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Furu Mienis - One of the best experts on this subject based on the ideXlab platform.
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Carbonate Mound development in contrasting settings on the Irish margin
Deep Sea Research Part II: Topical Studies in Oceanography, 2014Co-Authors: Cees Van Der Land, Furu Mienis, Henk De Haas, John J. G. Reijmer, Dierk Hebbeln, Markus Hermann Eisele, Tjeerd C.e. Van WeeringAbstract:Cold-water coral Carbonate Mounds, formed by framework building cold-water corals, are found in several Mound provinces on the Irish margin. Differences in cold-water coral Mound development rates and sediment composition between Mounds at the southwest Rockall Trough margin and the Galway Mound in the Porcupine Seabight are investigated. Variations in sediment composition in the two Mound provinces are related to the local environmental conditions and sediment sources. Mound accumulation rates are possibly higher at the Galway Mound probably due to a higher influx of hemipelagic fine grained non-Carbonate sediments. In both cold-water coral Mound areas, Mound growth has been continuous for the last ca 11,000 years, before this period several hiatuses and unconformities exist in the Mound record. The most recent unconformity can be correlated across multiple Mounds and Mound provinces at the Irish margin on the basis of apparent age. On the southwest Rockall Trough margin these hiatuses/unconformities are associated with post-depositional aragonite dissolution in, and lithification of, certain intervals, while at Galway Mound no lithification occurs. This study revealed that the influx and types of material transported to cold-water coral Mounds may have a direct impact on the Carbonate Mound accumulation rate and on post-depositional processes. Significantly, the Logachev Mounds on the SW Rockall Trough margin accumulate slower but, because they contain lithified layers, are less susceptible to erosion. This net effect may account for their larger size compared to the Belgica Mounds.
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Paleo-redox fronts and their formation in Carbonate Mound sediments from the Rockall Trough
Marine Geology, 2011Co-Authors: Cees Van Der Land, Furu Mienis, Henk De Haas, John J. G. Reijmer, Rudy Swennen, Henko De Stigter, Tjeerd C.e. Van WeeringAbstract:Abstract Piston cores from the summits of coral topped Carbonate Mounds at the south west Rockall Trough margin reveal that the sediments have undergone significant post-depositional modifications affecting the original geochemical signature and mineralogical composition of the sediments. This diagenetic imprint provides information about the geochemical processes within cold-water coral Mounds. The most prominent result of diagenetic alteration of the primary sediment composition is the absence or poor preservation of aragonitic coral skeletons in certain depth intervals associated with lithification. This study focuses on the enrichment of redox-sensitive elements and the dissolution of primary magnetic ferric iron minerals in the depth interval below lithification levels. By combining the magnetic susceptibility with the XRF signal of Fe and Ti specifically, intervals with susceptibility variations related to the conversion of strongly magnetic into weakly magnetic iron species can be defined. In all three studied cores a succession is recognised with a lithified interval with aragonite dissolution and low-Mg calcite precipitates that is underlain by an interval of magnetite dissolution and of iron and manganese enrichment. For the most recent lithified interval it is demonstrated that initial lithification occurred before an erosional regime was in place, most likely near the end of interglacial or at the start of glacial periods.
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Paleo-redox fronts and their formation in Carbonate Mound sediments from the Rockall Trough
Marine Geology, 2011Co-Authors: Cees Van Der Land, Furu Mienis, Henk De Haas, John J. G. Reijmer, Rudy Swennen, Henko De Stigter, Tjeerd C.e. Van WeeringAbstract:Piston cores from the summits of coral topped Carbonate Mounds at the south west Rockall Trough margin reveal that the sediments have undergone significant post-depositional modifications affecting the original geochemical signature and mineralogical composition of the sediments. This diagenetic imprint provides information about the geochemical processes within cold-water coral Mounds. The most prominent result of diagenetic alteration of the primary sediment composition is the absence or poor preservation of aragonitic coral skeletons in certain depth intervals associated with lithification.This study focuses on the enrichment of redox-sensitive elements and the dissolution of primary magnetic ferric iron minerals in the depth interval below lithification levels. By combining the magnetic susceptibility with the XRF signal of Fe and Ti specifically, intervals with susceptibility variations related to the conversion of strongly magnetic into weakly magnetic iron species can be defined.In all three studied cores a succession is recognised with a lithified interval with aragonite dissolution and low-Mg calcite precipitates that is underlain by an interval of magnetite dissolution and of iron and manganese enrichment. For the most recent lithified interval it is demonstrated that initial lithification occurred before an erosional regime was in place, most likely near the end of interglacial or at the start of glacial periods. © 2011 Elsevier B.V
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diagenetic processes in Carbonate Mound sediments at the south west rockall trough margin
Sedimentology, 2010Co-Authors: Cees Van Der Land, Furu Mienis, Henk De Haas, Rudy Swennen, Norbert Frank, Tjeerd C.e. Van WeeringAbstract:Cold water coral covered Carbonate Mounds at the south-west margin of the Rockall Trough form ridges several kilometres long and up to 380 m high. Piston cores obtained at three Mound crests reveal the complex internal structure of the Mound build up, with alternating unlithified coral-dominated intervals and lithified intervals. The most recent lithified interval is covered by corals embedded in a fine-grained matrix, comprising ca 11 000 years of continuous Mound evolution. Before this time 230Th/U dating shows the presence of several hiatuses in Mound build-up. Aragonitic coral material is absent or only present as mouldic porosity in the lithified intervals and coccoliths display widespread overgrowth. Downcore X-ray fluorescence scanning, computer tomography scan images and petrographic observations indicate different degrees of diagenetic alteration. The upper boundary of the most recent lithified interval shows some erosional features, but petrographic observations indicate that initial lithification of the sediments is not related to this erosive event or to long-term non-sedimentation, but to earlier sub-surface diagenesis. Organic matter oxidation and the subsequent lowering of the saturation state of the Carbonate system drives dissolution of the unstable aragonitic coral skeletons. Depending on the openness of the system, this can lead to precipitation of a more stable low-magnesium Carbonate. A model is presented describing the sedimentary and diagenetic processes leading to the formation of lithified intervals.
