In this paper, the singularity structure in moduli spaces of G-Higgs bundles arising from degenerations of Riemann surfaces to nodal curves is examined. Specifically, for a complex reductive Lie group G and a standard degeneration \(\pi : {\mathcal {X}} \rightarrow \Delta \) with central fiber \(X_0 = Y_1 \cup Y_2\) , we prove the existence of a flat family of schemes \(\mathcal {M}_G \rightarrow \Delta \) whose general fiber is the moduli space of semistable G-Higgs bundles. The central fiber \(\mathcal {M}_G(0)\) admits a stratification indexed by conjugacy classes of parabolic subgroups \(P \subset G\) , where each stratum \(\mathcal {M}_G^P(0)\) is isomorphic to \(\mathcal {M}_L(Y_1, p) \times _{H^0(p, \mathfrak {l}/\mathfrak {z})} \mathcal {M}_L(Y_2, p)\) for the Levi factor L of P. We demonstrate that the formal neighborhood of a stable point in \(\mathcal {M}_G^P(0)\) is analytically equivalent to the cone on \(G/P \times G/P^{\textrm{op}}\) with its Plücker embedding, and construct a canonical resolution \(\tilde{\mathcal {M}}_G(0) \rightarrow \mathcal {M}_G(0)\) whose exceptional locus over \(\mathcal {M}_G^P(0)\) is a \(\mathbb {P}^{\dim (G/P)-1}\) -bundle. Furthermore, we establish that \(\mathcal {M}_G(0)\) carries a natural Poisson structure whose symplectic leaves are precisely the strata \(\mathcal {M}_G^P(0)\) . Finally, as an application, we derive explicit formulas for Gromov-Witten invariants of associated symplectic fibrations in terms of relative invariants on \(Y_1\) and \(Y_2.\)
