Collaborative Research: Nuclear Studies of Continental Erosion Processes and Rates

这是一个实验项目的延续，旨在进一步发展和应用核方法来研究地表地质过程，包括研究大陆侵蚀。该技术的基础是通过宇宙射线的核相互作用在岩石中原位产生核素。由于岩石中宇宙辐射的吸收平均自由程为- 50 cm，并且由于在大多数岩石中可以很容易地研究原位核素10Be（半衰期为1.5X106年），26Al（半衰期为0.7X106年）和14C（半衰期为5730年），因此可以在2X10-5-6X10-3 cm. year -1中最佳地表征表面变化；使用较短半衰期的核素（39Ar， 269年）和稳定的核素（3He和21Ne）分别可以获得较高和较低的速率。我们已经通过对从50个岩石样品中提取的石英中的10Be和26Al的原位研究证明了该方法的潜力。我们研究了自然环境下石英中它们的产量，也用高能粒子照射石英。我们研究了几块岩石的表面侵蚀率和暴露历史，还确定了亚利桑那州迪亚波罗峡谷陨石坑的形成时间。所进行的测量证实了我们两年前向美国国家科学基金会提出的核方法的潜力。我们现在建议再进行两年的测量，以充分发展和利用原位方法的潜力。简要地说：我们将包括石英中原位14C的研究；我们将获得有关同位素产量的进一步数据；我们将继续研究选定表面的表面侵蚀率。此外，我们还提出了核方法的一系列新应用，如研究断裂和全球砂的历史。多种原位核素的使用现在已经实现了对地表过程的革命性理解的潜力，因为它将地球表面的绝大部分开放给了数字年龄控制。

This is a continuation of an experimental program to further develop and apply a nuclear method for studies of earth- surface geologic processes, including studies of continental erosion. The technique is based on in situ production of nuclides in rocks by nuclear interaction of cosmic rays. Since the absorption mean free path of cosmic radiation is - 50 cm in rocks, and since in situ nuclides, 10Be (half-life, 1.5X106 yrs), 26Al (half-life, 0.7X106 yrs) and 14C (half-life, 5730 yrs) can easily be studied in most rocks, one can optimally characterize surficial changes in the bracket 2X10-5-6X10-3 cm.yr-1; higher and lower rates are accessible using shorter half-life nuclides (39Ar, half-life 269 yrs) and stable nuclides, 3He and 21Ne respectively. We have already demonstrated the potential of the method based on studies of in situ 10Be and 26Al in quartz extracted from some 50 rock samples. We have studied their production rates in quartz in natural settings, and also by irradiating quartz with high energy particles. And we have studied surface erosion rates and exposure histories of several rocks, and also determined the time of formation of the Canyon Diablo meteorite crater in Arizona. The measurements carried out have established the potential of the nuclear method proposed 2 years ago by us to NSF. We now propose to continue our measurements for another period of 2 years to fully develop and to exploit the potentials of the in situ method. Briefly: we will include studies of in situ 14C in quartz; we will obtain further data on isotope production rates; we will continue studies of surficial erosional rates of selected surfaces. In addition, we proposal a set of new applications of the nuclear method, e.g. studying faulting and history of global sands. The use of multiple in situ nuclides has the now realized potential to revolutionize the understanding of surficial processes by opening up the vast majority of earth's surface to the numerical age control.