Resumo

EGUILUZ Y DE ANTUNANO, Samuel  e  CHAVEZ, Gabriel. Lower Cretaceous synsedimentary extension at the edge of the Coahuila Block, a rift-like margin in Mexico. Bol. Soc. Geol. Mex [online]. 2022, vol.74, n.1, e130821.  Epub 02-Maio-2023. ISSN 1405-3322.  https://doi.org/10.18268/bsgm2022v74n1a130821.

This work presents data that identify a system of normal lystric domino faults, with synthetic and antithetical arrangements, at the edge of what is presumed to be a rift-type basin in northeastern Mexico. The outcrops are located within La Gavia and Arteaga anticlines, in the State of Coahuila and these localities are located paleogeographically on the eastern edge of the Coahuila Block. The structural analysis of these faults allows defining an extension vector σ3 perpendicular to the edge of the Coahuila Block, trending ~ 0 ° /191°-193 ° in La Gavia, and σ3 ~ 0 °/ 200° in Arteaga. Deformation in soft “non-lithified” sediments is also present in the succession. The structural analysis of the faults and the sedimentary structures in soft sediments suggest that these deformations were synchronous to basin infilling and co-genetics. This fault system is restricted to a specific stratigraphic level; thus, it is suggested that it has a contemporary development with the clastic sedimentation of the Arcosa Patula and the Carbonera Formation during the Lower Cretaceous. It is interpreted that the extension that generated these faults and soft sediment deformation can be attributed to different causes: 1) as a consequence of regional tectonic stress during extension in rift-type environments such as those generated by the Sabinas and Central Mexico basins; 2) a steep slope of the sedimentary wedge between the Coahuila Block and the basins during rejuvenation of the relief, or, 3) the combination of both mechanisms.

Palavras-chave : rift; sin-sedimentary faults; slump; Patula Arkose; Carbonera Formation.