Determining the Duration of the Ediacaran Shuram C-isotope Excursion using Rock Magnetic Cyclostratigraphy

使用岩石磁旋回地层学确定埃迪卡拉舒拉姆 C 同位素偏移的持续时间

• 批准号: 1322002
• 负责人: Kenneth Kodama
• 金额: $ 21.58万
• 依托单位: Lehigh University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-08-15 至 2018-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1322002&HistoricalAwards=false
• 关键词: Determining; Duration; Ediacaran; Shuram; isotope

Determining the Duration of the Ediacaran Shuram C-isotope Excursion using Rock Magnetic CyclostratigraphyPI: Kenneth P. Kodama, Lehigh University, EAR-1322002ABSTRACTThis award is designated as an OIIA/ISE Global Venture Fund Award and is being co-funded by NSF's OIIA International Science and Engineering Section. This project will develop high-resolution time sequences, or chronostratigraphies, for the sedimentary rocks that carry a record of the Ediacaran (~555 Ma) Shuram negative carbon isotope excursion at two distant localities, one in South China and the other in South Australia. The chronostratigraphies will be determined by a new technique, rock magnetic cyclostratigraphy, which can detect global climate cycles that are driven by variations in the magnitude and direction of Earth's axial tilt and the ellipticity of Earth's orbit around the Sun. The astronomically-forced global climate cycles have been very regular throughout Earth history, so they provide a high-resolution metronome to develop time sequences for sedimentary rocks. The rock magnetic chronostratigraphies should provide up to 15,000 year resolution for the duration of the Shuram carbon isotope excursion recorded by the Doushantuo Formation in South China and by the Wonoka Formation in South Australia, both marine, silt-carbonate sedimentary rocks. Magnetizations applied in the laboratory to samples collected at close stratigraphic spacing (10-30 cm) will measure variations in the concentration of depositional magnetic minerals in the rocks. PIs previous work shows that the magnetic mineral concentration variations can record astronomically-forced global climate cycles. Oriented samples will also be collected from the Wonoka and Doushantuo rocks for standard paleomagnetic analysis to detect polarity reversals of the Earth's magnetic field. The reversal stratigraphy developed will help constrain the duration of the rock magnetically detected cycles to ensure they are astronomically-forced climate cycles. Comparing the rock magnetic cyclostratigraphies from two widely separated localities will provide a strong test of the primary nature of the Shuram carbon isotope excursion. Post-depositional alteration of the rocks is one explanation for the Shuram excursion. Identical high-resolution durations for the excursion in Australia and China would support a primary origin and would bolster the interpretation that the Shuram excursion is a singular event in Earth history and resulted from the oxidation of the world ocean just before life exploded into multi-cellular diversity. The development of the rock magnetic cyclostratigraphy technique for Ediacaran rocks that will result from this project will afford higher resolution relative time assignment for these ancient rocks than afforded by current geochronological techniques.

确定使用岩石磁性旋转式典型播放的Ediacaran Shuram C同位素探索的持续时间：Lehigh University，Lehigh University，Lehigh University，EAR-1322002Abstractthis Award被指定为OIIA/ISE ISE全球风险基金奖，并由NSF的OIIA国际科学和发电机部分共同资助。 该项目将开发出高分辨率的时间序列或年级地层图，以纪念Ediacaran（〜555 MA）Shuram负碳同位素偏移的记录，在中国南部，另一个在南澳大利亚。年度地层学将由一种新技术，即岩石磁环质地层学决定，该技术可以检测到由地球轴向倾斜的大小和方向驱动的全球气候循环，以及围绕太阳的地球轨道的椭圆形。在整个地球历史上，天文自然的全球气候周期一直很规律，因此它们提供了高分辨率的节拍器来开发沉积岩石的时间序列。岩石磁性年级地层图应在中国南部的杜桑图（Doushantuo）地层和南澳大利亚州的WONOKA组记录的Shuram碳同位素游览期间最多可提供15,000年的分辨率，包括海洋，锡尔特 - 碳酸盐沉积岩石。实验室中应用于在近距地层间距（10-30 cm）中收集的样品中的磁化将测量岩石中沉积磁矿物质浓度的变化。 PIS先前的工作表明，磁性矿物质浓度变化可以记录天文造成的全球气候周期。也将从Wonoka和Doushantuo岩石中收集定向样品，以进行标准的古磁分析，以检测地球磁场的极性逆转。开发的逆向地层将有助于限制磁磁检测到的循环的持续时间，以确保它们是天文自然的气候周期。比较来自两个广泛分开的地方的岩石磁性环地层图将提供对Shuram碳同位素偏移的主要性质的强烈检验。岩石的沉积后变化是Shuram游览的一种解释。在澳大利亚和中国游览的相同高分辨率持续时间将支持主要起源，并会加强这样的解释：Shuram游览是地球历史上的一个奇异事件，是由于世界海洋的氧化而造成的，就在生命中爆炸为多细胞多样性之前。 岩石磁性环地层技术针对该项目产生的Ediacaran岩石的开发将为这些古老的岩石提供更高的分辨率相对时间分配，而不是当前的年代学技术所提供的。