New insights into sedimentary processes and related morphologies in tidal straits: the case of the Rio-Antirio Sill (Greece)

2021 ◽  
Author(s):  
Romain Rubi ◽  
Aurélia Hubert-Ferrari ◽  
Elias Fakiris ◽  
Dimitris Christodoulou ◽  
Xenophon Dimas ◽  
...  
Keyword(s):  
High Resolution ◽  
Tidal Currents ◽  
Internal Tides ◽  
Tectonic Activity ◽  
Depositional Model ◽  
Carbonate Production ◽  
Sea Floor ◽  
Bottom Currents ◽  
Gulf Of Corinth ◽  
Underwater Camera

<p>Straits are crossed by marine currents that are amplified due to the water constriction. These nearshore high-velocity flows are problematic for offshore infrastructures (bridge pillars, cables, pipelines etc), but constitute an under-estimated carbon-free kinematic energy source. Most of the straits are dominated by tidal currents which flow axially to the seaway, with reversal directions and phase difference between the two interlinked basins. These tidal currents interplay with: (i) sediment sources that also includes in situ carbonate production and deltas, (ii) tectonic activity, and (iii) inherited lowstand features, all shaping the sea floor into complex geomorphologies. Previous studies have highlighted a common tidal-strait depositional model with a strait-center zone in erosion and on each side a dune-bedded strait zone with 3D and 2D tidal dunes and tidal ripples.</p><p>Here, we present an alternative tidal-strait model based on an interdisciplinary approach using high-resolution geophysical and oceanographical data to better constrain the processes acting at the sea floor. We focus on the Rion-Antirion strait in Greece which controls the connection between the Gulf of Corinth and the Mediterranean Sea. Based on high-resolution multibeam bathymetry (MBES) over an area of 211km<sup>2</sup>, we identify and quantify the morphologies by extracting bathymetric swath profiles. These results are integrated with currents data (ADCP) and CTD profiles. In addition,  we use high-resolution Chirp subbottom profiles and high-resolution sparker seismic reflection profiles to document the stratigraphy and morphology of the sedimentary beds and erosional features. To complete this dataset, we use a towed underwater camera to image the sea-floor.</p><p>We define three zones, each characterized by common hydrodynamics, bedforms and morpho-bathymetric features which reveal an asymmetric strait. (1) The western zone is dominated by tectonics with salt diapirism and faults which interact with bottom currents to form erosional pools and ridge systems. (2) The strait center zone displays abrasion surfaces which consists on a rough rock-paved plateau surface encrusted by living red corals and sponges. Moreover, a moat cuts this plateau that localizes the sill at its eastern tip. This strait center area is dominated by inherited hard-ground fluviatile deposits which are abraded by bidirectional tidal-currents. (3) The eastern zone shows a deeper bathymetry with smoother features. The sediments are veneered on slopes forming plastered drifts and spits while the basin axis presents large chutes and pools. The bottom-currents in this zone, are related to internal tides from the Gulf of Corinth that are delayed with respect to the tidal currents. These internal-tide currents (3m/s) are three times faster than the oceanic tidal-currents in the strait (1m/s).</p><p>In conclusion, we document a tidal-strait system, which is interacting with active tectonics, and internal-tides along its axis. In results, Rion strait displays complex bathymetric features without any 3D or 2D tidal dunes. Thus, it provides a new end member to the tidal-strait depositional model. This end member is characterized by a re-localization of the erosion, bypass and deposition. It illustrates the key role of internal tides for straits located at the boundary between a confined deep-basin and the open-sea.</p>

scholarly journals GEOMETRY OF HOLOCENE TIDAL NOTCHES – SEA LEVEL MARKERS AT PERACHORA PENINSULA, GULF OF CORINTH, GREECE

2017 ◽  
Vol 50 (1) ◽  
pp. 468
Author(s):  
S. Schneiderwind ◽  
M. Kázmér ◽  
S. Boulton ◽  
I. Papanikolaou ◽  
K. Reicherter
Keyword(s):  
High Resolution ◽  
Sea Level ◽  
Laser Scanning ◽  
Seismic Event ◽  
Tectonic Activity ◽  
Level Indicator ◽  
Mean Sea Level ◽  
Related Information ◽  
Gulf Of Corinth ◽  
Coastal Cliffs

Tidal notches are a generally accepted sea level indicator that, when different from mean sea level, witness tectonic activity at or near coastlines. However, how to infer related information is controversial since tectonic uplift from a single seismic event is not likely to exceed several decimetres. High resolution laser scanning offers the availability of close-up views on exposures and to detect evidence for multiple sea level indicators in between major emergence. Statistically representative profiles along exposure were analysed in order to prove for already described tidal notches and to highlight similar shapes in consistent geometries along coastal cliffs of Perachora Peninsula.

