A Late Pleistocene-Holocene lacustrine record from Lake Manas, Zunggar (northern Xinjiang, western China)
(Palaeogeography, Palaeoclimatology, Palaeoecology. vol. 120, n° 0031-0182, pp. 105-121, 01/02/1996)
CEREGE, IRD, INRA, AMU, CdF (institution), INSU - CNRS, CNRS, UP11, CAS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IDES, UP11, INSU - CNRS, CNRS, MNHN, UP11
Hydrographic changes of the Southern Ocean (southeast Indian Sector) Over the last 230 kyr
(Paleoceanography. vol. 11, n° 0883-8305, pp. 57-76, 01/02/1996)
CFR, CEA, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Morphogenèse, paysage et peuplement en Aquitaine
(07/04/1996)
ArScAn, UP1, UP8, UPN, MCC, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Lacustrine organic fluxes and palaeoclimatic variations during the last 15 ka: Lac du bouchet (Massif Central, France)
To assess the influence of climatic changes on organic lacustrine sedimentation, two cores recovered from the centre of the Lac du Bouchet were studied by petrographical (palynofacies) and geochemical methods. Only core LDB H was used for estimation of the organic fluxes. The variation of these fluxes with climo-stratigraphic periods showed: low organic fluxes during the Lateglacial, an increase at the beginning of the Holocene, a minimum at the end of the Atlantic period resulting from the climatic cooling, and a maximum at the end of the Sub-Boreal related to the installation of the present climatic conditions.
(Quaternary Science Reviews. vol. 15, n° 0277-3791, pp. 203-211, 07/04/1996)
PALEOTROPIQUE, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, ISTO, INSU - CNRS, UO, CNRS
Experimental evidence of complex interactions between biotic and abiotic factors in the dynamics of an intertidal population of the bivalve Cerastoderma edule.
Densities of the suspension-feeding bivalve Cerastoderma edule (L.) were manipulated inside field enclosures at two tidal elevations (low water level, LWL, and mid-tide level, MTL) on an intertidal sand flat in Arcachon Bay to test the influence of both adult densities and emersion time on (1) individual growth rate, (2) settlement rate, and (3) survival rate of cockles. These experiments were conducted during two consecutive years, in plots with ambient (Ix) and modified (1/3x, 3x, or 10x) densities of adult cockles. Growth rate and condition index of both adults and juveniles were significantly higher at the lowest tidal elevation (LWL), which is in accordance with the feeding mode of the species. The highest juvenile growth rate was recorded in the low-density treatments (160-200 adults m(-2)), which suggests a competitive interaction with adults; for the latter, growth rate was depressed only at the highest density (2000 m(-2)). survival of-adults was affected neither by immersion time nor by densities. Contrasted results were found for the settlement rate and the survival of recruits. During the first year of-experiment, density-treatments had no effect on settlement at MTL, whereas high adult densities negatively influenced settlement at LWL, but only during the period of high settlement; during the second year, a significant effect of-adult densities on settlement was found on a single occasion at MTL. However, at the end of-both experiments (195 and 252 d, respectively), recruit densities did not significantly differ between density-treatments. Although the difference in tidal elevation between the two experimental sites was only 1.0 m, settlement peaks were clearly distinct: they occurred in April (approximate to 4000 m(-2)) at LWL but not earlier than July (approximate to 12000 m(-2)) at MTL; however, the final recruitment was higher at LWL than at MTL. Preliminary results of a laboratory flume study show that, in conditions of smooth turbulent flow (u* = 0.51 cm s(-1), Re* = 1.8), juvenile cockles are able to leave the substratum, to migrate by byssus drifting into the water column over several metres and to avoid resettlement in areas with high densities of conspecific adults. Although competition with adults may occur during larval settlement, subsequent migration of juveniles between different tidal levels is likely to affect significantly the growth and recruitment of intertidal cockle populations.
(Oceanologica Acta, n° 0399-1784, 07/04/1996)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Morphologie, paysages et occupations du sol entre Atlantique et Gironde aux époques historiques
(pp. p. 206-211, 07/04/1996)
ArScAn, UP1, UP8, UPN, MCC, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Le Quaternaire littoral girondin.
Nous présentons la situation géographique, l'histoire géologique, les traces d'occupations humaines, l'histoire contemporaine et le vin en Médoc.
(07/04/1996)
PACEA, UB, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
A comparison of the Vostok ice deuterium record and series from Southern Ocean core MD 88-770 over the last two glacial-interglacial cycles
Taking advantage of the fact that the Vostok deuterium (δD) record now covers almost two entire climatic cycles, we have applied the orbital tuning approach to derive an age-depth relation for the Vostok ice core, which is consistent with the SPECMAP marine time scale. A second age-depth relation for Vostok was obtained by correlating the ice isotope content with estimates of sea surface temperature from Southern Ocean core MD 88-770. Both methods lead to a close correspondence between Vostok and MD 88-770 time series. However, the coherence between the correlated δD and insolation is much lower than between the orbitally tuned 8D and insolation. This reflects the lower accuracy of the correlation method with respect to direct orbital tuning. We compared the ice and marine records, set in a common temporal framework, in the time and frequency domains. Our results indicate that changes in the Antarctic air temperature quite clearly lead variations in global ice volume in the obliquity and precession frequency bands. Moreover, the average phase we estimated between the filtered δD and insolation signals at precessional frequencies indicates that variations in the southern high latitude surface temperature could be induced by changes in insolation taking place during a large period of the summer in northern low latitudes or winter in southern low latitudes. The relatively large lag found between Vostok δD variations and obliquity-driven changes in insolation suggests that variations in the local radiative balance are not the only mechanism responsible for the variability in surface temperature at those frequencies. Finally, in contrast to the cross-spectral analysis method used in previous studies, the method we use here to estimate the phases can reveal errors in cross-correlations with orbitally tuned chronologies.
(Climate Dynamics. vol. 12, n° 0930-7575, pp. 113-123, 01/12/1995)
LMCE, CFR, CEA, CNRS, LGGE, OSUG, UJF, Grenoble INP, INSU - CNRS, IRSTEA, USMB [Université de Savoie] [Université de Chambéry], CNRS, INSU - CNRS, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, AARI, Roshydromet
Could deep subantarctic convection feed the world deep basins during the Last Glacial Maximum?
Simple box model calculations are used to simulate the oceanic circulation during the last glacial maximum (LGM). These experiments show that the main features of the 1513C and A14C distributions and of the lysocline depth may be explained by a circulation pattern very different from the modem one. Intermediate and upper deep waters were produced in the North Atlantic Ocean, whereas deep waters of Subantarctic Mode type, forming at the northern edge of the Subantarctic convergence, invaded the main oceanic basins. The Southern Ocean, mainly self ventilated, had a reduced deep component that flew southward along the East Pacific Ridge and the Australian west cost. The thermodynamic fractionation that occurs during air-sea exchange has only contributed slightly to the glacial deep 1513C distribution through surface water temperature variations.
(Paleoceanography. vol. 10, n° 0883-8305, pp. 927-941, 01/10/1995)
CFR, CEA, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Pollen analyses off Senegal: Evolution of the coastal palaeoenvironment during the last deglaciation
Not Available
(Journal of Quaternary Science. vol. 10, n° 0267-8179, pp. 95-105, 01/06/1995)
BTP, LOCEAN, IPSL, ENS-PSL, UVSQ, UPMC, CEA, INSU - CNRS, X, CNES, CNRS, MNHN, IRD, UPMC, INSU - CNRS, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, CEREGE, IRD, INRA, AMU, CdF (institution), INSU - CNRS, CNRS