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High Resolution Sequence Stratigraphy of the Upper Ordovician Red River "B" Reservoir, Williston Basin, North Dakota, USA

Aptian carbonate sequences of a cooler phase within Cretaceous greenhouse, Adriatic platform, Croatia

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

Ovaj list prikazuje geološku građu, odnosno prostorni raspored, stratigrafske i tektonske odnose te temeljnu paleontologiju i petrologiju 18 litostratigrafskih jedinica različite geološke starosti (kreda, paleogen, i kvartar) središnjeg dijela otoka Cresa. List je izrađen prema pisanom geološkom standardu (Upute za izradu Osnovne geološke karte Republike Hrvatske mjerila 1:50 000), u okviru projekta od strateškog nacionalnog interesa.

Sequence and Carbon Isotope Stratigraphy from the Aptian carbonate platform interior, southern Croatia

Facies and Porosity-Permeability Relationship in Red River A and B Intervals, North Dakota

Petrographic composition and carbonate mineralogy of modern subtidal sediments from two subtropical lagoons, San Salvador isolated platform, Bahamas

Sedimentary facies architecture of the Upper Ordovician Red River Formation, North Dakota

Sequence Stratigraphic Framework, Trace Element and Stable Isotope Geochemistry of the Late Ordovician Red River Formation, Williston Basin, North Dakota

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

Cyclostratigraphy of Upper Albian tropical platform-interior carbonate facies, Korcula Island, 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.

Sedimentary and carbon isotope record from the Aptian carbonate platform, Croatia

Calcareous algae of the Late Ordovician Red River Formation and their biostratigraphic significance

Microfacies and Porosity of the Late Ordovician Red River A and B Intervals in Central North Dakota

Core and Log‐Based Carbonate‐Evaporite Depositional Sequence Analysis, Late Ordovician Upper Red River Formation, Western North Dakota

Carbonate-evaporite facies in the „B“ interval of the Upper Ordovician Red River Formation, Williston Basin, North Dakota

Karbonatna platforma Bahama (Great Bahama Bank) široko je poznata kao recentni ekvivalent karbonatnih platformi iz geološke povijesti. Istraživanja su se fokusirala na vapnenačke alge, posebno dazikladalne, njihovu raznovrsnost, životne okoliše, utjecaj na stvaranje karbonatnih sedimenata, kao i na usporedbu s fosilnim zajednicama rasprostranjenima u karbonatnim naslagama hrvatskih Dinarida.

Bioturbated-carbonate-capped parasequences: a key to short term climate/sea level change on carbonate platforms controlled by climate and plant and animal bioturbation

Carbon chemostratigraphy and depositional sequences of the Late Ordovician Katian Red River Formation, North Dakota

Late Valanginian to Early Barremian peritidal facies of the Adriatic platform, Croatia: Evidence of subaerial exposure

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

Late Valanginian to Late Hauterivian Peritidal and Subaerial Exposure Facies, Adriatic Platform, Croatia

Analysis of carbonate-evaporite facies and depositional environments in the „B“ interval of the Upper Ordovician Red River Formation, Williston Basin, North Dakota

Carbonate platform signature of greenhouse worlds

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

Small scale parasquences characterize carbonate platforms from the Late Archean to Holocene. These cycles are bound by marine flooding surfaces. On shallow platforms shallowing upward regressive, peritidal parasequences are common. Thin transgressive lags form during transgressions when deepening water (sedimentation less than accommodation) may be tied to submarine erosion, bypass and lag time/or depth, followed by accumulation of regressive subtidal to peritidal sediments under stable or falling relative sea level, and possible subaerial erosion updip. Cycles are capped by barren muds, tidal flat facies and subaerial exposure surfaces, and evaporites in arid settings. Rapid deepening to deeper subtidal depths, followed by upward shallowing to storm or fair weather wave base as sea level falls on outboard of low and mid-latitude platforms in deeper water, commonly causes regressive coarsening up parasequences of carbonate muds, interbedded muds and sands, grainy tops, capped by marine erosion surfaces. Transgressive and transgressive-regressive parasequences are common on some platform interiors (e.g. Triassic). Here sea level rise just outpaces sedimentation rate, and low energy and insufficient bioturbation prevent removal of the deepening upward section so a marked transgressive record is preserved, often capped by a paleosol if sea level fall is rapid enough or the peritidal cap is stripped by erosion. On low-latitude greenhouse platforms this transgressive part of a cycle may also contain beaches of ooids, sublittoral sand sheets, and even hypersaline ponds of the platform interior. On deeper parts of low-latitude platforms, deepening and fining upwards parasequences may form on the deep ramp or within intrashelf basins, near storm wave-base. Cycles typically start with a sharp basal contact, overlain by high energy grainstone grading up through packstone, wackestone to mudstone, capped by the next truncation surface. These are deeper ramp, symmetrical transgressive-regressive cycles whose regressive cap has been stripped by marine erosion when sea level is lowered. Deepening upwards, but upwards coarsening parasequences occur in mid-latitude epeiric ramps within low energy embayments and estuaries bordering swell wave dominated shelves. The cycles have low energy muddy lower parts and deepen up into high energy open marine skeletal grainstones deposited near the wave abrasion depth.