Dynamics of the Late Weichselian ice sheet on Svalbard inferred from high-resolution sea-floor morphology

Boreas ◽  
2007 ◽  
Vol 36 (3) ◽  
pp. 286-306 ◽  
Author(s):  
DAG OTTESEN ◽  
JULIAN A. DOWDESWELL ◽  
JON Y. LANDVIK ◽  
JUERGEN MIENERT
Keyword(s):  
High Resolution ◽  
Ice Sheet ◽  
Sea Floor ◽  
Late Weichselian

scholarly journals Holocene environmental evolution and climate variability inferred from multi-proxy coastal sediment records of southern Greece

2021 ◽  
Author(s):  
Αλέξανδρος Εμμανουηλίδης
Keyword(s):  
Computed Tomography ◽  
High Resolution ◽  
Ct Scanning ◽  
The Holocene ◽  
X Ray ◽  
Salt Pond ◽  
Gulf Of Corinth ◽  
Non Destructive ◽  
Southern Greece ◽  
Δ18o And Δ13c

This thesis presents a multi-proxy reconstruction from 5 different coastal wetlands of southern Greece spanning in the Holocene period and an in-depth review and application of non-destructive systems (CT scanning, X-ray Fluorescence) in paleoenvironmental research. During this thesis, the acquired dataset used consisted of a) X-ray Fluorescence scanning (XRF), b) Computed Tomography (CT) scanning, c) Stable isotopes δ18O and δ13C, d) micropaleontology (foraminifera, ostracods, diatoms, pollen), e) mineralogical analysis, and f) standard sedimentological techniques (grain size, magnetic susceptibility (MS), Total Organic Carbon (TOC), carbonates content). The chronological framework for the sediment cores was established through 14C radiocarbon dating. The wetlands studied are Aliki salt pond (NE Gulf of Corinth), Klisova lagoon (SW Greece), lake Vouliagmeni (E Gulf of Corinth), Agoulinitsa marsh field (W Peloponnese) and Pappas lagoon (NW Peloponnese). The sites form an E-W transect of southern Greece, an area with high climatic and environmental spatial variability, whereas human occupancy on all areas is recorded from antiquity. Non-destructive, high-resolution techniques used in this thesis have been established as standard in the last decades and have been a great asset in geosciences. Computed Tomography (CT) was conducted in lake Vouliagmeni, Agoulinitsa marsh and Pappas lagoon cores. In contrast, XRF was performed on all core sections except for Pappas lagoon core, where the high assemblage of bivalve shells could lead to bias of Ca. The fundamental parameter behind CT analysis is the Hounsfield units that reflect relative density variations in the sediment. Correlation between HU values and heavy elements like Zr has been detected in all cores, whereas distinct sedimentological facies were recorded according to HU variations. In Agoulinitsa and Pappas lagoon, microstructural characteristics like shells/sediment ratio and root remnants were examined through 3D sections, in which HU boundaries were set accordingly. Lake Vouliagmeni sediment core was characterized by extreme stratigraphic variations with lamination structures alternating with homogenous deposits and event layers. Laminae thickness and boundaries were recorded through 3D rendered volumes with HU boundaries. Micro CT scanning and thin section analysis was also performed to cross-check possible variations. Event sedimentation layers were distinguished through the combined use of CT scanning, XRF and MS, with layers responding to increased HU, MS and Mn values. Statistical assessment of elemental distribution and HU revealed 3 different clusters. Cluster A responded to sedimentation during enhanced evaporation in the area, Cluster B emulated sedimentation during increased chemical weathering in the catchment, and Cluster C reflected the homogenous deposits. Aliki salt pond is located in a highly tectonic region, at the northeast part of the Gulf of Corinth in Greece. Beachrock deposits that form a barrier between the salt pond and the marine environment play an essential role in the evolution of the area. The chronological framework was set at ca. 3100 cal BP by four 14C radiocarbon dates and the established evolutionary model indicate four different changes taking place during this period in the study area. From