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標題: | 臺灣北部大漢溪剖面更新世卓蘭層至楊梅層之生痕化石分析 Trace fossil analyses of the Pleistocene Cholan Formation to Yengmei Formation in Dahan River section, Northern Taiwan |
作者: | 葉尚榮 Shang-Rong Ye |
指導教授: | 林日白 Jih-Pai Lin |
關鍵字: | 生痕化石,生痕化石群落,更新世,前陸盆地,沉積層序, Trace fossil,Ichnocoenoses,Pleistocene,Foreland basin,Depositional sequences, |
出版年 : | 2024 |
學位: | 碩士 |
摘要: | 自蓬萊造山運動以來,山脈前緣的前陸盆地接收大量來自造山帶的沉積物,造山運動的過程,因構造活動及浮體均衡,促使增積楔形體增厚抬升,山脈向西持續擴展,逐漸將老的前陸盆地沉積物褶皺隆起,形成新的山脈前緣—外麓山帶。本研究探討的卓蘭層至楊梅層,是位於北部外麓山帶,屬於更新統,年代始於2.6 Ma。由於前陸盆地呈現高沉積速率,且受米蘭科維奇氣候循環作用影響,形成第五級沉積層序。
因此,本研究欲利用生痕化石族群(assemblage)的擾動程度、多樣性和豐度等各種特性,並配合沉積構造及岩性,建立具有次環境意義的生痕群落(ichnocoenosis),且依照沉積環境的由淺至深分為 Psilonichnus、Thalassinoides、Ophiomorpha、Cylindrichnus、Teichichnus 和 Scolicia 等六種生痕群落。之後,從沉積層序的變化來探討生痕群落的演變及環境變遷的關係。 根據層序的生痕群落變化,可以分為A、B、C三種類型。海進時,A類型的生痕群落演變過程為 Thalassinoides → Ophiomorpha → Teichichnus生痕群落,其沉積環境從潮間帶、潮下帶演變至遠濱過渡帶。B類型的生痕群落演變過程為 Ophiomorpha → Cylindrichnus → Teichichnus → Scolicia生痕群落,其沉積環境從潮下帶、遠濱過渡帶演變至上部遠濱帶。上述兩種類型在高水位體系域後期,海退的情況略為相同,因此A與B類型海退時的生痕群落演變過程為Cylindrichnus → Ophiomorpha → Thalassinoides 生痕群落,其沉積環境從潮下帶演變至潮間帶。C類型的生痕群落演變過程為海進時的Ophiomorpha → Psilonichnus → Thalassinoides生痕群落,但Thalassinoides較不常出現,其沉積環境由陸相河道轉為潮坪或氾濫平原;海退時的生痕群落組合為Psilonichnus → Ophiomorpha生痕群落,沉積環境由氾濫平原轉為陸相河道。此類型因受到海水面變動的影響較小,僅有在海進時可能轉為 Thalassinoides生痕群落,才有較多的生痕出現。 Since the Penglai orogeny, the foreland basin at the front of the mountain range has received a large amount of sediment from the source region in the mountain. In the process of orogeny, due to tectonic activity and isostasy, the mountain range continues to expand westward, gradually uplifting the older foreland basin deposit, forming Western Foothill. Studied strata, covering from the Cholan Formation to the Yengmei Formation, are Pleistocence in age and located in the outer belt of Western Foothill, since 2.6 Ma. Due to the high sedimentation rate influenced by the Milankovitch cycles in the foreland basin, fifth-order sedimentary sequences have been noted. This study aims to use various characteristics of trace fossil assemblages, such as bioturbation, diversity, and abundance, combined with sedimentary structures and lithology, to establish ichnocoenosis with subenvironmental significance. Six ichnocoenoses—Psilonichnus, Thalassinoides, Ophiomorpha, Cylindrichnus, Teichichnus, and Scolicia—are classified from shallow to deep marine based on sedimentary environments. Subsequently, the evolution of ichnocoenosis and their relationship with environmental changes are explored through changes in depositional sequences. The ichnocoenoses evolution of depositional sequences can be divided into three types. Type A consists of Thalassinoides → Ophiomorpha → Teichichnus, belonging to marine sequence with sedimentary environments ranging from the intertidal and subtidal to offshore transition during transgression. Type B consists of Ophiomorpha → Cylindrichnus → Teichichnus → Scolicia, belonging to marine sequence with sedimentary environments ranging from subtidal and offshore transition to upper offshore during transgression. Following with highstand system tract for both A and B types the ichnocoenosis successions are somewhat similar during regression. Thus, the ichnocoenosis successions for both A and B types consist of Cylindrichnus → Ophiomorpha → Thalassinoides, belonging to a marine sequence with sedimentary environments ranging from subtidal to intertidal during regression. Type C consists of Ophiomorpha → Psilonichnus → Thalassinoides, but Thalassinoides less commonly present, belonging to continental sequence with sedimentary environments ranging from a continental channel to a tidal flat or floodplain during transgression. Following by regression Type C consists of Psilonichnus → Ophiomorpha, belonging to continental sequence with environments ranging from floodplain to continental channel. This type of trace fossil is less influenced by changes in sea level, with more trace fossils appearing only in the Thalassinoides ichnocoenosis during transgression. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/92013 |
DOI: | 10.6342/NTU202400470 |
全文授權: | 同意授權(限校園內公開) |
顯示於系所單位: | 地質科學系 |
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