Astrochronology depends on the faithful record of insolation forcing in climatic proxies, including the carbon isotope composition measured on bulk carbonates (δ¹³C_carb). In marginal basins close to carbonate platforms, the source of carbonate is varied, which can impact the record of the astronomical cycles in the δ¹³C_carb signal. We compare here the δ¹³C_carb values together with detrital and weathering proxies before and during a crisis in the platform carbonate production (Weissert event, Valanginian, ~135 Ma) to document how a change in the carbonate source can affect the record of the orbital forcing by the carbon isotope system. The level of burial diagenesis was insufficient to alter the clay mineral assemblages, which are linked to cyclic changes in weathering conditions. The δ¹³C_carb values correspond to the values measured in other parts of the basin, which experienced various levels of burial diagenesis, suggesting that they also reflect a paleoenvironmental signal. In marl beds, the δ¹³C_carb values increase with detrital and kaolinite content, suggesting that humid/arid cycles controlled the evolution of the δ¹³C_carb signal in marl beds. Before the Weissert event, the δ¹³C_carb values in the limestone beds increase with CaCO₃ content and arid conditions. This can reflect the change of type of carbonate produced in shallow‐marine environments and exported to the basin. These environmental changes disrupted the record of the eccentricity cycles in the δ¹³C_carb signal. The sources of carbonate must therefore be clearly identified and documented before using the δ¹³C_carb series for orbital tuning in hemipelagic areas close to carbonate platforms.

中文翻译：

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碳循环对中生界周缘边缘盆地中轨道强迫的反演：对天文学的意义

Astrochronology取决于日照气候中代理，包括散装碳酸盐（δ测得的碳同位素组成迫使忠实记录¹³ Ç_{碳水化合物}）。在边缘盆地接近碳酸盐平台，碳酸盐源是变化的，它可以在δ影响天文周期的记录¹³ Ç_{碳水化合物}信号。在这里，我们比较δ ¹³ C ^_{碳水化合物}在平台碳酸盐生产发生危机之前和期间（Weissert事件，Valanginian，〜135 Ma），利用数值和碎屑和风化代理来记录碳酸盐源的变化如何影响碳同位素系统的轨道强迫记录。埋藏成岩作用的程度不足以改变粘土矿物组合，而粘土矿物组合与风化条件的周期性变化有关。的δ ¹³ C ^_{碳水化合物}值对应于在盆地，其经历了埋藏成岩作用的各种级别的，这表明它们也反映古环境信号的其它部分测量的值。在泥灰岩张床位，δ ¹³ C ^_{碳水化合物}值与碎屑和高岭石含量增加，这表明湿润/干燥循环控制δ的演变¹³ Ç_{碳水化合物}信号在泥灰岩床。在Weissert事件之前，δ ¹³ C ^_{碳水化合物}在灰岩值与碳酸钙增加₃含量和干旱条件。这可以反映出浅海环境中产生并输出到盆地的碳酸盐类型的变化。这些环境变化扰乱了偏心周期的记录中δ ¹³ Ç_{碳水化合物}信号。碳酸酯的来源，因此必须清楚地识别和记录使用δ之前¹³ Ç_{碳水化合物} 系列在碳酸盐台地附近的半海域进行轨道调谐。