A detailed look at diapir piercement onto the ocean floor: New evidence from Santos Basin, offshore Brazil

Uri Schattner, Francisco José Lobo, Marga García, Mor Kanari, Raissa Basti Ramos, Michel Michaelovitch de Mahiques

Research output: Contribution to journalArticlepeer-review

Abstract

Diapir piercement through the ocean floor marks the final stages of a dynamic migration path. Once exhumed, a diapir extrudes from the seafloor, placing an obstacle for the flow of ocean bottom currents. While the hydrodynamic response of the flow has been previously studied, the detailed depositional and weathering modifications involved in the piercement process are less understood. To bridge this gap, we gathered already available multibeam bathymetric data, multichannel 2D seismic reflection profiles and collected new single-channel CHIRP profiles, Acoustic Doppler Current Profiler data and sediment samples across Santos Basin, offshore Brazil. In this region, the processes connecting the uppermost subsurface with the lowermost section of the water column are unknown. Data show three main stages of diapir exhumation: pre-, syn- and post-piercement into the seafloor. Extensional faults crown the pre-exposed diapir, before its piercement through the seafloor. Ocean bottom currents rework the top of the faults to form elongated depressions. The bottom currents tightly detour the diapir during and after its exposure at the seafloor. This interaction forms a drift and moat contourite depositional pattern. Our high-resolution data allow relating these morphologies to seafloor processes and distinguishing them from other reflector geometries related to diapir flank deformation, such as outward dipping of reflections. We further use this geometrical distinction to suggest a key for interpreting the exposure versus burial history of other diapirs worldwide.

Original languageEnglish
Pages (from-to)98-108
Number of pages11
JournalMarine Geology
Volume406
DOIs
StatePublished - 1 Dec 2018

Bibliographical note

Funding Information:
This work was funded by the São Paulo Research Foundation (FAPESP), grants 2010/06147-5 , 2014/08266-2 , and 2017/50191-8 . The authors are indebted to the crew and researchers of the RV Sirius (Brazilian Navy) and Alpha Crucis (University of São Paulo). MM de M acknowledges the Brazilian National Research Council (grant 303132/2014-0 and 401041/2014-0 ). F.J. Lobo acknowledges the Brazilian program “Ciência sem Fronteiras” funded by the CNPq, enabling him to conduct several research stages as “Pesquisador Visitante Especial” at the Instituto Oceanográfico, Universidade de São Paulo, under project number 401041/2014-0. M. García's research is funded by the Spanish Research Plan (TALUS Project CGL2015-74216-JIN ). U Schattner thanks IHS Kingdom Suite and Petrel-Schlumberger for providing academic licenses that enabled the seismic interpretation. We thank the editor-in-chief M. Rebesco, L. Somoza and an anonymous reviewer for commenting and improving this manuscript.

Publisher Copyright:
© 2018 Elsevier B.V.

Keywords

  • ADCP
  • Atlantic Ocean
  • Bathymetry
  • Contourite
  • Diapir
  • Ocean bottom currents
  • Salt tectonics
  • Seafloor morphology
  • Seismic reflection

ASJC Scopus subject areas

  • Oceanography
  • Geology
  • Geochemistry and Petrology

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