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Diagenetic processes in Carbonate Mound sediments at the south‐west Rockall Trough margin
Sedimentology, 2010Co-Authors: Cees Van Der Land, Furu Mienis, Henk De Haas, Rudy Swennen, Norbert Frank, Tjeerd C.e. Van WeeringAbstract:Cold water coral covered Carbonate Mounds at the south-west margin of the Rockall Trough form ridges several kilometres long and up to 380 m high. Piston cores obtained at three Mound crests reveal the complex internal structure of the Mound build up, with alternating unlithified coral-dominated intervals and lithified intervals. The most recent lithified interval is covered by corals embedded in a fine-grained matrix, comprising ca 11 000 years of continuous Mound evolution. Before this time 230Th/U dating shows the presence of several hiatuses in Mound build-up. Aragonitic coral material is absent or only present as mouldic porosity in the lithified intervals and coccoliths display widespread overgrowth. Downcore X-ray fluorescence scanning, computer tomography scan images and petrographic observations indicate different degrees of diagenetic alteration. The upper boundary of the most recent lithified interval shows some erosional features, but petrographic observations indicate that initial lithification of the sediments is not related to this erosive event or to long-term non-sedimentation, but to earlier sub-surface diagenesis. Organic matter oxidation and the subsequent lowering of the saturation state of the Carbonate system drives dissolution of the unstable aragonitic coral skeletons. Depending on the openness of the system, this can lead to precipitation of a more stable low-magnesium Carbonate. A model is presented describing the sedimentary and diagenetic processes leading to the formation of lithified intervals.
Henko De Stigter - One of the best experts on this subject based on the ideXlab platform.
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Paleo-redox fronts and their formation in Carbonate Mound sediments from the Rockall Trough
Marine Geology, 2011Co-Authors: Cees Van Der Land, Furu Mienis, Henk De Haas, John J. G. Reijmer, Rudy Swennen, Henko De Stigter, Tjeerd C.e. Van WeeringAbstract:Abstract Piston cores from the summits of coral topped Carbonate Mounds at the south west Rockall Trough margin reveal that the sediments have undergone significant post-depositional modifications affecting the original geochemical signature and mineralogical composition of the sediments. This diagenetic imprint provides information about the geochemical processes within cold-water coral Mounds. The most prominent result of diagenetic alteration of the primary sediment composition is the absence or poor preservation of aragonitic coral skeletons in certain depth intervals associated with lithification. This study focuses on the enrichment of redox-sensitive elements and the dissolution of primary magnetic ferric iron minerals in the depth interval below lithification levels. By combining the magnetic susceptibility with the XRF signal of Fe and Ti specifically, intervals with susceptibility variations related to the conversion of strongly magnetic into weakly magnetic iron species can be defined. In all three studied cores a succession is recognised with a lithified interval with aragonite dissolution and low-Mg calcite precipitates that is underlain by an interval of magnetite dissolution and of iron and manganese enrichment. For the most recent lithified interval it is demonstrated that initial lithification occurred before an erosional regime was in place, most likely near the end of interglacial or at the start of glacial periods.
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Paleo-redox fronts and their formation in Carbonate Mound sediments from the Rockall Trough
Marine Geology, 2011Co-Authors: Cees Van Der Land, Furu Mienis, Henk De Haas, John J. G. Reijmer, Rudy Swennen, Henko De Stigter, Tjeerd C.e. Van WeeringAbstract:Piston cores from the summits of coral topped Carbonate Mounds at the south west Rockall Trough margin reveal that the sediments have undergone significant post-depositional modifications affecting the original geochemical signature and mineralogical composition of the sediments. This diagenetic imprint provides information about the geochemical processes within cold-water coral Mounds. The most prominent result of diagenetic alteration of the primary sediment composition is the absence or poor preservation of aragonitic coral skeletons in certain depth intervals associated with lithification.This study focuses on the enrichment of redox-sensitive elements and the dissolution of primary magnetic ferric iron minerals in the depth interval below lithification levels. By combining the magnetic susceptibility with the XRF signal of Fe and Ti specifically, intervals with susceptibility variations related to the conversion of strongly magnetic into weakly magnetic iron species can be defined.In all three studied cores a succession is recognised with a lithified interval with aragonite dissolution and low-Mg calcite precipitates that is underlain by an interval of magnetite dissolution and of iron and manganese enrichment. For the most recent lithified interval it is demonstrated that initial lithification occurred before an erosional regime was in place, most likely near the end of interglacial or at the start of glacial periods. © 2011 Elsevier B.V
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sediment accumulation on a cold water Carbonate Mound at the southwest rockall trough margin
Marine Geology, 2009Co-Authors: Furu Mienis, Henko De Stigter, C Van Der Land, M Van De Vorstenbosch, H De Haas, T O Richter, Tjeerd C.e. Van WeeringAbstract:Abstract Cold-water corals build isolated and clustered Carbonate Mound ridges, several kilometres long and wide and up to 380 m high at the Southwest Rockall Trough margin. Photo and video observations as well as coring have shown that mainly the upper Mound flanks and summits are covered with a thriving living coral cover and associated fauna. Box cores prove the presence of living coral colonies on top of a thick layer of coral debris, which is to a large extent abraded and bio-eroded, before being buried. The coral framework is filled with sediment from settling pelagic material and parts of the fauna living at the Mounds, resulting in a 120 cm thick layer of sediments since 10,800 yr. Component analysis of a piston core from the top of a Carbonate Mound shows a complete record of cold-water coral Mound facies, comprising many different species living at the Mounds. An alternation of skeletal and cement dominated intervals was distinguished in the piston core. Stable isotope analysis of planktonic and benthic foraminifera indicates a continuous sedimentation pattern since the Younger Dryas. The deeper and older part of the core, showing mainly intermediate isotope values, is dominated by the presence of large hiatuses, spanning a total of up to 200,000 yr. Hiatuses in the core may reflect periods of non-deposition or erosion, which may be linked to glacial–interglacial variability. Environmental conditions probably change at glacial–interglacial timescales, influencing the local hydrodynamic regime, food supply and sedimentation rate around the Carbonate Mounds affecting coral growth and therefore Carbonate Mound development.
