Guadalupian carbon isotope stratigraphy indicates extended interval of carbon cycle stability

IF 1.9 3区 地球科学 Q3 GEOSCIENCES, MULTIDISCIPLINARY
S. Arefifard, J. Payne, M. Rizzi
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引用次数: 0

Abstract

Stratigraphic variations in the carbon isotope composition of marine limestones (δ13Ccarb) have been widely reported from the Guadalupian, particularly in the uppermost Capitanian, but the extent to which they reflect global carbon cycle dynamics remains in dispute. Resolving these uncertainties is critical for interpreting the dynamics of the carbon cycle during the Guadalupian as well as for testing hypothesized circumstances of the marine extinction event during the Capitanian (latest Guadalupian). To assess the local versus global causes of stratigraphic variations in δ13Ccarb, here we report δ13Ccarb values from Guadalupian strata in the Hambast Valley, Abadeh region, southwest Iran, in two sections. We then compare the data from the two sections (Abadeh-1 and Abadeh-2) to data from numerous other well-studied sections that were distant from central Iran at the time of deposition. In the Hambast sections, there are broad excursions of δ13Ccarb, of up to 3‰. However, the δ13Ccarb values do not show any remarkable shifts across the Wordian/Capitanian or Capitanian/Wuchiapingian boundaries in the Abadeh-1 section. An excursion occurs near the Capitanian/Wuchiapingian boundary in the Abadeh-2 section but is associated with elemental and oxygen-isotope evidence for diagenetic resetting. The lack of reproducibility in the δ13Ccarb shifts between the two studied sections at Abadeh and evidence for diagenetic resetting in association with negative excursions are consistent with evidence from other, previously reported, study sites that negative excursions can be accounted for by local primary or diagenetic factors and do not require any global perturbation of the carbon cycle through this interval. When carbonate values are compared with previously published organic carbon isotope data and carbonate sections are compared for shared isotope features, the primary global signal that is supported by the data is one of stable and relatively heavy values of δ13Ccarb in marine limestone during the Guadalupian.
瓜达鲁阶碳同位素地层学表明碳循环稳定性的时间间隔延长
Guadalupian,特别是最上层的Capitanian,已经广泛报道了海洋石灰岩碳同位素组成(δ13Carb)的地层变化,但它们在多大程度上反映了全球碳循环动力学仍存在争议。解决这些不确定性对于解释瓜达卢皮期碳循环的动力学以及测试凯德期(最新的瓜达卢皮期)海洋灭绝事件的假设情况至关重要。为了评估δ13Carb地层变化的局部和全球原因,我们在这里分两个部分报告了伊朗西南部阿巴德地区哈姆巴斯特山谷的Guadalupian地层的δ13carb值。然后,我们将两个剖面(Abadeh-1和Abadeh-2)的数据与沉积时远离伊朗中部的许多其他经过充分研究的剖面的数据进行比较。在Hambast剖面中,δ13Carb的偏移幅度很大,高达3‰。然而,在Abadeh-1剖面中,δ13Carb值在Wordian/Capitanian或Capitanian/Wuchiapingian边界上没有显示出任何显著的变化。Abadeh-2剖面的Capitanian/Wuchiapangian边界附近发生偏移,但与成岩重置的元素和氧同位素证据有关。Abadeh两个研究剖面之间的δ13Carb位移缺乏再现性,以及与负偏移相关的成岩重置证据与先前报道的其他证据一致,研究地点认为,负偏移可以由局部原生或成岩因素解释,并且不需要对该区间的碳循环进行任何全球扰动。当将碳酸盐数值与先前公布的有机碳同位素数据进行比较,并将碳酸盐剖面与共有同位素特征进行比较时,该数据支持的主要全球信号是瓜达卢皮期海洋石灰岩中δ13Carb的稳定且相对较重的值之一。
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来源期刊
American Journal of Science
American Journal of Science 地学-地球科学综合
CiteScore
5.80
自引率
3.40%
发文量
17
审稿时长
>12 weeks
期刊介绍: The American Journal of Science (AJS), founded in 1818 by Benjamin Silliman, is the oldest scientific journal in the United States that has been published continuously. The Journal is devoted to geology and related sciences and publishes articles from around the world presenting results of major research from all earth sciences. Readers are primarily earth scientists in academia and government institutions.
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