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

合作研究：晚白垩世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: 0309343
• 负责人: J Kirk Cochran
• 金额: $ 3.65万
• 依托单位: SUNY at Stony Brook
• 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=0309343&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.

摘要 这项多学科研究建议使用对西部内海道 (WIS) 晚坎帕期压缩杆状生物带（74 MA；晚白垩世）所描绘的单个区间内发现的原始软体动物进行 O、C 和 Sr 同位素分析来检查四个总体利用 PI 和顾问优势的假设。它们是：1。通过单个标本的个体发育进行的地球化学分析 - 硬化年代学（sensu Jones，1983） - 提供了环境条件的年度到十年以下的记录（例如，季节性温度波动、水团动态），这对于了解晚白垩世陆缘海洋的动态至关重要.2.可以使用硬化年代学方法来确定坎帕尼亚晚期生物的生长速率和其他古生物学方面，例如迁移模式。3。生物群，特别是软体动物元素，占据了水柱内和基质上/内的不同生态位，这些不同栖息地的信号在它们的同位素特征中被捕获。4．由于温度和盐度的差异，WIS 中存在显着的环境梯度，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外，同位素数据将使我们能够批判性地分析一系列针对晚白垩世世界提出的相互竞争的古海洋学、古生物学和古气候假设。其中包括：WIS 内的环流模式、WIS 的分层、单个菊石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。为了解决上述问题，我们建议对白垩纪晚期的 PIerre 页岩中以 B. compressus 生物带为重点的化石产区的单个时间间隔进行详细调查。该生物带期间的沉积在 WIS 中广泛存在，并且经常伴随着早期成岩结核内动物群的精美保存，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至东部代表南北和陆上和海上横断面的地区进行采样。我们将测量各地的详细剖面并收集含有不同软体动物群的结核。在进行任何同位素分析之前，将使用显微镜和地球化学技术筛选所有标本，以寻找成岩作用的证据。然后将对那些通过成岩筛选的样本进行 d13C 和 d18O 分析，以确定其硬化年代学。由于分泌壳材料的水环境的值对于准确估计温度和盐度至关重要，因此我们还建议分析一部分样品的 Sr 同位素比。最近的研究表明，在河口等淡水输入是系统重要组成部分的地区， 87 Sr/86 Sr 主要反映盐度而不是地质年龄，我们的初步数据表明，这种方法可以成功应用于信息系统。这些 Sr 数据提供了一个独立的盐度代理，可以更好地限制水的同位素组成。总之，这些方法将使我们能够检验我们的三个假设，并显着增进我们对 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的短期生物和环境动态的见解。模式。预期结果应该作为“基本事实”对温室气候的约束假设产生重大影响。它还将在一个多学科项目中对几名研究生和本科生进行培训，向他们介绍现场技术和实验室技术之间的协同作用。与过去一样，代表性不足的群体参与了 PI 开展的各种项目，我们将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 PI 的合作项目，因此必然涉及网络并促进这些机构之间的互动。 AMNH 的参与提供了向广大公众展示这些研究成果的独特机会。这一点尤其重要，因为更好地了解温室气候对于社会了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。