Origin and Geomorphic Characteristics of Ocean Basins

The results of a multivariate classification of ocean basins is presented, based on an existing digital global map of seafloor features that are related to major phases of evolution, namely young, mature, declining and terminal evolutionary stages. “Young” basins are characterised by the absence of ocean trenches, young ocean crust (<8 MA), large areas of continental slope, thick sediments, and large percentage area of mid-ocean ridge rift valley (above 1.7%). “Mature” ocean basins are characterised by relatively thick sediment deposits (mean of 940 m), large percentage areas of continental rise (mean of 19.8%) and large areas of submarine fans (mean of 4.3%). The area of ocean trench is relatively small in all “mature” ocean basins, ranging from 0 to 0.3%. A defining geomorphic feature of the “declining” category is that around 1% of their area is trench. “Declining” ocean basins contain the highest concentration of seamounts (3.5–5 seamounts per 100,000 km2), which is more than double the mean value (1.4 seamounts per 100,000 km2) that occurs for the “mature” category with the next highest concentration. The “terminal” category of ocean basins is characterised by the greatest mean sediment thickness (4311 m) and greatest percentage area of submarine fans (7.2%) of any ocean basin. Bottom water occurring within 33 major bathymetric basins (located within the broader ocean basins) is found to exhibit a spatial relationship to near-bottom dissolved oxygen (DO) concentrations. Gradients of decreasing DO concentration suggests bottom water pathways within basins and between adjacent basins of similar (or greater) depth.