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Bioherm

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Jonathan S Price – 1st expert on this subject based on the ideXlab platform

  • effect of mine dewatering on the peatlands of the james bay lowland the role of marine sediments on mitigating peatland drainage
    Hydrological Processes, 2013
    Co-Authors: Peter Whittington, Jonathan S Price

    Abstract:

    The wetlands of the James Bay Lowland comprise one of largest wetland complexes in the world, in part due to the properties (thickness and hydraulic conductivity) of the marine sediment (MS) that underlay them. Dewatering of an open-pit diamond mine is depressurizing the surrounding Silurian bedrock below the MS. Prior to mining, it was assumed that these MS would largely isolate the overlying peatlands from the depressurized regional bedrock aquifer. To assess this isolation, we instrumented a 1.5 km long transect of wells and piezometers located within the zone of the mine’s influence that crossed a sequence of bogs, fens, and bedrock outcrops (Bioherms). Results were differentiated between those areas with no MS (near Bioherms) and those underlain by MS (non-Bioherm) along the transect. Between 2007 and 2010 at near-Bioherm and non-Bioherm locations, average peat water tables declined 71 and 31 cm, and hydraulic head declined 66 and 32 cm, in Bioherm and non-Bioherm locations, respectively. Gradients varied from near zero (−0.001) at the start of dewatering to −0.03 (after 5 years) in non-Bioherm areas and from −0.20 to −0.45 in near-Bioherm areas. These gradients corresponded to fluxes (groundwater recharge) of approximately −0.26 mm/day and −2.1 mm/day, in non- and near-Bioherm areas, respectively. Specific discharge (recharge) determined using the known mine dewatering rate and drawdown cone heads and areas corresponded well with measured recharge determined in the non-Bioherm transect locations. A simple rearrangement of Darcy’s Law used to calculate the specific discharge highlighted how the ratio of hydraulic conductivity to the thickness of the MS can be used to assess vulnerable areas. Therefore, given the increasing development in Ontario’s Far North, considerable attention must be given to both the thickness and hydraulic conductivity of MS. Copyright © 2013 John Wiley & Sons, Ltd.

  • Effect of mine dewatering on peatlands of the James Bay Lowland: the role of Bioherms
    Hydrological Processes, 2012
    Co-Authors: Peter Whittington, Jonathan S Price

    Abstract:

    The James Bay Lowland host one of the largest wetland complexes in the world in part due to the low permeability of marine sediments that suppress groundwater seepage losses. Dewatering of an open-pit diamond mine in the area has depressurized the regional bedrock aquifer. Bioherms, fractured limestone outcroppings formed from ancient coral reefs that protrude to the peatland surface, lack this mantle of low-permeability sediments and provide a direct connection between the peatland (surficial) and the regional (bedrock) aquifers. Well transects and piezometer nests were installed around seven Bioherms in the depressurized zone and one in a non-affected zone (control) to monitor the water table drawdown and change in hydraulic gradients around the Bioherms. Water tables in the affected Bioherms decreased between 2 and 4 m in the first 4 years of dewatering. The drawdown in the Bioherms caused a localized water table drawdown in the peat surrounding the Bioherms that extended to approximately 30 m from the edge of the Bioherm during a dry period. Under wet conditions, drawdown was similar to that at the control site. Hydraulic gradients in the peat (which typically are very small) increased over the field seasons and in a few locations exceeded 1. These gradients represented significant losses to the local, near Bioherm, system as at many of the locations surrounding the Bioherms vertical seepage losses ranged between 1 and 4 mm/day, which are similar to the seasonal average evaporative water loss of ~ 3 mm/day. The Bioherms are acting as efficient drainage nodes; however, their influence is localized to the peat immediately (~ 

Vincent Rommevaux – 2nd expert on this subject based on the ideXlab platform

  • The role of topography and erosion in the development and architecture of shallow-water coral Bioherms (Tortonian–Messinian, Cabo de Gata, SE Spain)
    Palaeogeography Palaeoclimatology Palaeoecology, 2020
    Co-Authors: Raphaël Bourillot, Emmanuelle Vennin, Christophe Kolodka, Jean-marie Rouchy, Antonio Caruso, Christophe Durlet, Christian Chaix, Vincent Rommevaux

    Abstract:

    23 pagesInternational audienceDuring the Miocene, Mediterranean shallow-water carbonates were rich in scleractinian corals, which thrive in various depositional settings. A Tortonian–Messinian Bioherm belt developing in a heterozoan-dominated ramp was investigated along a 1.2 km continuous transect located in the Cabo de Gata region. The interval studied displays four depositional environments from mid-to-inner ramp, dominated by swell waves and storm energy, deposited as a single, large-scale depositional sequence during a 3rd to 4th order transgressive–regressive cycle. The Bioherms grew in three phases, and were essentially composed of inplace primary frameworks. Three coral genera were the main framebuilders (Porites, Tarbellastrea and rare Siderastrea), associated with melobesioid and mastophoroid red algae and bryozoans as secondary framebuilders. The corals display five morphotypes, from a fast-growing branched type to slow-growing domal to plate morphologies, with an uncommon form of mesh Porites as the dominant morphotype. Changes in coral morphotype and composition of micro-encrusters communities reveal changes in hydrodynamics, detrital influx and perhaps nutrient levels. Bioherms architecture was driven by sea level, palaeotopography and erosion. The coral framework was affected during its development by erosion surfaces metres to tens of metres deep and hundreds of metres wide. Unexpectedly, these surfaces are better developed on the inner edges of the Bioherms. This could indicate the circulation of strong bottom currents between the volcanic palaeohighs and the synoptic relief created by the buildups. Finally, a major sub-aerial erosional episode associated with increasing detrital influxes, ended Bioherm development, thus allowing the colonization of the dead coral substratum by red algae

