Deep-water syn-rift sedimentary response to alternating Late Quaternary palaeoenvironments in the Gulf of Corinth (Greece)

2021 ◽  
Author(s):  
Natacha Fabregas ◽  
Sofia Pechlivanidou ◽  
Robert Gawthorpe ◽  
Mary Ford ◽  
Richard Collier
Keyword(s):  
High Resolution ◽  
Deep Water ◽  
Late Quaternary ◽  
Discrete Events ◽  
Climatic Fluctuations ◽  
Fine Grained ◽  
Sea Level Fluctuations ◽  
Gulf Of Corinth ◽  
Depositional Processes ◽  
Unit Scale

<p>Relatively few detailed studies exist of rift axis depositional systems and the controls on their sedimentology and stratigraphy. Cores from the IODP Expedition 381 (Corinth Active Rift Development) provide a continuous high resolution stratigraphic record of depositional processes operating within this deep-water rift. During the Late Quaternary, the Gulf of Corinth alternated between marine and isolated/non-marine conditions due to intermittent connection with the open ocean across a sill driven by climate-related sea-level fluctuations. In this study we performed bed scale logging of the sedimentary deposits within the eastern Gulf of Corinth in order to understand key controls on sedimentation during the Late Quaternary. High resolution, mm-scale analysis was performed on the first 300 m of core from Site M0079 that records the last two glacial-interglacial cycles and the Holocene (Marine Isotope Stages 1 to 7). The succession is dominated by fine-grained gravity flows (event beds) and hemipelagic sediments. Event beds result from discrete events that interrupt/overprint ongoing low energy sedimentation. As such, these have been abstracted in order to define three main sedimentary unit types. Unit-scale logging was extended to the rest of the succession and to the other drill sites to build a stratigraphic and depositional model covering the last ca. 700 kyr of deposition. Our results show that during interglacial periods (i.e. marine conditions), the sediment record consists mainly of highly bioturbated mud with rarer occurrences of coarser grained sediment. Sedimentary structures and identifiable event beds have largely been lost due to the high degree of bioturbation. In contrast, during glacial periods (i.e. isolated/semi-isolated lake conditions) the deposits are well bedded with a low bioturbation index and background muds alternate with event beds. Transitional strata, between marine and non-marine units, show finely laminated beds rich in aragonite, often becoming more organic rich toward the top. The deepest parts of the core penetrate slumped units and thicker gravity flow deposits. This study allows us to recognise the response to high frequency climatic fluctuations recorded in the sedimentary succession of this deep-water rift.</p>

Variability of fine-grained basin floor turbidites and evaluation of controls on their development: Late Pleistocene, Gulf of Corinth, Greece

2020 ◽  
Author(s):  
Natacha Fabregas ◽  
Robert Gawthorpe ◽  
Mary Ford ◽  
Martin Muravchik ◽  
Sofia Pechlivanidou ◽  
...  
Keyword(s):  
Late Pleistocene ◽  
Deep Water ◽  
Rift Basins ◽  
Fine Grained ◽  
Sea Level Fluctuations ◽  
Sediment Routing ◽  
Gulf Of Corinth ◽  
Depositional Processes ◽  
Energy Flows ◽  
Basin Floor

<p>The Gulf of Corinth is one of the World’s fastest extending continental rift basins. During the Late Pleistocene, it alternated between marine and lacustrine conditions due to climate-driven sea-level fluctuations connecting or isolating/semi-isolating it from the open ocean. Core from IODP Expedition 381 (Corinth Active Rift Development) provide a continuous record of depositional processes operating within this deep-water rift and the interaction of tectonic and climate drivers controlling deep-water deposition over the Middle to Late Pleistocene. Subaqueous sediment density flows affect the Gulf of Corinth and are classified either by physical flow properties and grain support mechanisms or by depositional processes. Existing classifications mainly describe deposits from decimetre to 10’s of meter scale with an emphasis on sandy beds. Thinner (millimetre to centimetre scale) and finer (muddy to sandy) subaqueous sedimentary density flows beds are understudied. Low energy flows and tail of flow processes need a better understanding and are the target of this work. The aim of this study is to characterise the variability of fine-grained subaqueous sedimentary gravity flow deposits and the controls on their development based on core data from Site M0079 (IODP Expedition 381).  This site is located in the deepest part of the Gulf of Corinth (857 m water depth), in the most distal part of the sediment routing system. Analyses were performed within a 100 m interval covering Marine Isotope Stages 6 and 7 (from ~130 to ~250 ka). Detailed, sub-centimetre visual logging recorded over 2 000 beds classified according to (1) the presence/absence of a coarse base, (2) the grain-size (silty or sandy) of the base (if any), (3) the presence/absence of laminations within the muddy intervals, (4) sedimentary structures. The bed types reflect the diversity of the sedimentary processes and the subaqueous sediment density flows are thus organised within the depositional model. Bed frequency analysis provides insight into the variability between marine and lacustrine conditions. Relative chemical composition obtained from high resolution (2 mm) X-ray fluorescence scanning is used: (1) to examine the interactions between tail of the flow and background sedimentation in the basin and (2) to assess the provenance of the sediments.</p>

