Deep groundwater samples from the Continental Intercalaire CI aquifer in the Northern Tunisian Sahara have been analyzed for noble gases 3 He, 4 He, Ne and 81 Kr, and for 14 C to better constrain the groundwater residence time of this large transboundary aquifer. Its significant radiogenic 4 He content and background-level 14 C both indicate water older than a few tens of thousands of years. Here, this study exemplifies the utility of 81 Kr not only as an independent and conservative chronometer, but also as a supplemental measurement to better calibrate the parameters required for other age tracers, including cosmogenic 36 Cl and radiogenic 4 He. GOV collections:. This content will become publicly available on January 28, Title: Krypton dating of the deep Continental Intercalaire aquifer with implications for chlorine dating. Full Record Other Related Research. Abstract Deep groundwater samples from the Continental Intercalaire CI aquifer in the Northern Tunisian Sahara have been analyzed for noble gases 3 He, 4 He, Ne and 81 Kr, and for 14 C to better constrain the groundwater residence time of this large transboundary aquifer.
Cosmogenic Isotope Dating
Thank you for visiting nature. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser or turn off compatibility mode in Internet Explorer.
Chlorine (36Cl) cosmogenic surface exposure dating of five boul- ders of the rock avalanche deposit indicates a mean event age of +.
Jump to navigation. Science Support Program. Search form Search. Chlorine Chlorine In situ cosmogenic 36 Cl is produced by interaction of cosmic rays with different target elements, mainly calcium, potassium and chlorine 35 Cl. We try to avoid rocks with high chlorine concentrations because of the complex 36 Cl production mechanism from chlorine, and we therefore focus on mineral separates rather than whole silicate rocks. Using isotope dilution see Fig.
To extract 36 Cl from silicate minerals we follow the method developed by Irene Schimmelpfennig during her PhD work , which is inspired by the procedure set up by John Stone at the University of Washington Stone et al. It consists of spiking the thoroughly leached sample with an either 35 Cl-enriched or 37 Cl-enriched NaCl spike; dissolving the sample; precipitating silver chloride a first time; cleaning the re-dissolved sample from sulfur; precipitating silver chloride a second time.
Help Contact us. Rudolph, Elizabeth M. Quaternary Science Reviews , ,
Abstract. We apply cosmogenic-nuclide burial dating using the 36Cl-in-K-feldspar/10Be-in-quartz pair in fluvially trans- ported granitoid clasts.
Detailed mapping of dolerite slope deposits overlying sedimentary Triassic rocks on the northern slopes of the Nicholas Range in northeastern Tasmania has revealed an extensive mass movement complex. Exposure dates were obtained for three large boulders collapsed dolerite columns from a ridge within the ripple landscape. The two youngest dates gave a mean age of This is the estimated age for collapse of the dated columns from the cliff face c.
Boulder ages and landscape morphology indicate that the ripple landscape developed by physical and chemical degradation and concurrent northern displacement of topples over a slip plane formed at the contact between dolerite colluvium and underlying Triassic sedimentary rocks. There is no evidence of movement today, other than localised debris flows associated with knickpoints in streams, and it is deduced that movement on the slip plane occurred under a cooler climate than that prevailing today, possibly under the influence of melting of winter snow during the last glacial cycle.
As there is no evidence of significant recent mass movement and forests in the area are likely to have experienced many stand-destroying forest fires in the Holocene, forest harvest is not considered to pose a risk to landscape stability. This is a preview of subscription content, log in to check access.
Cosmogenic nuclide dating
Cosmogenic 36 Cl ages were determined on 11 glacial erratics from the summits of Porcupine Hills and Cloudy Ridge, Waterton valley, and the Foothills south of Cardston, Alberta. They were laid down by 1 the most extensive advance of a Canadian Shield centred continental ice sheet into this region stratigraphically oldest glacial deposits ; 2 a montane glacial advance from the Waterton valley stratigraphically intermediate glacial deposits ; and 3 an advance of continental glacial ice that overrode deposits of the intermediate-age montane advance.
Zero erosion rate 36 Cl ages of the erratics, uncorrected for snow cover, range between about 12 and 18 ka. They support the hypothesis that the Laurentide Ice Sheet reached farther into the southwestern Foothills than did all the previous continental ice sheets. Laurence D. Advanced Search.
Abstract. Over the past 20 years, analyzing the abundance of the isotope chlorine (36Cl) has emerged as a popular tool for geologic dating.
Rock Avalanches View all 11 Articles. Rock avalanches are low frequency natural hazards that can alter landscape morphology, and constraining the timing, volume and emplacement dynamics of pre-historic rock avalanches is crucial for understanding the hazards posed by these events. Here we perform cosmogenic nuclide dating, topographic reconstruction and runout modeling of the Molveno rock avalanche, located north of Lake Garda in the Province of Trento, Italy.
