Budoš Limestone

Budoš Limestone
Stratigraphic range: Pliensbachian-Lower Toarcian ~192–182 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Rumija, where the southernmost Budoš Limestone emerges
Type	Geological formation
Thickness	50–60 m (160–200 ft)[1]
Lithology
Primary	Limestones alternated with green marls and calcareous stone
Other	Lithified limestone
Location
Coordinates	42°59′30″N 18°54′20″E / 42.99167°N 18.90556°E / 42.99167; 18.90556
Region	Nikšić
Country	Montenegro  Albania?
Type section
Named for	Budoš Mountain
Named by	Pantić
Year defined	1952[1]
Budoš Limestone (Montenegro)

The Budoš Limestone ("Budos Mountain Limestone", also known simply as High Karst Bioclastic limestones^[2]) is a geological formation in Montenegro and maybe Albania, dating to 192-182 million years ago, and 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 know from the Toarcian of Europe.^[3] 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.^[4] In the Adriatic section, this unit is an equivalent of the Calcare di Sogno of north Italy, as well represents almost the same type of ecosystem recovered in the older (Pliensbachian) Rotzo Formation of the Venetian region and the Podpeč Limestone of Slovenia, know also for its rich floral record.^[5]

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 paleogeography 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, that represented a shallow marine setting where ammonites are abundant, separated at the W of the Apulian Carbonate Platform by the "deep-water Adriatic Basin".^[6] The previous Pliensbachian platform suffered in the Toarcian a partial flooding in some sectors and simultaneous emergence in others, with the carbonate facies recovered at W of Nikšić, NE of Podgorica and in the Rumija Mt remaining as environments close to the marginal part.^[4] 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.^[4][6]

While at the Pliensbachian most of the area was dominated by the "Lithiothis Facies" from Tolmin to Podgorica, with no proper emegent lands nearby, in the Toarcian the nearest emergent lands expanded were located at the NE-SE, 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.^[4] 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.^[7] 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.^[8]

The Seoce Section is likely linked with the Budoš Limestone depositional setting, found mostly on the mountain of the same name on the Dinarides near Nikšić. The main unit is lithologically almost identical to the major fossiliferous levels of the Rotzo Formation, composed by bituminous limestones and marly limestones (fenestrate limestones and tempestites) with several episodes of emersions, 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 in the Adriatic region.^[5] The Budoš Limestone was delimited as younger than the Rotzo Formation due to its floral composition and the fact is overlain by the Late Toarcian-Aalenian greenish local claystone-limestone layers.^[5]

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 on semi-arid climates.^[9] 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 were Pachypteris dominated, and drier vegetation within the island regions of "Maquis shrubland" type (probably a number of species of the genera Brachyphyllum and Pagiophylum).^[10] Most of the research of the flora was done by Pantic between 1952 & 1981, recovering abundant Macroflora and Palynomorphs. Several other genera were recovered, such as Coniopteris (Dicksoniaceae), Caytonia (Caytoniales), Lindleycladus (Krassiloviaceae) and Elatides (Taxodiaceae).^[10] The nearest emgerged 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.^[11]

The Budoš Limestone was developed in a coastal setting with marine ingressions, likely a Mangrove-type environment (ex. with modern plants from Indonesia). Inland vegetation was probably dominated by Maquis shrubland (ex. with modern plants from from Italy)

It was considered initially that this flora grew in a continental setting, appearing on deposits that resemble modern inland deposition on ferric soils, thus, in a large inland valley with semi-arid conditions but with nearby large water bodies such as lakes.^[12] Latter however, was interpreted that this flora developed on an island setting in the Dinaric Carbonate Platform, likely linked with the exposed layers of Seoce. This setting would be made of the emerged Budoshi High, representing an island flora; a humid belt would have existed along the shore, while coniferous vegetation would have prevailed in the drier interior.^[13] The Budoš flora, as well Rumija and Seoce lithiotis facies were made after the Livari Supersequence created a massive lagoon in the inner ramp.^[7] A common facies in the 3 locations shows about 1-2 m thick lagoon parasequences, from lithiotis rich subtidal packstone to shallower wackestone, where the lagoonal shale facies recovering the flora is deposited.^[7]

The main consensus is that the layers rich in flora belong to a Bahamian-type Mangrove system developed on a coastal setting with a nearby Macchia arid inland setting dominated by Hirmeriellaceae and Araucariaceae conifers, as well Bennettites, that was either an island inside a Carbonate platform or part of a larger landmass.^[12] The mangrove system was mostly composed of seed ferns bearing the leaf genus Pachypteris linked with complex root systems that cover most of the layers, developed over and linked with the local aberrant bivalve (Lithiotis) reefs, together developed as a belt around the coast, yet is unknown how far reached.^[12] The inland setting was dry and with common wildfire activity, as proven by the great amount of charcoal recovered in some of the layers.^[12] The Lithiotis layers are intercalated by oolitic and oncolitic layers of likely subtidal/lagoonal origin, with several coastal cycles measured, such as development of lagoons and complete flooding of the vegetation levels, as well small coal-dominated sections. The ingression-regression trend allowed the development of the local mangroves.^[12]

