High-resolution organic carbon isotope record across the Cretaceous–Tertiary boundary in south-central Alberta: implications for the post-impact recovery rate of terrestrial ecosystems and use of δ13C as a boundary marker
High-resolution organic carbon isotope record across the Cretaceous–Tertiary boundary in south-central Alberta: implications for the post-impact recovery rate of terrestrial ecosystems and use of δ13C as a boundary marker
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艾伯塔省中南部白垩纪-第三纪边界的高分辨率有机碳同位素记录：对陆地生态系统影响后恢复率的影响以及使用 δ13C 作为边界标记
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发表时间：
2007
期刊：
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通讯作者：
D. Zelenitsky
中科院分区：
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作者：
F. Therrien;D. Eberth;D. R. Braman;D. Zelenitsky
一项高分辨率研究发现，在阿尔伯塔中南部Scollard组的两个地点，陆地有机质中的δ 13 C偏移量为-1.8‰至-2.3‰，跨越了白垩纪-第三纪（K-T）边界，Scollard组是陆地环境中K-T边界最北的地点之一。δ 13 C值在K-T界线粘土岩上方6cm处最低，在界线粘土岩上方10 cm处恢复到界线前水平。统计分析表明，在阿尔伯塔的K-T同位素的转变是与跨K-T边界发生的花的变化的性质。一个放射性测年的膨润土休息的边界托管尼维斯煤在一个地方允许我们估计，陆地碳循环恢复10万年后的K-T边界事件，一个值，支持现有的假设，陆地生态系统比海洋生态系统恢复得更快。整个Scollard组的有机碳同位素记录表明，在阿尔伯塔，K-T边界上的δ 13 C偏移没有达到晚马斯特里赫特标准的异常低值。此外，K-T碳同位素位移发生在有限的地层间隔（<10 cm）内，极大地限制了其在陆相沉积环境中保存的可能性。这些观测结果表明，δ 13 C剖面本身对于确定K-T边界（以及可能的其他地质瞬时事件）可能是不可靠的，应该与其他方法（例如，在缺乏界线粘土岩和铱异常的地段，利用孢粉学方法识别K-T界线。简历：一项高分辨率研究，确定了δ 13 C同位素的一次漂移，其中-1.8‰和-2.3‰
A high-resolution study identified a δ 13 C excursion of -1.8‰ to -2.3‰ in terrestrial organic matter across the Cretaceous-Tertiary (K-T) boundary at two localities in the Scollard Formation of south-central Alberta, one of the northernmost occurrences of the K-T boundary in terrestrial settings. δ 13 C values are at their lowest within 6 cm above the K-T boundary claystone and return to pre-boundary levels within 10 cm above the boundary claystone. Statistical analyses reveal that the K-T isotopic shift in Alberta is related to the nature of floral changes that occurred across the K-T boundary. A radiometrically dated bentonite resting on the boundary-hosting Nevis coal at one of the localities permits us to estimate that the terrestrial carbon cycle recovered 100 000 years after the K-T boundary event, a value that supports an existing hypothesis that terrestrial ecosystems recovered more rapidly than marine ecosystems. The organic carbon isotope record of the entire Scollard Formation demonstrates that the δ 13 C excursion across the K-T boundary did not reach anomalously low values by late Maastrichtian standards in Alberta. Furthermore, the occurrence of the K-T carbon isotope shift within a restricted stratigraphic interval (<10 cm) greatly limits the probability of its preservation in the context of terrestrial sedimentary environments. These observations suggest that, on their own, δ 13 C profiles may be unreliable for locating the K-T boundary (and possibly other geologically instantaneous events) and that they should be used in combination with other approaches (e.g., palynology) to identify the K-T boundary in sections lacking the boundary claystone and iridium anomaly. Resume : Une etude de haute resolution a identifie une excursion isotopique δ 13 C varient entre -1.8‰ et -2.3‰ dans