Early Eocene evolution of carbonate depositional environments recorded in the Čikola Canyon ( North Dalmatian Foreland Basin , Croatia )

The stratigraphic succession in the Čikola Canyon (part of the North Dalmatian Foreland Basin) was studied in detail to describe both the sedimentological characteristics and fossil assemblages of the Lower Eocene deposits during the initial stage of the foreland basin formation. The North Dalmatian Basin now represents a part of the Outer Dinarides, and was developed in front of the evolving Dinaric structures by tectonic deformation and marine transgression of an emerged and denuded Mesozoic Adriatic Carbonate Platform (AdCP). During the initial phase, a distal ramp of a foreland basin was formed, characterised by carbonate sedimentation, lasting until the Middle Eocene. In a studied section more than 300 m thick, porcelaneous foraminifera, Alveolina, Orbitolites and complex miliolids (Idalina, Periloculina) prevail, associated with conical agglutinated forms, nummulitids and red algae. These samples belong to the SBZ 11–12 (Ypresian), according to occurrences of Alveolina decastroi, Alveolina cremae, Alveolina multicanalifera and Coskinolina liburnica. Two main lithological units have been described: 1) mudstones to wackestones with sporadic occurrences of ostracods and charophyceae, deposited in restricted lagoonal settings with several episodes of freshwater influences, and 2) foraminiferal packstones to grainstones with complex miliolids, alveolinids, corallinacean algae and nummulitids, deposited within inner and middle ramp settings. Palaeogene deposition of ramp carbonates in the Outer Dinarides area was mainly controlled by the continuous compressional tectonics, and the deposits today appear in more or less discontinuous outcrops. Palaeogene transgression occurred at different times over various parts of the former carbonate platform area, and subsequent carbonate sedimentation was characterised by deposition in similar environments during different time intervals over spatially restricted carbonate ramps controlled by synsedimentary tectonics. Article history: Manuscript received November 08, 2016 Revised manuscript accepted February 25, 2017 Available online February 28, 2017


