Ljubljana University Library was built using, among others Podpeč limestone
This limestone has been used since Roman times in Slovenia, with artefacts crafted from this stone including funerary markers, altars, and boundary stones. The limestone was transported along the Ljubljanica river to Emona (now Ljubljana), where it featured prominently in major Roman structures. When the Roman Empire fell in the 5th century AD, stone extraction at Podpeč ceased for centuries.[2][7][8]
Archaeological findings in Emona showed this limestone was valued for its durability, in contrast to the less resilient sandstones, like the ones from Ljubljana Castle. It was also favored due to the accessibility of the quarries by redirecting the Ljubljanica River within a kilometer, facilitating transport.[2][8]
Interest in Podpeč Limestone remained minimal until around 1850, aside from a few historical buildings, such as a church portal from the 15th century. However, the stone gained popularity by the late 19th and early 20th centuries, leading to its use in various architectural elements like sills, lintels, and door frames in Ljubljana. It also became popular for monuments, fountains, and religious artifacts. The quarry remained active until production ceased in 1967, with the limestone also crushed for roadwork and shipped as blocks for stonecutting workshops.[2][8]
A notable user of this limestone was by the Slovenian architect Jože Plečnik, who applied them in the construction of several iconic structures in Ljubljana, including the Central Stadium, the Faculty of Natural Sciences and Technology, the National University Library, and various churches and altars. Other notable buildings featuring this stone include the Triglav Insurance Company Palace, sections of the Slovenian Parliament, and Ljubljana skyscraper.[2][8]
Paleoenvironment
The Podpeč limestones record a shallow Carbonate Platform sea, similar to modern Bahamas
In Slovenia, the northeastern margin of the Adriatic Platform displays a range of Lower Jurassic carbonate deposits, prominently seen from Tolmin through Vrhnika, Novo Mesto, Krško, and into the Gorjanci region. These deposits are characterized by well-layered, dark platform carbonates, including interbedded mudstones, fossiliferous wackestones, oolitic grainstones, and later-stage diagenetic dolomites.[6] This Slovenian carbonate sequence is comparable to those observed in adjacent regions like Croatia and Bosnia.[6] Hettangian-Sinemurian layers typically consist of white-grey, dense limestone, with some regions containing white carnous dolomite and in areas such as Hrušica and Notranjsko, dark grey, coarse-grained, bituminous dolomites are observed. The Pliensbachia facies are characterized by black, dense limestones that sometimes transition to black bituminous dolomite.[9]
Throughout the wider Adriatic Carbonate Platform in Slovenia and beyond, the transition to Toarcian carbonates shows a reduction in significant fossils, a trend also noted in the Croatian and Bosnian sections.[6]
The Podpeč type profile revelated a 75-meter-thick limestone sequence rich in diverse types, including micritic, bioclastic, and ooidal limestone, interspersed with marl, specially within the lower layers, while tectonic activity is evident in the upper sections.[2] The distinctive dark grey to black limestone is highly valued for its aesthetic appeal, marked by white fossilized bivalves. This limestone, known as a "lumachella," formed under low-oxygen lagoonal conditions and contains abundant Lithiotis-type bivalves. Faces similar to those at Preserje near Borovnica indicate littoral zones with alternating subtidal and supratidal conditions, similar to the present-day Bahamas, with occasional high-energy oolitic limestone beds reflecting dynamic water flow.[10]
During the Lower Jurassic, southern Slovenia was part of the Dinaric Carbonate Platform, a shallow marine environment adjacent to the deep-sea Slovenian Basin to the north and stretching into what is now Croatia. The Julian Carbonate Platform lay further north across the basin. Due to the depth of the basin, species exchange between the Dinaric and Julian platforms was unlikely. However, the narrowing of the Slovenian Basin near central Soča Valley may have allowed direct contact between these platforms.[4][11]
Within the Dinaric Platform, shallow, turbulent waters shaped the limestone formations, forming breccias and oolitic sands that built up into beaches and dunes. Coral reefs served as barriers, protecting southern lagoonal areas rich in organic material, where limited oxygen levels facilitated the formation of bituminous rock layers. Salinity fluctuations, caused by alternating drought and rainfall periods, drove dolomitization, transforming the sediments. The presence of tropical fossils, including Mytilus-like bivalves and land plants, as well as rare coal beds, indicates intermittent swampy land islands.[4][12][13]
The fossil record across these layers is diverse, preserving bivalves, gastropods, brachiopods, foraminifera, algae, and occasional coral. A rimmed carbonate platform model is proposed for the Podpeč region, positioning it near the oolitic platform margin with a sheltered lagoon landward characterized by low-energy, mud-rich limestone. Neighboring areas like Trnovski Gozd share these conditions, while sites like Kočevje and Suha krajina reveal lithiotid dolomite layers, breccias, and coal-bearing deposits from marshy environments. While some propose a ramp model, evidence such as cortoids and aggregate grains, as well as frequent emersion events, supports the rimmed platform model and a stable paleogeographic setting.[13]
This area, part of the ancient Adriatic plate, once lay in a tropical belt at lower latitudes, later shifting northward to its present location.[12]
A Terebratulidan brachiopoda, member of Plectoconchidae. Typical Mediterranean region taxon in the Pliensbachian, the main Branchiopod locally associated with the Lithiotids facies, where they formed rare mass occurrences at discrete intervals.[22]
An oyster, member of Plicatostylidae inside Ostreida. A large bivalve, with a subequivalved shell, up to 60–70 cm high. It is one of the Three main bivalves recovered on the Lithiotis Facies, with its accumulations generally overlying megalodontid coquinas.[23]
An oyster, member of Plicatostylidae inside Ostreida. Large, large and aberrant bivalves, it's accumulation have had different denominations on literature, such as banks, bioherms, biostromes, bivalve reefs or bivalve mounds.[23]
A clam, member of Astartidae inside Carditida. Is considered a genus that evolved from shallow burrowing ancestors, becoming a secondarily semi-infaunal edgewise recliner adapted to photosymbiosis.[24]
^ abcdefghijDozet, S. (2009). "Lower Jurassic carbonate succession between Predole and Mlačevo, Central Slovenia". Materials and Geoenvironment. 56 (2): 164–193. S2CID211559009.
^ abcdefghijkGeyer, O. F. (1977). "Die "Lithiotis-Kalke" im Bereich der unterjurassischen Tethys [The "Lithiotis Limestones" in the Lower Jurassic Tethys realm]". Neues Jahrbuch fuer Geologie und Palaeontologie, Abhandlungen. 153 (3): 304–340.
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