Relative Sea-level Fluctuations Research Articles

Pedogenesis of late Quaternary deposits, northern Kyonggi Bay, Korea: Implications for relative sea-level change and regional stratigraphic correlation

Late Pleistocene and early Holocene paleosols are described from construction pits and boreholes in the northern Kyonggi Bay, west coast of Korea. Thin-section petrography, chemistry, clay mineralogy and geotechnical properties of the paleosols were examined to infer relative sea-level fluctuations during the late Quaternary. Relict laminae and gradational contacts with underlying tidal rhythmites confirm that the late Pleistocene paleosol is a pedogenically altered tidal deposit. Illuvial clay coatings, rootlets and enrichment of kaolinite and chemically stable oxides indicate that pedogenesis occurred on a well-drained, stable surface during the last glacial period. Redoximorphic features, such as drab-colored root traces and sphaerosiderite, however, suggest that waterlogged conditions developed temporarily due to a rise of the water table at the end of the last glacial period. As sea level rose, an early Holocene paleosol formed in freshwater bog deposits, burying the late Pleistocene paleosol. The early Holocene paleosol has abundant sphaerosiderites and organic material. The presence of weakly developed illuvial clay coatings, oxidized siderites and pellets, however, indicates oxidizing condition associated with water-table fall occurred during the early Holocene. Despite the similarity in the degree of chemical and clay mineralogical weathering, the late Pleistocene paleosol is distinguished from its early Holocene counterpart by thicker and more abundant illuvial clay coatings, more Fe 2O 3 and a greater degree of consolidation. Duration of pedogenesis might be a primary cause for the difference of the pedofeatures with climate playing a secondary role. The widespread presence of similar late Pleistocene paleosols highlights its significance as a key stratigraphic marker for regional correlations along the west coast of Korea.

Distribution of sedimentary organic matter in Anisian carbonate series of S Poland: evidence of third-order sea-level fluctuations

The stratigraphic distribution of sedimentary organic matter in Anisian carbonate series of southern Poland is studied with respect to relative sea-level fluctuations. Palynofacies patterns clearly reflect transgressive–regressive trends that are interpreted in terms of third-order cyclicity. Major flooding phases are detected by maximum abundance of marine plankton in the upper Bithynian and Pelsonian. Transgressive and highstand deposits are recognized by changes in the terrestrial input of organic particles and the relative percentages and diversity of the plankton group. The palynological data support the sequence stratigraphic interpretation based on sedimentological features and geochemical signatures. The corresponding eustatic signals of sedimentary and organic facies are discussed. The study highlights the potential of palynofacies analysis for sequence stratigraphical interpretation.

Coral zonation of an Oxfordian reef tract in the northern French Jura

During the Middle Oxfordian, numerous coral reefs flourished on the northern margin of the Tethys Ocean. The outcrop of Bonnevaux-le-Prieure (northern French Jura mountains) provides a rare opportunity to observe a nearly complete section allowing the installation, evolution and demise of this global carbonate reef rich event to be studied. Quantitative data on coral assemblages together with sedimentological and palaeoecological observations lead to the reconstruction of a reef tract coral zonation. Starting from the outer slope, Dimorpharaea, Microsolena, Dendraraea, Comoseris, and Stylina ecozones are recognized. This new facies model implies a central position for an oolitic shoal in the highest energy zone, within the Comoseris ecozone. Applying this facies model to the sequence stratigraphic interpretation of the vertical succession results in recognising a third-order relative sea-level fluctuation, which can be correlated at least with Lorraine (France) and Switzerland.

Lithofacies, palynofacies, and sequence stratigraphy of Palaeogene strata in Southeastern Nigeria

Integrated sedimentologic, macrofossil, trace fossil, and palynofacies data from Paleocene-Middle Eocene outcrops document a comprehensive sequence stratigraphy in the Anambra Basin/Afikpo Syncline complex of southeastern Nigeria. Four lithofacies associations occur: (1) lithofacies association I is characterized by fluvial channel and/or tidally influenced fluvial channel sediments; (2) lithofacies association II ( Glossifungites and Skolithos ichnofacies) is estuarine and/or proximal lagoonal in origin; (3) lithofacies association III ( Skolithos and Cruziana ichnofacies) is from the distal lagoon to shallow shelf; and (4) shoreface and foreshore sediments ( Skolithos ichnofacies) comprise lithofacies association IV. Five depositional sequences, one in the Upper Nsukka Formation (Paleocene), two in the Imo Formation (Paleocene), and one each in the Ameki Group and Ogwashi-Asaba Formation (Eocene), are identified. Each sequence is bounded by a type-1 sequence boundary, and contains a basal fluvio-marine portion representing the transgressive systems tract, which is succeeded by shoreface and foreshore deposits of the highstand systems tract. In the study area, the outcropping Ogwashi-Asaba Formation is composed of non-marine/coastal aggradational deposits representing the early transgressive systems tract. The occurrence of the estuarine cycles in the Palaeogene succession is interpreted as evidence of significant relative sea level fluctuations, and the presence of type-1 sequence boundaries may well be the stratigraphic signature of major drops in relative sea level during the Paleocene and Eocene. Sequence architecture appears to have been tectono-eustatically controlled.

