The Pelotas Basin oil province revealed – new interpretation from long offset 2D seismic data

Saunders, Mike; Bowman, Scott A.

doi:10.3997/1365-2397.32.10.78249

Cited by 2 publications

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“…The Rio Grande Cone (RGC) consists of a 5 km-thick sediment pile that is thicker than adjacent areas 30 , i.e., a depocenter, formed by the accumulation of early Miocene-present fine-grained sediments in the Pelotas Basin, southern Brazil 31 (Figs. 1 and 2 ).…”

Section: Methane Migration Pathways In a Collapsing Depocentermentioning

confidence: 99%

Gravity complexes as a focus of seafloor fluid seepage: the Rio Grande Cone, SE Brazil

Ketzer

Praeg

Augustin

et al. 2023

Sci Rep

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Seafloor methane emissions can affect Earth’s climate and ocean chemistry. Vast quantities of methane formed by microbial decomposition of organic matter are locked within gas hydrate and free gas on continental slopes, particularly in large areas with high sediment accumulations such as deep-sea fans. The release of methane in slope environments has frequently been associated with dissociation of gas hydrates near the edge of the gas hydrate stability zone on the upper slope, with discharges in greater water depths less understood. Here we show, using data from the Rio Grande Cone (western South Atlantic), that the intrinsic, gravity-induced downslope collapse of thick slope sediment accumulations creates structures that serve as pathways for gas migration, unlocking methane and causing seafloor emissions via giant gas flares in the water column. The observed emissions in the study region (up to 310 Mg year−1) are three times greater than estimates for the entire US North Atlantic margin and reveal the importance of collapsing sediment accumulations for ocean carbon cycling. Similar outgassing systems on the Amazon and Niger fans suggest that gravity tectonics on passive margins is a common yet overlooked mechanism driving massive seafloor methane emissions in sediment-laden continental slopes.

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Section: Methane Migration Pathways In a Collapsing Depocentermentioning

confidence: 99%

Gravity complexes as a focus of seafloor fluid seepage: the Rio Grande Cone, SE Brazil

Ketzer

Praeg

Augustin

et al. 2023

Sci Rep

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“…Contreras et al, 2010), and petroleum potential (e.g. Conti et al, 2017;Fontana, 1989;Morales et al, 2020;Saunders & Bowman, 2014).…”

Section: Case Study: the Pelotas Basinmentioning

confidence: 99%

High‐resolution sedimentary budget quantification – Example from the Cenozoic deposits in the Pelotas Basin, South Atlantic

Rohais

Lovecchio²,

Abreu³

et al. 2021

Basin Research

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In this paper, we propose a high-resolution (HR) sedimentary budget quantification at basin-scale for the Cenozoic deposits of the Pelotas Basin (South Atlantic). A new workflow is implemented including five main steps: (1) basin-scale analysis and characterization, (2) quality control and selection of reference 2D dip-sections,(3) HR seismic stratigraphy analysis, (4) sediment supply estimation taking into account lithology and porosity corrections and then (5) the estimation of the sedimentary budget curve including 41 time-intervals for the last 65 Myr. Variance ranges were determined considering the parameters of the method on the case study. The main uncertainties are related to the seismic velocities for the time-to-depth conversion (5%-22%), the method for lithological parameters quantification and associated porosity correction (4.4%-14.3%), the absolute ages of stratigraphic markers (1%-25%), and the proportion of in-situ sediment production (0.3%-0.5%). For the very first time, this method allows the identification of several cycles from an entire sedimentary basin fill characterized by pulses of sediment supply (Qs) whose growth phase lasts less than 1 Myr, followed by a constant phase lasting 1-2 Myr, and finally an exponentially decreasing phase lasting 2-5 Myr. These pulses alternate with phases where the sediment supply was very low for intervals of ca. 1-5 Myr. Ten major pulses were recognized during the Cenozoic. We propose that the sediment supply dynamic in the Pelotas basin records the orogenic phases of the Andes located more than 2,000 km upstream. The recorded Qs pulses in the basin are out of phase with respect to the active tectonic phases of the Central Andes. Finally, by comparing the volume of preserved sediment and the production capacity of the catchment, we suggest that a source of sediment in addition to the Brazilian craton and the Andes should be envisaged, potentially associated with deep-water oceanic circulation.

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The Pelotas Basin oil province revealed – new interpretation from long offset 2D seismic data

Cited by 2 publications

References 0 publications

Gravity complexes as a focus of seafloor fluid seepage: the Rio Grande Cone, SE Brazil

Gravity complexes as a focus of seafloor fluid seepage: the Rio Grande Cone, SE Brazil

High‐resolution sedimentary budget quantification – Example from the Cenozoic deposits in the Pelotas Basin, South Atlantic

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