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Sediment accumulation on a cold-water Carbonate Mound at the Southwest Rockall Trough margin
Marine Geology, 2009Co-Authors: F. Mienis, Henko De Stigter, C. Van Der Land, H De Haas, M. Van De Vorstenbosch, T. Richter, T.c.e. Van WeeringAbstract:Cold-water corals build isolated and clustered Carbonate Mound ridges, several kilometres long and wide and up to 380 m high at the Southwest Rockall Trough margin. Photo and video observations as well as coring have shown that mainly the upper Mound flanks and summits are covered with a thriving living coral cover and associated fauna. Box cores prove the presence of living coral colonies on top of a thick layer of coral debris, which is to a large extent abraded and bio-eroded, before being buried. The coral framework is filled with sediment from settling pelagic material and parts of the fauna living at the Mounds, resulting in a 120 cm thick layer of sediments since 10,800 yr. Component analysis of a piston core from the top of a Carbonate Mound shows a complete record of cold-water coral Mound facies, comprising many different species living at the Mounds. An alternation of skeletal and cement dominated intervals was distinguished in the piston core. Stable isotope analysis of planktonic and benthic foraminifera indicates a continuous sedimentation pattern since the Younger Dryas. The deeper and older part of the core, showing mainly intermediate isotope values, is dominated by the presence of large hiatuses, spanning a total of up to 200,000 yr. Hiatuses in the core may reflect periods of non-deposition or erosion, which may be linked to glacial-interglacial variability. Environmental conditions probably change at glacial-interglacial timescales, influencing the local hydrodynamic regime, food supply and sedimentation rate around the Carbonate Mounds affecting coral growth and therefore Carbonate Mound development. © 2009 Elsevier B.V. All rights reserved
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Hydrodynamic controls on cold-water coral growth and Carbonate-Mound development at the SW and SE Rockall Trough Margin, NE Atlantic Ocean
Deep Sea Research Part I: Oceanographic Research Papers, 2007Co-Authors: Furu Mienis, Henko De Stigter, H De Haas, Martin White, Gerard C.a. Duineveld, T.c.e. Van WeeringAbstract:Long-term (p1-year) records obtained by seabed observatories (BOBO) and repeated (24-h) CTD casts show the presence of a highly energetic environment in and around two cold-water Carbonate-Mound provinces, on the Southwest and Southeast Rockall Trough (SW and SE RT) margin. Carbonate Mounds, covered with a thriving coral cover, are embedded mainly in the Eastern North Atlantic Water (ENAW) and are observed in a confined bathymetric zone between 600 and 1000 m water depth. Cold-water corals seem to be restricted in their growth by temperature and food availability. The presence of living corals on top of the Carbonate Mounds appears linked to the presence of internal waves and tidal currents in the water column, and consequently Carbonate Mound structures are shaped by the local hydrodynamic regime. Mound clusters have an elongated shape perpendicular to the regional contours and corresponding to the direction of the highest current speeds. On the SW RT margin temperature, salinity and current speed reflect a diurnal tidal pattern, causing maximum temperature variations at 900 m depth of more than 31C. Current speeds up to 45 cm s � 1 occur, and a residual current of 10 cm s � 1 is directed along the slope to the southwest. At the SE RT margin the temperature of the bottom water fluctuates more than 11C with a semi-diurnal tidal cyclicity. Amplitudes of average and peak current speeds here are comparable with those measured on the southwest margin, but the residual current in this area is directed to the northeast. Tidal currents and internal waves at both margins force the formation of intermediate and bottom nepheloid layers and bring fresh food particles with increased velocity to the Mounds. The distribution of corals in both Mound areas is considered directly related to the presence of enhanced turbidity. An increase in temperature can be directly related to an increase in the amount of particles in the water column. Current velocity increases when a transition occurs from cold to
T.c.e. Van Weering - One of the best experts on this subject based on the ideXlab platform.
