Silurian graptolite biofacies on Arctic Canada: taxonomy, biostratigraphy, biogeography, paleoenvironments and evolution

加拿大北极地区志留纪笔石生物相：分类学、生物地层学、生物地理学、古环境和演化

• 批准号: 4236-2008
• 负责人: Lenz, Alfred
• 金额: $ 1.09万
• 依托单位: University of Western Ontario
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2011
• 资助国家: 加拿大
• 起止时间: 2011-01-01 至 2012-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=473810
• 关键词: Silurian; graptolite; biofacies; Arctic; Canada

The Silurian (~445 to 415 million years) of the Canadian Arctic Islands, as elsewhere in the then-existing world, were occupied by many unusual organisms, including one dominant group of very abundant marine plankton animals, the graptolites. Graptolites evolved very rapidly and through the Silurian existing species disappeared and new species appeared very frequently, making them excellent fossils to subdivide the Silurian geologic column into many fine time slices, a procedure known as biostratigraphy. The graptolites of the Arctic Islands while continuous through the entire Silurian rock sequence, as is normal elsewhere, are virtually unique in the world in their mode of preservation: their original 3D skeletal material is encased within limestone concretions, and are easily extracted by dissolving the rock in dilute acid, yielding beautifully preserved specimens. As such, the Arctic graptolite sequence is considered to be one of the best in the world. For that reason, I have for years studied, and continue to study, these beautifully preserved graptolites. The procedure for newly recovered material continues as follows: firstly examination of their morphology for new information on their morphology and for species recognition, secondly the continual process of the development and refinement of their biostratigraphy to enable comparison and correlation with the fine time slices of rock elsewhere in the world, and finally from this background to advance the knowledge of their evolutionary history. Graptolites witnessed a number of mass extinctions during the Silurian. One event, well marked in the Arctic, witnessed the abrupt reduction of 50 pre-extinction species to only two post-extinction species, and coincided with a strong drop in sea level, and also with a strong increase Carbon 13. Future studies will examine this in more detail, and extend studies into earlier and later Silurian extinction events, with the goal of better understanding the nature of plankton extinction, and of extinctions in general. Finally, my overriding goal while continuing to learn more about graptolites and their habitats, is to extend that knowledge to help understand the geological and biological history, including climate, of the Arctic Canada during the Silurian Period.

与当时世界上的其他地方一样，加拿大北极群岛的志留纪（约 445 至 4.15 亿年）被许多不寻常的生物占据，其中包括数量非常丰富的海洋浮游动物的一个主要群体——笔石。笔石进化得非常迅速，在志留纪期间，现有物种消失了，新物种频繁出现，使它们成为将志留纪地质柱细分为许多精细时间切片的极好化石，这一过程称为生物地层学。北极群岛的笔石虽然像其他地方一样连续贯穿整个志留纪岩石序列，但其保存方式实际上在世界上是独一无二的：它们原始的 3D 骨骼材料被包裹在石灰岩结核中，并且可以通过将岩石溶解在稀酸中轻松提取，从而产生保存完好的标本。因此，北极笔石序列被认为是世界上最好的序列之一。出于这个原因，我多年来一直在研究并继续研究这些保存完好的笔石。新回收材料的程序如下：首先检查其形态，以获得有关其形态和物种识别的新信息，其次不断发展和完善其生物地层学，以便能够与世界其他地方的岩石的精细时间切片进行比较和关联，最后在此背景下推进对其进化历史的了解。笔石在志留纪期间见证了多次大规模灭绝。北极地区发生的一个事件非常明显，见证了 50 种灭绝前物种突然减少至仅 2 种灭绝后物种，同时海平面大幅下降，碳 13 也大幅增加。未来的研究将对此进行更详细的研究，并将研究扩展到志留纪早期和晚期的灭绝事件，目的是更好地了解浮游生物灭绝和一般灭绝的性质。最后，在继续更多地了解笔石及其栖息地的同时，我的首要目标是扩展这些知识，以帮助了解志留纪时期加拿大北极地区的地质和生物历史，包括气候。