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By considering radioisotope dating as a problem in trace element detection, and by using the cyclotron as a high-energy mass spectrometer for this purpose, we have shown that one can greatly increase the maximum age that can be determined while simultaneously reducing the size of the sample required. The cyclotron can be used to detect atoms or simple molecules that are present at the 10(-16) level or greater. For (14)C dating one should be able to go back 40,000 to 100,000 years with 1- to 100-mg carbon samples; for (10)Be dating, 10 to 30 million years with 1-mm(3) to 10-cm(3) rock samples; for tritium dating, 160 years with a 1-liter water sample. The feasibility of the technique has been demonstrated experimentally by measuring the tritium/deuterium ratio in a sample 24 years old. For samples many half-lives old, the fractional error in the age is small even if rates of production or deposition of the isotopes. Although cyclotrons are expensive to build, their operating costs are relatively low. If several samples are dated per hour the cost per date may not be substantially higher than it is today for decay dating. There are already more than 50 cyclotrons in operation which have the potential to do radioisotope dating, and their application to important problems of dating and trace element analysis should prove very fruitful.
We propose that the approx. 100-k.y. cycle seen in terrestrial glaciation is due to changes in meteor flux that come from changes in the Earth's orbit. This model can explain a 70-k.y. 'anomalous' period in climate data and the apparent discrepancy between present extraterrestrial fluxes and those in oceanic sediments. It can be tested by measuring Ir densities in sediments and ice during glacials and interglacials.
Research Article| January 01, 1997 Simultaneous presence of orbital inclination and eccentricity in proxy climate records from Ocean Drilling Program Site 806 Richard A. Muller; Richard A. Muller 1Department of Physics, University of California, Berkeley California 94720 Search for other works by this author on: GSW Google Scholar Gordon J. MacDonald Gordon J. MacDonald 2International Institute for Applied Systems Analysis, A-2361 Laxenburg, Austria Search for other works by this author on: GSW Google Scholar Geology (1997) 25 (1): 3–6. https://doi.org/10.1130/0091-7613(1997)025<0003:SPOOIA>2.3.CO;2 Article history first online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation Richard A. Muller, Gordon J. MacDonald; Simultaneous presence of orbital inclination and eccentricity in proxy climate records from Ocean Drilling Program Site 806. Geology 1997;; 25 (1): 3–6. doi: https://doi.org/10.1130/0091-7613(1997)025<0003:SPOOIA>2.3.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Ocean Drilling Program Site 806 in the western Pacific shows evidence of a remarkably constant average sedimentation rate. This feature allows us to analyze ancient climate proxies without the need for “orbital tuning,” a standard procedure in prior work, but one that can lead to biased results. Spectral analysis of stable oxygen isotope ratios at this site, a proxy for global ice volume, shows a single narrow peak with a period ≈ 100 k.y., a result that supports our model which links glacial cycles to variations in the inclination of the Earth's orbit. In contrast, spectral analysis of the coarse component fraction of the sediment (primarily foraminifera) shows a structure characteristic of standard Milankovitch theory, with a triplet of peaks with periods near those expected from the Earth's eccentricity: 95, 125, and 400 k.y. Bispectral analysis confirms these linkages but suggests that orbital inclination also plays some role in the coarse fraction. From the clear presence of both signals in different proxies at the same site, we conclude that although eccentricity affected the local climate, it is orbital inclination that drove the variations in the global ice volume for the past million years. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.
Atmospherically induced phase perturbations have for years limited the resolution of large optical astronomical telescopes. A prototype telescope system with six movable elements has successfully corrected these phase perturbations. This use of real-time image sharpening has restored stellar images to the diffraction limit (in one dimension) for a 30-centimeter telescope. The double-star image presented indicates that the bulk of the atmospherically induced wave-front phase change occurred within 2 kilometers of the telescope. This implies that, at least for conditions similar to those of our measurement, real-time correction can be accomplished simultaneously for a region at least several arc seconds in angular size. With the present apparatus the technique should be practical for objects as dim as fifth magnitude, and with improvements the technique holds the promise of active image restoration for objects as dim as ninth magnitude.
Research Article| September 01, 1997 Simultaneous presence of orbital inclination and eccentricity in proxy climate records from Ocean Drilling Program Site 806: Comment and Reply Michael Schulz; Michael Schulz 1Universität Kiel, Sonderforschungsbereich 313, Heinrich-Hecht-Platz 10, D-24118 Kiel, Germany Search for other works by this author on: GSW Google Scholar Manfred Mudelsee; Manfred Mudelsee 2Universität Kiel, Geologisch-Paläontologisches Institut, Olshausenstrasse 40, D-24118 Kiel, Germany Search for other works by this author on: GSW Google Scholar Richard A. Muller; Richard A. Muller 3Department of Physics and Lawrence Berkeley Laboratory, University of California, Berkeley California Search for other works by this author on: GSW Google Scholar Gordon F. MacDonald Gordon F. MacDonald 4International Institute for Applied Systems Analysis, A-2361 Laxenburg, Austria Search for other works by this author on: GSW Google Scholar Author and Article Information Michael Schulz 1Universität Kiel, Sonderforschungsbereich 313, Heinrich-Hecht-Platz 10, D-24118 Kiel, Germany Manfred Mudelsee 2Universität Kiel, Geologisch-Paläontologisches Institut, Olshausenstrasse 40, D-24118 Kiel, Germany Richard A. Muller 3Department of Physics and Lawrence Berkeley Laboratory, University of California, Berkeley California Gordon F. MacDonald 4International Institute for Applied Systems Analysis, A-2361 Laxenburg, Austria Publisher: Geological Society of America First Online: 02 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (1997) 25 (9): 860–862. https://doi.org/10.1130/0091-7613(1997)025<0860:SPOOIA>2.3.CO;2 Article history First Online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Michael Schulz, Manfred Mudelsee, Richard A. Muller, Gordon F. MacDonald; Simultaneous presence of orbital inclination and eccentricity in proxy climate records from Ocean Drilling Program Site 806: Comment and Reply. Geology 1997;; 25 (9): 860–862. doi: https://doi.org/10.1130/0091-7613(1997)025<0860:SPOOIA>2.3.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract No Abstract Available. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.
Introduction.- The prevailing paradigm.- Details of the data and their interpretation.- Astronomical effects.- Time scale determination - a critical problem.- Tuning.- Spectral Methods: the minimum you must know.- Spectral analysis of data.- The 23 kyr cycle - does it exist?- Linking mechanisms to climate.- Critical tests of theory.- Summary: Status of our understanding. Appendices
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