In a small bowl, combine cookie crumbs and butter. Press into the bottom of a greased 9-inch spring form pan. Place pan on a baking sheet. Bake at 325 F. for 10-15 minutes or until set. Cool on a wire rack.
In a large mixing bowl, beat the cream cheese, sugar and 2 T. cornstarch until smooth. Beat in the sour cream, vanilla and salt. Add eggs; beat on low speed just until combine.
Remove 3 1/2 cups of filling to a bowl; stir lemon juice into it and set aside.
Add the pumpkin, brown sugar, molasses, spices and remaining cornstarch to the remaining filling; remove 1/2 cup of mixture and set aside.
Pour half of the remaining pumpkin filling over gingersnap crust; top with half of the plain filling. Repeat layers. Dot with spoonfuls of the reserved 1/2 cup of pumpkin filling. Cut through the filling with a knife to swirl.
Place pan on a double thickness of heavy-duty foil; securely wrap foil around the pan. Place spring form pan into a larger baking pan. Add 1 inch of hot water to larger pan. Bake at 325 F. for 1 hour and 10 minutes or until center is almost set.
Remove spring form pan from water bath. Cool on a wire rack for 10 minutes. Carefully run a knife around edge of pan to loosen; cool 1 hour longer. Remove foil. Refrigerate overnight. Remove sides of pan when ready to serve.