scholarly journals Markov chains and entropy tests in genetic-based lithofacies analysis of deep-water clastic depositional systems

2016 ◽  
Vol 8 (1) ◽  
pp. 45-51
Author(s):  
Szabolcs Borka
Keyword(s):  
Markov Chains ◽  
Deep Water ◽  
Pannonian Basin ◽  
Depositional Environments ◽  
Structural Elements ◽  
Chi Square ◽  
Fine Grained ◽  
Hydrocarbon Reservoir ◽  
Depositional Processes ◽  
Chi Square Test

AbstractThe aim of this study was to examine the relationship between structural elements and the so-called genetic lithofacies in a clastic deep-water depositional system. Process-sedimentology has recently been gaining importance in the characterization of these systems. This way the recognized facies attributes can be associated with the depositional processes establishing the genetic lithofacies. In this paper this approach was presented through a case study of a Tertiary deep-water sequence of the Pannonian-basin.Of course it was necessary to interpret the stratigraphy of the sequences in terms of “general” sedimentology, focusing on the structural elements. For this purpose, well-logs and standard deep-water models were applied.The cyclicity of sedimentary sequences can be easily revealed by using Markov chains. Though Markov chain analysis has broad application in mainly fluvial depositional environments, its utilization is uncommon in deep-water systems. In this context genetic lithofacies was determined and analysed by embedded Markov chains. The randomness in the presence of a lithofacies within a cycle was estimated by entropy tests (entropy after depositional, before depositional, for the whole system). Subsequently the relationships between lithofacies were revealed and a depositional model (i.e. modal cycle) was produced with 90% confidence level of stationarity. The non-randomness of the latter was tested by chi-square test.The consequences coming from the comparison of “general” sequences (composed of architectural elements), the genetic-based sequences (showing the distributions of the genetic lithofacies) and the lithofacies relationships were discussed in details. This way main depositional channel has the best, channelized lobes have good potential hydrocarbon reservoir attributes, with symmetric alternation of persistent fine-grained sandstone (Facies D) and muddy fine-grained sandstone with traction structures (Facies F)

Controls on stratigraphic variability in a semi-closed rift basin over the Late Quaternary, Gulf of Corinth, Greece

2020 ◽  
Author(s):  
Sofia Pechlivanidou ◽  
Spyros Sergiou ◽  
Maria Geraga ◽  
Robert Gawthorpe ◽  
Dimitra Antoniou ◽  
...  
Keyword(s):  
Sea Level ◽  
Late Quaternary ◽  
Ct Scanning ◽  
Rift Basin ◽  
Last Glacial Period ◽  
Corinth Gulf ◽  
Fine Grained ◽  
Gulf Of Corinth ◽  
Cyclic Variations ◽  
The Last Glacial

