Isotopic records, dating

However, the Slowey et al. (1995) work on shallower carbonate bank sediments (off of the Bahamas) was successful and led to the dating of a number of important events in the marine oxygen isotope record (including the timing of the Last Interglacial (Slowey et al. 1996), Termination II (Henderson and Slowey 2000) and portions of the Penultimate Interglacial (Slowey et al. 1996, Robinson et al. 2002). The shallower depths obviate the most serious of the initial thorium problems encountered in the Nicaragua Rise work. 

Sampling and Precise Dating Requirements for Extracting Isotopic Records from Three Rings... 

At middle and southern European latitudes, farther from the immediate impact of glacier advances and retreats, well-dated isotope records from speleothems from widely spaced caves allow comparison of regional climate shifts. McDermott et al. (1999) found, for example that early Holocene warm conditions prevailed on the Atlantic seaboard (southern Ireland) while relatively cool conditions occurred in the Mediterranean region of southern France. At 3500 years these conditions were shown to reverse. In the eastern Mediterranean, oxygen and carbon isotope ratios have been used to determine wet and dry periods (Frumkin et al., 1994 Frumkin et al., 1999a, b Bar-Matthews et al., 1996). The wetter climate of the Holocene is recorded in the speleothems. 

Millenial-scale but low-amplitude oscillations are shown on virtually all the MIS 11 records of sufficient resolution (eg, Oppo et al, 1998) McManus et al (1999) note that MIS 11 has the longest period of relative climatic stability in the last 500 kyrs where sea surface temperature variations were limited to 1-2°C. The resolution of the LP6 isotopic record and the dating basis for the growth model do not allow strong conclusions to be... 

To facilitate preliminary comparisons, we have aligned the dated intervals of our speleothem isotopic records, plotted as distance from the base of the deposit, to the chronology of established global paleoclimatic records (from ice and marine cores) and... 

Figure 6. WFP-2L values compared to the GIPS2 and Vostok ice-core records for similar time periods. 3 -order polynomial best-fit lines are shown for the WFP-2L and Vostok isotope records. A 3-point running mean (thick line) is shown for the GISP2 record. This reduces the GISP2 record to a resolution similar to the WFP-2L s resolution (WFP-2L has 51 points while the GISP2 record has 160 points). 5 0 values are not available for the Vostok record. The speleothem isotopes are plotted relative to distance from base. Bars on the dates represent vertical sampling range and they have been lined up with the compared chronologies. One possible peak-correlation scenario is shown (dotted lines). The GISP2 data are from Grootes et al. (1993), Meese et al. (1994) and Stuiver et al. (1995). The Vostok data is from Chappellaz and Jouzel (1992).

Figure 12-4 will now be discussed in more detail. The record of reduced carbon in sedimentary rocks and the associated, 3C/I2C isotope shift date back to the oldest deposits of 3.5 Gyr ago, and even further if one makes allowance for the metamorphic alterations of the still older Isua formation (see Fig. 11-2). The biological origin of the isotope shift has been convincingly demonstrated, as reviewed by Schidlowski et al (1983). The implication that life had been in full swing 3.5 billion yr ago is supported by several lines of fossil evidence stromatolites, microfossils, and banded iron formations.

Analysis of extraterrestrial materials, and in particular meteorites, is an important focus of cosmochemical research, as such samples preserve chemical and isotopic records of early solar system conditions and processes. The first studies of meteorites, which recognized that such samples have an extraterrestrial origin, date back to the late eighteenth century [3], but modem research in cosmochemistry has a much more recent origin. This is traced back by many to the founder of contemporary geochemistry, V.M. Goldschmidt, as he produced early, but well-founded, compilations of cosmic element abundances, based on data acquired for meteorites [4, 5]. Goldschmidt s work was later continued and extended by Suess in collaboration with Urey and their study on the abundances of the elements [5] is still an important milestone in cosmochemistry. 

Some short-lived radionuclides were sufficiently abundant at the start of the solar system to produce variations in the abundance of their daughter isotopes in early-formed objects (Table 10.2). The half-lives of these nuclides are between about 0.1 and 100 Ma (Table 10.2). Hence, the parent isotopes are no longer present today, but they were synthesized in stars shortly before solar system formation and therefore they were present in the early solar nebula. The isotopic record of these nuclides provides information about stellar nucleosynthetic sites active shortly before the birth of the solar system and the time scales over which the early solar system formed and first differentiated. Depending on half-life and chemical affinities of parent and daughter isotopes, extinct radionuclide systems can be used to date processes as diverse as the formation of CAIs and chondrules, volatile element depletion and planetary difierentiation (e.g., core segregation and differentiation of early silicate reservoirs). In particular, they are powerful tools to study the Earth s accretion and core formation [90-92],... 

Record the contents of each waste container. Each radioactive waste container must have a record of the identity of radioisotope(s), the activity, and the date (see Figure 13.6). For short-lived isotopes, the date should be the date of assay of the activity, which should be very close to the disposal date. 

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