OLR(1979)26(12) C. Submarine Geology and Geophysics 777

79:5977 Milliman, J. D., 1979. Morphology and structure of

Amazon upper continental margin. Am. Ass. Petrol. Geol. Bull., 63(67: 934-950.

The development of the Amazon continental margin has been outlined based on integration of seismic reflection and refraction, gravity, and magnetic data. Cretaceous rifting of South American and African Precambrian shields was followed by Cretaceous and Paleogene shallow marine deposition of terrigenous sediments; then, uplift of the Andes in the Middle Miocene caused increased terrigenous influx and initiated formation of the Amazon Cone. Quaternary sea level fluctuations affected the sedimentary regime on the Amazon, causing sedimentation on the outer margin during low stands, and transport along the inner shelf during high stands. Figures include seismic reflection profiles. Woods Hole Oceanographic Institution, Woods Hole, Mass. 02543, U.S.A. (dme)

5. Gravity, geodesy and magnetism 79:5978

Baer, A. J., 1979. An unconventional Proterozoic paleomagnetic polar wander path for North America and its advantages. Phys. Earth planet. Interiors, 19(1): 100-105.

An alternative solution to the statistical derivation of cyclical polar wander paths (Morris et al., 1979) is suggested. Two varieties of hairpins are identified that either close in the Northern Hemisphere and are related to tectonic events or close in the Southern Hemisphere without apparent tectonic significance. Probable Proterozoic displacement of North America and a possible correlation between APW path reorganization and onset of subduction processes are discussed. Department of Geology, University of Ottawa, Ottawa Kl N 6N5, Canada. (rio)

79:5979 Ellwood, B. B., 1979. Sample shape and magnetic

grain sizes: two possible controls on the anisotropy of magnetic susceptibility variability in deep-sea sediments. Earth planet. Sci. Letts, 43(2): 309-314.

The length to diameter ratio of synthetic cylinder samples, containing materials of different magnetic grain sizes, is varied in order to measure effects on the anisotropy of magnetic susceptibility (AMS). When the magnetic grain size is small, sample shape does affect AMS ellipsoid orientations. Previous anomalous AMS results may be related to these effects. Department of Geology, University of Georgia, Athens, Ga. 30602, U.S.A. (rio)

79:5980 Goslin, Jean, 1979. R~sultats de gravimetrie sur les

monts sous-marins du Marion Dufresne, de la Lc~na et de I'Ob (Ocean Indien austral). [Gravity results above the Marion Dufresne, Lena and Ob seamounts, southern Indian Ocean.[ C. r. hebd. S~anc. Acad. Sci., Paris, (B)288(15): 241-244.

Gravity models derived for the three seamounts imply compensation of the topographic highs by a root with densities of about 3.0 g /cm-3 and depths of about 35 km. An ancient volcanic episode near a mid-oceanic ridge is suggested as the emplacement mechanism for the seamount chain. Institut de Physique du Globe de Paris, Laboratoire de Grophysique marine, 4, avenue de Neptune, 94100 Saint-Maur-des-Fossrs. (rio)

79:5981 Guennoc, Pol, Helene Jonquet and J.-C. Sibuet, 1979.

Presentation d'une carte magn~tique de I'Atlan- tique Nord-Est. [Magnetic cartography of the north-east Atlantic: composed from aeromagnetic and surface data.] C. r. hebd. S~anc. Acad. Sci., Paris, (D)288(13): 1011-1013. Dc~partement de G~ologie marine du B.R.G.M., B.P. No. 6009, 45018 Orlrans Cedex, France.

79:5982 Henshaw, P. C. Jr. and R. T. Merrill, 1979. Charac-

teristics of drying remanent magnetization in sedi- ments. Earth planet. Sci. Letts, 43(2): 315-320.

Natural remanent magnetization in drving marine sediments is experimentally shown to be dependent upon sediment water content, magnetic grain shape and sediment type, but probably not upon chemical changes. Significant and relatively stable magnetization can result from drying in a weak field:

.proper storage of paleomagnetic core samples is discussed. Chevron Oil Field Research Company, La Habra, Calif. 90631, U.S.A. (rio)

79:5983 Hu, Chin-Cheng and R. S. Lu, 1979. Downward con-

tinuation of magnetic field and the magnetic anomalies of offshore Taiwan. Acta oceanogr. Taiwan, 9: !-8.

The sin x / x method was used to continue the airborne residual magnetic intensities in the offshore area of western and southern Taiwan downward to the sea surface. The downward continued magnetic anomalies were then contoured and tied with the reduced sea surface measurements in the offshore area of Eastern Taiwan to complete a marine magnetic anomaly contour map. The integrated map clearly indicates that the older Asian continental structure has interacted with the younger structures of the South China Sea Plate, the Luzon Arc, and the Ryukyu Arc in the vicinity of Taiwan. Includes a fold- out magnetic anomaly map, offshore Taiwan. Exploration and Development Research Center, Chinese Petroleum Corporation, Miaoli, Taiwan, Republic of China.