(GRGC) Coll Res: Paleofloral and Stratigraphic Analysis and Eocene-Oligocene Climate Change in a Single Continental Section in North-Central Oregon

9506727曼彻斯特始新世-渐新世界线附近的气候变化是显生宙最显著的环境变化之一。这种地质上突然的全球变冷的性质，以及对其原因的假设，很大程度上来自对连续的海洋地层记录的研究。为了了解全球气候变化的动态，有必要更好地了解大陆早渐新世气候恶化的性质。到目前为止，对北美当时气候变化的解释一直是基于零散的、在某些情况下年代不佳的古植物群。因此，这些对气候敏感的植物群的年龄关系以及它们之间的差异在多大程度上代表了真实的时间变化，而不是海拔和其他环境参数在不同花区之间的变化，仍然是含糊不清的。我们将研究保存在俄勒冈州中北部单一地层序列中的化石植物群序列，那里的勘测工作表明，那里记录了整个气候变化。对这些植物群的详细收集、研究和解释将得到地质测绘、沉积学和地层学研究的补充，以确保包含化石的地层的地层格架，以及围绕植物群的地层所代表的沉积环境(因此是环境或挖掘学偏见)。古植物群赋存于火山碎屑沉积物中，夹层有凝灰岩和熔岩流，将用40Ar/39Ar方法测定年代，以限制俄勒冈州中部气候驱动的植物群变化的年代学。

9506727 Manchester Climate change near the Eocene-Oligocene boundary was one of the most significant environmental changes of the Phanerozoic. The nature of this geologically abrupt global cooling, and hypotheses for its cause, have come largely from study of continuous marine stratigraphic records. In order to understand the dynamics of global climate change, it is essential to better understand the nature of the early Oligocene climatic deterioration on continents. To date, the interpretation of climate change at the time in North America has been based on scattered, and in some cases poorly dated, paleo-floras. Ambiguities remain, therefore, on age relationships of these climatically-sensitive floras and the extent to which differences between them represent true temporal change rather than variations in altitude and other environmental parameters between floral sites. We will study a sequence of fossil floras preserved in a single stratigraphic sequence, in north-central Oregon, where reconnaissance work suggests a record of the entire climate change. Detailed collection, study, and interpretation of these floras will be complemented by geologic mapping, sedimentological, and stratigraphic study to assure the stratigraphic framework of strata containing the fossils and the depositional environments (and thus environmental or taphonomic biases) represented by beds enclosing the floras. The paleofloras are hosted in volcaniclastic sediment interlayered with tuffs and lava flows that will be dated by 40Ar/39Ar method in order to constrain the chronology of the climatically- driven floral change in central Oregon.