around 3100 to 1600 cal BP, a transition from a closed to an open lagoonal environment, was identified, interrupted by a terrestrial fluvial deposit at ca. 2500 cal BP. A shift toward a closed lagoonal system at around 1600 cal BP and the establishment of a salt pond environment seem to correlate with tectonic activity. The study provides important information about the evolution of the coastal landscape in such an active tectonic region and points the interaction between regional human activity and climatic changes during the late-Holocene period.Klisova lagoon is located in the eastern part of Messolonghi-Etoliko wetland, the biggest lagoonal complex of Greece and an area of great environmental interest. For the last 4700 cal BP, the freshwater influx, the progradation of the Evinos river delta and related geomorphological changes control the environmental conditions (e.g. depth and salinity) in the lagoon system. Considering the centennial temporal resolution of our analyses, small offsets of c.a. 50 years due to the lack of regional reservoir correction do not impact the reported radiocarbon ages considerably. Prior to 4000 cal BP, a relatively shallow water depth, significant terrestrial/freshwater input and increased weathering in the lagoon area are inferred. Elemental proxies and increased dinoflagellate and foraminifera abundances, which indicate marine conditions with prominent freshwater influxes, point to the gradual deepening of the lagoon recorded at the drilling site up to 2000 cal BP. The marine and freshwater conditions equilibrium sets at 1300 cal BP, and the lagoonal system seems to reach its present state. Maxima of anthropogenic pollen indicators during the Mycenaean (3200 cal BP), Hellenistic (2200 cal BP) and Late Byzantine (800 cal BP) periods suggest intervals of increased anthropogenic activities in the study area. Lake Vouliagmeni is subjected to intense climatically and tectonic forces, causing stratigraphic variations, with laminated sediments frequently interrupted by homogenous and event sedimentation deposits. Lamination couplets consist of aragonite layers alternating with detrital and organic residues and form during periods of seawater intrusion and stratification of the lake water. The discontinuous occurrence of laminated deposits excludes a varve based chronology from being established but still highlights the susceptibility of the lake to record environmental and climatically driven changes. Our synthesis model for regional climatic reconstruction and local environmental changes derives from δ18O and δ13C data from the laminated and homogenous sediments studied separately depending on the dominant carbonate mineral. This is further strengthened by high-resolution geochemical proxies, diatom and sedimentological data. Regional climatic trajectories from key sites and possible links to the lake Vouliagmeni record are explored in response to atmospheric circulation patterns variations. Phases of overall humid conditions are recorded by the increased inflow of siliciclastic material in the lake and negative δ18Obulk values. In contrast, periods of marine intrusion and enhanced evaporation are recorded by aragonite precipitation, increased δ18OAr values and laminations. The driving mechanism behind laminae formation seems to be marine intrusions, leading to pycnocline stabilization and increased evaporation of lake surface waters during summer months. Climatic oscillations recorded during the Holocene, apart from their duration, do not exceed events of the last millennia.

scholarly journals FORAMINÍFEROS BENTÓNICOS RECIENTES EN LAS AGUAS PROFUNDAS DE LA CUENCA DE PANAMÁ: ECOLOGÍA Y SU POSIBLE RELACIÓN CON LAS CORRIENTES DE FONDO

2016 ◽  
Vol 42 (1) ◽  
Author(s):  
Germán David Patarroyo Camargo ◽  
José Ignacio Martínez Rodríguez
Keyword(s):  
Benthic Foraminifera ◽  
Deep Sea ◽  
Lower Surface ◽  
Sea Floor ◽  
Bottom Currents ◽  
High Productivity ◽  
Surface Productivity ◽  
Sea Currents ◽  
The Relationship ◽  
Foraminíferos Bentónicos

