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The Lower Cretaceous shallow-marine succession of Mljet Island in Croatia records the geological history of the southern part of the Adriatic Platform during its last tectonically quiet period, prior to the Late Cretaceous collision processes between the Adria Microplate and the Eurasian Plate. We studied the Early Cretaceous biostratigraphy of benthic foraminifera and calcareous algae in order to establish a precise, combined benthic biozonation for the Adriatic, which in turn facilitates a better understanding of the global distribution of these microorganisms during the Early Cretaceous. Thirty-four species from 26 genera of benthic foraminifera and 32 species of calcareous algae, distributed among 11 genera, were recovered from the Lower Cretaceous shallow-water carbonate rocks of Mljet Island in southern Croatia. Nine biostratigraphical units, eight of which are based upon the benthic foraminifera and calcareous algae, and one upon the microencruster Bacinella irregularis, have been distinguished within this interval: the Clypeina parasolkani-Humiella catenaeformis Interval Zone (Berriasian–earliest Valanginian), Epimastopora cekici-Pseudoclypeina? neocomiensis Interval Zone (Late Valanginian), Montsalevia salevensis Taxon-range Subzone (Late Valanginian), Clypeina? solkani Abundance Zone (late Early and Late Hauterivian), Salpingoporella melitae-Salpingoporella muehlbergii Interval Zone (Barremian), Bacinella irregularis Assemblage Zone (Early Aptian), Salpingoporella dinarica Abundance Zone (Late Aptian), Orbitolina (Mesorbitolina) texana-“Valdanchella” dercourti Interval Zone (Early Albian) and “Valdanchella” dercourti Taxon-range Zone (Late Albian). The stratigraphical position of the main genera and species of benthic foraminifera and calcareous algae within the Berriasian–Albian interval is discussed, and the established biozones are correlated within the Adriatic Platform domain. The Early Cretaceous diversification of benthic foraminifera in the area investigated can be shown to follow the sea-level curves for that period, and the major foraminiferal turnovers coincide with global sea-level rise and fall. During relative sea-level rises, coupled with reduced oceanic circulation and expansion of nutrient-poor, shallow tropical waters, these organisms were able to diversify into various euphotic habitats, particularly within shallow subtidal environments of the platform interior. Regressive episodes resulted in the reduction of oligotrophic habitats and a decrease in species richness.

Dark-gray oolitic units characterized by oversized ooids with primary radial calcite fabrics occur in the interior of the Late Jurassic Late Tithonian, Adriatic Platform, a large Mesozoic, Tethyan isolated platform in Croatia. They differ from open-marine, platform-margin ooid grainstones in their dark color, cerebroid outlines, broken and recoated grains, abundant inclusions, highly restricted biota, and lack of cross-stratifiThey have been interpreted as being of vadose origin (“vadoids”) at tops of upward-shallowing parasequences. However, detailed sections show that most oolitic units occur at bases of precessional parasequences, overlying erosional surfaces on fenestral carbonates. The oolitic units are similar to quiet-water ooids that form today in low-energy settings. They developed in an arid climate during initial transgression of supratidal fl ats, along lowenergy shores seaward of tidal fl ats, and along the margins of restricted lagoons and intertidal ponds. Superimposed fenestral fabrics, meniscus micrite cements, and grain breakage occurred as they aggraded to high-tide level and were subjected to wetting and drying, thermal expansion and contraction, and wind transport. They migrated landward with transgression, forming extensive sheets, and were overlain by subtidal lagoonal facies that shallow up into fenestral carbonates. These distinctive facies may have been overlooked in the geological record, or their geological distribution requires juxtaposition of calcite seas, high-calcite supersaturation states, arid climate, and presence of fl at-topped carbonate platforms in a greenhouse world.

