Platform environments, microfacies and systems tracts of the upper Cenomanian-lower Santonian of Sinai, Egypt

Summary Factors controlling grain composition and depositional environments of upper Cenomanian—Santonian limestones of Sinai are discussed. The mainly shallow-water, inner-platform setting investigated is subdivided into five major facies belts, each represented by several microfacies types (MFTs). Their lateral distribution patterns and their composition underline aclear relation between depositional environment and platform position. The facies belts include sandstones and quartzose packstones of siliciclastic shorefaces, mudstones and bioclastic wackestones of restricted lagoons, shallow-subtidal packstones with diverse benthic foraminifera and calcareous algae, bioclastic and/or oolitic grainstones of inner-platform shoals, and wackestones of deep open-marine environments. The microfacies distribution patterns of the Cenomanian-Santonian strata are evaluated with respect to local and regional large-scale environmental changes. While protected shallow-subtidal environments with only subordinate ooids and oncoids prevail during the late Cenomanian, high-energy oolithic shoals and carbonate sands occur locally during the middle and late Turonian. They were probably related to a change of the platform morphology and a reorganisation of the platform after a late Cenomanian drowning. In the Coniacian-Santonian, the lack of ooids, oncoids, and the decrease of calcareous algae versus an increase in siliciclastics indicate a shift to lower water temperature and to a more humid climate. Especially in the Turonian, the interplay between sea-level changes, accommodation, hydrodynamics, and siliciclastic input is reflected by lithofacies and biofacies interrelation-ships that are elaborated within individual systems tracts. In particular, increasing accommodation intensified circulation and wave-agitation and controlled the distribution of high-energy environments of the middle and upper Turonian trans-gressive systems tracts. During highstands protected innerplatform environments prevailed.     

Carbonate facies evolution from the late albian to Middle Cenomanian in Southern Istria (Croatia): influence of synsedimentary tectonics and extensive organic carbonate production

Summary During the Late Albian, Early and Middle Cenomanian in the NW part of the Adriatic Carbonate Platform (presentday Istria) specific depositional systems characterised by frequent lateral and vertical facies variations were established within a formerly homogeneous area, ranging from peritidal and barrier bars to the offshore-transition zone. In southern Istria this period is represented by the following succession: thin-bedded peritidal peloidal and stromatolitic limestones (Upper Albian); well-bedded foreshore to shoreface packstones/grainstones with synsedimentary dliding and slumping (Vraconian-lowermost Cenomanian); shoreface to off-shore storm-generated limestones (Lower Cenomanian); massive off-shore to shoreface carbonate sand bodies (Lower Cenomanian); prograding rudist bioclastic subaqueous dunes (Lower to Middle Cenomanian); rudist biostromes (Lower to Middle Cenomanian), and high-energy rudist and ostreid coquina beds within skeletal wackestones/packstones (Middle Cenomanian). Rapid changes of depositional systems near the Albian/Cenomanian transition in Istria are mainly the result of synsedimentary tectonics and the establishment of extensive rudist colonies producing enormous quantities of bioclastic material rather than the influence of eustatic changes. Tectonism is evidenced by the occurrence of sliding scars, slumps, small-scale synsedimentary faults and conspicuous bathymetric changes in formerly corresponding environments. Consequently, during the Early Cenomanian in the region of southern Istria, a deepening of the sedimentary environments occurred towards the SE, resulting in the establishment of a carbonate ramp system. Deeper parts of the ramp were below fair-weather wave base (FWWB), while the shallower parts were characterised by high-energy environments with extensive rudist colonies, and high organic production leading to the progradation of bioclastic subaqueous dunes. This resulted in numerous shallowing- and coarsening-upwards clinostratified sequences completely infilling formerly deeper environments, and the final re-establishment of the shallow-water environments over the entire area during the Middle Cenomanian.     

Facies evolution and sequence chronostratigraphy of a “mid”-Cretaceous shallow-water carbonate succession of the Apulia Carbonate Platform from the northern Murge area (Apulia,southern Italy)

