Shallowing-upward Cycles Research Articles

Anatomy of a cyclically packaged Mesoproterozoic carbonate ramp in northern Canada

Carbonates in the upper member of the Mesoproterozoic Victor Bay Formation are dominated by lime mud and packaged in cycles of 20–50 m. These thicknesses exceed those of classic shallowing-upward cycles by almost a factor of 10. Stratigraphic and sedimentological evidence suggests high-amplitude, high-frequency glacio-eustatic cyclicity, and thus a cool global climate ca. 1.2 Ga. The Victor Bay ramp is one of several late Proterozoic carbonate platforms where the proportions of lime mud, carbonate grains, and microbialites are more typical of younger Phanerozoic successions which followed the global waning of stromatolites. Facies distribution in the study area is compatible with deposition on a low-energy, microtidal, distally steepened ramp. Outer-ramp facies are hemipelagic lime mudstone, shale, carbonaceous rhythmite, and debrites. Mid-ramp facies are molar-tooth limestone tempestite with microspar-intraclast lags. In a marine environment where stromatolitic and oolitic facies were otherwise rare, large stromatolitic reefs developed at the mid-ramp, coeval with inner-ramp facies of microspar grainstone, intertidal dolomitic microbial laminite, and supratidal evaporitic red shale. Deep-subtidal, outer-ramp cycles occur in the southwestern part of the study area. Black dolomitic shale at the base is overlain by ribbon, nodular, and carbonaceous carbonate facies, all of which exhibit signs of synsedimentary disruption. Cycles in the northeast are shallow-subtidal and peritidal in character. Shallow-subtidal cycles consist of basal deep-water facies, and an upper layer of subtidal molar-tooth limestone tempestite interbedded with microspar calcarenite facies. Peritidal cycles are identical to shallow-subtidal cycles except that they contain a cap of dolomitic tidal-flat microbial laminite, and rarely of red shale sabkha facies or of sandy polymictic conglomerate. A transect along the wall of a valley extending 8.5 km perpendicular to depositional strike reveals progradation of inner-ramp tidal flats over outer- and mid-ramp facies during shoaling. The maximum basinward progradation of peritidal facies coincides with a zone of slope failure that may have promoted the development of the stromatolitic reefs. The sea-level history of the Victor Bay Formation is represented by three hectometre-scale sequences. An initial flooding event resulted in deposition of the lower Victor Bay shale member. Upper-member carbonate cycles were then deposited during highstand. Mid-ramp slumping was followed by late-highstand reef development. The second sequence began with development of an inner-ramp lowstand unconformity and a thick mid-ramp lowstand wedge. A second transgression promoted a more modest phase of reef development at the mid-ramp and shallow-water deposition continued inboard. A third and final transgressive episode eventually led to flooding of the backstepping ramp. Overall consistent cycle thickness and absence of truncated cycles, as well as the high rate and amount of creation of accommodation space, suggest that the periodicity and amplitude of sea-level fluctuation were relatively uniform, and point to a eustatic rather than tectonic mechanism of relative sea-level change. High-amplitude, high-frequency eustatic sea-level change is characteristic of icehouse worlds in which short-term, large-scale sea-level fluctuations accompany rapidly changing ice volumes affected by Milankovitch orbital forcing. Packaging of cyclic Upper Victor Bay carbonates therefore supports the hypothesis of a late Mesoproterozoic glacial period, as proposed by previous workers.

Burrows and body fossil of decapod crustaceans in the Calcari Grigi, lower Jurassic, Trento platform (Italy)

Crustacean burrows are largely known and well described in the literature but a concurrence of abundant burrows and fossil remains of decapods represents an exceptional circumstance in the geological record. Well-preserved burrows of decapod crustaceans in the Pliensbachian of the Trento carbonate platform, northern Italy, reveal several ichnoassemblages of Thalassinoides and Ophiomorpha from 2 to 16 cm in diameter forming complex burrow systems in the lagoonal facies of the Rotzo Member. These burrows have been found both in the lower surface of beds and within shallowing-upwards cycles of fossiliferous limestones (Lithiotis facies), which reveal peculiar taphonomic characteristics. The abundant concentration of decapod crustacean burrows suggests intense burrowing activity of such organisms during the Early Jurassic as indicated also by an exuvia of Phlyctisoma (Erymidae), although we do not know if it was an active tracemaker. Many shallowing-upward parasequences occur and burrow systems were concentrated mainly in their lower part suggesting intense biological activity in deeper and quiet subtidal conditions; conversely, biologic activity was interactive with physical agents in the middle part of cycles and progressively replaced by wave or tidal-induced physical agents in the upper part where intertidal/supratidal conditions were formed.

