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1.
Jaume Llopart Roger Urgeles Carl Fredrik Forsberg Angelo Camerlenghi Maarten Vanneste Michele Rebesco Renata Giulia Lucchi Denise Christina Rüther Hendrik Lantzsch 《Basin Research》2019,31(3):487-513
Using a combination of geophysical and geotechnical data from Storfjorden Trough Mouth Fan off southern Svalbard, we investigate the hydrogeology of the continental margin and how this is affected by Quaternary glacial advances and retreats over the continental shelf. The geotechnical results show that plumites, deposited during the deglaciation, have high porosities, permeabilities and compressibilities with respect to glacigenic debris flows and tills. These results together with margin stratigraphic models obtained from seismic reflection data were used as input for numerical finite element models to understand focusing of interstitial fluids on glaciated continental margins. The modelled evolution of the Storfjorden TMF shows that tills formed on the shelf following the onset of glacial sedimentation (ca. 1.5 Ma) acted as aquitards and therefore played a significant role in decreasing the vertical fluid flow towards the sea floor and diverting it towards the slope. The model shows that high overpressure ratios (up to λ ca. 0.6) developed below the shelf edge and on the middle slope. A more detailed model for the last 220 kyrs accounting for ice loading during glacial maxima shows that the formation of these aquitards on the shelf focused fluid flow towards the most permeable plumite sediments on the slope. The less permeable glacigenic debris flows that were deposited during glacial maxima on the slope hinder fluid evacuation from plumites allowing high overpressure ratios (up to λ ca. 0.7) to develop in the shallowest plumite layers. These high overpressures likely persist to the Present and are a critical precondition for submarine slope failure. 相似文献
2.
Ceramicola S. Rebesco M. De Batist M. Khlystov O. 《Marine Geophysical Researches》2001,22(5-6):445-464
High resolution, single-channel seismic sparker profiles across the Akademichesky Ridge, an intra-basin structural high in Lake Baikal (Russia), reveal the presence of small sediment mounds and intervening moats in the upper part of the sedimentary cover. Such features interrupt the generally uniform and even acoustic facies and are not consistent with the hemipelagic sedimentation, which is expected on such an isolated high and which would produce a uniform sediment drape over bottom irregularities. The influence of turbidity currents is excluded since the ridge is an isolated high elevated more than 600-1000 m above adjacent basins. The mounded seismic facies, including migrating sediment waves and non-depositional/erosional incisions, strongly suggest that sediment accumulation was controlled by bottom-current activity. We interpret the mounds as small-scale (< few tens of km2 in area) lacustrine drifts. Four basic types of geometry are identified: 1) slope-plastered patch sheets; 2) patch drifts; 3) confined drifts; 4) fault-controlled drifts. The general asymmetry in the sedimentary cover of the ridge, showing thicker deposits on the NW flank, and the common location of patch drifts on the northeast side of small basement knolls indicate that deposition took preferentially place at the lee sides of obstacles in a current flowing northward or sub-parallel to the main contours. Deep-water circulation in the ridge area is not known in detail, but there are indications that relatively cold saline water masses are presently flowing out of the Central Basin and plunging into the deep parts of the North Basin across the ridge, a process that appears to be driven mainly by small differences in salinity. We infer that the process responsible for the observed bottom-current-controlled sedimentary features has to be sought in these large-scale water-mass movements and their past equivalents. The age of the onset of the bottom-current-controlled sedimentation, based on an average sedimentation rate of 4.0 cm/ky, is roughly estimated to be as least as old as 3.5 Ma, which is generally regarded as the age of the onset of the last major tectonic pulse of rift basin development in the Baikal region. 相似文献
3.