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Sediment accumulation on a cold-water Carbonate Mound at the Southwest Rockall Trough margin
Marine Geology, 2009Co-Authors: F. Mienis, Henko De Stigter, C. Van Der Land, H De Haas, M. Van De Vorstenbosch, T. Richter, T.c.e. Van WeeringAbstract:Cold-water corals build isolated and clustered Carbonate Mound ridges, several kilometres long and wide and up to 380 m high at the Southwest Rockall Trough margin. Photo and video observations as well as coring have shown that mainly the upper Mound flanks and summits are covered with a thriving living coral cover and associated fauna. Box cores prove the presence of living coral colonies on top of a thick layer of coral debris, which is to a large extent abraded and bio-eroded, before being buried. The coral framework is filled with sediment from settling pelagic material and parts of the fauna living at the Mounds, resulting in a 120 cm thick layer of sediments since 10,800 yr. Component analysis of a piston core from the top of a Carbonate Mound shows a complete record of cold-water coral Mound facies, comprising many different species living at the Mounds. An alternation of skeletal and cement dominated intervals was distinguished in the piston core. Stable isotope analysis of planktonic and benthic foraminifera indicates a continuous sedimentation pattern since the Younger Dryas. The deeper and older part of the core, showing mainly intermediate isotope values, is dominated by the presence of large hiatuses, spanning a total of up to 200,000 yr. Hiatuses in the core may reflect periods of non-deposition or erosion, which may be linked to glacial-interglacial variability. Environmental conditions probably change at glacial-interglacial timescales, influencing the local hydrodynamic regime, food supply and sedimentation rate around the Carbonate Mounds affecting coral growth and therefore Carbonate Mound development. © 2009 Elsevier B.V. All rights reserved
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Hydrodynamic controls on cold-water coral growth and Carbonate-Mound development at the SW and SE Rockall Trough Margin, NE Atlantic Ocean
Deep Sea Research Part I: Oceanographic Research Papers, 2007Co-Authors: Furu Mienis, Henko De Stigter, H De Haas, Martin White, Gerard C.a. Duineveld, T.c.e. Van WeeringAbstract:Long-term (p1-year) records obtained by seabed observatories (BOBO) and repeated (24-h) CTD casts show the presence of a highly energetic environment in and around two cold-water Carbonate-Mound provinces, on the Southwest and Southeast Rockall Trough (SW and SE RT) margin. Carbonate Mounds, covered with a thriving coral cover, are embedded mainly in the Eastern North Atlantic Water (ENAW) and are observed in a confined bathymetric zone between 600 and 1000 m water depth. Cold-water corals seem to be restricted in their growth by temperature and food availability. The presence of living corals on top of the Carbonate Mounds appears linked to the presence of internal waves and tidal currents in the water column, and consequently Carbonate Mound structures are shaped by the local hydrodynamic regime. Mound clusters have an elongated shape perpendicular to the regional contours and corresponding to the direction of the highest current speeds. On the SW RT margin temperature, salinity and current speed reflect a diurnal tidal pattern, causing maximum temperature variations at 900 m depth of more than 31C. Current speeds up to 45 cm s � 1 occur, and a residual current of 10 cm s � 1 is directed along the slope to the southwest. At the SE RT margin the temperature of the bottom water fluctuates more than 11C with a semi-diurnal tidal cyclicity. Amplitudes of average and peak current speeds here are comparable with those measured on the southwest margin, but the residual current in this area is directed to the northeast. Tidal currents and internal waves at both margins force the formation of intermediate and bottom nepheloid layers and bring fresh food particles with increased velocity to the Mounds. The distribution of corals in both Mound areas is considered directly related to the presence of enhanced turbidity. An increase in temperature can be directly related to an increase in the amount of particles in the water column. Current velocity increases when a transition occurs from cold to
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Carbonate Mound evolution and coral diagenesis viewed by U-series dating of deep water corals
Eos Transactions American Geophysical Union, 2007Co-Authors: Norbert Frank, C. Van Der Land, Anneleen Foubert, D. Blamart, Estelle Ricard, Christophe Colin, David Van Rooij, T.c.e. Van WeeringAbstract:U-series dating of constructional deep sea corals is a powerful tool to reconstruct the evolution of Carbonate Mound sediments driven by coral growth, sediment trapping and diagenesis. Here we have investigated in great detail the time framework of constructional corals such as L. pertusa and M. oculata on 5 different Mounds of the eastern North Atlantic (on Rockall Bank and in Porcupine Seabight) taken at variable depth and location (610 to 880m water depth). Periods favorable for coral growth are the Holocene and prior interglacials such as marine isotope stage 5 and 7, while glacial coral growth seems inhibited or extremely reduced. Coral development is almost continuous throughout the Holocene since Mound re-colonization about 10,500 years ago. Mound accumulation rates vary between 20 and 220 cm/kyr determined from the coral age - depth relationship in each core. Those changes are most likely driven by changes between horizontal and vertical Mound accumulation, food supply and ocean circulation. In addition, coral dating allowed to identify an important erosional event recorded in core MD01-2455G from Rockall Bank. Here a 1m thick sediment layer containing ancient corals likely from the start of Holocene re-colonization was displaced (collapsed) from further upslope on top of younger corals of ~2500 to 3000 years age. Prior to the initiation of coral growth diagenesis occurred frequently resulting in (1) the construction of so called Carbonate hardgrounds and/or (2) the dissolution of the pre-Holocene coral framework. Solely, the deepest selected core in Porcupine Seabight (MD01-2463G at 880m depth) reveals coral re-colonization on an undisturbed ancient reef structure that dates back to 250,000 years. Diagenesis of earlier coral reef generations leading to coral dissolution leads to a loss of magnetic susceptibility and open system behavior of the coral skeletons with respect to U-series dating. While the processes causing such diagenetic layers are barely understood the disappearance of the magnetic susceptibility can be used to trace such phenomena and a conserved magnetic susceptibility allows sampling of well preserved corals.
