Peatlands, an important organic carbon reservoir, play a crucial role in the global carbon cycle. The carbon accumulation of peatlands, reflected by net primary productivity (NPP), can have an impact on global carbon cycling and climate change. The late Carboniferous - early Permian is an icehouse period, during which numerous thick coal beds were accumulated in the North China Block (NCB) located within a low-latitude area, providing an opportunity for studying the carbon cycling under the glacial and interglacial climates. In this study, spectral analysis was performed on the natural gamma-ray (GR) logs of the Benxi, Taiyuan, and Shanxi formations of the late Carboniferous to early Permian in a borehole section located within the Ordos Basin in western NCB. Cyclic signals related to astronomical orbital parameters were identified, including long eccentricity (∼405 kyr), short eccentricity (∼125 kyr and ∼ 95 kyr), and obliquity (∼35.5 kyr). A floating astronomical time scale was established by using the long eccentricity signal, and this time scale was further used to constrain the durations of the accumulation of coal-forming paleo-peatlands. The paleo-peatland for the C8+9 coal seam (9 m thick) of the Taiyuan Formation lasted approximately 203 kyr, and the paleo-peatland for the C5 coal seam (4 m thick) of the Shanxi Formation lasted approximately 46 kyr. Using this timeframe and an estimation of carbon loss during coalification, the carbon accumulation rates of the late Carboniferous - early Permian low-latitude peatlands are calculated to be 104.7 ± 14.9 g·C·m−2·a−1for the C8+9 coal seam and 192.6 ± 11.6 g·C·m−2·a−1for the C5 coal seam. The NPP of the paleo-peatlands, which deducts a part of the carbon loss caused by the loss of CO2 and CH4, can be calculated from the carbon accumulation rates. The calculated average NPP of the paleo-peatlands for the C8+9 seam was 199 ± 28 g·C·m−2·a−1, and that of the C5 seam was 366 ± 22 g·C·m−2·a−1. In combination with the absolute time scale calibrated by high-precision UPb dates from Palougou section in western NCB, the depositional time of the investigated strata was constrained to be from 300.1 ± 0.5 Ma to 294.3 ± 0.5 Ma. The coal seams of the late Carboniferous to early Permian in the NCB correspond to an interglacial interval around ∼298 Ma. The peatland with a lower NPP corresponds to the warming stage and the peatland with a higher NPP corresponds to the cooling stage. This implies that a lower NPP of paleo-peatland tends to be less efficient in carbon storage, and could not reduce the atmospheric CO2 substantially. In contrast, a higher NPP of paleo-peatland tends to accelerate carbon fixation, leading to temperature decrease and the termination of interglacial interval in early Permian. The results of this study could provide insights into the relationship between the development of paleo-peatlands and the record of the paleoclimates during the same period, and could be helpful for the prediction of future climate change.

中文翻译：

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与石炭纪晚期和二叠纪早期冰室间隔的深时冰期相关的古泥炭地的净初级生产力


泥炭地是重要的有机碳库，在全球碳循环中发挥着至关重要的作用。泥炭地的碳积累，以净初级生产力 （NPP） 反映，会对全球碳循环和气候变化产生影响。石炭纪晚期—早二叠世为冰库期，其间位于低纬度地区的华北区块（NCB）积累了大量厚煤层，为研究冰期和间冰期气候下的碳循环提供了契机。本研究对位于NCB西部鄂尔多斯盆地内钻孔剖面的石炭世晚期至早二叠世本溪、太原和山西组的天然伽马射线（GR）测井进行了光谱分析。确定了与天文轨道参数相关的周期信号，包括长偏心率 （∼405 kyr）、短偏心率 （∼125 kyr 和 ∼ 95 kyr） 和倾斜度 （∼35.5 kyr）。利用长偏心率信号建立了浮动天文时间尺度，该时间尺度进一步用于限制成煤古泥炭地积累的持续时间。太原组 C8+9 煤层（9 m 厚）的古泥炭地持续了约 203 kyr，山西组 C5 煤层（4 m 厚）的古泥炭地持续了约 46 kyr。利用这个时间框架和对煤化过程中碳损失的估计，计算出晚石炭世-早二叠世低纬度泥炭地的碳积累速率为 104.7 ± 14.9 g·C·m−2·a−1 和 192.6 ± 11.6 g·C·m−2·a−1 表示 C5 煤层。 古泥炭地的 NPP 减去 CO2 和 CH4 损失造成的部分碳损失，可以根据碳积累速率计算得出。计算得出的C8+9煤层古泥炭地平均NPP为199 ± 28 g·C·m−2·a−1，C5 煤层的 C5 焊缝为 366 ± 22 g·C·m−2·a−1。结合 NCB 西部 Palougou 剖面高精度 UPb 测年校准的绝对时间尺度，研究地层的沉积时间被限制在 300.1 ± 0.5 马 到 294.3 ± 0.5 马。NCB 中石炭世晚期至二叠世早期的煤层对应于约 ∼298 马 的间冰期间隔。NPP 较低的泥炭地对应于变暖阶段，NPP 较高的泥炭地对应于冷却阶段。这意味着古泥炭地的 NPP 较低，碳储存效率往往较低，并且无法大幅减少大气中的 CO2。相反，古泥炭地NPP越高，碳固定越快，导致二叠世早期温度降低和间冰期间期结束。本研究结果可为古泥炭地发育与同期古气候记录之间的关系提供见解，有助于预测未来的气候变化。