浅议层序边界

About sequence boundary

基于现行层序地层学标准化建议方案出现的层序边界差异,分析层序边界设置的演变历史,存在将相对应的整合面cc分别放置在海平面、相对海平面或基准面垂向变化的1/8周期处、最低点、最高点3种方式。Sloss关于科迪勒拉冒地槽和阿巴拉契亚冒地槽之间的北美克拉通层序划分的年代地层关系图解,以及生物地层学均证实不整合面"楔入"层序为整体趋势,包围层序仅为局部的,这一观念的转变有利于层序地层学的进一步发展;岌岌湖现代水下加积扇实体模型经验地证实层序边界为残留最大水泛面及其相对应的不整合面,该定义也可为硅质碎屑岩背景提供借鉴。通过实例分析,比较了强迫海退底界、强迫海退顶界、残留最大水泛面+相对应的整合面3种层序边界划分,建议将不整合面"包围层序"的观念调整到"楔入且部分界定"这一理念上来。此外,对岸线迹线周期性约束层序边界、横向上不整合面上下地层成因关联性与其不整合面发育时间区间呈负相关问题进行了讨论。

Based on the boundary differences between sequence schools in the recommended scenarios of standardization of sequence stratigraphy,this paper analyses the designed history of sequence boundaries that are respectively placed on one-eighth periodicity of sea level,lowest of relative sea level and the highest of base level.The original conceptual model of sequences,recognized by Sloss in the North American Craton between Cordilleran Miogeosyncline and Appalachian Miogeosyncline,and biostratigraphy have proved that subaerial unconformities not only wedged into sequences entirely but also partly bounded them regionally;this transforming ideal is likely to be helpful to further development for sequence stratigraphy.Meanwhile,the empirically-based outcrop of Jijihu modern subaqueous aggradational fan（SAF）has proved that sequence boundaries are the pool-wards remnant maximum flooding surface（RMFS）and their landwards correlative subaerial unconformities（CSU）.This definition of sequence boundary may be considered to be used in siliciclastic settings.Comparing three sequence scenarios respectively bounded by base surface of forced regression（BSFR）,top of forced regressive deposits and RMFS＋CSU,this paper suggests that the ideal of subaerial unconformities enclosing sequences return to that of wedging and partly bounding sequences.Moreover,it has been discussed as follows：（1）the periodicity of shoreline trajectory should be used to restrict sequence boundary;（2）the strata relativity above and below subaerial unconformity are laterally negative to the development time intervals of subaerial unconformity.