The “mid”-Cretaceous carbonate succession of the Apulia Carbonate Platform cropping out in northern Murge area (Apulia, southern Italy) is composed of shallow-water carbonate rocks and is over 400 m in thickness. This paper focuses on the lithofacies analysis of this carbonate succession, its paleoenvironmental interpretation, and its sequence-chronostratigraphic architecture. Lithofacies analysis permitted to identify deposits which can be grouped into the following three facies belts: (1) terrestrial facies belt formed by: intraclast-supported paleosoils; solution-collapse breccias; (2) restricted facies belt made up of lithofacies deposited in protected peritidal environments; (3) normal-marine facies belt made up of lithofacies formed in moderate- to high-energy subtidal environments. The detailed study both in outcrops and in thin-sections revealed that, at the bed scale, lithofacies are cyclically arranged and form shallowing-upward small-scale depositional sequences comparable to parasequences and/or simple sequences. The following three small-scale sequence types have been distinguished: (1) subtidal sequences mostly made up of lithofacies formed in the normal-marine open subtidal domain; (2) peritidal sequences made up of lithofacies formed in the restricted peritidal domain; (3) peritidal sequences showing a cap formed by paleosoils. Small-scale sequences are not randomly arranged in the compiled succession but form discrete packages, or sets, that alternate in the sedimentary record. The repetition of such small-scale sequence packages in the succession has been the key to recognize large-scale sequences comparable to third-order depositional sequences. Although sedimentological data are often fragmentary due to late dolomitization, four large-scale sequences have been distinguished. The data support a generalized landward-backstepping of facies belts during transgression, which implies a gradual gain of accommodation culminating with the deposition of a package of small-scale sequences formed by normal-marine subtidal deposits. These mark periods of maximum accommodation space and form the maximum-flooding zones of large-scale sequences. A gradual seaward progradation of facies belts is recorded during highstand conditions, which implies a gradual loss of accommodation culminating with the deposition of a package of peritidal small-scale sequences capped by paleosoils or by solution-collapse breccias. The occurrence of terrestrial deposits marks periods of minimum accommodation on the platform and determines the sequence boundary of large-scale sequences. The large-scale sequences identified in this study fit with the main transgressive/regressive cycles published in the sequence-chronostratigraphic chart of European basins. As a consequence, it is interpreted that changes of the sea level recorded at the scale of European basins played an important role in determining the sequence-stratigraphic architecture of the studied succession. In spite of this, the occurrence of solution-collapse breccias, which implies a significant gap in carbonate sedimentation in between Early and Middle Cenomanian times, may also have an alternative interpretation. In particular, this deposit may represent the local fingerprint of the well-known tectonic phase which, during Late Albian-Early/Middle Cenomanian times, determined the subaerial exposure of large parts of Periadriatic carbonate platforms producing a marked regional unconformity.     

Depositional facies and cyclic patterns in a subtidal-dominated ramp during the Early-Middle Ordovician in the western Tarim Basin (NW China)

Due to a long-term transgression since the Early Cambrian, an extensive shallow-water carbonate platform was developed in the entire Tarim Basin (NW China). During the deposition of the Yingshan Formation (Early-Middle Ordovician), a carbonate ramp system was formed in the intrashelf basin in the Bachu-Keping area of the western basin. Four well-exposed outcrop sections were selected to investigate their depositional facies, cycles, and sequences, as well as the depositional evolution. Detailed facies analyses permit the recognition of three depositional facies associations, including peritidal, semi-restricted subtidal, and open-marine subtidal facies, and eleven types of lithofacies. These are vertically arranged into meter-scale, shallowing-upward peritidal, semi-restricted subtidal, and open-marine subtidal cycles, in the span of Milankovitch frequency bands, suggesting a dominant control of Earth’s orbital forcing on the cyclic sedimentation on the platform. On the basis of vertical facies (or lithofacies) and cycle stacking patterns, as well as accommodation changes illustrated graphically by Fischer plots at all studied sections, six third-order depositional sequences are recognized and consist of lower transgressive and upper regressive parts. In shallow depositional settings, the transgressive packages are dominated by thicker-than-average, shallow subtidal cycles, whereas the regressive parts are mainly represented by thinner-than-average, relatively shallow subtidal to peritidal cycles. In relatively deep environments, however, the transgressive and regressive successions display the opposite trends of cycle stacking patterns, i.e., thinner-than-average subtidal cycles of transgressive packages. Sequence boundaries are mainly characterized by laterally traceable, transitional zones without apparent subaerial exposure features. Good correlation of the long-term changes in accommodation space inferred from vertical facies and cycle stacking patterns with sea-level fluctuations elsewhere around the world suggests an overriding eustatic control on cycle origination, platform building-up and evolution during the Early-Middle Ordovician, although with localized influences of syndepositional faulting and depositional settings.     

