Figure 4. Detailed bathymetry in Pedro Channel and Walton Basin (Cunningham, 1998) represents the complexity and the segmented character of the seafloor morphology within the seaways along the northern Nicaraguan Rise. In association with the present-day carbonate banks (brick pattern) that have remained areas of neritic carbonate since the late Eocene, drowned banks and reefs observed in Pedro Channel and Walton Basin formed an east-west barrier along the northern Nicaraguan Rise, where continuous shallow-water environments prevailed from the late Eocene to early Miocene. Some of the carbonate banks and barriers (light gray pattern) subsided and drowned as late as the late middle Miocene (Cunningham, 1998). ODP Site 1000 is located in the Pedro Channel.