The relationship between recent benthic foraminifera and bottom currents in the Panama basin (Colombian Pacific) is examined, and the main ecological variables which control the distribution of benthic foraminifera are discussed. The benthic foraminiferal study of 24 core top samples and the integration with previous reports, support the view that in upwelling areas or under high terrigenous influx, the assemblages are dominated by infaunal forms such as Uvigerina, Bolivina, Globobulimina, and Chilostomella, beside common forms such as Uvigerina peregrina Cushman and Epistominella spp., which are indicative of high productivity. In contrast, epifaunal forms such as Cibicidoides, Laticarinina, and Hoeglundina are more common on the flanks of the Cocos and Carnegie Ridges indicating a lower surface productivity and a larger content of dissolved oxygen on the sea floor. Infaunal foraminifera are dominated by Siphouvigerina proboscidea (Schwager). In addition, several proxy taxa of the intensity of deep sea currents were detected in the analyzed assemblages. From these taxa, Cibicides wuellerstorfi (Schwager) has the best proxy potential for the reconstruction of intense bottom currents in sediments from the Cocos and Carnegie Ridges for the Holocene.

scholarly journals Time and time again: getting it right

1992 ◽  
Vol 6 ◽  
pp. 27-27
Author(s):  
William A. Berggren
Keyword(s):  
High Resolution ◽  
Major Change ◽  
Integrated Approach ◽  
Natural World ◽  
Atlantic Coastal Plain ◽  
Laser Fusion ◽  
Isotopic Dating ◽  
Sea Floor ◽  
Late Neogene ◽  
Rock Record

The passage of time cannot be measured in vacuo. Recognition of the time-continuum can only be made by reference to physical and/or biotic events in the geohistorical (rock) record. Inasmuch as these events in the rock record must be measurable in some fashion, they must be related to an objective and retrievable reference standard. Thus the “holy trinity” of litho-bio-and chronostratigraphy can serve as the material (concrete) evidence for the totally conceptual geochronologic units which have no objective existence apart from the natural world.Geochronology is defined here as the conceptual division of continuous time as measured (geochronometry) by the progression in an ordinal series of events. This is best achieved by an approach which integrates four independent data sets: magnetostratigraphy, sea-floor spreading magnetic anomalies, biostratigraphy and isotopic dating. This integrated approach has resulted, until recently, in an ordinal framework capable of measuring the passage of time with greater resolution (precision), though perhaps with less accuracy, than a radiometric approach alone. Recent improvements in the field of isotopic dating-the single crystal laser fusion (SCLF) 40Ar/39Ar technique - now render possible dates with analytical precision of <1% in the early to mid-Cenozoic. The implication for high resolution correlation is clear: until recently biostratigraphy and biochronology have been routinely able to achieve a degree of chronologic resolution considerably higher than that of isotopic dating with its inherently large analytical errors. Laser fusion dating is now capable of providing numerical values for parts of the stratigraphic record with comparable or greater precision than classical biostratigraphy and biochronology. It is clear, now more than ever, that an accurate and precise biostratigraphy is important as we continue to improve upon the geochronologic framework which underlies attempts at high resolution correlation between marginal, platform and deep-sea stratigraphies.A review of the philosophic and methodologic approach of various Cenozoic geochronologic schemes and their strengths and weaknesses will be presented together with a brief discussion of a new, and as yet unpublished, revision to Cenozoic geochronology. Recent assessment of sea floor anomaly patterns indicate a need to stretch the spacing of the interval between anomalies 3A to 5 resulting in an age increase of about 0.5my for Anomaly 5 from 8.92–10.42Ma (BKVC85) to 9.6–11.0Ma; the revised age estimates are consistent with those of McDougall (1984) based on radioisotopic dating of Icelandic basalts. No other major (age) revisions to Neogene chronology are contemplated. However, discrete adjustments are required in the late Neogene as magnetostratigraphic boundaries and biostratigraphic datum events are (re)correlated to the recently proposed astronomically calibrated orbital time scale of Hilgen and Langereis. In the Paleogene the major change is centered on readjustment of the Eocene which, while retaining its relative duration of ~21my, has younger (~34Ma) and older (~54.5Ma) limits, respectively, not unlike some estimates made over 20 years ago. Emphasis on implications for Paleogene geochronology will be stressed with particular reference to events around the Paleocene/Eocene boundary and the integration of correlative NW European and Gulf and Atlantic Coastal Plain stratigraphies in a sequence stratigraphic framework. The continuing efforts being devoted to revising Cenozoic geochronology have as their overiding goal the simple yet scientifically elusive objective of “getting it right”.