The same type of ecosystem was also recovered more recently on slightly older (Late Pliensbachian) rocks on Albania that may belong to the same unit, with also great dominance of the genus Pachypteris linked with root systems along Lithiotis reefs, with evidence of catastrophic events which “killed” the flora.^[14] These types of layers have been vinculated with the early evolution of crabs.^[15]

The Budos Mountain facies, like the Rotzo Formation, the Podpeč Limestone or the Aganane Formation, are known mostly due to its massive bivalve associations of the genera Lithiotis, Cochlearites and Lithioperna that extended all along the Pliensbachian-Toarcian Adriatic-Dinaric-Hellenic Platforms forming mass accumulations of specimens that formed Reef-Like structures.^[19] This fauna appeared after the early Pliensbachian C-cycle perturbation, that triggered the diffusion of the Lithiotis Fauna, noted on the rapid widespread of this biota after the event layers.^[19] All of the genera related with this fauna appeared on the lower Jurassic, and all but one became extinct before the Middle Jurassic.^[20] This "Reefs" had a strong zonation, starting with the bivalves Gervilleioperna and Mytiloperna, restricted to intertidal and shallow-subtidal facies. Lithioperna is limited to lagoonal subtidal facies and even in some low-oxygen environments. Finally Lithiotis and Cochlearites are found in subtidal facies, constructing buildups.^[20]

Genus	Species	Location	Material	Notes	Images
Cotylederma[24]	C. sp.	Tejani	Multiple ossicles	An Crinoidean, member of the family Cotyledermatidae
Isocrinus[24]	I. psilonoti I. spp.	Tejani	Multiple ossicles	An Crinoidean, member of the family Isocrininae
Pentacrinites[24]	P. cf. fossilis	Tejani	Sections	An Crinoidean, member of the family Pentacrinitidae

Genus	Species	Stratigraphic position	Material	Notes	Images
Aratrisporites[10]	A. sp	Budos Mountain	Miospores	Affinities with Isoetaceae inside Lycophyta, as was found associated with the genus Pleuromeia.[25]
Bennettiteaepollenites[10]	B. sp.		Pollen	Affinities with Bennettitaceae inside Bennettitales. Abundant and Dry environment indicator
Calamospora[10]	C. sp.		Miospores	Affinities with the Calamitaceae inside Neocalamitaceae. Horsetail spores, associated with the genus Equisetostachys, herbaceous flora related to riparian high humid environments.[25]
Callialasporites[10]	C. sp.		Pollen	Affinities with the family Araucariaceae inside Pinales. comparable to the in situ pollen of Apterocladus.[25]
Cerebropollenites[10]	C. macroverrucosus		Pollen	Affinities with both Sciadopityaceae and Miroviaceae inside Pinopsida. This Pollen resemblance with extant Sciadopitys suggest that Miroviaceae can be an extinct lineage of sciadopityaceaous-like plants.[26]
Classopollis[10]	C. cf. chateaunovi C. "sp. A" C. "sp. B" C. "sp. C" C. meyeriana C. cf. simplex		Pollen	Affinities with the Hirmeriellaceae inside Pinopsida. The Pollen of the cone genus Classostrobus. Dominant Palynological residue, either indicator of dry conditions or association with coastal settings.[25]
Concavisporites[10]	C. cf. kaiseri C. "sp. A" C. "sp. B" C. cf. Gleichenia unbonatus		Miospores	Affinities with the genus Gleichenia inside Gleicheniaceae. Tropical Ferns related to humid ferric soils.
Cycadopites[10]	C. "sp. A" C. "sp. B" C. cf. follicularis		Pollen	Affinities with the family Cycadaceae inside Cycadales. It has been found in situ in cycadalean, bennettitalean, and ginkgoalean plants.[25]
Deltoidospora[10]	D. minor		Miospores	Uncertain Fern Miospores whose affinity cannot be concreted beyond Pteridophytes.
Densoisporites[10]	D. "sp. A" D. "sp. B" D. "sp. C"		Miospores	Affinities with Isoetaceae inside Lycophyta, as was found associated with the genus Pleuromeia.[25]
Duplexisporites[10]	D. problematicus		Miospores	Affinities with the family Cibotiaceae inside Cyatheales. Arboreal Fern Spores, resembling the ones found in the genus Cibotium.[25]
Foveosporites[10]	F. vissheri F. sp."		Miospores	Affinities with the family Lycopodiaceae inside Lycopodiopsida. Lycopod spores, whose appearance resemble the ones recovered on modern Lycopodium clavatum.[25]
Granulatisporites[10]	G. "sp. A" G. "sp. B" G. "sp. C"		Miospores	Affinities with Dipteridaceae inside Pteridophyta. Fern spores related to freshwater ponds.
Ischyosporites[10]	I. sp.		Miospores	Uncertain Fern Miospores whose affinity cannot be concreted beyond Pteridophytes.
Klukisporites[10]	K. variegatus K. neovariegatus		Miospores	Affinities with the family Selaginellaceae inside Lycopsida. The Klukia type isospore.[25]
Leptolepidites[10]	L. macroverrucosus L. cf. crassibalteus		Miospores	Affinities with the family Dennstaedtiaceae inside Polypodiales. Forested areas Fern Spores
Matonisporites[10]	M. cf. phlebopteroides		Miospores	Affinities with the genus Matoniaceae inside Gleicheniales. Ferns of several sizes, from both dry land and near water environments. It resembles the spores of the extant Gleichenia dicarpa.[25]
Monolites[10]	M. couperi		Miospores	Affinities with the Polypodiaceae inside Polypodiales. Ferns of several sizes, from both dry land and near water environments.
Murospora[10]	M. cf. bicolateralis		Miospores	Uncertain Fern Miospores whose affinity cannot be concreted beyond Pteridophytes.
Nannoceratopsis[10]	N. cf. gracilis		Cysts	A Dinoflajellate, member of the family Nannoceratopsiaceae. It is a genus related with Marine deposits.
Obtusisporites[10]	O. sp		Miospores	Affinities with the family Cyatheaceae inside Cyatheales. Arboreal Fern Spores
Pityosporites[10]	P. sp		Pollen	Affinities with the family Pinaceae inside Pinopsida. Conifer pollen from medium to large arboreal plants
Podocarpidites[10]	P. sp.		Pollen	Affinities with the Podocarpaceae inside Pinopsida. Conifer pollen from medium to large arboreal plants
Porcellispora[10]	P. longdonensis		Miospores	Dubious Genus with affinities with Bryophyta
Scrinocassis[10]	S. sp.		Miospores	Dubious Genus with affinities with Scriniocassiaceae. Brackish Green Algae, related to lagoonar water bodies
Skarbysporites[10]	S. sp.		Miospores	Uncertain Fern Miospores whose affinity cannot be concreted beyond Pteridophytes.
Styxisporites[10]	S. sp		Miospores	Uncertain Fern Miospores whose affinity cannot be concreted beyond Pteridophytes.
Verrucosisporites[10]	V. "sp. A" V. "sp. B"		Miospores	Uncertain Fern Miospores whose affinity cannot be concreted beyond Pteridophytes.
Vitreisporites[10]	V. pallidus		Pollen	Pollen from the Family Caytoniaceae inside Caytoniales. Pollen found associated with Caytonanthus.[25]

