Sediment studies associated with drilling activity on a tropical shallow shelf

Area of Science:

• Marine geology and environmental science.
• Sedimentology and oceanography of tropical shelf systems.

Background:

• Tropical shelves are dynamic mixed carbonate-siliciclastic environments.
• Environmental impact assessments are crucial for offshore drilling operations.

Purpose of the Study:

• To monitor environmental changes in seafloor sediments around a shallow-water exploratory well.
• To assess the short-term and long-term sedimentological impacts of drilling in the Potiguar Basin.

Main Methods:

• Field sampling across 16 stations in 4 radials (50-500m) around an exploratory well.
• Analysis of sediment properties (grain size, texture, mineralogy, carbonate, organic matter) in 0-2cm and 0-10cm layers.
• Comparison of pre-drilling, 3-month, and 12-month post-drilling sediment samples across 3 cruises.

Main Results:

• Seafloor sediments are primarily bioclastic and poorly sorted.
• Minor, temporary changes in grain size and siliciclastic content observed in surficial sediments (0-2cm) near the well.
• Sediment characteristics returned to pre-drilling conditions by 12 months post-drilling.

Conclusions:

• Offshore drilling had no significant long-term sedimentological impact on this tropical shelf.
• High ocean dynamics effectively restored the original seafloor environment.
• The study highlights the resilience of dynamic marine ecosystems to localized anthropogenic disturbances.