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標題: | 三峽地區上新世早期二鬮層底部之孢粉分析 Pollen Analysis of the Lower Erhchiu Formation, The Early Pliocene, San-hsia, Northern Taiwan |
作者: | Li-Chiou Li 李麗秋 |
出版年 : | 1989 |
學位: | 碩士 |
摘要: | 本文著重於分析古植物社會之組成,輔以沈積璟境之之研究,來探討上新世早期三峽地區二鬮層底部之古生態環境。 分析本區之孢粉化石植物群,發現此孢粉化石組合中,被子植物化石花粉佔65.7%,裸子植物化石花粉佔17.2%,蕨類植物化石孢子佔17.1%。被子植物化石花粉中,與現生殼鬥科有親緣關係之三溝孔粉佔?大優勢,約佔總孢粉量之35%,佔被子植物化石花粉之53%左右。裸子植物化石花粉中,以松粉屬居第一位,約佔總孢粉量之9.5%,佔裸子植物化石花粉之55%左右。由此孢粉分析所反映之古植被為由常綠闊葉樹林為主所組合而成之植物社會。古氣候為熱帶、亞熱帶至暖溫帶。本孢粉分析之組成分子,幾乎大部分皆與現今臺灣森林之組成分子相同。 以地層剖面之建立,沈積岩相之組合,來探討此地區之沈積環境,推測其為受潮汐作用為主之海灣、河口之沈積環境。以古水流方向之研究,配合砂岩岩象學之分析,求出古水流為東南向西北流,而沈積物之中已含有中央山脈之板岩及變質石英岩之岩石碎屑物。推測沈積物之來源主要來自於古臺灣島。 由古孢粉學與沉積學上之研究,推測於沉積作用發生時,古臺灣島上已有和現今臺灣植被一樣垂直分佈之植物帶。 於此孢粉組合中,發現了四個新屬,八個新種及五個新記錄種。新發現的八個新種之中,除了臺灣網面三溝粉及大型錦葵粉不能確定其性狀外,其餘六種是具草本性狀植物科群之花粉化石。這些花粉化石可以說是新生代晚期之指標。 本孢粉分析中,草本性狀植物之化石花粉以蓼粉屬最多,佔孢粉總數之7%左右,其餘如藜科、菊科、禾本科之百分組成均少於1%,而水蕨孢於此分析中佔孢粉總數之1.7%;其與大陸上新世之孢粉分析特徵不甚符合,推論大陸孢粉分析之資料無法適用於臺灣地區,或者可能本區二鬮層底部之年代應較上新世為早。 In order to elucidate the palaeoecology of the lower Erhchiu Formation, the Early Pliocene, Sanhsia, northern Taiwan, an effort has been made to analyse the fossil pollen assemblage and reconstruct the depositional environment of that area. In this pollen analysis, 65.7 per cent angiosperms pollen , 17.2 per cent gymnosperms pollen, 17.1 per cent pteridophytic spores were obtained. The Tricolporopollenites pollen, having affinity with living Fagaceae, are dominated in angiosperms pollen, occupying about 35 per cent of the total palynomorphs and 53 per cent of the angiosperms pollen. The Pityosporites pollen, having affinity with the living Pinus species, are dominated in gymnosperms pollen, occupying about 9.5 per cent of the total palynomorphs and 55 per cent of the gymnosperms pollen. Evergreen broad-leaved forest is the main type of the vegetation reflected by the pollen analysis. The paleoclimate is possibly tropical, subtropical to warm temperate. The main components of the pollen analysis are almost the same as those of the extant Taiwan forests. Studying the depositional structures, paleocurrent direction and sandstone petrography, the writer has reached the following conclusions as to the depositional environment of the said formation: (1) the depositional site of the lower Erhchiu Formation must be in the estuary environment dominated with tidal current; and (2) the paleocurrent direction was approximately northwestward; and (3) the slate and metaquartzite rock fragements can be found in the sediments; and (4) the sediments making up the said formation were probably derived from the pro-Taiwan island. The results from investigations of palaeopalynology and sedimentology indicate the presence of vertical zonation in pro-Taiwan vegetation of the said formation. In this pollen assemblage, four new genera, eight new species and five new records have been found. In the eight new species, except the Retitricolpites taiwanensis and Malvacearumpollis majus which can't be confirmed, the six new species are herbaceous angiosperm pollen. These herbaceous angiosperm pollen can be useful as indicators of the Late Cenozoic age. In this pollen analysis, the herbaceous angiosperm pollen, with polygonacidites as its main component, only reach 7 per cent of the total palynomorphs. The others, including Artemisia-pollenites, Chenopodiopollis and Graminidites which percentage are under 1 per cent of the total palynomorphs. But the Magnastriatites spore reaches 1.7 per cent of the total palynomorphs. The Result dose not agree with the palynological data obtained from the Pliocene of the Mainland China, otherwise the age of the said formation should be earlier than the Pliocene. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/75702 |
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顯示於系所單位: | 植物科學研究所 |
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