The coralline flora of a Miocene maërl: the Croatian “Litavac”

The fossil coralline fl ora of the Badenian bioclastic limestone outcropping in Northern Croatia is known by the name “Litavac”, shortened from “Lithothamnium Limestone”. The name was given to indicate that unidentified coralline algae are the major component. In this first contribution to the knowledge of the coralline flora of the Litavac, Lithothamnion valens seems to be the most common species, with an unattached, branched growth-form. Small rhodoliths composed of Phymatolithon calcareum and Mesophyllum roveretoi also occur. The Badenian benthic association is dominated by melobesioid corallines, thus it can be compared with the modern maërl facies of the Atlantic Ocean and Mediterranean Sea. Since L. valens still survives in the present-day Mediterranean, an analogy between the Badenian Litavac and the living L. valens facies of the Mediterranean is suggested

Middle Miocene (Upper Badenian/Sarmatian) Palaeoecology and Evolution of the Environments in the Area of Medvednica Mt. (North Croatia)

In the area of Medvednica Mt., the Upper Badenian and Sarmatian deposits are divided into four facies associations: (A) deposits of a small carbonate platform represented by breccia, conglomerates, biocalcirudites, biocalcarenites and biocalclutites; (B) open-sea deposits composed of marls with intercalations of clay; (C) nearshore deposits of reduced salinity composed of conglomerates, sandstones, biocalcarenites, biocalcirudites and biocalclutites, and (D) lagoonal deposits represented by spongitic calclutites with clay, marl and sand intercalations. Deposits of these facies associations contain numerous and very diverse fossil species with very different palaeoecological characteristics, from shallow- and deeper-water normal marine to shallow- and deeper-water environment of reduced salinity, even of fresh-water. The transition from Late Badenian to Sarmatian deposition was characterized by three different unconformities and one conformity. Unconformities are located between different lithologies reflecting an amount of uplifting and erosion at the end of the Badenian. The occurrence of an angular unconformity suggests the influence of local tectonics. The Middle Miocene deposition shows different local variations but generally fits with the evolution of Central Paratethys and the Pannonian Basin System

GREBENI I DRUGE BIOGENE TVOREVINE U MIOCENSKIM NASLAGAMA SJEVERNOHRVATSKOGA BAZENA – ČUDESNA RAZNOLIKOST KOJU TEK TREBA ISTRAŽITI

During the early stages of the Middle Miocene transgression marine biota invaded the newly formed Paratethys Sea. Reefs and reef-like structures particularly flourished with life, supported by the favourable climate conditions. Miocene biogene buildups show a variety of fossil assemblages and lithologic features. The main reef-builders were bryozoans, coralline algae, corals, oysters, vermetids, sponges and serpulids. Water turbidity and depth were major ecological factors controlling the reef biota. Lithofacies types at the studied localities in Northern Croatia show significant similarity with the Upper Langhian (Middle Badenian) of the Leitha Mountains in Austria, but can also be well compared with Miocene to recent reef structures in the Mediterranean. The Miocene reef-like buildups exhibit different porosity rates and other lithological characteristics.Tijekom početne faze srednjomiocenske transgresije marinski organizmi naselili su novonastalo more Paratethys. Zahvaljujući pogodnim klimatskim i okolišnim uvjetima život je bio posebno raznolik na grebenima i grebenolikim strukturama. Miocenske biogene tvorevine na raznim lokalitetima u području sjeverne Hrvatske pokazuju raznolikost fosilnih zajednica i litoloških osobina. Glavni grebenotvorci bili su mahovnjaci, koralinacejske alge, kamenice, vermetidi, spužve i serpulidi. Glavni ekološki faktori koji su kontrolirali grebensku biotu bili su donos čestica i hraniva s kopna i iz dubina vode. Tipovi litofacijesa pokazuju veliku sličnost s gornjolangijskim (srednji baden) gorjem Leitha u Austriji, a mogu se usporediti i s miocenskim i recentnim grebenskim strukturama u Mediteranu. Razne vrste miocenskih grebenolikih tvorevina pokazuju različitu šupljikavost i druge petrofizičke osobine. Koraligenske biokonstrukcije danas nastaju kao konkrecije u slabo osvijetljenim uvjetima, pogodnim scijafilnim algama, u vodi relativno hladne, ali stalne temperature, jednoličnoga saliniteta i niske energije. Nastaju na stjenovitoj podlozi i na pokretnoj podlozi u donjoj litoralnoj zoni i katkad na obalnome detritusu. Rast im započinje nastankom rodolita unutar pijeska i šljunka (platformske koraligenske zajednice). Aktualistički princip pomaže nam razumjeti ranu pojavu koraligenskih tvorevina na početku srednjomiocenske transgresije. Početna rodolitna faza rezultira slabo vezanim bioklastičnim naslagama. Dijagenetski procesi dodatno povećavaju njihovu šupljikavost, uslijed otapanja aragonitnih bioklasta. To je otapanje agresivno u vrlo plitkim staništima i povećava se s dubinom. Promjenjiva šupljikavost koraligenskih tvorevina istraživana je tijekom terenskoga rada na području Medvednice. Uzorci stijena s velikim rodolitima već na prvi pogled pokazuju najveću šupljikavost, dok su briozojsko-koralinacejski frejmstoni najkompaktniji. Time se otvara prostor za daljnja istraživanja ovih zanimljivih naslaga