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Hydrodynamic controls on Carbonate Mound development: long term in situ seabed BOBO-lander observations and CTD-casts at the SW Rockall Trough Margin and in the Gulf of Cadiz
OCEANS 2007 - Europe, 2007Co-Authors: Furu Mienis, Henko De Stigter, H De Haas, Gerard C.a. Duineveld, T.c.e. Van WeeringAbstract:Long term records obtained by in situ seabed observatories and repeated CTD casts show the presence of a high energetic environment in and around two cold water coral Mound provinces at the SW RT margin and in the Gulf of Cadiz. In both areas cold water corals are present on the Mounds, but the areas differ strongly in geological setting, as well as in sedimentology and hydrography. Measurements of near bed hydrodynamics as recorded with freefalling seabed observatories and water column observations show that currents in Mound areas have a major influence on the presence of living cold water corals and on the shape of Carbonate Mounds. While at the Southwest Rockall Trough margin a dense cover of live corals has been demonstrated, only isolated living colonies and coral debris covered with mud occur on the Mounds in the Gulf of Cadiz, indicating that watermass properties and dynamics on the Southwest Rockall Trough are at the moment most favourable for coral growth.
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Carbonate Mound development at the SW Rockall Trough margin based on high resolution TOBI and seismic recording
Marine Geology, 2006Co-Authors: Furu Mienis, Henko De Stigter, H De Haas, T.c.e. Van Weering, V.a.i. Huvenne, Andrew J. WheelerAbstract:Abstract In 2002, high-resolution sidescan sonar images of a Mound area at the SW Rockall Trough margin were recorded with the TOBI deep towed sidescan sonar. Processed TOBI images with a pixel resolution of 6 m provide a unique overview of the Carbonate Mound distribution and related sedimentary features around the Mounds. Three morphologically distinct areas can be recognised on the TOBI mosaic. In area I (between 500 and 600 m water depth), upslope of the Mounds, giant sediment waves are found with wavelengths up to 500 m, with wave crests of more than 10 km long and with an amplitude of up to 30 m, reflected with a high backscatter on the TOBI image. Area II (between 600 and 1000 m water depth), along the upper margin flank, is characterised by clustered and isolated Carbonate Mounds, forming elongated ridges with an orientation perpendicular to the slope. Sedimentary structures such as flow ridges, sediment waves, local scouring at the foot of some Mounds and draping of sediment around Mounds indicate the influence of strong near-bed currents, oriented in two main current directions parallel to the margin, as well as in a similar direction as the Mound clusters. The Mound clusters are several kilometres long, can be over 380 m high and are dissected by downslope directed channels. On the TOBI image, the Mounds appear as regions of high backscatter caused by the presence of cold water coral colonies on the sediment and by distinct shadows. All Mounds have their tops at a specific depth level (500–600 m water depth). Area III (between 900 and 1200 m water depth) below the Mounds is characterised by disturbed sediments with distinct slump scars and flow ridges. 2D high resolution seismic profiling perpendicular and parallel to the slope across the Mounds does in general not reveal strong internal reflectors within the Mounds. In contrast, three strong reflectors can be observed in the sedimentary sequence underneath the Mounds. The upper reflector C10 (of early Pliocene age) is an erosional unconformity, above which most of the Mounds and sediment waves seem to have developed. The second erosional unconformity C20 (of middle Miocene age) is formed by an apparent irregular surface that locally is dissected by some small faults. Reflectors C10 and C20 have been found in two different Mound clusters in the Mound area, indicating that Mound development possibly started after formation of reflector C20. The third reflector forms the acoustic basement, which is locally dissected by some small faults that are located below the Mounds. At least two stages of Mound formation are recognised on the seismic profiles.
Tjeerd C.e. Van Weering - One of the best experts on this subject based on the ideXlab platform.
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Carbonate Mound development in contrasting settings on the Irish margin
Deep Sea Research Part II: Topical Studies in Oceanography, 2014Co-Authors: Cees Van Der Land, Furu Mienis, Henk De Haas, John J. G. Reijmer, Dierk Hebbeln, Markus Hermann Eisele, Tjeerd C.e. Van WeeringAbstract:Cold-water coral Carbonate Mounds, formed by framework building cold-water corals, are found in several Mound provinces on the Irish margin. Differences in cold-water coral Mound development rates and sediment composition between Mounds at the southwest Rockall Trough margin and the Galway Mound in the Porcupine Seabight are investigated. Variations in sediment composition in the two Mound provinces are related to the local environmental conditions and sediment sources. Mound accumulation rates are possibly higher at the Galway Mound probably due to a higher influx of hemipelagic fine grained non-Carbonate sediments. In both cold-water coral Mound areas, Mound growth has been continuous for the last ca 11,000 years, before this period several hiatuses and unconformities exist in the Mound record. The most recent unconformity can be correlated across multiple Mounds and Mound provinces at the Irish margin on the basis of apparent age. On the southwest Rockall Trough margin these hiatuses/unconformities are associated with post-depositional aragonite dissolution in, and lithification of, certain intervals, while at Galway Mound no lithification occurs. This study revealed that the influx and types of material transported to cold-water coral Mounds may have a direct impact on the Carbonate Mound accumulation rate and on post-depositional processes. Significantly, the Logachev Mounds on the SW Rockall Trough margin accumulate slower but, because they contain lithified layers, are less susceptible to erosion. This net effect may account for their larger size compared to the Belgica Mounds.
