Continent-Ocean Transition or Boundary? Crowd-sourced seismic
interpretations of the East-India Passive Margin
Abstract
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.