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A.j. Russell - One of the best experts on this subject based on the ideXlab platform.
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jokulhlaup ice dammed lake outburst flood impact within a valley confined sandur subject to backwater conditions kangerlussuaq west greenland
Sedimentary Geology, 2009Co-Authors: A.j. RussellAbstract:Abstract This paper examines the controls on the morphology and Sedimentology of a valley-confined proglacial outwash plain or ‘sandur’ in West Greenland subject to glacial outburst floods (jokulhlaups). Jokulhlaup flow conditions observed during a recent (1987) flood are linked to sandur Sedimentology and morphological change. Backwater effects over the distal sandur resulted in a reduction of stream power despite increasing discharge. Bar units were typically large. Bar front advance of 60 m during 1987 jokulhlaup occurred prior to waning stage bar dissection by chute channels. Channel change was confined to the distal sandur, due to the greater erodibility of the finer-grained bars. A temporary zone of sediment storage prevailed at the transition between free flowing and ponded flood waters until flood powers increased during waning flood stage as backwater effects were removed. Extension of pre-existing high-relief amplitude bars within the distal sandur records sedimentation related to at least eight jokulhlaups, whilst lower-relief amplitude, proximal sandur sediments provide a composite record of the last high stage jokulhlaup flows. Backwater conditions during jokulhlaups have increased the rapidity of spatial variation of grain sizes and fluvial facies types. Complex, within-event, sediment reworking and routing is generated by the onset and break up of backwater effects. The role of local topography is therefore crucial when interpreting the sedimentary record of former proglacial channels potentially subject to jokulhlaups. This study may prove useful in identifying the presence of flood cycles within palaeo-fluvial systems in both formerly glaciated and non glaciated areas.
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the role of hydrograph shape in controlling glacier outburst flood jokulhlaup sedimentation
IAHS-AISH publication, 2002Co-Authors: Lucy E Rushmer, Oskar Knudsen, A.j. Russell, Fiona S. Tweed, Philip M MarrenAbstract:Glacial outburst floods (jokulhlaups) play an important part in proglacial geomorphology and Sedimentology. Research on the impact of floods has made assumptions by associating jokulhlaup sedimentary successions with distinctive hydrograph shapes and flow rheology. However, jokulhlaup hydrograph shape alone is thought to have a significant impact on proglacial Sedimentology. To date, little information exists concerning the role of hydrograph shape as a control on the sedimentological and geomorpho-ogical impact of jokulhlaups. This paper illustrates how field interpretation of flood deposits can be related to specific hydrograph shapes, and outlines how flume experiments can be used to assess the extent to which hydrograph shape exerts a control on jokulhlaup Sedimentology.
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obstacle marks produced by flow around stranded ice blocks during a glacier outburst flood jokulhlaup in west greenland
Sedimentology, 1993Co-Authors: A.j. RussellAbstract:The effects of glacier ice block grounding on the morphology and Sedimentology of proglacial fluvial outwash were examined during a glacier outburst flood or jokulhlaup, near Sondre Stromfjord, west Greenland. Observations made during and after the 1987 jokulhlaup both on the surface of an ice contact delta and within a confined valley sandur plain provided information about the formation of ice block obstacle marks and the significance of these bedforms for sandur morphology and Sedimentology. Flow directions determined from obstacle mark morphology have been used successfully to chart flow direction changes on the falling limb of the jokulhlaup. Maximum flow depths for scour around stranded ice blocks may be given by 0·5–0·9 times the diameter of the ice block, as estimated from the depth of scour, the height of the obstacle shadow or the extent of ice block meltout sediments. Minimum flow depths can be represented by the height of the obstacle shadow above the mean bed level. The internal composition of the shadow indicates the ability of the flow to transport various sizes of material into the lee of obstacles. Ice block obstacle marks within the distal portion of the sandur initiated waning stage channel change. Proximal and lateral erosion around stranded ice blocks extended downstream from the ice block, forming chute channels which then captured waning stage flows, resulting in significant bar incision with associated deposition of lobate or deltaic deposits. It is suggested that ice block obstacle marks are important in terms of channel morphology, channel morphological change and their usefulness as palaeohydrological indicators.
