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Continent-Ocean Transition or Boundary? Crowd-sourced seismic interpretations of the East-India Passive Margin
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  • Clare Elizabeth Bond,
  • Juan Alcalde,
  • Robert W. H. Butler,
  • Ken G McDermott,
  • Ramon Carbonell
Clare Elizabeth Bond
University of Aberdeen
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Juan Alcalde
Geosciences Barcelona, GEO3BCN-CSIC

Corresponding Author:jalcalde@geo3bcn.csic.es

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Robert W. H. Butler
University of Aberdeen
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Ken G McDermott
Shell Global Solutions (UK) Ltd.
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Ramon Carbonell
Geosciences Barcelona (Geo3BCN-CSIC)
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On the edge of our continents, oceanic crust meets continental crust. At passive margins, those where there is no active tectonics, subduction or transform faulting, these crustal types are connected as sharp continent-ocean boundaries (COB) or as diffuse continent-ocean transition (COT) zones. Passive margins are hard to explore and consequently relatively little is known about their morphology or the processes of their formation. Here we elicit and analyse seismic image interpretations of the passive margin offshore East India conducted by 17 groups of geoscientists to better understand the differences, or lack therein, of COB or COT interpretations of the margin. The group interpretations provide a wide range of margin models, five of which are abrupt COB based and 11 which are diffuse COT based. However, interpretations within the COB set vary in the placement of the boundary line between continental and oceanic crust, the boundary placement lying within the range of interpreted COT zones, with the average COB location falling in the centre of the interpreted COT zones. These crowd-sourced results are then compared with ten published interpretations across the margin, which show COB and COT zones falling in the same area. These findings raise questions as to the real differences in COB and COT models and the geological processes involved in their formation. Considering this, we discuss the implications for passive margin models and the use of Wisdom of Crowds-type approaches in reflecting on both the range of interpretation-based models and in the value of determining ‘average’ model approaches.