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Abstract <p>We aimed to determine whether the decoupling of the Nazca Plate convergence, the Carnegie Ridge subduction, and/or the Chocó-Panama Arc collision is (are) the leading process(es) exerting control over transpression and margin-parallel extrusion on a small (Ecuador-Colombia Forearc Sliver) and/or large (Northern Andes) scale in northwestern South America. The partitioning of the subduction slip was found to be, at most, only weakly effective. However, it has been successful in producing the detachment and extrusion of the Ecuador-Colombia Forearc Sliver. A linear decrease in GPS velocities from coastal sites provides corroboration for the existence of a buttress to the north, coinciding with the region of island arc indentation. The majority of transpression generated by partial decoupling is absorbed by the Romeral Megashear Zone, which is the internal boundary of the sliver, leaving only a minimal portion to deform the Central and Eastern cordilleras. Consequently, the rapid slip rates necessary to satisfy strain accumulation along the NE-, ENE-, and NW-trending strike–slip faults that cross the orogen are not attributable to slip partitioning at the subduction interface. Instead, the interpretation of the widespread transpression in the Northern Andes is contingent upon the consideration of accretionary orogenesis by the indentation of the Chocó-Panama Arc.</p> Research Highlights <p><UnorderedList Mark="Bullet"> <ItemContent> <p>The convergence obliquity is largely consumed during subduction, leaving only a small portion to produce the detachment and extrusion of the Ecuador-Colombia Forearc Sliver.</p> </ItemContent> <ItemContent> <p>The strong Nazca-South America interplate coupling inhibits the complete partitioning of the subduction slip, leading to the categorization of the degree of partitioning as weak to null.</p> </ItemContent> <ItemContent> <p>The Chocó-Panama Arc collision has been identified as the primary control that successfully explains the widespread transpression in the Northern Andes.</p> </ItemContent> </UnorderedList></p>

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An assessment of the tectonic controls of transpression and margin extrusion in northwestern South America

  • 期刊论文

  • 发表日期：

    2026年8月1日

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  • Sergio Adrián López Isaza,
  • Eduardo Antonio Rossello,
  • Julián Andrés López-Isaza

摘要

Abstract

We aimed to determine whether the decoupling of the Nazca Plate convergence, the Carnegie Ridge subduction, and/or the Chocó-Panama Arc collision is (are) the leading process(es) exerting control over transpression and margin-parallel extrusion on a small (Ecuador-Colombia Forearc Sliver) and/or large (Northern Andes) scale in northwestern South America. The partitioning of the subduction slip was found to be, at most, only weakly effective. However, it has been successful in producing the detachment and extrusion of the Ecuador-Colombia Forearc Sliver. A linear decrease in GPS velocities from coastal sites provides corroboration for the existence of a buttress to the north, coinciding with the region of island arc indentation. The majority of transpression generated by partial decoupling is absorbed by the Romeral Megashear Zone, which is the internal boundary of the sliver, leaving only a minimal portion to deform the Central and Eastern cordilleras. Consequently, the rapid slip rates necessary to satisfy strain accumulation along the NE-, ENE-, and NW-trending strike–slip faults that cross the orogen are not attributable to slip partitioning at the subduction interface. Instead, the interpretation of the widespread transpression in the Northern Andes is contingent upon the consideration of accretionary orogenesis by the indentation of the Chocó-Panama Arc.

Research Highlights

The convergence obliquity is largely consumed during subduction, leaving only a small portion to produce the detachment and extrusion of the Ecuador-Colombia Forearc Sliver.

The strong Nazca-South America interplate coupling inhibits the complete partitioning of the subduction slip, leading to the categorization of the degree of partitioning as weak to null.

The Chocó-Panama Arc collision has been identified as the primary control that successfully explains the widespread transpression in the Northern Andes.