Effects of biogenic silica on sediment compaction and slope stability on the Pacific margin of the Antarctic Peninsula 总被引：2，自引：0，他引：2
Analysis of physical properties measured on cores and on discrete samples collected by the Ocean Drilling Programme (ODP) Leg 178 on the Pacific margin of the Antarctic Peninsula reveals anomalous down‐hole curves of porosity, density, water content, and P‐wave velocity. These indicate an overall trend of increasing porosity with depth and suggest that the drifts are mostly undercompacted. In one of the two boreholes analysed, a sharp decrease in porosity, matching increasing bulk sediment density and increasing compressional velocity occurs towards the base of the hole, which corresponds to a bottom‐simulating reflector in the seismic section. Analysis of seismic reflection, down‐hole logging, geotechnical and mineralogical data from two drilling sites indicates that the observed anomalous consolidation trends are a consequence of the presence of biogenic silica (diatom and radiolarian skeletons) even with a small to moderate amount. Above the bottom‐simulating reflector, intergranular contacts among whole or broken siliceous microfossils prevent normal sediment consolidation. Diagenetic alteration of biogenic opal‐A to opal‐CT causes a dramatic reduction of intra‐ and interskeletal porosity allowing sediments to consolidate at depth. This results in overpressuring and a decrease in the effective stress. Excess fluids are expelled towards the sediment surface through near vertical, small throw normal faults extending from the diagenetic front to the seafloor and affecting the stability of the submarine slope in the form of gravitational creep along a weakened surface. This work shows how physical properties of shallow fine‐grained marine sediments can be analysed as basin‐wide indicators of biogenic silica abundance. The diagenetic alteration of siliceous microfossils is a possible cause of slope instability along world continental margins where bottom‐simulating reflectors related to silica diagenesis are present at a regional scale. 相似文献
4.
The understanding of the evolution of the Antarctic Ice Sheet is crucial for the comprehension of the history of past global
climate. The debate regarding the age of the transition to modern “dry- and cold-based” ice sheet after the Neogene polythermal
conditions has taken place over more than 20 years. An evident change in the geometry of the depositional systems of the Prydz
Bay continental margin demarked the initiation of the Prydz Channel Fan and has been inferred to correspond to this transition.
The improvement in the age placement of this change contributes to unravel the last stages of the Antarctic glacial history.
We predicted the spatial distribution of P-wave velocity data along both dip- and strike-oriented seismic profiles that intersect
3 Ocean Drilling Program (ODP) sites on the Prydz Bay continental shelf. We used this information to assist the correlation
of the existing litho- and bio-stratigraphic information among the drilling sites and to produce an accurate geometric reconstruction
of the Neogene shelf units through depth-migration of the seismic data. The revised stratigraphy that we obtained suggests
an early late to late early Pliocene age for the seismic reflector at the base of the Prydz Channel Fan. This age, younger
than previously proposed, is consistent with the age inferred for similar geometric changes identified in different Antarctic
margins. 相似文献
5.
We have obtained improved images of a debris flow deposit through the reprocessing of multichannel seismic reflection data
between Drifts 6 and 7 of the continental rise of the Pacific margin of the Antarctic Peninsula. The reprocessing, primarily
aimed at the reduction of noise, relative to amplitude preservation, deconvolution, also included accurate velocity analyses.
The deposit is dated as upper Pliocene (nearly 3.0 Ma) via correlation to Sites 1095 and 1096 of the Ocean Drilling Program
(ODP) Leg 178. The estimated volume is about 1800 km3 and the inferred provenance from the continental slope implies a run out distance exceeding 250 km. The dramatic mass-wasting
event that produced this deposit, unique in the sedimentary history of this margin, is related to widespread late Pliocene
margin erosion. This was associated with a catastrophic continental margin collapse, following the Antarctic ice sheet expansion
in response to global cooling. The seismic data analysis also allowed us to identify diffractions and amplitude anomalies
interpreted as expressions of sedimentary mounds at the seafloor overlying narrow high-velocity zones that we interpret as
conduits of fluid expulsion hosting either methane hydrates or authigenic carbonates. Fluid expulsion was triggered by loading
of underlying sediments by the debris flow deposits and may have continued until today by input of fluids from sediment compaction
following the deep diagenesis of biogenic silica. 相似文献
6.
