scholarly journals Submarine mass failures as tsunami sources: their climate control

2010 ◽  
Vol 368 (1919) ◽  
pp. 2417-2434 ◽  
Author(s):  
D. R. Tappin
Keyword(s):  
Submarine Canyon ◽  
Coarse Grained ◽  
Sediment Type ◽  
Potential Hazard ◽  
Convergent Margins ◽  
Climate Control ◽  
River Deltas ◽  
Storm Waves ◽  
Depositional Processes ◽  
Climate Controls

Recent research on submarine mass failures (SMFs) shows that they are a source of hazardous tsunamis, with the tsunami magnitude mainly dependent on water depth of failure, SMF volume and failure mechanism, cohesive slump or fragmental landslide. A major control on the mechanism of SMFs is the sediment type, together with its post-depositional alteration. The type of sediment, fine- or coarse-grained, its rate of deposition together with post-depositional processes may all be influenced by climate. Post-depositional processes, termed sediment ‘preconditioning’, are known to promote instability and failure. Climate may also control the triggering of SMFs, for example through earthquake loading or cyclic loading from storm waves or tides. Instantaneous triggering by other mechanisms such as fluid overpressuring and hydrate instability is controversial, but is here considered unlikely. However, these mechanisms are known to promote sediment instability. SMFs occur in numerous environments, including the open continental shelf, submarine canyon/fan systems, fjords, active river deltas and convergent margins. In all these environments there is a latitudinal variation in the scale of SMFs. The database is limited, but the greatest climate influence appears to be in high latitudes where glacial/interglacial cyclicity has considerable control on sedimentation, preconditioning and triggering. Consideration of the different types of SMFs in the context of their climate controls provides additional insight into their potential hazard in sourcing tsunamis. For example, in the Atlantic, where SMFs are common, the tsunami hazard under the present-day climate may not be as great as their common occurrence suggests.

Morphology, architecture, and evolutionary processes of the Zhongjian Canyon between two carbonate platforms, South China Sea

2018 ◽  
Vol 6 (4) ◽  
pp. SO1-SO15 ◽  
Author(s):  
Yintao Lu ◽  
Wei Li ◽  
Shiguo Wu ◽  
Bryan T. Cronin ◽  
Fuliang Lyu ◽  
...  
Keyword(s):  
Seismic Data ◽  
Large Scale ◽  
Middle Miocene ◽  
Sedimentary Environment ◽  
Submarine Canyon ◽  
High Amplitude ◽  
Seismic Facies ◽  
Coarse Grained ◽  
Carbonate Platforms ◽  
Depositional Processes

Two isolated Neogene carbonate platforms (Xisha and Guangle carbonate platforms) have developed in the rifted uplifts since the Early Miocene. A large-scale submarine canyon system, the Zhongjian Canyon (ZJC), has developed in the tectonic depression between the two platforms since the Middle Miocene. High-resolution bathymetry data and 2D and 3D seismic data reveal the existence of the ZJC on the present seafloor, as well as in Neogene intervals. It exhibits typical characteristics of deepwater canyons that cut the surrounding rocks and indicate strong erosional features. The ZJC resulted from northwest–southeast strike-slip fault activities during synrift and postrift stages, and it periodically grew during the development of carbonate platforms since the Middle Miocene. We identified four cycles of parallel to subparallel high amplitude and dim reflectors in seismic data, which we interpreted as alternating canyon fill, based on the interpretation of seismic facies. Thus, the sedimentary evolution of the ZJC can be divided into four typical stages, which were in the Middle Miocene, Late Miocene, Early Pliocene, and Pleistocene. Considering the tectonic background of the carbonate platforms, as well as the on-going igneous activities, the sediment filling the canyon could be derived from a mixture of carbonate clasts, igneous clasts, mud, and silt. The laminar high-amplitude reflectors and dim-reflector package represented a fining-upward sedimentary cycle. The coarse-grained sediment in canyon fillings could be turbidites, carbonate debrites, and even igneous clasts. In contrast, the fine-grained sediment is likely to be dominated by pelagic to hemipelagic mud, and silt. This case study describes a deepwater canyon under a carbonate-dominated sedimentary environment and has significant implications for improving our knowledge of periplatform slope depositional processes. Furthermore, the insight gained into periplatform slope depositional processes can be applied globally.

