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

基本信息

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

项目摘要

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THIS多学科研究建议在单个间隔内发现的原始软体动物的O，C和SR同位素分析，由已故的Campanian baculites Compressus Biozone（74 mA;晚白垩纪）从西部内部海路（WIS）（WIS）中检查四个超过ARCOTHISSESESESSESS，从而实现PIS和PIS的强度。这些是：1。通过单个标本的个体发育进行的地球化学分析（Sensu Jones，1983） - 为了解晚期白垩纪晚期上腹膜海的动力学至关重要的环境条件的年度记录（例如，季节性温度波动，水质动力学）提供了年度至年子节记录。可以使用硬化量方法来确定坎帕尼生物体晚期生物的增长率和其他古生物学方面，例如迁移模式。3。生物群，尤其是软体动物元素，在水柱和基板上/底物中占据了不同的壁ni，以及这些各种栖息地的信号在其同位素特征中被捕获。4。 WIS中存在着重要的环境梯度，这是由于温度和盐度的差异而强迫的，并且可以使用保存完好的软体动物壳的氧气和畸形同位素进行测量和区分。除了解决我们的一般假设之外，同位素数据还可以使我们能够批判性地分析一系列针对晚期白垩纪世界提出的一系列竞争性古生物学，古生物学和古气候假设。其中包括：WIS中的循环模式，WIS的分层，栖息地范围和个别氨基分类群的深度，白垩纪软体动物的生长速率以及海洋温度中的季节性波动。为了解决上述问题，我们建议在非常化石的Pierre页岩中，通过白垩纪晚期的白垩纪对单个时间间隔进行详细研究，该时间间隔针对B. compressus Biozone。在此生物区域期间的沉积在WIS中很普遍，并且经常伴随着在早期成岩纤维混凝土中精致的动物区系，包括库拉贡元素。为了收集必要的标本，我们将在科罗拉多州中部，中部和南达科他州以及蒙大拿州西部至蒙大拿州的西部进行采样，这些地区代表了北南和陆上岸的样品。我们将在所有地区衡量详细部分，并收集包含多种软体动物动物区系的混凝土。在进行任何同位素分析之前，将对所有标本进行筛选，以获取使用微观和地球化学技术的任何成岩作用的证据。然后，将对D13C和D 18O进行分析，以建立其硬化量。由于将壳材料分泌的水性环境的值对于得出准确的温度和盐度估计至关重要，因此我们还建议分析其SR同位素比的样品子集。最近的研究表明，在诸如河口的地区，淡水输入是系统中重要的组成部分，87 SR/86 SR主要反映了盐度而不是地质年龄，而我们的初步数据表明，这种方法可以成功地应用于WIS。这些SR数据提供独立的盐度代理，可以更好地限制水的同位素组成。这些方法共同使我们能够检验三个假设，并大大增加了我们对居住在该的WIS和大型无脊椎动物的理解。这项研究的更广泛的影响包括对温室气候模式的短期生物和环境动态的见解。预期的结果应该具有重大影响，因为“地面真相”，用于限制关于温室气候的假设。这也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现场技术和实验室技术之间的协同作用。与过去一样，在PIS进行的各种项目中，代表性不足的团体参与了，我们将继续尝试让这些学生参与这项工作。此外，由于这是一个合作项目，涉及大学，自然博物馆和联邦政府的PI，因此必然涉及这些机构之间的网络和促进互动。 AMNH的参与提供了独特的机会，可以向广泛的公众受众展示这些研究结果。这尤其重要，因为对温室气候的更好理解对于社会对预测的人类引起的气候变化的理解以及这些变化可能需要对未来地球历史所需的更大后果的理解至关重要。