INTRODUCTION
The aim of this study was primarily to determine the microfacies properties of the Čikola river canyon carbonate deposits rich in Larger Benthic Foraminifera (LBF).These determined forami niferal assemblages and their ecological requirements combined with the study of other carbonate-producing biota (corals, bryo zoans, echinoids, molluscs, coralline red algae), enabled the definition of the palaeoenvironmental settings of the Lower Eocene deposits known as the Foraminiferal limestones.
The studied section is located in the Outer Dinarides, the unit being composed mainly of carbonate rocks, ranging in age from the Upper Carboniferous to the Eocene (VLAHOVIĆ et al., 2005).The studied deposits belong to the more or less continu ous Palaeogene belt oriented NW−SE along the NE Adriatic coast (ĆOSOVIĆ et al., 2008a) (Fig. 1), i.e. to the North Dalmatian Foreland Basin (BABIĆ & ZUPANIČ, 1983, 2007, 2012;MRI-NJEK et al., 2012).
The Lower Palaeogene carbonate succession in the area is underlain by karstified Upper Cretaceous rocks (subaerial expo sure commenced during the Campanian; MAMUŽIĆ, 1975).The Kozina beds, the oldest Palaeogene deposits, which originated locally within restricted lagoons are marked by a shift from freshand brackish-water environments to a fully marine regime in the area.During the Eocene the shallow-marine (neritic) carbonate succession rich in LBF, known as the Foraminiferal limestones, was deposited within carbonate ramp environments (DROBNE et al., 1991;BABIĆ & ZUPANIČ, 2016 with references therein) over either the Kozina beds or directly onto karstified Cretaceous deposits.The ramp deposits pass upward into glauconite-bearing marly Transitional beds, overlain in some areas by a turbiditic succession of flysch and/or by a thick succession of Promina beds (MRINJEK et al., 2012).
The most important characteristic of the studied Palaeogene carbonate deposits are the abundance and diversity of the LBF.They are an endosymbiont-bearing (LEE, 1998;HALLOCK, 1999, and references therein), highly diversified and specialized group of organisms with specific environmental preferences re garding temperature, salinity, water energy, light intensity, and substrate type, numerous in the photic zone of oligotrophic tropical and subtropical seas (HOTTINGER, 1983(HOTTINGER, , 1997;;BOUD AGHER-FADEL, 2008).This makes them, apart from being ma jor carbonate producers, excellent shallow-water environmental/ palaeoenvironmental indicators (HOTTINGER, 1983(HOTTINGER, , 1997;;HO HENEGGER, 2004, 2005), because their presence indicates spe cific water temperature, salinity, light conditions, energy and seabottom conditions.Based on the abundance of specific groups of LBF, the Foraminiferal limestones in the Outer Dinarides are often informally subdivided into separate members: miliolid-, alveolinid-, nummulitid-, and/or orthophragminid limestones.Deposits of each member originated under different palaeoenvi ronmental conditions, and their spatial and temporal distribution  (modified after ĆOSOVIĆ et al., 2008a;DROBNE et al., 2011) with the location of geological columns from Fig. 5, (B) geological map (modified after MAMUŽIĆ, 1971;IVANOVIĆ et al., 1973IVANOVIĆ et al., , 1977;;ĆOSOVIĆ et al., 2008a;DROBNE et al., 2011;MRI NJEK et al., 2012), and (C) panoramic view of the studied Čikola section.Late Cretaceous rudist limestones are unconformably overlain by the studied Kozina Beds and Lower Eocene Foraminiferal limestones, which are conformably overlain by the Promina beds (modified after MRINJEK et al., 2012).
suggests an overall deepening of the sedimentary settings during the Early Eocene and early Middle Eocene.
Our results could shed additional light on the deposition of the Foraminiferal limestones, and provide more data about the evolution of the Northern Dalmatian Foreland Basin during the Eocene.New data will help in completing the picture of the evo lution of the Eocene shallow-water (neritic) sedimentary system of the Outer Dinarides, including a discussion of palaeogeograph ical terminology.

GEOLOGICAL SETTING AND STRATIGRAPHY
The studied area represents part of the North Dalmatian Foreland Basin developed in front of the evolving Dinaric structures by tectonic deformation and marine transgression of an emerged and denuded Mesozoic Adriatic Carbonate Platform (AdCP).During the initial phase, a ramp was formed as a distal part of a foredeep in the Dinaric foreland basin system, and carbonate sedimenta tion existed on a flank of a broad forebulge until the Middle Eo cene (BABIĆ & ZUPANIČ, 2008, 2012).
Deposition during the Palaeogene was significantly control led by tectonic deformation caused by the propagation of the Di naric orogeny towards the SW.The Palaeogene shallow-marine (neritic) carbonates were deposited on a carbonate ramp (ĆOSO-VIĆ et al., 2008a), named the Palaeogene Adriatic Carbonate Platform (PgAdCP) by DROBNE et al. (2009DROBNE et al. ( , 2011)).The upward deepening of the carbonate ramp produced a 220 m thick succes sion (IVANOVIĆ et al., 1976) of carbonates in the studied region.The succession is composed of palustrine and marginal marine carbonates, often referred to as the Kozina beds overlain by neritic deposits known as the Foraminiferal limestones (for general overview see VLAHOVIĆ & VELIĆ, 2009).Deposition of the overlying Transitional beds (ĆOSOVIĆ et al., 2008a) and turbiditic deposits (flysch) started when ramp carbonate production was unable to keep pace with subsidence.The subsequent shal lowing of depositional environments is recorded in the small pig gyback sub-basins within the Promina basin (KORBAR 2009;MRINJEK et al., 2012), where the succession of Promina beds (SCHUBERT, 1904(SCHUBERT, , 1908;;MAMUŽIĆ, 1971;IVANOVIĆ et al., 1973IVANOVIĆ et al., , 1977) ) of the Middle Eocene to Oligocene age were deposited in thickness of up to 2000 m (BABIĆ & ZUPANIČ, 2012;MRINJEK et al., 2012).