Late Miocene to early Pliocene biofacies of Wanganui and Taranaki Basins, New Zealand: Applications to paleoenvironmental and sequence stratigraphic analysis

The Matemateaonga Formation is late Miocene to early Pliocene (upper Tongaporutuan to lower Opoitian New Zealand Stages) in age. The formation comprises chiefly shellbeds, siliciclastic sandstone, and siltstone units and to a lesser extent non‐marine and shallow marine conglomerate and rare paralic facies. The Matemateaonga Formation accumulated chiefly in shelf paleoenvironments during basement onlap and progradation of a late Miocene to early Pliocene continental margin wedge in the Wanganui and Taranaki Basins. The formation is strongly cyclothemic, being characterised by recurrent vertically stacked facies successions, bounded by sequence boundaries. These facies accumulated in a range of shoreface to mid‐outer shelf paleoenvironments during conditions of successively oscillating sea level. This sequential repetition of facies and the biofacies they enclose are the result of sixth‐order glacio‐eustatic cyclicity. Macrofaunal associations have been identified from statistical analysis of macrofossil occurrences collected from multiple sequences. Each association is restricted to particular lithofacies and stratal positions and shows a consistent order and/or position within the sequences. This pattern of temporal paleoecologic change appears to be the result of lateral, facies‐related shifting of broad biofacies belts, or habitat‐tracking, in response to fluctuations of relative sea level, sediment flux, and other associated paleoenvironmental variables. The associations also show strong similarity in terms of their generic composition to biofacies identified in younger sedimentary strata and the modern marine benthic environment in New Zealand.

Microboring and taphonomy in Middle Oxfordian to lowermost Kimmeridgian (Upper Jurassic) from the Prebetic Zone (southern Iberia)

Microboring was investigated through thin section analysis of Oxfordian rocks from the Prebetic Zone (Betic Cordillera, southern Spain). Microboring description and distribution were analysed, as was their correlation with traits such as the type and size of bioclasts and microtaphonomic features (encrustation and fragmentation). Single and branching microboring are the two major morphological groups differentiated. Microborers were not identified but by their patterns of distribution in the bioclasts and in the environmental setting are assumed to be phototrophic. Microboring only affected bioclasts, with higher values of microboring index ( MB i) registered in thicker ammonoid shells and serpulids, and lower ones in ostracods, foraminifera and small bivalves, gastropods and echinoderms. A very close, direct relationship exists between bioclast size and microboring abundance, as well as between the microboring ( MB i) and encrustation indexes ( E i) used. In contrast, a clear relationship between MB i and the fragmentation index ( F i) has not been proved. Microboring activity has been interpreted to be related to both bioclast-size and time exposure of bioclasts on the seafloor, the latter resulting directly proportional to the rate of sedimentation in low energy environments. The studied features ( MB i, F i, E i and bioclast mean size) were analysed taking into account the stratigraphic intervals investigated (I=Transversarium Zone to lower Bifurcatus Zone, II=upper Bifurcatus Zone, III=Bimammatum Zone, and IV=Planula Zone p. p.), and the trends registered were interpreted as a final consequence of relative sea-level fluctuations. Stratigraphic intervals I and IV, characterised by higher values in MB i and E i, were related to lower sedimentary rates during increasing distality in a context of relative sea-level rise, which is consistent with the development of Transgressive System Tract (TST) conditions. Stratigraphic intervals II and III, showing lower values in MB i and E i, are related to higher sedimentation rates and decreasing distance from shore during relative sea-level falls, which are in accordance with developing Highstand System Tract (HST) and Shelf Margin Wedge (SMW) conditions. Data obtained and interpretations agree with the general ecostratigraphic context in the studied area previously proposed by the authors.

