Seismic Acoustic Impedance: An Indicator for Deep-Water Depositional Processes

2011 ◽  
pp. 698-720
Author(s):  
Jiajie (Jeff) Chen
Keyword(s):  
Deep Water ◽  
Acoustic Impedance ◽  
Depositional Processes

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)

scholarly journals Fringe or background: Characterizing deep-water mudstones beyond the basin-floor fan sandstone pinchout

2020 ◽  
Vol 90 (12) ◽  
pp. 1678-1705
Author(s):  
Kévin Boulesteix ◽  
Miquel Poyatos-Moré ◽  
David M. Hodgson ◽  
Stephen S. Flint ◽  
Kevin G. Taylor
Keyword(s):  
Deep Water ◽  
Turbidity Currents ◽  
Stratigraphic Correlation ◽  
Low Density ◽  
Karoo Basin ◽  
Depositional Processes ◽  
Stratigraphic Architecture ◽  
Sand Supply ◽  
Stacking Pattern ◽  
Basin Floor

ABSTRACT Mud dominates volumetrically the fraction of sediment delivered and deposited in deep-water environments, and mudstone is a major component of basin-floor successions. However, studies of basin-floor deposits have mainly focused on their proximal sandstone-prone part. A consequent bias therefore remains in the understanding of depositional processes and stratigraphic architecture in mudstone-prone distal settings beyond the sandstone pinchouts of basin-floor fans. This study uses macroscopic and microscopic descriptions of over 500 m of continuous cores from research boreholes from the Permian Skoorsteenberg Formation of the Karoo Basin, South Africa, to document the sedimentology, stratigraphy, and ichnology of a distal mudstone-prone basin-floor succession. Very thin- to thin-bedded mudstones, deposited by low-density turbidity currents, stack to form bedsets bounded by thin packages (< 0.7 m thick) of background mudstones. Genetically related bedsets stack to form bedset packages, which are bounded by thicker (> 0.7 m thick) background mudstones. Stratigraphic correlation between cores suggests that bedsets represent the distal fringes of submarine fan lobe elements and/or lobes, and bedset packages represent the distal fringes of lobe complexes and/or lobe complex sets. The internal stacking pattern of bedsets and bedset packages is highly variable vertically and laterally, which records dominantly autogenic processes (e.g., compensational stacking, avulsion of feeder channels). The background mudstones are characterized by remnant tractional structures and outsize particles, and are interpreted as deposited from low-density turbidity currents and debris flows before intense biogenic reworking. These observations challenge the idea that mud accumulates only from hemipelagic suspension fallout in distal basin-floor environments. Thin background mudstones separating bedsets (< 0.7 m thick) are interpreted to mainly represent autogenically driven lobe abandonment due to up-dip channel avulsion. The thicker background mudstones separating bedset packages (> 0.7 m thick) are interpreted to dominantly mark allogenically driven regional decrease of sand supply to the basin floor. The recognition of sandstone-prone basin-floor fans passing into genetically linked distal fringe mudstones suggests that submarine lobes are at least ∼ 20 km longer than previously estimated. This study provides sedimentological, stratigraphic, and ichnological criteria to differentiate mudstones deposited in different sub-environments in distal deep-water basin-floor settings, with implications for the accurate characterization of basin-floor fan architecture, and their use as archives of paleoenvironmental change.

Late Pleistocene Deep-Water Stratigraphy and Depositional Processes, Offshore Trinidad and Tobago

2000 ◽  
pp. 104-115 ◽  
Author(s):  
Tonya R. Brami ◽  
Carlos Pirmez ◽  
Curtis Archie ◽  
Sookdeo Heeralal ◽  
Kelly L. Holman
Keyword(s):  
Trinidad And Tobago ◽  
Late Pleistocene ◽  
Deep Water ◽  
Depositional Processes

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>

Depositional processes of black shales in deep water

2001 ◽  
Vol 18 (4) ◽  
pp. 491-498 ◽  
Author(s):  
D.A.V Stow ◽  
A.-Y Huc ◽  
P Bertrand
Keyword(s):  
Deep Water ◽  
Black Shales ◽  
Depositional Processes

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>

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