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.

摘要本多学科的研究提出了使用O，C和Sr同位素分析的原始软体动物中发现的一个单一的间隔划定的晚Campanian Baculites compressus生物带（74 MA;晚白垩世）从西部内陆航道（WIS）检查四个过度的假设，利用的PI和顾问的优势。这些是：1.通过个体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至近十年记录（例如，季节性温度波动，水团动力学），这是至关重要的了解晚白垩世陆表海的动力学。生长速率和其他古生物学方面的晚坎帕尼亚有机体，如迁移模式，可以建立使用sclerochronologic方法。生物群，特别是软体动物元素，在水体中和底质上/中占据不同的生态位，这些不同生境的信号被捕获在它们的同位素特征中.存在显着的环境梯度的WIS，被迫在温度和盐度的差异，并可以测量和区分使用保存完好的软体动物壳的氧和锶同位素。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竞争的古海洋学，古生物学和古气候的假设，已提出的晚白垩世世界。其中包括：循环模式内的WIS，分层的WIS，栖息地范围和个别菊石类群的深度，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，我们建议对富含碳酸盐的皮尔页岩中的B层进行一次详细的晚白垩世单时间段调查。压缩生物带沉积在这个生物带是广泛的WIS，往往伴随着精致的保存动物群，包括文石元素，在早期成岩结核。为了收集必要的标本，我们将在科罗拉多中部、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沿岸-近海断面的地方取样。我们将在所有地点测量详细的部分，并收集含有不同软体动物区系的结核。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对所有标本进行筛选，以寻找任何成岩作用的证据。通过成岩筛选的样品将进行d13 C和d18 O分析，以建立其硬化年代学。由于壳材料分泌的水环境中的值是至关重要的，以获得准确的估计温度和盐度，我们还建议分析我们的样品的一个子集的Sr同位素比。最近的研究表明，在河口等淡水输入是系统中的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，这种方法可以成功地应用于WIS。这些锶数据提供了一个独立的，盐度代理，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，并显着增加我们的理解的WIS和大型无脊椎动物居住it.The更广泛的影响，这项研究包括洞察短期的生物和温室气候模式的心理动力学。预期的结果应该有一个实质性的影响，作为“地面真相”约束有关温室气候产生的假设。它还将导致在一个多学科项目中培训几名研究生和本科生，该项目将向他们介绍实地和实验室技术之间的协同作用。与过去一样，在代表性不足的群体参与了PI开展的各种项目的情况下，我们将继续努力让这些学生参与这一奋进。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，因此它必然涉及网络并促进这些机构之间的互动。AMNH的参与提供了独特的机会，将这些研究成果呈现给广大的公众。这一点特别重要，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。