MATERIALS AND METHODS
The studied section is located in the well-exposed road-cut along the local road passing across the Čikola river canyon (Fig. 1B, C).The geographic coordinates of the first and last sampled intervals are 43°50 '8.9"N, 16°2'49.3"E and 43°50'20.4"N, 16°2'58.2"E,re spectively.The section encompasses a 310 m thick carbonate suc cession which was measured and sampled in detail to document both the sedimentological characteristics and fossil assemblages (Fig. 2).
Over 300 samples were collected for microfacies and micro palaeontological study and more than 270 thin sections represent ing various microfacies types were analysed.A total of 12 micro facies types have been defined based on LBF assemblages and sedimentary textures.
Carbonate microfacies were distinguished according to DUNHAM's (1962) classification modified by EMBRY & KLOVAN (1971).For the microfacies analysis the methods of WILSON (1975) and FLÜGEL (2010) were applied.In order to study environmental conditions, the visual examination and semi-quantitative analysis of lithology, grain types (biogenic or abiogenic), textures and fossil assemblages was performed.The modal distribution of components in thin sections was estimated by using a point-counting method (FLÜGEL, 2010).On each examined thin section, a two-dimensional grid of 1 cm 2 was mark ed, and each grain within a grid was counted.From there, an estimated volume of a given grain type proportional to the counted numbers of a particular grain type was calculated.In de scriptions of identified microfacies, to simplify the results, esti mated volumes of particular grain types are presented semi-quan titatively by four subgroups: 'no grains', 'rare grains' (volume less than 15 %), 'common grains' (15 to 49 %), and 'abundant grains' (volume over 50 %).The microfacies types and foraminiferal assemblages enabled interpretation of the palaeoenviron mental conditions of the studied deposits similar to existing car bonate-ramp models (BUXTON & PEDLEY, 1989;BURCHETTE & WRIGHT, 1992;GEEL, 2000;POMAR, 2001;ROMERO et al., 2002;BASSI, 2005;BOSENCE, 2005;ZAMAGNI et al., 2008;TOMASSETTI et al., 2016).POMAR's (2001) subdivision of shallow-water carbonate environments from euphotic to oligo photic ones was also applied.

Stratigraphy of the Čikola section
The Palaeogene deposits in the studied Čikola section (Figs. 1, 2) may be divided into two stratigraphic units, S1 and S2, then fur ther subdivided into five sub-units (S1a, S1b, S2a, S2b and S2c), based on their fossil content (mainly foraminifera) and sedimen tary textures.
The S1 unit transgressively overlies massive light-coloured Upper Cretaceous rudist-bearing limestones.The non-deposi tional phase between the Upper Cretaceous and Palaeogene de posits is not easily recognizable in the field, since in the studied section it is not represented by any visible angular unconformity or infillings of continental deposits, and even karstification is not clearly visible everywhere.The detailed studies of thin sections reveal a reduction of fossils towards the youngest Cretaceous rocks, and the presence of Microcodium sp.aggregates in over lying beds, which are typical for the early stages of palaeosol de velopment in many Peri-Tethyan sections (KOŠIR, 2004).
The oldest Palaeogene deposits, stratigraphic unit S1, are composed of an alternation of well-bedded wackestones to pack stones and thin-bedded mudstones to wackestones.At the begin ning of a succession, the thin-bedded limestones are intercalated with a few cm thick coal layers.The lower part of S1 unit, the S1a, is characterised by a specific fossil content (gastropods, cha rophyceae and ostracods), while in the upper, S1b unit, the de creasing abundance of ostracods and gastropods is related to the increasing abundance of small miliolids and discorbids.
The lower part of the overlying stratigraphic unit S2 consists of well-bedded foraminiferal wackestones to packstones with a rich LBF assemblage, whereas a massive appearance characterises deposits in the upper part of the unit.In the lowermost part -the S2a unit -miliolids dominate, while the middle part (the S2b unit) has a diverse foraminiferal assemblage: miliolids, alveolinids, ag glutinated conical foraminifera and Orbitolites sp.In the upper part of the unit, S2c, massive coarse-grained foraminiferal pack stones occur with lenticular-shaped nummulites, fragments of zooaxanthellate corals (z-corals) and corallinacean red algae (in cluding small rhodoliths) and rare orthophragminids.The top of the Čikola section is conformably overlain by massive mudstone beds with thin streaks, normal-graded interlaminae and lenses of silt or very fine-grained sand, interpreted as initial fine-grained subneritic deposits of the Promina beds (MRINJEK et al., 2012).