Characterization of the Mississippian chat in south-central Kansas

To understand production from low resistivity-high porosity Mississippian chat reservoirs in south-central Kansas it is necessary to understand the nature of deposition and diagenesis, how tectonics is a factor, the lithofacies controls on petrophysical properties, and log response to these properties. The initial mudstones to sponge-spicule wacke-packstones were deposited in transgressive-regressive (T-R) cycles on a shelf to shelf margin setting, resulting in a series of shallowing-upward cycles. Sponge-spicule content appears to increase upward with increasing cycle thickness. After early silicification, inter- and post-Mississippian subaerial exposure resulted in further diagenesis, including sponge-spicule dissolution, vuggy porosity development in moldic-rich rocks, and autobrecciation. Meteoric water infiltration is limited in depth below the exposure surface and in distance downdip into unaltered, cherty Cowley Formation facies. Areas of thicker preserved chat and increased diagenesis can be correlated with structural lineaments and, in some areas, with recurrent basement block movement. Combination of folding or block fault movement prior to or during development of the basal Pennsylvanian unconformity, sponge-spicule concentration, and possibly thickness of overlying bioclastic wacke-grainstones resulted in variable reservoir properties and the creation of pods of production separated by nonproductive cherty dolomite mudstones. These events also resulted in alteration of the depositional cycles to produce a series of lithofacies that exhibit unique petrophysical properties. From bottom to top in a complete cycle seven lithofacies are present: (1) argillaceous dolomite mudstone, (2) argillaceous dolomite mudstone that has chert nodules, (3) clean dolomite mudstone that has nodular chert, (4) nodular to bedded chert, (5) autoclastic chert, (6) autoclastic chert that has clay infill, and (7) bioclastic wacke-grainstone. The uppermost cycle was terminated by another lithofacies, a chert conglomerate of Mississippian and/or Pennsylvanian age. The chert facies exhibit porosities ranging from 25 to 50% and permeabilities greater than 5 md. The (Begin page 86) cherty dolomite mudstones, argillaceous dolomite mudstones, and bioclastic wacke-grainstones exhibit nonreservoir properties. Reservoir production, numerical simulation, and whole core data indicate fracturing can be present in chat reservoirs and can enhance permeability by as much as an order of magnitude. Capillary pressure data indicate the presence of microporosity and can explain high water saturations and low resistivity observed in wire-line logs. Relative permeabilities to oil decrease rapidly for saturations greater than 60% and may be influenced by dual pore systems. Archie cementation exponents increase from 1.8 for mudstones to more than 2.5 in the cherts that have increasing sponge-spicule mold and vug content. Detailed modified Pickett plot analysis of logs reveals critical aspects of chat character and can provide reliable indices of reservoir properties and pay delineation. Models developed provide additional insight into the chat of south-central Kansas and understanding of the nature of controls on shallow-shelf chert reservoir properties.

Lithostratigraphic and facies analyses of the Sarcheshmeh Formation (Lower Cretaceous) in the eastern Kopet Dagh Basin, NE Iran

The Kopet Dagh Basin is located in north-east Iran where sedimentation continued throughout the Jurassic–Tertiary. The area studied is in the easternmost part of the basin. Two stratigraphic sections representing mainly the Lower Aptian Sarcheshmeh Formation have been measured. The Sarcheshmeh Formation in one of these sections (Mozduran) is about 200m thick. It thins towards the other section (Baghak) in easternmost part of the basin where it about 150m thick. It is conformably overlain by the Sanganeh Formation and underlain by the Tirgan Formation. Four different facies have been recognized; pelmicrite, mudstone–micritic limestone, biomicrite–bio-oomicrite and biosparite–oosparite. They reflect deposition on a carbonate ramp. Many small-scale shallowing-upward cycles (parasequences) have also been identified within transgressive and high stand system tracts. The cyclicity was probably related to subsidence, which in turn was related to both sediment loading and tectonics.

