RPG: Millennial-Scale Paleoclimatic Cycles Expressed in Paleozoic Basinal Marine Sequences

RPG：古生代盆地海洋层序中表达的千年规模的古气候循环

• 批准号: 9210462
• 负责人: Maya Elrick
• 金额: $ 1.8万
• 依托单位: University of New Mexico
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1992
• 资助国家: 美国
• 起止时间: 1992-07-15 至 1995-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9210462&HistoricalAwards=false
• 关键词: RPG; Millennial; Scale; Paleoclimatic; Cycles

The proposed research is to investigate the origin and periodicity of rhythmically interbedded limestone-marl couplets in four separate Paleozoic basinal marine sequences. In each of the sequences, the limestone-marl couplets are characterized by decimeter-scale alternations of even-bedded, laminated limestone and marls; well-preserved calcareous fossils in marl layers indicates a primary depositional(versus diagenetic origin) to the interbeds. Spectral analysis of the limestone-marl interbeds will be conducted to determine whether there is a regularly cyclicity to the bedding couplets, and the duration of the cycles will be determined from a range of sedimentation rates calculated for each individual sequence. A planning grant is submitted to study the sedimentologic origin and periodicity pf rhythmically bedded limestone-marl couplets in one of the proposed sequences; the Middle Cambrian of western Utah (Wheeler and Marjum Formations). The emphasis of the pilot project is to develop accurate and time-efficient sampling techniques for generating time series in interbedded limestone and marl facies. In previous studies, time series generated from variations in HCI-insoluble residues has proven to be an accurate method, however it is very laboratory-time intensive. Consequently, three other less-time consuming methods will be tested on the Middle Cambrian couplets determine which technique (s) best reflects the rhythmic nature of the deposits. Specific planning grant activities will include describing and interpreting the sedimentologic and stratigraphic characteristics of the basinal facies, evaluating the lateral continuity of limestone-marl couplets, sampling the best-exposed section for variations in HCI-insoluble residues, magnetic properties, and bed- thickness variations. Results from spectral analysis of the different time series will be compared to determine which time series sampling technique(s) are appropriate for interbedded limestone-marl facies. The cause of millennial-scale paleoclimatic fluctuations is not well understood, however they have been attributed to changes in solar activity or due to the nonlinear response of the climate to precessional (~20,000 yr) orbital forcing. If the periods of such persistent oscillations can be characterized, they offer the potential for developing high-resolution chronostratigraphy, with a greater resolution than Milankovitch cycles, that can be used to calibrate the length of time between absolute datums, variations in sedimentation rates, biologic evolution rates, and the time intervals over which geomagnetic reversals occur.

本研究拟探讨其起源及 韵律互层石灰岩-泥灰岩偶层的周期性 四个独立的古生代盆海相层序。 的每一个中 序列，石灰岩泥灰岩对联的特点是， 分米级的均匀层状石灰岩 和泥灰岩;泥灰岩层中保存完好的钙质化石 表明主要沉积（相对于成岩起源）， 夹层 灰岩-泥灰岩互层的光谱分析将 以确定是否存在定期循环 到床上对联，周期的持续时间将是 根据为每个计算的沉降率范围确定 个别序列。 提交了一份规划拨款，用于研究沉积学 韵律层状灰岩-泥灰岩成因与周期性 其中一个拟议序列中的对联;中寒武世 犹他州西部（惠勒和Marjum地层）。 的重点 试点项目是开发准确和省时的采样 在石灰岩夹层中生成时间序列的技术， 泥灰岩相 在以前的研究中，从 HCl不溶性残留物的变化已被证明是准确的 方法，但它是非常实验室的时间密集型。 因此，其他三种耗时较少的方法将被 在中寒武世的对句上进行了测试， (s)最能反映沉积物的韵律性质。 具体的规划赠款活动将包括描述和 解释沉积学和地层学特征 盆地相的横向连续性， 石灰岩泥灰岩对联，采样最好的暴露部分， HCl不溶性残留物、磁性和床层的变化， 厚度变化。 光谱分析的结果 将比较不同的时间序列以确定 系列采样技术适用于夹层 灰岩泥灰岩相 千年尺度的古气候波动的原因是 不太清楚，但它们被归因于变化。 太阳活动或由于气候的非线性响应 岁差（~ 20，000年）轨道强迫。 如果周期 这种持续的振荡可以被表征，它们提供了 发展高分辨率年代地层学的潜力， 比米兰科维奇周期更高的分辨率，可用于 校准绝对基准、偏差之间的时间长度 沉积速率，生物进化速率， 地磁反转发生的时间间隔。