Publication Date:
2021-07-21
Description:
Continental microplates are enigmatic plate boundary features, which can occur in extensional and compressional regimes. Here we focus on microplate formation and their temporal evolution in continental rift settings. To this aim, we employ the geodynamic finite element software ASPECT to conduct 3D lithospheric‐scale numerical models from rift inception to continental breakup. We find that depending on the strike‐perpendicular offset and crustal strength, rift segments connect or interact through one of four regimes: (1) an oblique rift, (2) a transform fault, (3) a rotating continental microplate or (4) a rift jump. We highlight that rotating microplates form at offsets 〉200 km in weak to moderately strong crustal setups. We describe the dynamics of microplate evolution from initial rift propagation, to segment overlap, vertical‐axis rotation, and eventually continental breakup. These models may explain microplate size and kinematics of the Flemish Cap, the Sao Paulo Plateau, and other continental microplates that formed during continental rifting worldwide.
Description:
Plain Language Summary:
Microplates are enigmatic features that form in the boundaries between tectonic plates. In continental rifts, plates are successively broken to eventually form new oceans. As the continental crust is very heterogeneous, rifts rarely form in straight lines. In some cases, individual rift segments initiate hundreds of kilometers apart both along and perpendicular to strike and as these segments grow, they interact and link. Here we use 3D computer simulations to investigate the linkage of offset rifts. We find that rift linkage is primarily controlled by the strike‐perpendicular offset and crustal strength. At low offset they link through an oblique rift segment, at medium offset a transform fault is formed, and at large offsets in weak crust they overlap and rotate a central block known as a microplate. We suggest that the latter processes have shaped the Flemish Cap, the Sao Paulo Plateau, and many other continental promontories at rifted margins worldwide.
Description:
Key Points:
Strike‐perpendicular offset and crustal strength control the mode of rift segment linkage (microplate, oblique, or transform)
Rotating continental microplates form at offsets of 〉200 km for weak and moderately strong crust
Modeled microplate evolution may explain the formation of the Flemish Cap, the Sao Paulo Plateau, and other continental promontories
Description:
Helmholtz Young Investigator Group CRYSTALS
Keywords:
551.136
;
Flemish Cap
;
Sao Paulo Plateau
;
microplate formation
;
numerical modeling
Type:
article
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