Pleistocene values

Capreolus capreolus dwelling in a forest 35 km south-west of Paris have negative 6 N values, ranging from -2.8 to -0.4%o, probably because of local acidic soil conditions and the very territorial habits of this deer species (Rodiere et al. 1996). Such differences between habitats should be confirmed by further studies in modem imdisturbed ecosystems. This would provide a very useful framework for understanding sources of variation in Pleistocene species. 

Figure 4.8. 6 C and 8 N values of bone collagen from Pleistocene Alaskan mammals (-10,000 - 40.000BP) compared with those of recent Alaskan mammals. Isotopic abundances of Pleistocene mammals are from Bocherens et al. (1995a).

Figure 4.10. Differences in 6 N values between bone and dentine collagen from Pleistocene and recent mammals. Isotopic abundances are from Bocherens et al. (1994, 1995b) and this paper.

Figure 4.11. Average collagen ( c ) and carbonate hydroxylapatite ( a ) 8 C values in modem and Pleistocene herbivores, carnivores and bears. Isotopic abundances for modem samples are from this paper, those for Kent s Cavern samples are from Bocherens et al. (1995b) and those for other Pleistocene localities are from Bocherens et al. (1994).

Two possibilities for the observed enriched values for many of the grazers, and the often concomitant but slight enrichment of browsers (Fig. 5.6), present themselves. Either these shifts represent atmospheric CO2 enrichment shifts at particular periods during the last -lOOKa represented (the Late Pleistocene), or a hitherto unknown or unrecognized fractionation process has taken place during burial and fossilization. The former hypothesis could be tested by comparison of observations from a larger sample set from the site, with CO2 concentration and carbon isotope data from Antarctic ice-core records or high resolution marine isotope records. 

Table 5. Effect of Variation in Pretreatment Methods on 15N Values of Contemporary and Late Pleistocene Bone Samples9.

Foraminifera are also important in marine geochemistry studies, and Li isotopes have been measured in the shells of a variety of these organisms. The first report of this kind (You and Chan 1996) gave data for four Pleistocene samples of H obliquiloculata 5 Li = +19.3 to +23.0 for two glacial period samples and +26.6 to +42.4 for two interglacial samples (data without blank correction). The species effect interpreted by Marriott et al. (2004) in corals has also been suggested for forams. In the study of Rosier et al. (2001), core-top (i.e., Holocene)P. obliquiloculata samples yielded isotopic compositions close to modem seawater (5 Li = +27.8 to +31.1), whereas samples of G. tumida from the same samples had values of up to +50.5. 

Based on Pleistocene and younger deep sea ooze data of De La Rocha and DePaolo (2000) and DePaolo (unpublished see Fig. 11b). Zhu and MacDougall (1998) estimate this value as about —1.2 0.3. 

Let us take another example. At the U.S. Gulf Coast, the Pleistocene and the Upper Tertiary (Pliocene and Miocene) reach a thickness of more than 6000 meters. Nevertheless, the coaliflcation has only reached the stage of high volatile bituminous at this depth. This observation resulted from our studies of samples from a deep borehole located in Terrebonne Parish, La. By reflectance measurements on humic inclusions in claystones of the uppermost Middle Miocene encountered at a depth of 5440 meters, we obtained a mean value (under oil) of 0.95% reflectance, which is equivalent to the reflectance of vitrinites (out of deep boreholes) with 35-40% volatile matter (daf). On the other hand, we found low volatile bituminous coals (14-16% volatile matter, daf) at a depth of 5100 meters in a borehole in the Lower... 

Figure 7.29. A scatter plot of 813C and 8180 values of Holocene and Pleistocene carbonate sediments. Open circle, unlithified bulk Holocene sediments + s, lithified bulk Holocene sediment closed circles, Pleistocene limestones altered by meteoric water. For Pleistocene limestones altered in the meteoric environment, temperate climate samples are represented by 8180 values more enriched than -5%o, whereas tropical climate samples have 8180 values more depleted than -5%o. The large depletion in 13C is because the sediment samples are primarily from vadose environments. (After Land, 1986.)...

Fig. 2a, b a Adsorption and desorption of 1,4-DCB from Pleistocene clay (PC) soil, b Total mass of 1,4-DCB remaining on the soil as a function of both desorption time and number of steps during the desorption cycle. The open square symbol denotes the values calculated from the adsorption data... 

This type of data raises the issue of the constancy of the oceanic circulation patterns over the region in question. In this case the question is to what degree the values cited in Figure 6 could be used to estimate oceanic upwelling effects along the continental margins of the Western Hemisphere as one moves back into the early Holocene and terminal Pleistocene. Table I lists a series of paired terrestrial organics/marine... 

However, the issue of the correct half-life for radiocarbon has lost a considerable amount of its significance because of the discovery and documentation of the long- and short-term secular variation effects. The existence of dendrochronologically documented relationships between radiocarbon age and calendar age fortunately enables researchers to circumvent completely the problem of the real half-life. This will also hold true even for radiocarbon determinations on Pleistocene age materials where the use of the 5730 value increases values at, for example, 35,000 years... 

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