QUANTITATIVE CHARACTERIZATION OF ABYSSAL HILL MORPHOLOGY ALONG FLOW LINES IN THE ATLANTIC-OCEAN

The morphology of the seafloor, when sampled along flow lines of relative plate motion, represents an indirect geologic time series record of the processes which form it. Eventually we hope to be able to interpret this information so that we may improve our understanding of the workings of ridge-crest and off-ridge processes through time. This study takes an important step toward that goal by quantitatively characterizing, through stochastic modeling, the abyssal hill morphology along the available Sea Beam flow line data sets in the Atlantic. The six Sea Beam flow line data sets used in this study include two near the Kane Fracture Zone and four near the Rio Grande and Moore Fracture Zones. Stochastic parameters estimated from these flow lines, such as the rms height, lineament azimuth, characteristic widths, and plan-view aspect ratio, are plotted as a function of crustal age. In addition to testing available hypotheses, the purpose of this work is to investigate how the abyssal hill morphology changes with age and to correlate this behavior to known changes in ridge characteristics with age. These results place important constraints on our understanding of the process of seafloor creation, and begin to establish a baseline against which morphology may be interpreted in the absence of other information. Along the Kane Fracture Zone, variations in the estimated abyssal hill lineament azimuth, rms height, and plan-view aspect ratio with crustal age appear to be correlated in various ways with the segmentation history and also possibly with large changes in plate motion direction that have occurred there within the past 80 m.y. Along the Rio Grande and Moore Fracture Zones, variations in the lineament azimuth, rms height and other parameters as a function of crustal age am often significant on a approximately 5-10 m.y. Lime scale. These variations are difficult to interpret as yet. To emphasize longer time scale variations, the estimated rms heights from the South Atlantic flow lines are averaged over common age bins. This demonstrates a strong negative correlation of rms height with the spreading rate. However, when characteristic widths are averaged in this manner, no strong correlation with spreading rate is found. Large variations in this parameter occur on a approximately 25 m.y. time scale.