Sea-Level Change (1990) / Chapter Skim
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6 Graphic Analysis of Dislocated Quaternary Shorelines
6 Graphic Analysis of Dislocated Quaternary Shorelines
Pages 104-115
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From page 104... ...
A similar procedure gives the initial level of any shoreline in a sequence of submerged features, if their depths are plotted against the depth of the deepest shoreline in the sequence. Correlation coefficients for typical calculations are inflated because Hm' always incorporates all subsequent movements on that transect.
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From page 105... ...
The second is the scale of 103 to 104 yr, primarily considering the deglacial hemicycle of the last ice age and the most recent 10,000 yr of geologic history called the Holocene Epoch. On this time scale, glacial eustatic sea level has risen some 120 m as the Northern Hemisphere ice sheets disintegrated, and then it has stabilized or fluctuated slightly with the subsequent isostatic adjustments of the solid earth to the postglacial distribution of surface ice and water masses.
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From page 106... ...
final section of this chapter, if others could be found by drilling or in natural exposures, stadial and glacial minima as well as interstadial and interglacial maxima sea level could be dated and the amplitudes of sea-level fluctuations could be defined. In addition to the value of coral-reef models for predicting sea levels of the last 125 ka, an excellent predictive model of the ages of middle Pleistocene and older terraces can be made if one of the lowest terraces in the sequence can be proved to be of last interglacial age, about 125,000 yr old.
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From page 107... ...
were consistent with similar estimates for terraces on Barbados, where the average rate of tectonic uplift was only about 10 percent of the rate in Papua New Guinea. The converging estimates were regarded as reasonable for the interstadial sea-level maxima, so that the height of a terrace of similar age elsewhere could be converted into an uplift rate by adding the present terrace height above sea level to its estimated original height (which is for all interstadial terraces at or below present sea level)
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From page 108... ...
512~. TECTONIC MOVEMENTS ON THE TIME SCALE OF 20,000 YEARS The straight-line regression equations with high corre lation coefficients demonstrated above justify the assumption of constant uplift rate on the time scale of 105 yr, but do not require it on shorter times.
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From page 109... ...
based on six transects on the Huon Peninsula, Papua New Guinea (Bloom and Yonekura, 1985, Figure 6.31. Table 6.2 shows that there was variation in the Huon Peninsula uplift rate on the time scale of the 20,000-yr sampling interval.
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From page 110... ...
described a cut-and-fill cycle in the uplifted deltaic foreset beds of the Tewai River delta on the Huon Peninsula of Papua New Guinea. Coral reefs that grew on the ARTHUR L
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From page 111... ...
suggested how very rapid ice-sheet growth could occur around the margins of the North Atlantic if a relict mass of warm surface water remained in the region adjacent to abruptly cooled adjacent land masses. LATE-GLACIAL AND HOLOCENE SEA LEVELS: THE 103- TO 104-YEAR TIME SCALE Numerous Holocene sea-level graphs have been published (see Bloom, 1977~.
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From page 112... ...
', .-. 2 0 ~00 Ye ~ FIGURE 6.7 Distribution of the six predicted sea-level zones resulting from retreat of Northern Hemisphere ice sheets.
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From page 113... ...
and western European ports is due to isostatic adjustments downward that are analogous and proportional to the uplift farther north in more recently deglaciated reasons? The near-zero intercept of all the regression lines in Figure 6.8 would seem to indicate that.
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From page 114... ...
Furthermore, an obvious discrepancy persists between the absolute heights of interstadial sea-level maxima as interpreted from the deep-sea oxygen-isotope record and those calculated from uplifted coral reefs. The oxygen-isotope record of corals agrees with the record obtained from pelagic and benthic foraminifera, and so the problem is not to resolve a contra added for evaluating the correlation coefficients shown on Figure diction between the coral-reef and the deep-sea isotopic record, but to determine whether the oxygen isotope ratios document ice volumes or temperature, and whether tectonic uplift models of coral coasts are valid.
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From page 115... ...
(19741. Geology of coral terraces, Huon Peninsula, New Guinea: A study of Quaternary tectonic movements and sea-level changes, Geol.
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