By marginally trapped surface I mean a spacelike surface in a 4-dimensional Lorentzian manifold such that the mean curvature vector is lightlike.

In my research I have stumbled across marginally trapped surfaces with Gaussian curvature equal to 1 in De Sitter's space. I have searched in vain for references about such surfaces. Does anyone know anything about them and if they could be interesting for General Relativity? I also have stumbled across spacelike surfaces with flat normal bundle in De Sitter space with constant Gaussian equal to 1, same question... Thank you in advance for any information.