COLLABORATIVE RESEARCH: Constraining Tertiary Temperatures, Salinities, and Ocean Chemistry: An Isotopic and Trace-metal Study of Serially-sampled Mollusks

合作研究：限制第三纪温度、盐度和海洋化学：连续采样软体动物的同位素和痕量金属研究

• 批准号: 0126311
• 负责人: Ethan Grossman
• 金额: $ 6.5万
• 依托单位: Texas A&M Research Foundation
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-01-01 至 2005-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0126311&HistoricalAwards=false
• 关键词: COLLABORATIVE; RESEARCH; Constraining; Tertiary; Temperatures

ABSTRACTConstraining Tertiary Temperatures, Salinities, and Ocean Chemistry: An Isotopic and Trace-metal Study of Serially-sampled MollusksE. Grossman, Y. Rosenthal, and C. Lear The Tertiary Period (55 to ~2 million years ago) presents our best opportunity to study the transition from an ice-free "greenhouse world" to today's "icehouse world" and to understand the response of present and future climates to high atmospheric carbon dioxide levels. This proposal will take advantage of the superb fossil record of the US Gulf Coast and two independent measures of ancient ocean temperatures, oxygen isotope (18O/16O) and strontium/calcium ratios in fossil shells, to characterize this dramatic change in global climate. These results will address a longstanding controversy of early Tertiary climate, the "cool tropics paradox". Oxygen isotope measurements of planktonic foraminifera indicate cool tropical sea-surface temperatures for a time when high latitudes experienced unusual warmth. This contradicts model simulations of greenhouse world climates that predict that both polar and tropical temperatures must have been significantly warmer than today. A common explanation for the discrepancy is that paleotemperature data from planktonic foraminifera have been modified by post-depositional chemical alteration (diagenesis). By analyzing pristine mollusk shells, this study will obviate this limitation of previous studies. A second objective is to improve our understanding of the nature and causes of the climatic transition near the Eocene-Oligocene boundary associated with rapid Antarctic glaciation and faunal overturn. Recent work using oxygen isotope ratios in fish otoliths from US Gulf Coastal Plain sediments has linked faunal overturn to increased seasonality, in particular colder winters in this region. However, interpretation of such data is limited by poorly constrained estimates of global ice volume and local salinity variations. This study will use paired measurements of mollusk Sr/Ca and 18O/16O to examine changes in low-latitude sea-surface temperatures and seasonality across this event. Lastly, modern mollusk samples will be collected with temperature, salinity, and seawater 18O/16O data from various sites in the Gulf of Mexico and Eilat, Israel. These samples will be analyzed for stable isotopes and trace metals (especially Sr/Ca) to calibrate trace metal-temperature relations.

第三纪的温度、盐度和海洋化学：对软体动物连续采样的同位素和微量金属研究。Grossman，Y. Rosenthal和C.第三纪（5500万年前到200万年前）是我们研究从无冰的“温室世界”到今天的“冰库世界”的转变以及了解现在和未来气候对大气中高二氧化碳水平的反应的最佳机会。 该提案将利用美国墨西哥湾沿岸极好的化石记录和两种独立的古代海洋温度测量方法，即化石贝壳中的氧同位素（18 O/16 O）和锶/钙比率，来描述全球气候的这一巨大变化。 这些结果将解决第三纪早期气候长期存在的争议，“凉爽的热带悖论”。 南极有孔虫的氧同位素测量表明，当高纬度地区经历不寻常的温暖时，热带海面温度较低。 这与温室世界气候的模型模拟相矛盾，该模型预测极地和热带温度必须比今天高得多。 对这种差异的一种常见解释是，来自南极有孔虫的古温度数据被沉积后化学蚀变（成岩作用）修改了。 通过对原始贝类贝壳的分析，本研究将弥补以往研究的不足。 第二个目标是提高我们对始新世-渐新世边界附近气候转变的性质和原因的认识，这一转变与南极快速冰川作用和动物区系翻转有关。最近的工作，使用氧同位素比值在鱼耳石从美国海湾沿岸平原沉积物中的动物区系的翻转增加的季节性，特别是在这个地区的寒冷的冬天。 然而，这些数据的解释是有限的约束不良的全球冰量和当地的盐度变化的估计。这项研究将使用成对的测量软体动物Sr/Ca和18 O/16 O，以检查在低纬度海面温度和季节性的变化，在整个事件。 最后，将从墨西哥湾和以色列埃拉特的各个地点收集现代软体动物样本，并提供温度、盐度和海水18 O/16 O数据。 将对这些样品进行稳定同位素和微量金属（特别是Sr/Ca）分析，以校准微量金属-温度关系。