Facies association and microfacies types
Regarding the composition of foraminiferal assemblages and as sociated biota as well as sedimentary textures, the studied suc cession has been divided into twelve microfacies types, MFT 1 to MFT 12 (Fig. 2).

MFT 1 -Non-fossiliferous mudstone to wackestone
Microfacies MFT 1 is composed of mudstones characterised by a lack of fossils, more or less intense recrystallization, often com mon scattered dolomite crystals, and locally visible Microcodium sp.clusters (Pl. 1, Fig. 1).
Interpretation: Carbonates of the MFT 1 microfacies were deposited in a shallow, inner ramp setting, where episodes of sub aerial exposure (as indicated by Microcodium sp.) occurred.A lack of fossils characterised supratidal conditions within an inner ramp setting.
This microfacies overlays the Upper Cretaceous rudist-bear ing limestones, and represents initial deposition over a regional unconformity (Cretaceous to Palaeogene stratigraphic hiatus).
Interpretation: The low-diversity fossil assemblage composed of thin-shelled ostracods, charophyceans and cyanobacteria sug gests episodic fresh-water influxes.The common presence of D. barattoloi, known as a pioneering organism in modifying the envi ronments to become more suitable for other organisms (ĆOSOVIĆ et al., 2008b), supports such an interpretation.These described con ditions are typical of low-energy, protected brackish lagoons.
This microfacies is typical for the basal part of the Čikola section, the S1a stratigraphic unit, representing the oldest Palae ogene deposits in the studied area (Fig. 2).

MFT 3 -Dolomitized gastropod wackestone to packstone
MFT 3 is represented by wackestones to packstones (Pl. 1, Fig. 3).Skeletal particles comprise abundant gastropods (Stromatop sis sp. and Cosinia sp.) and common charophyceae.The gastro pod shells are often compressed, fragmented, and intraskeletal pores are infilled by fine-grained wackestone to packstone.Finegrained micritic matrix is often recrystallized, with common to abundant dolomite crystals scattered in the matrix or within in terparticle cement.
Interpretation: The presence of charophyceae and gastro pods indicate a freshwater influence, thus deposition probably took place in a brackish environment, whereas the micritic ma trix suggests a low turbulence environment.
This microfacies occurs in the first 30 m of the Čikola sec tion (S1a stratigraphical unit) and contains eight coal intercala tions, each a few cms in thickness (Fig. 2).
Interpretation: The sedimentological and palaeontological features imply deposition in a very shallow, low-energy, restrict ed marine environment, where small epiphytic foraminifera (small miliolids) and discorbids thrived.Occurrences of agglutinated conical foraminifera, related to protected, relatively nutrient-rich lagoonal environments (GEEL, 2000) support this environmental interpretation.
This microfacies, together with MFT 3, is a dominant micro facies in the lower 45 m of the Čikola section, but it occurs throughout the entire Čikola section, especially in stratigraphic units S2a and S2b to the 175 m of the Čikola section (Fig. 2).
Interpretation: According to HOTTINGER (1983,1997), VECCHIO &HOTTINGER (2007) andAFZAL et al. (2011) conical agglutinated foraminifera occupied soft muddy sea-bottom at depths just below the tidal level.Thus, this microfacies is in terpreted as having been deposited in the protected, low-energy, shallowest parts of the innermost ramp.
This microfacies occurs in the stratigraphic unit S2b of the Čikola section.The first occurrence is at around 80 m and it is present almost until the end of the section (Fig. 2).
This microfacies occurs for the first time at c. 35 m from the base of the Čikola section within the stratigraphic unit S1b, but prevails at the beginning of stratigraphic unit S2 (within subunit S2a), and continues up to the 110 m mark in the Čikola section (Fig. 2).
This microfacies is dominant in the stratigraphic unit S2b of the Čikola section.The first occurrence is recorded around 70 m and it is present continuously almost until the end of the section (Fig. 2).