High resolution stratigraphy of channelized deposits on a continental slope setting with sea-floor topography controlled by halokinetics, uppermost cretaceous, Espírito Santo offshore basin, Brazil

2020 ◽  
Vol 103 ◽  
pp. 102721
Author(s):  
Igor Nascimento ◽  
Jorge Picanço de Figueiredo ◽  
Nilo C. de Azambuja Filho ◽  
João Paulo Oliveira ◽  
Ana Carolina Araújo ◽  
...  
Keyword(s):  
High Resolution ◽  
Continental Slope ◽  
Espírito Santo ◽  
Sea Floor ◽  
Espirito Santo

scholarly journals Integrated high-resolution stratigraphy of a Middle to Late Miocene sedimentary sequence in the central part of the Vienna Basin

2011 ◽  
Vol 62 (2) ◽  
pp. 155-169 ◽  
Author(s):  
Wieske Paulissen ◽  
Stefan Luthi ◽  
Patrick Grunert ◽  
Stjepan Ćorić ◽  
Mathias Harzhauser
Keyword(s):  
High Resolution ◽  
Late Miocene ◽  
Pannonian Basin ◽  
Foreland Basin ◽  
Integrated Approach ◽  
Tectonic Activity ◽  
Sedimentary Sequence ◽  
Vienna Basin ◽  
Lake Pannon ◽  
North Alpine Foreland Basin

Integrated high-resolution stratigraphy of a Middle to Late Miocene sedimentary sequence in the central part of the Vienna BasinIn order to determine the relative contributions of tectonics and eustasy to the sedimentary infill of the Vienna Basin a high-resolution stratigraphic record of a Middle to Late Miocene sedimentary sequence was established for a well (Spannberg-21) in the central part of the Vienna Basin. The well is located on an intrabasinal high, the Spannberg Ridge, a location that is relatively protected from local depocentre shifts. Downhole magnetostratigraphic measurements and biostratigraphical analysis form the basis for the chronostratigraphic framework. Temporal gaps in the sedimentary sequence were quantified from seismic data, well correlations and high-resolution electrical borehole images. Stratigraphic control with this integrated approach was good in the Sarmatian and Pannonian, but difficult in the Badenian. The resulting sedimentation rates show an increase towards the Upper Sarmatian from 0.43 m/kyr to > 1.2 m/kyr, followed by a decrease to relatively constant values around 0.3 m/kyr in the Pannonian. The sequence reflects the creation of accommodation space during the pull-apart phase of the basin and the subsequent slowing of the tectonic activity. The retreat of the Paratethys from the North Alpine Foreland Basin during the Early Sarmatian temporarily increased the influx of coarsergrained sediment, but eventually the basin acted mostly as a by-pass zone of sediment towards the Pannonian Basin. At a finer scale, the sequence exhibits correlations with global eustasy indicators, notably during the Sarmatian, the time of greatest basin subsidence and full connectivity with the Paratethyan system. In the Pannonian the eustatic signals become weaker due to an increased isolation of the Vienna Basin from Lake Pannon.

Settlement down again patterns of a carbonated platform following up a sedimentary crisis : example of the middle-late Jurassic boundary in the southeastern part of the Paris Basin

2004 ◽  
Vol 175 (3) ◽  
pp. 289-302 ◽  
Author(s):  
Sébastien Lorin ◽  
Philippe Courville ◽  
Pierre-Yves Collin ◽  
Jacques Thierry ◽  
Anthony Tort
Keyword(s):  
Late Jurassic ◽  
Regional Scale ◽  
High Energy ◽  
Depositional Environments ◽  
Low Energy ◽  
Tectonic Activity ◽  
Paris Basin ◽  
Marine Waters ◽  
Carbonate Production ◽  
Lithostratigraphic Units

