NEW MAPS FOCUS 30-ODD YEARS OF INVESTIGATION OF THE ESCANABA TROUGH SPREADING CENTER

The Escanaba Trough spreading ridge (half-spreading rate 2.4 cm/yr) is one of the best-studied sediment-buried mid-ocean ridges. Escanaba trough has been imaged by multiple geophysical and seismic surveys conducted at varying scales over the last 4 decades. Twenty-two camera tows and 26 dredge hauls provided targets for 4 manned submersible and 4 ROV dive cruises that resulted in a large amount of observational data on a local scale. Multiple hydrothermally active and inactive massive sulfide deposits have been sampled. Volcanic flows erupted through the sediment cover have been mapped and sampled. Thirty-six gravity and piston cores and two legs of scientific drilling by ODP/IODP provided constraints on the sedimentary and tectonic evolution of the spreading center. However, our understanding of the detailed history of the spreading center has taken a quantum leap forward as the previously collected data can now be interpreted in the context of bathymetric maps with 10 cm vertical and 1 m lateral resolution prepared from data collected by the MBARI AUV D. Allan B. Faulting, sediment redistribution features, igneous flow morphology and shallow intrusive processes, and hydrothermal deposits observed on the sea floor can now be constrained by their geometry and spatial extent. Sidescan data define the extent of surface lava flows. Chirp (2-16 khz) subbottom seismic profiles collected along the survey lines provide a time integrated history of the upper 100 meters or so of sedimentary units locally disrupted by tectonic and igneous events. The seismic images can be interpreted in terms of physical parameters and age constraints provide by IODP drill cores making this site one of the best areas for quantifying the tectonic, sedimentary, igneous and hydrothermal evolution of a slow spreading ridge.