Tectonic BSR Hypothesis in the Peruvian Margin: A Forgotten Way to See Marine Gas Hydrate Systems at Convergent Margins

Herbozo G.; Kukowski N.; Pecher I. · World Atlas of Submarine Gas Hydrates in Continental Margins (2022) · DOI: 10.1007/978-3-030-81186-0_33

Resumen

Along the Peruvian convergent margin, which is controlled by long-lived subduction erosion and primary productive coastal upwelling, gas hydrate-related bottom simulating reflections (BSRs) are the primary indicators for the existence of marine gas hydrate systems. Although conditions are favorable in the entire area for hydrates and free gas, BSRs are absent in some parts of this active convergent margin. The ‘Tectonic BSR Hypothesis’ postulates that this is due to subsidence and, thus, the tectonic suppression of the free gas zone. When uplift occurs, however, the free gas zone appears. We will examine 27 years old unpublished, multi-channel seismic data acquired by the hydrocarbon industry in the Central Peru margin to identify the BSR distribution in the area, covering the unexplored areas of the Central Trujillo Basin, the southernmost end of Lima Basin and the Pisco Basin. Based on this data set and the intergration of Ocean Drilling Program findings, three major differences are observed: (1) The existence of a continuous BSR in the quasi-tectonically stable Trujillo Basin, which has been characterized by slow subduction erosion since the Miocene; (2) The absence of BSRs in the strongly subsiding Lima and Pisco basins, which were affected by fast subduction erosion after the southward passage of the Nazca Ridge in the Late Miocene; (3) The appearance of BSRs in the southernmost end of the Pisco Basin related to seafloor uplift. These results lead us to consider that the Tectonic BSR Hypothesis may be useful in understanding marine gas hydrate systems at both convergent margins undergoing subduction erosion and non-convergent margins, controlled by vertical tectonics. © Springer Nature Switzerland AG 2022, corrected publication 2022.