south, the contact with the Dinarides is covered by Quaternary sediments. The Dinaridic basement consists of clay stones, siltstones, sandstones, and quartz conglomerates of the Carboniferous to the Permian [51], and is overlain by a thick sequence of Mesozoic carbonates [55]. To the west, southwest and southeast, the deeper marine rocks of the Mesozoic occur in the Tolmin nappe [45]. This structural complexity is recorded in the Neogene strata.  
The global regressive-transgressive cycles influenced sedimentation in the Tunjice Basin as well, from the Oligocene to the end of the Middle Miocene [51; 56]. The Oligocene sedimentary rocks consist of conglomerates and clays [51] and indicate initial Cenozoic sedimentation in the Tunjice Hills in a shallow marine environment [56; 57] before the formation of the PBS. Sedimentation continued with deposition of the Early Miocene (Egerian and Eggenburgian stages) conglomerates, sandstones, and marlstones, known as Govce beds, in a brackish and marine environment [51; 58], and are rich in fossil remains [57]. The regional distribution of similar Early Miocene deposits indicates the development of the western-southwestern part of a restricted shallow epicontinental sea in the Central Paratethys [59]. Sedimentation is not determined in the late Early Miocene (Ottnangian and Karpatian stages), when the evolution of the PBS started. The Badenian transgression [60] also influenced the studied succession in the Middle Miocene, when the Badenian wide-rift extension in the PBS was already in full progress [36]. Marls and sands were deposited, known as the Lasko formation [51]. The stable and warm paleoclimatic conditions during the Badenian period led to an expansion of fauna and flora [23; 40; 61], resulting in the preservation of many marine fossil remains. The Tunjice area share similar characteristics [51; 62]. At the end of the Middle Miocene, the Sarmatian strata were represented by marlstone, mudstone, sandstone, and calcarenites, which reflect deposition in a marine environment of reduced salinity, and are known as the Dol formation [51; 56]. Younger rocks (upper Miocene to Pleistocene) have not yet been determined in the Tunjice Hills.  
The Miocene strata in the Tunjice Hills were deformed during the Miocene by syn-rift and post-rift extensional and compressional processes, which led to the formation of the overturned syncline of Tunjice, with the northern limb in an inverse position [51; 56]. Thus, the youngest layers of the Dol formation are located in the center of the syncline (in the central part of the Tunjice Hills), the Middle Miocene layers of the Lasko formation are located north and south of the Dol formation and the lower Miocene layers of the Govce formation at the edges of the syncline (north and south of the Tunjice Hills; Figure 2). In addition, the Tunjice Hills are deformed by a dextral strike-slip fault, the so-called Tunjice Fault, in the NNW-SSE direction [47].