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AN UPPER TRIASSIC (RHAETIAN) RADIOLARIAN ASSEMBLAGE FROM BUSUANGA ISLAND, PHILIPPINES

菲律賓晚三疊世瑞替時代放射蟲族群之比較研究

摘要


This report deals with biostratigraphic correlation and systematic paleontology for a Rhaetian (Upper Triassic) radiolarian assemblage from Busuanga Island, Phililppines. The studied material was collected from a thinly-bedded red chert exposed at the eastern part of Busuanga Island, the Philippines. This sample yielded an abundant and fairly well preserved radiolarian fauna which has not been described in previous work. In this report the studied fauna is named the Parabipedis pessagnoi Assemblage. It contains more than forty taxa including several distinctive forms such as Deflandrecyrtium carterae, n. sp., Eptingium (?) amoenum Carter, Ferresium philippinense, n. sp., Haeckelicyrtium karcharos Carter, Livarella densiporata Kozur and Mostler, Livarella gifuensis Yoshida Parabipedis pessagnoi, n. sp., Pseudoheliodiscus huxleyen-sis (Carter), and Risella tledoensis Carter. Although an identical assembllage has not been described in previous studies, some species of the studied fauna have been previously reported from Central Japan and Queen Charlotte Islands, British Columbia, Canada. The results of faunal comparisons indicate that the studied fauna is probably late early Rhaetian in age, and it closely resembles a Rhaetian radiolarian fauna from Central Japan.

關鍵字

Radiolaria Triassic Rhaetian Philippines

並列摘要


本文旨在報導作者針對有史以來首次發現於菲律賓北巴拉灣地塊的一個瑞替(Rhaetian)時代放射蟲族群進行比較研究的結果。本研究標本採自布西安哥島(Busuanga Island)東部巴地克山脈(Patic Range)東緣的一個紅色(石圭)質岩剖面。在同一剖面採集的十一個標本(CR90-164至CR90-174)中,只有一個(CR90- 165)含有瑞替時代的放射蟲族群。其餘標本中之放射蟲保存不良,可辨識者之年代分別為晚三疊世(Norian) (CR90- 164)、早侏羅世(CR90-166)、晚二疊世(CR90-167)以及中三疊世(CR90-169) 。本研究之放射蟲定年顯示該(石圭)質岩層剖面層位錯亂,並非正常的沈積岩系,而是由板塊作用推擠而成的構造岩塊。由於本研究族群含有相當數量的Parabipedis pessagnoi, n. sp.,且其特徵極為明顯,因此作者將此放射蟲族群命名為Parabipedis pessagnoi族群。因標本保存不佳,許多個體難以辨識。經多次處理篩洗的結果,己知此一族群至少含有40種以上的放射蟲,其中數量較多且特徵名顯的種有Dejlandrecyrtium carterae, n. sp. Eptingium (?) amoenum Carter, Ferresium philippinense, n. sp., Haeckelicyrtium karcharos Carter, Livarella densiporata Kozur and Mostler, Livarella gifuensis Yoshida, Parabipedis pessagnoi, n. sp., Pseudoheliodoscus huxleyensis (Carter),以及Risella tledoensis Carter。與前人之研究結果比較,到目前為止仍無論文報導在世界其他地區發現同一族群的記錄,但已知在有些年代相當的族群(例如曾分別在日本及加拿大發現的瑞替放射蟲族群)中也含有一些相似種。將其對比研究的結果顯示: 1)本研究族群與Yoshida在1986年發表的一個日本族群極為相似,日本含有這一個放射蟲族群的(石圭)質岩體很可能與菲律賓岩體源自同一海洋板塊; 2)本研究族群之年代應歸於晚三疊世早瑞替時代晚期(late early Rhaetian),以及3) Carter在1993年依加拿大放射蟲而界定的晚三疊放射蟲生物地層帶無法應用於本研究,因此本研究結果將為重新修正晚三疊放射蟲生物地層帶極為重要的參考資料。

並列關鍵字

三疊紀 瑞替時代 放射蟲

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