Collaborative Research: A high-resolution middle Pleistocene paleoclimate record from the Valles Caldera, New Mexico

该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。这笔拨款支持新墨西哥大学、北亚利桑那大学和明尼苏达大学德卢斯分校之间的一个合作项目，该项目将对新墨西哥北部山谷火山口的一个独特的82米长的湖泊沉积物岩心（VC-3）进行详细分析。这个核心代表了过去与现代相似的关键时间间隔。因此，对地核观测到的气候变化的了解将导致对西南地区未来气候变化的最详细评估。知识价值：2004年5月，GLAD5钻井项目在新墨西哥州的Valles Caldera回收了一个82米深的湖泊沉积物岩心。根据岩心底部附近的岩心估算的Ar-Ar年龄（552±3 ka）、多个代用物中的两个不同的冰川终止期（VI和V），以及与全球公认的事件（14a和11a）相关的两个地磁极性“事件”的识别，将这些湖泊沉积物限制在更新世中期（MIS 14至MIS 10）。这个小组的初步工作表明，在地核的两个长间冰期（MIS 11和MIS 13）中，温度和水文气候之间存在着一种有趣的关系。间冰期温度峰值（MBT代用物，花粉）与岩心（泥裂间隔）延长的干燥期有很好的相关性。这与最近的预测一致，即由于全球变暖，冬季降水显著减少，北美西南部将出现长期干旱。为了更好地理解这种关键关系，研究小组将以~10厘米或更短的间隔对VC-3岩心进行更详细的采样，以分析温度（MBT代用物，花粉），湖泊生产力（有机碳，Si/Ti比率，生物成因二氧化硅），水文气候（硅藻二氧化硅的del-18O，岩心沉积学特征，花粉和木炭）。具体来说，他们将测试这样一个假设，即在漫长的间冰期，变暖导致延长的干燥气候，减少冬季锋面降水。其他的分析包括剩余物和岩石磁性，主要和次要元素地球化学，XRD， XRF扫描仪分析，碳和氮稳定同位素和C/N比率，以及植物宏观化石，所有这些都将有助于改进古气候代用物。结合这项工作，LANL合作者将进行化合物特定的del-D分析，并获得U&amp；#8208；系列日期，以改善年表，而不花费NSF。这项工作的结果将阐明两个重要的古气候问题：间冰期峰值温度与延长干旱条件之间的关系，以及更新世中期至千年尺度气候变化的性质。更广泛的影响：这项研究将进一步加深我们对北美西南部气候变化的本质及其对山地生态系统的影响的理解。该项目涉及四个研究机构的合作，分别是新墨西哥大学、国立大学、马里兰大学和洛斯阿拉莫斯国家实验室。研究生和教师都将受益于与其他机构的互动，以及每个机构的合作者为项目带来的不同专业知识。这项研究的结果将通过新成立的Valles Caldera国家保护区向公众展示和推广项目。这些信息不仅包括山谷破火山口湖泊形成的时间和由此产生的古气候记录，还包括山谷破火山口深处保存的物质以及火山口火山过程和地表过程之间相互作用的性质。该项目将涉及新墨西哥大学、新非洲大学和马里兰大学的几名研究生的教育和培训。新墨西哥大学的研究生包括一名攻读博士学位的西班牙裔女学生和另一名女研究生。这项研究的结果将纳入参与院校开设的几门课程。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).This grant supports a collaborative project between the University of New Mexico, Northern Arizona University and the University of Minnesota, Duluth which will conduct detailed analyses of a unique 82-m long lacustrine sediment core (VC-3) from the Valles Caldera, in northern New Mexico. This core represents a critical time interval in the past that is similar to the modern. As such, an understanding of climatic changes observed in the core will lead to the most detailed assessment of expected future climate variability in the southwest ever recorded.Intellectual Merit: In May 2004, the GLAD5 drilling project recovered an 82-m deep lacustrine sediment core from the Valles Caldera, New Mexico. Ar-Ar age estimates from a tephra near the base of the core (552±3 ka), two distinct glacial terminations (VI and V) in multiple proxies, and the identification of a two geomagnetic polarity "events", correlated to globally recognized events (14a; and 11a) constrain these lake sediments to the middle Pleistocene (MIS 14 to MIS 10). Initial work by this group shows an intriguing relationship between temperature and hydroclimate during the two long interglacials present in the core (MIS 11 and MIS 13). Peak interglacial temperatures (MBT proxy, pollen) correlate well with extended dry periods in the core (mudcrack intervals). This is consistent with recent predictions of extended drought in SW North America in response to global warming by a marked reduction in winter precipitation.To better understand this critical relationship, the team will conduct more detailed sampling of the VC-3 core at intervals of ~10 cm or less to analyze for temperature (MBT proxy, pollen), lake productivity (organic carbon, Si/Ti ratios, biogenic silica), hydroclimate (del-18O of diatom silica, core sedimentologic characteristics, and pollen and charcoal). Specifically, they will test the hypothesis that during long interglacials, warming leads to extended dry climates with reduced winter frontal precipitation. Additional analyses to be conducted include remanence and rock magnetic properties, major and minor element geochemistry, XRD, XRF scanner analyses, carbon and nitrogen stable isotopes and C/N ratios, and plant macrofossils, all of which will aid in refining paleoclimate proxies. In conjunction with this work, LANL collaborators will conduct compound specific del-D analyses and obtain U‐series dates to improve the chronology at no cost to NSF. Results from this work will shed light on two important paleoclimate questions: the relationship between peak interglacial temperatures and extended dry conditions, and the nature of orbital- to millennial-scale climate change during the middle Pleistocene.Broader Impacts: This study will further our understanding about the nature of climate change in southwestern North America and its impact on montane ecosystems. This project involves collaborations between four research institutions, UNM, NAU, UMD, and Los Alamos National Lab. Both graduate students and faculty will benefit from interactions with the other institutions and the different expertise that collaborators at each institution bring to bear on the project. The results of this study will be available to the general public using displays and outreach programs through the newly created Valles Caldera National Preserve. This information will include not only the timing of lakes forming in the Valles Caldera and the paleoclimatic records derived from them, but also information about the materials preserved at depth in the Valles Caldera and the nature of the interactions between volcanic processes in the caldera and surficial processes. The project will involve education and training of several graduate students at UNM, NAU and UMD. UNM graduate students include a female Hispanic pursuing a PhD and another female graduate student. The results of this study will be integrated into several courses offered at the participating institutions.