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 240-meter-thick Late Valanginian to Late Hauterivian roadcut section on Mljet Island, Croatia was deposited in a tectonically stable Adriatic carbonate platform interior. The Valanginian is dominated by massive to very-thick-bedded cream, coarse sucrosic dolomudstone. This subtidal facies locally contains scattered gastropod molds and/or interbeds of gastropod-mold dolowackestone-mudstone to floatstone ; non-dolomitized gastropod-algal wackestone-mudstone is very rare. Peritidal laminites are rare ; fine-scale faint lamination in coarse sucrosic dolomite is fenestral and planar. Shallowing-upward dolomudstone-to-laminite parasequences are infrequently capped by few-centimeter-thick reworked intraclast, paleosol-like layers. The Hauterivian is dominated by well developed subtidal cycles with basal rooted horizons and mainly fenestral laminite caps suggesting humid subtidal to emergent conditions. The most common facies is peloid lime mudstone-wackestone to floatstone with branching, up to 1-cm-wide root burrows ; some horizons are heavily root-disrupted with green dolomitized shale fills, or completely dolomitized and represented by olive-gray, root-disrupted sucrosic dolomudstone. This facies also contains gastropods, clams, benthic foraminifera and calcareous algae, as well as pockets of peloid packstone ; clams and gastropods are locally leached and molds are filled with green shale. Root-disrupted horizons sporadically exhibit highly irregular and karstified tops with incipient breccia composed of granule-to-pebble-size angular clasts in lime mudstone matrix or dolomitized green shaly interstices. Laminated facies (upper intertidal to supratidal) commonly overlies rooted horizons and is distinguishable by fenestral peloid packstone and mudstone, frequently with sharp tops. Locally, fenestral laminites are transgressive ; they overlie rooted horizons with karstified tops and grade up into massive, rooted mudstone-wackestone. Transgressive, deepening parts of subtidal cycles are less frequently characterized by transgressive lags of microbial-lump and pisoid wackestone-packstone to floatstone, and thin dark-colored, broken-and-rehealed coarse ooid rudstone.

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.

