Preheat oven to 350 F or 175 C.
Grease a 13 by 9 inch baking pan. Mix chocolate 1/3 cup sugar, cinnamon and blueberries set aside.
Mix flour, baking soda, baking powder and salt set aside
Beat margarine 1 1/3 cup sugar and vanilla in a large bowl with electric mixer on medium speed until light and fluffy. Add eggs one at a time, beating well after each addition and flour mixture alternatively with sour cream beating after every addition until smooth.
Spoon half of batter into prepared pan top with 1/2 of chocolate mixture repeat layers bake 40 to 45 minutes or until a toothpick inserted into center comes out clean.
Cool in pan on wire rack.