Jurassic radiolarites in a Tethyan continental margin (Subbetic, southern Spain): palaeobathymetric and biostratigraphic considerations

A region of the pelagic Subbetic basin within the Southern Iberian Continental Margin is studied in lithostratigraphical and biostratigraphical detail. Jurassic radiolarites (Jarropa Radiolarite Formation, Bathonian–Oxfordian) interbedded with shallow-water marine limestones have been recognized. Underlying the radiolarites (Camarena Formation, Bajocian) are oolitic limestones showing shallowing-upward cycles with karstic surfaces on the top, corresponding to deposition on an isolated carbonate platform on volcanic edifices. The Milanos Formation (upper Kimmeridgian–Tithonian), overlying the radiolarites, contains calciclastic strata with hummocky cross-stratification, which indicate outer carbonate ramp deposition. In the Jarropa Radiolarite Formation some calcisiltite strata with hummocky cross-stratification have been found. The bathymetry of the Subbetic Jurassic pelagic sediments, including the radiolarites, is considered as moderate or shallow in depth. We suggest that the pelagic character of the Jurassic sediments in this margin and their equivalents in other Alpine domains is a consequence of distance from the continent (beyond the pericontinental platform) but not necessarily of depositional depth.

Taphonomy of trace fossils at omission surfaces (Middle Triassic, East Germany)

In shallowing-upward cycles of the East German (Thuringian) Muschelkalk (Middle Triassic), sedimentological (probably storm) events interrupted longer periods of low net-sedimentation. The ichnofauna changed with the diagenesis of the substrate; it does not represent an ecological succession. The presence of both firmground and hardground traces in the same samples indicates superimposed Trypanites and Glossifungites ichnofacies. The ichnofabric of burrows was `frozen' by cementation during omission, the amount of erosion controlling the preservation of the upper tiers (borings). In general, both burrowing and boring has been intense but patchy, and recruitment of tracemakers had been almost monospecific. A hostile environment, perhaps due to high salinity and/or erosion, may thus be assumed. The type of preservation was governed by different reactions to sulphide production in different chemical microenvironments during early diagenesis. In absence of significant amounts of iron, H 2S escaped into burrows or borings from the adjacent anaerobic sediment. Depending on local physicochemistry, this resulted in calcite or pyrite precipitation. Well-aerated parts of burrows facilitated the formation of celestite after reoxidation of sulphide. On goethite-encrusted hardgrounds, pyrite rings were formed around numerous borings, trapping the active H 2S immediately after its formation. These haloes were previously mistaken as excrements.

Abstract: Sequence Stratigraphic Significance of Meter-Scale Shallowing-Upward Cycles, Wapanucka Formation (Morrowan), Oklahoma 

Abstract: Sequence Stratigraphic Significance of Meter-Scale Shallowing-Upward Cycles, Wapanucka Formation (Morrowan), Oklahoma 

The relationship between glacio-eustatic parasequences and a third-order sequence in the Kakegawa Group, central Japan

The Plio–Pleistocene Kakegawa Group, central Japan, consists of a third-order depositional sequence (2.6–1.0 Ma). The northwestern part of the Kakegawa sequence consists of up to 500 m of alluvial, shoreface, shelf, slope and submarine-channel facies. It contains at least sixteen upward-shallowing cycles (parasequences), the deposition of which was affected by high-frequency eustatic sea-level cycles. The lower part of the sequence is characterized by a retrogradational parasequence set, which formed a transgressive systems tract (2.2–1.75 Ma) followed by a progradational parasequence set comprising a highstand systems tract (1.75–1.4 Ma). Subsidence analysis and evaluation of changes in the shelf sedimentation rate estimated from cross-sections, suggest that formation of the third-order sequence was controlled by tectonic subsidence and variation in the sedimentation rate. Rapid subsidence and a high rate of sedimentation during 2.2–2.0 Ma resulted in deposition of the lower part of the transgressive systems tract, characterized by thick backstepping successions. The rate of subsidence decreased in the period 2.0–1.75 Ma. The sedimentation rate also decreased due to a high rate of sediment bypassing. However, subsidence was still the dominant factor, leading to the formation of thin backstepping successions. The 1.75–1.4 Ma progradational succession resulted from a combination of a low rate of subsidence and moderate sedimentation. The progradational units become thicker basinward owing to faster subsidence in the basin center. The maximum flooding surface was formed around 1.75 Ma even though subsidence was slow at this time.

