Mix gingersnaps and butter in small bowl and mix well. Press over bottom of 9 inch springform pan. Bake at 350 for 10 minutes. Cool on a wire rack. Spread ice cream evenly over cooled crust and freeze til firm. Sprinkle evenly with pecans.
Mix pumpkin, sugar, cinnamon and nutmeg in medium pan. Mix well. Bring to boil over medium high heat, stirring constantly. Remove from heat and allow to cool completely. Fold whipped cream into cooled pumpkin mixture. Pour into prepared pan and freeze til firm. Remove to the refrigerator 2 hours before serving time. Loosen and remove side of pan to serve. Serve 8 to 10