During the summer of 1988, multibeam bathymetric data ("Seabeam"), and magnetic data were acquired by the Marine Geoscience Department of IFREMER, on Mohn's Ridge, near 72-degrees-N, over a 200 X 250 km wide area, in the Norwegian-Greenland Sea. Thanks to a very dense and specific coverage, produced from ship's tracks which were both perpendicular and parallel to the ridge axis, different phases of sea-floor spreading were identified for the past 12 Ma. For the period comprised between anomaly 5 (about 9 Ma) and anomaly 3 A (about 5 to 6 Ma), a phase of dramatic decrease of spreading rate is observed, from about 10 mm/y to about 5 mm/y. Between anomaly 3 A and anomaly 2 A (about 3 Ma), spreading starts again: an increase of spreading rate occurs (up to values of about 9 to 10 mm/y), together with a global surelevation of the acoustic basement, over the whole of our study area. The period about 3 Ma may correspond to a local enhancement of tectonovolcanic activity. Between anomaly 2 A and present time, average spreading rate values are about 8 to 9 mm/y. No variation of spreading rate can be inferred from the data during this period.
