Geometry and kinematics of compressional growth structures and diapirs in the La Popa basin of northeast Mexico: Insights from sequential restoration of a regional cross section and three‐dimensional analysis

Abstract

Diapirism in the La Popa basin NE Mexico was triggered and sustained by compressional décollement tectonics. Coeval development of contractional structures and diapirs was recorded by growth strata of Late Cretaceous‐Tertiary age. A palinspastic reconstruction of a regional cross section, based on the restoration of growth strata related to both diapirs and detachment folds, was carried out. On the basis of this reconstruction and field data, a three‐dimensional geometrical study was done to quantify the movement of evaporites within the detachment horizon and two diapirs. The latter allowed determining the tectonodiapiric potential of a structure or set of structures (i.e., the amount of ductile rocks forced to flow in association with the growth of a tectonic structure, which is not accommodated by thickening of the ductile horizon nor by the tectonic structure itself, and is capable of producing diapiric phenomena). This study demonstrates that there is a direct coupling between tectonodiapiric potential and diapiric activity. Geometrical results show that the main factors that controlled the amount of ductile material moved as a consequence of compressional tectonics were shortening, the depth to detachment, the folding style, and the style of deformation process (i.e., pure shear/simple shear). In response to folding, the overburden experienced a downward movement that was the major cause of diapiric phenomena. In addition to field and geometrical data, mechanical data indicate that forceful intrusion was the prevailing emplacement mechanism. Temperatures (>150°–197°C) and strain rates (in the order of 10−16–10−17 s−1) calculated for top of the evaporite layer were adequate for the flow of these rocks from the initiation of compression onward. However, an inferred overpressure in the ductile layer should be considered the key factor for the emplacement mechanism.