海洋粘土矿物的古环境含意辨析

粘土矿物组合反映了源区气候冷、暖周期性变化,记录了沉积区域古环境演化的重要信息,为古环境重塑提供了有力证据.但沉积岩中粘土矿物组合及含量变化用于古气候的解释目前尚存在一定的局限性和复杂性,例外情况时有发生.各种非气候因素,如源区、沉积环境、成岩作用、差异输送、自生作用,影响粘土矿物的分布和含量,使粘土矿物的古气候含意变得错综复杂.可能只有当沉积盆地很小或者是陆盆,沉积物中的粘土矿物对古气候才可能是有用的指示器.比较大的沉积盆地,尤其是海盆,是从遥远的源区接受岩屑载荷的,代表了一种多样化的环境条件.重组的距离越长,扩散过程越复杂,沉积的粘土矿物组合古气候信息越不清晰.粘土微粒要经过一个长距离才能从土壤到达海洋,因此沉积学家和古气候学家应该多注意土壤和沉积粘土矿物之间关系的复杂性.目前海洋粘土组合的古气候解释,可能代表一种相当宽泛的古气候信息或提供了所有气候影响的整合记录.

Differentiation and discrimination of marine clay minerals as indicators of paleoenvironment

Clay mineral assemblages reflect the periodic cold and warm climate changes of sources and records the important information of evolvement of sedimentary environment and thus affords vigorous evidence of reconstructing paleoenvironment.But currently climate interpretation of clay mineral assemblages and their content variation has somewhat limitation and complexity,with exceptions occur frequently.Various nonclimate factors such as source land,sedimentary environment,diagenesis processes,differential settings and authigenesis influence the distribution and the contents of clay minerals,thus make their paleoclimate significance complicated.Perhaps clay minerals of sediments can be useful indicators of paleoclimatic conditions when the sedimentary basins are small or are marked by continental episodes.Larger sedimentary basins,and particularly marine basins,on the other hand,receive their detrital load from vast source areas,where a wide variety of environmental conditions are represented.The longer the reworking distance,the more complicated are the dispersal processes and the less clear the paleoclimatic message of the deposited clay mineral assemblages.A clay particle has a long way to go from soil to marine sediment and sedimentologists and paleoclimatologists should pay more attention to the difficulties of retrospective analysis of the relation between soil and sedimentary clay minerals.At present,the paleoclimatic interpretations of marine clay assemblages yield,at best,nothing more than rather broad paleoclimatic information or may provide integrated records of overall climatic impacts.