Layered carbonates in Roman aqueducts: a new archive for environmental studies and archaeology

洞穴、凝灰岩、钙华等陆相碳酸盐岩矿床是古气候、古水文的重要档案。最近，在历史上的渡槽中形成的碳酸盐沉积物被认为是这种类型的新的高分辨率档案，具有获得考古信息的额外可能性。渡槽沟道是一种明确的几何结构，其中的碳酸盐沉积比天然淡水碳酸盐沉积更容易理解和建模。从历史渡槽中更好地了解碳酸盐沉积物的分层对于探索其在高分辨率古环境和考古研究中的全球潜力至关重要。在之前对土耳其罗马渡槽的研究中，我们的小组已经表明，稳定同位素可以用来识别沉积物中的年度分层，即使在冬季致密、粗晶和夏季细晶、多孔方解石的典型岩相交替不清晰可见或不复杂的情况下。我们建议扩展这种方法，使这种新的高分辨率档案更广泛地适用于其他气候带和所有类型的水源。这将通过在法国南部一个新的气候区（弗莱姆贾斯和卡奥尔）调查两条罗马渡槽来实现。夏季和冬季沉积物和其他分层的确切性质将通过对两条渡槽沿线的一系列碳酸盐样本的综合分析，通过监测这些渡槽的泉水，以及监测仍在运作的古水道中的碳酸盐生长情况来调查。本研究涉及淡水碳酸盐岩沉积机制、古气候、岩石微结构、淡水微生物学、水资源、历史工程、考古学等多学科交叉研究。天然淡水陆相碳酸盐岩也是重要的油气储集岩，具有日益重要的经济意义。洞穴、凝灰岩、钙华等陆相碳酸盐岩矿床是研究古气候、古水文的重要档案。近年来，在历史上的渡槽中形成的碳酸盐沉积物被认为是这种类型的新的高分辨率档案，具有获得考古信息的额外可能性。渡槽沟道是一种明确的几何结构，其中的碳酸盐沉积比大多数天然淡水碳酸盐沉积更容易理解和建模。从历史渡槽中更好地了解碳酸盐沉积物的分层对于探索其在高分辨率古环境和考古研究中的全球潜力至关重要。在之前对土耳其罗马渡槽的研究中，我们的研究小组已经证明，稳定的氧和碳同位素可以用来识别年分层，即使在宏观和微观上不能清楚地看到冬季致密、粗晶和夏季细晶、多孔方解石的典型岩石学交替。为了使这个新的高分辨率档案更广泛地适用于其他气候带和其他类型的水源，我们建议扩展这种方法。这将通过调查法国南部另一个气候带的三条罗马渡槽（bsamziers， frsamjus和Cahors）来实现。夏季和冬季沉积物的确切性质将通过对两条渡槽沿线的一系列样本的综合分析来调查，通过监测这些渡槽的泉水，并通过监测仍在运行的水道中的碳酸盐生长。本研究涉及淡水碳酸盐岩沉积机制、古气候、碳酸盐岩微结构、淡水微生物学、水资源、历史工程、考古学等多学科交叉研究。

Terrestrial carbonate deposits such as speleothems, tufa and travertine are important archives for palaeoclimate and palaeohydrology. Recently, carbonate deposits formed in historical aqueducts have been recognised as a new high-resolution archive of this type, with the additional possibility to obtain archaeological information. Aqueduct channels are well-defined geometric structures, and carbonate deposition therein is easier to understand and model than in natural freshwater carbonate deposits. A better understanding of the layering in carbonate deposits from historical aqueducts is essential to explore their worldwide potential for high-resolution palaeo-environmental and archaeology studies. In a previous study on Roman aqueducts in Turkey our group has shown that stable isotopes can be used to identify annual layering in the deposits even when the typical petrographic alternation of dense, coarse-crystalline winter and fine-crystalline, porous summer calcite is not clearly visible or complex. We propose to expand this method and to make this new high-resolution archive more widely applicable to other climate zones and for all types of water sources. This will be achieved by investigating two Roman aqueducts in a new climatic area, in southern France (Fréjus and Cahors). The precise nature of summer and winter deposits and other layering will be investigated by a combined analysis of a series of carbonate samples along each of the two aqueducts, by monitoring of the springs feeding these aqueducts and by monitoring carbonate growth in a still functioning ancient channel. The study is multi- and transdisciplinary involving research on freshwater carbonate depositional mechanisms, palaeoclimate, rock microstructures, freshwater microbiology, water resources, historical engineering and archaeology. Natural freshwater terrestrial carbonates are also important reservoir rocks for oil and gas with increasing economic significance.Terrestrial carbonate deposits, such as speleothems, tufa and travertine, are important archives for palaeoclimate and palaeohydrology. In recent years, carbonate deposits formed in historical aqueducts have been recognised as a new high-resolution archive of this type, with the additional possibility to obtain archaeological information. Aqueduct channels are well-defined geometric structures, and carbonate deposition therein is easier to understand and model than in the majority of natural freshwater carbonate deposits. A better understanding of the layering in carbonate deposits from historical aqueducts is essential to explore their worldwide potential for high-resolution palaeoenvironmental and archaeological studies. In a previous study on Roman aqueducts in Turkey, our group has shown that stable oxygen and carbon isotopes can be used to identify annual layering even if the typical petrographic alternation of dense, coarse-crystalline winter and fine-crystalline, porous summer calcite is not clearly visible macro- and microscopically. We propose to expand this method in order to make this new high-resolution archive more widely applicable to other climate zones and for other types of water sources. This will be achieved by investigating three Roman aqueducts in another climate zone in southern France (Béziers, Fréjus, and Cahors). The precise nature of summer and winter deposits will be investigated by a combined analysis of a series of samples along each of the two aqueducts, by monitoring the springs feeding these aqueducts and by monitoring carbonate growth in a still functioning channel. The study is multi- and transdisciplinary involving research on freshwater carbonate depositional mechanisms, palaeoclimate, carbonate microstructures, freshwater microbiology, water resources, historical engineering and archaeology.