論湖南省泥盆紀地層與沈積環境

作者:胡忠恆(國立臺灣師範大學理學院物理系)

摘要：

根據目前可能得到的地質資料顯示，湖南省泥盆系地層的形成與沉積的環境，是屬於循環式（Rhythmic sedimentary cycle）與大海灣型（Embayment）。整個泥盆紀有二次沉積循環發生；第一次沉積循環為跳馬澗海侵與棋子橋海退，發生於早期至晚期中部泥盆紀，完成了上、下跳馬澗統與棋子橋統的沉積物；第二次沉積循環為余田橋海侵與錫礦山海退，發生於早期上部泥盆紀至晚期上部泥盆紀，完成了余田橋統，錫礦山統與岳麓砂岩（？）的沉積物。泥盆紀的湖南大海為一葫蘆形的海灣，湖中以北為內灣，而湖南以南至兩廣地帶為外海。其沉積物由南向北，由湖中向西，向北，向東發生變化。非碎層岩類或細粒碎層岩類主要分佈於湖中的南北方向，而粗粒的碎屑岩類則陳列大海灣的週邊地區，即湘西、湘北極湘東之半圓形地帶。又根據岩相分析的結果顯示，湖中偏湘西區為較深海，而湘北之湘東區則為淺海乃至近海，湘西有高山或古陸，而湘東及北方則為低地或丘陵地帶。海底由東向西漸趨加深，呈不對稱形式，而北方為淺海，南方則為開?的遠海或深海區。

《詳全文》

An Essay on Devonian Stratigraphy and Sedimentary Environment of Hunan Province , Southern China

Author: Chung-Hung Hu

Abstract：

Devonian deposits of the Hunan province furnish record of remarkably rhythmic transgression and regression of shallow sea. Two rhythmic sedimentary cycles are recognizable during the early Middle Devonian to the late Upper Devonian period. The first sedimentary cycle is named Tiaomachien cycle, which contains Tiamachien transgression and Chetzechiao regression, and the second is Shetienchiao cycle contains Shetienchiao transgression and Hsikuangshan regression. During the advance of the sea pread over of the entire area, it leaves record of its existance in deposits of conglomerate, sandstone, purplish shale, yellowish sandy shale, argillaceous lime stone, lump limestone sequence or sandstone, shales, shaly limestone, banded limestone, and lump limestone sequence. During the retreat of the sea, it remains record of ero-sional surface to form an unconformity or disconformity between the next sedimentary cycle.
Study of the whole body of deposits, taking account of characters observed both horizontally and vertically, lead inescapably to the conclusion that during the Devonian period the trangression of the seas inward from northern Kwangton and Kwangsi provinces to northern Hunan and the regression seas outward from northern Hunan to northern Kwangton and Kwangsi. The depositional area is a shallow sea showing an embayment structure. The embayment lies mainly from south-central to north central areas of Hunan. According to the result of lithologic analysis of the deposits, it suggests that on the west side of the embayment occupies possibly an high land or mountains, and the north and east sides are low land, might stand just above the sea level.