U.S.-Australia Cooperative Research: Southeastern Australian Test of the Role of Eustasy in Development of Small-Scale Upper Devonian Cycles

该奖项将支持巴克内尔大学的爱德华·科特博士和澳大利亚麦格理大学的帕特里克·科纳汉博士之间的合作研究。这项拟议的研究将试图确定晚泥盆世期间全球是否经历了小范围(五级或六级)海平面波动，从而引发了关于北美和欧洲的这种海平面波动是由海平面上升(全球范围)还是更局部的构造作用引起的争论。基本方法是研究澳大利亚东南部拉克兰褶皱带上泥盆统层序(兰比群)中的海相和边缘海相沉积序列，以确定它们是否包含一到十米厚的韵律模式，显示出周期性的深度交替变化。如果发现这种水深的韵律变化，计算这种变化的周期性将允许与北美阿巴拉契亚盆地同时代(弗兰斯-法门期)层序确定的周期性进行比较。如果澳大利亚东南部的周期以10万年左右为中心，就像北美的情况一样，这不仅将支持对周期发展的海平面控制，而且它强化了海平面与米兰科维奇类型的轨道变化有关的观点。然而，如果相对水深的小规模变化周期不在澳大利亚东南部的兰比群及其相关地区，那么就很难主张在北美控制着水深变化周期。该项目代表了新西兰小组和科特小组之间的出色合作，新西兰小组在了解构造板块相互作用产生的沉积模式方面做出了重大贡献，科特研究了晚泥盆世时期的小规模海洋波动是否为海平面上升。这是一项重要的工作，将有助于关于北美和欧洲的这种周期是由海平面上升还是更多的局部构造作用引起的辩论。

This award will support collaborative research between Dr. Edward Cotter of Bucknell University and Dr. Patrick Conaghan of Macquarie University, Australia. The proposed research will attempt to determine whether small-scale (fifth- or sixth-order) sea-level fluctations were experienced worldwide during Late Devonian time, thereby contributing to the debate concerning whether such cycles in North America and Europe were caused by eustatic (world-wide) or more local tectonic processes. The basic approach is to investigate marine and marginal-marine sedimentary sequences in the Upper Devonian succession (Lambie Group) of the Lachlan Fold Belt in southeastern Australia to determine whether they contain rhythmic patterns, one to ten meters thick, showing cyclically alternating changes of depth. If such rhythmic alternations of water depth are found, calculation of the periodicities of such changes will permit comparison with the periodicities determined for contemporaneous (Fransnian-Famennian) sequences in the Appalachian Basin of North America. Should the southeastern Australian periodicities center around 100,000 years, as is the case in North America, not only will this support a eustatic control of cycle development, but it reinforces the idea that eustasy was related to Milankovitch- type orbital variations. However, if small-scale cycles of change in relative water depth are not in the Lambie Group and its correlatives in southeastern Australia, it will be much more difficult to argue for eustasy as the control on the cycles in North America. This project represents excellent collaboration between the New Zealand group which has made major contributions to knowledge of the patterns of sedimentation that result from interaction of tectonic plates and the Cotter work on whether small-scale sea fluctuations during Late Devonian time were eustatic. This is important work which will contribute to the debate concerning whether such cycles in North America and Europe were caused by eustatic or more local tectonic processes.