OLR (1982) 29 (12) D. Submarine Geology and Geophysics 781

convergent plate boundaries,' and similarities be- tween marginal-basin basalts and MORB and between island-arc basalts and OIB. Elucidation of convergent-margin magmatism awaits further data. Programs in Geosci., Univ. of Texas, Box 688, Richardson, Tex. 75080, USA. (isz)

D290. Crust, mantle, core

82:6128 Barrett, T.J., H.C. Jenkyns, J.K. Leggett, A.H.F.

Robertson (comment), B.J. Bluck and A.N. Halliday (reply), 1982. Age and origin of the Ballantrae ophiolite and its significance to the Caledonian orogeny and the Ordovician time scale. Forum. Geology, geol. Soc. Am., 10(6): 331-333.

82:6129 Boak, J.L. and R.F. Dymek, 1982. Metamorphism of

the ca. 3800 Ma supracrustal rocks at Isua, West Greenland: implications for Early Archaean crus- tal evolution. Earth planet. Sci. Letts, 59(1): 155- 176. Dept. of Geol. Sci., Harvard Univ., Cam- bridge, Mass. 02138, USA.

82:6130 Crampin, Stuart (comment) and G.E. Backus (reply),

1982. [Seismic anisotropy of the oceanic upper- most manfle.I (Discussion.) J. geophys. Res., 87(B6):4636-4644.

82:6131 Forsyth, D.W., 1982. Determinations of focal depths

of earthquakes associated with the bending of oceanic plates at trenches. Phys. Earth planet. Interiors, 28(2): 141-160.

Focal depths of 12 intra-plate, sub-oceanic earth- quakes are determined from study of the original seismograms, analysis of surface wave radiation patterns, and modelling of long-period wave forms. The pattern of stresses within the bending litho- sphere 'is one of horizontal, deviatoric tension down to a depth of ~25 km, with horizontal compression at greater depths.' Dept. of Geol. Sci., Brown Univ., Providence, RI 02912, USA. (msg)

82:6132 Foucher, J.-P., X. Le Pichon and J.-C. Sibuet, 1982.

The ocean-continent transition in the uniform lithospheric stretching model: role of partial melting in the mantle. Phil. Trans. R. Soc., (A)305(1489):27-43.

Transition from continental lithosphere stretching to oceanic accretion is probably controlled by produc- tion of significant partial melting in the astheno- sphere immediately below the lithosphere, which requires stretching factors >3. At stretching factors >2, the law of subsidence is significantly changed by the presence of partial melt in the asthenosphere. Implications for the existence of deep continental margin basins on thinned continental crusts are examined. Centre Oceanol. de Bretagne, B.P. 337, 29273 Brest Cedex, France.

82:6133 LaGabrielle, Yves and J.-M. Auzende, 1982. Active

in-situ disaggregation of oceanic crust and mantle on Gorringe Bank: analogy with ophiolitic mas- sives. Nature, Loud., 297(5866):490-493.

Additional Cyana SP 3000 dives on Gorringe Bank confirm that the bank (located at the boundary of the European and African plates) (1) has tilted to expose oceanic crust and mantle, and (2) shows evidence of compressive and shearing events--phe- nomena associated with the disintegration of serpen- tinites and gabbros. Beds of ophiolitic breccias and pelagic sediments in mountain belts are compared with the Gorringe Bank observations. GIS Oceanol. et Geodynam., U.B.O. ave Le Gorgeu, 29200 Brest, France. (fcs)

82:6134 Turcotte, D.L. and C.L. Angevine, 1982. Thermal

mechanisms of basin formation. Phil. Trans. R. Soc., (A)305(1489):283-294.

Thermal subsidence of the seafloor explains the observed bathymetry of ocean ridges. A similarity solution for a 1-D cooling model successfully predicts bathymetry, heat flow and geoid anomalies under a wide range of conditions; can be modified to predict the thermal subsidence of sedimentary basins; and agrees well with the observed subsidence history of a variety of basins. For older basins it is necessary to consider an input of heat to the base of the lithosphere that places a limit on subsidence. An empirical model for the conversion of kerogen- to-oil-to-gas is used in conjunction with the thermal evolution predicted by the similarity solution in order to determine the oil window and relative volume of oil as a function of basin age. Dept. of Geol. Sci., Cornell Univ., Ithaca, NY 14853, USA.

82:6135 Watts, A.B., G.D. Karner and M.S. Steckler, 1982.

Lithospberic flexure and the evolution of sedi- mentary basins. Phil. Trans. R. Soc., (A)305 (1489):249-281.