Depositional conditions at the Aptian Pre-salt margins: evidence from quantitative petrography and textural analysis of the Mucuri Member, Espírito Santo Basin, Brazil

2021 ◽  
pp. petgeo2020-112
Author(s):  
G. Pantopoulos ◽  
G. K. L. Orita ◽  
G. Armelenti ◽  
C. E. Althaus ◽  
J. Kuchle ◽  
...  
Keyword(s):  
Grain Size ◽  
Settling Velocity ◽  
Textural Analysis ◽  
Coastal Sediments ◽  
Coarse Grained ◽  
Sediment Type ◽  
Espírito Santo ◽  
Depositional Processes ◽  
Depositional Settings ◽  
Espirito Santo

Aptian siliciclastic onshore deposits of the Mucuri Member are important reservoirs in the Espírito Santo Basin (eastern Brazil). A detailed quantitative petrographic and textural analysis of well core samples was performed in order to unravel their depositional processes and conditions, in relation to previously proposed depositional models. The results allowed the differentiation between two groups of sandstone samples, characterized by different textural characteristics associated to different depositional processes and environments within the Mucuri depositional system. Fluvial sandstones are represented by medium- to coarse-grained, poorly-sorted arkoses, rich in plutonic rock fragments and feldspar grains, mainly transported by traction. Coastal-lacustrine sandstones correspond to very fine- to fine-grained, moderately-sorted micaceous arkoses, mainly transported in suspension. The application of a discriminant function based on grain size parameters validated previously proposed depositional settings for the studied sample groups. The combination of grain size and shape data revealed differences in hydraulic equivalence and shape between grains from different depositional settings. In terms of hydraulic equivalence, micas in the fluvial sediments present lower settling velocity values, in contrast with the relatively large mica grains in the coastal sediments, which are hydraulically equivalent with the associated quartz and feldspar grains. The results of this study provide key information regarding depositional conditions (transportation mechanisms, grain settling velocity and mineral hydraulic fractionation) at the margins of the Aptian Pre-salt system, which can constrain the hydrological conditions and the sediment type available for distal lacustrine areas.

Multi-scale influence of topography on shallow-marine successions associated with long-term transgressions

2021 ◽  
Author(s):  
Miquel Poyatos-Moré ◽  
Ernesto Schwarz ◽  
Salvador Boya ◽  
Luz Elena Gomis-Cartesio ◽  
Ivar Midtkandal
Keyword(s):  
Regional Scale ◽  
Coarse Grained ◽  
Continuous Exposure ◽  
Entire Study ◽  
Shallow Marine ◽  
Sedimentary Characteristics ◽  
Multi Scale ◽  
Depositional Processes ◽  
Mouth Bars

<p>Thick shallow-marine successions associated with long-term transgressions are less well known than their thin, well-sorted counterparts, widely studied due to their potential to form good reservoirs. In these successions, particularly in storm-dominated examples, bioturbation can obliterate primary sedimentary characteristics, making stacking patterns and sequences difficult to define, and challenging our understanding of the main controls in their resulting depositional architecture. This study presents an example from the Jurassic of the Neuquén Basin (Argentina), with the aim to: a) refine the depositional model of a thick, shallow-marine succession associated with a long-term, early post-rift transgression, b) constrain multi-scale controls on stratigraphic architecture and lateral facies variability, and c) discuss their preservation and response to post-depositional processes. To do this, a <300 m-thick succession has been studied along a >10 km continuous exposure, with mapping, sedimentary logging and correlation of stratigraphic units, integrated with subsurface, biostratigraphic and ichnological data. The succession shows an overall retrogradational-aggradational-retrogradational stacking pattern, with several higher frequency regressive units (parasequences and parasequence sets, PSS). The lower part (PSS I) comprises laterally-discontinuous (10's of m) mouth-bars and distributary channel fills, dominated by several m-thick coarsening- and fining-up sandstone packages and m-scale erosive conglomeratic lenses. Above these, the succession (PSS II-IV) is composed by laterally-continuous (>100's of m) storm-dominated lower-shoreface to upper-offshore deposits, dominated by <1m-thick fine-grained and highly bioturbated tabular muddy sandstones and sandy mudstones, with rarely-preserved HCS and bioclastic-rich limestones; their internal characteristics and bed boundaries are diffuse due to pervasive bioturbation, suggesting overall low sedimentation rates and recurrent periods of colonization. The coarse-grained nature and lithology of the mouth bars and channel fills in the lower succession (PSS I) are consistent with a proximal sediment source, associated with erosion of intra-basinal highs. Its variable thickness, lateral distribution and onlap against underlying syn-rift deposits demonstrates partial infill of localized higher-accommodation areas. The well-sorted and finer-grained nature of the shoreface-offshore strata the middle and upper succession (PSS II-IV) indicates a more mature, distal source, with sediment redistributed by longshore currents, and then intensely bioturbated. These deposits display well-defined parasequences internally composed of laterally-continuous bedsets (<5 m-thick). They extend along the entire study area, but show a significant vertical thickness variability. The integration of outcrop and subsurface data mapping (well and seismic) reveals this variability records the stratigraphic response of transgression over a complex, regional-scale ramp-step and underfilled rift topography, which controlled the location of main thickness and facies changes, and promoted areas of favored biogenic reworking. This study offers new insights in how to interpret thick transgressive successions based on primary depositional mechanisms and postdepositional processes, and provides useful tools to understand and predict the nature and potential preservation of these deposits in limited subsurface datasets.</p>