Francisco Javier Hern��ndez-Molina Dorrik A. V. Stow Estefan��a Llave Michele Rebesco Gemma Ercilla David Van Rooij Anxo Mena Juan-Tom��s V��zquez Antje H. L. Voelker 《Geo-Marine Letters》2011,31(5-6):285-300
Deep-water circulation is a critical part of the global conveyor belt that regulates Earth??s climate. The bottom (contour)-current component of this circulation is of key significance in shaping the deep seafloor through erosion, transport, and deposition. As a result, there exists a high variety of large-scale erosional and depositional features (drifts) that together form more complex contourite depositional systems on continental slopes and rises as well as in ocean basins, generated by different water masses flowing at different depths and at different speeds either in the same or in opposite directions. Yet, the nature of these deep-water processes and the deposited contourites is still poorly understood in detail. Their ultimate decoding will undoubtedly yield information of fundamental importance to the earth and ocean sciences. The international congress Deep-water Circulation: Processes & Products was held from 16?C18 June 2010 in Baiona, Spain, hosted by the University of Vigo. Volume 31(5/6) of Geo-Marine Letters is a special double issue containing 17 selected contributions from the congress, guest edited by F.J. Hernández-Molina, D.A.V. Stow, E. Llave, M. Rebesco, G. Ercilla, D. Van Rooij, A. Mena, J.-T. Vázquez and A.H.L. Voelker. The papers and discussions at the congress and the articles in this special issue provide a truly multidisciplinary perspective of interest to both academic and industrial participants, contributing to the advancement of knowledge on deep-water bottom circulation and related processes, as well as contourite sedimentation. The multidisciplinary contributions (including geomorphology, tectonics, stratigraphy, sedimentology, paleoceanography, physical oceanography, and deep-water ecology) have demonstrated that advances in paleoceanographic reconstructions and our understanding of the ocean??s role in the global climate system depend largely on the feedbacks among disciplines. New insights into the link between the biota of deep-water ecosystems and bottom currents confirm the need for this field to be investigated and mapped in detail. Likewise, it is confirmed that deep-water contourites are not only of academic interest but also potential resources of economic value. Cumulatively, both the congress and the present volume serve to demonstrate that the role of bottom currents in shaping the seafloor has to date been generally underestimated, and that our understanding of such systems is still in its infancy. Future research on contourites, using new and more advanced techniques, should focus on a more detailed visualization of water-mass circulation and its variability, in order to decipher the physical processes involved and the associations between drifts and other common bedforms. Moreover, contourite facies models should be better established, including their associations with other deep-water sedimentary environments both in modern and ancient submarine domains. The rapid increase in deep-water exploration and the new deep-water technologies available to the oil industry and academic institutions will undoubtedly lead to spectacular advances in contourite research in terms of processes, morphology, sediment stacking patterns, facies, and their relationships with other deep-marine depositional systems. 相似文献
7.
8.
A new multi‐proxy investigation of Late Quaternary palaeoenvironments along the north‐western Barents Sea (Storfjorden Trough Mouth Fan) 
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Michele Rebesco Robert D. Larter Angelo Camerlenghi Peter F. Barker 《Geo-Marine Letters》1996,16(2):65-75
Multichannel seismic reflection profiles from the continental rise west of the Antarctic Peninsula between 63° and 69°S show the growth of eight very large mound-shaped sedimentary bodies. MCS profiles and long-range side-scan sonar (GLORIA) images show the sea floor between mounds is traversed by channels originating in a dendritic pattern near the base of the continental slope. The mounds are interpreted as sediment drifts, constructed mainly from the fine-grained components of turbidity currents originating on the continental slope, entrained in a nepheloid layer within the ambient southwesterly bottom currents and redeposited downcurrent. 相似文献
10.
R. C. Neagu U. Tinivella V. Volpi M. Rebesco A. Camerlenghi 《International Journal of Earth Sciences》2009,98(4):839-848
Petrophysical properties (wet bulk density, porosity, P-wave velocity) are used to predict biogenic silica contents along
a seismic reflection profile that ties two well sites, 1095 and 1096, drilled by Ocean Drilling Program (ODP) Leg 178 on sediment
drifts on the Pacific continental margin of the Antarctic Peninsula. The biogenic silica contents along the seismic reflection
profile were estimated on the basis of three hypotheses about petrophysical properties distributions in the two boreholes
and statistical relationships between biogenic silica and other petrophysical properties, which were established on various
sediment layers within the boreholes. Our study demonstrates the possibility to reliably predict the distribution of biogenic
silica in the sub-seabed sediments if seismic data processed with amplitude preservation are used and statistical relations
are considered. We conclude that the statistical extrapolation of biogenic silica content along seismic reflection profiles
tied to borehole data is an efficient tool to quantify the amounts of silica undergoing crystalline transformation, which
may have strong implications for submarine slope destabilisation. 相似文献