沉積年代較古老的樣品因保存不易，樣品量稀少且資訊較不充分，但若能藉由高精密度的質譜技術，使用少量樣品獲取資訊，便能對古環境的研究有所助益。當樣品缺乏絕對定年的資料時，可以使用鍶同位素海水線輔助判斷樣品對應的地層年代，本研究共有三組樣品，其中兩組是還沒有定年資料的樣品，分別來自藍田鎮及黃羊山，樣品對應時代分別為新元古代及寒武紀，黃羊山的樣品有記錄到寒武紀末期的碳同位素正異常事件(SPICE)，另一組來自南橫公路，樣品對應年代為中新世至始新世，本研究嘗試將這三組樣品對應至鍶同位素海水線，來判斷樣品對應的地層年代。本研究使用ICP-OES及ICP-MS測量樣品主量及微量元素濃度，南橫樣品Sr濃度從1.1ppm – 206.4ppm,，黃羊山樣品Sr濃度從298 – 597ppm。為避免樣品雜質影響87Sr/86Sr同位素比值，本研究使用醋酸淋洗出樣品的碳酸鹽相，並針對不同濃度醋酸淋洗出的樣品性質差異做比較，發現最適合淋洗樣品的醋酸濃度約為1% (0.18N)。淋洗完的碳酸鹽相樣品經離子交換樹脂純化過後，使用多接收器感應耦合電漿質譜儀測量樣品87Sr/86Sr同位素比值，南橫樣品的87Sr/86Sr同位素比值分布從0.70828–0.71587，和同時代的鍶同位素海水線相比，比值過高，再從元素濃度去評估樣品是否有受後期成岩作用影響，樣品Mn/Sr及Mg/Ca皆顯示已受後期成岩作用影響，而將樣品的87Sr/86Sr同位素比值和全岩樣品測得的值對比，可再將其分成廬山層和畢祿山層做討論，畢祿山層樣品和全岩87Sr/86Sr同位素比值接近，指示全岩可能受白雲岩化作用，廬山層樣品和全岩87Sr/86Sr同位素比值相差較多，可能是受其他變質作用影響。黃羊山樣品的87Sr/86Sr同位素比值分布從0.70919–0.70957，雖其元素濃度檢驗結果顯示，樣品未受成岩作用影響，但仍有三個樣品值過高，且皆分布在Sr濃度較低的樣品，因此檢驗成岩作用時，可能需要額外考慮樣品Sr濃度，剩下的樣品對應至鍶同位素海水線，可以推測樣品年代大約在497-500 Ma之間。寒武紀末期時，海洋處於缺氧且上下層水不交換的狀態，造成生物滅絕事件，而鍶同位素海水線則指示當時有海進事件，因此，海進事件可能使得缺氧水範圍擴大，造成生物滅絕更嚴重。最後，本研究部分樣品測得之87Sr/86Sr同位素比值是偏高的，原因可能是沉積環境並非開放性大洋，而是淺海或邊緣海。

For the reconstruction of paleoenvironment, this study collected samples from Lantian, Southern Cross-Island Provincial Highway (SC), and Huangyangshan (HYS) , try to estimate age from carbonate phase in samples. By measuring 87Sr/86Sr ratios from original carbonate phase from samples, and correspond 87Sr/86Sr values to strontium isotope seawater curve, we can estimate the age of samples. First, we used acetic acid to leach carbonate phase from samples, then measure concentration of elements of samples by ICP-OES and ICP-MS, and we could determine which samples preserve their original information from their element ratios.Then we measured 87Sr/86Sr ratios of samples by MC-ICP-MS, corrected data using SSB method. 87Sr/86Sr ratios of SC samples are higher then expected. Due to element ratios measured before, we surmise it may caused by diagenesis. 87Sr/86Sr ratios of HYS samples can correspond to strontium isotope seawater curve, and indicate age about 497 – 500 Ma. But there are still some samples have higher 87Sr/86Sr ratios. We have determined HYS samples preserved their original isotope signatures, so the higher value of 87Sr/86Sr ratios may indicate HYS samples were deposited in shallow sea or marginal sea . This study conclude that SC samples have affected by diagenetic effect ,and HYS samples may deposited in shallow sea or marginal sea.
Key words : Sr isotope , seawater strontium isotope curve, SPICE

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