A continuous, ∼350 m thick succession of cyclic, predominantly muddy upper Callovian-lower Kimmeridgian shallow-marine carbonates was logged in southern Croatia to define the sequence stratigraphy. The basal, late Callovian part contains three sequences (AdCal-x to AdCal-z) dominated by parasequences consisting of intraclast-skeletal-peloid packstone-grainstone capped by fenestral-laminated carbonates. The bulk of the Oxfordian (eight sequences: AdOx-1 to AdOx-8) and lower Kimmeridgian (AdKimm-1) is represented by low energy and muddy lithofacies. The parasequences consist of basal skeletal-microbial lump wackemudstone capped by barren lime mudstone. Lack of tidal flat facies caps to parasequences indicates incomplete shallowing to intertidal depths, and suggests that some parasequences are amalgamated. Given the duration of Oxfordian (∼8 m.y.), these likely represent third-order cycles with an average duration of ∼1 m.y. (suggestive of long-term obliquity forcing). The total number of Oxfordian parasequences (57, ∼100 k.y. duration) is suggestive of short-term eccentricity forcing. Samples for δ13C analysis were collected every meter from bulk carbonate matrix. The carbon-isotope values vary from −2.3 to +4.0‰ PDB, and show two significant isotope excursions in the Oxfordian The isotopic signature shows relatively constant values (0.8–1.8 ‰PDB) for the late Callovian, followed by a negative excursion to 0‰ at the beginning of Oxfordian, and a stepwise increase to 2.7‰. The subsequent negative excursion (-2.3‰) is followed by a stepwise increase to 3.8‰ in the middle of Oxfordian, slight decrease with values remaining between 1.5‰ and 3.3‰, and finally by a stepwise increase with a positive excursion to 4.1‰ in the late Oxfordian. Stepwise positive shifts in carbon-isotope values in the middle and late Oxfordian are both associated with shallowing upward parts of sequences AdOx-3 and AdOx-6, respectively. The remainder of the curve shows generally decreasing C-isotope values into the lower Kimmerdgian. The studied succession supports overall late Callovian cooling (marked by tidal flats) followed by mid-Oxfordian maximum flooding (widespread subtidal facies), with parasequence development suggestive of short-term eccentricity forcing and superimposed long-term obliquity forcing. It is interesting that the dominantly subtidal Oxfordian of the Adriatic platform corresponds to time of intrabasin source rock formation in the Middle East.

Sequence Stratigraphy and Oxygen-Carbon Isotope Signal from Albian Platform-Interior Carbonates, Southern Croatia

Depositional sequences capped by peritidal carbonates and breccias on the Aptian Adriatic carbonate platform, Croatia, were studied to evaluate evidence for glacioeustasy within an age framework constrained by carbon-isotope chemostratigraphy. Sequence Ad1 (17–60-m [56–197-ft] thick; uppermost Barremian–lower Aptian) is dominated by shallow subtidal parasequences. Sequence Ad2 (7–13-m [23–43-ft] thick; lower Aptian–lowermost upper Aptian) contains oceanic anoxic event (OAE) 1a, associated with lagoonal laminated carbonates. Sequence Ad3 (3–8-m [10–26-ft] thick) probably is lower upper Aptian and likely is separated by a major hiatus from sequence Ad4 (8–20-m [26–66-ft] thick; uppermost Aptian), which spans OAE1b. Both Ad2 and Ad3 are dominated by peritidal parasequences updip in the lower transgressive systems tract and upper highstand systems tract and by subtidal parasequences elsewhere, whereas sequence Ad4 is dominated by shallow subtidal parasequences. Low accommodation rates (4.0–6.0 cm [1.6–2.4 in.] in the earliest Aptian, decreasing to approximately 1.0 cm/k.y. [0.3 in./k.y.] later) promoted widespread breccia development during relative sea level falls, aided by tectonic warping. The sequence-capping breccias, eccentricity-dominated cyclicity, restriction of peritidal facies to late highstands, and coeval off-shelf oxygen-isotope records all suggest that sea level falls occurred during times of cooling and had a significant glacioeustatic component. These intermittent cooler periods and continental ice buildup punctuated the Aptian greenhouse climate.

This study focuses on a 343-m-thick section of Upper Jurassic (Upper Calovian-Lower Kimmeridgean ; the bulk of the section is Oxfordian) shallow-marine limestone and lesser dolostone from Jasenice near Dubrovnik, Croatia. The section was logged bed-by-bed noting color, sedimentary structures, grain size, shape, sorting, constituents, and diagenetic overprints. The lower units in the section are characterized by small packages of cyclic subtidal to intertidal facies consisting of dolomite layers (some weakly laminated), peloidal skeletal wacke-packstone, packstone and grainstone, and capped by lime mudstone or burrowed laminite. Caps have fenestrae and rare scalloped contacts, indicative of subaerial exposure. The exposure contains some thrust faulting and associated breccia. Upsection, the facies become muddier and microbial lumps and burrows are more common. The transition into the Oxfordian is distinguished by thick packages of brown-colored lime mudstone, which alternates with coarse, thick to massive dolostone. The lime mudstones contain microbial lumps, shell fragments, and abundant nubeculariid foraminifera. Thin beds of lime wacke-mudstone and intermittent skeletal wackestone break up these larger beds. Both the lime mudstone and wacke-mudstone become barren for a span of almost 30 meters up-section. The presence of these thick mudstones suggests that the platform deposition slightly lagged accommodation due to sea level rise coupled with subsidence. The accommodation rate began to decrease or production rate began to increase in the later Oxfordian units indicated by an increase in microbial lumps, benthic foraminifera, and fragments of calcareous algae. The section extends into the basal Kimmeridgian, which is regionally identified by the appearance and abundance of calcareous alga Clypiena jurassica.

