Mechanism of Varve Formation and Paleoenvironmental Research at Lake Bolterskardet, Svalbard, the Arctic  

作　　者：CHU Guoqiang LIU Jiaqi GAO Denyi SUN Qing 

机构地区：[1]Institute of Geology and Geophysics, Chinese Academy of Science, Beijing 100029 [2]Institute of Atmospheric Physics, Chinese Academy of Science, Beijing 100029 [3]The Geological Analysis Center, Beijing 100037

出　　处：《Acta Geologica Sinica(English Edition)》2006年第4期557-563,共7页地质学报（英文版）

基　　金：supported by the National Natural Science Foundation of China(Grant Nos.40472092,40352001);the Scientific Expedition Association;and the Yilite-Mulin Group,China.

摘　　要：On the basis of observation of thin sections and ^137Cs data, laminations in sediment are interpreted to be varves in Bolterskardet Lake （78°06′ N, 16°01′ E）, Svalbard, the Arctic. Varves appear under a petrologic microscope as couplets of dark-silt and light-clay layers. The mechanism of varve formation is surmized as follows： each silt layer is the production of sediment inflow interpreted as mainly derived from snowmelt during summer; each clay layer was deposited in a stillwater environment during an ice-cover period. A light -clay layer provides an important index bed to identify the annual interface. The high accumulation rates, long period of ice cover, and topographically closed basin are probably all critical factors in forming and preserving varves. Varve thickness is known to be controlled mainly by summer temperature. The variation of varve thickness in Lake Bolterskardet can then be used to reconstruct summer temperature. The varve series show that there has been distinct decade-scale variability of summer temperature over the past 150 years. Warm periods occurred in the 1860s, around 1900, the 1930s, 1950s, and 1970s, and in the last 20 years. The varved sediments of Lake Bolterskarde preserve an ideal record for high-resolution paleoclimatic and paleoenvironmental research in this data-sparse area.On the basis of observation of thin sections and ^137Cs data, laminations in sediment are interpreted to be varves in Bolterskardet Lake （78°06′ N, 16°01′ E）, Svalbard, the Arctic. Varves appear under a petrologic microscope as couplets of dark-silt and light-clay layers. The mechanism of varve formation is surmized as follows： each silt layer is the production of sediment inflow interpreted as mainly derived from snowmelt during summer; each clay layer was deposited in a stillwater environment during an ice-cover period. A light -clay layer provides an important index bed to identify the annual interface. The high accumulation rates, long period of ice cover, and topographically closed basin are probably all critical factors in forming and preserving varves. Varve thickness is known to be controlled mainly by summer temperature. The variation of varve thickness in Lake Bolterskardet can then be used to reconstruct summer temperature. The varve series show that there has been distinct decade-scale variability of summer temperature over the past 150 years. Warm periods occurred in the 1860s, around 1900, the 1930s, 1950s, and 1970s, and in the last 20 years. The varved sediments of Lake Bolterskarde preserve an ideal record for high-resolution paleoclimatic and paleoenvironmental research in this data-sparse area.

关 键 词：Arctic sediments VARVES PALEOCLIMATE summer temperature 

分 类 号：P532[天文地球—古生物学与地层学]