Shallowing-upward cycles in pelagic troughs (Upper Jurassic, Subbetic, Southern Spain)

Abundant calcareous tempestites with chert and hummocky cross-stratification (HCS) occur in Upper Jurassic successions (Milanos Formation) of the Subbetic (Betic Cordillera, Southern Spain). These calcareous tempestite beds are calcisiltites and very fine calcarenites with peloids and bioclasts, and have thicknesses between 25 and 75 cm. Beds show symmetrical wave ripple lamination near the top, and are usually capped with wave ripples. According to palaeogeographic reconstructions, these strata were deposited in a subsiding trough in the pelagic domain of the Southern Iberian Continental Margin, which was the northwestern-most border of the Tethys. Calcisiltite and calcarenite beds deposited in this pelagic trough form small-scale to large-scale shallowing-upward cycles. Shallowing-upward cycles with calcareous tempestites in the lower part and oolitic limestone beds in the upper part, have also been recognized in some sectors of the Subbetic pelagic basin. The large-scale cycle occurs in the upper part of the Jarropa Radiolarite Formation, which directly underlies upper Oxfordian, Kimmeridgian and Tithonian strata of the Milanos Formation. Two types of large-scale shallowing-upward cycles have been recognized, according to the presence or absence of thick units of oolitic limestone with large-scale cross-stratification. The water depth during deposition ranged from below, but near, storm wave base at the base of the large-scale cycles to very shallow carbonate platform at the top.

Origin and modification of early dolomites in cyclic shallow platform carbonates, Yeongheung Formation (middle Ordovician), Korea

The middle Ordovician Yeongheung Formation, Korea, consists of numerous metre-scale, shallowing-upward cycles, which were deposited on a shallow-marine carbonate platform. Depositional sequences developed on the inner platform were completely dolomitized regardless of constituting lithology, whereas those developed on the outer platform were partially dolomitized. The amount of replacement dolomite within a metre-scale, shallowing-upward peritidal cycle decreases downward from the peritidal cycle cap in the partially dolomitized depositional sequences. The cross-platform distribution of dolomites and their stratigraphic position in the sequences suggest that the Yeongheung dolomite formed syndepositionally. The common existence of pseudomorphs of evaporite minerals and nodules in the Yeongheung Formation indicates that dolomitization of the Yeongheung Formation occurred in a sabkha-type tidal-flat environment. It also occurred during each cycle of deposition influenced by high-frequency sea-level oscillations. The present-day Yeongheung replacement dolomites are characterized by near-stoichiometric to stoichiometric composition (49.9 to 52.1 CaCO 3 mole%), and low strontium concentration (52 to 133 ppm). The δ 18O value of the replacement dolomites ranges from −7.7 to −5.2‰ (PDB); this is much depleted relative to that of contemporary sabkha-type dolomites. These geochemical characteristics of Yeongheung dolomite indicate significant post-depositional modification. The common existence of oomolds, leached skeletal grains and dissolved evaporites in the Yeongheung Formation illustrates invasion of meteoric water into the sediments. Recrystallization of Yeongheung dolomites in the infiltrated meteoric water at slightly elevated temperatures during shallow burial resulted in lighter δ 18O values and lower strontium concentration.

Ordovician metre-scale cycles: implications for climate and eustatic fluctuations in the central Appalachians during a global greenhouse, non-glacial to glacial transition

Abstract Metre-scale shallowing-upward cycles in Ordovician carbonates of the central Appalachian Basin record climate and eustatic fluctuations during a transition from Early Ordovician global greenhouse to Late Ordovician icehouse conditions. Peritidal facies and shale abundance suggest a long-term trend in this area from semi-arid (Early Ordovician) to more humid (Middle to early Late Ordovician) conditions, with a return to semi-arid conditions during the Late Ordovician. The climatic fluctuations were most likely produced by tectonics (uplift and erosion) related to Taconic orogenesis, plate motion of North America and the areal extent of water covering the shelf. Peritidal cyclic facies indicate that high-frequency relative sea level fluctuations were of small amplitude ( 20 m) relative sea-level fluctuations that decreased into the later Ordovician. If these sea-level changes are eustatic, then the increased amplitude may mark the early initiation of continental glaciation on Gondwana in the late Middle Ordovician, followed by waning of ice sheets prior to the latest Ordovician glaciation.

Stacking patterns and correlation of meter-scale shallowing-upward cycles in the Lower Ordovician carbonates in Pingquan and Qinglongshan, North China.

Stacking patterns and correlation of meter-scale shallowing-upward cycles in the Lower Ordovician carbonates in Pingquan and Qinglongshan, North China.

