Metal/Ca ratios in pockmarks and adjacent sediments on the SW Atlantic slope: Implications for redox potential and modern seepage

Author(s)

dos Santos, Rosangela Felicio ^[1] ; Nagaoka, Doris ^[1] ; Ramos, Raissa Basti ^[1] ; Salaroli, Alexandre Barbosa ^[1] ; Taniguchi, Satie ^[1] ; Lopes Figueira, Rubens Cesar ^[1] ; Bicego, Marcia Caruso ^[1] ; Lobo, Francisco Jose ^[2] ; Schattner, Uri ^[3] ; de Mahiques, Michel Michaelovitch ^{[1, 4]}

Affiliation

^[1] Univ Sao Paulo, Oceanog Inst, Praca Oceanog 191, BR-05508120 Sao Paulo - Brazil

^[2] Univ Granada, Inst Andaluz Ciencias Tierra, CSIC, Ave las Palmeras 4, Armilla - Spain

^[3] Univ Haifa, Dr Moses Strauss Dept Marine Geosci, Leon H Charney Sch Marine Sci, Haifa - Israel

^[4] Univ Sao Paulo, Inst Energy & Environm, Sao Paulo - Brazil

• Document type: Journal article
• Source: JOURNAL OF GEOCHEMICAL EXPLORATION; v. 192, p. 163-173, SEP 2018.
• Web of Science Citations: 1

Abstract

Metal/Ca ratios and their corresponding enrichment factors (EFs) in bulk sediment samples collected at a mixed carbonate-siliciclastic continental slope setting with an extensive pockmark field were measured and analyzed to find evidence of lateral differences in the redox potential and recent seepage activity inside the pockmarks. The analyzed ratios point to metal enrichments that indicate variations in the redox potential inside the pockmarks compared to the adjacent areas, as shown by the Cu/Ca, Ni/Ca and Zn/Ca EFs. Slight but statistically significant differences in the Mg/Ca ratios indicated that the formation of Mg-enriched carbonates within the pockmarks is presently taking place, attesting the maintenance of seepage in the shallow sedimentary column. Recent seepage activity was also confirmed by the upward enrichment of Ba in the sedimentary column. Our study provides direct evidence for pockmark activity and reinforces the need for an extended analysis of the geochemistry of natural seepages on the SW Atlantic margin, an area that has still not been studied in relation to this subject. (AU)

• FAPESP's process: 16/22194-0 - Anomalous bottom features on the upper slope off Southern Brazil
• Grantee: Michel Michaelovitch de Mahiques
• Support Opportunities: Regular Research Grants
• FAPESP's process: 16/24379-7 - Utilization of geochemical proxies in an area of pockmarks (Southern Brazilian continental slope)
• Grantee: Rosângela Felício dos Santos
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• FAPESP's process: 17/50191-8 - Dymamics of salt dome exhumation on the ocean floor, focusing on Santos basin offshore Brazil
• Grantee: Michel Michaelovitch de Mahiques
• Support Opportunities: Regular Research Grants
• FAPESP's process: 14/08266-2 - Continental slope morphological features on the SE Brazilian Margin: active tectonics versus modern oceanographic conditions
• Grantee: Michel Michaelovitch de Mahiques
• Support Opportunities: Regular Research Grants
• FAPESP's process: 10/06147-5 - Increase of the research capabilities in oceanography and related sciences in São Paulo State, Brazil
• Grantee: Michel Michaelovitch de Mahiques
• Support Opportunities: Research Program on Global Climate Change - Regular Grants