COOL-WATER CARBONATE FACIES PATTERNS AND DIAGENESIS-THE KEY TO THE GIPPSLAND BASIN 'VELOCITY PROBLEM'

1998 ◽  
Vol 38 (1) ◽  
pp. 137 ◽  
Author(s):  
D.A. Feary ◽  
T.S. Loutit
Keyword(s):  
Submarine Canyon ◽  
Velocity Variation ◽  
Carbonate Facies ◽  
Seismic Attribute ◽  
Seismic Reflection Data ◽  
Cool Water ◽  
Depositional Processes ◽  
Attribute Analysis ◽  
Gippsland Basin ◽  
Water Carbonate

Throughout much of the exploration history of the offshore Gippsland Basin it has been difficult to achieve acceptable accuracy or precision for time-depth conversions beneath the stratigraphically and sonically complex Seaspray Group, overlying exploration targets within the hydrocarbon-rich Latrobe Group. A regional seismic stratigraphic and seismic attribute analysis of the Oligocene-Recent Seaspray Group has been carried out as the first step towards resolving this long-standing Gippsland Basin 'velocity problem'.High-resolution 2D seismic reflection data and downhole logs were used to determine the depositional history and sequence characteristics of the Seaspray Group. This analysis was based on the premise that velocity variation must be related to, or controlled by, the nature and distribution of the dominantly cool-water carbonate facies of the Seaspray Group, and that solution of the velocity problem must be based on understanding the particular depositional and geochemical characteristics of cool-water carbonates.Detailed seismic stratigraphic analysis of the G92A dataset shows that the 16 unconformity-bounded seismic sequences within the Seaspray Group form four mega-sequences, each separated by major erosional (channel-cutting) events, with sequences reflecting variable sediment inputs from northeasterly and southwesterly sources. Seaspray Group characteristics result from interaction of complex depositional and post-depositional processes, including river incision, submarine canyon erosion, slumping, subaerial exposure, karstification, and subsurface diagenesis and erosion. Seismic attribute analysis records the variability of diagenesis and shows that diagenetic effects are predominantly concentrated along sequence boundaries, sometimes to significant depths below the sequence boundary.Results to date indicate that application of a velocity model based on this new interpretation will enable improved precision of depth estimates to the top Latrobe Group unconformity to less than five per cent.

scholarly journals How do tectonics influence the initiation and evolution of submarine canyons A case study from the Otway Basin, SE Australia

2021 ◽  
Author(s):  
Nan Wu ◽  
Harya Nugraha ◽  
Michael Steventon ◽  
Fa Zhong
Keyword(s):  
Late Miocene ◽  
Submarine Canyon ◽  
Turbidity Currents ◽  
Submarine Canyons ◽  
Seismic Reflection Data ◽  
Reflection Data ◽  
Depositional Processes ◽  
Seabed Topography ◽  
Gravity Driven ◽  
Unconformity Surface

The architecture of canyon-fills can provide a valuable record of the link between tectonics, sedimentation, and depositional processes in submarine settings. We integrate 3D and 2D seismic reflection data to investigate the dominant tectonics and sedimentary processes involved in the formation of two deeply buried (c. 500 m below seafloor), and large (c. 3-6 km wide, >35 km long) Late Miocene submarine canyons. We found the plate tectonic-scale events (i.e. continental breakup and shortening) have a first-order influence on the submarine canyon initiation and evolution. Initially, the Late Cretaceous (c. 65 Ma) separation of Australia and Antarctica resulted in extensional fault systems, which then formed stair-shaped paleo-seabed. This inherited seabed topography allowed gravity-driven processes (i.e. turbidity currents and mass-transport complexes) to occur. Subsequently, the Late Miocene (c. 5 Ma) collision of Australia and Eurasia, and the resulting uplift and exhumation, have resulted in a prominent unconformity surface that coincides with the base of the canyons. We suggest that the Late Miocene intensive tectonics and associated seismicity have resulted in instability in the upper slope that consequently gave rise to emplacement of MTCs, initiating the canyons formation. Therefore, we indicate that regional tectonics play a key role in the initiation and development of submarine canyons.