San Salvador Island is a small isolated carbonate platform in the Bahamas archipelago. The island is composed of a thin veneer of Pleistocene and Holocene carbonate rocks, predominantly eolianites overlying thick succession of Mesozoic and Tertiary limestones and dolomites. A large area of the island is covered by mostly hypersaline lakes that formed in depressions between the dune ridges. San Salvador is surrounded by barrier reefs with protected lagoons behind them. Sea-water temperature ranges from 24 to 30 oC. The study focuses on modern calcareous algae, particularly Dasycladales, from the paleontologist’ s perspective, in order to better understand their present contribution to carbonate sediments, as well as to compare these algae with their possible fossil counterparts. Investigated localities are include: Long Lake, Fernardez Bay (Telephone Pole Reef), French Bay, Pigeon Creek, Rice Bay and Graham’ s Harbor (North Point and Dump reef). Calcareous algae have been found in diverse environments. The most common are Halimeda and Penicillus. They are widespread, especially in protected lagoons with soft bottom, in both barren and grass-covered areas. They can be also found on patch reefs, in tidal channels and near beaches just below the low-tide level. Other green algae are also common, as Rhipocephalus, Udotea and Avrainvillea. Dasycladales are much less common then Bryopsidales. Among them the most common species is Batophora occidentalis. Relatively common are Acetabularia crenulata and Dasycladus vermicularis. Calcified species Cymopolia barbata and Neomeris annulata are very rare. All of the observed Dasycladales live attached to hard substrate (rock, corals, pebbles, shell fragments) and occur in bushes composed of several individuals. Batophora has been found in lagoon environment, but mostly near beaches, commonly in small pools between callianassid mounds. It also occurs on mangrove roots above low tide level, implying tolerance to temporary desiccation. Acetabularia has been found in the same environment as Batophora, but not above sea level. Dasycladus has been found in hypersaline lake. Cymopolia has been found near shore, where it swings with waves, firmly attached to the substratum. Calcification types vary among different algae. Some algae (Halimeda, Neomeris, Cymopolia) form distinct calcareous skeletons that they use for protection against predators. Postmortem disintegration of these skeletons leads to formation of sand-to-mud-size carbonate sediments. Other algae (Penicillus, Avrainvillea, Rhipocephalus, Udotea, Padina) precipitate small aragonite crystals that aggregate on the surface of the alga and between filaments. Young algae are therefore green, being whiter as aragonite precipitates. Following death, the aragonite envelope breaks down forming mud-size particles. Acetabularia form very thin aragonite envelope that also disintegrates into mud-sized particles, but genetically is closer to the first type of calcification. Non-calcified dasyclads Batophora and Dasycladus act as bafflers, collecting sand and mud-sized particles. The amount of sediment that they baffle is small compared to sea-grasses, but in the geological past, before the appearance of sea-grasses, the non-calcified algae likely were the main sediment-bafflers, although they haven’ t been preserved as fossils. Contribution of Bryopsidales to modern carbonate sediments is well known. Our investigations support previous data on exceptional importance of calcareous algae in formation of sand-to-mud-size carbonate particles. Since the scarcity of calcified Dasycladales prevents an estimation of their contribution to carbonate sediments, living Halimedaceans can be used as their analogues. In Mesozoic and Paleozoic times, when Dasycladales were much more abundant then Bryopsidales, their role in production of carbonates was probably significant.

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 Cambro-Ordovician Theresa Formation of northeastern New York has yielded an association of peritidal facies characterized by a poor body fossil assemblage but rich biogenic structures. Road-cut stratigraphy is complicated due to the patchy character of exposed sections, but a characteristic vertical sediment sequence could be recognized. The Theresa is characterized by a distinctive alternating sequence of grey, intensely bioturbated, poorly sorted calcareous sandstone and white quartz sandstone. Bioturbated facies of the grey calcareous sandstone contains a Cruziana ichnofacies of abundant deposit feeders. Scolithos ichnofacies is present in the white cross-bedded sandstone. The white sandstone in the upper Theresa is also characterized by wave ripples, herring-bone cross-stratification and horizontal lamination. The microbial structures distinguished by wavy laminated stromatolite growth structures are common in the white quartz sandstones of the middle Theresa. Vertical sections of stromatolites exhibit predominantly space-linked hemispheroids with close-linked hemispheroids as a microstructure in the constituent laminae. Hemispheroids vary both in amplitude and in shape, i.e. from low-amplitude (5-10 cm) and gently convex, to higher-amplitude (up to 20 cm), steeply convex to slightly rectangular, vertically stacked hemispheroids. Subcircular, concentrically stacked spheroids up to 30 cm in diameter, with laminae composed of close-linked hemispheroids are observed in plan view. The facies stacking pattern observed within the microbial structure-rich part of the Theresa Formation likely represents shallowing-upward parasequences composed of grey, intensely bioturbated, restricted subtidal facies, capped by microbial laminites of tidal flats. Some parasequences are capped by thin breccia-conglomerate horizons suggesting periodic subaerial exposure of tidal flats. The alternating vertical stacking pattern of the two facies is complicated by their common interfingering in the upper Theresa, suggesting facies mosaics.