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Carbonate Mounds from the Gulf of Cadiz in relation to methane seepage: unrelated phenomena or coupling?
2010Co-Authors: Alina Stadnitskaia, Henk De Haas, Tjeerd C.e. Van Weering, Marianne Baas, R. Kreulen, Jaap S. Sinninghe DamstéAbstract:For more than decade, the formation of Carbonate Mounds, related ecosystem development and organization/functioning of the entire Mound habitats are subjects for a growing amount of studies and discussions. Carbonate Mounds from the Gulf of Cadiz are of special interest due to their association with active mud volcanoes within the El Arraiche mud volcano field. Such co-occurrence of ecologically contrasting phenomena anticipates complex biogeochemical interactions between a Carbonate Mound interior and seeping through hydrocarbon-rich fluids. To get closer in understanding of how methane affects a Carbonate Mound development in the gulf, a combination of inorganic and organic geochemical techniques was applied to two sedimentary cores collected from summits of Alfa and Beta Mounds. These Mounds were found at the NW slope of the Gimini MV at the Pen Duick Mound Province. We analyzed vertical distribution profiles of sulfate, sulfide, chlorinity, DIC in combination with hydrocarbon gas measurements and lipid biomarker study. To have estimates of Sea Surface Temperature (SST) during the Carbonate Mound formation, we applied the TEX86 (TetraEther indeX of tetraethers with 86 carbon atoms; Schouten et al., 2002) and the alkenone-based UK37 index (Muller et al., 1998). The pore-water data revealed the presence of brine inflow, which is consistent with the data of Hensen et al., (2007). The behavior of sulfide distribution profiles and 13C values from dissolved inorganic carbon (DIC) indicated that most of the sulfide and DIC are resulted from the microbial anaerobic oxidation of methane (AOM) processes. In contrast, the analysis of archaeal membrane lipids from distinct clades of AOM-mediating anaerobic methanotrophs showed exceedingly low concentrations of specific biomarkers, which is in contradiction with pore-water and gas chemistry data. Besides, AOM is the main cause for the increase of sedimentary alkalinity that leads to Carbonate precipitation. Instead, some sedimentary intervals associated with pore-water-detected AOM zone showed the presence of semi-dissolved coral branches, indicating thus rather acidic intra-environments. In this paper we discuss a potential “consecutive order” of biogeochemical processes in the close subsurface of Alfa and Beta Carbonate Mounds and outline the importance of careful interpretation of biogeochemical signatures related to past, modern and post seepage episodes.
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diagenetic processes in Carbonate Mound sediments at the south west rockall trough margin
Sedimentology, 2010Co-Authors: Cees Van Der Land, Furu Mienis, Henk De Haas, Rudy Swennen, Norbert Frank, Tjeerd C.e. Van WeeringAbstract:Cold water coral covered Carbonate Mounds at the south-west margin of the Rockall Trough form ridges several kilometres long and up to 380 m high. Piston cores obtained at three Mound crests reveal the complex internal structure of the Mound build up, with alternating unlithified coral-dominated intervals and lithified intervals. The most recent lithified interval is covered by corals embedded in a fine-grained matrix, comprising ca 11 000 years of continuous Mound evolution. Before this time 230Th/U dating shows the presence of several hiatuses in Mound build-up. Aragonitic coral material is absent or only present as mouldic porosity in the lithified intervals and coccoliths display widespread overgrowth. Downcore X-ray fluorescence scanning, computer tomography scan images and petrographic observations indicate different degrees of diagenetic alteration. The upper boundary of the most recent lithified interval shows some erosional features, but petrographic observations indicate that initial lithification of the sediments is not related to this erosive event or to long-term non-sedimentation, but to earlier sub-surface diagenesis. Organic matter oxidation and the subsequent lowering of the saturation state of the Carbonate system drives dissolution of the unstable aragonitic coral skeletons. Depending on the openness of the system, this can lead to precipitation of a more stable low-magnesium Carbonate. A model is presented describing the sedimentary and diagenetic processes leading to the formation of lithified intervals.
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Diagenetic processes in Carbonate Mound sediments at the south‐west Rockall Trough margin
Sedimentology, 2010Co-Authors: Cees Van Der Land, Furu Mienis, Henk De Haas, Rudy Swennen, Norbert Frank, Tjeerd C.e. Van WeeringAbstract:Cold water coral covered Carbonate Mounds at the south-west margin of the Rockall Trough form ridges several kilometres long and up to 380 m high. Piston cores obtained at three Mound crests reveal the complex internal structure of the Mound build up, with alternating unlithified coral-dominated intervals and lithified intervals. The most recent lithified interval is covered by corals embedded in a fine-grained matrix, comprising ca 11 000 years of continuous Mound evolution. Before this time 230Th/U dating shows the presence of several hiatuses in Mound build-up. Aragonitic coral material is absent or only present as mouldic porosity in the lithified intervals and coccoliths display widespread overgrowth. Downcore X-ray fluorescence scanning, computer tomography scan images and petrographic observations indicate different degrees of diagenetic alteration. The upper boundary of the most recent lithified interval shows some erosional features, but petrographic observations indicate that initial lithification of the sediments is not related to this erosive event or to long-term non-sedimentation, but to earlier sub-surface diagenesis. Organic matter oxidation and the subsequent lowering of the saturation state of the Carbonate system drives dissolution of the unstable aragonitic coral skeletons. Depending on the openness of the system, this can lead to precipitation of a more stable low-magnesium Carbonate. A model is presented describing the sedimentary and diagenetic processes leading to the formation of lithified intervals.
