. The Earth beneath the sea : History. Ocean bottom; Marine geophysics. 716 AKRHENIUS [chap. 25 matter higher than average and thus an overestimate for the extrapolated age. These conditions ilhistrate the desirabihty of stratigraphic control in sequences where absolute age determinations are attempted. Methods similar to those applied in the equatorial Pacific have been used by Emiliani (1955) and Broecker et al. (1959) to determine the absolute age relations of the Upper Pleistocene climatic stages in the Atlantic Ocean. Depth m 57 Core number 56 5 5 54 G> 5 — 53 —J— 52 51 UATERNARY iPl^i
. The Earth beneath the sea : History. Ocean bottom; Marine geophysics. 716 AKRHENIUS [chap. 25 matter higher than average and thus an overestimate for the extrapolated age. These conditions ilhistrate the desirabihty of stratigraphic control in sequences where absolute age determinations are attempted. Methods similar to those applied in the equatorial Pacific have been used by Emiliani (1955) and Broecker et al. (1959) to determine the absolute age relations of the Upper Pleistocene climatic stages in the Atlantic Ocean. Depth m 57 Core number 56 5 5 54 G> 5 — 53 —J— 52 51 UATERNARY iPl^iOr-ENE] 50. PLIOCENE 130° 120" w 130 X \0~' MIOCENE PaOs 53, ? 52 • 51 .5" • 55 »56 • 50 •57 20° !0°N Fig. 40. Stratigraphy of the present north equatorial clay facies in the Pacific on the basis of phosphate content of the sediment. The phosphate is due to skeletal debris of pelagic fish, and the concentration appears to be inversely proportional to the rate of accumulation of terrigenous components. Concentrations are given in g/g. Vertical lines correspond to the sediment cores indicated by numbers in the graph and in the map insert. The lower detached parts of the figure show older sediments now near the surface below unconformities of various age. C indicates the heterochronous calcium carbonate compensation surface, separating calcareous from non-calcareous deposits. This boundary moved south past approxi- mately latitude 15°N in the Upper Miocene and appears to have arrived near its present position (cf. Fig. 36) in Pliocene times. (After Arrhenius, 1952.) Emiliani assumes a low variability in time for both the inorganic and biotic sedimentary components. The stratigraphic subdivision used by Emiliani is based on changes in ocean surface temperature, whereas the stratification in the equatorial Pacific, as mentioned above, is presumably caused by productivity changes, induced by variations in trade-wind intensity. Since certainly both equator
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