SEISMIC REFLECTION PROFILES OF THE NORTH ATLANTIC NOW ON THE WEB

During the 1960’s and 1970’s research ships of the Lamont-Doherty Earth Observatory gathered numerous analog single-channel seismic profiles. Thousands of photographic negatives were scanned by the National Geophysical Data Center as part of the LDEO Data Rescue Project. These digital images from the North Atlantic have been geo-referenced and incorporated into a database for the dynamic and publicly accessible GeoMapApp dataviewer developed at Lamont-Doherty with support from the National Science Foundation. GeoMapApp is a freely downloadable Java application (http://www.geomapapp.org) that allows internet users to interactively browse a worldwide bathymetry database, generate and download custom grids and maps, as well as view a variety of other data types including seismic reflection profiles. The digital reflection profile images reveal details of sediment thicknesses and stratigraphic relationships with the igneous basement, which had previously only been available via the LDEO paper archives. Preliminary analysis has found a symmetric distribution of pelagic sediments on the mid-ocean ridge flanks and similarities between sediments of Jurassic and Early Cretaceous age on the conjugate North American and African margins. However, since cooling in the Oligocene and the onset of a vigorous deep thermal-haline circulation, the younger sediments on the opposing margins have taken different trajectories in their evolution. Broad continental rise prisms appear on the North American margin with a canyon- dissected slope, whereas the African margin has remained relatively starved. The seismic profiles also reveal asymmetries of igneous basement depth across the ridge related to patterns of ridge segmentation.