Microboring and taphonomy in Middle Oxfordian to lowermost Kimmeridgian (Upper Jurassic) from the Prebetic Zone (southern Iberia)

Abstract Microboring was investigated through thin section analysis of Oxfordian rocks from the Prebetic Zone (Betic Cordillera, southern Spain). Microboring description and distribution were analysed, as was their correlation with traits such as the type and size of bioclasts and microtaphonomic features (encrustation and fragmentation). Single and branching microboring are the two major morphological groups differentiated. Microborers were not identified but by their patterns of distribution in the bioclasts and in the environmental setting are assumed to be phototrophic. Microboring only affected bioclasts, with higher values of microboring index (MBi) registered in thicker ammonoid shells and serpulids, and lower ones in ostracods, foraminifera and small bivalves, gastropods and echinoderms. A very close, direct relationship exists between bioclast size and microboring abundance, as well as between the microboring (MBi) and encrustation indexes (Ei) used. In contrast, a clear relationship between MBi and the fragmentation index (Fi) has not been proved. Microboring activity has been interpreted to be related to both bioclast-size and time exposure of bioclasts on the seafloor, the latter resulting directly proportional to the rate of sedimentation in low energy environments. The studied features (MBi, Fi, Ei and bioclast mean size) were analysed taking into account the stratigraphic intervals investigated (I=Transversarium Zone to lower Bifurcatus Zone, II=upper Bifurcatus Zone, III=Bimammatum Zone, and IV=Planula Zone p.p.), and the trends registered were interpreted as a final consequence of relative sea-level fluctuations. Stratigraphic intervals I and IV, characterised by higher values in MBi and Ei, were related to lower sedimentary rates during increasing distality in a context of relative sea-level rise, which is consistent with the development of Transgressive System Tract (TST) conditions. Stratigraphic intervals II and III, showing lower values in MBi and Ei, are related to higher sedimentation rates and decreasing distance from shore during relative sea-level falls, which are in accordance with developing Highstand System Tract (HST) and Shelf Margin Wedge (SMW) conditions. Data obtained and interpretations agree with the general ecostratigraphic context in the studied area previously proposed by the authors.

Lateglacial and Holocene sea level changes in semi-enclosed seas of North Eurasia: examples from the contrasting Black and White Seas

A comparison of the Black and White Seas, which differ in their tectonic, glacial and climatic history but which share a strong dependence upon limited water exchange with the world ocean, represents an opportunity for the identification of major factors controlling sea level changes during the Lateglacial and Holocene and for the correlation of these changes. Existing data were critically analyzed and compared with the results of geological, geomorphological and palaeohydrological studies obtained by the present authors during the past two decades. We conclude that glacioeustatic processes played a major role in relative sea level changes on most coasts of both areas. However, along several coastlines, other factors overwhelm glacioeustasy during some time intervals. In the Black Sea, water level rose from its minimum position, −100–120 m, at 18–17 ka BP, to −20–30 m at nearly 9 ka BP. In the White Sea, the decreasing trend in relative sea level is well illustrated on the Kola Peninsula and in Karelia, subject to glacioisostatic emergence. A drastic sea level fall from +15 to −25 m occurred with the drainage of glacial lakes in the eastern White Sea (12.5–9.5 ka BP). The Black and White Sea histories changed drastically in the early Holocene or in the beginning of the middle Holocene (9.5–7.5 ka BP) due to the intrusion of water from the Mediterranean and the Barents seas, respectively. During this period, the White Sea developed under the strong influence of the formation of “ice shelves” and “dead ice” blocks, retreating glaciers, as well as of glacioisostatic and related processes. The Black Sea history, however, was determined by water exchange with the Mediterranean via the shallow Dardanelles and Bosporus straits (outflow from the Black Sea 10–9.5 ka BP and inflow from 9–7.5 ka BP according to various data), and, partially, by river discharge variations caused by climatic changes on the Russian Plain. The hypothesis of a catastrophic sea level rise from −120–150 to −15–20 m nearly 7550 calendar years BP is not supported by our data. Water intrusion from the Mediterranean was fast but not catastrophic. In the Black Sea, periods of high sea levels after the intrusion of Mediterranean waters are dated from four sedimentary complexes, Vityazevian, Kalamitian, Dzhemetian and Nymphaean, from nearly 7.5, 7–6, 5.5–4.5 and 2.2–1.7 ka BP, respectively. A fluctuating pattern of sea level change was established in the White Sea after the drainage of proglacial lakes and intrusion of ocean waters at the end of the early Holocene (nearly 8.5–8.2 ka BP). Major periods of sea level rise in the White Sea are dated from the late Boreal–early Atlantic (8.5–7.5 ka BP), late Atlantic (6.5–5.2 ka BP), middle Subboreal (4.5–4 ka BP) and middle Subatlantic (1.8–1.5 ka BP). Fluctuations of relative sea level during the middle and late Holocene were possibly on the order of several meters (from +2–3 to −2–3 m in the Black Sea and from +3–5 to −2–3 m in the White Sea). Lower estimates of regressive stages are principally derived from archaeological data on ancient settlements in tectonically submerging deltaic areas and cannot be regarded as reliable. Palaeohydrological analysis does not indicate that intensive (15–25 m or greater) sea level fluctuations were present in the Black Sea or in the White Sea during the middle and late Holocene. Instead, such analysis provides independent evidence to support the argument that significant differences in water level between the Black Sea and the Mediterranean could not be maintained for an extended period of time.

