Using oxygen isotopes from apatitic conodonts to understand the origins of Paleozoic-Triassic 3rd-order (My-scale) sea-level changes

利用磷灰石牙形石中的氧同位素了解古生代-三叠纪第三级（My-scale）海平面变化的起源

• 批准号: 0518205
• 负责人: Maya Elrick
• 金额: --
• 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: 2005
• 资助国家: 美国
• 起止时间: 2005-09-15 至 2009-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0518205&HistoricalAwards=false
• 关键词: Using; oxygen; isotopes; apatitic; conodonts

Precambrian through Phanerozoic marine deposits are dominated by lithological, geochemical, and biological records of repeated sea-level changes ranging in duration from 10 thousand to 10 million years. The objectives of the proposed research are to understand the origin of persistent, but enigmatic ~1-5 My-scale sea-level changes which result in the deposition of transgressive-regressive marine sequences tens to about a hundred meters thick. The method used to evaluate the origin of these sequences is to analyze the delta-18 Oxygen values of conodonts (extinct apatitic marine microfossils) from selected Ordovician through Triassic sequences to determine if a systematic relationship exists between del 18-O values and transgressive-regressive facies trends.If a systematic relationship between del 18-O values and transgressive/regressive facies trends is observed, then this will indicate that My-scale climate changes are responsible for sequence development. If no relationship between del 18-O values and facies changes is observed, then tectonic process(es) unrelated to climate change are responsible. The research will also evaluate the depth habitat of certain Ordovician and Triassic conodonts; this is crucial for reconstructing depth-dependent marine paleotemperatures and isotopic compositions. This research is primarily focused on understanding the My-scale controls on the infilling of marine basins. If the sea-level changes are, in fact, controlled by climate variations, facies-independent sea-level curves can be constructed and the argument for long-period orbital forcing modulation is supported. This may permit using these sequences for calibrating the Paleozoic-Triassic geological time scale, much like shorter term orbital cycles (~20-100 ky) are being used to calibrate the Cenozoic time scale. The techniques, data, and results will be utilized to develop hands-on, inquiry-based laboratory exercises for undergraduate Earth History and Sedimentology-Stratigraphy classes at UNM. The techniques and results will also be incorporated into graduate-level lectures in Carbonate Stratigraphy, Paleoclimatology, and Stable Isotope Geology. Results from this research will be presented at conferences (GSA, AGU, AAPG), in appropriate journal publications, and invited university seminars.

前寒武纪至显生宙的海相沉积以岩性、地球化学和生物记录为主，海平面重复变化的持续时间从1万年到1000万年不等。这项研究的目的是了解持续但神秘的海平面变化的起源，这些变化导致数十至约100米厚的海侵-海退海序沉积。评价层序成因的方法是对奥陶系至三叠系层序中已灭绝的磷灰岩海相微体化石--牙形刺的18O值进行分析，以确定DEL18-O值与海侵-海退相趋势之间是否存在系统的关系，如果观察到DEL18-O值与海侵/海退相趋势之间的系统关系，则表明我尺度的气候变化是层序发育的原因。如果没有观察到DEL18-O值与相变化之间的关系，那么与气候变化无关的构造过程就是原因。这项研究还将评估某些奥陶系和三叠纪牙形刺的深度栖息地；这对于重建依赖深度的海洋古温度和同位素组成至关重要。这项研究主要集中在了解My-Scale对海洋盆地充填的控制。如果海平面变化实际上是由气候变化控制的，则可以建立独立于相的海平面曲线，并支持长周期轨道强迫调制的论点。这可能允许使用这些序列来标定古生代-三叠纪地质时标，很像正在使用较短的轨道旋回(~20-100 Ky)来标定新生代时标。这些技术、数据和结果将被用来为UNM的本科生地球历史和沉积学-地层学课程开发动手的、以探究为基础的实验室练习。这些技术和成果还将被纳入碳酸盐地层学、古气候学和稳定同位素地质学的研究生课程。这项研究的结果将在会议(GSA、AGU、AAPG)、适当的期刊出版物和受邀的大学研讨会上公布。