Print this pageImportant constraints on the growth of a fold-thrust belt (FTB) include the shape and depth of basement beneath the deforming sedimentary wedge. Our first step in developing a three-dimensional model of the southern Appalachian FTB involved compiling all available industry, academic, and U.S./state geological survey well and seismic reflection data on basement elevation. We have combined our compilation of the basement surface in the southern Appalachians with Shumaker's 1996 map of the central Appalachians to develop a contour map of the basement surface for the Appalachian orogen from Alabama to New York. In the Tennessee embayment (GA to VA), the basement surface dips gently to the SE and contains several NE-striking down to the southeast normal faults related to Late Proterozoic-earliest Cambrian rifting events along the Laurentian margin. These basement structures likely influence structures in the FTB. Downdropped basement blocks may have permitted deposition of a thicker stratigraphic sequence. For instance, major thickness changes in the Cambrian rifted-margin deposits of the Rome Formation and Conasauga Group may be the stratigraphic expression of basement features. Normal faults in the basement may also localize detachment folds or ramps, limit thrust displacement, and influence the spacing of thrust faults in the FTB. Areas in which basement appears to affect FTB structure include the Valley and Ridge province in Alabama and Georgia and the Pine Mountain thrust sheet. In addition, fault spacing in the Appalachians increases towards the foreland, whereas in the Canadian Cordillera, fault spacing increases towards the hinterland.
AAPG Search and Discovery Article #90926©1999 AAPG Eastern Section Meeting, Indianapolis, Indiana