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I.R. MacDonald, R. Sassen and A. Pichabchy
Resource Geosciences Division., Geochemical Environmental Research. Group
College of Geosciences, Texas A&M University
727 Graha,m Rd. College Station, TX 77845 voice 409-862-2323 ext. 119, fax 862 1347
Hydrocarbon seepage on the Gulf of Mexico slope nourishes extensive chemosynthetic communities, which are characterized by visually distinctive colonies of tube worms, seep mussels, and bacterial mats--as well as geological formations such as carbonate pavements and gas hydrates. Laser line scan image strips from four separate seeps were joined into >geo-referenced mosaics that covered areas of up to 150 by 250 m.
Mosaicking was accomplished by use of ER-Mapper, a remote-sensing and geophysical image-processing application. Spatial resolution was on the order of 1 to 2 cm and spectral resolution was sufficient to delineate all major seep components. Comparison of the mosaics demonstrates the differences between two major forms of seepage: sediment diffusion and brine pooling; in particular, the dynamics of the two processes are evident from comparison of seeps with different activity levels,. These sessile biological aggregations are indicators of persistent seepage through discrete seafloor areas over time-scales of tens or hundreds of years.
Measurement of their precise area can provide low-order estimates for the localized scale and distribution of seepage over time
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