scholarly journals Micromorphology of modern tills in southwestern Spitsbergen – insights into depositional and post-depositional processes

2016 ◽  
Vol 37 (4) ◽  
pp. 435-456 ◽  
Author(s):  
Katarzyna Skolasińska ◽  
Grzegorz Rachlewicz ◽  
Witold Szczuciński
Keyword(s):  
Textural Properties ◽  
Coarse Grained ◽  
Glacial Deposits ◽  
Glacier Surface ◽  
Depositional Processes ◽  
Basal Ice ◽  
Mass Flows ◽  
Characteristic Features ◽  
Marginal Zones ◽  
Layer Deformation

AbstractTextural properties and microstructures are commonly used properties in the analysis of Pleistocene and older glacial deposits. However, contemporary glacial deposits are seldom studied, particularly in the context of post-depositional changes. This paper presents the results of a micromorphological study of recently deposited tills in the marginal zones of Hansbreen and Torellbreen, glaciers in southwestern Spitsbergen. The main objectives of this study were to compare modern tills deposited in subglacial and supraglacial conditions, as well as tills that were freshly released from ice with those laid down several decades ago. The investigated tills are primarily composed of large clasts of metamorphic rocks and represent coarse-grained, matrix-supported diamictons. The tills reveal several characteristic features for ductile (e.g.turbate structures) and brittle (e.g.lineations, microshears) deformations, which have been considered to be indicative of subglacial conditions. In supraglacial tills, the same structures are common as in the subglacial deposits, which points to the preservation of the primary features, though the sediment was transferred up to the glacier surface due to basal ice layer deformation and redeposited as slumps, or to formation of similar structures due to short-distance sediment re-deposition by mass flows. This study revealed that it might not be possible to distinguish subglacial and supraglacial tills on the basis of micromorphology if the latter are derived from a subglacial position. The only noted difference was the presence of iron oxide cementation zones and carbonate dissolution features in supraglacial tills. These features were found in tills that were deposited at least a few years ago and are interpreted to be induced by early post-depositional processes involving porewater/sediment interactions.

scholarly journals Hilbert problems for the geosciences in the 21st century

2001 ◽  
Vol 8 (4/5) ◽  
pp. 211-211 ◽  
Author(s):  
M. Ghil
Keyword(s):  
Nonlinear Systems ◽  
Time Scales ◽  
21St Century ◽  
Land Surface ◽  
Thermohaline Circulation ◽  
Low Frequency ◽  
Coarse Grained ◽  
Climate Control ◽  
Unified Framework

Abstract. The scientific problems posed by the Earth's fluid envelope, and its atmosphere, oceans, and the land surface that interacts with them are central to major socio-economic and political concerns as we move into the 21st century. It is natural, therefore, that a certain impatience should prevail in attempting to solve these problems. The point of this review paper is that one should proceed with all diligence, but not excessive haste: "festina lente," as the Romans said two thousand years ago, i.e. "hurry in a measured way." The paper traces the necessary progress through the solutions to the ten problems: 1. What is the coarse-grained structure of low-frequency atmospheric variability, and what is the connection between its episodic and oscillatory description? 2. What can we predict beyond one week, for how long, and by what methods? 3. What are the respective roles of intrinsic ocean variability, coupled ocean-atmosphere modes, and atmospheric forcing in seasonal-to-interannual variability? 4. What are the implications of the answer to the previous problem for climate prediction on this time scale? 5. How does the oceans' thermohaline circulation change on interdecadal and longer time scales, and what is the role of the atmosphere and sea ice in such changes? 6. What is the role of chemical cycles and biological changes in affecting climate on slow time scales, and how are they affected, in turn, by climate variations? 7. Does the answer to the question above give us some trigger points for climate control? 8. What can we learn about these problems from the atmospheres and oceans of other planets and their satellites? 9. Given the answer to the questions so far, what is the role of humans in modifying the climate? 10. Can we achieve enlightened climate control of our planet by the end of the century? A unified framework is proposed to deal with these problems in succession, from the shortest to the longest timescale, i.e. from weeks to centuries and millennia. The framework is that of dynamical systems theory, with an emphasis on successive bifurcations and the ergodic theory of nonlinear systems. The main ideas and methods are outlined and the concept of a modelling hierarchy is introduced. The methodology is applied across the modelling hierarchy to Problem 5, which concerns the thermohaline circulation and its variability. Key words. Climate dynamics, nonlinear systems, numerical bifurcations, mathematical geophysics

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