Integrated Paleontological, Geochemical, and Paleoceanographic Studies on the Taconic Foreland Basin

塔科尼克前陆盆地的综合古生物学、地球化学和古海洋学研究

• 批准号: 8804344
• 负责人: John Cisne
• 金额: --
• 依托单位: Cornell University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1988
• 资助国家: 美国
• 起止时间: 1988-07-01 至 1990-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=8804344&HistoricalAwards=false
• 关键词: Integrated; Paleontological; Geochemical; Paleoceanographic; Studies

Studies on a roughly five million year long Middle Ordovician sequence in the Taconic Foreland Basin, New York are addressed to these questions: How did water temperature and oxygen content vary with depth in going from a continental carbonate platform down the outer slope of a subduction trench? Was oceanic deep circulation driven by sinking of warm, saline water from low-latitude platforms, as has been suggested for this and other times of highest sea stand? Twelve years' background work on the stratigraphy and paleontology of the sequence, including an ongoing two-year feasibility study, has made a unique opportunity for answering these and related questions from carbon and oxygen isotopic studies on shells of bathymetrically wide-ranging benthic invertebrates, and from carbon and sulfur analyses of sediments. Relative water depth is measured in terms of position on downslope transects along individual volcanic ash layers and, over time, through gradient analysis of fossil assemblages. Relative water temperature will be determined from oxygen isotopic composition in one articulate brachiopod (low-Mg calcite), two inarticulate brachiopods (calcium phosphate), and other taxa selected for comparison. Evidently, texturally and chemically well-preserved calcareous brachiopods are isotopically little-altered: specimens from the same sampling station yield tightly clustered 180 values similar to those of the best-preserved Middle and Late Ordovician material. The density of puncta on the articulate brachiopod's shell (proportional to temperature in modern forms) is proportional to relative depth, and may provide a check on 80O as a temperature measure. Research will aid in paleoceanographic reconstruction and in identification of possible areas for resource exploration.

对纽约州塔科尼克前陆盆地长达约 500 万年的中奥陶世层序的研究旨在解决以下问题：从大陆碳酸盐台地向下俯冲海沟外坡的过程中，水温和氧含量如何随深度变化？ 正如这次和其他最高海位时期所暗示的那样，海洋深层环流是否是由低纬度平台的温暖咸水下沉驱动的？ 十二年的地层学和古生物学背景工作，包括正在进行的为期两年的可行性研究，为回答这些问题和相关问题提供了独特的机会，这些问题来自对测深范围广泛的底栖无脊椎动物贝壳的碳和氧同位素研究，以及沉积物的碳和硫分析。 相对水深是根据沿各个火山灰层的下坡横断面的位置来测量的，并且随着时间的推移，通过化石组合的梯度分析来测量。 相对水温将根据一种有关节腕足动物（低镁方解石）、两种无关节腕足动物（磷酸钙）和选择用于比较的其他类群的氧同位素组成来确定。 显然，在结构和化学上保存完好的钙质腕足动物的同位素变化很小：来自同一采样站的标本产生了紧密聚集的 180 个值，与保存最完好的中奥陶世和晚奥陶世材料的值相似。 关节腕足动物外壳上的点的密度（与现代形式的温度成正比）与相对深度成正比，并且可以提供对 80° 作为温度测量的检查。 研究将有助于古海洋重建和确定可能的资源勘探区域。