Sequence Sequence stratigraphy, sea-level changes and depositional systems in the Cambro-Ordovician of the North China carbonate platform

The Cambro-Ordovician strata in North China were deposited over a very extensive craton, extending some 1500 km east-west and 1000 km north-south. The dominantly shallow-water carbonate succession reaches up to 2000 m in thickness and two megasequences (transgressive-regressive cycles) can be distinguished: Lower Cambrian through Lower Ordovician strata, and Middle through Upper Ordovician strata, separated by a major palaeokarst. The first megasequence consists of nine sequences which are generally 50-150 m in thickness. The Lower Cambrian sediments consist of phosphorites and phosphatic sandstones, deposited during the flooding of the craton. Carbonates, mudrocks and evaporites were deposited in the Early Cambrian under an arid climate, laying the foundation for the subsequent long period of shallow-water carbonate deposition which lasted some 70 m.y. The Middle and lower Upper Cambrian sequences consist predominantly of mudrocks and storm deposits (‘tempestites’) in the lower part and oolitic grainstones and tidal-flat lime mudstones in the upper part; these represent outer-mid and mid-inner-ramp depositional systems, respectively, of the transgressive and highstand systems tracts. These sequences have strong similarities with the ‘Grand Cycles’ in the Cambro-Ordovician successions of North America. In the Upper Cambrian, there is a distinctive unit of glauconitic purple-red mudstone several metres thick which is interpreted as the deposits of the maximum flooding of the first megasequence. In the Upper Cambrian, there was a phase of tilting of the North China Carbonate Platform to the north, and storm deposits, especially intraclastic conglomerates and hummocky cross-stratified grainstones-packstones, were very common at this time. Also common in upper Middle and lower Upper Cambrian strata are stromatolitic-thrombolitic bioherms, several metres in diameter. The upper Upper Cambrian through Lower Ordovician strata are dominantly fine-grained limestones and dolomites deposited in shallow-subtidal and inter- to supra-tidal environments on a low-energy epeiric-sea platform. This part of the succession is the regressive part of the first megasequence, so that overall the platform shows an evolution from platform initiation to platform foundation, to a ramp-depositional system and then an extensive epeiric platform. On a small scale, the succession is composed of metre-scale shallowing-upward cycles (parasequences) arranged into cycle sets of 10–30 m thick. The Middle-Upper Ordovician megasequence consists mostly of shallow-water carbonates with several thick evaporite units. Minor palaeokarsts and palaeosoils separate the sequences, which are composed of metre-scale cycles. Regional uplift affected the North China Platform in the Ordovician and sedimentation did not resume until the Carboniferous. There is a good correlation of the two transgressive-regressive megasequences described here with the global 2nd-order relative sea-level curve for the Cambro-Ordovician.

Cycle stacking pattern, diagenesis and reservoir geology of peritidal dolostones, Trigonodus-Dolomite, Upper Muschelkalk (Middle Triassic, SW-Germany)

Peritidal dolostones (Trigonodus-Dolomite) characterize the back-bank environment of the Upper Muschelkalk (Middle Triassic) carbonate ramp of SW-Germany. These deposits represent the Late Highstand Systems Tract (HST) of the ‘Third-Order’ Middle to Upper Muschelkalk depositional sequence. The HST forms an overall shallowing-upward trend and is build by a progradational stack of 1–2 m thick shallowing-upward cycles. The latter vary from subtidal-to-intertidal cycles at the base of the investigated section to intertidal-to-supratidal cycles at the top of the section.

Depositional cyclicity of the Middle Ordovician Yeongheung Formation, Korea

The Middle Ordovician Yeongheung Formation consists of numerous meter-scale, shallowing-upward cycles, which were deposited on a shallow-marine carbonate platform. Two types of shallowing-upward cycles, peritidal and shallow subtidal cycles, are recognized in the Yeongheung Formation. The peritidal cycles are composed of shallow subtidal lithofacies capped by tidal-flat lithofacies, whereas the shallow subtidal cycles are entirely subtidal lithofacies with no tidal-flat caps or subaerial exposure features. Stacking of shallow subtidal cycles, the similtaneous development of peritidal and subtidal cycles on different parts of the carbonate platform, and persistent vertical stacking of meter-scale, shallowing-upward cycles suggest that most of the cycles were formed in response to high-frequency eustatic sea level oscillations.

Facies sequences of the middle-upper jurassic carbonate platform (Amran Group) in the Sana'a region, Republic of Yemen

Rocks of the Amran Group in the Sana'a region of Yemen disconformably overlie the Kohlan Formation and unconformably underlie the Tawilah Group. Sea-level rises have produced landward migration of facies belts and the development of deeper water facies over shallow ones. The geometry of the depositional environments identified has enabled the passage of relatively short-lived transgressive-regressive cycles of sedimentation to be recognized. Three facies associations are introduced: (1) Carbonate platform facies, (2) Carbonate-marl alternation facies, and (3) Shallow water coral and stromatoporoid build-up facies. These facies are widely distributed and the whole sequence reflects deposition on a broad platform upon which shoals separated platform carbonates from basin sedimentation and an open marine environment. The repetition and interfingering of both fining- and shallowing-upward cycles within the study areas suggest that deposition occurred within the same basin with slightly different conditions in different places. The main factors controlling their deposition are sea-level changes and tectonics.