Genus	Species	Location	Material	Notes	Images
Brachyphyllum[1][10]	B. crucis	Budos Mountain	Branched shoots	Affinities with Araucariaceae or Hirmeriellaceae inside Pinales.
Coniopteris[1][10]	C. sp.		Isolated pinnae	A Fern of the family Polypodiales inside Polypodiidae. Common cosmopolitan Mesozoic fern genus. Recent research has reinterpreted it a stem group of the Polypodiales (Closely related with the extant genera Dennstaedtia, Lindsaea, and Odontosoria).[27]
Caytonia[1][10]	C. sp.		Pollen Organs	Affinities with Caytoniales inside Peltaspermopsida. Reproductive organ of the Peltaspermales, with berry like cupules with numerous small seeds arrayed along axes.
Equisetites[1][10]	E. columnaris E. sp.		Isolated Stems	Affinities with Equisetaceae inside Sphenopsida. Near water plants, associated with static freshwater ponds and other humid environments.
Elatides[1][10]	E. williamsoni		Branched shoots	Affinities with Cupressaceae inside Coniferales. Leaves from Arbustive to Arboreal Coniferous trees.
Eretmophyllum[1][10]	E. sp.		Branched shoots	Affinities with Ginkgoales inside Ginkgoopsida. Ginko Relatives with a more wider leaf, representing among the best specimens found on the mediterranean realm.
Lindleycladus[1][10]	L. lanceolatus		Branched shoots	Affinities with Krassiloviaceae inside Voltziales.
Otozamites[1][10]	O. beani O. cf.gramineus O. tenuatus O. sp.		Isolated leaflets	Affinities with Williamsoniaceae inside Bennettitales. Cycadales-Like medium sized trees. The most abundant flora on the Budos Mountain Limestone.
Pachypteris[1][10]	P. papillosa P. sp		Isolated pinnae	Affinities Corystospermaceae inside Corystospermales. The dominant floral remain over the mangrove-type layers
Pagiophyllum[1][10]	P. kurri		Branched shoots	Affinities with Araucariaceae or Hirmeriellaceae inside Pinales.
Ptilophyllum[1][10]	P. pectinoides P. cf. pecten		Isolated leaflets	Affinities with Williamsoniaceae inside Bennettitales.
Zamites[1][10]	Z. sp.		Isolated leaflets	Affinities with Williamsoniaceae inside Bennettitales.

• List of fossiliferous stratigraphic units in Italy
• Toarcian turnover
• Toarcian formations