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標題: | 臺灣東北海岸南港層生痕化石Ophiomorpha isp.量化型態類型分析 Quantitative Morphological Analysis of the Trace Fossil Ophiomorpha isp. in Nangang Formation, Northeast Coast of Taiwan |
作者: | Chung-Ping Yeh 葉崇平 |
指導教授: | 施路易(Ludvig Lowemark) |
關鍵字: | 南港層,蝦類掘穴生痕化石,生痕化石型態,沉積相,中新世, Nangang Formation,Ophiomorpha,Morphology,Sedimentary facies,Miocene,Trace fossils, |
出版年 : | 2017 |
學位: | 碩士 |
摘要: | 蝦類掘穴生痕化石(Ophiomorpha)擁有良好的辨識性及分布性,在沉積學的領域上經常用以辨識環境,是使用十分頻繁的古環境指標。其中屬於Ophiomorpha的各項生痕化石種,還可以搭配各種生痕化石相指示出更為詳盡的沉積相。憑藉著獨特的泥球牆壁以及多樣化的洞穴結構,Ophiomorpha在生痕化石中有著十分顯著的辨識度。然而,這種生痕化石目前卻缺乏在形態上用以界定各式種類的量化標準。
為了得出此生痕化石分類的型態標準,本研究在臺灣東北角海岸的中新世南港層,測量岩層中數量豐富的Ophiomorpha樣本並加以記錄分析。在野外工作中,本研究測量了每個樣本的管直徑、分岔角度、管壁分岔點的大小、還有兩個分岔點之間的距離,且經過測量樣本資料近乎500份。初步測量的結果包含了管壁直徑的大小坐落在0.8至5公分間,分岔間的距離範圍橫跨1到20公分,且分岔點的大小一般都略大於管壁。 為了建立相對客觀的量化標準,並將此標準加以利用在現行的生痕化石種之內。本研究對上述的測量結果進行近一步的統計分析。發現依照野外測量的型態特徵,所有的樣本可以分成兩群,第一群的管壁直徑皆小於2公分,由分岔角度和分岔間距離的分析可知,此群的分岔模式為樹枝狀且有較低的分岔頻率。第二群的管壁直徑皆大於兩公分,分岔模式為二分岔枝狀,三個分岔角度都接近120度左右,且擁有較高的分岔頻率。 本研究試圖將量化的形態學方法應用在生痕化石的領域上,並期許這項方法可以在生痕化石中篩選出更多可以使用的型態特徵,以及替生痕分類學中的型態標準建立新的模式。 The trace fossil Ophiomorpha is commonly used as a paleoenvironment indicator in sandy environments by geologists. The ichnospecies of Ophiomorpha are also used for more detailed environment characterization in sedimentology and stratigraphy. The lined burrow system with knobby wall makes Ophiomorpha easily distinguishable from most other trace fossils. However, the morphological criteria used to distinguish between different morphologies or ichnospecies of the ichnogenus Ophiomorpha still remain poorly defined. In order to determine which properties of Ophiomorpha that can be used to separate the different morphotypes, and how to apply those properties in the classification of this ichnogenus, observations on a large number of specimens are needed. The Miocene Nangang Formation on the Northeast Coast of Taiwan provides well-exposed outcrops with abundant Ophiomorpha, allowing different morphotypes to be observed and measured. Through the field work in Nangang Formation, nearly 500 specimens of lined, tubular trace fossil have been analyzed and their architectural features, such as representative tube diameter, size of junctions, the distance between two adjacent junctions, and branching angles have been measured. The tube diameters typically are around 0.8-5.0 centimeters and the junction sizes are usually slightly larger than tube diameters. The distances between junctions vary greatly, usually ranging from 1.0 to 20.0 centimeters. This research attempts to build objective criteria to distinguish among the different characteristics of Ophiomorpha, and then clarify the connection between the observed morphologies and the established ichnospecies of Ophiomorpha. The statistical analysis of the morphological data reveals a high correlation between outer and inner tube wall diameters. Based on differences in parameters such as distance between junctions, tube diameters, and branching angles, the observed burrow systems can also be separated into two major groups. The first group have smaller tube diameter (<2 centimeters) and lower branching frequency, and their branching show a dendritic pattern. The second group has bigger tube diameters (>2 centimeters), higher branching frequency, and their branching pattern is of dichotomous type, with branching angles around 120 degrees. This research demonstrates that the quantitative morphological method can not only be applied in paleontology on body fossils, but the method can also be used to search for patterns and set morphological criteria for trace fossils. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/70155 |
DOI: | 10.6342/NTU201800205 |
全文授權: | 有償授權 |
顯示於系所單位: | 地質科學系 |
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