222
(1979–1980). This chapter introduces Part IV: Oil Spill Records in Deep Sea
Sediments and addresses a series of questions regarding MOSSFA in the sedimentary record:
• What were the characteristics of MOSSFA sedimentary inputs?
• What was the extent of MOSSFA on the seafloor?
• What postdepositional processes took place as a result of MOSSFA?
• Can MOSSFA be preserved in the sedimentary record?
MOSSFA sedimentary inputs were comprised of three main components (biogenic, lithogenic, and petrogenic), many of which were surface derived. MOSSFA
resulted in a four- to ten fold increase in bulk sediment accumulation rates, a two- to
three fold increase in oil-derived hydrocarbon concentrations, a two- to three-order of
magnitude increase in Corexit 9500A dispersant concentration, and two- to three fold
increases in surface-derived biotic material (e.g., planktic foraminifera, diatoms).
Estimates of the total spatial extent of MOSSFA on the seafloor of the northern GoM
range from 1030 to 35,425 km
2
, accounting for between 3.7% and 14.4% of the total
petroleum released during DWH. Increased microbial respiration of organic carbon
caused depleted surface sediment oxygen, intensifying reducing conditions up to
3 years following DWH. Multiple proxies provided evidence of multi-year preservation of both oil residue in the sediments associated with DWH, MOSSFA, and the
sedimentary event in the geologic record. Despite confounding factors in the southern
GoM including regional events (e.g., volcanoes, hurricanes) and complex hydrocarbon backgrounds (e.g., natural seeps, oil, and gas infrastructure), multiple sedimentary proxies have provided evidence of degraded Ixtoc 1 oil-residue input and the
MOSSFA sedimentary event preserved in the geologic record greater than 35 years
after Ixtoc 1. Federal and international policies can be benefitted by incorporating
MOSSFA with regard to response strategies, weighing the ecological trade-off
between oiled coastlines and offshore benthic environments.
Keywords MOSSFA · Deepwater Horizon · Ixtoc 1 · Seafloor · Oil residue ·
Sedimentation
13.1 Introduction
The amount of oil released from the Deepwater Horizon (DWH) subsurface marine
petroleum well blowout to the northern Gulf of Mexico (GoM) is somewhat controversial. McNutt et al. (2012) calculated that the cumulative release was approximately 4.9 million barrels, of which 0.8 million barrels were collected. Joye et al.
(2011) figured the amount released to the environment was between 4.5 and 6.3
million barrels. Griffiths (2012) estimated that the cumulative discharge was 5.4
million barrels of which 4.6 million barrels entered the northern GoM. A court settlement (US District Court 2015) set the estimate at 4 million barrels of cumulative
release with 3.2 million barrels released to the northern GoM following response
efforts. The release of petroleum into the northern GoM resulted in the occurrence
P. T. Schwing et al.
(1979–1980). This chapter introduces Part IV: Oil Spill Records in Deep Sea
Sediments and addresses a series of questions regarding MOSSFA in the sedimentary record:
• What were the characteristics of MOSSFA sedimentary inputs?
• What was the extent of MOSSFA on the seafloor?
• What postdepositional processes took place as a result of MOSSFA?
• Can MOSSFA be preserved in the sedimentary record?
MOSSFA sedimentary inputs were comprised of three main components (biogenic, lithogenic, and petrogenic), many of which were surface derived. MOSSFA
resulted in a four- to ten fold increase in bulk sediment accumulation rates, a two- to
three fold increase in oil-derived hydrocarbon concentrations, a two- to three-order of
magnitude increase in Corexit 9500A dispersant concentration, and two- to three fold
increases in surface-derived biotic material (e.g., planktic foraminifera, diatoms).
Estimates of the total spatial extent of MOSSFA on the seafloor of the northern GoM
range from 1030 to 35,425 km
2
, accounting for between 3.7% and 14.4% of the total
petroleum released during DWH. Increased microbial respiration of organic carbon
caused depleted surface sediment oxygen, intensifying reducing conditions up to
3 years following DWH. Multiple proxies provided evidence of multi-year preservation of both oil residue in the sediments associated with DWH, MOSSFA, and the
sedimentary event in the geologic record. Despite confounding factors in the southern
GoM including regional events (e.g., volcanoes, hurricanes) and complex hydrocarbon backgrounds (e.g., natural seeps, oil, and gas infrastructure), multiple sedimentary proxies have provided evidence of degraded Ixtoc 1 oil-residue input and the
MOSSFA sedimentary event preserved in the geologic record greater than 35 years
after Ixtoc 1. Federal and international policies can be benefitted by incorporating
MOSSFA with regard to response strategies, weighing the ecological trade-off
between oiled coastlines and offshore benthic environments.
Keywords MOSSFA · Deepwater Horizon · Ixtoc 1 · Seafloor · Oil residue ·
Sedimentation
13.1 Introduction
The amount of oil released from the Deepwater Horizon (DWH) subsurface marine
petroleum well blowout to the northern Gulf of Mexico (GoM) is somewhat controversial. McNutt et al. (2012) calculated that the cumulative release was approximately 4.9 million barrels, of which 0.8 million barrels were collected. Joye et al.
(2011) figured the amount released to the environment was between 4.5 and 6.3
million barrels. Griffiths (2012) estimated that the cumulative discharge was 5.4
million barrels of which 4.6 million barrels entered the northern GoM. A court settlement (US District Court 2015) set the estimate at 4 million barrels of cumulative
release with 3.2 million barrels released to the northern GoM following response
efforts. The release of petroleum into the northern GoM resulted in the occurrence
P. T. Schwing et al.