事件层的保存潜力探讨  

Discusses on Preservational Potential of Event Bed

作　　者：S.G.Pemberton 周志澄[2] J.MacEachern 

机构地区：[1]加拿大艾伯塔大学地球和大气科学系 [2]中国科学院南京地质古生物研究所,南京210008 [3]加拿大西蒙弗雷泽大学地球科学系

出　　处：《沉积学报》2001年第1期7-12,共6页Acta Sedimentologica Sinica

基　　金：国家自然科学基金! (批准号 :49872 0 46 );古生物所创新基金成果

摘　　要：影响事件层保存潜力的主要因素有 :纯粹的沉积速率、生物成因的混合速率以及机械改造的规模 ,可以从时间规模 (过渡时间和消除时间 )的角度来考虑事件层保存潜力。基底的机械改造同样对于事件层和正常天气下的沉积物的保存具有重要影响。综合分析影响事件层保存潜力的各种因素表明 ,在近基的临滨带中、上部及滨外带下部 ,事件层具有较高的保存潜力 ,而在近基及远基两端之间的临滨带下部及滨外带上部 。The increasing awareness of tempestites in the ancient record has correspondingly led to much consideration of their preservability. The main factors influencing the preservability are the net sedimentation rate, the biogenic mixing rate, and the magnitude of physical reworking. Wheatcroft has put forward the concept of time scales to attempt to solve this problem. The terms of transit time and dissipation time are introduced. Transit time is related to the thickness of the biogenic reworking zone , the thickness of event beds and sedimentation rate. The biogenic reworking zone is also controlled by the animal size and the behavior engaged in during its generation. The determination of transit time is difficult because of the unsteady and unpredictable sedimentation rate. The determination of dissipation time is even more complicated than that of transit time. The dissipation time is controlled by many factors such as the size of infauna, the behavior engaged in by the organisms, the dynamic interplay between the benthic community and the depositional event itself, the desirability of the event bed as a site for colonization and as a repository of food resources and the absolute time available for burrowing etc. Unfortunately, the preceding factors appear to resist quantification and therefore severely limit the effectiveness of existing mathematical models to explain tempestites preservation in the rock record. Physical reworking of the substrate has a profound effect on the preservation of both the event bed and the fair-weather deposits. On the basis of comprehensive analyses of all factors influencing preservational potential of event beds and empirical observations, both proximal upper-shoreface and middle-shoreface and distal shelf and lower offshore favor preservation of tempestites but for markedly different reasons. The lowest preservational potential for tempestites appears to occur somewhere between the proximal and distal extremes. Such zones appear to correspond to proximal Cruziana ichnofac

关 键 词：事件层 保存潜力 过渡时间 消除时间 机械改造 沉积速率 生物成因 事件地层学 

分 类 号：P539.6[天文地球—古生物学与地层学] P512.2[天文地球—地质学]