The unique morphology of the deposits, which features numerous large scarps and prominent lineaments, have previously led researchers to interpret the Molveno rock avalanche as being the result of multiple events. Our results show that the Molveno rock avalanche had a volume of approximately Mm 3 , and failed from a prominent niche located on Monte Soran.
Numerical runout modeling shows that this morphology could have resulted from a combination of runup and extensional spreading of the debris along the complex valley floor topography. The ages we determined for this event are coincident with the nearby Marocca Principale rock avalanche 5. Our results have important implications for interpreting the morphology of rock avalanche deposits, and contribute to the evolving understanding of rock avalanche processes in the Alps.
Large rock avalanches are rare mass movements that can dramatically alter landscape morphology. Many rock avalanches have filled valleys and created landslide dammed lakes, and these catastrophic events can be a significant hazard to people and infrastructure located in the potential runout zone Schwinner, ; Heim, ; Abele, ; Hovius et al. Detailed studies of pre-historic landslides are important to understand the risk posed by these natural hazards, and understand post-glacial slope dynamics, landscape evolution, and paleoseismicity Hovius et al.
Earthquake supercycles in Central Italy, inferred from 36Cl exposure dating
Chlorine 36 Cl is an isotope of chlorine. Chlorine has two stable isotopes and one naturally occurring radioactive isotope, the cosmogenic isotope 36 Cl. In the top meter of the lithosphere, 36 Cl is generated primarily by thermal neutron activation of 35 Cl and spallation of 39 K and 40 Ca. The half-life of this isotope makes it suitable for geologic dating in the range of 60, to 1 million years.
The principal advantage ofthe proposed dating method for permafrost studies is based on the determination of the time of 36Cl and 10Be fixationthat.
Skip to search form Skip to main content You are currently offline. Some features of the site may not work correctly. DOI: Jackson and F. Phillips and K. Shimamura and E. Jackson , F. Little Published Geology. The Foothills erratics train of Alberta was carried into place during coalescence between montane glaciers and the Laurentide ice sheet. Its age has been controversial: Late Wisconsinan and pre-Wisconsinan ages have been assigned to it.
Cosmogenic 36 Cl exposure dating was carried out on erratics over a km segment of the erratics train. Seven of eight age determinations support emplacement during the late Wisconsinan glaciation.
Permafrost is one of the most sensitive parts of the lithosphere that reacts to the climate changes. Within its horizons, geological events and climatic oscillations have been reflected in permafrost accumulation and degradation. The presented interdisciplinary project focuses on a key geocryological problem which has not been solved yet, that is, the direct determination of the permafrost age. In order to approach this problem, a method of direct permafrost dating back to 1.
The proposed dating method is based on the determination of the time of 36Cl fixation within ice i.
cosmogenic-nuclide exposure dating to glacier chronology, cosmogenic 36Cl to date moraine boulders at the Bloody Canyon.
How can we date rocks? Using cosmogenic nuclides in glacial geology Sampling strategies cosmogenic nuclide dating Difficulties in cosmogenic nuclide dating Calculating an exposure age Further Reading References Comments. Geologists taking rock samples in Antarctica for cosmogenic nuclide dating. They use a hammer and chisel to sample the upper few centimetres of the rock. Cosmogenic nuclide dating can be used to determine rates of ice-sheet thinning and recession, the ages of moraines, and the age of glacially eroded bedrock surfaces.
It is an excellent way of directly dating glaciated regions. It is particularly useful in Antarctica, because of a number of factors:. Cosmogenic nuclide dating is effective over short to long timescales 1,,, years , depending on which isotope you are dating. Different isotopes are used for different lengths of times. This long period of applicability is an added advantage of cosmogenic nuclide dating. Cosmogenic nuclide dating is effective for timescales from ,, years.
Cartoon illustrating cosmogenic nuclide exposure ages. A glacier transports an erratic boulder, and then recedes, exposing it to cosmic rays.
Dating ultra-deep mine waters with noble gases and 36Cl, Witwatersrand Basin, South Africa
Chlorine has two stable isotopes and one cosmogenic isotope. The cosmogenic isotope, 36 Cl, has a long half-life, making it useful in age dating groundwaters up to 1 million years old. There is also limited variation in 37 Cl. Most natural variation in 37 Cl values in hydrologic systems are related to diffusion processes. Origin return to top 36 Cl – Natural Production 36 Cl is produced naturally in the atmosphere and within solid materials at the earth’s surface.
The results of 81Kr dating and the recalibrated 36Cl dating define an eastward age progression across > km of flow path from the Algerian.