Drill core within the Potsdam Group near Ellenburg, New York provides further insight into the depositional environments that existed prior to blanketing of the area by subarkosic to quartz arenites of the Ausable Formation. Three of the four cores taken within a few hundred meters of one another show variable lithologies ranging from thin (1-2 cm or less) hematitic, clay-rich mudstones, and siltstones, sandstones, pebbly granulestones, and upward fining conglomerates. A fourth core is dominated by a prominent 10 m thick layer(s) of hematitic, mud-supported conglomerate interpreted as the distal portion of debris flow(s). This core has abundant and dispersed, vertical water-escape pathways as shown by differences in color and texture defining discrete zones where fines were washed out. Major and trace element and petrographic analysis provide insight into the source of the sedimentary deposits. Silica ranges from 42.29-69.38%, whereas most other major elements, aside from MgO and CaO (carbonate alteration), fall within tight ranges (e.g. K2O = 5.3 – 8.94% ; Na2O = 0.41-0.78%). Most trace elements also fall into narrow ranges, except those dominated by resistant heavy minerals like zircon (Zr = 319.7-1265.0 ppm and Hf = 8.1-33.1 ppm). Rare earth elements yield consistent patterns generally 2-3x UCC abundances but depleted slightly in the LREEs. These patterns match nearby Precambrian basement rocks (Lyon Mountain Gneiss - LMG). Numerous, large grains of perthitic feldspar and large zircon grains, with cores and metamorphic rims characteristic of the LMG, document the likely source of the sequence. Samples with the highest amount of silica and largest grain-size closely match the geochemistry of the LMG, suggesting little dilution by other sources, minimal alteration, and rapid burial. These observations expand the inventory of depositional environments found at the base of the Potsdam sandstone to include debris flows, and strengthen paleogeographic models for an Adirondack source shedding sediment derived from fault scarps to the south (present coordinates) into the Ottawa Embayment. Stratigraphically these rocks may be similar to coarse clastics sporadically exposed at the base of the Hannawa Falls Member of the Ausable Formation, or proximal equivalents to the newly defined basal Jericho Member (B. V. Sanford, dissertation, Ottawa University, 2006).

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.

The mid-Cretaceous shallow-marine platform-interior deposits of southern Croatia are dominated by dasycladalean algae and benthic foraminifera. These deposits have been intensively biostratigraphically studied and major effort of micropaleontologists has been directed toward a description of the pattern of distribution of these two groups of microorganisms, not toward understanding of where and how they lived. The present study discusses the stratigraphical position and taxon richness of the main genera and species of dasycladalean algae within the Berriasian-Early Cenomanian interval. Several species of dasycladalean algae are of great value to the mid-Cretaceosu biostratigraphy of the Adriatic platform in southern Croatia. These species have restricted stratigraphical ranges, evolving rapidly and becoming extinct suddenly. They are also abundant and have a widespread distribution. These include: Salpingoporella melitae RADOIČIĆ and S. muehlbergii (LORENZ) (Barremian), and Salpingoporella turgida (RADOIČIĆ) and Cylindroporella taurica CONRAD & VAROL (Upper Albian).

Whole, broken and recoated radial calcite ooids occur in the Upper Jurassic platform interior carbonates (Adriatic platform, Croatia). The oolitic units also contain “ grapestone-like” aggregates, peloids and a restricted biota of gastropods and dasyclad algae. Ooids commonly have cerebroid outlines with radial structure, and lesser concentric micrite envelopes. The cortex contains numerous dark micron-sized inclusions of possible organic material that under SEM resemble microbial filaments and dissolved aragonite laths. Coatings show little evidence of abrasion of radial crystal terminations nor is there much rounding of broken ooids. Some units have superimposed fenestral fabric and many ooids are linked by micritic meniscus bridges. Dark color, platform interior setting, very restricted biotas and lack of high-energy sedimentary structures indicate that ooids were formed in hypersaline settings, similar to those in low-energy lakes, and marginal ponds and lagoons.

