The Dynamic History of 220 Million Years of Subduction Below Mexico: A Correlation Between Slab Geometry and Overriding Plate Deformation Based on Geology, Paleomagnetism, and Seismic Tomography

Abstract

Global tectonic reconstructions of pre‐Cenozoic plate motions rely primarily on paleomagnetic and geological data from the continents, and uncertainties increase significantly with deepening geological time. In attempting to improve such deep‐time plate kinematic reconstructions, restoring lost oceanic plates through the use of geological and seismic tomographical evidence for past subduction is key. The North American Cordillera holds a record of subduction of oceanic plates that composed the northeastern Panthalassa Ocean, the large oceanic realm surrounding Pangea in Mesozoic times. Here we present new paleomagnetic data from subduction‐related rock assemblages of the Vizcaíno Peninsula of Baja California, Mexico, which yield a paleolatitudinal plate motion history equal to that of the North American continent since Late Triassic time. This indicates that the basement rocks of the Vizcaíno Peninsula formed in the forearc of the North American Plate, adjacent to long‐lived eastward dipping subduction at the southern part of the western North American continental margin. Tomographic images confirm long‐lived, uninterrupted eastward subduction. We correlate episodes of overriding plate shortening and extension to flat and steep segments of the imaged slab. By integrating paleomagnetic, geological, and tomographic evidence, we provide a first‐order model that reconciles absolute North American plate motion and the deformation history of Mexico since Late Triassic time with modern slab structure.

Control of Subduction Zone Age and Size on Flat Slab Subduction

“…Another requirement is for slabs to be continuous from the surface down to the lower mantle, which is the case for a number of slabs in nature that include flat slab segments, as implied by mantle tomography studies. In particular, several tomography studies indicate that part of the Nazca slab subducting below South America continues down to ∼2400 km (e.g., van der Meer et al, 2018), and that part of the Cocos slab subducting along the Mexico-Central America subduction zone continues down to ∼2600-2800 km (e.g., Boschman et al, 2018).…”

“…Flat slab subduction occurs in the Eastern Pacific in Peru, Central Chile, and Mexico and the proposed flat slab mechanism, involving a wide subduction zone (≥∼6000 km) and prolonged (>∼80-110 Myr) subduction, applies to these examples (Figure 2). Indeed, they formed at the Farallon/South American subduction zone at a time when it had been active for a long period (since the Middle Triassic-Early Jurassic) (Burchfiel and Davis, 1975;Coira et al, 1982;Boschman et al, 2018) and when it was extremely wide (7000-13,000 km). The Altiplano flat slab that formed in the central Andes at ∼35 Ma and terminated at ∼25 Ma (Ramos and Folguera, 2009) can also be explained in this manner.…”

Subduction Duration and Slab Dip

“…Based on the combination of age dating of volcanic rocks, structural evolution and seismic evidence, the reinitiation of subduction has been dated at 50 Ma (Schmandt & Humphreys, ) with a 53–48 Ma range based on U‐Pb ages of basalt eruptions (Wells et al, ). Through an interpretation of seismic tomography, along with paleomagnetism and other geological indicators, Boschman et al () assign a 220 Myr duration for subduction in Mexico. We assign this age to SW and SE Mexico, considerably longer than the 90 ±3 Ma age assigned by Jarrard () and shorter than the 255 Ma geologically based age for North America.…”

The Caribbean and Farallon Plates Connected: Constraints From Stratigraphy and Paleomagnetism of the Nicoya Peninsula, Costa Rica

“…Except for the Juan de Fuca, Rivera, Cocos, and Nazca plates, which are presumed present‐day remnants of the Farallon Plate, the absence of anomalies conjugate to the Jurassic‐early Cenozoic anomalies of the Pacific Plate indicates that the vast majority of the Farallon Plate has been lost to subduction. Reconstruction of the kinematic history of the Farallon Plate therefore relies on indirect evidence such as the spreading history of the Pacific Plate (Engebretson et al, ; Wright et al, ), geological and paleomagnetic records of the highly deformed continental margins of North and South America (Boschman, Garza, et al, ; Boschman, van Hinsbergen, et al, ; Johnston, ; Nokleberg, ; Tarduno et al, ; Tarduno & Alvarez, ), and interpretation of seismic tomography models that image subducted Farallon lithosphere (Boschman, van Hinsbergen, et al, ; Grand et al, ; Liu et al, ; Liu & Stegman, ; Sigloch & Mihalynuk, ; van der Meer et al, , , ).…”