Late Cretaceous sedimentary evolution of a northern sector of the Adriatic Carbonate Platform (Matarsko Podolje,SW Slovenia)

Cretaceous shallow-marine carbonate rocks of SW Slovenia were deposited in the northern part of the Adriatic Carbonate Platform. A 560-m-thick continuous Upper Cenomanian to Santonian carbonate succession has been studied near Hru?ica Village in Matarsko Podolje. With regard to lithological, sedimentological, and stratigraphical characteristics, the succession has been divided into nine lithostratigraphic units, mainly reflecting regressive and transgressive intervals of larger scale. During the latest Cenomanian and Early Turonian, hemipelagic limestones were deposited on top of shallow-marine lagoon and peritidal Upper Cenomanian deposits indicating relative sea-level rise. Subsequently, the deeper marine depositional setting was gradually filled by clinoform bioclastic sand bodies overlain by peritidal and shallow-marine low-energy mainly lagoonal lithofacies. Similar lithofacies of predominately inner ramp/shelf depositional settings prevail over the upper part (i.e., Coniacian to Santonian) of the succession. In the area, the Upper Cetaceous carbonate rocks are separated from the overlying Lower Eocene (Upper Paleocene?) carbonate sequence by regional unconformity denoted by distinct paleokarstic features. On the Adriatic Carbonate Platform the deeper marine carbonate setting, developed at the Cenomanian/Turonian boundary, is usually correlated with OAE2 and related eustatic sea-level rise. Similarly, subsequent reestablished shallow-marine conditions are related to Late Turonian long- and short-term sea-level fall. However, we are suggesting that deeper marine deposits were deposited in a tectonically induced intraplatform basin formed simultaneously with the uplift of the northern and northeastern marginal parts of the Adriatic Carbonate Platform.     

Microfacies and cycle stacking pattern in Liassic peritidal carbonate platform strata, Gavrovo-Tripolitza platform, Peloponnesus, Greece

Platform carbonate sediments of Liassic age cropping out in the area of the Pigadi-Fokianos Gulf (SE of Leonidion, Peloponnesus) have been investigated in order to determine their depositional environment. Facies analysis allowed the recognition of several microfacies types and their cyclic stacking pattern. The carbonates were deposited in a restricted inner platform environment (lagoon-peritidal domain) and are arranged into small-scale shallowing-upward cycles. Palaeosol horizons containing typical pedogenic features are developed on the top of the peritidal facies or are directly superimposed on subtidal deposits, forming diagenetic caps. This implies repeated sea-level fluctuations and periodic emersion episodes. The presence of orbitally forced cyclicity though is mostly probable, cannot be clearly documented by the available data. The studied carbonates are comparable with other coeval analogous peritidal cycles of the same age along the southern margin of the Tethys.     

Cherty carbonate facies of the Montoya Group, southern New Mexico and western Texas and its regional correlatives: a record of Late Ordovician paleoceanography on southern Laurentia

The Upper Ordovician Montoya Group in southern New Mexico and westernmost Texas records predominantly subtidal deposition on a gently dipping carbonate ramp that was subsequently nearly entirely dolomitized. The medial unit of the Montoya Group, the Aleman Formation is unique because it contains abundant chert (10–70% by volume). The chert occurs as: (1) thin continuous beds of sponge spicules within mudstone or calcisiltite; (2) discontinuous, lenses or nodules within skeletal wackestones and packstones; or (3) as a replacement of skeletal grains and burrows. Coeval skeletal grainstones and muddy peritidal facies contain little chert. Phosphate (up to 5 wt.%) occurs within the underlying Upham Formation and the Aleman Formation as replacement of fossils and peloids. The abundance of chert and phosphate in these subtidal facies indicates they formed within a region of strong upwelling. Regional correlation with Upper Ordovician cherty units along the periphery of southern Laurentia and other low latitude continents suggests that upwelling was widespread and long-lived during the Late Ordovician. The upwelling is interpreted to record vigorous oceanic circulation produced by the onset of glaciation on Gondwana during this period. Late Ordovician relative sea-level curves around the periphery of Laurentia indicate correlative third-order (1–3 my duration) fluctuations that may provide a means for high-resolution global correlations. However, the mechanism(s) that produced these long-term fluctuations are unclear.     

Facies stacking and extinctions across the Triassic–Jurassic boundary in a peritidal succession from western Sicily