Well exposed Late Jurassic sections (over 750 m thick, approximately 5 to 6 m.y. duration) of the Bahama-sized Adriatic platform along the Dalmatian coast, southern Croatia, have well developed parasequences dominated by shallow subtidal to peritidal facies. These include dasyclad-oncoid mudstone-wackestone-floatstone (shallow lagoon), skeletal-peloid wackestone-packstone (very 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). Oversized, whole, broken and recoated radial ooids that form distinctive units resemble ooids of modern, low energy lake and marginal marine ponds. Their common position at bases of parasequences indicates formation during initial inundation of supratidal flats, along the shores of shallow hypersaline ponds and restricted lagoons of the platform interior. The abundance of these distinctive ooid facies in the Tithonian of Tethys may be due to arid climate, high calcite saturation state of platform waters, and the flat-topped, platform-interior morphology. The Tithonian parasequences appear to be less than 20 k.y. average duration and likely were formed by small sea-level changes driven by precessional forcing. During long-term (2.5 m.y.) sea-level rise, predominantly subtidal cycles were deposited, whereas peritidal cycles developed on the long-term (2.5 m.y.) sea-level fall. Evidence of an eccentricity signal in the parasequence bundling is relatively weak and produced parasequence sets whose component facies become successively more restricted upward. Paleosols are conspicuously absent from the Tithonian, suggesting that relative sea-level falls driven by precession were suppressed by high accommodation rates (12 to 15 cm/k.y.). The parasequence stacking patterns strongly suggest that the Tithonian likely was a time of hot global greenhouse during the postulated Middle Jurassic to Early Cretaceous "cool" mode.

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.

The Tithonian carbonates of the southern part of the Adriatic Platform are more than 700 meters thick, and have an accumulation rate of up to 15 cm/k.y. during a time of relatively uniform subsidence. The platform interior consists of numerous shallowing upward parasequences 1 to 3 meters thick. Facies include dasyclad and oncoid wackestone, skeletal packstone-grainstone, lime mudstone, and microbial and fenestral laminites. Late Tithonian parasequences commonly contain radial-ooid grainstone that occurs at transgressive bases of parasequences, or less commonly, in upper regressive parts of parasequences. Fischer plots are a simple graphical method to define relative sea level changes on "cyclic" carbonate platforms, by graphing cumulative departure from mean cycle thickness (corrected for subsidence) as a function of time. The preliminary plots of the Late Jurassic data suggest that the Fischer plots are effective in extracting 3rd order accommodation cycles from the data, but there is only a weak 4th order (100 and 400 k.y. signal) evident. The accommodation plots measure the combined effects of sea-level plus subsidence. Accommodation (Fischer) plots of the Late Jurassic cyclic succession show four 3rd order accommodation events (0.5 to 5 m.y. long). Differences between the plots for the Adriatic Platform, the Arabian Platform and the Haq and Al-Qahtani (2005) curve may in part be due to the effects of local tectonics. A combination of spectral analysis of time series constructed using some measure of relative water depth plotted against stratigraphic thickness, plot of cycle thickness vs. cycle number, and Fischer plots are being used to examine the possible influence of Milankovitch forcing on the formation of the platform interior cycles.

The Mesozoic, Barremian-Aptian deposits of southern Croatia comprise a succession of shallow tropical-water, inner platform deposits that formed on a Bahama-type isolated platform in the Dinarides. This succession is dominated by benthic foraminifera and calcareous algae, and is exposed in a nearly continuous outcrop section on the island of Mljet, southern Croatia. It has been studied in terms of biostratigraphy, paleoecology and sedimentary facies. The analysis of the microfossil association has provided a detailed biostratigraphic zonation based on the stratigraphic distribution of either benthic foraminifera or calcareous algae. The present study, calibrated against the standard regional biostratigraphic zonation for the Eastern Adriatic Lower Cretaceous, documents that several species of benthic foraminifera and calcareous algae have exceptional age-diagnostic value for the Early Cretaceous biostratigraphy. These Barremian calcareous algae species Salpingoporella melitae and S. muehlbergii, and Early Aptian benthic foraminifera Palorbitolina lenticularis and Voloshinoides murgensis are abundant, have a widespread distribution and a restricted stratigraphic range. They evolved rapidly and became extinct suddenly. The carbonate platform, because of its isolated position within the Late Mesozoic Tethyan Ocean, was free of terrigenous influences. The region was also tectonically quiet during most of the Early Cretaceous. Consequently, benthic distribution within oligotrophic habitats of the study area was primarily controlled by sea-level oscillations, variations in oceanic circulation rate and nutrient availability in surface waters. This study shows that Early Cretaceous diversification of benthic foraminifera in the area investigated, follows the regional relative sea-level curve for that period and the major foraminiferal turnovers coincide with sea-level rise and fall. During relative sea-level rises associated with reduced oceanic circulation and the expansion of nutrient-poor, shallow tropical waters, organisms were able to diversify into various euphotic habitats within the shallow subtidal platform interior. Regressive episodes resulted in reduction of oligotrophic habitats and decreased species richness.