  • The role of topography and erosion in the development and architecture of shallow-water coral Bioherms (Tortonian–Messinian, Cabo de Gata, SE Spain)
    Palaeogeography Palaeoclimatology Palaeoecology, 2009
    Co-Authors: Raphaël Bourillot, Emmanuelle Vennin, Christophe Kolodka, Jean-marie Rouchy, Antonio Caruso, Christophe Durlet, Christian Chaix, Vincent Rommevaux

    Abstract:

    Abstract During the Miocene, Mediterranean shallow-water carbonates were rich in scleractinian corals, which thrive in various depositional settings. A Tortonian–Messinian Bioherm belt developing in a heterozoan-dominated ramp was investigated along a 1.2 km continuous transect located in the Cabo de Gata region. The interval studied displays four depositional environments from mid-to-inner ramp, dominated by swell waves and storm energy, deposited as a single, large-scale depositional sequence during a 3rd to 4th order transgressive–regressive cycle. The Bioherms grew in three phases, and were essentially composed of in-place primary frameworks. Three coral genera were the main framebuilders (Porites, Tarbellastrea and rare Siderastrea), associated with melobesioid and mastophoroid red algae and bryozoans as secondary framebuilders. The corals display five morphotypes, from a fast-growing branched type to slow-growing domal to plate morphologies, with an uncommon form of mesh Porites as the dominant morphotype. Changes in coral morphotype and composition of micro-encrusters communities reveal changes in hydrodynamics, detrital influx and perhaps nutrient levels. Bioherms architecture was driven by sea level, palaeotopography and erosion. The coral framework was affected during its development by erosion surfaces metres to tens of metres deep and hundreds of metres wide. Unexpectedly, these surfaces are better developed on the inner edges of the Bioherms. This could indicate the circulation of strong bottom currents between the volcanic palaeohighs and the synoptic relief created by the buildups. Finally, a major sub-aerial erosional episode associated with increasing detrital influxes, ended Bioherm development, thus allowing the colonization of the dead coral substratum by red algae.

Peter Whittington – 3rd expert on this subject based on the ideXlab platform

  • effect of mine dewatering on the peatlands of the james bay lowland the role of marine sediments on mitigating peatland drainage
    Hydrological Processes, 2013
    Co-Authors: Peter Whittington, Jonathan S Price

    Abstract:

    The wetlands of the James Bay Lowland comprise one of largest wetland complexes in the world, in part due to the properties (thickness and hydraulic conductivity) of the marine sediment (MS) that underlay them. Dewatering of an open-pit diamond mine is depressurizing the surrounding Silurian bedrock below the MS. Prior to mining, it was assumed that these MS would largely isolate the overlying peatlands from the depressurized regional bedrock aquifer. To assess this isolation, we instrumented a 1.5 km long transect of wells and piezometers located within the zone of the mine’s influence that crossed a sequence of bogs, fens, and bedrock outcrops (Bioherms). Results were differentiated between those areas with no MS (near Bioherms) and those underlain by MS (non-Bioherm) along the transect. Between 2007 and 2010 at near-Bioherm and non-Bioherm locations, average peat water tables declined 71 and 31 cm, and hydraulic head declined 66 and 32 cm, in Bioherm and non-Bioherm locations, respectively. Gradients varied from near zero (−0.001) at the start of dewatering to −0.03 (after 5 years) in non-Bioherm areas and from −0.20 to −0.45 in near-Bioherm areas. These gradients corresponded to fluxes (groundwater recharge) of approximately −0.26 mm/day and −2.1 mm/day, in non- and near-Bioherm areas, respectively. Specific discharge (recharge) determined using the known mine dewatering rate and drawdown cone heads and areas corresponded well with measured recharge determined in the non-Bioherm transect locations. A simple rearrangement of Darcy’s Law used to calculate the specific discharge highlighted how the ratio of hydraulic conductivity to the thickness of the MS can be used to assess vulnerable areas. Therefore, given the increasing development in Ontario’s Far North, considerable attention must be given to both the thickness and hydraulic conductivity of MS. Copyright © 2013 John Wiley & Sons, Ltd.

  • Effect of mine dewatering on peatlands of the James Bay Lowland: the role of Bioherms
    Hydrological Processes, 2012
    Co-Authors: Peter Whittington, Jonathan S Price

    Abstract:

    The James Bay Lowland host one of the largest wetland complexes in the world in part due to the low permeability of marine sediments that suppress groundwater seepage losses. Dewatering of an open-pit diamond mine in the area has depressurized the regional bedrock aquifer. Bioherms, fractured limestone outcroppings formed from ancient coral reefs that protrude to the peatland surface, lack this mantle of low-permeability sediments and provide a direct connection between the peatland (surficial) and the regional (bedrock) aquifers. Well transects and piezometer nests were installed around seven Bioherms in the depressurized zone and one in a non-affected zone (control) to monitor the water table drawdown and change in hydraulic gradients around the Bioherms. Water tables in the affected Bioherms decreased between 2 and 4 m in the first 4 years of dewatering. The drawdown in the Bioherms caused a localized water table drawdown in the peat surrounding the Bioherms that extended to approximately 30 m from the edge of the Bioherm during a dry period. Under wet conditions, drawdown was similar to that at the control site. Hydraulic gradients in the peat (which typically are very small) increased over the field seasons and in a few locations exceeded 1. These gradients represented significant losses to the local, near Bioherm, system as at many of the locations surrounding the Bioherms vertical seepage losses ranged between 1 and 4 mm/day, which are similar to the seasonal average evaporative water loss of ~ 3 mm/day. The Bioherms are acting as efficient drainage nodes; however, their influence is localized to the peat immediately (~