New high-resolution organic (δ¹³C_org) and carbonate (δ¹³C_carb) carbon isotope data from middle shelf deposits in southeastern Iowa demonstrate decoupled signals during the onset of the Hangenberg Event and across the Devonian-Carboniferous Boundary. High-resolution sampling captures a transient negative excursion in δ¹³C_org during the initiation of rising δ¹³C_carb values at the onset of the Hangenberg Event that ends prior to the onset of the final rise in δ¹³C_carb to values greater than +6.0‰ in the Louisiana Limestone. This negative excursion in δ¹³C_org is coincident with a significant increase in Total Organic Carbon (TOC) content in the underlying English River Formation, which likely corresponds to the well-known Hangenberg Black Shale of the classical European sections. The complex behavior of the carbon isotope record recovered here, combined with recently published geochemical data from classical European sections, demonstrate that a succession of geochemical events took place during the initiation of this global biogeochemical event that include a negative excursion in both δ¹³C_carb and δ¹³C_org prior to the major positive carbon isotope excursion, and that the role of organic carbon burial in this Devonian Oceanic Anoxic Event (OAE) extends well beyond the depositional interval of the Hangenberg Black Shale.

来自爱荷华州东南部中陆架沉积物的新高分辨率有机 (δ ¹³ C _org ) 和碳酸盐 (δ ¹³ C _carb ) 碳同位素数据表明，在汉根伯格事件开始期间和穿过泥盆纪-石炭纪边界时，出现了解耦信号。高分辨率采样捕获了在汉伯格事件开始时δ ¹³ C_{碳水化合物}值开始上升期间δ ¹³ C _org的瞬态负偏移，该事件在 δ ¹³ C _carb最终上升开始之前结束，值大于+6.0‰ 在路易斯安那石灰岩中。δ ¹³ C 的负偏移_org与潜在的英国河流地层中总有机碳 (TOC) 含量的显着增加相吻合，这可能对应于经典欧洲部分著名的汉伯格黑页岩。此处恢复的碳同位素记录的复杂行为，结合最近公布的欧洲经典剖面地球化学数据，表明在这一全球生物地球化学事件开始期间发生了一系列地球化学事件，其中包括 δ ¹³ C_{碳水化合物}的负偏移和 δ ¹³ C _org 在主要的碳同位素正偏移之前，有机碳埋藏在泥盆纪大洋缺氧事件 (OAE) 中的作用远远超出了汉伯格黑页岩的沉积区间。