Preheat oven to 350°.

Stir together crushed cookies, pecans, and butter in a bowl. Press into bottom and 1"up sides of a 9" springform pan. Bake 10 minutes.

Meanwhile, beat together cream cheese, 1/2C sugar, and vanilla in a bowl with mixer, until smooth. Beat in the eggs, one at a time, blending well. Reserve 1C batter. Then beat in the remaining 1/4C sugar, the pumpkin, cinnamon and nutmeg into remaining batter.

Spread pumpkin batter into crust. Drop reserved 1C plain batter by spoonfuls onto top. Swirl with a knife to make a marbled effect.

Bake for 45-55 minutes, until only the center is jiggly. Let cool on a wire rack for 15 minutes. Run a knife around the edge to loosen; let cool 2 hours or more before removing pan rim. Chill at least 4 hours. Garnish with whipped cream and nuts if desired.