苗栗白沙屯地區頭嵙山層之年代地層與沉積環境

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Title:	苗栗白沙屯地區頭嵙山層之年代地層與沉積環境
Authors:	李慶蘭;Chin-Lan Lee
Contributors:	地球物理研究所
Keywords:	底棲性有孔蟲化石;浮游性有孔蟲化石;鈣質超微化石;年代地層;沉積環境;白沙屯;頭嵙山層;過港貝化石層;benthonic foraminifera;planktonic foraminifera;calcareous nannofossil;ronostratigraphy;sedimentary environment;Paishatung;Toukoshan formation;Koukang Shell Bed
Date:	2000-07-20
Issue Date:	2009-09-22 09:52:53 (UTC+8)
Publisher:	國立中央大學圖書館
Abstract:	本研究針對位於苗栗縣白沙屯地區之頭嵙山層，選擇七個剖面，利用鈣質超微化石及有孔蟲化石對本區域之地層做地質年代及沉積環境上的解析與比較。依據鈣質超微化石之分析結果，白沙屯地區各剖面地質時代均屬於更新世早期，即Pseudoemiliania lacunosa帶中上部，絕對年代約為1.24~0.46Ma。各剖面中最老的磚場剖面（ZC）屬於small Gephyrocapsa亞帶，絕對年代為1.24~1.03Ma，最年輕的清海宮剖面（CHK）屬於Pseudoemiliania lacunosa亞帶末期，其他剖面屬於Pseudoemiliania lacunosa亞帶，絕對年代為1.03~0.46Ma。由鈣質超微化石環境分析其沉積環境，各剖面因含有Helicosphaera, Coccolithus及Discolithina等種屬，指示地層之古沉積環境為開闊、近岸之淺海環境，本區域之浮游性有孔蟲化石群集亦以暖水域的種屬為主。根據底棲性有孔蟲化石的環境分析結果，各剖面的層位稍有不同，除了磚場剖面（ZC）的底棲性有孔蟲化石之優勢種為Bolivina、Melonis、Textularia及Discorbis（B-M-T-D）群集，顯示的古沉積環境為正常鹽度、較深的中~外大陸棚環境外，其餘剖面之底棲性有孔蟲化石優勢種為Textularia、Cibicides、Quinqueloculina及Discorbis（T-C-Q-D）群集，顯示其古沉積環境為正常鹽度、較淺的內大陸棚環境。依據過港貝化石層之浮游性有孔蟲化石碳氧同位素分析結果，顯示該沉積物沉積當時為更新世暖期，與底棲性有孔蟲化石、鈣質超微化石及浮游性有孔蟲化石分析之結果相符。 Seven sections were selected from the Toukoshan Formation of the Paishatung area in Miaoli for this study, which is focused on the analyses of biostratigraphy, geological age and paleoenvironments by calcareous nannofossils and foraminiferal fossils. Based on the calcareous nannofossil study, the geological age of the sections of Paishatung area is determined as early Pleistocene in age. They can be assigned to the middle~upper parts of the Pseudoemiliania lacunosa Zone which corresponds to the age interval of 1.24~0.46Ma. The eldest one is correlated to the small Gephyrocapsa subzone which corresponds to the age interval of 1.24~1.03Ma. The youngest one is determined to the upper Pseudoemiliania lacunosa subzone. Others are assigned to the Pseudoemiliania lacunosa subzone which corresponds to the age interval of 1.24~1.03Ma. According to the analyses of the paleoenvironments by calcareous nannofossils, because of the existing of the genus, Helicosphaera, Coccolithus and Discolithina, the paleosedimentary environment of the sections is open neritic-shallow marine. The dominated species of the planktonic foraminiferal fossils belongs to warm fauna. From the results of paleoenvironments analyses by the benthonic foraminiferal fossils, only one section belongs to the B-M-T-D assemblage composed mainly by Bolivina, Melonis, Textularia and Discorbis. The assemblage indicates the environment of middle~outer shelf with deeper and normal salinity water mass. Others belongs to the T-C-Q-D assemblage composed by Textularia, Cibicides, Quinqueloculina and Discorbis. The assemblage indicate the environment of inner shelf with shallower and normal salinity water mass. The results of carbon-oxygen isotopic composition from Koukang Shell Bed was suggested that they were deposited in a warm period of the Pleistocene. This conclusion agreed with the results of the analysis by planktonic and benthonic foraminiferal fossil and calcareous nannofossils.
Appears in Collections:	[Graduate Institute of Geophysics] Electronic Thesis & Dissertation

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