MIDDLE MIOCENE DROWNED RAMP IN THE VICINITY OF MARIJA BISTRICA (NORTHERN CROATIA)

Uz cestu Marija Bistrica - Adamovec, nedaleko od raskrižja prema Lazu, može se na izdancima pratiti slijed srednjomiocenskih naslaga. U bazi slijeda vide se polimiktni, klastpotporni do matrikspotporni konglomerati. Valutice uglavnom odgovaraju sastavu okolnih stijena, a vezivo predstavlja koralinacejski bioklastični vekston. Sekundarni nalazi velikih oštriga upućuju na moguća ostrižišta, vjerojatno nedaleko od riječnoga ušća. U zaštićenim lagunama stvarali su se rodoliti malih dimenzija, živjele su halimede i nježni, razgranjeni mahovnjaci i puževi. U oligotrofnim uvjetima alge su učestalije od mahovnjaka. Zbog isparavanja povećana je koncentracija i kristalizacija kalcijeva karbonata, koji je cementirao bioklaste. Oko nekih su bioklasta vidljive kortoidne ovojnice, a sediment je tipa grejnston. Rodolitno-briozojske biokonstrukcije nastajale su najviše u plitkoj potplimnoj zoni, najvjerojatnije na dubinama od 20 do 30 m. Mjestimice su izgrađivale barijere između laguna i otvorenoga mora. One se nisu uspjele sačuvati in situ, već kao fragmenti u bioklastičnim taložinama padine. Na strmijim padinama pokazuju mikrostrukturu floutstona. Sadržavaju velike briozojske kolonije i bioerodirane solitarne koralje, kakvi su mogli živjeti u nešto dubljemu okolišu, vjerojatno između 30 i 75 m, uz nešto veću količinu nutrijenata. U vrhu slijeda, samo desetak metara iznad konglomerata, leže lapori s pučinskim organizmima (kalcitičnim nanoplanktonom, planktonskim i malim bentičkim foraminiferama i planktonskim puževima, pteropodima), kakvi su obično taloženi na distalnim padinama. Morska je razina brzo rasla, što je dovelo do naglih promjena u istraženome taložnom prostoru. Planktonski organizmi iz lapora upućuju na NN5 nanoplanktonsku zonu srednjega badena, pa se tonjenje rampe može povezati s početkom transgresivno-regresivnoga ciklusa TB 2.4.Fossiliferous Middle Miocene deposits from the surroundings of Marija Bistrica (north-east of Zagreb) transgressively overly older pre-Cenozoic bedrocks. Fossils from shallow marine environments are in most cases preserved as bioclasts, while deep marine calcareous oozes characterize the pelagic marls. The age of the transgressive sequence is estimated on the basis of planktic biota from marls (foraminifera, nannoplankton and pteropods) as the Badenian NN5 Nannozone. The following palaeoenvironments can be distinguished or presumed on the basis of biota and sedimentary features: (1) beach characterized by polymictic conglomerates with rhodolith-rich carbonate matrix; (2) oyster banks, recognized from secondarily found oyster clusters; (3) lagoons marked with compact bioclastic deposits and rhodolith-halimeda assemblage; (4) patch-reefs recognized from the surrounding bioclastic deposits; (5) shallow subtidal mäerl beds preserved as loose bioclastic deposits and (6) distal slope argillaceous marls with pelagic biota. Palaeoenvironmental analyses indicate rapid drowning, most probably corresponding to the transgression during the Middle Badenian TB 2.4 3rd order transgressive-regressive sequence

