Sea-Level Change (1990) / Chapter Skim
Currently Skimming:
5 Quaternary Sea-Level Change
5 Quaternary Sea-Level Change
Pages 88-103
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 88... ...
After negotiating a long path through data and concepts of mixed quality, one finds global ice volume has fluctuated by tens of meters sea-level equivalent at rates that are difficult to resolve. Satellite monitoring of global ice volume appears only prudent.
|
From page 89... ...
. Peats Holocene brackish water peat deposits in close proximity to late Pleistocene subaerial exposure surfaces provide quite good stratigraphic indicators of paleosea level, which can be easily dated using the 14C method.
|
From page 90... ...
On the basis of impeccable geologic arguments, Rendezvous Hill (Barbados III) terrace, the Curacao +6 m terrace, and the Key Largo limestone of South Florida all represent deepsea isotope stage Se (event 5.5 in the SPECMAP terminology; taken to be centered around 122 kaBP; Imbrie et al., 1984~.
|
From page 91... ...
The ~80 Ice VolumelTemperature Relationship Calcium carbonate precipitated from sea water records some combination of information concerning the isotopic composition of the water and the temperature at which the calcium carbonate grew. Sizable variation in the isotopic composition of the sea water results from variation in global ice volume.
|
From page 92... ...
Recrystallization of unstable aragonite and high-magnesium calcite in proximity to soil gas imparts a highly negative 6~30 signal to sediments immediately below subaerial exposure surfaces. Similiarly, recrystallization of various unconformity-bounded packages of carbonate sediment generally occurs under slightly different conditions of global ice volume and/or climate.
|
From page 93... ...
Additionally, the New Guinea terrace sequence contains several younger terraces that are not represented on Barbados or Haiti because the uplift rate of Barbados and Haiti is considerably less than the uplift rate of the New Guinea terrace sequence. The Constant Uplift Rate Hypothesis Historically, a great deal of literature concerning relative sea level within the time interval 140 to 70 kaBP hinges on application of the "constant uplift rate hypothesis" (Broecker et al., 1968)
|
From page 94... ...
After discussion of the coral-reef terrace 6~80 record, I will return to integration of these data with the deep-sea 6~80 record and with sea-level estimates based on the coral-reef terrace constant-uplift hypothesis discussed above. The Barbados Coral-Reef Terrace ~ ~ SO Record Figure 5.1 presents a cross section of the Christ Church region of Barbados indicating the location of numerous cored boreholes and the position of a subaerial exposure surface ROBLEY K
|
From page 95... ...
RENDEZVOUS HILL KINGSLAND VENTNOR-t KENDAL HIL+BERDARE WORTHING: ~ / \ if, ' RKM 2) T ~RKM 23R ~ ~RKM 20R DEEP SEA RECORD ~RKM 22R THOUSANDS OF YEARS BEFORE PRESENT FIGURE 5.3 Comparison of Barbados coral isotope record with the stacked deep-sea planktonic isotope curve of Prell et al.
|
From page 96... ...
The deep-sea INTO record clearly demonstrates that isotope stage 2 and isotope stage 6 are comparable examples of maximum glaciation during late Pleistocene time. The Barbados borehole data capture 1.7 per mil 6~80 variation within an elevation variation of approximately 80 m.
|
From page 97... ...
, one notes re markable agreement between the new Barbados isotope data and the deep-sea cores. Estimates based on the ad hoc TABLE 5.1 Comparison of Terrace Elevation Data to Isotope Data from Corals and Low-Latitude Planktonic Foraminifers Terrace Elevation Barbados Corals Low-Latitude Data, 6~80 Fairbanks and Planktonic Isotope Stage equivalent,a Matthews (1978)
|
From page 98... ...
n = 6 n = 9 Rendezvous Hill (Barbados III) Ventnor (Barbados 11)
|
From page 99... ...
The Deep-Sea I;'80 Record as an Ice-Volume Signal In summary then, terrace elevation data, Barbados isotope data, and deep-sea isotope data are in close agreement within the time interval of Barbados terraces Worthing, Ventnor, and Rendezvous Hill (82 to 125 kaBP)
|
From page 100... ...
Taking all of these data literally, one is left with the unsatisfactory proposition that isotope stage 5.5 (equivalent to New Guinea reef VIIa) achieved a level somewhere between +2 and +6 m relative to present sea level by removal of an ice sheet in a manner inconsistent with the Wilson hypothesis, whereas isotope stage 5.5 was followed closely by a glacial surge (and resultant New Guinea reef VIIb)
|
From page 101... ...
opportunity is before us to model an empirically derived glacio-eustatic signal with mathematical formulations of basin subsidence and isostasy, for example. By way of example, Figure 5.4 presents a proposed stratigraphy of subaerial exposure surfaces within bankmargin carbonate rocks.
|
From page 102... ...
. The Last Great Ice Sheets, Wiley, New York, 484 pp.
|
From page 103... ...
Role of glacial Arctic Ocean ice sheets in Pleistocene oxygen isotope and sea level records, Earth Planet.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.