The influence of biogenic silica on seismic lithostratigraphy at ODP Sites 642 and 643, eastern Norwegian Sea

• Main Authors: Hempel, Peter, Mayer, Larry A., Taylor, Elliot, Bohrmann, Gerhard, Pittenger, Alan
• Format: Text
• Language: unknown
• Published: University of New Hampshire Scholars' Repository 1989
• Subjects: 12 Stratigraphy; Historical Geology and Paleoecology; 20 Geophysics; Applied Arctic Ocean; biogenic processes; bulk density; Cenozoic; clastic rocks; diatomaceous earth; geophysical methods; geophysical surveys; impedance; Leg 104; lithostratigraphy; marine geology; neutron methods; Norwegian Sea; Ocean Drilling Program; oceanography; ODP Site 642; ODP Site 643; porosity; sedimentary rocks; seismic methods; seismograms; silica; stratigraphy; surveys; synthetic seismograms; Geology; Oceanography and Atmospheric Sciences and Meteorology; Arctic; Arctic Ocean
• Online Access: https://scholars.unh.edu/ccom_affil/48; https://scholars.unh.edu/cgi/viewcontent.cgi?article=1047&context=ccom_affil

Drilling at ODP Sites 642 and 643 revealed a 250 m-thick section of diatomaceous Pliocene to Miocene sediments on the outer Vdring Plateau, eastern Norwegian Sea. These biogenic silica-rich sediments have a significantly lower saturated bulk density than the surrounding sediments, causing a decrease in acoustic impedance, which is seismically expressed as a negative polarity reflection. Variations in sonic velocity, the other key parameter in seismic analysis, is only of secondary importance in creating impedance contrasts in our study. Synthetic seismograms were produced from shipboard physical property measurements corrected for in situ conditions. These synthetic seismograms are in good agreement (< 6 m) with high-resolution air-gun seismic profiles shot during extensive seismic surveys on the Vdring Plateau and provide the basis for correlations between the seismic record and the borehole. The ability to unambiguously identify seismic horizons associated with biogenic silica deposits on the Vdring Plateau will permit the mapping of Miocene productivity patterns.