Abyssal hill characterization at the ultraslow spreading Southwest Indian Ridge

Heather Sloan (1) , Daniel Sauter , John A. Goff (2) , Mathilde Cannat (3)

1 Environmental, Geographical and Geological Sciences
2 RHUL - Royal Holloway [University of London]
3 IPGP - Institut de Physique du Globe de Paris

The morphology of the flanks of the Southwest Indian Ridge holds a record of seafloor formation and abyssal hill generation at an ultraslow spreading rate. Statistical analysis of compiled bathymetry and gravity data from the flanks of the Southwest Indian Ridge from 54°E to 67°E provides estimates of abyssal hill morphologic character and inferred crustal thickness. The extent of the compiled data encompasses a spreading rate change from slow to ultraslow at 24 Ma, a significant inferred variation in sub-axis mantle temperature, and a patchwork of volcanic and non-volcanic seafloor, making the Southwest Indian Ridge an ideal and unique location to characterize abyssal hills generated by ultraslow spreading and to examine the effect of dramatic spreading rate change on seafloor morphology. Root mean square abyssal hill height in ultraslow spreading seafloor ranges from 280 m to 320 m and is on average 80 m greater than found for slow-spreading seafloor. Ultraslow spreading abyssal hill width ranges from 4 km to 12 km, averaging 8 km. Abyssal hill height and width increases west-to-east in both slow and ultraslow spreading seafloor, corresponding to decreasing inferred mantle temperature. Abyssal hills persist in non-volcanic seafloor and extend continuously from volcanic to non-volcanic terrains. We attribute the increase of abyssal hill height and width to strengthening of the mantle portion of the lithosphere as the result of cooler subaxial mantle temperature and conclude that abyssal hill height is primarily controlled by the strength of the mantle component of the lithosphere rather than spreading rate.

Mots clés: Southwest Indian Ridge; abyssal hills; seafloor morphology

Domaines: Planète et Univers [physics]

Heather Sloan, Daniel Sauter, John A. Goff, Mathilde Cannat. Abyssal hill characterization at the ultraslow spreading Southwest Indian Ridge. Geochemistry, Geophysics, Geosystems, 2012, 13 (2), pp.n/a - n/a. ⟨10.1029/2011GC003850⟩. ⟨hal-00721836⟩