An uppermost Triassic–lowermost Jurassic carbonate platform succession, which is 430 m thick, in northwestern Sicily is described with the aim to provide new data on the sedimentological and biological variations across the Triassic–Jurassic boundary in peritidal environments. The studied succession belonged to the rimmed carbonate shelf that developed during the Late Triassic along the margins of the Ionian Tethys. The peritidal sediments consist of meter-scale shallowing-upward cycles formed by subtidal, intertidal, and supratidal facies. Three main informal units are differentiated along the section on the basis of the variations recorded by the subtidal facies. The lower and middle units are attributed to the Rhaetian, on the basis of the common presence of the foraminifer Triasina hantkeni, associated with several benthic foraminifers, such as Aulotortus sinuosus and Auloconus permodiscoides. Megalodontids are particularly abundant and large in the lower unit, whereas they become rare in the middle unit and disappear in the upper unit. The last occurrence of T. hantkeni, along with the disappearance of the benthic foraminifer fauna, and the bloom of the calcareous alga Thaumatoporella parvovesiculifera is assumed as a proxy of the Rhaetian–Hettangian boundary. Recovery biota during the early Jurassic occurs about 20 m upward of the boundary zone, marked by the appearance of benthic foraminifers, such as Siphovalvulina sp. The observed biostratigraphic signature in the studied section is easily comparable to similar Tethyan sections already described from Italy, Greece, and Turkey; thus, it is believed that the faunistic turnover does not reflect local facies variations, in response to changes in the accommodation space of the platform, but regional changes in a more wide area of ocean Tethys.     

Recovery of carbonate platform production in the Lombardy Basin during the Anisian: paleoecological significance and constrain on paleogeographic evolution

In the Central Lombardy Basin (Southern Alps) Anisian carbonate platform marginal facies yielding the first documented occurrence of coral colonies in this area of the Western Tethys has been recognized. These marginal facies identify the east-west transition between two sectors with a different Anisian evolution. West of the recognized marginal facies the Anisian succession is characterised by subtidal bioturbated limestones passing upward to peritidal dolostones, whereas toward the east a thicker succession of subtidal facies persist until the end of the Anisian. The margin belt develops at the passage between a more subsiding eastern portion and a less subsiding one toward the west. The different facies and thickness of the Anisian succession east and west of the marginal facies is indicative of syndepositional tectonics. The transition from subtidal to peritidal facies in the western sector is ascribed to a sea-level fall that favoured the onsetting of peritidal facies on the less subsiding block and of marginal facies on its border. The occurrence of a N-S trending syndepositional Anisian fault system could also explain the scarce progradational evolution of the margin facies, prevented both by the paleobathymetric setting and by the scarce productivity of the Anisian marginal communities. The presence, in the Anisian marginal facies, of crinoids and corals (together with the occurrence of one of the oldest specimen of coralline red algae) outlines the return to normal marine conditions and documents the recovery of the carbonate platform marginal faunal association after the Permo-Triassic crisis in the Western Southern Alps.     

Cenomanian rudist-dominated shelf-margin limestones from the panormide carbonate platform (Sicily, Italy): Facies analysis and sequence stratigraphy

Summary Sedimentological, paleontological and sequence analyses of Cenomanian limestones in Sicily reveal the facies architecture and dynamics of a Mid Cretaceous rudistdominated platform margin from Western Tethys. The studied deposits outcrop near Palermo, as part of a large structural unit of the Sicilian Maghrebids. They belong to the Panormide carbonate platform, a Mesocenozoic paleogeographic domain of the African margin. The lateral continuity of the beds along three nearly parallel E-W outcrop sections allowed the recording of cm/dm thick lithological and faunal variations. Nine main lithofacies associations have been recognised along about 200 m of subvertical strata. Their vertical and lateral organisation points to a transition from highenergy shelf-margin rudist patches and shoals to more internal lagoonal-tidal environments over a short distance. The lithofacies evolution and stacking pattern along the three sections made it possible to define elementary cycles, composite cycles and larger-scale sequences with a dominant shallowing-upward trend. Their hierarchical organisation implies that sea-level fluctuations were an important factor in their formation. The cycles are characterised by a great variation in facies as a result of transgressive-regressive events in different sectors of the inferred Cenomanian shelf. Subtidal cycles typical of the shelf margin (4–10 m-thick) are particularly well identifiable. They are made of large Caprinidae and Sauvagesiac rudstone-to-floatstone (about 2/3 of the total thickness), capped by rudist-conglomerates, often organised into 3–5 fining-upward amalgamated beds and showing, in places, effects of surface-related diagenesis. In more internal shelf areas the cycles consist of Caprinidae-Radiolitidae floastone grading up into amalgamated beds of angular bioclastic rudstone/grainstone. Alternations of foraminifer/ostracod mudstone/wackestone and bioclastic grainstone/fine-rudstone, capped by loferites and/or by other emersion-related overprintings, characterise the cycles formed in the peritidal zones. these cycles are stacked into three incomplete depositional sequences. The sequence boundaries have been identified by the abrupt interposition of peritidal cycles in subtidal rudist-rich cycles, with evidence of brief subaerial exposure.     

