Collaborative Research: High-Resolution Calibration of the Maastrichtian to Paleocene of the Western U. S.: Integration of Geochronology, Magnetostratigraphy and Paleontology

在7000万至5500万年前(白垩纪和古新世末期)，地球属于温室气候，经历了巨大的变化，包括海平面下降、洪水玄武岩(德干圈闭)的大规模喷发、恐龙的灭绝(K-T边界)、拉拉米德造山运动、哺乳动物的爆炸性辐射以及被称为古新世-始新世最高温度(PETM)的全球快速变暖的重大事件。这一时期的古气候记录为理解建立、维持和摆脱温室气候的机制、海洋和陆地环境之间的关系以及当前和未来气候变化的各个方面提供了宝贵的背景。这项研究的目标是根据落基山脉地区几个盆地的一系列陆地岩石序列，为这一关键的1500万年间隔开发一个高分辨率的时间框架。落基山脉地区白垩纪和古新世岩石包含丰富的气候波动记录，世界上最好和采样最多的陆地生物记录(特别是植物和哺乳动物化石)，以及适合于磁性地层学和年代学的广泛暴露。我们的方法将结合生物地层学(记录化石生物体的地层演替)、磁性地层学(测量地球磁场的反转)和地质年代学(使用铀到锆石晶体中的铅的放射性衰变来确定层间火山灰层的年代)。在某些情况下，我们将直接确定磁极反转的边界的日期。总而言之，这些技术将使我们能够评估保存在海洋和湖泊沉积岩中的沉积旋回是否受到地球轨道动力学以及与太阳系其他行星的相互作用的控制。尽管讨论很多，但这项测试从未对这个年代的岩石进行过。该项目将导致地质时间尺度的极高分辨率增强，这将完善世界范围内的时间相关性。例如，最近由磁性地层学和生物地层学确定年代的深海岩心研究记录了来自遥远海洋盆地的高分辨率生物、海洋温度和气候记录。通过将这些记录与我们研究区陆地岩石的高分辨率年代学联系起来，我们希望为更好地理解温室气候动力学和相关的陆地事件提供一个框架。

Between 70 and 55 million years ago (latest Cretaceous & Paleocene), the earth had a greenhouse climate and underwent massive changes that included a drop in sea level, massive eruptions of flood basalt (Deccan Traps), the extinction of the dinosaurs (K-T boundary), the Laramide orogeny, the explosive radiation of mammals, and a major episode of rapid global warming known as the Paleocene-Eocene Thermal Maximum (PETM). The paleoclimatic record of this time provides an invaluable context for understanding the mechanisms for establishing, maintaining, and escape from greenhouse climates, the relationships between marine and terrestrial environments, and aspects of current and future climate change. The goal of this research is to develop a high-resolution temporal framework for this critical 15-million-year interval based on a series of terrestrial rock sequences from several basins in the Rocky Mountain Region. Cretaceous and Paleocene rocks of the Rocky Mountain region contain a rich record of climatic fluctuations, the best and most sampled terrestrial biotic record in the world (especially fossil plants and mammals), and extensive exposures suitable for magnetostratigraphy and geochronology. Our approach will integrate biostratigraphy (documenting the stratigraphic succession of fossil organisms), magnetostratigraphy (measuring reversals in the earth's magnetic field), and geochronology (dating interlayered volcanic ash beds using the radioactive decay of uranium to lead in zircon crystals). In several cases, we will directly date the boundaries of magnetic polarity reversals. Together, these techniques will allow us to evaluate whether sedimentary cycles preserved in marine and lacustrine sedimentary rocks are controlled by earth's orbital dynamics and interactions with the other planets in the solar system. Though much discussed, this test has never been performed for rocks of this age. The project will result in very high-resolution enhancement of the geologic time scale that will refine temporal correlation worldwide. For example, recent deep-sea core studies dated by magnetostratigraphy and biostratigraphy have documented high-resolution biotic, ocean temperature and climate records from far-flung ocean basins. By linking these records with high-resolution geochronology of the terrestrial rocks in our study area, we hope to provide a framework for better understanding of greenhouse climate dynamics and related terrestrial events.