The first record of gas flares along the Peruvian convergent margin: The case of the hydrocarbon-prolific Talara Basin

Abstract

During the last few decades, streams of gas bubbles released from the seafloor have been discovered around the world with hydroacoustic systems. That being said, such a discovery had not occurred along the Peruvian convergent margin. For the first time, 75 zones of gas flares were imaged with high-resolution swath bathymetry in the well-known hydrocarbon-rich Talara Basin (4°S–5°S) of the northern Peru margin. 78% of all flares occur along the shelf, while the remaining 22% is found between the shelf break and the upper slope (up to water depths of 1700 m in the study area). Almost all flares (96%) are within the permanent oxygen minimum zone (OMZ) and above the top of the gas hydrate stability zone (GHSZ). Gas flares are not observed between the top of the GHSZ and water depths of 1300 m. Beneath the gas flare-free region, the additional 4% contains one of the most impressive gas flares of 1310 m height, which crosses the top of the GHSZ for 230 m in the water column. The projection of the largest gas flare onto seismic data shows a spatial link with bottom-simulating reflections (BSRs), landward-dipping strata, and a deep half-graben. Despite assumptions and uncertainties, we suggest that a total volume gas flux of 7–45 × 106 mol CH4.yr−1 (average of 26 × 106 mol CH4.yr−1) is being released in the form of gas bubbles in the study area. From our findings, we propose that other parts of the Peru margin are likely seeping natural gas from the seafloor, with hydrocarbon-dependent deep-sea biological communities, more so than previously thought.