Upper Triassic–Lower Cretaceous seismic sequence stratigraphy and basin tectonics at Bornholm, Denmark, Tornquist Zone, NW Europe

An integrated analysis of seismic sequence stratigraphy and structural evolution of a dynamic intraplate fault basin was conducted along a segment of the Tornquist Zone at the boundary between the Northwest European Craton and the Baltic Shield-East European Platform. High-quality regional seismic-reflection lines document the Late Triassic through early Late Cretaceous tectonic history and depositional sequence architecture. The stratigraphic package was divided into three major transgressive/regressive cycles (1st-order sub-cycles). The upper Upper Triassic through Lower Cretaceous siliciclastic cycles I and II are divided into 2nd-order transgressive/regressive facies cycles composed of higher frequency 3rd-order sequences. The lowstand basin fill comprises stacked successions of lowstand systems tracts produced by relative sea-level rises and falls. During the 3rd-order regressive intervals highstand-dominated depositional conditions prevailed to the northwest while lowstand-dominated conditions occurred to the southeast. Cycle III records an Upper Cretaceous major siliciclastic–chalk cycle. The magnitude of the relative sea-level highs and lows increased up through the studied interval. A two-dimensional structural-evolution analysis is based on the variation of the sediment thickness across the fault blocks up through the sedimentary column. Basin subsidence can be divided into successive structural/tectonic regimes. Fault block rotation and structural inversion characterized the early subsidence of the basin floor. During the second interval, inversion ceased while fault-block rotation continued. In the third interval, the rotation also stopped and no deformation of the basin is recognized. The three major transgressive/regressive facies cycles and associated relative sea-level cycles are linked with the structural regimes. Contemporaneous deposition of 3rd-order highstand- and lowstand-dominated complexes related to differential subsidence and uplift is also evidence of basin tectonics as the controlling factor on relative sea-level changes. Comparison of the relative sea-level curve developed for the study area with eustatic sea-level curves shows that they follow different trends. The deviations between these curves, and the correlation of sequence boundaries with changes of the tectonic regime, support the conclusion that tectonics was a major control on relative sea-level fluctuations in the study area. The 2nd-order cycles linked with deformation episodes along the Tornqist Zone correlate with Lower-Middle Jurassic 2nd-order cycles in England. Deformation along the Tornquist Zone may thus have influenced the sequence stratigraphy across the entire Northwest European Craton.

Pliocene–Pleistocene sequences bounded by subaerial unconformities within foramol ramp calcarenites and mixed deposits (Salento, SE Italy)

Nine discrete, metre-scale sequences, of Early Pliocene to Middle Pleistocene age, were deposited in the small Novoli graben (Salento peninsula, Puglia, S-Italy). They consist of carbonate and mixed carbonate-siliciclastic sediments, deposited on a slowly subsiding foreland ramp. Skeletal concentrations and intervening less fossiliferous intervals have been examined to provide information on major environmental parameters and infer the dynamics of their changes. Taphonomic and palaeoecological analyses indicate that storm-induced waves and currents, reduced sediment input, and settling behaviour of components were the main factors controlling the features of the various shellbed types. The concentrations were formed below fair-weather wave base in low-stress inner-to-outer shelf environments and are often associated with surfaces or intervals that are characterized by sedimentary condensation. Vertical change in the fossil content within individual cycles indicates water depth changes that were parallel to climatic fluctuations, hence may result from glacio-eustatic sea-level changes. Most sequences are bounded by subaerial, karstic unconformities. Because of the regional setting of low subsidence rate, the record of the relative sea-level fluctuations is incomplete. Episodes of subaerial exposure and concomitant effects of vadose diagenesis are documented by: (i) diagenetic changes leading to hardening of unconformity horizons; (ii) local subvertical solution pits developed in the vadose zone below unconformity surfaces; (iii) networks of polygonal cracks below unconformities; and (iv) infilling of solution pits and polygonal cracks with vadose silt and marine sediment inwashed during transgressions following the subaerial stages. Lower sequences are characterized by tighter cementation and significant increase in moldic and vuggy porosity, due to superimposition of the diagenetic effects of repeated high-amplitude sea-level fluctuations.

