Controls on the seafloor exposure of detachment fault surfaces

• Published in: Earth and Planetary Science Letters
• Main Authors: Olive, Jean-Arthur, Parnell-Turner, Ross, Escartin, Javier, Smith, Deborah, Petersen, Sven
• Other Authors: Laboratoire de géologie de l'ENS (LGENS), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Département des Géosciences - ENS Paris, École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), Institut de Physique du Globe de Paris (IPGP), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Université de La Réunion (UR)-Institut de Physique du Globe de Paris (IPG Paris)-Centre National de la Recherche Scientifique (CNRS)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2019
• Subjects: [SDU.STU.TE]Sciences of the Universe [physics]/Earth Sciences/Tectonics; Mid-Atlantic Ridge; North Atlantic
• Online Access: https://hal.science/hal-02324084; https://hal.science/hal-02324084/document; https://hal.science/hal-02324084/file/Olive2019.pdf; https://doi.org/10.1016/j.epsl.2018.11.001

International audience Keywords 19 Mid-ocean ridge; detachment faulting; oceanic core complex; critical taper; fault friction; 20 21 Highlights 22 • A small fraction of corrugated detachment fault surfaces is eventually exposed at the seafloor. 23 • Seafloor slopes indicate effective friction of ~0.15 on shallow part of detachments. 24 • Moderate-offset detachment faults may be largely blanketed by hanging wall material. 25 • Seafloor-shaping processes profoundly alter the morphology of oceanic core complexes. 26 27 28 Abstract 29 While oceanic detachment faults have been proposed to account for the accretion of ~40% of new 30 seafloor in the North Atlantic ocean, clear exposures of large-offset, often-corrugated fault 31 surfaces remain scarce and spatially limited. To help resolve this paradox, we examine the 32 conditions under which detachment fault growth may or may not lead to extensive exposure of 33 corrugated fault planes at the seafloor. Using high-resolution bathymetry from four detachment 34 faults at the northern Mid-Atlantic Ridge, we investigate the rafting of hanging wall-derived debris 35 over emerging fault scarps, which can lead to covering shallow-dipping corrugated fault surfaces. 36 We model this process using critical taper theory, and infer low effective friction coefficients 37 (~0.15) on the shallowest portion of detachment faults. A corollary to this result is that detachments 38 emerging from the seafloor at angles <10º are more likely to become blanketed under an apron of 39 hanging wall material. We generalize these findings as a simple model for the progressive exposure 40 and flexural rotation of detachment footwalls, which accounts for the continued action of seafloor-41 shaping processes. Our model suggests that many moderate-offset, hidden detachment faults may 42 exist along slow mid-ocean ridges, and do not feature an exposed fault surface. 43 44