Depositional environments and facies development of the Cenomanian–Turonian Galala and Maghra el Hadida formations of the Southern Galala Plateau (Upper Cretaceous,Eastern Desert,Egypt)

The Cenomanian–Turonian (Upper Cretaceous) Galala and Maghra el Hadida formations of the Southern Galala Plateau in Wadi Araba (northern Eastern Desert, Egypt) represent marine depositional systems developing in response to the early Late Cretaceous transgression at the southern margin of the Neotethyan Ocean in tropical paleolatitudes. A facies analysis (litho-, bio- and microfacies) of these successions shows the presence of 22 facies types (FTs, six are related to the Galala Formation, while the Maghra el Hadida Formation is represented by 16 FTs). The Galala Formation was deposited in a fully marine lagoonal environment developing in response to a latest Middle to early Late Cenomanian transgression. The rich suspension- and deposit-feeding macrobenthos of the Galala Formation indicate meso- to eutrophic (i.e., green water) conditions. The facies types of the uppermost Cenomanian–Turonian Maghra el Hadida Formation suggest deposition on a homoclinal carbonate ramp with sub-environments ranging from deep-subtidal basin to intertidal back-ramp. Major and rapid shifts in depositional environments, related to (relative) sea-level changes, occurred in the mid-Late Cenomanian, the Early–Middle Turonian boundary interval, the middle part of the Middle Turonian and the Middle–Late Turonian boundary interval.     

Continental, brackish and marine carbonates from the Lower Cretaceous of Kolone–Barbariga (Istria, Croatia): stratigraphy, sedimentology and geochemistry

During the Early Cretaceous, wide areas of the Dinaric–Adriatic Carbonate Platform emerged for long periods. The Hauterivian–Barremian carbonates from Kolone–Barbariga show a few typical examples of lacustrine facies with dinosaur bones and brackish/palustrine facies. The sequence of the platform is made for the most part by subtidal and intertidal limestones. The bone levels are located in a large depression few meters deep in the uppermost Hauterivian marine limestones. The filling facies of this depression are made by oncolitic rudstones and algal boundstones, which represent marginal lacustrine facies, and by laminated limestones, thin stromatolitic levels and distal fringes of rudstones which represent relatively open lacustrine facies. The fossil content is characterized by rare charophyte stems, ostracods, gastropods and plant remains, while typical marine fauna is absent. At the Hauterivian–Barremian boundary a major emersion event has been observed, then a slow transgressive phase occurred. The transgressive facies are primarily made by mudstones with ostracods, charophytes and Spirillina (brackish and probably freshwater facies), wackestones with Ophtalmidiidae and rare dasyclad algae, storm layers with gastropods and miliolids and breccia-like dinoturbated beds. Wackstones, packstones and very rich in dasyclad grainstones outcrop at the top of the section, representing the maximum of the transgression. Trace elements content, carbon and oxygen stable isotope analyses have been performed to aid the palaeoenvironmental interpretation. In this geological setting, Barium seems to discriminate between brackish and freshwater facies. The isotopic values of the marine carbonates appear to depend on early diagenetic processes, meanwhile lacustrine facies seem to show a weak signal of the depositional environment.     

Benthic foraminiferal assemblages of the Cretaceous platform carbonate succession in the Yavca area (Bolkar Mountains, S Turkey): biostratigraphy and paleoenvironments

The microbiostratigraphic analysis of the three outcrop sections from the Cretaceous inner platform carbonate succession in the Yavca area (Bolkar Mountains) allows to recognize the four local benthic foraminiferal zones. These are: (1) Voloshinoides murgensis and Praechrysalidina infracretacea Cenozone in the Lower Aptian; (2) Pseudorhapydionina dubia and Biconcava bentori Cenozone in the Middle-Upper Cenomanian; (3) Ostracoda and Miliolidae Interval Zone in the probable Turonian, represented by dolomitized limestones without any significant markers; (4) Moncharmontia compressa and Dicyclina schlumbergeri Cenozone in the Coniacian-Santonian. The benthic foraminiferal assemblages correspond to those in other areas of the Mediterranean realm, with the exception of a lack of alveolinids and orbitolinids due to unfavorable environmental conditions (inner platform, restricted shelf). After the regionally well-known emergence during the late Aptian, Albian and early Cenomanian, very shallow subtidal to intertidal conditions were re-established during the middle-late Cenomanian time. The Coniacian-Santonian benthic foraminiferal assemblage shows an increase in diversity and abundance as a result of open marine influence, confirmed by the presence of larger foraminifera (Dicyclina), Rotaliidae and radiolitid fragments. Thaumatoporella and Aeolisaccus-bearing wackestone intercalations still indicate the existence of sporadic restricted environment conditions. The Cretaceous shallow-water platform carbonate succession of the Yavca area is conformably overlain by gray pelagic limestones with calcispheres and planktonic foraminifera. The Campanian flooding of the Bolkar Da? carbonate platform resulted in drowning of the pre-existing biota and facies.     