Lithofacies and depositional processes on a high, steep-margined Carboniferous (Bashkirian–Moscovian) carbonate platform slope, Sierra del Cuera, NW Spain

The depositional slope of the Sierra del Cuera, a Carboniferous (Bashkirian–Moscovian), high, steep-margined carbonate platform, provides excellent cross-sections of lithofacies zonations and associated stratal geometries. The steep (30–40°) and nearly planar upper slope is dominated by massive sheet-like layers of microbial, cement-rich boundstone, which alternate with intercalations of red-stained bryozoan cementstone with crinoids and brachiopods. The slightly gentler (20–26°) and concave-upward lower slope is characterized by clast-supported resedimented deposits. The upper slope extended from platform break to ca. 300 m water depth, whereas lower slope sediments were deposited in water depths up to 600–700 m, at which level the slope beds flatten to a few degrees (toe-of-slope) and interfinger with spiculitic and argillaceous basinal sediments. Between 250 and 450 m water depth, boundstones and breccias alternated in a transitional zone. The lower slope sediments include clast-supported breccias with radiaxial fibrous cement in interparticle space, mud- to clast-supported breccias with red-stained carbonate mud matrix and packstone to grainstone and rudstone beds. Most of the clasts comprise boundstone reworked from an upper slope setting and smaller grains are platform and slope derived. A pervasive submarine cementation occurs along the upper two-thirds of the flank and this stabilized the slope. Slope deposition is interpreted as follows. During active boundstone accretion, microbial boundstone layers slid off and formed breccia tongues extending from the lower upper slope down to the toe-of-slope. Rock falls and avalanches were generated whenever the shear strength of the substrate of loose (or partly lithified) sediment was exceeded. Upper-slope boundstone accretion and shedding, independent of the depth of light penetration, controlled most of the depositional processes on the slope. Cement-dominated intervals are considered to be related to early highstand (and/or flooding) phases. Relative sea-level fluctuations and/or associated changes in the water conditions are believed to be responsible for intervals of low boundstone production or cement precipitation. Whether the in situ boundstone and breccia are preferentially related to lowstand or highstand periods is, as yet, unclear.

Sea-level fluctuations during the last 8600 years in the de la Plata river (Argentina)

The de la Plata river, considered from the geomorphologic point of view, can be defined as a unit composed of a set of features genetically linked together which were formed as a result of the post-Last Glacial Maximum transgression. Regional stratigraphical, morphological and topographical studies carried out in the de la Plata river and surrounding areas of eastern Argentina determined that the Holocene evolution of the area was the result of processes resulting from relative sea-level fluctuations. In order to date the different stages of evolution, a curve of sea-level fluctuations was constructed after a selective choosing of samples with reliable ages supported by field geological evidence. The curve shows a rapid initial transgressive event and the maximum highstand of mean sea level at 6000 yr BP at a relative elevation of +6.5 m above present. The following regressive event was characterized by a discontinuous fall in sea level. Geomorphological evidence suggests that sea-level fall could have experienced minor changes in rate as well as moments of stability that are not shown by the curve. Short interruptions in the geological record can be explained either by the same minor changes in sea level or by a change in wave regime. Correlation of transgressive–regressive events with paleoclimatic and biogeographic information proposed that Holocene sea-level fluctuations in the de la Plata river were mainly controlled by climatic changes.

PALEOAMBIENTE E ESTRATIGRAFIA DA FORMAÇÃO IPIXUNA, ÁREA DO CAPIM, LESTE DA SUB-BACIA DE CAMETÁ

Facies analysis and stratigraphy of the Ipixuna Formation (Late Cretaceous-?Early Tertiary), eastern Cameta Sub-basin, revealed a variety of depositional environments including tidal-influenced (?) fluvial channel, flood plain/mud plug, tidal flat, bay fill, tidal channel and tidal delta. These deposits are better justified applying a wave-dominated estuarine model. The marine influence is attested by the nature of the sedimentary structures attributed to tidal processes (i.e., reactivation surfaces, foresets with bi-directional azimuths, mud couplets), as well as by the ichnological assemblage consisting of Diplocraterion, Planolites, Thalassinoides, Teichichinus, Taenidium,Skolithos. Chondrites ? e Cylindrichnus. In addition to these features, estuarine nature is revealed by the upward gradation from fluvial to tidal-influenced deposits. The stratigraphic analysis led to distinguish two stratigraphic units (A1 and A2) bounded by regionally correlatable discontinuity surfaces (SD1 and SD2). The question remains whether these are completely unrelated sequences or if they record low amplitude sequences formed within a compound estuarine system due to high frequency relative sea level fluctuations. A better characterization of these stratigraphic units is important for the kaolin exploration, as the high quality kaolin is confined to unit A1, while the semi-flint is related to unit A2.

