Points along an isochron in the vicinity of an oceanic fracture zone

Points along the Kane Fracture Zone and picks along the older edge of marine magnetic anomaly C5n.2n (11.056 Myr). Location data from and Merkuriev and DeMets (2014).

Some resources associated with the presentation by Collins and Cronin at AGU 2018

Tectonophysics, Session T003, Application of Gravity, Magnetic and Heat Flow to Tectonic Studies,
Poster T43D-0417, Hall A-C, Walter E Washington Convention Center
Thursday, 13 December 2018, 13:40-18:00


The Length of Some (Perhaps All) R-R Transform Faults Changes Over Time. Why?

Ryley M. COLLINS and Vincent S. CRONIN, Geosciences Department, Baylor University, One Bear Place #97354, Waco, TX 76798-7354, ( and

ABSTRACT Many geoscientists assume that ridge-ridge transform faults along mid-ocean ridges have a constant geometry over finite time intervals until or unless some plate-reorganization event occurs. This assumption is based on the first-generation plate-kinematic model in which [1] transform faults were assumed to be concentric around an Euler pole that is fixed to the two plates over finite time intervals and, hence, [2] no convergence or divergence occurs along transform faults and [3] oceanic fracture zones follow small circles concentric to the Euler pole except where perturbed by plate reorganization (e.g., Morgan, 1968; McKenzie and Parker, 1967). These postulates of first-generation plate kinematics were disproven for finite displacements in the early 1970s on purely geometric-kinematic grounds (e.g., Cox, 1973), so plates must generally move in a non-circular finite trajectory relative to each other and the shape, length, and position of transform faults is likely to vary continuously over finite time intervals.

The traces of isochrons defined by marine magnetic anomalies are deflected as they cross oceanic fracture zones. The distance that a given isochron is deflected provides a measure of the approximate length of the transform fault associated with the fracture zone at that time. We used the best published data for the location of isochrons defined by marine magnetic anomalies ( to measure the variation in length of several transform faults during the Cenozoic, including some of the major transforms in the North Atlantic: Kane, Atlantis, Hayes and Oceanographer. The length of R-R transform faults examined in this study seems to have changed continuously over that time interval. For example, the Kane transform fault has lengthened from ~85 km at ~50 Ma, ~107 km at ~20 Ma, and ~132 km at ~10 Ma to its current length of ~147 km. A similar progression was noted for other transforms between the North American and Nubian (west African) plates. Reasons might include the generally non-circular finite relative motion of plates and the instantaneous instability of mid-ocean ridges (Cronin, 1994).

References and other relevant information are accessible via

This abstract is accessible online via the AGU Fall Meeting 2018 site at

Poster file

The poster, its contents, and the digital copy accessible via the link provided below are all copyright 2018 by Vincent S. Cronin. These resources are the intellectual and digital property of the coauthors, Ryley M. Collins and Vincent S. Cronin.

A PDF copy of the final poster file is accessible via

Codes in Mathematica v.11

References for this work

Some Online Resources

This is not a static resource, so please send your suggestions for additional resources to Vince Cronin via

Revised 13 November 2018

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