Revisiting the Cambrian Series 1 animal origination chronology

重温寒武纪系列 1 动物起源年表

• 批准号: 2025735
• 负责人: Jessica Creveling
• 金额: $ 37.01万
• 依托单位: Oregon State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-09-01 至 2024-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2025735&HistoricalAwards=false
• 关键词: Revisiting; Cambrian; Series; animal; origination

The oldest shelly sea creatures appeared ~540 million years ago in the ‘Cambrian explosion’. This research seeks to refine the timeline for this captivating evolutionary event. This task is harder than expected because fossils of the same organism appear at different times in different places. How can one tell which of the many fossils of the same species is oldest—and refine its evolutionary timeline—with a sparse chronology for Cambrian marine sediment deposition and fossil occurrences? This research uses a computer program to match up the globally synchronous chemical signals of carbon cycle changes preserved in the rocks hosting Cambrian fossils. Matching the chemical signals from a fossil’s location to the one Cambrian location with many dates will allow these ages to be determined via extrapolation. As most Cambrian fossil organisms are the earliest members of still-living taxonomic phyla, our research promotes the progress of scientific inquiry into the tempo of evolution within and across animal clades. This project will develop open source, interactive software for the broader geological community to align chemical records without the need for advanced coding experience; train one PhD student and three undergraduates in computational research; and develop and distribute curricula, based on this new software, to promote undergraduate quantitative literacy. The chronology for the early Cambrian radiation of small skeletal fossils arises from visual alignment of δ13Ccarb excursions at a U-Pb radiometrically calibrated, fossil barren, stratigraphic section in Morocco to excursions at richly fossiliferous, time uncertain sections elsewhere. Visual δ13Ccarb correlation methods cannot ensure unique alignments, nor a given chronology. This research adopts a dynamic programming algorithm to identify libraries of geologically permissible alignments between fossiliferous stratigraphic sections and the Moroccan δ13Ccarb–U/Pb age model. Each permissible δ13Ccarb alignment will generate a distinct chronology for the local first appearance datum (FAD) of all fossil taxa at a stratigraphic section and, thus, various combinations of local FAD chronologies will yield alternative ages for a taxon’s global FAD. The proposed research explores whether/how alternative global FAD chronologies reveal a different number of origination pulses and alternative ages for pulse initiation and duration, thereby addressing heretofore unacknowledged uncertainty in the earliest Cambrian explosion chronology.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

最古老的贝壳状海洋生物出现在5.4亿年前的“寒武纪大爆发”中。这项研究试图完善这一迷人的进化事件的时间表。这项任务比预期的要困难，因为同一种生物的化石在不同的时间出现在不同的地方。如何通过寒武纪海洋沉积物沉积和化石出现的稀疏年表来判断同一物种的许多化石中哪一个是最古老的，并完善其进化时间表？这项研究使用了一个计算机程序来匹配全球同步的碳循环变化的化学信号，这些信号保存在含有寒武纪化石的岩石中。将化石位置的化学信号与一个寒武纪位置的许多日期相匹配，可以通过外推来确定这些年龄。由于大多数寒武纪生物化石是现存分类门中最早的成员，我们的研究促进了对动物分支内部和跨分支进化速度的科学探索。该项目将为更广泛的地质社区开发开源的交互式软件，以便在不需要高级编码经验的情况下对齐化学记录；培养1名博士生和3名本科生进行计算研究；并在此基础上开发和分发课程，以提高大学生的量化素养。早寒武纪小型骨骼化石的辐射年代学源于对摩洛哥一个U-Pb辐射校准、化石贫瘠的地层剖面的δ13Ccarb偏移与其他地方化石丰富、时间不确定的剖面的偏移的视觉比对。视觉δ13Ccarb相关方法不能确保唯一的排列，也不能确保给定的年代学。本研究采用动态规划算法识别化石地层剖面与摩洛哥δ13Ccarb-U /Pb年龄模型之间的地质允许排列文库。每一种允许的δ13Ccarb对线都将为地层剖面上所有化石分类群的局部首次出现基准（FAD）产生不同的年代学，因此，局部FAD年代学的各种组合将产生一个分类群的全球首次出现基准的不同年龄。本研究拟探讨不同的全球FAD年表是否/如何揭示不同数量的起源脉冲以及脉冲起始和持续时间的不同年龄，从而解决迄今为止在最早寒武纪爆发年表中未被承认的不确定性。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。