The immense, several kilometers thick Bahama-type carbonate platform of the Dinarides was initiated in the Permo-Triassic as a portion of a land-attached Tethyan platform. It developed into the Jurassic-Cretaceous isolated platform following breakup of the Adria microcontinent. Well exposed Mesozoic sections along the Dalmatian coast (S Croatia) reveal the detailed stacking patterns of facies within the Late Jurassic (Tithonian) shallow platform interior (over 700 m thick). Facies include deeper lagoon dasyclad wackestone, oncoid wackestone, shoal-water skeletal packstone and grainstone, restricted lagoon lime mudstone, tidal flat microbial laminites and fenestral carbonates, and transgressive, periodically emergent radial-ooid grainstone. Sections consist of 40-60 meter thick parasequence sets roughly 400 ky duration based on long-term accumulation rates. Lower Tithonian sets are dominated by thick subtidal parasequences passing up into thin, more shallow water parasequences. Upper Tithonian sets also have thick subtidal parasequences in lower parts passing up into thin muddy peritidal parasequences with oolitic bases and microbial laminite caps. Roughly 10-15 parasequences make up the 400 ky parasequence sets suggesting incompletely recorded obliquity-precessional forcing. Emergence near the Jurassic/Cretaceous boundary formed extensive sequence-bounding subaerial clayey limestone breccia horizons interstratified with lowermost Cretaceous (Berriasian) cyclic carbonates. The striking 400 ky packaging in the Late Jurassic has also been observed in the Early Cretaceous elsewhere by others, and ascribed to presence of some polar ice. The Jurassic-Cretaceous sections of the Dinaric platform in Croatia may provide important paleoclimatic data for this time interval during which some of the world's major petroleum reservoirs were generated.

Otok Vis čini prostranu antiformnu strukturu, pravca pružanja istok – zapad. U području Komiškog zaljeva u krilima nalazimo slijed naslaga kredne starosti, koji je u tektonskom (dijapirskom) kontaktu s trijaskim vulkanogeno-sedimentno-evaporitnim kompleksom u jezgri. Detaljni litostratigrafski stupovi snimljeni su kroz kredne plitkomorske karbonate duž zapadnih obala otoka Visa. Analizom lito- i biostratigrafskih podataka prikupljenih tijekom snimanja i obrade stupova dobiven je jasan uvid u stratigrafiju, te su izdvojene neformalne jedinice koje odgovaraju formacijama i članovima. Neke jedinice litološki i stratigrafskim položajem odgovaraju ranije izdvojenim jedinicama na širem području, pa su neformalni nazivi tih jedinica preuzeti iz ranijih radova. Najstarije naslage karbonatnog slijeda čine neokomski dolomiti peritajdalnih obilježja. Monotoni slijed peritajdalnih ciklusa metarskih debljina prekinut je u donjem aptu izmjenom nekoliko litotipova vapnenaca istaloženih u uvjetima izražene paleookolišne dinamike. Sljedeći markantni horizont nalazi se u gornjem dijelu albskih naslaga, a obilježavaju ga orbitolinidno-radiolitidna litosoma i decimetarski horizonti laporovitog materijala, koji odgovaraju stratigrafskoj razini tzv. “ kvarcnih pijesaka“ . Ponovni izostanak peritajdalnih ciklusa s naznakama otvorenije cirkulacije obilježava početak gornjocenomansko– ?donjoturonske jedinice koju čine masivni i nodularni vapnenci s većim ili manjim udjelom bioklasta školjkaša, debeloljušturastih radiolitida i kaprinida. Pojava fenestralnih madstona s vrlo oskudnim fosilnim sadržajem, a naviše i brojnih eolisakusa, obilježava početak najmlađe turonsko– ?konijačke kredne jedinice na otoku Visu.

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.