Continent-ocean boundary

Techniques used in identification

The following techniques are used either on their own or more commonly in combination.

Gravity data inversion

Moho depth can be derived by the inversion of satellite gravity data, taking into account the lithosphere thermal gravity anomaly. Crustal thickness can then be derived by subtracting this from the observed base of the drift (post break-up) sequence, normally from the interpretation of seismic reflection data.

Magnetic stripe data

Most areas of oceanic crust show characteristic stripes due to periodic magnetic reversals during formation at a mid-oceanic ridge. The continental crust is by contrast typically magnetically quiet. This method is dependent on stripes being present and will not work for oceanic crust created during the Cretaceous Quiet Zone. On some magma-rich margins stripes have also been identified within the transition zone.

Seismic reflection data

On normal incidence seismic reflection data recorded to sufficient depths, the Moho can in some areas be directly imaged, allowing the identification of normal thickness oceanic crust.

Wide-angle seismic refraction and reflection data

The combined use of seismic wide-angle reflection and refraction data give a precise location for the COB by determining the P-wave velocities along a profile. The two types of crust have distinct P-wave velocities.

Economic importance

As hydrocarbon exploration moves further offshore to look for the remaining potential on passive margins, understanding the location of the COB is critical to predicting possible hydrocarbon occurrence. This is both from the likely location of source and reservoir rocks and the need to model the thermal effects of break-up in basin modelling

References

References

1. (2008). "Integrated crustal thickness mapping and plate reconstructions for the high Arctic". Earth and Planetary Science Letters.
2. (2021). "Nature of the Cuvier Abyssal Plain crust, offshore NW Australia". Journal of the Geological Society.
3. (2015). "Getting over continent ocean boundaries". Earth-Science Reviews.
4. "Frontier Science and Exploration: The Atlantic – Arctic". [[Geological Survey of Norway.