OLR 11987) 34 (9) D. Submarine Geology and Geophysics 759

Delaware, and Hatteras deposits are from large Appalachian river systems; the southern New Jersey and southern Delmarva deposits are eroded from outcrops of coastal-plain strata. Dept. of Geol., Texas A&M Univ., College Station, TX 77843, USA.

87:5053 Schwarzacher, W., 1987. The analysis and inter-

pretation of stratification cycles. Paleoceanog- raphy, 2(1):79-95.

Stratification cycles (cyclic repetitions of beds or bundles of beds separated by distinct layers) from 0.5 m to several meters thick are present throughout the geological column. The analysis of the cycles involves regional mapping; petrographic examina- tion (in particular, analyses of primary structures): and quantitative analysis of vertical sections using power spectral methods to detect superimposed cycles. The latter approach is illustrated using lower Carboniferous limestone sections from NW Ireland. Similar cyclic Upper Jurassic limestone marl suc- cessions from southern Germany and Late Creta- ceous and Early Tertiary successions from Italy suggest that they are ultimately caused by variations in the Earth's orbit, although the exact mechanism which links sedimentation with orbital variations is not known. Dept. of Geol., Queen's Univ., Belfast, Northern Ireland.

87:5054 Wetzel, Andreas, 1987. Sedimentoiogical significance

of strain and sonic velocity anisotropy in fine- grained turbiditic and hemipelagic deep-sea sed- iments. An example from the Mississippi Fan. Mar. Geol., 74(3-4):191-207.

In visually homogeneous, compositionally similar, argillaceous sediment of the Mississippi Fan, depo- sitional processes are reflected in the anisotropy of strain and sonic velocity. In single beds, the turbiditic part is characterized by an anisotropy within bedding and comparatively low anisotropy between vertical and horizontal directions. In dep- ositional sequences, anisotropy pattern depends on sequence type. The general correspondence between trends in lithology and anisotropy documents rela- tive changes in predominant depositional process within a specific fan subenvironment. Degrees of both types of anisotropy differ from site to site and provide useful supplementary information for inter- preting fan environments. Compaction generally leads to increasing anisotropy in both turbiditic and hemipelagic sediments. Inst. und Mus. fur Geol. und Palaontol., Univ. Tubingen, Sigwartstr. 10, D-7400 Tubingen, FRG.

D140. Submarine hydrology (springs, hy- drothermal deposits, etc.)

87:5055 Little, S.A., K.D. Stolzenbach and R.P. Von Herzen,

1987. Measurements of plume flow from a hydrothermal vent field [on the EPRI. J. geophys. Res., 92(B3):2587-2596.

The convective flow emanating from a hydrothermal vent field approaches an ideal plume in the tem- perature and velocity distribution. Such parameters as total heat flow and maximum plume height can be estimated using either the velocity or the temper- ature information; results are in close agreement, yielding a total heat flow from this vent site (10°56"N, 103°41"W) of 3.7+_0.8 MW and a maximum height of 150_+10 m. The nonlinear effects of large temperature variations on heat capacity and volume changes slightly alter the calculations applied to obtain these values. WHOI, Woods Hole, MA 02543, USA.

87:5056 Urabe, T., M. Yuasa and S. Nakao et al., 1987.

Hydrothermal sulfides from a submarine caidera in the Shichito-lwojima Ridge, northwestern Pacific. Mar. Geol., 74(3-4):295-299.

Sulfide minerals observed in the sample are domi- nantly pyrite with minor amount of sphalerite and Cu-Fe-sulfide. They occur in 5 mm thick veinlets together with euhedral quartz and chlorite. The high filling temperatures (~290°C) of fluid inclusions in the quartz crystals and enrichment of gold in vein materials both indicate a hydrothermal origin of the sulfides. This is, to our knowledge, the first discovery of hydrothermal precious and base-metal mineral- izations associated with front volcanism in the marine environment. Geol. Survey of Japan, 1-1-3 Yatabe-Higashi, Tsukuba 305, Japan.

87:5057 Varnavas, S.P., 1987. Marine barite in sediments

from Deep Sea Drilling Project sites 424 and 424A (Galapagos hydrothermal mounds field). Mar. Chem., 20(3):245-253.

Barite in these deposits is associated with calcareous sediments and is completely absent from the hydro- thermal material; concentrations tend to increase in the deeper sediments. Although nontronite is formed within buried sediments the environmental condi- tions (reducing) occurring during its formation prevent barite formation. The association of barite with calcareous sediments is due to the release of Ba by calcareous microorganisms or to high concen- trations of Ca in the pore waters. Dept. of Geol., Univ. of Patras, Patras, Greece.