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Goal – The reconstruction of past topographies remains challenging and only a few methods allow accurate determination of past surface elevations. We propose here a new technique for deriving paleo-elevations, in which multiple cosmogenic nuclides are measured in the same geological sample exposed at the Earth's surface. This method relies on the altitude dependence of the cosmogenic nuclides' production rates combined with the radioactive decays of nuclides with different half-lives. Theory – The position of the two cosmogenic nuclide exposure curves ( 26 Al/ 10 Be vs 10 Be or 10 Be/ 21 Ne vs 10 Be) depends on the altitude of exposure. If the studied surfaces have been exposed for sufficiently long durations (>500 ka), or have been affected by low erosion rates (500 ka), or low erosion rates (, SCOPUS: ar.j, info:eu-repo/semantics/published

The 176Lu–176Hf isotopic system is widely used for dating and tracing cosmochemical and geological processes, but still suffers from two uncertainties. First, Lu–Hf isochrons for some early Solar System materials have excess slope of unknown origin that should not be expected for meteorites with ages precisely determined with other isotopic chronometers. This observation translates to an apparent Lu decay constant higher than the one calculated by comparing ages obtained with various dating methods on terrestrial samples. Second, unlike the well constrained Sm/Nd value (to within 2%) for the chondritic uniform reservoir (CHUR), the Lu/Hf ratios in chondrites vary up to 18% when considering all chondrites, adding uncertainty to the Lu/Hf CHUR value. In order to better understand the Lu–Hf systematics of chondrites, we analyzed mineral fractions from the Richardton H5 chondrite to construct an internal Lu–Hf isochron, and set up a numerical model to investigate the effect of preferential diffusion of Lu compared to Hf from phosphate, the phase with the highest Lu–Hf ratio in chondrites, to other minerals. The isochron yields an age of 4647±210 million years (Myr) using the accepted 176Lu decay constant of 1.867±0.008×10−11yr−1. Combining this study with the phosphate fractions measured in a previous study yields a slope of 0.08855±0.00072, translating to a 176Lu decay constant of 1.862±0.016×10−11yr−1 using the Pb–Pb age previously obtained, in agreement with the accepted value. The large variation of the Lu/Hf phosphates combined with observations in the present study identify phosphates as the key in perturbing Lu–Hf dating and generating the isochron slope discrepancy. This is critical as apatite has substantially higher diffusion rates of rare earth elements than most silicate minerals that comprise stony meteorites. Results of numerical modeling depending of temperature peak, size of the grains and duration of the metamorphic event, show that diffusion processes in phosphate can produce an apparently older Lu–Hf isochron, while this effect will remain negligible in perturbing the Sm–Nd chronology. Our results suggest that only type 3 chondrites with the lowest metamorphic grade and large minerals with minimal diffusive effects are suitable for determination of the Lu–Hf CHUR values and the Lu decay constant respectively., SCOPUS: ar.j, info:eu-repo/semantics/published

Rubidium at a concentration of between ∼0.5 and ∼3 ppm has been determined in rocks and minerals by atomic absorption spectrophotometry. By comparison with external standards a precision of better than 3% has been attained without recourse to chemical separation of rubidium. Lanthanum and potassium buffers were added to the standards and samples to compensate for interferences. Very favourable agreement was obtained between the concentration of rubidium as determined by atomic absorption when compared to measurements made by stable isotope dilution analysis. © 1967., SCOPUS: ar.j, info:eu-repo/semantics/published

210Pb and 90Sr measurements were carried out on firn and ice samples from the Kesselwandferner (Austrian Alps). 90Sr seems to be selectively lost in the firn with respect to the other fission products and to 210Pb. The distribution of the 210Pb 'ages' of the ice samples follows a consistent pattern and is in general agreement with surface velocity measurements. © 1967., SCOPUS: ar.j, info:eu-repo/semantics/published

Sodium, magnesium, potassium, calcium, iron, manganese and nickel were measured in firn samples from Base Roi Baudouin (BRB, 70°S, 24°E), Amundsen-Scott Station (ASS, 90°S) and Plateau Station (PLA, 79°S, 40°E). The rates of snow accumulation at the three stations are respectively, in g.cm-2.yr-1 :40, 6 and 2.8. The analyses were carried out by neutron activation, atomic absorption and isotope dilution. In most cases, Fe, Mn, Ni were measured simultaneously by two or three methods on aliquots of the same sample. The corrections for contamination never exceeded 10%. Average concentrations found at BRB (5 samples, 14 kg total) and at PLA (4 samples, 32 kg) respectively are as follows, in p.p.b. Na 250-30; Mg 29-5; K 29-5; Ca 17-8; Mn 0.1-0.35; Fe 6-7; Ni 0.36-0.08. At AAS (2 samples, 3 kg) :Na 9; Mn 0.2; Ni 0.1. On account of the everpresent possibility of contamination, these values must be considered as upper limits. The following conclusions are drawn from the results: 1. 1), SCOPUS: ar.j, info:eu-repo/semantics/published

The 210Pb dating method is applied to deep thermally recovered firn-ice cores from the North Greenland ice sheet. The 210Pb activity is found to decay exponentially with depth (expressed in water equivalent). The corresponding rate of snow accumulation, averaged over the past 150 years, is (32±3) g/cm 2-yr, in good agreement with present day surface snow accumulation obtained by different methods. © 1966., SCOPUS: ar.j, info:eu-repo/semantics/published

Climatological records from the Amundsen-Scott Station, South Pole, show the summer 1957-1958 to be characterized by periods of exceptionally warm air temperature and above normal snow accumulation. The firn layer deposited during this summer displays an exceptionally high oxygen-18 content, as revealed by 18O/16O ratio profiles obtained by Epstein et al. [6,7] and by us in five pits dug along-side accumulation stakes. © 1966., SCOPUS: ar.j, info:eu-repo/semantics/published

A procedure is described for measuring 210Po in the range of 10-13Ci in water and ice samples. 208Po is used as a tracer in order to check the recovery yield. This procedure is of special interest for dating firn cores by the 210Pb method. It is applied here for the measurement of the snow accumulation rate at the Pole of Relative Inaccessibility (82°07′S, 55°06′E). © 1966., SCOPUS: ar.j, info:eu-repo/semantics/published