A meta-analysis of the Steptoean Positive Carbon Isotope Excursion: The SPICEraq database
A meta-analysis of the Steptoean Positive Carbon Isotope Excursion: The SPICEraq database
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DOI：
10.1016/j.earscirev.2020.103442
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发表时间：
2021
影响因子：
12.1
通讯作者：
M. Pulsipher;J. Schiffbauer;M. Jeffrey;J. Huntley;D. Fike;K. Shelton
中科院分区：
文献类型：
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作者：
M. Pulsipher;J. Schiffbauer;M. Jeffrey;J. Huntley;D. Fike;K. Shelton
Steptoean正同位素碳漂移（SPICE）是下古生界一个重要的化学地层学特征。它已被用于全球上寒武统碳酸盐岩地层的对比，并被引用为与Crepicephalus-Aphelaspistrilobite灭绝事件和Sauk II-Sauk III megasequence转换密切相关。尽管全球性的SPICE事件，区域/当地的条件作为一个控制的岩石记录中的SPICE事件的表达。有鉴于此，为了更好地了解SPICE事件作为化学地层学对比工具的可靠性，我们创建了“SPICEraq”数据库，该数据库包括78个含SPICE的剖面，其中包含6669个单独的δ 13 C分析。在这项研究中，我们定量评估SPICE记录的变化，并记录，而漂移是一个全球性的签名，其地层表达的影响，如古纬度，古大陆，水深和相等条件。虽然SPICE偏移的幅度基本一致（增加约4‰），但δ 13 C峰值变化很大（范围为+0.35至+5.87‰）。具体而言，位于30和60°S paleolatitude之间的部分约。500 Ma记录的δ 13 C值较低古纬度低约1 ~ 2‰。沉积在浅水深度和相的剖面记录的δ 13 C值也低于中、深水相;深水相在SPICE峰值和偏移后显示出最富集的13 C碳酸盐。偏移的地层厚度变化很大，范围从<3到~884 m，并且受到本研究中研究的所有分类变量的显著影响。本研究记录了SPICE上升支之前，75%的SPICE前收集数据的切片中δ 13 C出现了小的负偏移。虽然32%的剖面在SPICE峰值期间记录到δ 13 C平台，但其在δ 13 C记录中的存在似乎不受本文研究的任何环境条件的影响。总之，这些分析表明，区域/当地条件影响δ 13 C记录的地层表达，因此应注意使用可靠的定量措施来比较和关联偏移。
The Steptoean Positive Isotopic Carbon Excursion (SPICE) is a prominent chemostratigraphic feature in the Lower Paleozoic. It has been used to correlate Upper Cambrian carbonate strata globally, and is cited as intimately linked to theCrepicephalus-Aphelaspistrilobite extinction event and the Sauk II-Sauk III megasequence transition. Despite the global nature of the SPICE event, regional/local conditions serve as a control on the expression of the SPICE event in the rock record. In light of this, and to better understand how reliable the SPICE event is as a chemostratigraphic tool for correlation, we have created the “SPICEraq,” a database comprising 78 SPICE-bearing sections containing 6669 individual δ13C analyses. In this study, we quantitatively evaluate the variability in SPICE records, and document that, while the excursion is a global signature, its stratigraphic expression is influenced by such conditions as paleolatitude, paleocontinent, water depth, and facies. While the magnitude of the SPICE excursion is generally consistent (an ~4‰ increase), the peak δ13C values are quite variable (ranging from +0.35 to +5.87‰). Specifically, sections located between 30 and 60°S paleolatitude ca. 500 Ma record δ13C values ~1 to 2‰ lower than those from lower paleolatitudes. Sections deposited in shallow water depths and facies also record lower δ13C values than intermediate and deep-water facies; the deep-water facies exhibit the most13C-enriched carbonates at the peak of the SPICE and post-excursion. The stratigraphic thickness of the excursion varies widely, ranging from <3 to ~884 m, and is significantly impacted by all categorical variables investigated in this study. This study documents that the rising limb of the SPICE is immediately preceded by a small negative δ13C excursion in 75% of sections with data collected pre-SPICE. While 32% of sections record a δ13C plateau during peak SPICE, its presence in the δ13C record does not appear to be influenced by any environmental conditions investigated herein. Altogether, these analyses indicate that regional/local conditions impact the stratigraphic expression of δ13C records, and thus care should be taken to use robust, quantitative measures to compare and correlate excursions.