MFT 8 -Peloidal-foraminiferal packstone
The MFT 8 is represented by packstones with dominant peloids (Pl.2, Fig. 2) of varying sizes and shapes, irregular to rounded, and foraminiferal tests.Fine-grained micritic matrix occasionally shows partial recrystallization.Where peloids are sparsely distributed, the micritic matrix and partially recrystallized ma trix (sparitic matrix) occur, and where peloids are densely packed, it is hard to distinguish them from the surrounding micritic ma trix.Dominant skeletal allochems are recrystallized rotaliid foraminifera.Porcelaneous foraminifera, which are mostly deformed and bioeroded, and echinoderm fragments are common.Skeletal remains are wellsorted and some of the agglutinated conical fora minifera are compacted.
This microfacies occurs in the stratigraphic unit S2b of the Čikola section, starting from 120 m (Fig. 2).
Well-sorted grainstones are easily recognizable macroscopically because of the abundance of oriented, up to 3 cm long alveolinid tests.
Interpretation: MFT 9 represents a high-energy environ ment, under the influence of waves and currents.Alveolinids pre ferred algal or sea-grass substrates, although they could have lived on all kinds of substrates.They inhabited shallow-water, protected environments (including protected inner ramp settings) but, also, sand shoals near and below fair-weather wave base (GEEL, 2000).Abraded alveolinid tests and well-sorted grains indicate their probable deposition on inner ramp shoals.Generally, porcelaneous foraminifera (miliolids and alveolinids) are abundant in normal marine and, occasionally hypersaline la goons (HOTTINGER, 1974;TORRICELLI et al., 2006).
This microfacies appears several times along the Čikola sec tion within stratigraphic unit S2b (Fig. 2).

