STUDIES OF RADIOLARIA FROM THE FIELDS CREEK FORMATION, EAST-CENTRAL OREGON, U.S.A.

三疊紀菲爾芝魁克層放射蟲之研究

葉貴玉(KUEI-YU YEH)

《Collection and Research》 1期 (1989/09) Pp. 43-109

https://doi.org/10.6693/CAR.1989.1.5

摘要

From the Fields Creek Formation, east-central Oregon, four major radiolarian assemblages wererecovered, they are the Ladinian PseudostyJosphaera magnispinosa Assemblage, Karnian Pou/pus karnicus Assemblage, Norian Corum parvum Assemblage, and an upper Norian or Hettangian fauna of Orbiculiform sp. A Assemblage. Characteristic species of each assemblage and other distinct radiolarian taxa including twenty three new species and four new genera are figuered and described in this report. The results of this study indicate that (1) the Fields Creek Formation was mainly deposited during Norian times, but the deposition of the Fields Creek sediment may have initiated from Ladinian times, or (2) the rocks contain Ladinian or Karnian Radiolaria represent the allochthonous blocks in the Fields Creek olistostromes.

並列摘要

本文乃奧瑞岡中部菲爾芝魁克層放射蟲研究結果之報告。菲爾芝魁克層乃該區中生代碎屑岩系列中規模最大，出露面積最廣的一層。本層堆積厚達5000米左右，但岩性以黑色泥岩為主，除發現過上部三疊紀的腕足類於轉石中外，尚未報導過其他大型化石的出現。黑色泥岩中所含的放射蟲在無形中為生物地層對比或解說板塊活動史的主要證據之一。根據分析之結果，菲爾芝魁克層中含有四個放射蟲族群，分別為中部三壘紀Karnian Poulpus，上部三壘紀Karnian Poulpus karnicus，上部三疊紀mid-die Norian Corum parvum族群，以及可能為下部侏羅紀Orbiculzjorma sp. A族群。其中新命名的有二十三種及三個新屬。本研究指出: (一)菲爾芝魁克層的沉積主要發生於上部三疊紀晚期Norian時代，(二)中部三疊紀或上部三星紀初期的放射蟲應為洋底大規模滑落再沉積作用的產物;(三)至於下部侏儸紀化石的出現可能指示侏儸紀的凱樂魁克頁岩層應比前人所劃定的區域再向西側延伸。