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

点击翻译按钮获取中文摘要

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.