The balance between degradation and preservation of sedimentary organic carbon (OC) is important for global carbon and oxygen cycles¹. The relative importance of different mechanisms and environmental conditions contributing to marine sedimentary OC preservation, however, remains unclear^{2,3,4,5,6,7,8}. Simple organic molecules can be geopolymerized into recalcitrant forms by means of the Maillard reaction⁵, although reaction kinetics at marine sedimentary temperatures are thought to be slow^9,10. More recent work in terrestrial systems suggests that the reaction can be catalysed by manganese minerals^11,12,13, but the potential for the promotion of geopolymerized OC formation at marine sedimentary temperatures is uncertain. Here we present incubation experiments and find that iron and manganese ions and minerals abiotically catalyse the Maillard reaction by up to two orders of magnitude at temperatures relevant to continental margins where most preservation occurs⁴. Furthermore, the chemical signature of the reaction products closely resembles dissolved and total OC found in continental margin sediments globally. With the aid of a pore-water model¹⁴, we estimate that iron- and manganese-catalysed transformation of simple organic molecules into complex macromolecules might generate on the order of approximately 4.1 Tg C yr⁻¹ for preservation in marine sediments. In the context of perhaps only about 63 Tg C yr⁻¹ variation in sedimentary organic preservation over the past 300 million years⁶, we propose that variable iron and manganese inputs to the ocean could exert a substantial but hitherto unexplored impact on global OC preservation over geological time.

沉积有机碳 (OC) 的降解和保存之间的平衡对于全球碳和氧循环非常重要¹。然而，不同机制和环境条件对海洋沉积物有机碳保存的相对重要性仍不清楚^{2,3,4,5,6,7,8}。简单的有机分子可以通过美拉德反应⁵聚合成顽固的形式，尽管海洋沉积温度下的反应动力学被认为是缓慢的^9,10。最近在陆地系统中的研究表明，该反应可以由锰矿物催化^11,12,13，但在海洋沉积温度下促进地质聚合 OC 形成的潜力尚不确定。在这里，我们进行了孵化实验，发现铁、锰离子和矿物质在与大陆边缘相关的温度下非生物催化美拉德反应高达两个数量级，而大陆边缘是大多数保存发生的地方⁴。此外，反应产物的化学特征与全球大陆边缘沉积物中发现的溶解的有机碳和总有机碳非常相似。借助孔隙水模型¹⁴，我们估计铁和锰催化的简单有机分子向复杂大分子的转化可能会产生大约 4.1 Tg C yr ^-1的数量级，以便在海洋沉积物中保存。在过去 3 亿年中沉积物有机保存可能仅发生约 63 Tg C yr ^-1变化6的背景下，我们提出，海洋中不同的铁和锰输入可能会对全球 OC 保存产生重大但迄今为止尚未探索的影响。地质时间。