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

从前寒武纪到中生代的海相沉积主要是由岩石学、地球化学和生物学记录的海平面反复变化所决定的，其持续时间从1万年到1千万年不等。拟议研究的目标是了解持续的起源，但神秘的~1-5百万年规模的海平面变化，导致海进海退的海洋序列沉积几十到大约一百米厚。评价这些层序成因的方法是分析牙形石的δ-18氧值（已灭绝的磷灰石海相微体化石），以确定del 18-O值与海进-海退相趋势之间是否存在系统关系。如果观察到del 18-O值与海进/海退相趋势之间存在系统关系，那么这将表明，我的规模的气候变化是负责序列的发展。如果del 18-O值与相变化之间没有关系，那么与气候变化无关的构造过程是负责的。该研究还将评估某些奥陶纪和三叠纪牙形刺的深度生境;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我的规模控制海洋盆地的填充。如果海平面的变化实际上是由气候变化控制的，那么就可以建立与相无关的海平面曲线，从而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校准古生代-三叠纪地质时标，就像使用较短期的轨道周期（~20-100 ky）来校准新生代时标一样。技术，数据和结果将被用来开发动手，探究为基础的实验室练习本科地球历史和沉积地层学类UNM。这些技术和结果也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邀请大学研讨会上发表。

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.