Coarse, fabric destructive post-depositional dolomites, Late Jurassic-Early Cretaceous Adriatic platform, Croatia: origin by mesohaline reflux

Facies stacking pattern, sequence stratigraphy and carbon-isotope signature of Albian platform-interior carbonates, southern Croatia

Some parasequences in the interior of the Early Cretaceous isolated carbonate platform, Croatia, which formed under a greenhouse climate, lack the typical regressive tidal flat laminites. Instead, these bioturbated emergent parasequences have burrowed and rooted upper parts, capped with thin greenish paleosols, and are reminiscent of Triassic “Lofer cycles.” We propose that the bioturbated cycle tops reflect coastal salinities that are normal marine, brackish, or metahaline, whereas the transgressive (rare) and abundant regressive tidal flat laminites formed under hypersaline coastal waters. Thus, these features may be used to track gross salinity changes of coastal waters on the platform through time. In addition, we suggest ways to evaluate whether the salinity changes relate to hypersaline embayments on the platform or changes in the climate at the parasequence scale. We propose that the bioturbated emergent parasequences could have formed under semiarid conditions, seaward of subtle, shallow embayments on the platform. Contemporaneously, in the bayheads, microbial laminites developed—these would require time-equivalent updip and downdip laminate-capped and bioturbated emergence–capped parasequences. However, the parasequences could also have been controlled by climate changes. The laminite-capped parasequences could have resulted from salinity increase with shallowing of the platform interior under semiarid conditions (stable climate). In contrast, the bioturbated emergence–capped parasequences could have formed during times of more humid climate punctuating the overall semiarid climate. The humid phase would have favored brackish to normal marine salinities in the coastal zone, along with macrophytes, and intense animal and plant bioturbation, which would suppress development of laminite caps. Thus, these parasequences provide a means of tracking gross salinity of coastal waters, and if climate induced, then they have implications for fluctuating climates in greenhouse worlds.

Albian cyclic peritidal facies of Adriatic platform interior in southern Croatia

Sequence Stratigraphy, Carbon Isotope Signature, and Dolomitization of a Late Jurassic Greenhouse Platform, Croatia

Marine platform dolomites, Late Jurassic Early Cretaceous Bahama type platform, Croatia

This study explores Aptian aged platform-interior carbonate facies exposed on the Peljesac Penninsula and the islands of Korcula, Hvar, and Mljet in Southern Croatia. The Lower Aptian succession is characterized by non-cyclic, thick-bedded to massive subtidal facies of lime mudstone and skeletal-intraclastic lime mudstone and wackestone with rare benthic foraminifera, calcareous algae, microbial encrusters (Bacinella), bivalve fragments, as well as subordinate pelagic crinoids (Saccocoma) and planktic foraminifers (Hedbergella). The shallowest facies are skeletal-peloid wacke-packstones and grainstones with rudists ; these are calculated to occur in about 0-3 meters water depth. The cyclicity of the facies increases with proximity to the Early-Late Aptian boundary. The Upper Aptian is more cyclic, with parasequences consisting of basal skeletal mudstone-wackstone overlain by peloid-intraclast-skeletal packstone and grainstone, and barren mudstone, fenestral lime mudstone or microbial laminite. The emersion breccia horizons and/or residual clay horizons as parasequence caps are very common ; up to seven horizons are recorded in the lower, and six in the upper part of Upper Aptian.Maximum water depths of facies are estimated at 5 meters based on the range of stratigraphic distances of facies below base of laminate cap, breccias, or top of barren lime mudstone. The facies stacking patterns suggest an important environmental change during Aptian, with Early Aptian transgression, coeval with drowning of numerous Tethyan carbonate platforms, and pronounced Late Aptian regression marking a significant biological crisis in the peri-Adriatic region. The published data show that accumulation rates for the southern part of the Adriatic platform were 4 cm/k.y. on average, reaching a minimum value of less than 1 cm/k.y. in the Aptian. These low accommodation and accumulation rates likely caused amalgamated subtidal facies in the Early Aptian, and periodic emergence and well-developed paleosols in the Late Aptian. The thickness variations between the columns may be due to syndepositional tectonics combined with sea level oscillations.