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Deep-water corals of the northeastern Atlantic margin: Carbonate Mound evolution and upper intermediate water ventilation during the Holocene
Cold-Water Corals and Ecosystems, 2005Co-Authors: Norbert Frank, Jean-pierre Henriet, D. Blamart, David Van Rooij, Audrey Lutringer, Martine Paterne, Tjeerd C.e. Van WeeringAbstract:We present combined 230Th/U and 14C dating on deep-water corals from the northeastern North Atlantic in order to investigate coral growth and sedimentation on Carbonate Mounds, as well as past changes of intermediate water ventilation. Within European projects GEOMound and ECOMound reef forming Lophelia pertusa deep-water corals were raised from intermediate depth (∼610 to 888 m bsl) from top of Carbonate Mounds at southeast Rockall Bank and at Porcupine Seabight. XRD analyses, δ234U, and 230Th/232Th indicate negligible alteration of the investigated corals, i.e. open system U-series behavior. 230Th/U ages from coral specimens of the uppermost coral sequence of the investigated Mounds range from today to 10,950 CAL yr BP, i.e. coral growth during the Holocene. A modern Lophelia gave a 230Th/U age of 1983±6 AD, close to the date of collection in 2001 AD. Deep-water coral growth is the driving process of sediment accumulation on the summit of Carbonate Mounds, with sediment accumulation rates in the order of ∼0.3 mm yr−1. However, coral growth is discontinuous and irregular, and complete coral sequences are frequently altered (dissolved) likely due to organic matter consumption by oxidizing pore fluids. Mound top sediments indicate the presence of corals over several glacial/interglacial cycles, but corals of glacial origin could not be identified on the investigated Mounds.
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Carbonate Mound development in contrasting settings on the Irish margin
Deep Sea Research Part II: Topical Studies in Oceanography, 2014Co-Authors: Cees Van Der Land, Furu Mienis, Henk De Haas, John J. G. Reijmer, Dierk Hebbeln, Markus Hermann Eisele, Tjeerd C.e. Van WeeringAbstract:Cold-water coral Carbonate Mounds, formed by framework building cold-water corals, are found in several Mound provinces on the Irish margin. Differences in cold-water coral Mound development rates and sediment composition between Mounds at the southwest Rockall Trough margin and the Galway Mound in the Porcupine Seabight are investigated. Variations in sediment composition in the two Mound provinces are related to the local environmental conditions and sediment sources. Mound accumulation rates are possibly higher at the Galway Mound probably due to a higher influx of hemipelagic fine grained non-Carbonate sediments. In both cold-water coral Mound areas, Mound growth has been continuous for the last ca 11,000 years, before this period several hiatuses and unconformities exist in the Mound record. The most recent unconformity can be correlated across multiple Mounds and Mound provinces at the Irish margin on the basis of apparent age. On the southwest Rockall Trough margin these hiatuses/unconformities are associated with post-depositional aragonite dissolution in, and lithification of, certain intervals, while at Galway Mound no lithification occurs. This study revealed that the influx and types of material transported to cold-water coral Mounds may have a direct impact on the Carbonate Mound accumulation rate and on post-depositional processes. Significantly, the Logachev Mounds on the SW Rockall Trough margin accumulate slower but, because they contain lithified layers, are less susceptible to erosion. This net effect may account for their larger size compared to the Belgica Mounds.
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Paleo-redox fronts and their formation in Carbonate Mound sediments from the Rockall Trough
Marine Geology, 2011Co-Authors: Cees Van Der Land, Furu Mienis, Henk De Haas, John J. G. Reijmer, Rudy Swennen, Henko De Stigter, Tjeerd C.e. Van WeeringAbstract:Abstract Piston cores from the summits of coral topped Carbonate Mounds at the south west Rockall Trough margin reveal that the sediments have undergone significant post-depositional modifications affecting the original geochemical signature and mineralogical composition of the sediments. This diagenetic imprint provides information about the geochemical processes within cold-water coral Mounds. The most prominent result of diagenetic alteration of the primary sediment composition is the absence or poor preservation of aragonitic coral skeletons in certain depth intervals associated with lithification. This study focuses on the enrichment of redox-sensitive elements and the dissolution of primary magnetic ferric iron minerals in the depth interval below lithification levels. By combining the magnetic susceptibility with the XRF signal of Fe and Ti specifically, intervals with susceptibility variations related to the conversion of strongly magnetic into weakly magnetic iron species can be defined. In all three studied cores a succession is recognised with a lithified interval with aragonite dissolution and low-Mg calcite precipitates that is underlain by an interval of magnetite dissolution and of iron and manganese enrichment. For the most recent lithified interval it is demonstrated that initial lithification occurred before an erosional regime was in place, most likely near the end of interglacial or at the start of glacial periods.
