STOCHASTIC-ANALYSIS OF SEA-FLOOR MORPHOLOGY ON THE FLANK OF THE SOUTHEAST INDIAN RIDGE - THE INFLUENCE OF RIDGE MORPHOLOGY ON THE FORMATIONOF ABYSSAL HILLS

In this study we estimate the statistical properties of abyssal hill m orphology adjacent to the Southeast Indian Ridge in a region where the axial morphology changes from axial high to axial valley without a co rresponding change in spreading rate. We explore the influence of axia l morphology on abyssal hills and place these results within the conte xt of response to spreading rate. Two cruises aboard the RN Melville c ollected Sea Beam 2000 multibeam data along the Southeast Indian Ridge , providing continuous multibeam coverage of the axis from degrees 89 degrees W to similar to 118 degrees W, and similar to 100% coverage wi thin four survey regions extending out to similar to 45 km (similar to 1.2 Ma) from the axis [Semptre' et al., 1997; Cochran et al., 1997]. We apply the statistical modeling method of Goff and Jordan [1988] to gridded data from the four survey areas, examining in particular estim ates of abyssal hill rms height, characteristic width and length, aspe ct ratio, and skewness. Two analyses are performed: (1) comparison of the along-axis variation in abyssal hill characteristics to ridge segm entation, and (2) a calculation of population statistics within axial high, intermediate, and axial valley data populations of this study, a nd comparison of these results to population statistics derived from s tudies adjacent to the Mid-Atlantic Ridge and East Pacific Rise. We fi nd that abyssal hills generated along axial high mid-ocean ridges are very different from those generated along axial valley mid-ocean ridge s, not only with respect to size and shape, but also in their response to such factors as spreading rate and segmentation.