EAGER: Seismic survey to evaluate the potential of Lake Chalco, Mexico, for continental drilling

这项EAGER拨款支持在墨西哥盆地南端的Chalco湖进行地震反射剖面分析，其最终目标是为国际大陆钻探计划提出建议。Chalco盆地在19世纪和20世纪初被排干用于农业，包含高达500米的湖泊沉积物，记录了数十万年（可能多达数百万年）的亚热带美洲气候历史。Chalco的记录提供了有用的对比资料，可以与陆地遗址（如亚利桑那州贝尔洞穴的化石，危地马拉佩滕伊察的湖泊沉积物，新墨西哥州的卡尔德拉山谷）以及沿海海洋环境（如卡里亚科和圣巴巴拉盆地的沉积物）的中美洲气候记录相比较。Chalco的气候历史可能与美西螈的进化有关，美西螈是Chalco及其邻近盆地特有的一种水生蝾螈，在数千项生理和生物医学研究中被用作“模式生物”。最后，地震测量和沉积记录为墨西哥盆地的构造和火山历史提供了相关信息。陆相湖泊沉积物的古气候记录通常跨越全新世，只有少数比末次盛冰期延伸得更深。最近，人们对湖泊钻探的兴趣开始改变这一现状，在Bear lake（美国）、Valles Caldera（美国）、Peten Itza（危地马拉）、Titicaca（玻利维亚/秘鲁）、Malawi（东非）、Bosumtwi（加纳）和El'gygytgyn（西伯利亚）等地都取得了成功。中铝公司的气候记录应该提供对耦合气候系统过去变化的区域响应的见解。例如，诱发和传播千年尺度气候变化的过程（如Dansgaard-Oeschger和Heinrich事件）仍然存在争议；解决这些争议需要来自地球上许多地区的连续高分辨率气候记录，包括缺乏此类信息的北美热带地区。此外，中更新世至晚更新世间冰期条件作为全新世的可能类似物而特别令人感兴趣。来自南极冰芯的证据证明了中更新世期间大气二氧化碳分压和气候变化的显著差异，但跨越这一区间的高分辨率大陆记录在全球范围内很少见，在北美也没有。Chalco的完整记录有可能提供独特的信息，填补这些关键的空白，提高我们对当前间冰期及其未来进程的理解。更广泛的影响该项目为研究生和本科生培训提供了机会，并利用了与墨西哥同事的持续合作，促进了美国和墨西哥科学界之间的合作。这项工作获得的记录提供了对气候和水文平衡的见解，对资源管理和区域规划有影响。Chalco的沉积档案包含了与地球上人口最密集的城市中心之一直接相关的信息。墨西哥城是1700多万居民的家园，主要建在墨西哥盆地的湖泊沉积物上，这些沉积物在欧洲人征服后被用于农业的湖泊水转移后暴露出来。从与这些湖泊沉积物相关的含水层中持续抽取地下水是造成沉降的主要原因。对过去水文平衡变化的了解将有助于我们了解区域水资源的可用性。

This EAGER grant supports work on seismic reflection profiling in Lake Chalco, at the southern end of the Basin of Mexico, with the ultimate goal of developing a proposal to the International Continental Drilling Program. The Chalco basin, which was drained for agriculture in the 19th and early 20th Centuries, contains up to 500m of lacustrine sediments that have recorded several hundred thousand years (perhaps as much as million years) of subtropical American climate history. The Chalco records provide useful counterpoints to records of Middle American climate from terrestrial sites (e.g. spethelothems from Cave of the Bells, Arizona or lake sediments from Peten Itza, Guatemala or from Valles Caldera, New Mexico) as well as coastal marine settings (e.g. sediments of the Cariaco and Santa Barbara Basins). The climate history of Chalco may be relevant to evolution of the axolotl, an aquatic salamander endemic to Chalco and its neighboring basin that has been used as a 'model organism' in thousands of physiological and biomedical studies. Finally, the seismic survey and sedimentary record provides information relevant to the tectonic and volcanic history of the Basin of Mexico.Paleoclimate records from lacustrine deposits in terrestrial settings typically span the Holocene and only rarely have extended much deeper in time than the Last Glacial Maximum. Recent interest in lake drilling has begun to change this, with successful programs in Bear Lake (US), Valles Caldera (US), Peten Itza (Guatemala), Titicaca (Bolivia/Peru), Malawi (East Africa) and Bosumtwi (Ghana), and El'gygytgyn (Siberia) among others. The climate record from Chalco should provide insights on regional responses to past changes in coupled climate systems. For example, the processes that induce and propagate millennial-scale climate shifts (e.g the Dansgaard-Oeschger and Heinrich events) remain controversial; settling these controversies requires continuous high-resolution climate records from many areas of the planet, including tropical North America, where such information is lacking. In addition, Middle to Late Pleistocene interglacial conditions are of particular interest as possible analogs for the Holocene. Evidence from Antarctic ice cores document significant differences in atmospheric pCO2 and climate change over the Middle Pleistocene, but high-resolution continental records spanning this interval are rare globally and absent in North America. The full Chalco record has the potential to provide unique information that will fill these critical gaps, improving our understanding of our present interglacial and its future course.Broader impactsThis project provides opportunities for graduate and undergraduate student training and takes advantage of ongoing collaborations with Mexican colleagues, fostering collaboration among scientific communities in the U.S. and Mexico.This work obtains records that provide insights on climate and hydrological balance that have implications for resource management and regional planning. The sedimentary archive in Chalco contains information that is directly relevant to one of the most densely populated urban centers on our planet. Mexico City, home to over 17 million inhabitants, is built primarily on lacustrine sediments of the Basin of Mexico that were exposed when waters that fed the lakes were diverted for agriculture after the European conquest. Continued withdrawal of groundwater from aquifers associated with these lacustrine sediments is a major cause of subsidence. Knowledge of past change in hydrological balance will inform our understanding of regional water resource availability.