The Albian carbonate succession (approximately 400 m thick) of Adriatic Platform in southern Croatia, although predominantly peritidal, locally contains basal several meters thick sequence of deeper lagoon laminated limestones that were deposited during a regional deepening of the platform concomitant to oceanic anoxic event (OAE) 1B. Limestones are thin-bedded, platy, and planar laminated pellet packstone and lime mudstone, locally fine dolomite with petroliferous odor ; these rapidly pass up into meter-scale cycles dominated by fenestral caps suggesting relatively humid conditions. The cyclic peritidal carbonates that are markedly different from those described above make up the rest of the Albian. These meter-scale cycles consist of, from bottom to top: (1) Lime mudstone, locally heavily burrowed, with peloidal fills and scattered clam and gastropod fragments ; locally, this member is represented by coarse dolomite with rare oncoids and clam/gastropod moulds ; (2) pellet-skeletal wackestone with oncoids, calcareous algae and benthic foraminifera ; (3) peloid-skeletal-intraclast wacke-packstone with abundant calcareous algae (Salpingoporella) and benthic foraminifera, and scattered rudists and gastropods ; (4) intraclast-peloid-skeletal grainstone ; (5) gastropod and rudist floatstone to rudstone with lime mudstone, skeletal-peloid, or course dolomite matrix ; locally, oncoid-lump and pisoid rudstone ; (6) barren lime mudstone with tubular fenestrae and greenish infills, rare gastropod moulds ; (7) fenestral laminite ; platy and microbial laminite are subordinate ; (8) intra/lithoclast floatstone-rudstone with black and/or tan lime fenestral mudstone clasts or pebbles in a green clay, tubular fenestral wacke-mudstone, or dolomitized matrix. Cycles may also have basal thin transgressive lag of intraclast-oncoid floatstone in muddy matrix that grades up into skeletal bioturbated mudstone with gastropod fragments. Cycle tops are commonly microcarstic with mud-filled green vugs of leached mollusks, or with clay mm-seams.

A composite section through the Adriatic platform, Croatia from the Late Jurassic Kimmeridgian to the Early Cretaceous Albian stage provides a high-resolution climate and sea level record spanning fifty million years. The Kimmeridgian was dominated by warm humid conditions (local brackish alga Chara) marked by platform flooding interrupted by two cooling events, sea level fall and breccia development. The Tithonian warms into full-blown greenhouse conditions. The platform became increasingly semi-arid with meter-scale oolitic cycles capped by microbial laminites. Four cooling events punctuate the succession with the last one being in the Early Creataceous Berriasian (multiple subaerial breccia horizons). The Berriasian is cyclic with fenestral laminite or restricted, unfossiliferous lime mudstone capping most parasequences. The Valanginian is dominated by coarse dolomitized shallow subtidal carbonates and rare peritidal laminites. Transition from Valanginian dolomite to basal Hauterivian limestone may be synchronous with oceanic anoxic event (OAE) off the platform. The Hauterivian is dominated by well developed subtidal cycles with rooted horizons and mainly fenestral laminites suggesting humid subtidal to emergent conditions. Multiple emergence horizons at the top-Hauterivian and base-Barremian are associated with microkarsting and paleocave development. The Barremian contains abundant meter-scale cycles suggesting greenhouse conditions, becoming increasingly semi-arid upward (cycle caps become more stromatolitic and less fenestral compared to the lower part). Multiple short term cooling events are marked by black-pebble emergence horizons associated with sea level drops. The Early Aptian is marked by significant warming and shallow flooding of the platform and deposition of non-cyclic shallow carbonates. The Late Aptian is marked by multiple emergence horizons suggesting multiple cooling events and long term sea level fall. The Albian is marked by a regional deepening of the platform (OAE-1B) and deposition of deeper lagoon laminated limestones. This rapidly passes up into meter-scale cycles dominated by fenestral caps suggesting relatively humid conditions.

