Evolution of Caribbean subduction from P-wave tomography and plate reconstruction
- 1Imperial College, Department of Earth Sciences and Engineering, London, United Kingdom of Great Britain and Northern Ireland (r.allen16@imperial.ac.uk)
- 2Geophysical Institute, Karlsruhe Institute of Technology, Germany
- *A full list of authors appears at the end of the abstract
The Caribbean plate has a complex tectonic history, which makes it particularly challenging to establish the evolution of the subduction zones at its margins. Here we present a new teleseismic P-wave tomographic model under the Antillean arc that benefits from ocean-bottom seismometer data collected in our recent VoiLA (Volatile Recycling in the Lesser Antilles) project. We combine this imagery with a new plate reconstruction that we use to predict possible slab positions in the mantle today. We find that upper mantle anomalies below the eastern Caribbean correspond to a stack of material that was subducted at different trenches at different times, but ended up in a similar part of the mantle due to the large northwestward motion of the Americas. This stack comprises: in the mantle transition zone, slab fragments that were subducted between 70 and 55 Ma below the Cuban and Aves segments of the Greater Arc of the Caribbean; at 450-250 km depth, material subducted between 55 and 35 Ma below the older Lesser Antilles (including the Limestone Caribees and Virgin Islands); and above 250 km, slab from subduction between 30 and 0 Ma below the present Lesser Antilles to Hispaniola Arc. Subdued high velocity anomalies in the slab above 200 km depth coincide with where the boundary between the equatorial Atlantic and proto-Caribbean subducted, rather than as previously proposed, with the North-South American plate boundary. The different phases of subduction can be linked to changes in the age, and hence buoyancy structure, of the subducting plate.
Rob Allen(1), Benedikt Braszus(2), Saskia Goes(1), Andreas Rietbrock(2), Jenny Collier(1), Nick Harmon(3), Tim Henstock(3), Stephen Hicks(1), Kate Rychert(3), Ben Maunder(1), Jeroen van Hunen(4), Lidong Bie(2), Jon Blundy(5), George Cooper(5), Jon Davidson(8), Richard Davy(1), Mike Kendall(5), Colin Macpherson(4), Julie Prytulak(4), Jamie Wilkinson(6), and Marjorie Wilson(7)
How to cite: Allen, R., Braszus, B., Goes, S., Rietbrock, A., and Collier, J. and the The VoiLA Team: Evolution of Caribbean subduction from P-wave tomography and plate reconstruction, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9018, https://doi.org/10.5194/egusphere-egu2020-9018, 2020
Comments on the display
AC: Author Comment | CC: Community Comment | Report abuse
Hi Rob, very nice overview of the evolution of the Caribbean! I noticed you mention a lateral tear below Grenada; could you point me to the tomography figure where I could recognize that (I am not an expert at reading those)? Also, do you think this tear is the reason for the shallower slab geometry in the southern part of the LAA (0-200 km depth), as shown by both the Slab2 model and Bie et al. (2020)? I wonder what the impact of such a lateral tear is on the seismogenic behavior of the subduction interface.
Hi Eleonora,
Sorry, could not fit a vertical cross section which best shows that into the poster, but it is visible by comparing the horizontal slice in Fig 3 b (depth of the tear) and those in 3a and 3c (above and below the tear).
Yes, could be that this tear facilitates the smaller dip of the southern part of the Antilles slab.
How it affect seismogenesis is hard to say. It may play a role in the smaller number of Benioff earthquakes in the south than north (warmer slab in the south than north), but then again different dip angles also already lead to smaller sinking velocities in the south and hence higher slab temperatures at the same depth in south compared to north. For interplate earthquakes, your models may be better placed to provide some answers
Saskia
Hi Elenora,
So I think Saskia has covered most of your questions. If you aren't too comfortable with the tomography, essentially we would expect the slab to be fast (blue). In the 160-240 km slice you can see that the southern end of the arc, where we predict the location of the slab is distinctly slow (orange), suggesting that there is mantle where we would expect the slab to be. Hence we interpret this as a slab tear beneath the southern end of the arc.
Cheers,
Robert
Thanks Saskia and Robert for your clarifications! And yes, I understand that your study does not focus on the seismogenesis; I was simply thinking out loud. It might be something to keep in mind when we compare the seismogenic behaviour of the north and the south of the margin. Thanks again!