台灣中北部晚期中新世以來古沉積環境與前陸盆地之演變-栗林構造層序地層與生物地層之分析

Post Late Miocene Sedimentary Environment and Foreland Basin Evolution in Northern and Central Taiwan--Sequence Stratigraphy and Biostratigraphy of the Lilin Structure

吳榮章(J.-C. Wu)

指導教授 ： 李通藝

國立臺灣師範大學/理學院/地球科學系/博士(2009年)

摘要

層序地層學為震測地層學引入沉積體系的觀念，將震測反射相與相應的沉積相劃分為層序和沉積體系，並依照相對海平面升降之海進、海退旋迴，劃分為低水位、海進、高水位及陸棚邊緣體系，並依照沉積物堆積體系和岩相，結合震測、井下電測以及野外露頭資料，以整合解釋盆地內的沉積物岩相分佈，作為推斷儲集岩、生油岩、蓋層及可能地層封閉位置之重要參考。
本研究除對台灣西北部進行層序地層分析外，並特別針對首次在栗林構造所發現之關刀山砂岩丘狀砂體水下扇，對其成因、特性、沉積模式及油氣潛能作深入探究。而由研究結果得知，台灣西部麓山帶附近的確存在低水體系域較深水部分之諸單元；這幾個單元發育完善，生油、儲油、蓋層及封閉組合兼備，應有極高之油氣生產潛能。且台灣西北前陸盆地的肇始（即前淵沉積水深大幅增加或坡度變陡的時間），應較前人研究所推論的時間為早，大約在關刀山砂岩沉積的時候開始 （晚中新世）這個結果，亦將對台灣新第三紀造山帶的瞭解有更深入釐清及重要的影響。
從栗林一號井附近的震測解釋，加上電測解釋的結果，配合層序地層分析栗林一號井之超微化石及有孔虫化石的詳細分析，判定從電測剖面、震測剖面及層序分析中之桂竹林層下段關刀山砂岩所形成之扇狀堆積並非很深之海洋海底平原之濁流沖積扇，而是在蓬萊運動早期形成的斜坡之水下扇(Submarine fan)。本研究提出相關之沉積模式分析；目前除分析其他井下層序地層及建構台灣西北部層序地層架構外，並進一步探討台灣弧－陸碰撞之肇始和前陸盆地沉積之發育情況。

關鍵字

生物地層 ； 層序地層 ； 栗林構造 ； 前陸盆地 ； 台灣中北部

並列摘要

Sequence stratigraphy revitalizes the concepts of depositional systems in the context of seismic stratigraphy by dividing the seismic facies and their corresponding sedimentary facies into systems tracts, namely, lowstand, transgressive, highstand and shelf-margin systems tracts based on relative sea-level fluctuation and transgression- regression cycles. Seismic, well log and field data can be integrated into the theory of sequence stratigraphy, on the basis of depositional systems and sedimentary facies, to give comprehensive interpretations of the distribution of depositional architectures in a basin, which would be the most important references for investigating the locations of reservoirs, source rocks, cap rocks and potential stratigraphic traps.
In addition to the sequence stratigraphic analysis of the newly discovered Upper Miocene Kuantaoshan Sandstone submarine fan in Lilin Structure at northwestern Taiwan, this study particularly addresses in details about the formation, characteristics, sedimentary model, and hydrocarbon potential of the fan. The study results indicate that the Foothills belt and its adjacent areas in northwestern Taiwan were once in a setting suitable for the development of the deeper portions of lowstand systems tract (basin-floor fan, slope fan, shingled turbidites and prograding complex). This setting is perfect for hydrocarbon generation, accumulation, seal and trap, and should be a prime target for hydrocarbon exploration as well. Besides, the initiation of the foreland basin in northwestern Taiwan, i.e., the timing of sudden increase in water depth or depositional slope in the foredeep, should be at the very beginning of the deposition of the Kuantaoshan Sandstone (Late Miocene). This timing is a bit earlier than that inferred by the previous studies, however, is consistent with the igneous records on Taiwan and neighboring areas. The study results will shed some lights on the Penglay Orogeny in Taiwan.
According to the results of seismic and well log interpretations of the data from the Lilin well no.1 and nearby areas, plus the detailed analysis of nanno and foraminifera fossils from the wells in the same region, it is plausible to conclude that the deposits of mount-shaped fan in the Kuantaoshan Sandstone of the lower Kuechulin Formation is not from a turbidity source in the abyssal plane but from a submarine fan formed on the deepened slope at the earliest stage of the Penglay Orogeny. Other than the sequence stratigraphic study of the wells in northwestern Taiwan, this study further investigated the depositional models for the wells in central Taiwan. Tectonic and depositional models for the initiation of the arc-continental collision and the contemporaneous evolution of sedimentary records in the foreland basin in Taiwan have also been proposed by this study. The ultimate model for the foreland depositions contained two deepening and shallowing cycles which were identical with the general sea level fluctuation patterns from Late Miocene to Present. Therefore, the depositional configurations might have been generated by tectonic activities but largely modified by eustatic sea level variations.

並列關鍵字

Biostratigraphy ； Sequence Stratigraphy ； Lilin Structure ； Foreland Basin ； Northern and Central Taiwan

參考文獻

Scholle, P.A., and Spearing, D.R., 1982; Sandstone depositional environments, Memoir 32 - American Association of Petroleum Geologists, Tulsa, OK, p. 410.

Wilgus, C.K., Hastings, B.S., Posamentier, H., Wagoner, V., Ross, C.A., and Kendall, G.S.C., 1988, Sea-level changes: An integrated approach: Tulsa, Oklahoma, Society of Economic Paleontologists and Mineralogists Special Publication #42, 407 p.

Aitken J f. Flint S S. The application of high resolution sequence stratigraphy to fluvial systems: A case study from the Upper Carboniferous Breathitt Group, eastern Kentucky, USA. Sedimentology, 1995, 42: 3～30.

American Association of Petroleum Geologists Bulletin, v. 87, p. 1169-1191.

Bouma, A.H., Normark, W.R., and Barnes, N.E., 1985, Submarine fans and related turbidite systems: New York, USA, Springer-Verlag, 343 p.