The Jurassic-Cretaceous Adriatic Platform provides a window into tropical shallow-marine carbonate deposition in the western Tethys. The highly cyclic Barremian sediments are superbly exposed on the islands and mainland of southern Croatia . Five logged sections, ranging from 20 to 100 m thick, display superbly developed peritidal parasequences ; the extensive Barremian microbial laminite facies likely contain the best preserved tidal flat facies compared to any Lower Cretaceous interval of the Adriatic Platform. The Barremian consists of 2 supersequences. The sequence boundary zone 1 in the Lower Barremian consists of up to 3 breccias. Supersequence 1 has at least 2 high frequency sequences. Sequence boundary zone 2 contains one to 2 breccias. Supersequence 2 has four high frequency sequences (HFS). Each HFS consists of shallowing upward succession with dominantly subtidal lower part, and laminated to fenestral upper part. Individual parasequences within each sequence are composed of shallow subtidal (lime mudstone and peloid-intraclast-skeletal packstone-grainstone) to intertidal (microbial laminites and fenestral lime mudstone) and subaerial exposure facies (greenish clay sheets or breccias with green clayey matrix). Presence of platform-wide subaerial exposure surfaces capping some cycles suggest relative sea level falls affected the platform over large areas. Most parasequences were formed by high-frequency sea level fluctuations perhaps related to orbital forcing ; possible durations of the interval and its component parasequences are being evaluated to see if these are compatible with a precessional vs longer term obliquity or eccentricity signals. Some parasequences probably also formed by autocyclic processes and local tectonics associated with the impending (Aptian) collision between the Adriatic microplate and Eurasia. Rapid thickness variations and facies changes over several tens of kilometers indicate that the synsedimentary differential subsidence (possibly over fault blocks) was a strong influence, with a superimposed sea-level fluctuations generating the sequences and component cycles.

The Late Jurassic-Early Cretaceous has been considered to lie in the Mesozoic “cool” mode of Frakes et al. (1992), as evidenced by oxygen isotope signals (VEIZER et al. 2000) and by the pCO2 plots GEOCARB III of BERNER & KOTHAVALA (2001). At the long-term scale, these climate proxies are in agreement, but at shorter time scales, there is some conflict both in degree or warming or cooling and timing of the events (VEIZER et al. 2000 ; ROYER et al., 2004). This study uses data from the Adriatic platform of Croatia to evaluate whether the approximately 5 to 6 m.y. long Late Jurassic Tithonian, has facies compatible with a Mesozoic “cool” mode (FRAKES et al 1992). Well exposed Mesozoic sections of the Bahama-like Adriatic Platform reveal the detailed stacking patterns of cyclic facies within the rapidly subsiding Late Jurassic (Tithonian) shallow platform interior (over 770 m thick, approximately 5 to 6 m.y. duration). Accommodation plots show four 3rd-order relative sea-level cycles, the third being the largest both in duration and magnitude (HUSINEC & READ 2007). Facies within parasequences include dasyclad-oncoid mudstone-wackestone-floatstone and skeletal-peloid wackestone-packstone (shallow lagoon), intraclast-peloid packstone and grainstone (shoal), radial-ooid grainstone (shallow subtidal/intertidal shoals and ponds), lime mudstone (restricted lagoon), fenestral carbonates and microbial laminites (tidal flat). Maximum water depths (estimated from distance below tidal flat units capping parasequences) generally were less than four meters, and facies show strongly overlapping depth ranges suggesting facies mosaics. Facies in the overall transgressive, Lower Tithonian sections are arranged in 1 to 4.5 meter thick parasequences dominated by subtidal facies, some of which are capped by very shallow water grainstone-packstone or restricted lime mudstone ; laminated tidal caps only become common toward the interior of the platform. Parasequences in the regressive Upper Tithonian are dominated by peritidal facies with distinctive basal oolite units and well developed laminite caps. Parasequence durations appear to be within the precessional band and eccentricity bundling is weak. Modeling suggests that precessional sea level changes were small (several meters) as were eccentricity sea level changes, supporting a global, hot greenhouse climate for the Late Jurassic (Tithonian) within the overall “cool” mode of the Middle Jurassic to Early Cretaceous.