Geomorphological and sequence stratigraphic variability in wave‐dominated, shoreface‐shelf parasequences

Abstract Physical stratigraphy within shoreface‐shelf parasequences contains a detailed, but virtually unstudied, record of shallow‐marine processes over a range of historical and geological timescales. Using high‐quality outcrop data sets, it is possible to reconstruct ancient shoreface‐shelf morphology from clinoform surfaces, and to track the evolving morphology of the ancient shoreface‐shelf. Our results suggest that shoreface‐shelf morphology varied considerably in response to processes that operate over a range of timescales. (1) Individual clinoform surfaces form as a result of enhanced wave scour and/or sediment starvation, which may be driven by minor fluctuations in relative sea level, sediment supply and/or wave climate over short timescales (101−103 years). These external controls cannot be distinguished in vertical facies successions, but may potentially be differentiated by the resulting clinoform geometries. (2) Clinoform geometry and distribution changes systematically within a single parasequence, reflecting the cycle in sea level and/or sediment supply that produced the parasequence (102−105 years). These changes record steepening of the shoreface‐shelf profile during early progradation and maintenance of a relatively uniform profile during late progradation. Modern shorefaces are not representative of this stratigraphic variability. (3) Clinoform geometries vary greatly between different parasequences as a result of variations in parasequence stacking pattern and relict shelf morphology during shoreface progradation (105−108 years). These controls determine the external dimensions of the parasequence.

Indices de fluctuations mineures du niveau marin relatif à l’Holocène supérieur, à l’Isle-Verte, côte sud de l’estuaire du Saint-Laurent, Québec

À L'Isle-Verte, sur la rive sud de l'estuaire du Saint-Laurent, des relevés récents ont permis de mettre en évidence des fluctuations mineures du niveau marin relatif au cours de la seconde moitié de l'Holocène. À cet endroit, le littoral est caractérisé par une vaste batture, une basse terrasse et une falaise morte. La batture et le substrat de la basse terrasse correspondent à une surface d'érosion taillée dans l'argile glacio-marine de la Mer de Goldthwait vraisemblablement au cours de la transgression Laurentienne. Il en fut de même pour la falaise morte (falaise Micmac), elle aussi taillée dans l'argile. Une date au 14C de 4 ka sur Mya arenaria en position de vie autour d'un caillou résiduel sur la surface d'érosion a fourni un âge minimal pour l'aplanissement de la surface argileuse. La basse terrasse au pied de la falaise morte comprend deux sections ; la partie interne, à 5-6 m d'altitude (côté sud de la Nationale 132), est constituée de sédiments fins (limon et sable fin) intertidaux localement recouverts de sable et petits graviers (plage) ; cette partie daterait d'environ 2 ka, ce qui est l'âge moyen de la terrasse Mitis sur les deux rives de l'estuaire. La partie externe, à 4-5 m d'altitude, est plus jeune. À l'embouchure de la rivière Verte, un dépôt intertidal mis en place au cours du dernier millénaire et recouvrant des alluvions fluviatiles datées de 1,4 à 1,6 ka témoigne d'une fluctuation mineure (± 1 m) du niveau marin relatif. C'est aussi au cours de cette période qu'ont été mis en place les dépôts intertidaux (slikke et schorre inférieur) sous-jacents au schorre supérieur actuel. Présentement le rivage semble connaître une période de stabilité relative.

Interplay between tectonics and glacio-eustasy: Pleistocene succession of the Crotone basin, Calabria (southern Italy)

