NUMERICAL ANALYSIS OF FORAMINIFERAL ASSEMBLAGES: A TOOL FOR RECOGNIZING DEPOSITIONAL FACIES IN LOWER MIOCENE REEF COMPLEXES
NUMERICAL ANALYSIS OF FORAMINIFERAL ASSEMBLAGES: A TOOL FOR RECOGNIZING DEPOSITIONAL FACIES IN LOWER MIOCENE REEF COMPLEXES
复制标题
有孔虫组合的数值分析：识别下中新统礁石沉积相的工具
DOI：
--
复制
发表时间：
1985
期刊：
影响因子：
--
通讯作者：
E. C. Glenn
中科院分区：
文献类型：
--
作者：
P. Hallock;E. C. Glenn
对菲律宾巴拉望西北海岸Matinloc 2井和Libro 1井下中新世岩心薄片中钙质有孔虫组合的研究发现，这两口井的生物相相似。对原始资料进行多变量和形态计量学分析，划分出三个组合。这三个组合有助于确定两口井中发现的四个不同的相：1)以小有孔虫和千年虫为特征的小有孔虫砾石包岩，2)珊瑚边界岩与有孔虫-藻包岩，其中小的有孔虫-水母组合与一些较大的有孔虫组合一起表示，3)藻类较大的有孔虫包裹岩，其特征是Amphistegina和miogyp-sinids，以及4)较大的有孔虫包岩，其中大的、扁平的、定向的鳞藻和环藻在含有浮游叉虫的泥晶基质中占主导地位。这四个相分别代表：1)泻湖沉积，2)珊瑚碎屑礁坪或礁缘，3)藻类稳定的礁坪，4)淹没的礁或斜坡沉积。对104m马丁洛克2岩心的沉积史解释为：岩心下部44m处为泻湖充填，顶部为浅海藻类稳定的礁滩。珊瑚礁平面上的能量略有增加，使得珊瑚可以在被植被覆盖的珊瑚礁平面取代之前暂时定居。最后，在岩心上部41m处，明显存在一个从平坦的礁体到淹没的礁体的主要海侵序列。淹没的珊瑚礁石灰岩被页岩覆盖。天秤一号岩芯虽然不完整，但在下部显示出类似的浅泻湖和礁坪，而在上部显示出逐渐淹没的礁石。
Study of the calcareous foraminiferal assemblages in thin sections of lower Miocene cores from the Matinloc 2 and Libro 1 wells off the northwest coast of Palawan, Philippines, revealed similar biofacies in the two wells. Multivariate and morphometric analysis of the fora- miniferal data distinguished three assemblages. These three assemblages helped to define four distinct facies that are found in both wells: 1) small foraminiferal grainstone-packstones charac- terized by small rotaliines and miliolines, 2) coral boundstones with foraminiferal-algal packstones in which a small rotaliine-milioline assemblage is represented along with some larger rotaliine foraminifera, 3) algal-larger foraminiferal packstones characterized by Amphistegina and miogyp- sinids, and 4) larger foraminiferal wackestones in which large, flat, oriented lepidocyclinids and Cycloclypeus dominate in a micrite matrix that bears planktonic foraminifera. These four facies were interpreted to represent, respectively: 1) lagoonal sediments, 2) coral-rubble reef flat or reef margin, 3) algal-stabilized reef flat, and 4) drowned reef or slope sediments. The depositional history of the 104 m of Matinloc 2 core is interpreted as follows: lagoonal infill topped by shallow algal-stabilized reef flat is indicated in the lower 44 m of core. A slight increase in energy on the reef flat allowed for temporary colonization by coral before replacement by vegetated reef flat. Finally, a major transgressional sequence of reef flat to reef to drowned reef is evident in the upper 41 m of the core. The drowned-reef limestones are overlain by shales. The Libro 1 core, though incomplete, shows similar conditions of shallow lagoon and reef flat in the lower portion and progressive drowning of the reef in the upper portion.