Facies pattern and sea-level dynamics of the early Late Cretaceous transgression: a case study from the lower Danubian Cretaceous Group (Bavaria,southern Germany)

The facies development and onlap pattern of the lower Danubian Cretaceous Group (Bavaria, southern Germany) have been evaluated based on detailed logging, subdivision, and correlation of four key sections using an integrated stratigraphic approach as well as litho-, bio-, and microfacies analyses. Contrary to statements in the literature, the transgressive onlap of the Regensburg Formation started in the Regensburg–Kelheim area already in the early Early Cenomanian Mantelliceras mantelli ammonite Zone and not in the Late Cenomanian. In the Early Cenomanian, nearshore glauconitic-bioclastic sandstones prevailed (Saal Member), followed by Middle to lower Upper Cenomanian mid-shelf siliceous carbonates intercalated with fine-sandy to silty marls (Bad Abbach Member). Starting in the mid-Late Cenomanian (Metoicoceras geslinianum ammonite Zone), a considerable deepening pulse during the Cenomanian–Turonian Boundary Event (CTBE) initiated the deposition of the deeper shelf silty marls of the Eibrunn Formation, which range into the early Early Turonian. During the CTBE transgression, also the proximal Bodenwöhrer Senke (ca. 40 km NE of Regensburg) was flooded, indicated by the onlap of the Regensburg Formation onto Variscan granites of the Bohemian Massif, overlain by a thin tongue of lowermost Turonian Eibrunn Formation. A detailed record of the positive δ¹³C excursion of the global Oceanic Anoxic Event (OAE) 2 has been retrieved from this shallow-water setting. An integrated approach of bio-, event-, carbon stable isotope and sequence stratigraphy was applied to correlate the sections and to decipher the dynamics of this overall transgressive depositional system. The Cenomanian successions show five prominent unconformities, which correlate with those being known from basins in Europe and elsewhere, indicating their eustatic origin. The rate of sea-level rise during the CTBE suggests glacio-eustasy as a driving mechanism for Late Cenomanian sea-level changes. The Regensburg and Eibrunn formations of the lower Danubian Cretaceous Group are highly diachronous lithostratigraphic units. Their regional distribution and northeast-directed onlap pattern onto the southwestern margin of the Bohemian Massif can readily be explained by the lateral movements of roughly coast-parallel (i.e., NW/SE-trending) facies belts of a graded shelf system transgressing on a northeastward-rising substrate. It took the Cenomanian coastline ca. 6 Ma to transgress from southwest of Regensburg to the topographically elevated granite cliffs southeast of Roding in the Bodenwöhrer Senke (=60 km distance).     

Late Cenomanian–Early Turonian facies development and sea-level changes in the Bodenwöhrer Senke (Danubian Cretaceous Group, Bavaria, Germany)

The Upper Cenomanian–Lower Turonian litho-stratigraphic units of the Danubian Cretaceous Group of the proximal Bodenwöhrer Senke (Regensburg, Eibrunn and Winzerberg formations, the latter consisting of a lower Reinhausen Member and an upper Knollensand Member), have been investigated with a focus on facies analysis and sequence stratigraphy. Analyses of litho-, bio-, and microfacies resulted in the recognition of 12 predominantly marine facies types for the Eibrunn and Winzerberg formations. Petrographic and paleontological properties as well as gradual transitions in the sections suggest that their depositional environment was a texturally graded, predominantly siliciclastic, storm-dominated shelf. The muddy–siliceous facies types FT 1–3 have been deposited below the storm wave-base in an outer shelf setting. Mid-shelf deposits are represented by fine- to medium-grained, bioturbated, partly glauconitic sandstones (FT 4–6). Coarse-grained, gravelly and/or shell-bearing sandstones (FT 7–10) developed in the inner shelf zone. Highly immature, arkosic coarse-grained sandstones and conglomerates (FT 11 and 12) characterize an incised, high-gradient braided river system. The Winzerberg Formation with its general coarsening- and thickening-upward trend reflects a regressive cycle culminating in a subaerial unconformity associated with a coarse-grained, gravelly unit of marine to fluvial origin known as the “Hornsand” which is demonstrably diachronous. The overlying Altenkreith Member of the Roding Formation signifies the onset of a new transgressive cycle in the early Middle Turonian. The sequence stratigraphic analysis suggests that the deposition of the Upper Cenomanian and Lower Turonian strata of the Bodenwöhrer Senke took place in a single cycle of third-order eustatic sea-level change between the major sequence boundaries SB Ce 5 (mid-Late Cenomanian) and SB Tu 1 (Early–Middle Turonian boundary interval). The southeastern part of the Bodenwöhrer Senke was flooded in the mid-Late Cenomanian (Praeactinocamax plenus transgression) and a second transgressive event occurred in the earliest Turonian. In the central and northwestern parts of the Bodenwöhrer Senke, however, the initial transgression occurred during the earliest Turonian, related to pre-transgression topography. Thus, the Regensburg and Eibrunn formations are increasingly condensed here and cannot be separated anymore. Following an earliest Turonian maximum flooding, the Lower Turonian Winzerberg Formation filled the available accommodation space, explaining its constant thickness of 35–40 m across the Bodenwöhrer Senke and excluding tectonic activity during this interval. Rapid sea-level fall at SB Tu 1 terminated this depositional sequence. This study shows that Late Cenomanian–Early Turonian deposition in the Bodenwöhrer Senke was governed by eustatic sea-level changes.     