On a global scale, the Crotone basin preserves one of the best-developed and most complete Pleistocene marine records available in outcrop, as important as those in California, New Zealand, and Japan. A deformed, markedly cyclothemic, lower to middle Pleistocene succession is present in the territory of San Mauro Marchesato (Crotone area, southern Italy), showing an overall shallowing trend from slope mudstones to marginal marine and continental deposits. Preservation and high resolution of cyclothems occurred through the interaction between high-amplitude relative sea-level fluctuations, a particular pattern of differential subsidence due to intrabasinal tectonics, and high rates of sediment supply. The studied succession was laid down in the Crotone basin under an extensional tectonic regime, following a major, middle Pliocene contractional phase probably of transpressional nature. Two major unconformities, locally accompanied by angular discordances, occur within the succession. The former, centered at ca. 1.2 Ma, is thought to reflect the opening of the San Mauro subbasin within the Crotone basin in the early Pleistocene, following dextral transtensional motion along north- to north-northeast–trending faults. The latter, with a hiatus lasting from ca. 0.65 to 0.45 Ma, may reflect the decoupling of the Calabrian block with respect to Adria and Sicily, allowing further advancing of the Calabrian arc in the Ionian area, where subduction could continue until the present time. The lower part of the succession (the H. sellii and “large Gephyrocapsa ” Zones, from ca. 1.67 to ca. 1.23 Ma) consists of slope to outer-shelf monotonous mudstones and is bounded at the top by the first unconformity, whose gap suppresses the upper part of to locally the entire “large Gephyrocapsa ” Zone (1.608–1.235 Ma) and the lower part of the “small Gephyrocapsa ” Zone (1.235–0.96 Ma). A number of cyclothems developed in an outer- to inner-shelf environment within the “small Gephyrocapsa ” Zone. Biomagnetostratigraphic constraints strongly support a correlation between the condensed sections of cyclo thems and MIS (marine isotope stage) 33 to MIS 25. From the base of the P. lacunosa Zone (at ca. 0.96 Ma) upward, the succession rapidly becomes sand dominated, a change that can be confidently correlated with the major climatic shift associated with MIS 24 to MIS 22. In the following succession, two tephra layers, named “Pitagora ash” and “Parmenide ash,” provide mappable isochronous surfaces across the subbasin. The sedimentary record is remarkably cyclo themic, characterized by a stack of simple or composite, seaward-prograding, sand- dominated tongues and intervening aggradational deposits related to transgressive-deepening episodes. The cyclothems can be confidently correlated with the oxygen isotope record up to the Matuyama-Brunhes inversion, i.e., up to MIS 19, whereas the stratigraphic record postdating MIS 19 has poorer chronological constraints. Dating is provided by tracing the Parmenide ash in the deeper-water coeval succession of the southern part of the Crotone basin, where the deposits including the ash can be correlated by means of nannofossil biostratigraphy with termination V (transition from MIS 12 to MIS 11). The second unconformity marks an abrupt increase in the proximal character of the sedimentary deposits forming the cyclothems, which incorporate increasing amounts of marginal-marine to continental deposits in the upper part of the subbasin infill. Several lines of direct and indirect evidence indicate that, in spite of the dramatic role of tectonics in shaping stratigraphic architecture, the roles of tectonics and eustasy can be disentangled, owing to the different time scales of the tectonic events and the high-frequency, high-amplitude glacio- eustatic Pleistocene cycles. Interaction between intrabasinal tectonics and high rates of sediment supply allowed forced regressive and possibly also lowstand systems tracts to be preserved in some cyclothems, particularly in the lower part of the succession, an unusual fact in shelf deposits. Considering the far younger age of marine terraces on the Ionian side of Calabria when compared to the Tyrrhenian side, it is thought that, during ongoing subduction of the Ionian crust, a wave of uplift and related extensional tectonics migrated southeastward in the rear of the frontal accretionary wedge.

The Clearwater Formation, Cold Lake, Alberta: a worldclass hydrocarbon reservoir hosted in a complex succession of tide-dominated deltaic deposits

Research Article| September 01, 2002 The Clearwater Formation, Cold Lake, Alberta: a worldclass hydrocarbon reservoir hosted in a complex succession of tide-dominated deltaic deposits G. Glen McCrimmon; G. Glen McCrimmon Exxon-Mobil Exploration Co., P.O. Box 4778, Houston, Texas 77120, USA Search for other works by this author on: GSW Google Scholar R.W.C. Arnott R.W.C. Arnott Department of Earth Sciences and Ottawa-Carleton Geoscience Centre, University of Ottawa, Ottawa, ON K1N 6N5 Search for other works by this author on: GSW Google Scholar Author and Article Information G. Glen McCrimmon Exxon-Mobil Exploration Co., P.O. Box 4778, Houston, Texas 77120, USA R.W.C. Arnott Department of Earth Sciences and Ottawa-Carleton Geoscience Centre, University of Ottawa, Ottawa, ON K1N 6N5 Publisher: Canadian Society of Petroleum Geologists Received: 15 Oct 2001 Revision Received: 26 May 2002 First Online: 02 Mar 2017 Online ISSN: 2368-0261 Print ISSN: 0007-4802 © The Society of Canadian Petroleum Geologists Bulletin of Canadian Petroleum Geology (2002) 50 (3): 370–392. https://doi.org/10.2113/50.3.370 Article history Received: 15 Oct 2001 Revision Received: 26 May 2002 First Online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation G. Glen McCrimmon, R.W.C. Arnott; The Clearwater Formation, Cold Lake, Alberta: a worldclass hydrocarbon reservoir hosted in a complex succession of tide-dominated deltaic deposits. Bulletin of Canadian Petroleum Geology 2002;; 50 (3): 370–392. doi: https://doi.org/10.2113/50.3.370 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyBulletin of Canadian Petroleum Geology Search Advanced Search Abstract The Lower Cretaceous (Lower Albian) Clearwater Formation at Cold Lake, Alberta is a complex assemblage of nonmarine, marginal marine and shallow marine strata. Within the study area, these strata form four unconformity-bounded depositional sequences that in most cases consists of a lower progradational unit overlain by a retrogradational unit. The base of all sequences, except the first, is marked locally by a deeply incised, northwest–south-trending paleovalley. Although eroded during a fall of relative sea level, each paleovalley was filled mostly with sediment deposited by a northwest-prograding tide-dominated delta during each subsequent rise of relative sea level. Reservoir strata occur in the lower, deltaic part of the three youngest sequences, and consist primarily of nonmarine fluvial and high-energy tidal sand flats deposits. Deltaic progradation was halted, however, by a possible decrease in sediment flux and a return to retrogressive conditions. This formed an areally extensive flooding surface, which then was overlain by retrogradational shallow-marine deposits (embayment-mouth deposits). Accordingly, each sequence represents a short-term (4th order?) fluctuation of relative sea level that was superimposed on a long-term (3rd order?) rise of relative sea level. In addition, each successive sequence indicates a progressively more basinward migration of (tide-dominated) deltaic facies (prograding sequence set) suggestive of temporal changes in some number of local and/or regional sedimentary controls, such as sediment flux, rates of relative sea level, or depositional gradient. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Fluvial/tidal interaction at the southern Tethyan strandline during Triassic Mukheiris times in central Jordan