The Adriatic Platform provides a window into carbonate deposition spanning the Jurassic-Cretaceous transition in the western Tethys. The sediments exposed on the islands of southern Croatia are highly cyclic. The Barremian section is characterized by extensive microbial laminite facies that is by far the best preserved tidal flat facies compared to any Lower Cretaceous interval of the Adriatic platform. Three logged sections, each between 150 and 200 m thick, display superbly developed peritidal parasequences. The parasequences are composed of shallow subtidal (lime mudstone and peloid-intraclast-skeletal packstone-grainstone) to intertidal (microbial laminites and fenestral lime mudstone) and subaerial exposure facies (greenish clay sheets or breccia with greenish clay or mud matrix). The majority of the cycles may have been formed by high-frequency changes in sea level perhaps related to orbital forcing ; possible durations of the interval and its component parasequences are being evaluated to see if these are compatible with a precessional vs longer term obliquity or eccentricity signals. Some parasequences probably also formed by autocyclic processes and local tectonics. Presence of platform-wide subaerial exposure surfaces capping some cycles suggest a relative sea level falls affected the platform over wide areas.

This study explores Aptian aged platform-interior carbonate facies exposed on the islands of Korcula, Hvar, and Mljet, Croatia. The Lower Aptian succession is characterized by thick-bedded to massive predominantly non-cyclic lime mudstone and skeletal-intraclastic lime mudstone and wackestone with benthic foraminifera, calcareous algae and microbial encrusters (Bacinella), as well as subordinate pelagic crinoids (Saccocoma) and planktic foraminifers (Hedbergella). The Upper Aptian is distinguished by a cyclic alternation of facies with typically basal skeletal mudstone-wackstone overlain by peloid-intraclast-skeletal packstone and grainstone, and barren mudstone, fenestral lime mudstone or microbial laminite. Many cycles are capped by greenish residual clay sheets and partially dolomitized breccias/conglomerates. The facies stacking patterns suggest an important environmental change during Aptian, with Early Aptian transgression, coeval with drowning of numerous Tethyan carbonate platforms, and pronounced Late Aptian regression marking a significant biological crisis in the peri-Adriatic region. The published data show that accumulation rates for the southern part of the Adriatic platform were 4 cm/k.y. on average, reaching a minimum value of less than 1 cm/k.y. in the Aptian. These low accommodation and accumulation rates likely caused amalgamated subtidal facies in the Early Aptian, and periodic emergence and well-developed paleosols in the Late Aptian.

Well-exposed Mesozoic sections of the Bahama-like Adriatic Platform along the Dalmatian coast (southern Croatia) reveal the detailed stacking patterns of cyclic facies within the rapidly subsiding Late Jurassic (Tithonian) shallow platform-interior (over 750 m thick, ca 5–6 Myr duration). Facies within parasequences include dasyclad-oncoid mudstone-wackestone-floatstone and skeletal-peloid wackestone-packstone (shallow lagoon), intraclast-peloid packstone and grainstone (shoal), radial-ooid grainstone (hypersaline shallow subtidal/intertidal shoals and ponds), lime mudstone (restricted lagoon), fenestral carbonates and microbial laminites (tidal flat). Parasequences in the overall transgressive Lower Tithonian sections are 1– 4AE5 m thick, and dominated by subtidal facies, some of which are capped by very shallow-water grainstone-packstone or restricted lime mudstone; laminated tidal caps become common only towards the interior of the platform. Parasequences in the regressive Upper Tithonian are dominated by peritidal facies with distinctive basal oolite units and well-developed laminate caps. Maximum water depths of facies within parasequences (estimated from stratigraphic distance of the facies to the base of the tidal flat units capping parasequences) were generally