MFT 10 -Nummulitid packstone
The MFT 10 is composed of coarse-grained packstones with complete, fragmented and/or abraded (outer whorl missing) lenticular tests of nummulitids (Pl.2, Fig. 4).The tests are randomly ori ented, and the matrix is composed of fine bioclastic fragments.Nummulitid packstones are easily recognizable macroscopically because of the abundance of up to 15 mm long nummulitid tests.
Interpretation: The deposits identified as MFT 10 originat ed in a high-energy environment, where wave and current action was significant.Nummulitids are bottom dwellers, and can be found at depths less than 30 m, but are dominant at mesophotic to oligophotic depths (≥30m; HOHENEGGER, 2005).Small-and medium-sized lenticular forms lived in various environments within the platform interior, and can form banks (AIGNER, 1983;GEEL, 2000).Specimens of Nummulites larger than 8 mm are frequent in nearshore shoals (TORRICELLI et al., 2006).The prevalence of tests larger than 8 mm suggests that rocks of this microfacies were deposited on shoals.
This microfacies appears in stratigraphic unit S2c of the Čikola section.
Interpretation: Coarse-grained matrix with numerous bio clasts (in particular, Neorotalia spp.) within packstones suggests a higher-energy environment.The co-occurrences of mixotrophs, such as z-corals and LBFs, suggests mesophotic conditions.The encrusting foraminifera are associated with corals (occupying cryptic and semi-cryptic microhabitats; BOSELLINI & PAPAZ ZONI, 2003) and therefore follow the same environmental re quirements as corals.It is known that in the mesophotic zone, corals lived and grew along with red algae (MORSILLI et al., 2012).In such settings, the high hydrodynamics provided the energy to rework bioclasts and produce skeletal packstones.This microfacies occurs in the last 30 m of the Čikola sec tion, at the beginning of stratigraphic unit S2c (Fig. 2).
Interpretation: Rhodoliths dominated by sporolithaceans and melobesioids occur below 60 m depth, and are characteristic of recent carbonate environments below the fair-weather wave base in tropical and subtropical seas (BASSI, 2005) in a wide va riety of settings, including back-reef, reef-flat and channels, forereef and also in deeper water down to 250 m (BOSENCE, 1983).Rhodophyceae live at greater depths than other algae because they can better utilize the blue light that penetrates furthest into the water (LEE, 1998) and their occurrence marks the lower limit of the oligophotic zone.Coralline algae Lithotamnion sp. and Mesophyllum sp. are today found between 30 and 80 m depth on the Indo-Pacific shelves (ADEY, 1979) and similar facies were interpreted as being deposited in the upper photic zone (RASSER, 2000;NEBELSICK et al., 2013), as suggested by the occurrences of Nummulites (HOTTINGER, 1997).Small rhodoliths in pack stones with fragmented bioclasts suggest some degree of bottom current reworking (BASSI, 2005).
Based on the skeletal composition and textures, deposits of this microfacies probably accumulated in a moderate-high en ergy areas within the mesophotic zone, probably in the proximal part of the middle ramp, well above the SWB, closer to FWWB.This microfacies occurs only in the last 7 m of the Čikola section, at the end of the stratigraphic unit S2c (Fig. 2).

Biostratigraphy
The S1 unit of the Čikola section is characterised by occasional freshwater influences and alternating coal intercalations.The dominant organisms have no biostratigraphic value, so the deter mined fossil association does not allow age attribution.