<p>The Corinth Gulf is a semi-closed active rift basin, which alternated between marine and isolated/semi-isolated conditions as sea level fluctuated with respect to basin sills during Quaternary glacial/interglacial cycles. Results from the recent IODP Expedition 381 reveal cyclic variations of 10s-100s of kyr in sedimentation rates and basin paleoenvironment. In this study we investigate the controls on stratigraphic development of the Corinth basin during the last eustatic cycle and the Holocene based on core data from the IODP Expedition 381 Site M0079. We perform a multi-proxy analysis of the upper ~200 mbsf of core covering Marine Isotope Stages (MIS) 1-5 (i.e. last 130 kyr). Our analyses include grain size and micropaleontological (foraminifera) analyses at regular intervals (~0.5 m), Computed Tomography (CT-scanning) of selected u-channels and specific microscopic work (smear slides, SEM) on targeted samples. Our results show pronounced variability in sedimentation patterns during the isolated/semi-isolated phases compared to the marine intervals. Low density, thinly bedded and laminated muds alternating with high density homogenous mud beds and occasionally sandy, organic rich beds prevail during isolated/semi-isolated conditions. In contrast, homogenous and/or highly bioturbated successions characterize the marine sequences. The transitions from marine to isolated/semi-isolated conditions and vise-versa are often associated with authigenic carbonate deposition. Fine grained sediments (sand < 10%) dominate both the marine and the isolated sequences. Nevertheless, sandy turbidites (sand > 10%) are also present and are more often observed in the isolated phases, likely associated with climatic-driven changes in erosional processes onshore. Our analysis reveals short-lived isolated/semi-isolated sub-phases within the lower marine interval corresponding to the MIS5b and MIS5d lowstands. Short marine spikes also interrupt the isolated/semi-isolated conditions of the last glacial period indicating temporary sea level rises within MIS3. Overall, the marine intervals display significant paleoenvironmental differences although they share similar sedimentary patters. In particular, we observe more diverse palaeoceanographic conditions in the MIS5 marine sub-phases compared to the MIS1, especially regarding temperature and eutrophication levels of the water column.  </p>

New insights into the internal structure of Turbidite deposits from physical modelling of relevant erosional and depositional processes

2020 ◽  
Author(s):  
Jonathan Wilkin
Keyword(s):  
High Resolution ◽  
Deep Water ◽  
Experimental Studies ◽  
Turbidity Currents ◽  
Densimetric Froude Number ◽  
Lateral Confinement ◽  
Transition Zones ◽  
Depositional Processes ◽  
The Impact ◽  
Lower Slope

<p>Results are presented from the current experimental campaign which aims to observe the character of supercritical turbidity currents and other supercritical sediment gravity flows (SGFs) as they respond to morphological transition zones, e.g. slope breaks and losses of lateral confinement. This experimental setup aims to reproduce lower slope, channel-lobe transition zone, and, proximal lobe conditions, in order to be analogous to conditions found within deep-marine sedimentary environments such as those found within foreland basins, and on passive margins. Of particular interest is the sedimentological expression of these systems, how sedimentological variability arises in the form of sediment waves and scour fields, and how does an understanding of current dynamics help in the prediction of the internal structures of these features. Thus, this study will yield new data on how turbidity currents impact multi-layered sedimentary beds and determine parametric controls on erosion, deposition and bed restructuring processes. Turbidity currents are scaled via dimensionless parameters representing prevalent flow (e.g. Reynolds, Densimetric Froude Number, and Shields Numbers) and sedimentary (e.g. Rouse and Reynolds Particle Numbers) conditions, following the scaling techniques of de Leeuw et al., (2016) which have now been tested in numerous experimental studies e.g. Pohl et al., 2019.</p><p> </p><p>Investigating how varying experimental conditions such as current parameters, severity of breaks in-slope, and, losses of lateral confinement impact the resulting depositional signature of lower slope, and channel-lobe transition zones. Of particular interest is the impact of previously developed bedforms upon current dynamics which will be studied via UVP and ADV measurements, as well as through the application of digital elevation models (DEM), which will be used to understand how systems evolve over multiple runs. DEM models will be generated using a photogrammetry technique capable of producing a high-resolution model (±2mm). The results of which will then be linked to synchronous sedimentological packages – both on the modern seafloor and preserved within ancient geological outcrops – with the aim of enhancing the predictive sedimentological concepts applied to these systems when being interpreted within the subsurface.</p><p> </p><p>A seafloor study will focus upon supercritical bedforms generated by SGFs upon a deep-water slope and terrace located offshore of Senegal, West Africa. Combining seafloor seismic images, high-resolution sparker data, and drop cores taken from deep water channels, and overbanks. Through the interpretation of this dataset, it will be possible to understand the sedimentological variability of bedforms present on this slope system and allude to the flow conditions that led to their formation.</p><p> </p><p>References</p><p>de Leeuw, J., Eggenhuisen, J.T., Cartigny, M.J.B., 2016. Morphodynamics of submarine channel inception revealed by new experimental approach. Nat. Commun. 7. https://doi.org/10.1038/ncomms10886</p><p>Pohl, F., Eggenhuisen, J.T., Cartigny, M.J.B., Tilston, M., de Leeuw, J. & Hermidas, N. (in review). The influence of a slope break on turbidite deposits: an experimental investigation. Marine Geology.</p>