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Paleo-redox fronts and their formation in Carbonate Mound sediments from the Rockall Trough
Marine Geology, 2011Co-Authors: Cees Van Der Land, Furu Mienis, Henk De Haas, John J. G. Reijmer, Rudy Swennen, Henko De Stigter, Tjeerd C.e. Van WeeringAbstract:Piston cores from the summits of coral topped Carbonate Mounds at the south west Rockall Trough margin reveal that the sediments have undergone significant post-depositional modifications affecting the original geochemical signature and mineralogical composition of the sediments. This diagenetic imprint provides information about the geochemical processes within cold-water coral Mounds. The most prominent result of diagenetic alteration of the primary sediment composition is the absence or poor preservation of aragonitic coral skeletons in certain depth intervals associated with lithification.This study focuses on the enrichment of redox-sensitive elements and the dissolution of primary magnetic ferric iron minerals in the depth interval below lithification levels. By combining the magnetic susceptibility with the XRF signal of Fe and Ti specifically, intervals with susceptibility variations related to the conversion of strongly magnetic into weakly magnetic iron species can be defined.In all three studied cores a succession is recognised with a lithified interval with aragonite dissolution and low-Mg calcite precipitates that is underlain by an interval of magnetite dissolution and of iron and manganese enrichment. For the most recent lithified interval it is demonstrated that initial lithification occurred before an erosional regime was in place, most likely near the end of interglacial or at the start of glacial periods. © 2011 Elsevier B.V
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Carbonate Mounds from the Gulf of Cadiz in relation to methane seepage: unrelated phenomena or coupling?
2010Co-Authors: Alina Stadnitskaia, Henk De Haas, Tjeerd C.e. Van Weering, Marianne Baas, R. Kreulen, Jaap S. Sinninghe DamstéAbstract:For more than decade, the formation of Carbonate Mounds, related ecosystem development and organization/functioning of the entire Mound habitats are subjects for a growing amount of studies and discussions. Carbonate Mounds from the Gulf of Cadiz are of special interest due to their association with active mud volcanoes within the El Arraiche mud volcano field. Such co-occurrence of ecologically contrasting phenomena anticipates complex biogeochemical interactions between a Carbonate Mound interior and seeping through hydrocarbon-rich fluids. To get closer in understanding of how methane affects a Carbonate Mound development in the gulf, a combination of inorganic and organic geochemical techniques was applied to two sedimentary cores collected from summits of Alfa and Beta Mounds. These Mounds were found at the NW slope of the Gimini MV at the Pen Duick Mound Province. We analyzed vertical distribution profiles of sulfate, sulfide, chlorinity, DIC in combination with hydrocarbon gas measurements and lipid biomarker study. To have estimates of Sea Surface Temperature (SST) during the Carbonate Mound formation, we applied the TEX86 (TetraEther indeX of tetraethers with 86 carbon atoms; Schouten et al., 2002) and the alkenone-based UK37 index (Muller et al., 1998). The pore-water data revealed the presence of brine inflow, which is consistent with the data of Hensen et al., (2007). The behavior of sulfide distribution profiles and 13C values from dissolved inorganic carbon (DIC) indicated that most of the sulfide and DIC are resulted from the microbial anaerobic oxidation of methane (AOM) processes. In contrast, the analysis of archaeal membrane lipids from distinct clades of AOM-mediating anaerobic methanotrophs showed exceedingly low concentrations of specific biomarkers, which is in contradiction with pore-water and gas chemistry data. Besides, AOM is the main cause for the increase of sedimentary alkalinity that leads to Carbonate precipitation. Instead, some sedimentary intervals associated with pore-water-detected AOM zone showed the presence of semi-dissolved coral branches, indicating thus rather acidic intra-environments. In this paper we discuss a potential “consecutive order” of biogeochemical processes in the close subsurface of Alfa and Beta Carbonate Mounds and outline the importance of careful interpretation of biogeochemical signatures related to past, modern and post seepage episodes.
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diagenetic processes in Carbonate Mound sediments at the south west rockall trough margin
Sedimentology, 2010Co-Authors: Cees Van Der Land, Furu Mienis, Henk De Haas, Rudy Swennen, Norbert Frank, Tjeerd C.e. Van WeeringAbstract:Cold water coral covered Carbonate Mounds at the south-west margin of the Rockall Trough form ridges several kilometres long and up to 380 m high. Piston cores obtained at three Mound crests reveal the complex internal structure of the Mound build up, with alternating unlithified coral-dominated intervals and lithified intervals. The most recent lithified interval is covered by corals embedded in a fine-grained matrix, comprising ca 11 000 years of continuous Mound evolution. Before this time 230Th/U dating shows the presence of several hiatuses in Mound build-up. Aragonitic coral material is absent or only present as mouldic porosity in the lithified intervals and coccoliths display widespread overgrowth. Downcore X-ray fluorescence scanning, computer tomography scan images and petrographic observations indicate different degrees of diagenetic alteration. The upper boundary of the most recent lithified interval shows some erosional features, but petrographic observations indicate that initial lithification of the sediments is not related to this erosive event or to long-term non-sedimentation, but to earlier sub-surface diagenesis. Organic matter oxidation and the subsequent lowering of the saturation state of the Carbonate system drives dissolution of the unstable aragonitic coral skeletons. Depending on the openness of the system, this can lead to precipitation of a more stable low-magnesium Carbonate. A model is presented describing the sedimentary and diagenetic processes leading to the formation of lithified intervals.