Lake Varves as Natural Calendars

湖相层作为自然日历

Varves are annual sediment layers formed in lakes in certain environments. According to Davidson and Wolgemuth "In northern latitudes where lakes freeze over, fine grained particles will settle out in winter, followed by coarser-grained material in spring as ice thaws and increased stream flow carries larger particles into the lake."

In other places, varves are produced by annual diatom blooms. "At all times of the year, fine particulate material settles out on the bottom, but during the spring, single-celled organisms with a solid shell rapidly reproduce near the surface of the lake. As they die, the shells rain out onto the lake floor and form a light-colored coating. Each winter-spring cycle produces a dark-light colored sediment couplet, or varve."

在其他地方，varves是由每年的硅藻 blooms产生的。‘全年都有细颗粒物质沉降到湖底，但在春季，具有坚硬外壳的单细胞生物在湖面附近迅速繁殖。当它们死亡时，外壳沉降到湖底，形成一层浅色的覆盖层。每个冬春周期都会产生一层深色-浅色的沉积层，即varve。

The photo at left shows two core sections of sediment varves. The photo is from Tufts University Glacial Varve Project.

左图显示了两个沉积层的核心部分。这张照片来自Tufts大学的冰期沉积层项目。

The graph below is a summary of comparison of carbon-14 activity with tree rings and with lake varves from Lake Steel in Minnesota and Lake Suigetsu in Japan. It was prepared by geologists Davidson and Wolgemuth. From Lake Suigetsu, a sediment core nearly 250 feet in length was collected in 1991. The core contained an uninterrupted sequence of varves with a total count in excess of 100,000!

下图是对碳-14活动与树轮以及明尼苏达州Steel湖和日本Suigetsu湖湖相沉积物的比较总结。该图由地质学家Davidson和Wolgemuth编制。1991年，从Suigetsu湖采集了一个近250英尺长的沉积物柱样。该柱样包含了一个连续的湖相沉积层序，总层数超过100,000层！

Varves 是在特定环境中湖泊中形成的年沉积层。根据 Davidson 和 Wolgemuth 的说法，在高纬度地区，当湖泊结冰时，细颗粒物会在冬季沉降，而春季冰层融化后，流速增加，较大颗粒物被带入湖泊，从而形成较粗颗粒的沉积层。

The varve data from Lake Suigetsu are from H. Kitagawa and J. van der Plicht, Atmospheric radiocarbon calibration beyond 11,900 CAL BP from Lake Suigetsu laminated sediments. Radiocarbon, 2000, 42:370-381. The Lake Steel varve data are from P.J. Reimer and 28 others, IntCal04 terrestrial radiocarbon age calibration, 0-26 cal kyr BP. Radiocarbon, 2004, 46:1029-1058.; J. Tian, T.A. Brown, and F.S. Hu, Comparison of varve and 14C chronologies from Steel Lake, Minnesota, USA. The Holocene, 2005, 15:510-517.

来自苏伊特湖（Lake Suigetsu）的varve数据来自H. Kitagawa和J. van der Plicht，见H. Kitagawa和J. van der Plicht，《从苏伊特湖叠层沉积物中获得的超过11,900年校正的大气碳-14年代数据》，《Radiocarbon》，2000，42:370-381。苏伊特湖的varve数据来自P.J. Reimer和28位其他作者，见P.J. Reimer和28位其他作者，《0-26 cal kyr BP的陆地碳-14年代校正》，《Radiocarbon》，2004，46:1029-1058；J. Tian, T.A. Brown和F.S. Hu，《美国明尼苏达州苏伊特湖varve与碳-14年代数据的比较》，《Holocene》，2005，15:510-517。