Analyses of New High Resolution MCS Data from Guaymas Basin, Gulf of California

本研究旨在了解当沉积物被注入温度约为1000 ° C的岩浆岩床侵入时，沉积物中释放的碳量，如CO2和甲烷。 这一理解与现代气候以及全球范围的碳预算有关。 与现代气候的相关性与古新世/始新世热最大值有关，这是一个快速大气变暖的时期，被认为是现代快速变暖的最佳古代模拟。 古新世/始新世事件被假设为已被驱动的快速和大量的碳从沉积物侵入火成岩岩床在区域性的大岩浆事件的时间周围的格陵兰岛和欧洲之间的北大西洋的开放。 确定火成岩岩床侵入沉积物和碳从这些沉积物释放到海洋和潜在的大气之间的关系，将有助于确定岩床假设下可用于造成快速变暖的碳量，并可与现代大气碳输入进行比较。 此外，现今存在许多活跃的岩浆系统，它们涉及岩床侵入富含有机物的沉积物，这些沉积物通常被认为是稳定的碳汇。 这项工作的更广泛影响包括了解碳从这些岩浆系统的沉积物中重新引入海洋并可能进入大气，这是目前全球碳循环模型所缺少的。另一个影响是支持国际海洋发现计划的一个钻探腿，这是国家科学基金会和国际社会的一项重大投资，旨在通过钻探海底并检查岩石和沉积物及其地层学和岩性关系来了解地球系统的行为。这项研究将分析一个新的高分辨率多道地震数据集从瓜伊马斯盆地在加州湾，以促进我们的沉积物蚀变的过程中响应火成岩岩床入侵的理解。 这项工作有两个主要目标：（1）将新的高分辨率数据整合到基于低频6公里拖缆地震数据的分析中，旨在量化火成岩岩床厚度与上覆沉积物蚀变之间的关系。新的数据将使我们能够自信地确定薄至12米的岩床，并为拟议中的瓜伊马斯盆地国际海洋发现计划评估潜在的钻探地点。这些新的数据是第一次看到拟议的主要钻探地点和潜在替代地点区域的地壳的第二维。 在区域广泛的岩浆事件期间，火成岩岩床侵入沉积物所驱动的过程越来越多地被用作灭绝事件和全球范围的海洋和大气化学变化的触发因素。 这些假说主要是基于在古代露头中观察到的火成岩岩床的变质光环内沉积物的碳含量的变化，以及从光环中丢失的碳和其他元素也从整个地下系统中丢失并有效地释放到海洋或大气中的假设。 本研究项目支持的瓜伊马斯钻探建议的一个关键目标是了解由于岩床侵入而释放的碳的地下和海底生物/地球化学循环。 本提案的一个关键目标是进一步开展工作，制定反映蚀变强度的地震代用指标，以便将基于岩心的知识扩展到区域范围。 岩床厚度与上覆沉积物中地震速度变化之间的关系可能被证明是一个有用的替代指标，本项目将借助新的高分辨率地震数据，沿着瓜伊马斯盆地现有的长拖缆线进行共址测量。 长拖缆数据提供了估计接触变质作用引起的沉积物性质（地震速度）变化的手段，而高分辨率数据提供了估计岩床厚度的手段，岩床厚度与侵入体的可用热能成比例。

This research aims to understand the amount of carbon released from sediments, as CO2 and methane, when those sediments are intruded by magmatic sills with injection temperatures of ~1000°C. This understanding has relevance for modern day climate and also for global-scale carbon budgets. The relevance to modern day climate is related to the Paleocence/Eocene thermal maximum, a period of rapid atmospheric warming, thought to be the best ancient analogue to rapid present-day warming. The Paleocence/Eocene event is hypothesized to have been driven by the rapid and voluminous release of carbon from sediments intruded by igneous sills during a regionally large magmatic event around the time of the opening of the North Atlantic between Greenland and Europe. Defining relationships between igneous sill intrusion into sediments and carbon release from those sediments into the ocean and potentially the atmosphere will help place bounds on the volume of carbon available to create the rapid warming under the sill hypothesis and can be compared to modern atmospheric carbon inputs. In addition, many active magmatic systems exist in the present day that involve sill intrusion into organic-rich sediments, units that have generally been thought of as stable carbon sinks. Broader impacts of the work include understanding the reintroduction of carbon into the ocean and potentially into the atmosphere from sediments in these magmatic systems, something that is presently missing from global carbon cycle models. An additional impact is the support of a drilling leg of the International Ocean Discovery Program, a major NSF and international investment in understanding how the Earth system behaves by drilling into the seafloor and examining the rocks and sediments and their stratigraphy and lithologic relationships. The research will analyze a new high-resolution multi-channel seismic dataset from Guaymas Basin in the Gulf of California in order to advance our understanding of the processes of sediment alteration in response to igneous sill intrusion. The work has two main goals: (1) integration of the new high-resolution data into analyses based on lower-frequency 6-kilometer streamer seismic data aimed at quantifying relationships between igneous sill thickness and alteration of overlying sediments. The new data will enable us to confidently identify sills as thin as 12m and evaluate potential drilling sites for the proposed International Ocean Discovery Program in the Guaymas Basin. These new data are the first that look at the second dimension of the crust in the area of the proposed main drill sites and potential alternate sites. Processes driven by the intrusion of igneous sills into sediments during regionally extensive magmatic episodes are increasingly being invoked as triggers for extinction events and global-scale changes in oceanic and atmospheric chemistry. These hypotheses are largely founded on changes in the carbon content of sediments within metamorphic aureoles of igneous sills observed in ancient outcrops and the assumption that carbon and other elements lost from the aureoles are also lost from the entire subsurface system and efficiently released into the ocean or atmosphere. A key objective of the Guaymas drilling proposal, which this research project supports, is to understand the subsurface and seafloor bio/geochemical cycling of carbon released due to sill intrusion. A key objective of the present proposal is to further the work of developing seismic proxies for alteration intensity that can extend knowledge, based on drill cores, to regional scales. Relationships between sill thickness and changes in seismic velocity within overlying sediments may prove to be a useful proxy, and this project will make co-located measurements along existing long-streamer lines in Guaymas Basin with the aid of the new hi-resolution seismic data. The long-streamer data provide the means to estimate changes in sediment properties (seismic velocity) due to contact metamorphism, while the high-resolution data provide a means to estimate sill thickness, which scales with the available thermal energy of the intrusion.