Collaborative Research: Paleobiology, Paleoceanography, and Paleoclimatology of a Time Slice through the Late Cretaceous Western Interior Seaway

合作研究：白垩纪晚期西部内陆航道时间切片的古生物学、古海洋学和古气候学

• 批准号: 0309449
• 负责人: Peter Harries
• 金额: $ 4.51万
• 依托单位: University of South Florida
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-09-01 至 2006-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0309449&HistoricalAwards=false
• 关键词: Collaborative; Research; Paleobiology; Paleoceanography; Paleoclimatology

ABSTRACTThis multidisciplinary study proposes using O, C, and Sr isotopic analyses of pristine mollusks found within a single interval delineated by the Late Campanian Baculites compressus biozone (74 MA; Late Cretaceous) from the Western Interior Seaway (WIS) to examine four over-arching hypotheses which exploit the strengths of the PIs and consultant. These are:1. Geochemical analyses taken through the ontogeny of individual specimens - sclerochronology (sensu Jones, 1983) - provides annual to subdecadal records of environmental conditions (e.g., seasonal temperature fluctuations, water-mass dynamics) that are critical to understand the dynamics of Late Cretaceous epicontinental seas.2. Growth rates and other paleobiologic aspects of Late Campanian organisms, such as migration patterns, can be established using the sclerochronologic approach.3. The biota, especially molluscan elements, occupied different niches within the water column and on/in the substrate and the signals of these various habitats are captured in their isotopic signatures.4. Significant environmental gradients existed in the WIS, forced by differences in temperature and salinity, and can be measured and differentiated using oxygen and strontium isotopes from well-preserved molluscan shells. In addition to addressing our general hypotheses, the isotopic data will allow us to critically analyze a range of competing paleoceanographic, paleobiologic, and paleoclimatic hypotheses that have been proposed for the Late Cretaceous world. These include: circulation patterns within the WIS, stratification of the WIS, habitat ranges and depths of individual ammonite taxa, growth rates of Cretaceous molluscs, as well as seasonal fluctuations in marine temperatures. In order to address the questions posited above, we propose to undertake a detailed investigation of a single time interval through the Late Cretaceous in the very fossiliferous PIerre Shale focused on the B. compressus biozone. Deposition during this biozone was widespread in the WIS and was often accompanied by exquisite preservation of the fauna, including aragonitic elements, within early diagenetic concretions. To collect the necessary specimens, we will sample localities in central Colorado, central and western South Dakota, and western to eastern Montana that represent north-south and onshore-offshore transects. We will measure detailed sections at all localities and collect concretions containing diverse molluscan fauna. Before any isotopic analysis is undertaken, all specimens will be screened for any evidence of diagenesis using microscopic as well as geochemical techniques. Those specimens that pass the diagenetic screening will then be analyzed for d13C and d 18O to establish their sclerochronologies. Because the value of the aqueous environment in which the shell material was secreted is critical to deriving accurate estimates of temperature and salinity, we also propose to analyze a subset of our samples for their Sr isotopic ratio. Recent studies have shown that in areas, such as estuaries, where freshwater input is an important component in the system, that 87 Sr/86 Sr dominantly reflects the salinity rather than geologic age and our preliminary data suggest that this approach can be successfully applied to the WIS. These Sr data supply an independent, salinity proxy with which can better constrain the isotopic composition of the water. Together, these approaches will allow us to test our three hypotheses and add significantly to our understanding of the WIS and the macroinvertebrates that inhabited it.The broader impacts of this study include insights into the short-term biologic and environ-mental dynamics of greenhouse climate modes. The anticipated results should have a substantial impact as 'ground truth' for constraining hypotheses generated about greenhouse climates. It will result also in the training of several graduate and undergraduate students in a multidisciplinary project that will introduce them to the synergy between field and laboratory techniques. As in the past, where underrepresented groups have been involved in various projects undertaken by the PIs, we will continue to attempt to involve those students in this endeavor. Furthermore, because this is a collaborative project involving PIs from universities, a natural-history museum, and the Federal government, it will necessarily involve networking and foster interaction among these institutions. The involvement of the AMNH offers unique opportunities to present these research results to a broad, public audience. This is especially significant because a better understanding of greenhouse climate is critical to society's understanding of predicted human-induced climate change as well as to the larger ramifications that these changes may entail for future Earth history.

这项多学科的研究建议使用氧、碳和锶同位素分析在由西内海晚寒武纪(74 Ma；晚白垩世)压缩生物带(74 Ma；晚白垩世)圈定的单个区间内发现的原始软体动物，以检验四个最重要的假说，这些假说利用了PI和顾问的长处。这些是：1.通过个体标本的个体发育所进行的地球化学分析晚寒武世生物的生长速度和其他古生物学方面，如迁徙模式，可以用岩石年代学方法来确定。生物群，特别是软体动物元素，在水柱和底物上/在底物上占据了不同的生态位，这些不同生境的信号被捕获在它们的同位素特征中。由于温度和盐度的差异，威斯康星州存在着显著的环境梯度，可以使用保存完好的软体动物贝壳中的氧和锶同位素进行测量和区分。除了解决我们的一般假设，同位素数据将使我们能够批判性地分析一系列相互竞争的古海洋学、古生物学和古气候假说，这些假说已经被提出用于晚白垩世世界。这些包括：白垩纪的环流模式、白垩纪的分层、个别菊石分类群的栖息地范围和深度、白垩纪软体动物的生长速度以及海洋温度的季节性波动。为了解决上面提出的问题，我们建议对晚白垩世期间非常富含化石的Pierre页岩中的单个时间段进行详细调查，重点放在B.compressus生物带。在这一生物带中的沉积在威斯康星州非常普遍，并经常伴随着对早期成岩结核中的动物群的精细保存，包括文石元素。为了收集必要的标本，我们将对科罗拉多州中部、南达科他州中部和西部以及蒙大拿州西部到东部代表南北和陆上-近海断面的地点进行抽样。我们将在各地测量详细的切片，收集含有不同软体动物的结核。在进行任何同位素分析之前，将使用显微和地球化学技术对所有标本进行筛选，以寻找成岩作用的任何证据。然后将对通过成岩筛选的样品进行d13C和d18O分析，以确定它们的成岩年代学。由于贝壳材料所处的水环境的值对于准确估计温度和盐度是至关重要的，我们还建议分析我们的一部分样品的锶同位素比率。最近的研究表明，在淡水输入是系统重要组成部分的地区，如河口，87Sr/86Sr主要反映盐度而不是地质年龄，我们的初步数据表明，这种方法可以成功地应用于WIS。这些锶数据提供了一个独立的盐度替代物，可以更好地约束水的同位素组成。总之，这些方法将使我们能够测试我们的三个假设，并显著增加我们对WIS和栖息在其中的大型无脊椎动物的理解。这项研究的更广泛影响包括对温室气候模式的短期生物和环境动力学的洞察。预期的结果应该会产生实质性的影响，因为它是约束有关温室气候的假说的“基本事实”。它还将在一个多学科项目中培训几名研究生和本科生，向他们介绍实地技术和实验室技术之间的协同作用。一如以往，当代表人数不足的团体参与督导所进行的各项计划时，我们会继续尝试让这些学生参与这项工作。此外，由于这是一个涉及大学、自然历史博物馆和联邦政府的私人投资机构的合作项目，它必然涉及网络和促进这些机构之间的互动。AMNH的参与为向广大公众展示这些研究成果提供了独特的机会。这一点特别重要，因为更好地了解温室气候对于社会理解预测的人类引起的气候变化以及这些变化可能对未来地球历史产生的更大影响至关重要。