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Sand calcites as a key to Pleistocene periglacial landscapes
Quaternary Research ( IF 2.3 ) Pub Date : 2020-12-28 , DOI: 10.1017/qua.2020.98
Médard Thiry , Christophe Innocent , Jean-Pierre Girard , Anthony Richard Milnes , Christine Franke , Sophie Guillon

We tested the potential for sand calcites to serve as a novel paleoclimate archive by investigating their age and formation conditions. Fontainebleau sand calcites are Pleistocene in age (based on 14C and U-Th dating) and were primarily formed during glacial periods. δ13C values increase with the depth at which these sand calcites formed, consistent with open and closed CO2 systems. Interpretation of the δ18O-T relationship in sand calcites points primarily to their formation at a low temperature, around 2°C in shallow ground water and at about 9°C in deeper ground-water settings. Their occurrence, characteristics, and compositions suggest crystallization from paleo-ground waters in permafrost environments. Crystallization of sand calcites was triggered by degassing of cold carbonate-containing surface waters as they infiltrated warmer subsurface ground-water environments. We consider sand calcites to be important indicators of interactions between meteoric water and ground water in Pleistocene periglacial landscapes. Their disposition may point to specific features of periglacial landscapes, and their ages could permit an assessment of landscape incision rates. Large crystals and zoned spheroliths may, in fact, encapsulate continuous high-resolution records of continental glacial and periglacial paleoenvironments.

中文翻译:

砂方解石是更新世冰缘景观的关键

我们通过调查砂方解石的年龄和形成条件,测试了砂方解石作为新的古气候档案的潜力。枫丹白露砂方解石的年龄是更新世(基于14C 和 U-Th 测年),主要形成于冰期。δ13C 值随着这些砂方解石形成的深度而增加,与开放和封闭的 CO 一致2系统。δ的解释18砂方解石中的 OT 关系主要指向它们在低温下形成,在浅层地下水中约为 2°C,在较深的地下水环境中约为 9°C。它们的出现、特征和组成表明从多年冻土环境中的古地下水结晶。砂方解石的结晶是由冷的含碳酸盐地表水的脱气引发的,因为它们渗透到较温暖的地下地下水环境中。我们认为沙方解石是更新世冰缘景观中大气水和地下水相互作用的重要指标。他们的性格可能指向冰缘景观的特定特征,他们的年龄可以评估景观切割率。事实上,大晶体和带状球晶石可能
更新日期:2020-12-28
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