Structural interpretation of a seismic section in the Arcabuz–Culebra area, Cuenca de Burgos, NE Mexico

Abstract

The seismically imaged subsurface stratigraphy of the Arcabuz–Culebra area in the Burgos Basin (Nuevo León State, northeast Mexico) consists of a probably metamorphic basement of late Paleozoic age unconformably overlain by a sequence of sedimentary rocks which spans from the Middle Jurassic (?) to the early Oligocene. This stratigraphic sequence can be subdivided into two packages with different structural behavior that define a detached extensional deformation. The lower sequence appears undeformed, and includes the basement as well as the mesozoic marine strata which dip shallowly to the east. The upper sequence includes the paleogene units and is deformed by a series of eastward dipping normal faults with listric geometry, which sole out at the Mesozoic–Paleogene boundary. The upper sequence also exhibits shale diapir structures. Two structurally distinct domains can be identified within the detached upper plate: the deformation within the western domain is dominated by listric faulting defining a detached normal fault style, while in the eastern domain, shale mobility or flow appears to be the dominant deformation mechanism defining a shale structure style. The truncation of fault systems by paraconformities constrains their age to the Eocene. In detail, the first deformational phase, of early Eocene age, is post-depositional, while the latter two phases in middle Eocene and late Eocene–early Oligocene time, respectively, correspond to syn-sedimentary events. These last two pulses are also spatially and temporally associated with three periods or stages of shale mobility: a middle Eocene reactive stage, a late middle Eocene active stage and a new late Eocene–early Oligocene reactive stage. Toward the middle of the seismic section, the intersection of the two structural styles corresponds with the development of an important depocenter, in which important thicknesses of Queen City, Weches, and Cook Mountain strata accumulated.