A METHOD FOR SEA-FLOOR CLASSIFICATION USING DIRECTIONAL VARIOGRAMS, DEMONSTRATED FOR DATA FROM THE WESTERN FLANK OF THE MID-ATLANTIC RIDGE

Seafloor classification is aimed at quantitatively characterizing seaf loor properties such as roughness and anisotropy, and at using such sp atial characteristics to distinguish geological provinces automaticall y. From geostatistical principals, a variogram method is developed for seafloor classification and it is demonstrated for data from the west ern flank of the Mid-Atlantic Ridge at 25-degrees-45'N to 26-degrees-4 0'N. This study uses HYDROSWEEP bathymetric data which have been ping- edited to flag erroneous data records, and navigation corrected. The c lassification method can handle the resultant data gaps inside the sur vey swaths as well as interpret data from several swaths. For a suite of test areas representative of different geological provinces, direct ional variograms are calculated, and characteristic parameters are ext racted for the classification. Examples include a sediment pond, abyss al hill terrain in several segments and of variable spacing, inside an d outside comers of ridge discontinuities, and mixed morphological for ms. The dependency of the results on random or regular subsampling and on the size of the test area is investigated.