P F Silva - One of the best experts on this subject based on the ideXlab platform.
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multidisciplinary characterization of quaternary mass movement deposits in the portimao bank gulf of cadiz sw iberia
Marine Geology, 2020Co-Authors: P F Silva, Cristina Roque, Teresa Drago, A Belen, Bernard Henry, E Gemma, A Lopes, Nieves LopezgonzalezAbstract:Abstract We present a multidisciplinary study of the seismic stratigraphy, Sedimentology, geochemistry and magnetism to characterize the Quaternary mass movement deposits (MMD) and the associated deformation in the Portimao Bank (Gulf of Cadiz, offshore SW Iberia). Two scales of approach have been applied. At large-scale (m to km) approach, were recognized and characterized a series of important and subsequent slide scars (tens of meters high) and MMD (the larger one with 10 km length) related to landslides, more prominent at Portimao Bank's southern flank. At small-scale (cm) approach, we point out on a piston core collected within a scar affected by MMD, a replication of the sedimentary column as evidenced by geochronological results and corroborated by Sedimentology, geochemistry and magnetic data. Magnetic fabric data enabled the identification and characterization of the internal structure and deformation of MMD along the sedimentary column. For last, geochronology and the morphology of Portimao seamount are discussed in order to constraint the factors controlling MMD triggering. The multidisciplinary approach is useful in a better characterization of the MMD at different scales and improved the understanding of its dynamics.
Boulvain Frédéric - One of the best experts on this subject based on the ideXlab platform.
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Magnetic Susceptibility Record in Paleozoic Succession (Rhenohercynian Massif, Northern Europe) – Disentangling Sea Level, Local and Diagenetic Impact on the Magnetic Records
'Frontiers Media SA', 2019Co-Authors: Pas Damien, Da Silva Anne-christine, Poulain Geoffrey, Spassov Simo, Boulvain FrédéricAbstract:This study uses an integrated approach, including Sedimentology, geochemistry and hysteresis magnetic measurements on a million year Givetian sequence in the southern margin of the Ardennes carbonate platform (France) to test the reliability of magnetic susceptibility (χ) records as inter-regional correlation tools in remagnetized settings. Furthermore, we aim to better understand the N-S depositional variations and sea-level fluctuations in the Ardennes. Sedimentological analyses revealed a complex platform evolution displaying a variety of shallow- and off-reef paleoenvironmental rocks, which ultimately allowed us to improve the sedimentological model of this area and to constrain the main sea-level fluctuations within the southern margin of the Ardennes platform. Comparison of the χ curve of this succession with previously published time-equivalent records in the western margin of the platform indicates a clear correlation between the two areas, despite the distance between the locales, their different Sedimentology background and the remagnetization affecting the entire region. In contrast, the comparison of these χ profiles from the Ardennes (SW Rhenohercynian Massif, Belgian and France) with coeval data from the Rheinisches Schiefergebirge (NE Rhenohercynian Massif, Germany) do not show obvious correlations. Therefore, it is inferred that syn-sedimentary autogenic processes (e.g., vicinity to landmasses, wave agitation), which operate at small spatial and temporal scales affected the χ signal and could cause the lack of correlation between χ profiles.Peer reviewe
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Magnetic Susceptibility Record in Paleozoic Succession (Rhenohercynian Massif, Northern Europe) – Disentangling Sea Level, Local and Diagenetic Impact on the Magnetic Records
