ON DEGENERATE SECANT VARIETIES OF SECANT DEFECT-2

We study projective manifolds with degenerate secant varieties under a ssumptions that the secant defect is two and that the Gauss maps of se cant varieties have the largest images. In particular we classify 7-di mensional projective manifolds with 13-dimensional degenerate secant v arieties whose Gauss maps have 10-dimensional images. We also determin e Del Pezzo fibrations over curves with smallest embedded codimension in the case that the degree of a general fiber is three or four.