246
detection in the sedimentary record by smearing and diluting the signature to below
detection. If there is a lack of bioturbation immediately following a deposition
event, it is possible for burial by subsequent sedimentation to increase the preservation potential as long as the depositional layer is deeper (downcore) than the depth
of bioturbation (Fig. 14.2). Burial of the impacted layer by subsequent sedimentation will lead to the highest potential for preservation and detection in the sedimentary record (Fig. 14.2). Areas with higher sedimentation rates generally have a
higher probability of burial. Some of the indicators of oiled sedimentation are susceptible to degradation and will become more difficult to detect over time (Romero
et al. 2020). With subsequent burial, compaction will lead to thinning of the depositional layer, making it more difficult to detect and requiring high-resolution sampling. The remobilization of impacted sediments can lead to a lack of preservation
at the location of the initial deposition, as well as modification of the geographic
extent of oil-contaminated sediments on the seafloor. This often is a function of
resuspension and downslope transport to deeper water with the potential for focusing contaminated sediments in areas of high deposition, and/or distribution over a
broader area. Research shows that seafloor morphology affects resuspension
(Diercks et al. 2018; Turnewitsch et al. 2017) and redistribution (Durrieu De Madron
et al. 2017), as well as subsequent settling and deposition of material (Turnewitsch
et al. 2013, 2004) focusing erosion and deposition on specific areas on the seafloor.
This provides a mechanism for uneven sediment deposition and distribution within
a given time frame.
14.7 Critical Approaches/Methods
The investigation of the DWH blowout in the sedimentary system was developed
using a variety of approaches that maximized the detection of sedimentary impacts
without pre-existing knowledge of the evolution and processes influencing sedimentation associated with a deepwater oil blowout. This included the rapid collection of sediment cores, an annual time series to characterize the event and its
evolution in the sedimentary system over subsequent years, high-resolution sampling to maximize temporal resolution, and a multidisciplinary approach to determine diagnostic as well as corroborative indicators of oil-contaminated sediment
deposition.
14.7.1 Rapid Response and Collection of Cores
The rapid collection of sediment cores following the initiation of the blowout event
allowed for investigation of the immediate sedimentary response and benthic
impacts and the use of time-sensitive indicators to define sedimentation associated
with the event. Time-sensitive indicators included short-lived chronometers (
234
Th xs )
R. A. Larson et al.
detection in the sedimentary record by smearing and diluting the signature to below
detection. If there is a lack of bioturbation immediately following a deposition
event, it is possible for burial by subsequent sedimentation to increase the preservation potential as long as the depositional layer is deeper (downcore) than the depth
of bioturbation (Fig. 14.2). Burial of the impacted layer by subsequent sedimentation will lead to the highest potential for preservation and detection in the sedimentary record (Fig. 14.2). Areas with higher sedimentation rates generally have a
higher probability of burial. Some of the indicators of oiled sedimentation are susceptible to degradation and will become more difficult to detect over time (Romero
et al. 2020). With subsequent burial, compaction will lead to thinning of the depositional layer, making it more difficult to detect and requiring high-resolution sampling. The remobilization of impacted sediments can lead to a lack of preservation
at the location of the initial deposition, as well as modification of the geographic
extent of oil-contaminated sediments on the seafloor. This often is a function of
resuspension and downslope transport to deeper water with the potential for focusing contaminated sediments in areas of high deposition, and/or distribution over a
broader area. Research shows that seafloor morphology affects resuspension
(Diercks et al. 2018; Turnewitsch et al. 2017) and redistribution (Durrieu De Madron
et al. 2017), as well as subsequent settling and deposition of material (Turnewitsch
et al. 2013, 2004) focusing erosion and deposition on specific areas on the seafloor.
This provides a mechanism for uneven sediment deposition and distribution within
a given time frame.
14.7 Critical Approaches/Methods
The investigation of the DWH blowout in the sedimentary system was developed
using a variety of approaches that maximized the detection of sedimentary impacts
without pre-existing knowledge of the evolution and processes influencing sedimentation associated with a deepwater oil blowout. This included the rapid collection of sediment cores, an annual time series to characterize the event and its
evolution in the sedimentary system over subsequent years, high-resolution sampling to maximize temporal resolution, and a multidisciplinary approach to determine diagnostic as well as corroborative indicators of oil-contaminated sediment
deposition.
14.7.1 Rapid Response and Collection of Cores
The rapid collection of sediment cores following the initiation of the blowout event
allowed for investigation of the immediate sedimentary response and benthic
impacts and the use of time-sensitive indicators to define sedimentation associated
with the event. Time-sensitive indicators included short-lived chronometers (
234
Th xs )
R. A. Larson et al.