Paleomagnetic constraints on the forearc deformation history of the Costa Rican convergent margin

Author(s): Li Yongxiang; Zhao Xixi; Xie Siyi; Jovane, Luigi; Petronotis, Katerina E.
Author Affiliation(s): Primary:
Nanjing University, Nanjing, China
Tongji University, China
Instituto Oceanografico-USP, Brazil
Texas A&M University, International Ocean Discovery Program, United States
Volume Title: AGU 2017 fall meeting
Source: American Geophysical Union Fall Meeting, Vol.2017; American Geophysical Union 2017 fall meeting, New Orleans, LA, Dec. 11-15, 2017. Publisher: American Geophysical Union, Washington, DC, United States
Note: In English
Summary: We conducted a detailed paleomagnetic investigation of IODP Site U1380 located on the middle slope of the forearc wedge in order to examine the deformation history of the Costa Rican erosive convergent margin. Hole U1380C recovered a sedimentary section from 440 to 800 meters below seafloor (mbsf) consisting of, from bottom to top, silty claystone, clayey siltstone and sandstone, and silty clay. Anisotropy of magnetic susceptibility (AMS) data show predominantly oblate fabrics with the Kmin axes tilted off the vertical. Also, the degree of the Kmin tilt appears to generally track changes in bedding dip that was measured shipboard and thus can be used as a steepness proxy of tilted strata. An interval of strong deformation from ∼490 to ∼550 mbsf is indicated by the occurrence of abundant foliations that are shallower than the bedding. The interval of strong deformation is constrained from ∼1.95 to ∼1.83 Ma based on the detailed paleomagnetic investigation, together with biostratigraphic constraints. A comparative analysis of the deformation history from proximal middle slope Site U1378, frontal prism Site U1412, and upper slope Site U1379 reveals that a strongly deformed, wedge-shaped veneer of sediments formed between ∼2.0 and 1.9 Ma on the forearc. The short-lived, widespread, and strong forearc deformation in the Costa Rican margin is interpreted as the result of the abrupt onset of Cocos Ridge subduction. The results of this study provide supportive evidence for the "depositionary forearc" model for an erosive convergent margin.
Year of Publication: 2017
Research Program: IODP Integrated Ocean Drilling Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Basins; Central America; Costa Rica; Costa Rica Seismogenesis Project; East Pacific; Expedition 334; Fore-arc basins; IODP Site U1378; IODP Site U1380; Integrated Ocean Drilling Program; North Pacific; Northeast Pacific; Pacific Ocean; Paleomagnetism
Coordinates: N083600 N083600 W0840424 W0840424
Record ID: 2019060715
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