New constraints on timing of Hidalgoan (Laramide) deformation in the Parras and La Popa basins, NE Mexico

Resumen

The Parras and La Popa
basins of northeastern Mexico together contain at least three
separate types of structures that were active during Maastrichtian
through Early Eocene time. These structures include salt diapirs and
salt welds, E-W trending anticlines detached within the Campanian
Parras shale, and large NW-SE trending anticlines detached within
the Jurassic salt layers. The oldest halokinetic structure, the La
Popa salt weld, began to form by Late Aptian time. This structure is
parallel to the later NW-SE contractional folds, but it pre-dates
regional contraction. The earliest dated contractional structures in
the Sierra Madre Oriental are E-W trending folds and faults found
east of the La Popa syncline. These structures were active only
briefly during the deposition of the lower Maastrichtian Muerto
Formation. Very similar east-west structures in the northern Parras
Basin contain growth strata of upper Maastrichtian and Paleocene
age. Folding of upper Paleocene beds indicates that this shortening
continued into the Eocene. Very Large amplitude NWSE trending
anticlines in La Popa Basin also formed due to regional contraction,
and they clearly re-fold the shallow-detached E-W set. Regional
evidence suggests that all contractional deformation ceased around
40 Ma. Salt withdrawal may have continued after the cessation of
contractional deformation. The contractional deformation in these
basins is similar in structural style to the Sevier orogen in the U.
S. A., but it is later and of shorter duration than the Sevier
orogeny; it is time-equivalent to the Laramide orogeny, but it
differs significantly from the Laramide structural style. Thus, the
Mexican orogenic system differs from the U. S. A. orogens. This
uniqueness was recognized by Guzmán and De Cserna (1963) who named
this deformational event in Mexico the Hidalgoan orogeny.