'Frontiers Media SA', 2019Co-Authors: Pas Damien, Da Silva Anne-christine, Poulain Geoffrey, Spassov Simo, Boulvain FrédéricAbstract:peer reviewedThis study uses an integrated approach, including Sedimentology, geochemistry and hysteresis magnetic measurements on a million year Givetian sequence in the southern margin of the Ardennes carbonate platform (France) to test the reliability of magnetic susceptibility (χ) records as inter-regional correlation tools in remagnetized settings. Furthermore, we aim to better understand the N-S depositional variations and sea-level fluctuations in the Ardennes. Sedimentological analyses revealed a complex platform evolution displaying a variety of shallow- and off-reef paleoenvironmental rocks, which ultimately allowed us to improve the sedimentological model of this area and to constrain the main sea-level fluctuations within the southern margin of the Ardennes platform. Comparison of the χ curve of this succession with previously published time-equivalent records in the western margin of the platform indicates a clear correlation between the two areas, despite the distance between the locales, their different Sedimentology background and the remagnetization affecting the entire region. In contrast, the comparison of these χ profiles from the Ardennes (SW Rhenohercynian Massif, Belgian and France) with coeval data from the Rheinisches Schiefergebirge (NE Rhenohercynian Massif, Germany) do not show obvious correlations. Therefore, it is inferred that syn-sedimentary autogenic processes (e.g., vicinity to landmasses, wave agitation), which operate at small spatial and temporal scales affected the χ signal and could cause the lack of correlation between χ profiles.IGCP-652 project “Reading geologic time in Paleozoic sedimentary rocks: the need for an integrated stratigraphy
Nieves Lopezgonzalez - One of the best experts on this subject based on the ideXlab platform.
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multidisciplinary characterization of quaternary mass movement deposits in the portimao bank gulf of cadiz sw iberia
Marine Geology, 2020Co-Authors: P F Silva, Cristina Roque, Teresa Drago, A Belen, Bernard Henry, E Gemma, A Lopes, Nieves LopezgonzalezAbstract:Abstract We present a multidisciplinary study of the seismic stratigraphy, Sedimentology, geochemistry and magnetism to characterize the Quaternary mass movement deposits (MMD) and the associated deformation in the Portimao Bank (Gulf of Cadiz, offshore SW Iberia). Two scales of approach have been applied. At large-scale (m to km) approach, were recognized and characterized a series of important and subsequent slide scars (tens of meters high) and MMD (the larger one with 10 km length) related to landslides, more prominent at Portimao Bank's southern flank. At small-scale (cm) approach, we point out on a piston core collected within a scar affected by MMD, a replication of the sedimentary column as evidenced by geochronological results and corroborated by Sedimentology, geochemistry and magnetic data. Magnetic fabric data enabled the identification and characterization of the internal structure and deformation of MMD along the sedimentary column. For last, geochronology and the morphology of Portimao seamount are discussed in order to constraint the factors controlling MMD triggering. The multidisciplinary approach is useful in a better characterization of the MMD at different scales and improved the understanding of its dynamics.
Teresa Drago - One of the best experts on this subject based on the ideXlab platform.
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multidisciplinary characterization of quaternary mass movement deposits in the portimao bank gulf of cadiz sw iberia
Marine Geology, 2020Co-Authors: P F Silva, Cristina Roque, Teresa Drago, A Belen, Bernard Henry, E Gemma, A Lopes, Nieves LopezgonzalezAbstract:Abstract We present a multidisciplinary study of the seismic stratigraphy, Sedimentology, geochemistry and magnetism to characterize the Quaternary mass movement deposits (MMD) and the associated deformation in the Portimao Bank (Gulf of Cadiz, offshore SW Iberia). Two scales of approach have been applied. At large-scale (m to km) approach, were recognized and characterized a series of important and subsequent slide scars (tens of meters high) and MMD (the larger one with 10 km length) related to landslides, more prominent at Portimao Bank's southern flank. At small-scale (cm) approach, we point out on a piston core collected within a scar affected by MMD, a replication of the sedimentary column as evidenced by geochronological results and corroborated by Sedimentology, geochemistry and magnetic data. Magnetic fabric data enabled the identification and characterization of the internal structure and deformation of MMD along the sedimentary column. For last, geochronology and the morphology of Portimao seamount are discussed in order to constraint the factors controlling MMD triggering. The multidisciplinary approach is useful in a better characterization of the MMD at different scales and improved the understanding of its dynamics.
