Paleomagnetism of IODP Site U1380: Implications for the Forearc Deformation in the Costa Rican Erosive Convergent Margin

Yong-Xiang Li,Katerina Petronotis,Siyi Xie,Xixi Zhao,Luigi Jovane

doi:10.1038/s41598-018-29243-7

Yong-Xiang Li, Katerina Petronotis + Show 3 more

Open Access

https://doi.org/10.1038/s41598-018-29243-7

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Abstract

The destructive nature of subduction erosion poses challenges to fully understanding the evolution of erosive convergent margins that are critical to understanding crustal recycling and seismogenesis. Forearc deformation holds important clues to the evolution of erosive convergent margins. Here we present detailed paleomagnetic and structural analyses of IODP Site U1380 cores from the middle slope of the forearc of the Costa Rican erosive convergent margin. The analyses reveal a strong deformation zone from ~490 to ~550 mbsf that is characterized by abundant fissility/foliations shallower than the bedding. Similar relatively strong deformation zones are recognized from the frontal prism and upper slope sites, and are broadly correlative, forming a zone of strong deformation across the forearc. This zone spans ~2.0 to 1.83 Ma and the deformation likely occurred briefly at ~1.80 Ma. The widespread, short-lived, and strong deformation is interpreted as a result of intense subhorizontal shear following the rapid forearc subsidence driven by the dramatic subduction erosion associated with the abrupt onset of the Cocos Ridge subduction. Given the typical occurrence of forearc subsidence by subduction erosion, similar styles of deformation are probably common in other erosive convergent margins as well.

Highlights

The southern segment of the Costa Rican margin is drastically different from the northern counterpart
Sediments in the upper slope appear to exhibit different styles of deformation before and after the deposition of the nearshore facies[32], it is not clear whether the difference in deformation style is pervasive in the forearc largely because the structural architecture in the forearc has generally not been examined in detail
We examine the deformation style and history at the middle slope Site U1380 in the southern segment of the Costa Rican margin

Summary

Introduction

The southern segment of the Costa Rican margin is drastically different from the northern counterpart. Integrated Ocean Drilling Program (IODP) Expeditions 334 and 344 cored the frontal prism (Site U1412), and the subducting CR (Sites U1381 and U1414) and middle slope (Sites U1378 and U1380), and the upper slope (Sites U1379 and U1413) offshore southern Costa Rica (near Osa Peninsula)[8,29] (Fig. 1b, BGR99-Line7), providing a unique opportunity to examine the forearc deformation history. We examine the deformation style and history at the middle slope Site U1380 in the southern segment of the Costa Rican margin. A comparative analysis of the deformation in the middle slope, the frontal prism, and the upper slope allows an improved understanding of the forearc deformation of the Costa Rican erosive convergent margin

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