DISCUSSION
During the Early Eocene in the studied area, a succession of car bonates around 300 m thick was deposited within shallow-water (neritic) settings, ranging from brackish to protected marine en vironments (represented by MFT 1 to MFT 7) to inner and mid dle carbonate ramp environments (represented by MFT 8 to MFT 12).A palaeoenvironmetal model for the studied succession is provided in Fig. 3.The Čikola succession is interpreted as having been deposited in subtropical, oligotrophic and euphotic to mix ophotic environments based on microfacies characteristics.
A total of 12 microfacies types (MFT 1 to MFT 12) have been distinguished, demonstrating a diverse array of depositional and palaeoenvironmental conditions.They reflect a great diver sity of shallow-marine biota, especially LBF as a highly diversi fied group with specific environmental preferences (HOT TINGER, 1983, 1997) within fluctuating environmental conditions.Restricted, lagoonal environments with fresh water influence (occurrences of charophyceae along with ostracods and gastropods) are recorded in microfacies units MFT 1 to MFT 3 (S1 unit in Fig. 2).Foraminiferal limestones (S2 unit in Fig. 2), composed of microfacies MFT 4 to MFT 12, with miliolids, LBF (including alveolinids and orbitolitids) and agglutinated conical foraminifera, were deposited in the inner ramp settings.Differentiation between two sub-settings based on the proportion of particular foraminiferal genera in assemblages was done.The microfacies MFT 4 and MFT 6 originated under low-energy con ditions are characterised by the dominance of miliolids and spo radic occurrences of small, unidentified rotaliids.Diverse assem blages of alveolinids (fusiform to elliptical forms, representatives of A-generation), agglutinated conical foraminifera, larger mili olids, orbitolitids and z-corals characterised inner ramp settings.Where the influence of wave action was significant, shoals were formed, as indicated by the MFT 9 and MFT 10.The middle ramp settings were characterised by a high abundance of corallinacean red algae (MFT 12) while LBF are present in decreased propor tions (Fig. 3).The dominance of fragments of LBF and macrofos sils indicate the high-energy, well-lit part of the middle ramp.A melobesoid assemblage thrived in mid-latitudes within shallowwater warm-temperate settings (AGUIRRE et al., 2000).Fossil shallow-water corallinaceans have been reported from the Tethy an areas (BOSENCE, 1983;BASSI, 1998BASSI, , 2005;;BASSI & NEBEL SICK, 2010) and their co-occurrence with LBF indicates some what deeper settings.The succession ends with massive mud stone beds with thin streaks, normal-graded interlaminae and lenses of silt or very fine-grained sand, representing initial (prethrusting) fine-grained subneritic deposits belonging to the be ginning of the Promina beds (MRINJEK et al., 2012), suggesting a probably tectonically induced ending of Foraminiferal lime stone sedimentation.Deposition in the Čikola section was char acterised by shallow-marine (neritic) environments showing an aggradational pattern, composed predominantly of inner-ramp deposits, above the FWWB, except for the last 10 metres.Fo raminiferal limestones were deposited at the beginning of the foreland basin evolution and represent a bedrock of a wedge-top sub-basin filled up by Promina beds.
Lack of biostratigraphic markers in the S1 unit prevented precise age attribution of the oldest Palaeogene deposits, (the Kozina beds), in the Čikola section.In adjacent areas, the Palaeogene transgression started in the middle 'Cuisian' (SBZ 11;DROBNE et al., 1991).The beginning of sedimentation in the studied section is also assumed to be middle 'Cuisian', based on the fact that identified alveolinids and associated foraminifera from continuously overlying deposits, belong to the SBZ 11-12.
As mentioned, SBZs 11-12 correspond to the Late Ypresian (SERRA-KIEL et al., 1998) and during that period an almost 300 m thick succession of carbonates was deposited.Such a mas sive amount of carbonates testifies to a fine equilibrium having been established between the tectonically induced creation of ac commodation space/subsidence and significant carbonate sedi ment production, especially as in the Čikola section there is no evidence of subsequent drowning in the form of Transitional beds and/or flysch deposits, typical for most other areas with Palaeo gene deposits.
As evidenced, the main characteristic of these deposits is the abundant and diverse assemblage of LBF, major carbonate pro ducers of the Early Palaeogene carbonate environments (HOT TINGER, 1997;PEARSON, 2012).Their occurrence in the area was controlled by the palaeolatitudinal position of the North Dal matian Foreland Basin during the Early Palaeogene, at approxi mately 38°N (MEULENKAMP & SISSINGH, 2000, 2003) (Fig. 4) and by the early Palaeogene "warm" climate.The long-term global warming, beginning in the Late Palaeocene and culminat ing during the Early Eocene Climatic Optimum (EECO -ZACHOS et al., 2001) with tropical sea-surface temperatures of 28 to 32°C (PEARSON et al., 2007), enabled abundant carbonate production even in the areas which should, according to their pal aeolatitudes, be characterised by a more temperate climate.The sea-level fluctuations, along with variations in the configuration of the sedimentary basins and different subsidence rates, also contributed to such sedimentary scenarios (development of dif ferentiated environments -from lagoons and shoals to innermiddle ramp settings).