Lithostratigraphy and facies development of upper cretaceous carbonates in east central Sinai,Egypt

Summary The Upper Cretaceous exposures in east central Sinai are represented by carbonate-dominated successions interbedding few sandstone, chert, shale and marl horizons. The recognised rock units are correlated with their counterparts commonly used in the Gulf of Suez region and central Sinai including from base to top: the Raha Formation, Abu Qada Formation, Wata Formation, Matulla Formation and the Sudr Chalk. Twelve limestone microfacies are encountered and are categorised as mudstones (pelmicrite and ostracod micrite), wackestones (pelagic biomicrite and foraminiferal biomicrite), grainstones (foraminiferal biopelsparite and oosparite), boundstones (bindstone and framestone), floatstones (coated-grained biomicrudite, rudist biomicrudite and shelly biomicrudite) and rudstones (shelly biosparudite). The dolostone microfacies include fine-medium crystalline ostracod dolostones and shelly dolostones. These microfacies have been compared with the Standard Microfacies Types and their depositional environments are discussed. The encountered litho- and biofacies suggest that the Cenomanian shallow transgressive sea had covered east central Sinai as far south as the Dahab region. By the advent of the Turonian, open marine subtidal conditions prevailed. This was followed by transitional conditions with shoals and tidal bars in the Late Turonian pointing to a regressive phase more pronounced at the southern localities. The rocks of the Matulla Formation were deposited in an oscillating environment of shallow subtidal to intertidal conditions during Coniacian-Santonian. In the Late Santonian and during most of the Campanian-Maastrichtian, sedimentation was influenced by open marine conditions with low sedimentation rates; local shallow subtidal regressive events occurred.     

Microfacies and paleoenvironment of the Wadi Sir Formation (Upper Cretaceous), North Jordan

The Wadi Sir Formation (the “Massive Limestone”) is divided into five distinct microfacies-types. They are from top to bottom: Globigerinid mudstones, bioclastic grainstones, miliolid packstones, peloidal packstones and pure mudstones. During the Turonian restricted lagoonal environments dominated except toward the end of the period, where open-shelf conditions prevailed.     

Quantitative analysis of accommodation patterns in carbonate platforms: an example from the mid-Cretaceous of SE Spain

For sequence stratigraphic analysis of extensive carbonate platforms (hundreds of kilometres wide) developed in greenhouse climates on broad, passive margins, less emphasis should be placed on large-scale seismic geometries, and more attention paid to sequence stratigraphic correlation of stratigraphic sections based usually on isolated outcrops. To this end, quantitative analysis of accommodation emerges as a simple, useful tool, that allows detailed architectural reconstructions, regional chronostratigraphical correlation and systems tract interpretation. In this paper, a quantitative analysis of accommodation was applied to the wide platforms that developed in the southern passive continental margin of Iberia during the mid-Cretaceous (late Albian to early middle Cenomanian interval). This analysis was based on several integrated techniques including: (1) construction of total accommodation curves with the aid of backstripping techniques for calculating decompacted sedimentary accumulation through time, (2) mathematical analysis of these curves and characterisation of second- and third-order accommodation patterns, and (3) analysis of parasequence stacking patterns in peritidal cyclic successions by means of Fischer plots. By applying these techniques to eight individual sections logged at the decimetre scale in outcrops of the External Zones of the Betic orogenic belt, it was possible to characterise the second- and third-order accommodation signal for this interval in the basin. The second-order curve defines a long-term sigmoidal pattern of nearly six million years, with low rates of accommodation generation in the first and the last part of the interval, and high rates in the mid-interval. The third-order signal defines six accommodation events of one million years average duration, which controlled the development of six successive depositional sequences and their systems tracts. On the basis of this new sequence stratigraphic framework, a high-resolution, 2-D platform transect, showing the spatial distribution of facies, was erected and analysed. The results notably complete previous qualitative sequence stratigraphic data on the platform and contribute to a better understanding of the nature of systems tracts and their boundaries in response to overlapping of second- and third-order accommodation patterns.     

