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Geochronology and continental drift—the North Atlantic
Oceanographic Abstracts
779
curvilinearity of the response of development rate to temperature may be the same in different populations. Fecundity differs geographically, but total clutch volume, determined from egg diameter, is the same function of female length wherever Pseudocalanus occurs. Thus, if temperature characteristics of size, development rate, and fecundity can be obtained in detail from one population, they can be transferred to other populations. MENRAN A. R. and J. L. TR£MBLAY, 1965. Un aspect du metabolisme du zinc chez Littorina obtusata L, et Fueus edentatus de la Pylaie. Revue Canadienne de Biologic, 24 (3): 157-161. A tidal zone seaweed, Fucus edentatus and a mollusc of the same habitat, Littorina obtusata were put together in an apparatus duplicating the tidal phenomenon (thalassiotron) in sea water containing 2"5 ~,Ci o f Z n 6s per litre. The depletion o f this isotope in the water was followed as well as its absorption by these organisms. The depletion of Zn 65 in the sea water was very rapid at the beginning: 42 o/, of the zinc had disappeared from the water at the end of the first day, and after ten days the water did not contain more than 10 ~*/,of the initial amount of the isotope. Meanwhile the Littorina shov, ed a high absorption rate during the first two days, and after three days reached an equilibrium content o f Z n 6~ corresponding to 6.5 × 104 C.P.M. per gram of fresh animal tissue or 21 pg per gram of fresh tissue. The saturation of Fucus edentatus was reached after three to four days while the activity of its fresh tissues was o f 4"2 × 104 C.P.M.,'g. M£NARD H. W., 1965. The world.wide oceanic rise-ridge system. Phil. Trans. 1~. Soc., A, 25S (1088): 109-122. About half the l e n ~ h of the " o c e a n i c " rise-ridge system is centred in ocean basins. On the other hand, almost the whole system is approximately disposed in circles around continental shields. Exceptional heating of the system is indicated by high heat flow and the extrusion of extraordinary volumes of flood basalts. The concentration of volcanoes, however, is little greater than normal for ocean basins. Longitudinal normal faulting and transverse wrench faulting are characteristic o f the system. Both types formed early in the life of the system and are still active. Wrench faults offset belts of normal faulting and the crests of rises and ridges in many places but are not themselves known to be offset by normal faults. The ancient Darwin Rise has subsided in the southwestern Pacific. Its history differs in some respects from other rises although it too was heated and faulted. A hypothesis of origin o f the system is briefly discussed. Mn.t.rR J. A., 1965. Geochronology and continental drift--the North Atlantic. Phil. Trans. R. Soc., A, 258 (1088): 180--191. A geometri~l fit of the land masses of northern Europe, Canada and Greenland has been constructed by Dr. A. G. Smith using the method devised by Sir Edward Bunard and Mr. J. E. Everett. The method involves taking points of latitude and longitude on the 500 fm line at inte~'als of about 30 miles along the two coasts to be fitted. Young features such as oceanic islands are ignored. By a method of successive approximation, the computer '" homes i n " on to the centre of rotation which gives the minimum root mean square misfit between the rotated coastlines; the misfit being measured as the discrepancy of longitude relative to the centre of rotation. In this manner the 500 fm line along the east coast of Greenland has been fitted to that of northwestern Europe to form one unit. This unit, that is, the 500 fm line of the west coast of Greenland and the Channel approaches have been fitted on to the 500 fm line of Canada. Maps of this fit drawn as a conical projection with two standard parallels o f latitude will be presented and will show the geochronological patterns across the reconstructed land masses. MURRAY J. W., 1965. Significance of benthic foraminiferids in plankton samples. J. Palaeont., 39 (1): 156-157. After a period of storms during January 1962, dead, empty tests o f benthic foraminiferids were found in six plankton samples collected from three stations across the Channel in the surface 10 m of water. Only thin-walled forms were represented and most of these were 0.15---0.20 m m in length or diameter according to shape. Disturbance of the sea floor sediments during the storms had led to the preferential removal of these small foraminiferids and the mechanism would enable them to be widely dispersed before they settled back to the sea floor. This phenomenon must be considered when making a palaeoecological interpretation of fossil foraminiferid assemblages. NICNOLUS G. D., 1965. Petrological and geochemical evidence for convection in the Earth's mantle. Phil Trans. R. Soc., A, 258 0088): 168--179. Various lines of evidence suggest that layer 3 of the oceanic material is partially serpentinized periodotite. Hess (1962) suggested that this layer originated by serlmntinization of the upper part of the mantle, the necessary water being derived from the degassing of rising columns of mantle convection cells beneath the mid-ocean ridges In this paper it is shown that support for this hypothesis can be derived from two entirely differentlines of evidence. The firstconcerns the characters of volcanic lavas extruded in oceanic areas. Although these are, in general terms, basaltic, significant minor differences exist between basalts dredged from
