Seaward‐Dipping Reflector Influence on Seafloor Magnetostratigraphy—A Pelotas Basin View

Previous works used marine magnetic survey data and interpreted magnetic anomalies related to seaward‐dipping reflectors (SDRs) as oceanic crust or SDR age constraints in the South Atlantic Ocean. However, we advise against using SDR‐related magnetic anomalies to constrain ages because of the mostly low‐dipping geometry causing the overlapping of rocks extruded during periods of different polarities. The data are difficult to interpret correctly because of the SDR compositional heterogeneity, sedimentary intercalations, variations in package thickness with different compositions and magnetic polarities, and the absence of a link between the SDR magmatic position and age. SDR‐related magnetic anomalies are mainly caused by magnetic susceptibility contrasts rather than remanent magnetism. Due to this complexity, the SDR geometry and variable composition make SDR‐related magnetic anomalies challenging to use for age constraints. The Pelotas Basin SDRs age cannot be estimated by magnetostratigraphy, and this method likely cannot constrain the age of any SDR wedge.

[1]  P. Vasconcelos,et al.  Geochronology of the Paraná-Etendeka large igneous province , 2021 .

[2]  C. Devey,et al.  13 million years of seafloor spreading throughout the Red Sea Basin , 2021, Nature Communications.

[3]  L. Geoffroy,et al.  Conjugate volcanic passive margins in the austral segment of the South Atlantic – Architecture and development , 2021 .

[4]  N. Kusznir,et al.  Origin, composition and relative timing of seaward dipping reflectors on the Pelotas rifted margin , 2020 .

[5]  W. Buck,et al.  Estimating emplacement rates for seaward-dipping reflectors associated with the U.S. East Coast Magnetic Anomaly , 2018, Geophysical Journal International.

[6]  F. Chemale,et al.  Age of basement rocks from the Maurice Ewing Bank and the Falkland/Malvinas Plateau , 2018, Precambrian Research.

[7]  J. V. Grant,et al.  New constraints on the age of the opening of the South Atlantic basin , 2018, Marine and Petroleum Geology.

[8]  M. Schnabel,et al.  New constraints on the age and style of continental breakup in the South Atlantic from magnetic anomaly data , 2017 .

[9]  L. Borghi,et al.  The use of seismic attribute in 2D data: A case study , 2017 .

[10]  M. Rosa,et al.  High-Frequency Sequences in the Quaternary of Pelotas Basin (coastal plain): a record of degradational stacking as a function of longer-term base-level fall , 2017 .

[11]  W. Buck.  The role of magmatic loads and rift jumps in generating seaward dipping reflectors on volcanic rifted margins , 2017 .

[12]  Farid Chemale,et al.  Evolução tectônica do Cinturão Dom Feliciano no Sul do Brasil: relações geológicas e geocronologia U-Pb , 2016 .

[13]  J. Karson.  Crustal Accretion of Thick, Mafic Crust in Iceland: Implications for Volcanic Rifted Margins , 2016 .

[14]  L. Hartmann,et al.  Airborne geophysical characterization of geotectonic relationships in the southern Ribeira Belt, Luís Alves Craton, and northern Dom Feliciano Belt, Brazilian Shield , 2016 .

[15]  A. Gordon.  Seismic Volcano-Stratigraphy in the Basaltic Complexes of the Rifted Margin of Pelotas Basin, Southeast Brazil , 2015 .

[16]  G. Eagles,et al.  Getting over continent ocean boundaries , 2015 .

[17]  L. Geoffroy,et al.  Volcanic passive margins: another way to break up continents , 2015, Scientific Reports.

[18]  J. Dyment,et al.  The Cretaceous opening of the South Atlantic Ocean , 2015 .

[19]  M. Schnabel,et al.  The late rifting phase and continental break-up of the southern South Atlantic: the mode and timing of volcanic rifting and formation of earliest oceanic crust , 2014 .

[20]  R. Müller,et al.  Community infrastructure and repository for marine magnetic identifications , 2014 .

[21]  P. Zalán,et al.  The evolution of rifting on the volcanic margin of the Pelotas Basin and the contextualization of the Paraná–Etendeka LIP in the separation of Gondwana in the South Atlantic , 2014 .

[22]  T. Wright,et al.  Magma storage conditions beneath Dabbahu Volcano (Ethiopia) constrained by petrology, seismicity and satellite geodesy , 2012, Bulletin of Volcanology.

[23]  W. Mohriak,et al.  Phanerozoic regional geology of the eastern Brazilian margin , 2012 .

[24]  J. Cartwright,et al.  Conjugate margins of the South Atlantic: Namibia-Pelotas , 2012 .

[25]  D. Keir,et al.  The protracted development of the continent-ocean transition in Afar , 2011 .

[26]  A. Peyve.  Tectonics and magmatism in eastern South America and the Brazil basin of the Atlantic in the Phanerozoic , 2010 .

[27]  D. Aslanian,et al.  A new starting point for the South and Equatorial Atlantic Ocean , 2010 .

[28]  M. Gomes,et al.  REVISÃO DA EXTENSÃO AREAL E DO VOLUME DA FORMAÇÃO SERRA GERAL, BACIA DO PARANÁ, AMÉRICA DO SUL , 2009 .

[29]  Xiong Li.  Magnetic reduction-to-the-pole at low latitudes: Observations and considerations , 2008 .

[30]  L. Geoffroy.  Volcanic passive margins , 2005 .

[31]  J. Baker,et al.  Characteristics of volcanic rifted margins , 2002 .

[32]  V. Abreu,et al.  Inferences regarding initiation of oceanic crust formation from the U.S. East Coast margin and conjugate South Atlantic margins , 2013 .

[33]  C. Oppenheimer,et al.  Largest known historical eruption in Africa: Dubbi volcano, Eritrea, 1861 , 2000 .

[34]  C. Cainelli.  Some remarks on the evolution of sedimentary basins along the eastern Brazilian continental margin , 1999 .

[35]  S. Planke,et al.  Seismic volcanostratigraphy of the extrusive breakup complexes in the northeast Atlantic : Implications from ODP/DSDP drilling , 1999 .

[36]  O. Eldholm,et al.  South Atlantic volcanic margins , 1997, Journal of the Geological Society.

[37]  C. Hawkesworth,et al.  Chemical stratigraphy of the Paraná lavas (South America): classification of magma types and their spatial distribution , 1992 .

[38]  H. K. Chang,et al.  Tectonics and stratigraphy of the East Brazil Rift system: an overview , 1992 .

[39]  S. Jakobsdóttir,et al.  Distribution, crustal properties and significance of seawards-dipping sub-basement reflectors off E Greenland , 1988, Geological Society, London, Special Publications.

[40]  P. Stoffa,et al.  Origin of seaward-dipping reflectors in oceanic crust off the Norwegian margin by “subaerial sea-floor spreading” , 1982 .

[41]  P. Rabinowitz,et al.  The Mesozoic South Atlantic Ocean and evolution of its continental margins , 1979 .

[42]  Vladimir Baranov,et al.  Numerical calculation of the formula of reduction to the magnetic pole , 1964 .

[43]  C. Laj,et al.  Magnetic Anomalies Over Oceanic Ridges , 1963, Nature.

[44]  H. H. Hess.  The history of ocean basins , 1962 .

[45]  R. Dietz,et al.  Continent and Ocean Basin Evolution by Spreading of the Sea Floor , 1961, Nature.