This research was designed to check the assumption of the grain-size control on a gas hydrate presence in the Blake Ridge sediments; the assumption had originated from the data gained at Deep Sea Drilling Project (DSDP) Site 533. Granulometric analysis (the combined pipette-sieve method) of the 345 sediment samples obtained after pore-water squeezing from Ocean Drilling Program (ODP) Sites 994, 995, and 997 has provided support for this assumption. The zone of negative anomalies of pore-water chlorinity, which is generally recognized to be gas hydrate bearing, is confined, as a whole, to the interval of comparatively coarse-grained sediments in each of the three site columns because content of the fine fractions <0.05, <0.01, <0.005, and <0.001 mm is lower there (although the character of this control changes from site to site). The individual chlorinity anomalies also coincide, for the most part, with relatively coarse-grained sediments.
1Paull,
C.K., Matsumoto, R., Wallace, P.J., and Dillon, W.P. (Eds.), 2000. Proc. ODP,
Sci. Results, 164: College Station, TX (Ocean Drilling Program).
2Research Institute
for Geology and Mineral Resources of the Ocean, 1, Angliyskiy Prospect, 190121,
St. Petersburg, Russia. Correspondence author: soloviev@gashyd.spb.ru
3Deceased.
Date of
initial receipt: 15 April 1998
Date of acceptance: 10 March 1999
Ms 164SR-236