The existence of freshwater ferromanganese concretions has been known for decades, but we are not aware of a generally accepted explanation for their formation, and there has been little research into their potential use as records of Holocene climate and paleohydrology. A conceptual model is presented to describe the environmental and geochemical processes which result in the formation and growth of freshwater ferromanganese concretions. In order to evaluate their potential as historical geochemical records, a concretion from Magaguadavic Lake, New Brunswick, Canada is the focus of a detailed geochronological and geochemical investigation. The radiocarbon data provide a coherent growth curve and a maximum age for the concretion of 8448 ± 43 years, consistent with the establishment of Magaguadavic Lake as a stable post-glacial lacustrine system. The data suggest accretion rates of 1.5 and 3.4 mm per 1000 years during the Northgrippian and Meghalayan stages of the Holocene, respectively. The abrupt change in growth rate observed at the stage boundary may be an indicator of Holocene climate change. These features are consistent with inferences from previous research that warmer climate in the Northgrippian led to eutrophication in some lakes in eastern North America. The results confirm that freshwater Fe–Mn concretions may yield important information about past climatic and environmental conditions.

淡水锰铁矿固结物的存在已有数十年的历史了，但我们尚不知道其形成的普遍接受的解释，而且很少有人对其潜在用途作为全新世气候和古水文学的记录进行研究。提出了一个概念模型来描述环境和地球化学过程，这些过程导致淡水锰铁矿的形成和生长。为了评估它们作为历史地球化学记录的潜力，来自加拿大新不伦瑞克省Magaguadavic湖的凝结物是详细的地球年代和地球化学研究的重点。放射性碳数据提供了连贯的生长曲线，最大固结年龄为8448±43岁，这与将Magaguadavic湖建立为稳定的冰川后湖相系统相一致。数据表明，在全新世的北格里普期和Meghalayan阶段，每1000年的增生速率分别为1.5和3.4 mm。在阶段边界观察到的增长率的突然变化可能是全新世气候变化的指示。这些特征与先前研究得出的结论一致，即Northgrippian地区气候变暖导致北美东部某些湖泊富营养化。结果证实淡水Fe–Mn固结物可能会提供有关过去的气候和环境条件的重要信息。这些特征与先前研究得出的推论一致，即诺斯grippian气候变暖导致北美东部某些湖泊富营养化。结果证实淡水Fe–Mn固结物可能会提供有关过去的气候和环境条件的重要信息。这些特征与先前研究得出的结论一致，即Northgrippian地区气候变暖导致北美东部某些湖泊富营养化。结果证实淡水Fe–Mn固结物可能会提供有关过去的气候和环境条件的重要信息。