黄土高原区环纹藻化石的发现及其意义

DISCOVERY AND SIGNIFICANCE OFTHE CONCENTRICYSTES FOSSILS ON LOESS PLATEAU

环纹藻化石不仅广泛分布于我国东南部新生界地层，而且笔者近年在黄土高原区晚更新世以来的孢粉中亦有较多发现。在８个化石点共找到环纹藻化石２３７８粒．研究表明，它具有横向和纵向分布规律性。含环纹藻的孢粉组合不仅有喜暧湿的阔叶树种花粉，而且也有喜冷湿的暗针叶树种花粉，反映了环纹藻对气候有很强的适应性．我国西部环纹藻化石种类较东南部单调，其数量从东向西趋于减少。其时代分布，从晚更新世早期到晚全新世，以中全新世最为繁盛。人们可依据它及其共生藻类，追溯到地史时期淡水湖沼的消长。

The concentricystes fossils are distributed not only over the Cenozoic strata in the south-east of China,but also over the loess plateau of China. They are more discovered by the author in the sPOre-pollen formedsince the later pleistocene ePOCh. There are 2378 concentricyStes particles found at & fossil-sites. It is revealed by studing that their distribution has the vertical and horizontal regularity. The sPOre-pollen of concentricystes is comPOsed of not only the pollen of the broadleaf trees which are fond of marm and moistweather but also the POllen of the dark coniferous trees which are keen on cold and moist weather. Thisshows that the concentricystes are of a high adaptability to weather changes. There are less kinds of concentricyStes fossils in the weats of China than that in the south--east of Chia. Its quantity gets less and less fromthe east to the west. Its age ranges from the early period of the late Pleistocene to the late Holocene, and themost prosperous time was in the middle Holocene. The nuctuation of the fresh water lakes over the geological epoch can be dated back to according to it and its mutualism algae.