The Costa Rican convergent margin is a typical erosive margin where a low-angle subduction of the Cocos Ridge (CR) beneath the Caribbean Plate takes place and subduction erosion of the basal and forearc area in the overlying plate occurs. Because subduction erosion is destructive to rock records, subduction erosion processes can only be understood by indirect means such as investigating the deformation of the forearc sediments of the overlying plate. To explore the deformation characteristics and their relationships to subduction erosion process, we conducted paleomagnetic and sedimentologic investigations on sedimentary strata of Site U1413, recovered by the International Ocean Discovery Program (IODP) Expedition 344 in the upper slope of the forearc area of the Costa Rican convergent margin. The magnetic fabric results show that the degree of offset of the K_min axis from the vertical, as measured by the “90°-K_min”, increases with depth in the strata below ~380 mbsf (meters below seafloor), indicating a deformation zone below ~380 mbsf. The age of the uppermost deformation zone of Site U1413 is similar to those at the upper slope Site U1379 and the middle slope Site U1380, suggesting that widespread deformation occurred in the forearc area since ~1.8 Ma as a result of the near-flat subduction of the CR. In addition, from the middle slope to the upper slope, the dip angle of the strata in the deformation zone decreases, suggesting that the degree of deformation decreases progressively landward. Furthermore, the sudden changes in depositional environments recorded in different sites spanning ~2.0 Ma to ~1.9 Ma, likely indicate small-scale rapid uplift and subsidence in the forearc in response to seamount subduction in the context of km-scale uplift and subsequent subsidence associated with the initiation of the CR subduction at ~2.0 Ma.

哥斯达黎加会聚边缘是典型的侵蚀边缘，加勒比板块下方的科科斯海岭（CR）发生低角度俯冲，上覆板块基底和弧前区发生俯冲侵蚀。由于俯冲侵蚀对岩石记录具有破坏性，俯冲侵蚀过程只能通过调查上覆板块弧前沉积物变形等间接手段来理解。为了探索变形特征及其与俯冲侵蚀过程的关系，我们对由国际海洋发现计划 (IODP) 344 号远征队在哥斯达黎加弧前区上坡回收的 U1413 站点的沉积地层进行了古地磁和沉积学调查。收敛边缘。从垂直方向的_最小轴，通过“90°-K _min”，随着低于~380 mbsf（海底以下米）的地层深度而增加，表明变形区低于~380 mbsf。U1413 最上部变形带年龄与上斜坡 U1379 和中斜坡 U1380 相似，表明弧前区自~1.8 Ma 以来发生了广泛的变形CR。此外，从中斜坡到上斜坡，变形带地层的倾角逐渐减小，表明变形程度逐渐向陆地减小。此外，在不同地点记录的沉积环境的突然变化跨越~2.0 Ma 到~1.9 Ma，