Cross Section Balancing in the Central Apennines: An Application of locace (1)

Abstract

LOCACE (LOgiciel de Construction Assistee de Coupes Equilibrees), a recently developed computer program for balancing geological cross sections, has been used here on the geology of the central Apennines. Although initially conceived to help explorationists improve seismic interpretations involving no more than two or three fault-bounded tectonic units or modules, LOCACE is also expected to address regional problems involving complete geologic sections with numerous and complex structures. Our study area is a cross section across the complex thrust belt and foreland basin of the central Apennines. Because surface mapping and subsurface data (conventional seismic profiles with well control) do not provide adequate deep constraints on the amount of basement involvement and details of basement fault configuration, we present two alternative balanced cross sections. In contrast to previous interpretations with only thin-skinned deformation, both of our hypotheses involve basement thrusting. One involves a piggyback thrusting sequence; the other involves later emplacement of an out-of-sequence basement thrust. Our study demonstrates the ability of LOCACE to restore structurally complex cross sections. It also demonstrates that more than one distinct balanced solution can be derived from the same observed near-surface geometry, and that additional investigations (such as deep seismic profiling) are required to help resolve the problems at depth.