The Late Mesozoic Barremian to Cenomanian southern interior part of the Adriatic platform, Croatia, is characterized by exclusively shallow water carbonate facies that were deposited in shallow water, peritidal environments. The succession is characterized by a relatively rich association of shallow marine benthic organisms, primarily foraminifers and dasyclad algae. The analysis of the entire microfossil association has provided a detailed biostratigraphic zonation based on the stratigraphic distribution of either benthic foraminifera or calcareous algae. Both the fossil and the sedimentary record point to several episodes of change in relative sea level, paleoenvironments, and distribution of paleocommunities dominated by benthic foraminifers and dasyclad algae. The Barremian to Cenomanian benthic foraminiferal assemblages, including a total of 106 species and 57 genera, were analyzed to establish the principal diversity patterns at (sub)stage level of resolution. The diversity patterns of benthic foraminifers in the study area appear related to regional changes in relative sea level, coupled with related changes in habitats. The observed diversity pattern of benthic foraminifers shows that after a relatively high diversification in the Barremian, the Early Aptian marked the foraminiferal diversity maximum. Foraminifers diversified into a suite of euphotic habitats backed by a relative sea-level rise that coincided with oceanic anoxic event (OAE-1A). The regional regression in the Late Aptian resulted in loss of “ deeper” subtidal habitats and, consequently, foraminiferal diversity drop. Transgression in the Early Albian and probable associated decrease in platform waters fertility, resulted in the gradual increase of diversity throughout the Albian. Regional onset of regression in the latest Albian, again could have increased nutrient supplies to surface waters, and consequently, the subsequent Early Cenomanian foraminiferal association reached its mid-Cretaceous diversity minimum. The Middle Cenomanian relative sea-level rise led to a gradual recolonization of the platform interior and the renewal of the benthic foraminiferal association. The present study, calibrated against the standard regional biostratigraphic zonation for the Eastern Adriatic mid-Cretaceous (Barremian to Cenomanian), documents that several species of benthic foraminifers have exceptional age-diagnostic value for the Barremian to Cenomanian biostratigraphy, the most important being orbitolinids (Campanellula capuensis, Palorbitolina lenticularis, Praeorbitolina cormyi, Orbitolina (M.) lotzei, O. (M.) parva, O. (M.) texana, “ Valdanchella” dercourti, Neoiraqia insolita, N. convexa), and alveolinids (Archaealveolina reicheli, Ovalveolina crassa, O. maccagnoae, Sellialveolina viallii, Cisalveolina fraasi), as well es ataxophragmiids (Voloshinoides murgensis) and chrysalinids (Protochrysalidina elongata, Chrysalidina gradata). These are generally abundant, have a widespread distribution and a restricted stratigraphic range. They evolved rapidly and became extinct suddenly.

Although the Mesozoic has long been considered greenhouse, the stacking patterns on Jurassic-Cretaceous platforms suggest that some intervals have formed under sea level changes that are too large for an ice free world. This is manifested in juxtaposition of facies or biotas in parasequences that represent 10 to 30 m shifts in water depths in excess of that expected from simple shallowing of several meters (the parasequence thickness). The presence of obliquity and short and long term eccentricity cycles also is suggestive of ice rather than the abundant precessional cycles that typify greenhouse platforms. We present data showing that the Late Tithonian of the Adriatic Platform represents a greenhouse phase. Well exposed Mesozoic sections along the southern Dalmatian islands (southern Croatia) can be used to evaluate the Jurassic-Cretaceous paleoclimate. The detailed stacking patterns of facies within the Late Jurassic (Tithonian) shallow platform interior (over 700 m thick) were examined. Facies include deeper lagoon dasyclad wackestone, oncoid wackestone, shoal-water skeletal and radial ooid packstone-grainstone, restricted lagoon lime mudstone, tidal flat microbial and fenestral laminites. They are arranged in 1 to 3 m thick parasequences. Parasequences likely are precessional (roughly 20 k.y. given the accumulation rates). They are arranged in sets 8 to 15 m thick composed of 3 to 6 parasequences, and possibly 100 k.y. duration. Lower Tithonian sets are dominated by subtidal parasequences passing up into thin, more shallow water parasequences. Upper Tithonian parsequences commonly have radial ooid grainstones at the base, and less commonly in upper regressive parts. Upper Tithonian parasequence sets have well developed tidal flat facies in upper parts. Estimation of water depths using the fenestral/microbial carbonate as a sea-level datum, shows that the subtidal facies formed in water depths of less than 5 m, and had overlapping depth ranges, implying mosaic-like facies patterns. These shallow water depths support very small precessional sea level changes forming the parasequences, compatible with very warm greenhouse climate. The high Tithonian subsidence rates favored relatively complete preservation of precessional cycles with few missing beats ; this also required that any eccentricity signal was very small, otherwise many precessional beats would not have been deposited on the platform top. Emergence near the Jurassic/Cretaceous boundary formed extensive sequence-bounding subaerial clayey and limestone breccia horizons interstratified with lowermost Cretaceous (Berriasian) cyclic carbonates. These Early Cretaceous emergence events were due to long term relative sea level fall, coupled with decreased subsidence rates. Thus the Late Tithonian appears to be a very warm greenhouse phase in the mid-Jurassic-Early Cretaceous cool mode. The Jurassic-Cretaceous sections of the Adriatic platform in Croatia may provide important paleoclimatic data for this time interval during which some of the world's major petroleum reservoirs were generated.