δ13C stratigraphy of the Proterozoic Bylot Supergroup, Baffin Island, Canada: implications for regional lithostratigraphic correlations
δ13C stratigraphy of the Proterozoic Bylot Supergroup, Baffin Island, Canada: implications for regional lithostratigraphic correlations
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DOI：
10.1139/e98-100
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发表时间：
1999-08
影响因子：
1.4
通讯作者：
Linda C. Kah;Anne G. Sherman;G. Narbonne;A. Knoll;A. J. Kaufman
中科院分区：
文献类型：
--
作者：
Linda C. Kah;Anne G. Sherman;G. Narbonne;A. Knoll;A. J. Kaufman
巴芬岛北部的Bylot超群包含约1270至723 Ma之间沉积的bb0 1500 m的台地、陆架和斜坡碳酸盐。有限的年代地层资料使Bylot超群与Laurentia北部和西部主要的新元古代地层序列进行了广泛的对比；然而，由于生物地层学和岩石地层学的限制，详细的对比是不可能的。碳同位素化学地层学是约束这种区域间相关性的潜在数据集。Bylot超群和萨默塞特岛和格陵兰岛西北部大致相同的序列的碳同位素数据显示了明显的δ 13c地层趋势，其中13c的中等富集区间（+3.5±1‰）被略负值（-1.0±1‰）所点缀。尽管与新元古代标准相比，观测到的变化幅度不大，但与劳伦西亚西北部记录的值的差异表明，这些地层描绘了一个离散的沉积层段。同位素值与已发表资料的比较表明，δ 13c值大约在-1.0‰和+4.0‰之间，是~ 1300 ~ ~ 800 Ma区间的特征。这一模式不同于新元古界较年轻的序列，通常记录的值为bb0 +5‰，而较老的中元古界序列记录的值接近0‰，表明这些中等正数值可能有助于广泛的时间对比。新数据和已发表数据的汇编允许对全球中元古代碳同位素曲线进行初步重建。
The Bylot Supergroup, northern Baffin Island, contains >1500 m of platform, shelf, and slope carbonates deposited between ∼1270 and ∼723 Ma. Limited chronostratigraphic data have led to the broad correlation of the Bylot Supergroup with predominantly Neoproterozoic successions in northern and western Laurentia; yet, detailed correlation has been impossible given biostratigraphic and lithostratigraphic limitations. Carbon-isotope chemostratigraphy represents a potential dataset to constrain such interregional correlations. Carbon isotopic data from the Bylot Supergroup and broadly coeval successions from Somerset Island and northwest Greenland reveal distinct stratigraphic trends in δ 13 C, with intervals of moderate 13 C enrichment (+3.5 ± 1‰) punctuated by excursions to slightly negative values (-1.0 ± 1‰). Although the scale of the observed variation is muted relative to Neoproterozoic standards, the dissimilarity of values to those recorded in northwestern Laurentia suggests that these strata delineate a discrete depositional interval. Comparison of isotopic values with published data indicates that δ 13 C values between approximately -1.0 and +4.0‰ are characteristic of the interval between ∼1300 and ∼800 Ma. This pattern is distinct from that of younger Neoproterozoic successions, which typically record values >+5‰, and older Mesoproterozoic successions, which record values near 0‰, and suggests that these moderately positive values may be useful for broad time correlation. Compilation of new and published data permits the tentative reconstruction of a global Mesoproterozoic carbon isotopic curve.