Cycle anatomy and variability in the storm-dominated type cincinnatian (Upper Ordovician): coming to grips with cycle delineation and genesis.

Although parasequence and sequence are scale-independent terms, they are frequently applied only to specific scales of cycles. For example, meter-scale cycles are commonly assumed to be parasequences or PACs. In the Upper Ordovician Kope and Fairview Formations of northern Kentucky, we examined a succession of 50 meter-scale cycles that have been variously interpreted as deepening-upward, shallowing-upward, or showing no relationship with water depth. Our analysis shows that these cycles, characterized by shifts in storm-bed proximality, are highly variable in their thickness and internal construction. Most cycles are best considered high-frequency sequences, because deepening-upward intervals are common, and many cycles contain evidence of abrupt basinward shifts in facies as expected at sequence boundaries. A minority fit the parasequence model of shallowing-upward cycles bounded by flooding surfaces. Larger, 20 m scale cycles are defined by systematic thickening and thinning trends of meter-scale cycles. However, meter-scale cycles do not display any systematic trends in cycle anatomy as a function of position within the 20 m cycles or position within the Kope and Fairview Formations. The high cycle variability and the lack of systematic stratigraphic organization with respect to longer-term cyclicity reflect either the irregularity of relative sea-level changes, the poor recording of sea-level changes in this deep-water setting, or the generation of these cycles by climate-induced cyclicity in storm intensity. These three mechanisms would generate similar patterns at the outcrop scale, so it is not possible at the present to distinguish between them.

Autogenic dynamics in carbonate sedimentation; meter-scale, shallowing-upward cycles, Upper Cambrian, western Newfoundland, Canada

Autogenic dynamics in carbonate sedimentation; meter-scale, shallowing-upward cycles, Upper Cambrian, western Newfoundland, Canada

Early ordovician microbial reef mounds of the tribes Hill formation, Mohawk Valley, New York

Tribes Hill domal thrombolites, termed here microbial reef mounds, occupied the basal part of meter-scale shallowing-upward cycles. They are part of a high-energy facies that a sharp, transgressive surface, separates from an underlying low-energy peritidal setting. This erosional surface served as the surface on which one of the reef mounds established itself during initial transgression before further deepening. The others overlie a floor of skeletal grainstone reflecting a high-stand sea-level facies tract. Skeletal grainstone composes the fill between the mounds. One channel and several aggrading hummocks occupy inter-reef mound areas resulting from storm events in a subtidal setting.

Cycle Stacking and Long-Term Sea-Level History in the Lower Cretaceous (Gavrovo Platform, NW Greece)

ABSTRACT The stacking pattern of peritidal shallowing-upward cycles of a continuously exposed Barremian to upper Albian section from an isolated carbonate platform in the Gavrovo-Tripolitza Zone (NW Greece) has been analyzed. The 541 m thick succession is located in an intraplatform setting with an overall mud-dominated facies development. It comprises 252 peritidal cycles, which show a systematic increase in cycle thickness from the Barremian to Albian. Comparison of the cycle stacking pattern of the section, which spans 35 m.y., and several published curves of long-term eustatic sea-level history show striking similarities. Comparison of cycle stacking pattern in Greece with a time-equivalent section measured near Potrero Garcia in Mexico suggests preservation of similar trends in Fischer pl ts in the two areas even though a difference in mean cycle thickness indicates different rates of subsidence in Greece and Mexico. This implies that the shallow-water carbonates of the Gavrovo platform are recording second-order eustatic sea-level variations. Closely spaced samples throughout the section allow evaluation of the degree of early diagenetic alteration of depositional facies within the shallowing-upward cycles. The degree of vadose diagenetic overprinting of intertidal and subtidal facies and multiple overprinting of individual cycles support a predominantly allocydic control of deposition by low-amplitude, high-frequency sea-level fluctuations during Early Cretaceous greenhouse climate. However, expected time gaps of different lengths in the succession during sea-level lows ands may bias the direct translation of cycle stacking pattern into third-order sea-level curves.