Cardiff University | Prifysgol Caerdydd ORCA
Online Research @ Cardiff 
WelshClear Cookie - decide language by browser settings

Footwall rotation in an oceanic core complex quantified using reoriented Integrated Ocean Drilling Program core samples

Morris, A., Gee, J. S., Pressling, N., John, B. E., MacLeod, Christopher John, Grimes, C. B. and Searle, R. C. 2009. Footwall rotation in an oceanic core complex quantified using reoriented Integrated Ocean Drilling Program core samples. Earth and Planetary Science Letters 287 (1-2) , pp. 217-228. 10.1016/j.epsl.2009.08.007

Full text not available from this repository.

Abstract

Oceanic core complexes expose lower crustal and upper mantle rocks on the seafloor by tectonic unroofing in the footwalls of large-slip detachment faults. The common occurrence of these structures in slow and ultra-slow spread oceanic crust suggests that they accommodate a significant component of plate divergence. However, the subsurface geometry of detachment faults in oceanic core complexes remains unclear. Competing models involve either: (a) displacement on planar, low-angle faults with little tectonic rotation; or (b) progressive shallowing by rotation of initially steeply dipping faults as a result of flexural unloading (the “rolling-hinge” model). We address this debate using palaeomagnetic remanences as markers for tectonic rotation within a unique 1.4 km long footwall section of gabbroic rocks recovered by Integrated Ocean Drilling Program (IODP) sampling at Atlantis Massif oceanic core complex on the Mid-Atlantic Ridge (MAR). These rocks contain a complex record of multipolarity magnetizations that are unrelated to alteration and igneous stratigraphy in the sampled section and are inferred to result from progressive cooling of the footwall section over geomagnetic polarity chrons C1r.2r, C1r.1n (Jaramillo) and C1r.1r. For the first time we have independently reoriented drill-core samples of lower crustal gabbros, that were initially azimuthally unconstrained, to a true geographic reference frame by correlating structures in individual core pieces with those identified from oriented imagery of the borehole wall. This allows reorientation of the palaeomagnetic data, placing far more rigorous constraints on the tectonic history than those possible using only palaeomagnetic inclination data. Analysis of the reoriented high temperature reversed component of magnetization indicates a 46° ± 6° anticlockwise rotation of the footwall around a MAR-parallel horizontal axis trending 011° ± 6°. Reoriented lower temperature components of normal and reversed polarity suggest that much of this rotation occurred after the end of the Jaramillo chron (0.99 Ma). The data provide unequivocal confirmation of the key prediction of flexural, rolling-hinge models for oceanic core complexes, whereby oceanic detachment faults initiate at higher dips and rotate to their present day low-angle geometries as displacement increases.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Earth and Ocean Sciences
Subjects: G Geography. Anthropology. Recreation > GC Oceanography
Q Science > QE Geology
Uncontrolled Keywords: IODP; oceanic core complex; rotation; palaeomagnetism
Publisher: Elsevier
ISSN: 0012-821X
Last Modified: 04 Jun 2017 02:09
URI: http://orca.cf.ac.uk/id/eprint/10021

Citation Data

Cited 42 times in Google Scholar. View in Google Scholar

Cited 66 times in Scopus. View in Scopus. Powered By Scopus® Data

Cited 38 times in Web of Science. View in Web of Science.

Actions (repository staff only)

Edit Item Edit Item