41. THE RELATIONSHIP BETWEEN THE "R2 " SEISMIC REFLECTOR AND A ZONE OF ABUNDANT DETRITAL AND AUTHIGENIC SMECTITES, DEEP SEA DRILLING
In Hole 610, seismic Reflector "R2 " is caused by an abrupt increase in sediment sonic velocity at approximately the lower/middle Miocene boundary. This increase in sonic velocity results from a zone of well-developed massive smectite cement. Scanning electron microscope, Energy Dispersive...
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| Format: | Text |
| Language: | English |
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| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.530.1434 http://www.deepseadrilling.org/94/volume/dsdp94pt2_41.pdf |
| Summary: | In Hole 610, seismic Reflector "R2 " is caused by an abrupt increase in sediment sonic velocity at approximately the lower/middle Miocene boundary. This increase in sonic velocity results from a zone of well-developed massive smectite cement. Scanning electron microscope, Energy Dispersive System, and X-ray diffraction studies show that the massive cement has a morphology distinctly different from the common crystalline detrital smectite that occurs disseminated throughout the sediment. These studies also suggest that both forms of smectite have similar compositions. A widespread northeast Atlantic hiatus at the lower/middle Miocene boundary suggests there was increased bottom-current activity during the early middle Miocene. This increased circulation probably led to the scouring and entrain-ment of Norwegian Sea smectite and volcanic ash and their subsequent deposition at Site 610. This ash later altered to form the smectite cement responsible for reflector "R2." |
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