Diagenetic alteration and burial environment of fossil hard tissues

化石硬组织的成岩蚀变与埋藏环境

基本信息

批准号：
07454122
负责人：
SUZUKI Seiichi
金额：
$ 3.84万
依托单位：
FUKUOKA UNIVERSITY OF EDUCATION
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1995
资助国家：
日本
起止时间：
1995 至 1996
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-07454122/
关键词：
fossilization diagenesis carbonate cement mollusca pore water silicification calcite aragonite

项目摘要

Carbonate fossil hard tissues were collected from Lower Cretaceous to Quaternary systems in Japan, which are composed of non-carbonate clastic rocks, for the investigation of their diagenetic alteration. In clastic rocks cemented with carbonates (mainly calcite), three types of carbonate tissues (aragonite, low magnesium calcite=calcite and high magnesuim calcite) have the manner different from each other during burial stages, although all of the tissues within the host rocks with non-calcareous cement have usually been dissolved. Calcitic tissues are very stable so that the alteration did not occur in the calcitic specimens from the Upper Cretaceous and more younger strata. High-Mg-calcitic ones are comparatively well remaining in many cases, but they have been converted to low Mg calcite. Aragonitic ones show various patterns of the fossilization, such as preservation without any mineralogical alteration, calcitization (conversion to calcite through a thin solution film), dissolution and replacement with non-carbonate minerals. Original aragonite sometimes remains in the Upper Cretaceous rocks, though the calcitization commonly occurred in the Miocene and more older strata (sometimes in the Piocene and Pleistocene). Silicification of aragonitic tissues was observed in many strata of various ages, and chloritization, glouconitization and pyritization were also recognized in some strata. These are characterized by the preservation of microstructures. The alteration of araginitic tissues seems to have occurred in the mixing zone between marine and meteoric waters located near coastal regions.

在日本下白垩世至第四纪系统中采集了由非碳酸盐碎屑岩组成的碳酸盐化石硬组织，用于研究其成岩蚀变。在以碳酸盐（主要是方解石）胶结的碎屑岩中，三种类型的碳酸盐组织（文石、低镁方解石=方解石和高镁方解石）在埋藏阶段的表现方式各不相同，尽管围岩内的组织均具有不同的特征。非钙质水泥通常已溶解。方解石组织非常稳定，因此来自上白垩统和更年轻地层的方解石样本中没有发生改变。高镁方解石在许多情况下保存得相对较好，但它们已转化为低镁方解石。文石显示出各种化石化模式，例如没有任何矿物学改变的保存、方解石化（通过薄溶液膜转化为方解石）、溶解和被非碳酸盐矿物替代。原始文石有时残留在上白垩统岩石中，尽管方解石化通常发生在中新世和更古老的地层中（有时在新世和更新世）。在不同时代的许多地层中均观察到文石化组织的硅化，部分地层还发现绿泥石化、绿泥石化和黄铁矿化。这些的特点是保留微观结构。藻质组织的改变似乎发生在沿海地区附近的海洋和大气水域之间的混合区。