The shapes and directionality of bathymetry at slow-spreading ridges are key to understanding the magmatic or tectonic emplacement of the crust. Magmatic terrain is marked by linearly fault-bounded abyssal hills, while tectonic terrain is marked by long-lived detachment faults, forming Oceanic Core Complexes (OCCs). However, the quantitative description of these crustal regimes is still limited. We develop a novel automated terrain classification technique and test it at the 13-15° N section of the Mid-Atlantic Ridge. The algorithm uses the Slope-Weighted Eccentricity (SWE) of the horizontal eigenvalues to represent surface directionality and reveal crustal tectonic fabric. The application of this new technique yields results consistent with qualitative interpretation. Thus, it provides both new insights into the mid-oceanic ridge spreading and the potential to automate such mapping with different sets of grids, such as gravity and magnetic data in regions further away from the ridge where sediments mask sea-bed features.

In recent years it has been recognised that parts of slow spreading ridges such as the Mid-Atlantic Ridge (MAR) are characterised by typical magmatic spreading, while other parts are characterised by the formation of detachment faults and Oceanic Core Complexes (OCC). These different spreading modes can be clearly identified in the near-ridge environment in the bathymetry, with magmatic mode crust characterised by linear fault-bounded ridges, and detachment mode crust by more chaotic bathymetric signatures. The aim of this project is to characterise the magnetic and gravity signatures of lithosphere created by different modes of spreading, with the aim of using these signatures to identify if the structures still remain in ocean-continent transitions, where they have been covered by sediments coming from the continental crust. We first characterise different modes of spreading using available high-resolution bathymetry data of the MAR up to 20 My of age. The identified characteristics are then related to the corresponding ship-borne gravity and magnetic data in the same area. From the gravity anomalies, thinner crust is observed where the OCCs are in place. This allows the mantle to be exhumed to the sea-floor. As for the magnetic anomalies, it is found that in places where OCCs are present, the anomalies are not as symmetrical as those found in magmatic mode regions. We present a range of parameters extracted from the data that characterise different spreading modes, and use these to test whether transitions between detachment and magmatic mode crust identified in the bathymetry can be readily identified in gravity and magnetic data.