Neogene deposits of the western slopes of the Psunj Mt., Croatia: an overview of historical background and actualisation of geological research

On the crystalline rocks of the western slopes of the Psunj Mt. disconformably lie Neogene sediments with recorded deposits from the Lower Miocene to the Quaternary period. The basal Neogene sediments are in the older papers defined as “Oligomiocene” or “preTortonian”, today corresponding to the Lower Miocene sediments. These freshwater and marine-brackish sediments are transgressively overlain by the marine middle Miocene sediments. Badenian deposits are distributed as a continuous belt along the western slopes of the Psunj Mt., east from Pakrac and Lipik, with various lithofacies diversity. In the wider area they are a part of the structure Bijela Stijena–Novska. Lower Sarmatian rhythmic sediments conformably lie on the Badenian sedimentary rocks. The brackish and freshwater development is marked by the continuation of the Upper Miocene sedimentation, and Pliocene sediments with complete “Paludina beds” development mark the end of the Neogene. Dominant is the anticlinal structure – structure nose with an axis Bijela Stijena– Novska. In the core of the structure are crystallinic rocks. Neogene sediments are periclinal and almost continued along the limbs and forehead of the structure

The Miocene “Pteropod event” in the SW part of the Central Paratethys (Medvednica Mt., northern Croatia)

Deep marine Miocene deposits exposed sporadically in the Medvednica Mt. (northern Croatia) comprise pelagic organisms such as coccolithophores, planktic foraminifera and pteropods. The pteropod fauna from yellow marls at the Vejalnica locality (central part of Medvednica Mt.) encompasses abundant specimens of Vaginella austriaca Kittl, 1886, accompanied with scarce Clio fallauxi (Kittl, 1886). Calcareous nannoplankton points to the presence of NN5 nannozone at this locality. Highly fossiliferous grey marls at the Marija Bistrica locality (north-eastern area of Medvednica Mt.) comprise limacinid pteropods: Limacina valvatina (Reuss, 1867), L. gramensis (Rasmussen, 1968) and Limacina sp. Late Badenian (NN5 to NN6 nannozone) age of these marls is presumed on the basis of coccolithophores. Most of the determined pteropods on species level, except V. austriaca have been found and described from this region for the first time. New pteropod records from Croatia point to two pteropod horizons coinciding with the Badenian marine transgressions in Central Paratethys. These pteropod assemblages confirm the existence of W–E marine connection (“Transtethyan Trench Corridor”) during the Badenian NN5 nannozone. Limacinids point to the possible immigration of the “North Sea fauna” through a northern European marine passage during the Late Badenian (end of NN5-beginning of NN6 zone), as previously presumed by some other authors

Neogene deposits of the western slopes of the Psunj Mt., Croatia: an overview of historical background and actualisation of geological research

On the crystalline rocks of the western slopes of the Psunj Mt. disconformably lie Neogene sediments with recorded deposits from the Lower Miocene to the Quaternary period. The basal Neogene sediments are in the older papers defined as “Oligomiocene” or “preTortonian”, today corresponding to the Lower Miocene sediments. These freshwater and marine-brackish sediments are transgressively overlain by the marine middle Miocene sediments. Badenian deposits are distributed as a continuous belt along the western slopes of the Psunj Mt., east from Pakrac and Lipik, with various lithofacies diversity. In the wider area they are a part of the structure Bijela Stijena–Novska. Lower Sarmatian rhythmic sediments conformably lie on the Badenian sedimentary rocks. The brackish and freshwater development is marked by the continuation of the Upper Miocene sedimentation, and Pliocene sediments with complete “Paludina beds” development mark the end of the Neogene. Dominant is the anticlinal structure – structure nose with an axis Bijela Stijena– Novska. In the core of the structure are crystallinic rocks. Neogene sediments are periclinal and almost continued along the limbs and forehead of the structure