Seismic interpretation and structural analysis of the Alleghanian fold-thrust belt in Central Alabama
In the central part of the Alleghanian fold-thrust belt of Alabama, multi-channel seismic and well log data are used to analyze structural elements of the thrust belt. Six horizons were interpreted on the seismic data in two-way travel time and were depth-converted using interval velocities derived from a synthetic seismogram as well as from sonic logs from USS-29-01-09 and COGC-USX #1. The structural interpretation from the depth-converted data shows the thrust belt is a forward-propagating thrust sequence with four main thrust faults branching off of a basal detachment. Basement along the profile is at a minimum depth of 4,700 m in the Black Warrior Basin and a maximum depth of 7,200 m in the Birmingham Graben System, yielding 2,500 m of relief in this Precambrian rift system. The coherent reflectors in this cross-section show no evidence for a ductile duplex; thus, the section was balanced using line length balancing techniques. The balanced cross-section yields a minimum of 30 km or 24% shortening. This value is similar to other balanced cross-sections to the north and south that span the Alleghanian fold-thrust belt in Alabama.