The McMurdo Dry Valleys presently contain more than 20 permanent lakes and ponds, which vary markedly in character. All, with the exception of a hypersaline pond, have a perennial ice-cover. The dry valley lakes, and lakes in other ice-free regions of continental Antarctica, are unique on this planet in that they consistently maintain a thick year-round ice cover (2.8–6.0 m) over liquid water. The persistent ice covers minimize wind-generated currents and reduce light penetration, as well as restricting sediment deposition into a lake and the exchange of atmospheric gases between the water column and the atmosphere. From a paleolimnological perspective, the dry valley lakes offer an important record of catchment and environmental changes. These lakes are also modern-day equivalents of periglacial lakes that were common during glacial periods at temperature latitudes. The present lakes are mostly remnants of larger glacial lakes that occupied the valleys in the past, perhaps up to 4.6 Ma ago. Two of the valleys contain evidence of being filled with large glacial lakes within the last 10000 years. Repeated drying and filling events since then have left a characteristic impression on the salt profiles of some lakes creating a unique paleo-indicator within the water column. These events are also marked in the sediments by the concentration and dilution of certain chemical constituents, particularly salts, and are also corroborated by carbonate speciation and oxygen isotope analysis. Stratigraphic analysis of dry valley lake sediments is made difficult by the occurrence of an ‘old carbon’ reservoir creating spurious radiocarbon dates, and by the high degree of spatial variability in lake sedimentation. From a biological perspective, the lakes are relatively simple, containing various taxa of planktonic and benthic microorganisms, but no higher forms of life, which is an advantage to paleolimnologists because there is no bioturbation in the sediments. Useful biological paleo-indicators found in the sediments include cyanobacterial filament sheaths, diatom frustules and other eukaryotic algal cells, protozoan cysts, photosynthetic pigments, and minerals (e.g. carbonates) associated with microbial activity. Future work will benefit from fully characterizing the connection between the ice covers, environmental conditions, and paleo-indicators, thereby allowing refinement of inferences made concerning the paleoenvironment. New dating techniques need to be tested in this environment to overcome the problems associated with radiocarbon dating. The establishment of a detailed and focused paleolimnological campaign is proposed.

中文翻译：

---

南极洲麦克默多干谷的古湖泊学

麦克默多干谷目前包含 20 多个永久性湖泊和池塘，它们的特征明显不同。除了高盐度池塘外，所有的池塘都有常年冰盖。干谷湖泊和南极洲大陆其他无冰地区的湖泊在这个星球上是独一无二的，因为它们在液态水上始终保持着厚厚的全年冰盖 (2.8-6.0 m)。持久的冰盖最大限度地减少了风力产生的洋流，减少了光线的穿透，并限制了沉积物沉积到湖泊中以及水柱与大气之间的大气气体交换。从古湖泊学的角度来看，干涸的山谷湖泊提供了流域和环境变化的重要记录。这些湖泊也是现代冰缘湖泊的等效物，这些湖泊在温度纬度的冰川时期很常见。现在的湖泊大多是过去占据山谷的较大冰川湖的残余物，可能长达 4.6 Ma。其中两个山谷包含在过去 10000 年内充满大型冰川湖的证据。此后反复的干燥和填充事件在一些湖泊的盐分剖面上留下了特征性的印象，在水柱内创造了一个独特的古指标。这些事件也在沉积物中通过某些化学成分（尤其是盐类）的浓缩和稀释来标记，并且也通过碳酸盐形态和氧同位素分析得到证实。干谷湖沉积物的地层分析变得困难，因为“旧碳”储层的出现产生了虚假的放射性碳日期，以及湖泊沉积的高度空间变异性。从生物学的角度来看，湖泊相对简单，含有浮游和底栖微生物的各种分类群，但没有更高的生命形式，这对古湖泊学家来说是一个优势，因为沉积物中没有生物扰动。在沉积物中发现的有用的生物古指标包括蓝藻丝鞘、硅藻壳和其他真核藻细胞、原生动物包囊、光合色素和与微生物活动相关的矿物质（例如碳酸盐）。未来的工作将受益于对冰盖、环境条件、和古指标，从而可以改进关于古环境的推论。需要在这种环境中测试新的测年技术，以克服与放射性碳测年相关的问题。建议建立详细和重点突出的古湖沼学运动。