Nontectonic influences on continental basin-fill sedimenta- tion and post-orogenic sedimentation in a late Cenozoic Extensional Basin

该项目将评估亚利桑那州东南部上新世-早更新世圣大卫组的沉积学和地层学。圣大卫组是在山脉锋面和谷底之间的相对运动几乎停止后沉积在盆地和山脉山谷中的。这种环境使得在盆地边缘没有活动变形的情况下，可以研究盆地的沉积特征。初步研究表明，该层序厚度约为150 m，具有相当大的垂向和横向变异性。在没有活动构造作用的情况下，沉积样式的时间变化必然是由气候变化和与区域流域一体化相关的流域格局演变引起的。其中一些变化初步与海洋古气候记录相关联。这个项目代表了第一次共同努力来评估一个主要是前第四纪大陆盆地-填充单元的沉积学，强调气候和古地貌变化，而不是构造作用，以产生沉积物粒度和相分布的时空变化。研究结果将用于：a)表征晚期盆地沉积的性质；b)评估目前有关地层变化的假设的有效性，先验的，幕式构造作用；c)尝试将上新世-早更新世非冰期大陆记录与海洋古气候记录进行对比。

The project will evaluate the sedimentology and stratigraphy of the Pliocene-early Pleistocene St. David Formation in southeastern Arizona. The St. David Formation was deposited in a Basin and Range valley after near cessation of relative motion between range fronts and valley floor. This setting allows for examination of the characteristics of basin sedimentation in the absence of active deformation along the basin margins. Preliminary study reveals an approximately 150 m thick coarsening-upward sequence with considerable vertical and lateral variability. In the absence of active tectonism, temporal changes in depositional style must be caused by climatic changes and evolving drainage patterns related to regional drainage integration. Some of these changes are tentatively correlated to marine paleoclimatic records. This project represents the first concerted effort to evaluate the sedimentology of a largely pre- Quaternary continental basin-fill unit with emphasis on climate and paleogeomorphological changes, rather than tectonism, to produce temporal and spatial variations in sediment grain size and facies distribution. The results will be used to a) charactertize the nature of late-stage basin sedimentation, b) evaluate the validity of current hypotheses relating stratigraphic variation, apriori, to episodic tectonism, and c) attempt correlation of a Pliocene-early Pleistocene nonglacial continental record to marine paleoclimatic records.