The Seoca Lithiotis Limestone ("Budoš Mountain Limestone", also known simply as High Karst Bioclastic limestone is a geological formation in Montenegro and possibly Albania that dates to 185-183 million years ago, covering the Pliensbachian-Toarcian stage of the Jurassic Period. It is located within the high karst zone, and represents a unique terrestrial setting with abundant plant material, one of the few known from the Toarcian of Europe. It is the regional equivalent to the Toarcian-Aalenian units of Spain such as the Turmiel Formation and the El Pedregal Formation, the Sinemurian Coimbra Formation in Portugal, units like the Aganane Formation or the Tafraout Group of Morocco and others from the Mediterranean such as the Posidonia Beds of Greece and the Marne di Monte Serrone of Italy. In the Adriatic section, this unit is equivalent to the Calcare di Sogno of Northern Italy. It represents almost the same type of ecosystem recovered in the older (Pliensbachian) Rotzo Formation of the Venetian region and the Podpeč Limestone of Slovenia, known also for its rich floral record.
Regional Context In Montenegro, Lower Jurassic carbonate deposits are seen intermittently along the Adriatic Carbonate Platform extending from Herzegovina into the region and reaching northern Albania. The Toarcian palaeogeography of Montenegro was characterised by two major units, mostly found in the Dinarides: the High Karst Zone, representing the Carbonate Platform, and the Budva Basin, which represented a shallow marine setting where ammonites are abundant, separated at the W of the Apulian Carbonate Platform by the "deep-water Adriatic Basin". The previous Pliensbachian platform suffered partial flooding in some sectors and simultaneous emergence in others during the Toarcian, with the carbonate facies recovered at S of Nikšić, northeast of Podgorica and in the Rumija Mt remaining as environments close to the marginal part. These layers, generally overlaid by younger sediments, exhibit oolitic limestone characteristics, with late-diagenetic dolomite intercalations indicative of formation near the platform's margin. Key exposures appear west of Nikšić, northeast of Podgorica, and within the Rumija Mountain range. During the Pliensbachian, most of the area was dominated by the "Lithiotis Facies" from Tolmin to Podgorica, with no proper emergent lands nearby, In the Toarcian, the nearest emergent lands were located to the northeast–southeast, from the west of Zagreb to Prozor, while the sectors at Montenegro and Albania were located in between ooid grainstone levels, representing a proximal carbonate ramp. The Budva basin evolution in the Toarcian was marked by the changes in the sea level, developing a distally steepened ramp until the Lower Toarcian, and an accretionary rimmed platform in younger layers. The Adriatic-Dinaric Carbonate Platform is well measured at the Mount Rumija where the transitional facies between the platform setting and the deeper pelagic environment is seen, recovering a lateral transition from a lagoonal environment exposed in Seoce to the platform edge, exposed in Tejani (called Tejani section), and finally the deeper water environment, called Livari section can be observed at the own Mount Rumija.
Description The formation is ~450 m thick and comprises well-bedded light brown to light grey limestones organized into meter-scale shoaling-upward cycles. Typical microfacies include lumachelle beds of Plicatostylidae, bioclastic packstone/wackestone, oncoid–peloid grainstone, and fenestral pelmicrites. Fenestral textures, vadose features (mouldic/corrosion voids with meteoric cements) and intermittent nodular horizons occur toward the top of cycles. Deposition took place in intratidal to supratidal lagoons along the platform interior; the uppermost part records opening toward deeper settings that were rapidly blanketed by Aalenian oolites. The base lies on Late Triassic Lofer Limestones without angular discordance; the top transitions sharply to Aalenian oolitic sands (Oolites of Mt. Rumija II). The Liassic age (likely Pliensbachian–early Toarcian) is constrained by the Plicatostylidae facies, Foraminifera content and upward passage into Middle Jurassic oolitic units documented on Rumija. The main unit at Budoš is lithologically almost identical to the major fossiliferous levels of the Rotzo Formation, composed of bituminous limestones and marly limestones (fenestrate limestones and tempestites) with several episodes of emersion, all of coastal origin and rich in plant detritus and leaf remains, connected to the typical Lithiotis reefs found in the Pliensbachian–Toarcian carbonate platforms of the Adriatic region. The unit is mostly known by its rich macroflora, the most complete of the Mediterranean Toarcian realm along with the Marne di Monte Serrone, with several characteristics, such as the abundant presence of thermophilic Bennettitales and the dominance of the Seed Fern Pachypteris, that grew in semi-arid climates. This particular province is characterized by fossil plants that belonged to the specific vegetation of intra-oceanic islands with the dominance of "mangrove"-type swamps where ''Pachypteris'' dominated, and drier vegetation within the island regions of "Maquis shrubland" type (probably a number of species of the genera Brachyphyllum and Pagiophylum). The nearest emerged areas were present in the terrains of Sinjavina and Durmitor, marked by a paleorelief of Jurassic Bauxite-abundant deposits within karstified limestones and rare dolomites.
Paleoenvironment
… excerpt ends here. Continue reading the full article.