The Triassic (Anisian) Mukheiris Formation is exposed along the northeastern margins of the Dead Sea area, and encompasses all those sediments preserved between the Triassic Hisban and Iraq al Amir formations. It attains a thickness of at least 108 m, and comprises two subdivisions defined here: a lower tidal unit and an upper fluvial unit. The presence of fossiliferous limestones and marlstones in the lower member, and the presence of thin, rhythmic tidal bedding, flaser bedding and oscillation ripple marks suggests deposition in a tidally influenced shallow water, marine environment. The erosively based, fining-upward cycles of non-fossiliferous, unidirectional cross-bedded quartz arenites, and paucity of siltstones and mudstones in the lower part of the fluvial unit indicate that deposition occurred within a braided mixed load fluvial system. The increased proportion of fines ratio in the upper part suggests a change to a more meandering fluvial system. The spatial and temporal arrangement of tidal/fluvial facies during Mukheiris times may be related to fluctuations of the Tethyan strandline due to fluctuations in relative sea level and the development of alternating transgressive and regressive events.

New data on the Holocenic sea-level rise in NW Sicily (Central Mediterranean Sea)

The emerged and submerged coastal tracts of selected areas in NW Sicily (San Vito Lo Capo Promontory and Marettimo Island in the Egadi Archipelago) have been studied by means of an interdisciplinary approach (geomorphological and neotectonic surveys, palaeontological, depositional and petrographical observations) with the aim to characterize the coastal evolution of the sector over a wide time frame (Late Pleistocene and Holocene) and to recognize the geological indicators of relative sea-level fluctuations. Neotectonic studies performed all along the coastal sector through the check of the present-day height of marine notches and of the inner margin of marine terraces of Eutyrrhenian age allowed to assess the entity of post-Tyrrhenian differential crustal movements in the area. The calculated rates of uplift confirm the relative stability of the area in the last 125 ka and that the relative corrections introduced can be considered negligible in the reconstruction of sea-level rise in the last thousand years. On the base of these considerations, the sea-level rise curve which has been drawn for the Holocene through the radiometric dating ( 14C and U/Th) of submerged speleothems and Vermetid reefs is assumed to gain a regional significance and to represent a good reference datum for the Central–Southern Mediterranean Sea. In addition, the sea-level rise data are in good agreement with the predicted sea-level curves based on geophysical models previously applied to the same study areas.

Architecture of channel bodies and paleovalley fills in high-frequency Carboniferous sequences, Sydney Basin, Atlantic Canada

ABSTRACT Fluvial channel bodies in the Pennsylvanian Sydney Mines Formation are contained within high-frequency sequences that represent relative sea-level fluctuations, linked to climate change, on a gently subsiding craton. Channel-body style within coastal-plain deposits was controlled by sea-level transit cycles, modulated by climate and substrate resistance. Coarse bed-load systems are deeply incised, multi-storey bodies up to 30 m thick. Some represent valleys backfilled during late lowstand and transgression, probably under a humid climate. Sinuous channel systems display well developed lateral accretion surfaces and ridge-and-swale topography. Distributary systems are narrow channel bodies that cut bayfill deposits. These two groups lie within highstand deposits, and represent the readvance of coastal rivers following maximum transgression. Sand-flat systems consist of plane-bedded sand sheets and downstream-accreting macroforms, laid down under ephemeral flow conditions, adjacent to deep sinuous channels. They are interpreted as channel and valley fills generated during late highstand, falling stage, and lowstand under a strongly seasonal climate. Calcrete caps on some sandflat bodies suggest that they filled prior to the main lowstand phase of paleosol development. A complex relationship is apparent between channel or valley fills and mature paleosols that bound sequences. Resistant substrates (coals, indurated limestones) influenced channel-body geometry by promoting lateral expansion and localising incision. 1 Present Address: Nova Scotia Community College, Institute of Technology Campus, P.O. Box 2210, Halifax, N S, Canade B3J 3C4; E-mail: batsonpA@it.nscc.ns.ca End_Page 138------------------------