3) In some areas, including the studied one, the complete ramp system succession was not developed.Comparison with neighbouring regions reveals its complete development in Istria, whereas in Dalmatia (Ravni kotari, Hvar and Pelješac area) only some parts of the entire sequence were documented.(CHOROWICZ, 1975;MARINČIĆ et al., 1976;JELASKA et al., 2003;ĆOSOVIĆ et al., 2006).
5) The discrepancy in age and physiography of depositional settings probably resulted from diachronous deformation of the progressively evolving orogen (KORBAR, 2009) during the Early to Middle Eocene.Intense tectonic activity might have pre vented the full development of ramp settings.Therefore, the Palaeogene deposits in the Outer Dinarides may be considered as syn-orogenic deposits connected to the development and the evolution of foreland basin(s) and were deposited in basins control led by deformation related to the Dinaric orogen (SCHMID et al., 2008;KORBAR, 2009).
Palaeogene deposits were accumulated on the deformed for mer AdCP, mostly above the regional unconformity (OTO NI-ČAR, 2007;KORBAR, 2009;BRLEK et al., 2014).Gently folded AdCP deposits were during the Palaeogene gradually drowned and covered by a complex network of depositional environments for which the term Palaeogene Adriatic Carbonate Platform was proposed (DROBNE et al., 2009(DROBNE et al., , 2011)).However, during most of the Palaeogene, a completely different depositional system was formed, because (1) the former area of the Mesozoic AdCP was only partially covered by Palaeogene marine deposits, (2) instead of the previous vast, relatively flat shallow-marine Mesozoic AdCP, during the Palaeogene complex carbonate ramp deposi tional systems were formed, and (3) deposition was primarily con trolled by compressional synsedimentary tectonics and although carbona te production (represented mostly by LBF) was an impor tant factor (as shown in the Čikola section example), the prevail ing force in modifying the accommodation space was tectonics, while on the AdCP, the dominant factor in sedimentation was car bonate production keeping balance with the subsidence (VLA-HOVIĆ et al., 2005).
Therefore to avoid terminological confusion, a specific name for such a complex Palaeogene depositional system should be proposed, in order to clearly distinguish it from the underlying Adriatic Carbonate Platform.
Based on lithology, grain types and fossil assemblages (mainly LBF) 12 microfacies types were identified, showing con solidation and development of a fully marine regime.Microfacies MFT 1 to MFT 3 are typical of deposits originating within re stricted, unstable environments with the influence of fresh water.The inner ramp wackestones to packstones (microfacies MFT 4 to MFT 11), with abundant and diverse LBF assemblages were deposited under low-to high-energy conditions, i.e. in protected lagoons ( MFT 5,6,7), inner high-energy parts of carbonate ramp (MFT 9, 10) and in distal inner ramp settings (MFT 11).The mid dle ramp environments were recorded by the MFT 12, where corallinaceans and LBF cooccurred.
From the latest Cretaceous to the Bartonian in the area of the Dinarides several carbonate ramp systems were developed.Each ramp system was characterised by its different evolution through out its existence, including variable thickness, different ages of initiation and duration of marine conditions, and deposition in different sedimentary environments controlled primarily by syn sedimentary tectonics related to the evolving Dinaric orogen.

Figure 2 .
Figure 2. Studied stratigraphic column of the Čikola section showing the lithology, identified biozones (SBZ after SERRAKIEL et al., 1998) and distribution of the microfacies types MFT 1 to MFT 12 (left), and position of the studied section within a generalized stratigraphic column of the Upper Cretaceous-Eocene succession in the Čikola Canyon, Northern Dalmatia (MRINJEK et al., 2012) (right).

Figure 4 .
Figure 4. Simplified palaeogeographic reconstruction of the Mediterranean realm in the Early to Middle Eocene with marked position of the North Dalma tian Basin.The positions of the continents and ocean basins are adapted from MEULENKAMP & SISSINGH (2000, 2003) as presented in HÖNTZSCH et al. (2013).

4 )
Deposition in the entire North Dalmatian area, from the middle 'Cuisian' onward, was characterised by more or less con tinuous shallow-marine environments, except for a narrow trench characterised by deeper-marine environments that developed in the Palaeocene and extended westward from Montenegro and eastern Herzegovina