Glacial-Interglacial Variations in Late Paleozoic Atmospheric Circulation Inferred from Loessite-Paleosol Couplets of Western Equatorial Pangea

从西赤道盘古大陆黄土-古土壤联体推断晚古生代大气环流的冰期-间冰期变化

• 批准号: 0418983
• 负责人: Michael Soreghan
• 金额: --
• 依托单位: University of Oklahoma Norman Campus
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-08-01 至 2009-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0418983&HistoricalAwards=false
• 关键词: Glacial; Interglacial; Variations; Late; Paleozoic

Earth's climate during the late Paleozoic (ca. 300 Ma) was profoundly affected by both large-scalecontinental glaciation and monsoonal circulation. Accordingly, key elements of its climate exhibitparallels to Earth's modern climate, which has intrigued both those who model climate, and those whoreconstruct climate using proxy data. Validation and further sophistication of climate models of thisinterval are hampered, however, by low-resolution geologic datasets. That is, although the broad strokesof Pangea's climate system are well established, many aspects remain unconstrained.Preliminary geochronologic and sedimentologic data collected by the PIs from a lower Permianloessite-paleosol couplet in the study region document a profound shift in equatorial wind direction andstrength; the PIs hypothesize that this shift signals a geologically abrupt change in the intensity ofmonsoonal circulation of western Pangea between glacials, and interglacials. The objective of theproposed study, therefore, is to examine and characterize in detail the character, variability, andchronology of such high-frequency shifts in atmospheric circulation in western equatorial Pangea, justbefore and after onset of monsoonal conditions. To achieve this, the PIs and students will study loessite(eolian silt) and intercalated paleosols that record alternating glacial-interglacial states. The PIs havetargeted for study loessite-paleosol couplets that represent wide geographic coverage in westernequatorial Pangea (western U.S.), and that date from (1) middle-late Pennsylvanian (zonal), and (2) earlyPermian (monsoonal) times. Each study couplet will be subjected to several previously-tested techniquesincluding detrital-zircon based provenance analysis, magnetic susceptibility, whole-rock geochemistry,and grain-size analysis as proxies for various climatic parameters including wind direction, strength, andseasonality, and relative aridity. High-precision, radio-isotopic (U-Pb) dating of the youngest (volcanic)detrital zircons and some experimental dating of pedogenic carbonate will be used to improve absoluteage constraints on the target couplets, and constrain durations of these glacial-interglacial shifts.Intellectual Merit of Proposed Activity-- Project results will enable examination of late Paleozoicicehouse variations in atmospheric circulation at an unprecedented detail, and in particular, high-resolution(glacial-interglacial) shifts in equatorial circulation during both zonal and monsoonal states ofthe Pangean interval. Results will also provide improved age constraints on target strata, and durations ofclimatic fluctuations, and will enable further testing of the paleosol-carbonate dating technique.Broader Impacts Resulting from Proposed Activity "Project results will provide better constraints forclimate models of the late Paleozoic and for natural variation in climatic conditions of interglacials overgeologically long periods of time. Accordingly, results should further our understanding of Earth'sclimate system in general, ultimately contributing to improved climate predictions in our moderninterglacial world. The PIs will fund and train at least two graduate students directly from this proposedresearch, and have a strong commitment to, and history of, involving undergraduate geoscience majors intheir research, which they will continue in the proposed project. OU's formal agreement with Fort ValleyState University (a Historically Black University), in which upperclassmen complete their geologydegrees at OU, offers an excellent opportunity to involve minority students in this undergraduate research.MJS has also used NSF funds to support science-education majors in undergraduate research projects, andwill actively recruit at least one such student to work on aspects of the proposed project. The projectwill enhance teaching and training at all levels (undergraduate through professional). MJS teaches anEarth System Science course for education majors, and GSS teaches advanced courses in Earth's PastClimate and Depositional Systems; both PIs regularly utilizes case examples from their own research toillustrate climate concepts. Furthermore, the project will enable significant cross-disciplinary training, andinvolves a mixed-gender research team of sedimentologists and geochronologists. Finally, the PIs andstudents will continue to disseminate results in high-profile journals and at national meetings.

大量冰川和季风循环中，晚古生代晚期（大约300 mA）期间的地球气候受到深刻的影响。因此，其气候的关键要素展示了地球现代气候，这既吸引了那些对气候建模的人，也吸引了那些使用代理数据建筑气候的人。但是，低分辨率的地质数据集对该间隔间气候模型的验证和进一步的复杂性受到阻碍。也就是说，尽管pangea的气候系统的广泛震动已经确定，但许多方面仍然不受约束。在研究区域中，PIS收集的PIS收集的基本学和沉积学数据是研究区域中的较低二叠纪 - 五洛斯果溶液，记录了赤道风方向和斯特长的赤道风向的深刻变化； PI假设这种转移标志着冰川和冰川间冰川之间西部pangea和冰期之间的地质循环强度在地质上突然变化。因此，该研究的目的是详细检查和表征西方赤道pangea大气循环中这种高频转移的特征，可变性，和教学学，季风条件开始时和之后。为了实现这一目标，PIS和学生将学习Loessite（Eolian淤泥）和插入的古溶质，以记录交替的冰川间 - 冰川状态。 PIS用于研究loesite-Paleosol的研究，代表西方均等Pangea（美国西部）的广泛地理覆盖范围，并从（1）宾夕法尼亚州中期（Zonal）和（2）（2）早期佩里米亚人（蒙古）时代。每个研究对联将经过几种先前测试的技术，包括基于碎屑的出处分析，磁敏感性，全摇滚地球化学和晶粒尺寸分析，作为各种气候参数的代理，包括风向，强度，强度和季节性和相对的干扰。最年轻（火山）碎屑锆石的高精度，放射性异位（U-PB）的日期和一些实验性碳酸盐含量将用于改善目标偶联的绝对约束，并限制这些冰川相互作用的持续时间，以促进良好的良好循环效果。在Pangean间隔的区域和季风状态期间，赤道循环的前所未有的细节，尤其是高分辨率（冰川间 - 冰河）的变化。结果还将为目标地层和持续波动的持续时间提供改进的年龄限制，并能够进一步测试古溶质碳酸盐约会技术。提议的活动所产生的影响力的影响“项目结果将提供更好的限制，以使晚期的较晚模型和在我们的跨性别范围内的自然差异，以实现较长的范围，以实现较长的时间，以实现时间表，这是在我们的互助过程中，该时间段的良好时期，该学期的范围是学的。总体而言，地球的系统最终有助于改善我们的现代冰河世界中的气候预测。他们在OU的地质学家提供了一个极好的机会，让少数群体参与这项本科研究。MJS还使用NSF资金来支持科学教育专业的本科生研究项目，并积极地招募了一个这样的学生来招募一项项目，从而在所有级别的教育中培训了培训。 GSS在地球的过去和沉积系统中教授高级课程；这两个PIS经常利用自己的研究概念的案例。