  In this paper, we propose a connection between the field theory local model
(Katz-Vafa field theory) and the type of singular fibre in flat crepant
resolutions of elliptic Calabi-Yau fourfolds, a class of fourfolds considered
by Esole and Yau. We review the analysis of degenerate fibres for models with
gauge groups SU(5) and SO(10) in detail, and observe that the naively expected
fibre type is realized if and only if the Higgs vev in the field theory local
model is unramified. To test this idea, we implement a linear (unramified)
Higgs vev for the `E6' Yukawa point in a model with gauge group SU(5) and
verify that this indeed leads to a fibre of Kodaira type IV*. Based on this
observation, we argue i) that the singular fibre types appearing in the
fourfolds studied by Esole-Yau are not puzzling at all, (so that this class of
fourfolds does not have to be excluded from the candidate of input data of some
yet-unknown formulation of F-theory) and ii) that such fourfold geometries also
contain more information than just the eigenvalues of the Higgs field vev
configuration in the field theory local models.
