EAGER: Early-mid Pliocene Climate Change in Northern Chile

戈弗雷/罗格斯大学-1117496这一早期概念的探索性研究的目的是确定奥帕奇形成的气候意义，碳酸盐岩单位之间的780万和337万年前沉积在智利北部北方的阿塔卡马沙漠。阿塔卡马中部和东部安第斯山脉的降雨量受到厄尔尼诺、太平洋十年涛动和南美季风的长期影响。奥帕奇由两个碳酸盐相组成，一个是由盆地溢出形成的层状凝灰岩，另一个是沼泽单元。这项研究的目的是重建气候（水文平衡）的沉积特征，如薄层厚度。研究人员认为，每年有两个带沉积，季节性周期大约每17年加强一次，但他们希望证明每年有两个纹层形成，并与气候直接相关。卡拉马盆地沉积的沼泽碳酸盐岩单元将用于推断该地区在气候重组时期的长期气候，这项建议将侧重于现代类似物，以帮助解释岩石记录。奥帕奇是独特的中部安第斯山脉方面，其规模，而不是形成机制。在30公里范围内，活跃的碳酸盐沉积发生在Rio Loa和附近的地下水泉以及高海拔湖泊中，两者都可以为Opache相的形成提供重要的见解。除了从薄片上研究沉积物组构外，研究人员还将使用稳定同位素来限制对CO2的动力学影响，如脱气。这些现代模拟研究的年代测定将利用Ra-226（半衰期1599年），结合罗格斯大学的U-Th年代测定。纹层的旋回性可以通过计算活跃生长面的定年层位并与气候资料相比较来确定。EAGER的建议包括增加了U-Pb分层单元的日期，将该技术带到了Rutgers.成功地测试了十年气候记录是可能的这一假设，将导致提交一份完整的建议，该建议将产生一个受ENSO影响的地区的上新世早中期罕见的大陆十年气候记录。该项目将包括本科生参与国际研究，并与罗格斯大学合作，扩大他们的研究经验。研究人员对从现代模拟研究中提取最近的气候记录寄予厚望。

Godfrey/EAR-1117496/Rutgers UniversityThe aim of this early-concept proposal for exploratory research is to determine the climate significance of the Opache formation, a carbonate rock unit deposited in the Atacama Desert of northern Chile between ~7.8 and 3.37 million years ago. Rainfall in the Atacama, both in its central area and in the Andes to its east, is strongly influenced by El Niño, the Pacific Decadal Oscillation, and on longer timescales by the South American monsoon. The Opache is made up of two carbonate facies, a laminated tufa which formed from basin over-spill and a palustrine unit. The aim of this study is to reconstruct climate (hydrologic balance) from sedimentological features such as lamina thickness. The investigators believe that two bands were deposited annually with the seasonal cycle strengthening roughly every seventeen years, but they want to demonstrate that two laminae form annually and are directly related to climate. The palustrine carbonate unit deposited in the Calama Basin will be used to infer the long-term climate of the region during a time of climate re-organization.This proposal will focus on modern analogs to aid in interpreting the rock record. The Opache is unique in the central Andes in regard to its size rather than formation mechanism. Within 30 km, active carbonate deposition occurs in and close to the Rio Loa from groundwater springs as well as in high altitude lakes and both can provide important insight to the formation of both Opache facies. In addition to study of sediment fabrics from thin section, the investigators will use stable isotopes to constrain kinetic effects on CO2 such as degassing. Dating for these modern analog studies will utilize Ra-226 (half life 1599 years), combined with U-Th dating at Rutgers. Laminae cyclicity can be determined by counting between dated horizon from active growth surface and compared with recorded climate data. This EAGER proposal includes addition of dates of the laminated unit by U-Pb, bringing the technique to Rutgers.Successful testing of the hypothesis that a decadal climate record is possible will result in a submission of a full proposal which will yield a rare continental decadal climate record from the early-mid Pliocene in a region influenced by ENSO. This project will include undergraduate involvement in international research and collaboration with Rutgers University which broadens their research experience. The investigators have high expectations that a recent climate record will be extracted from the modern analog studies.