Abstract
The southern Gulf of Mexico (sGoM) is home to an extensive oil recovery and development infrastructure. In addition, the basin harbors sites of submarine hydrocarbon seepage and receives terrestrial inputs from bordering rivers. We used stable carbon, nitrogen, and radiocarbon analyses of bulk sediment organic matter to define the current baseline isoscapes of surface sediments in the sGoM and determined which factors might influence them. These baseline surface isoscapes will be useful for accessing future environmental impacts. We also examined the region for influence of hydrocarbon deposition in the sedimentary record that might be associated with hydrocarbon recovery, spillage and seepage, as was found in the northern Gulf of Mexico (nGoM) following the Deepwater Horizon (DWH) oil spill in 2010. In 1979, the sGoM experienced a major oil spill, Ixtoc 1. Surface sediment δ13C values ranged from -22.4‰ to -19.9‰, while Δ14C values ranged from -337.1‰ to -69.2‰. Sediment δ15N values ranged from 2.8‰ to 7.2‰, while the %C on a carbonate-free basis ranged in value of 0.65% to 3.89% and %N ranged in value of 0.09% to 0.49%. Spatial trends for δ13C and Δ14C were driven by water depth and distance from the coastline, while spatial trends for δ15N were driven by location (latitude and longitude). Location and distance from the coastline were significantly correlated with %C and %N. At depth in two of twenty (10%) core profiles, we found negative δ13C and Δ14C excursions from baseline values in bulk sedimentary organic material, consistent with either oil-residue deposition or terrestrial inputs, but likely the latter. We then used 210Pb dating on those two profiles to determine the time in which the excursion-containing horizons were deposited. Despite the large spill in 1979, no evidence of hydrocarbon residue remained in the sediments from this specific time period.
Highlights
The southern Gulf of Mexico is a diverse ecosystem of lagoons, river catchments, and shallow shelves, and is home to many important economic activities
Surface sediment of all samples range in δ13C values from -22.4‰ to -19.9‰ (S1 Table) and have an average value of -21.2 ± 0.6‰, while Δ14C values range from -337.1‰ to -69.2‰ (S1 Table), and have an average of -164.6 ± 54.0‰ (n = 72)
The %C on a Southern Gulf of Mexico seafloor isoscapes carbonate-free basis range in value from 0.65% to 3.89% (S1 Table), and average 1.45 ± 0.59% (n = 66), while %N range in value from 0.09% to 0.49% (S1 Table), with an average of 0.18 ± 0.07% (n = 66)
Summary
The southern Gulf of Mexico (sGoM) is a diverse ecosystem of lagoons, river catchments, and shallow shelves, and is home to many important economic activities. The two most important economic drivers are the fishing industry and the oil industry [2]. Exploration for oil reached the region in the early 1950’s and oil exploitation in the 1970’s [1]. The sGoM is home to a robust oil recovery infrastructure, with over 75% of Mexican oil production occurring in the region [6]. Offshore oil exploitation began in 1976 and by 2016, the area had 256 platforms, with a crude oil production of 1,701,000 barrels per day [1]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