Abstract Following a sedimentary crisis which begins in the late Lower Callovian and spans all the early Oxfordian, the settlement down patterns of a platform with carbonated sedimentation are analysed in a southeastern area of the Paris Basin (fig. 1). Ten lithostratigraphic units (reefal formations, associated bioclastic facies and marly distal lateral facies ; fig. 2) are defined (fig. 3). New ammonite and brachiopod faunas, collected in situ, allow to date accurately the sedimentary units with a precision matching an ammonite subzone of the standard bio-chronostratigraphic scale (fig. 4) of the middle-late Oxfordian (from the Parandieri Subzone, at the base of the Transversarium Zone, to the Planula Subzone, at the top of the Planula Zone). The sedimentologic analysis coupled with the study of the benthic and pelagic faunal communities allow to define twelve type-facies (tabl. I and II). Regrouped into three associations, these characterise depositional environments which occur in succession, following three platform models (fig. 5). As witnesses of the evolution of the accomodation/sedimentation ratio, the resulting time succession of sedimentary bodies shows a depositional dynamics organised into three sequence tracks (fig. 5 and 6) : – a retrogradation phase is characterised by a moderately deep and open platform, dominated by low energy and marly sedimentation, which ranges from the Middle Oxfordian (Plicatilis Zone and Transversarium Zone) to the lowermost late Oxfordian (Bifurcatus Zone) ; – during the late Oxfordian (Bimammatum Zone, from the Semimammatum Subzone to the Bimammatum Subzone) an aggradation phase corresponds to the installation of three successive shallow platforms with contrasted morphology. Indicating the re-initiation of carbonated production, these platforms are well limited and represent high energy shallows with reef buildings, which lateraly grade into dismantling bioclastic faciès, then secondly and more laterally again into low energy and medium deep marly facies ; – the upper part of the late Oxfordian (Hauffianum Subzone, in the uppermost Bimammatum Zone, and Planula Zone) shows the wide extent of a low energy and morphologically very little contrasted distal platform. This one has a high potential of carbonated production characterised by bioclastic, oolitic and micritic facies which illustrate a progradation phase ; such a phase proceeds in the early Kimmeridgian. The collected data and the corresponding phenomenons pointed out on this area of the southeastern border of the Paris Basin are discussed and replaced in the general framework of the sedimentary, biologic, palaeogeographic and palaeoclimatic events henceforth recognised at the middle-late Jurassic boundary on the peri-Tethyan intracratonic domains of western Europe. The demise of the carbonate production seems to be correlated with a global cooling of both marine waters and atmosphere, which is considered as a limiting factor. During the Middle Oxfordian, the re-initiation of carbonate production with the developement of reef buildings should correspond to a large scale warming of the marine waters still observed elswhere on the Russian Platform, in the North Sea and in the Paris Basin. However, the geographic distribution and the chronologic succession of the facies and deduced palaeoenvironments is probably equally related to a synsedimentary tectonic activity which operates as a favorable factor at both a local and regional scale.

scholarly journals 888–444 Ma Global Plate Tectonic Reconstruction With Emphasis on the Formation of Gondwana

2021 ◽  
Vol 9 ◽  
Author(s):  
Christian Vérard
Keyword(s):  
Plate Tectonics ◽  
Additional Data ◽  
Continuous Process ◽  
Tectonic Activity ◽  
Plate Tectonic ◽  
Sea Floor ◽  
Tectonic Model ◽  
The Earth ◽  
Tectonic Reconstruction ◽  
Accretion Rates

The formation of Gondwana results from a complex history, which can be linked to many orogenic sutures. The sutures have often been gathered in the literature under broad orogenies — in particular the Eastern and Western Pan-African Orogenies — although their ages may vary a lot within those wide belts. The Panalesis model is a plate tectonic model, which aims at reconstructing 100% of the Earth’s surface, and proposes a geologically, geometrically, kinematically, and geodynamically coherent solution for the evolution of the Earth from 888 to 444 Ma. Although the model confirms that the assembly of Gondwana can be considered complete after the Damara and Kuunga orogenies, it shows above all that the detachment and amalgamation of “terranes” is a roughly continuous process, which even persisted after the Early Cambrian. By using the wealth of Plate Tectonics, the Panalesis model makes it possible to derive numerous additional data and maps, such as the age of the sea-floor everywhere on the planet at every time slice, for instance. The evolution of accretion rates at mid-oceanic ridges and subduction rates at trenches are shown here, and yields results consistent with previous estimates. Understanding the variation of the global tectonic activity of our planet through time is key to link plate tectonic modeling with other disciplines of Earth sciences.

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