779
curvilinearity of the response of development rate to temperature may be the same in different populations. Fecundity differs geographically, but total clutch volume, determined from egg diameter, is the same function of female length wherever Pseudocalanus occurs. Thus, if temperature characteristics of size, development rate, and fecundity can be obtained in detail from one population, they can be transferred to other populations. MENRAN A. R. and J. L. TR£MBLAY, 1965. Un aspect du metabolisme du zinc chez Littorina obtusata L, et Fueus edentatus de la Pylaie. Revue Canadienne de Biologic, 24 (3): 157-161. A tidal zone seaweed, Fucus edentatus and a mollusc of the same habitat, Littorina obtusata were put together in an apparatus duplicating the tidal phenomenon (thalassiotron) in sea water containing 2"5 ~,Ci o f Z n 6s per litre. The depletion o f this isotope in the water was followed as well as its absorption by these organisms. The depletion of Zn 65 in the sea water was very rapid at the beginning: 42 o/, of the zinc had disappeared from the water at the end of the first day, and after ten days the water did not contain more than 10 ~*/,of the initial amount of the isotope. Meanwhile the Littorina shov, ed a high absorption rate during the first two days, and after three days reached an equilibrium content o f Z n 6~ corresponding to 6.5 × 104 C.P.M. per gram of fresh animal tissue or 21 pg per gram of fresh tissue. The saturation of Fucus edentatus was reached after three to four days while the activity of its fresh tissues was o f 4"2 × 104 C.P.M.,'g. M£NARD H. W., 1965. The world.wide oceanic rise-ridge system. Phil. Trans. 1~. Soc., A, 25S (1088): 109-122. About half the l e n ~ h of the " o c e a n i c " rise-ridge system is centred in ocean basins. On the other hand, almost the whole system is approximately disposed in circles around continental shields. Exceptional heating of the system is indicated by high heat flow and the extrusion of extraordinary volumes of flood basalts. The concentration of volcanoes, however, is little greater than normal for ocean basins. Longitudinal normal faulting and transverse wrench faulting are characteristic o f the system. Both types formed early in the life of the system and are still active. Wrench faults offset belts of normal faulting and the crests of rises and ridges in many places but are not themselves known to be offset by normal faults. The ancient Darwin Rise has subsided in the southwestern Pacific. Its history differs in some respects from other rises although it too was heated and faulted. A hypothesis of origin o f the system is briefly discussed. Mn.t.rR J. A., 1965. Geochronology and continental drift--the North Atlantic. Phil. Trans. R. Soc., A, 258 (1088): 180--191. A geometri~l fit of the land masses of northern Europe, Canada and Greenland has been constructed by Dr. A. G. Smith using the method devised by Sir Edward Bunard and Mr. J. E. Everett. The method involves taking points of latitude and longitude on the 500 fm line at inte~'als of about 30 miles along the two coasts to be fitted. Young features such as oceanic islands are ignored. By a method of successive approximation, the computer '" homes i n " on to the centre of rotation which gives the minimum root mean square misfit between the rotated coastlines; the misfit being measured as the discrepancy of longitude relative to the centre of rotation. In this manner the 500 fm line along the east coast of Greenland has been fitted to that of northwestern Europe to form one unit. This unit, that is, the 500 fm line of the west coast of Greenland and the Channel approaches have been fitted on to the 500 fm line of Canada. Maps of this fit drawn as a conical projection with two standard parallels o f latitude will be presented and will show the geochronological patterns across the reconstructed land masses. MURRAY J. W., 1965. Significance of benthic foraminiferids in plankton samples. J. Palaeont., 39 (1): 156-157. After a period of storms during January 1962, dead, empty tests o f benthic foraminiferids were found in six plankton samples collected from three stations across the Channel in the surface 10 m of water. Only thin-walled forms were represented and most of these were 0.15---0.20 m m in length or diameter according to shape. Disturbance of the sea floor sediments during the storms had led to the preferential removal of these small foraminiferids and the mechanism would enable them to be widely dispersed before they settled back to the sea floor. This phenomenon must be considered when making a palaeoecological interpretation of fossil foraminiferid assemblages. NICNOLUS G. D., 1965. Petrological and geochemical evidence for convection in the Earth's mantle. Phil Trans. R. Soc., A, 258 0088): 168--179. Various lines of evidence suggest that layer 3 of the oceanic material is partially serpentinized periodotite. Hess (1962) suggested that this layer originated by serlmntinization of the upper part of the mantle, the necessary water being derived from the degassing of rising columns of mantle convection cells beneath the mid-ocean ridges In this paper it is shown that support for this hypothesis can be derived from two entirely differentlines of evidence. The firstconcerns the characters of volcanic lavas extruded in oceanic areas. Although these are, in general terms, basaltic, significant minor differences exist between basalts dredged from