Turbidite origin of some laminated mudstones

1972 ◽  
Vol 109 (2) ◽  
pp. 115-126 ◽  
Author(s):  
David J. W. Piper
Keyword(s):  
Deep Water ◽  
Deep Sea ◽  
Careful Examination ◽  
Turbidity Currents ◽  
Granular Bed ◽  
Terrigenous Sediment ◽  
Fine Grained ◽  
Depositional Processes ◽  
Lower Palaeozoic

SummaryMany deep water marine muds, including lower Palaeozoic mudstones from Britain, have thin graded beds in which mud and silt laminae alternate, with the silt becoming finer and less abundant upwards. Of the known deep-sea depositional processes, turbidity currents are the most likely cause of such graded laminated beds. The lamination may be produced by alternating cohesive and granular bed conditions. Much more careful examination of laminated fine grained terrigenous sediment is needed.

scholarly journals Late Quaternary paleoseismic sedimentary archive from deep central Gulf of Corinth: time distribution of inferred earthquake-induced layers

2014 ◽  
Vol 56 (6) ◽  
Author(s):  
Corina Campos ◽  
Christian Beck ◽  
Christian Crouzet ◽  
Eduardo Carrillo ◽  
Aurélien Van Welden ◽  
...  
Keyword(s):  
Time Distribution ◽  
Late Quaternary ◽  
Coarse Grained ◽  
Lower Term ◽  
Piston Core ◽  
Magnetic Susceptibility Anisotropy ◽  
North Central ◽  
Fine Grained ◽  
The North ◽  
Gulf Of Corinth

<p>A sedimentary archive corresponding to the last 17 cal kyr BP has been studied by means of a giant piston core retrieved on board R/V MARION-DUFRESNE in the North Central Gulf of Corinth. Based on previous methodological improvements, grain-size distribution and Magnetic Susceptibility Anisotropy (MSA) have been analysed in order to detect earthquake-induced deposits. We indentified 36 specific layers -Homogenites+Turbidites (HmTu) - intercalated within continuous hemipelagictype sediments (biogenic or bio-induced fraction and fine-grained siliciclastic fraction). The whole succession is divided into a non-marine lower half and a marine upper half. The “events” are distributed through the entire core and they are composed of two terms: a coarse-grained lower term and an upper homogeneous fine-grained term, sharply separated. Their average time recurrence interval could be estimated for the entire MD01-2477 core. The non-marine and the marine sections yielded close estimated values for event recurrence times of around 400 yrs to 500 yrs.</p>

High Resolution Low Loss Microscopy of Crystalline Surfaces

1980 ◽  
Vol 38 ◽  
pp. 162-163
Author(s):  
William Krakow ◽  
Alec N. Broers
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Surface Topography ◽  
Secondary Electron ◽  
Objective Lens ◽  
Surface Imaging ◽  
Low Loss ◽  
Fine Grained ◽  
Scanning Electron ◽  
Crystalline Surfaces

Low-loss scanning electron microscopy can be used to investigate the surface topography of solid specimens and provides enhanced image contrast over secondary electron images. A high resolution-condenser objective lens has allowed the low-loss technique to resolve separations of Au nucleii of 50Å and smaller dimensions of 25Å in samples coated with a fine grained carbon-Au-palladium layer. An estimate of the surface topography of fine grained vapor deposited materials (20 - 100Å) and the surface topography of underlying single crystal Si in the 1000 - 2000Å range has also been investigated. Surface imaging has also been performed on single crystals using diffracted electrons scattered through 10−2 rad in a conventional TEM. However, severe tilting of the specimen is required which degrades the resolution 15 to 100 fold due to image forshortening.

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