Preheat oven to 325°. Place a greased 9-in. springform pan on a double thickness of heavy-duty foil (about 18 in. square). Wrap foil securely around pan., Place pecans and brown sugar in a food processor; pulse until fine crumbs form. Add butter; pulse to combine. Press onto the bottom of prepared pan. Place pan on a baking sheet. Bake until light brown, 15-20 minutes. Cool on a wire rack., In a large bowl, beat cream cheese and 3/4 cup brown sugar until smooth. Beat in sour cream and vanilla. Add eggs; beat on low speed just until blended., In another bowl, mix pumpkin, spices and remaining brown sugar. Stir in 1-1/2 cups of the cream cheese mixture., To layer, pour 1-1/2 cups plain cream cheese mixture over crust. Gently spread 1-1/3 cups pumpkin mixture over top. Repeat layers. Cut through layers with a knife to swirl. Place springform pan in a large baking pan; add 1 in. of very hot water to larger pan., Bake until center is just set and top appears dull, 70-80 minutes. Remove springform pan from water bath. Cool cheesecake on a wire rack 10 minutes. Loosen sides from pan with a knife; remove foil. Cool 1 hour longer. Refrigerate overnight. Remove rim from pan.