Integrated Sedimentologic/Magnetic Records of Late Paleozoic Climate, Western Pangea

[805130] soreghan晚古生代的气候史引起了人们极大的兴趣。极地冰川作用是宾夕法尼亚时期的特征，大陆组合在二叠纪时期明显引发了大季风条件。重大的气候趋势和/或波动可能记录了这些事件，但这些气候变化的证据和特征仍然缺乏。本研究的目的是：(1)验证沉积学/岩石磁学综合方法获取上古生界黄土岩古气候数据的可行性，(2)将这些技术应用于盘古大陆西部低纬古气候的解释。最近对许多地区第四纪-上新世黄土序列的研究表明，岩石磁分析在古气候研究中的应用。这些研究表明，在相对温暖湿润的间冰期，超细和细粒磁性物质的成土作用。即使在土壤形成的沉积学证据不明确的地方，磁性代用物也能指示气候和时间相关的土壤形成。我们的初步分析表明，在非常古老的黄土岩中保存了与土壤成因形成的磁性物质有关的磁化率增强。我们建议通过收集科罗拉多州和犹他州暴露的上古生界（宾夕法尼亚-二叠纪）黄土剖面的详细沉积学和岩石磁性数据来扩展这些分析。在实验室中，我们将进行岩石磁性分析（如归一化铁磁化率、频率相关磁化率、非滞后剩磁、低温剩磁），以获取磁化率变化的来源，并将这些数据与沉积学/古土壤学和成岩数据相结合，以评估古气候信号。最终，我们希望将这些数据与改进的年龄分辨率联系起来，以便评估目标剖面内部和之间的宾夕法尼亚中部-二叠纪早期区间的短期和长期气候趋势。据我们所知，我们的工作是第一次尝试将岩石磁技术应用于前新生代（上新世-更新世）黄土岩的古气候分析；我们认为，证明沉积学/岩石磁学综合方法对上古生代黄土岩的适用性，将代表一个重大的：(1)在非常古老的地层中进行古气候研究的技术进步，(2)有助于我们对晚古生代西盘古大陆低纬度古气候的理解。

9805130SoreghanThe history of late Paleozoic climate is of great interest. Polar glaciation characterized Pennsylvanian time, and continental assembly apparently initiated megamonsoonal conditions by Permian time. These events are likely recorded by significant climatic trends and/or fluctuations, but the evidence for and character of these climate changes remain poorly constrained. The objective of the proposed research is to (1) confirm the feasibility of obtaining paleoclimatic data from upper Paleozoic loessite using an integrated sedimentologic/rock-magnetic approach, and (2) apply these techniques to elucidating low-latitude paleoclimate of western Pangea. Recent studies of Quaternary-Pliocene loess sequences in many regions have demonstrated the utility of rock-magnetic analyses for paleoclimate studies. These studies indicate pedogenic production of ultra-fine and fine-grained magnetic material during relatively warm, wet (interglacial) periods. Magnetic proxies signal climatically and temporally dependent soil formation even where sedimentologic evidence for pedogenesis is equivocal. Our preliminary analyses establish that susceptibility enhancement linked to pedogenically formed magnetic material is preserved in very ancient loessite. We propose to extend these analyses by collecting detailed sedimentologic and rock magnetic data from upper Paleozoic (Pennsylvanian-Permian) loessite sections exposed in Colorado and Utah. In the lab, we will perform rock-magnetic analyses (e.g., normalized ferrimagnetic susceptibility, frequency-dependent susceptibility, anhysteretic remanent magnetization, low-temperature remanence) to access the origin of magnetic susceptibility variations, and integrate these data with sedimentologic/paleopedologic and diagenetic data to evaluate the paleoclimatic signal. Ultimately, we hope to link these data to an improved age resolution in order to assess short-and long-term climatic trends across the middle Pennsylvanian-early Permian interval both within and between the target sections. To our knowledge, our effort represents the first attempt to apply rock-magnetic techniques for paleoclimatic analyses in pre-Cenozoic (Plio-Pleistocene) loessite; we believe that demonstration of the applicability of an integrated sedimentologic/rock-magnetic approach to upper Paleozoic loessite will represent a significant (1) technical advance for paleoclimatic studies in very ancient strata, and (2) contribution toward our comprehension of the low-latitude paleoclimate of late Paleozoic western Pangea.