40Ar/39Ar muscovite geochronology of Arperos Basin inversion in Southern Mexico: new insights into cretaceous shortening initiation in southernmost North America

During Cretaceous-Eocene time, North America was involved in a succession of shortening events that produced major orogenic belts. Previous work permitted the characterization of the kinematics and dynamics of some of these orogenic events along various transects. However, the timing of shortening is not well constrained everywhere. This has led to misinterpretation of the tectonic history of some sectors of the North American Pacific margin and to an incomplete understanding of the subduction dynamics. Mexico is one of those sectors in which the shortening history is not completely defined. We present structural and 40Ar/39Ar isotopic data from major shortening structures in southern Mexico, documenting two episodes of shortening: a first one at similar to 118-112 Ma, not considered in previous works, and a second one at similar to 104-90 Ma, which was previously interpreted as the record of shortening initiation. Integrated with previous data, our 40Ar/39Ar results indicate that, in Mexico, the shortening history was developed in two main stages: 1) a Late Aptian-Early Albian stage of localized shortening, during which the oceanic Arperos Basin was closed and the Guerrero terrane arc accreted to nuclear Mexico forming a similar to 80 km-wide suture belt, and 2) a latest Albian-Eocene stage, in which shortening was propagated from the North American trench to the plate interior, producing the development of a critically tapered wedge. Whether these two stages represent two superposed orogenic cycles or two steps within the same orogenic cycle remains to be established. In any case, the Late Aptian-Early Albian stage of deformation, which was not fully recognized in most previous works, is a key for our understanding of the causes that triggered shortening in southern North America after similar to 100 m.y. of extension associated with Pangea break-up [GRAPHICS] . During Cretaceous-Eocene time, North America was involved in a succession of shortening events that produced major orogenic belts. Previous work permitted the characterization of the kinematics and dynamics of some of these orogenic events along various transects. However, the timing of shortening is not well constrained everywhere. This has led to misinterpretation of the tectonic history of some sectors of the North American Pacific margin and to an incomplete understanding of the subduction dynamics. Mexico is one of those sectors in which the shortening history is not completely defined. We present structural and 40Ar/39Ar isotopic data from major shortening structures in southern Mexico, documenting two episodes of shortening: a first one at similar to 118-112 Ma, not considered in previous works, and a second one at similar to 104-90 Ma, which was previously interpreted as the record of shortening initiation. Integrated with previous data, our 40Ar/39Ar results indicate that, in Mexico, the shortening history was developed in two main stages: 1) a Late Aptian-Early Albian stage of localized shortening, during which the oceanic Arperos Basin was closed and the Guerrero terrane arc accreted to nuclear Mexico forming a similar to 80 km-wide suture belt, and 2) a latest Albian-Eocene stage, in which shortening was propagated from the North American trench to the plate interior, producing the development of a critically tapered wedge. Whether these two stages represent two superposed orogenic cycles or two steps within the same orogenic cycle remains to be established. In any case, the Late Aptian-Early Albian stage of deformation, which was not fully recognized in most previous works, is a key for our understanding of the causes that triggered shortening in southern North America after similar to 100 m.y. of extension associated with Pangea break-up [GRAPHICS] . During Cretaceous-Eocene time, North America was involved in a succession of shortening events that produced major orogenic belts. Previous work permitted the characterization of the kinematics and dynamics of some of these orogenic events along various transects. However, the timing of shortening is not well constrained everywhere. This has led to misinterpretation of the tectonic history of some sectors of the North American Pacific margin and to an incomplete understanding of the subduction dynamics. Mexico is one of those sectors in which the shortening history is not completely defined. We present structural and 40Ar/39Ar isotopic data from major shortening structures in southern Mexico, documenting two episodes of shortening: a first one at similar to 118-112 Ma, not considered in previous works, and a second one at similar to 104-90 Ma, which was previously interpreted as the record of shortening initiation. Integrated with previous data, our 40Ar/39Ar results indicate that, in Mexico, the shortening history was developed in two main stages: 1) a Late Aptian-Early Albian stage of localized shortening, during which the oceanic Arperos Basin was closed and the Guerrero terrane arc accreted to nuclear Mexico forming a similar to 80 km-wide suture belt, and 2) a latest Albian-Eocene stage, in which shortening was propagated from the North American trench to the plate interior, producing the development of a critically tapered wedge. Whether these two stages represent two superposed orogenic cycles or two steps within the same orogenic cycle remains to be established. In any case, the Late Aptian-Early Albian stage of deformation, which was not fully recognized in most previous works, is a key for our understanding of the causes that triggered shortening in southern North America after similar to 100 m.y. of extension associated with Pangea break-up [GRAPHICS] .

Automated summary

During the Cretaceous-Eocene period, North America experienced a series of shortening events that resulted in major orogenic belts. However, the timing of these events is not well constrained everywhere, leading to misinterpretation of tectonic history in some areas, particularly along the North American Pacific margin, and an incomplete understanding of subduction dynamics. This study focuses on southern Mexico and presents structural and isotopic data that reveal two episodes of shortening: one around 118-112 Ma and another around 104-90 Ma. These findings contribute to a better understanding of the shortening history in Mexico and highlight the importance of the Late Aptian-Early Albian stage of deformation.