The Cenomanian–Turonian boundary in Jordan: Ammonite biostratigraphy and faunal turnover

Well-exposed fossiliferous Upper Cenomanian–Lower Turonian marine sedimentary rocks are present in west-central Jordan. Ammonites serve as an important faunal marker for this interval and can be used to subdivide the Cenomanian–Turonian transition into two upper Cenomanian biozones (Neolobites vibrayeanus and Vascoceras cauvini) and two lower Turonian biozones (Vascoceras proprium and Choffaticeras segne). A revised stratigraphic range of the Vascoceras cauvini Zone in the study area is proposed, consisting of the Metoicoceras geslinianum and Neocardioceras juddii zones of the standard zonation. Based on intercontinental biostratigraphic correlation, a minor unconformity appears to be present around the Cenomanian–Turonian boundary, and a part of the lower Turonian is probably missing. In addition, a faunal turnover is recorded in the uppermost Cenomanian, marked by the disappearance of most of the Cenomanian taxa, including Costagyra olisiponensis (Sharpe), Ceratostreon flabellatum (Goldfuss), Ilymatogyra africana (Lamarck), Rhynchostreon suborbiculatum (Lamarck), Harpagodes nodosus (Sowerby), and Heterodiadema libycum (Desor). This bioevent is thought to be an effect of the Oceanic Anoxic Event OAE 2; the dramatic shifts in species richness and diversity spanning the Cenomanian–Turonian boundary in the study area occurred in response to the major paleoclimatic and paleoenvironmental perturbations prevailing at that time. The stratigraphic and paleontological patterns studied in Jordan are very similar to those recorded in Egypt in terms of litho- and biostratigraphy, event stratigraphy, and macroinvertebrate content, suggesting the presence of uniform triggering mechanisms and bio-sedimentary responses in the Upper Cretaceous basins of the Middle East and providing clues for a high-resolution correlation between the two areas.     

Late paleozoic and Late Triassic limestones from north Palawan Block (Philippines): Microfacies and paleogeographical implications

Summary Selected Late Paleozoic and Triassic limestone exposures were studied on northern Palawan Island, Philippines, with regard to microfacies, stratigraphy and facies interpretation. Although some of the outcrops were already reported in literature, we present the first detailed microfacies study. Late Paleozoic carbonates in the El Nido area are represented by widley distributed Permian and locally very restricted Carbonifenous limestones. Of particular interest is the first report of Carboniferous limestones in the Philippines dated by fossils. Fusulinids indicate a ‘Middle’ Carboniferous (Moscovian-Kasimovian) age of the Paglugaban Formation only known from Paglugaban Island. The Permian Minilog Formation consists mostly of fusulinid wackestones and dasycladacean wacke-/packstones. Fusulinid datings (neoschwagerinids and verbeekinids) provide a Guadalupian (Wordian-Capitanian) age. The depositional setting of the Middle Permian carbonates corresponds to a distally steepened ramp with biostromes built by alatoconchid bivalves locally associated with richthofeniid brachiopods. Late Triassic limestones occur in isolated exposures on and around Busuanga Island (Calamian Islands). The age of the investigated carbonates is Rhaetian based on the occurrence ofTriasina hantkent Maizon. Microfacies data indicate the existence of reefs (Malajon Island) and carbonate platforms (Kalampisanan Islands, Busuanga Island, Coron Island). Reef boundstones are characterized by abundant solenoporacean red algae, coralline sponges and corals. Platform carbonates yield a broad spectrum of microfacies types, predominantly wacke- and packstones with abundant involutinid foraminifera and some calcareous algae. These facies types correspond to platform carbonates known from other parts of Southeast Asia (Eastern Sulawesi and Banda Basin; Malay Peninsula and Malay Basin). The Philippine platform carbonates were deposited on and around seamounts surrounded by deeper water radiolarian cherts. The new data on facies and age of the Philippine Permian and Triassic carbonates contradict a close paleogeographical connection between the North Palawan Block and South China and arise problems for the currently proposed origin of the North Palawan Block at the paleomargin of South China. We hypothesize that North Palawan was part of the Indochina Block during the Carboniferous and Permian, separated from the Indochina Block during the Middle Permian and collided with the South China Block in the Late Cretaceous.