碩士 / 國立成功大學 / 地球科學系碩博士班 / 98 / In southwestern Taiwan, depositional system of Coastal plain and outer part of Foothills belt has been influenced by loading of the orogenic belt to the east from Pliocene to present and developed into a typical foreland basin system. In the study area, which is located at the distal and central parts of the foreland basin, the well bore data and outcropped sections record the changes of sedimentary facies within the foreland basin sequences. The changes were caused by the mixed variations of eustasy and activity of the orogenic belt during active/quiescent periods. Previous studies concerning the foreland basin in southwestern Taiwan mainly focus on the model of basin framework, and the accompanied orogenic morphology as well. The aim of this study is to analyze the sedimentary cycles and establish the tectonostratigraphy in foreland basin.
The Late Mio-Pleistocene strata composed by the lithological units from older to younger are Chunlun, Niaotsui, Yunshuichi, Liuchungchi, Kanshualiao and Erchungchi Formation, and they are deposited during the time of nannofossil biozone NN11-NN19. To study the sedimentary cycles of submarine deposits, we should recognize the sedimentary facies at first. According to the lithofacies analysis, the sedimentary facies are classified into six types: intertidal, subtidal, shoreface, offshore transition, offshore and flooding relict. Based on the trend of facies change, the environments can be divided into several sedimentary cycles. The cycles can be recognized and grouped into the system tracts, including the lowstnad (LST), transgressive (TST), highstand (HST), and falling-stage (FSST) systems tracts.
Stratigraphic columns were correlated and compared by analyzing the stratigraphic sequences, and a stratigraphic profile extending from the distal to central parts of the basin was then constructed. Twice rapid subsidence events are identified in sequence stratigraphic records of foreland basin.
In foreland basin, the rapid subsidence event is interpreted as the tectonic active period, and the FSST is preserved very well at this time. We interpret that the FSST results from relative sea-level fall caused by the approaching forebulge uplift. In each period of foreland basin development, TST was deposited at the higher rate of tectonic subsidence, which was followed by FSST representing the hinterlandward approaching forebulge. When tectonic activity in the orogenic belt gradually diminished, HST was deposited at the lower rate of tectonic subsidence and by the progradation toward the distal part of the basin till the end of the period. The assemblage of the foreland basin sequences (LST/TST/HST/FRST) demonstrates that tectonic activity has been dominant during its deposition, while another one (TST/HST) shows that it was rarely affected by tectonic activity and mainly influenced by eustasy.
Two elements compete with each other continuously, including tectonic activity and sea level changes, respectively. The tectonostratigraphy indicates that the foreland basin underwent two tectonic active period. The depositional position of the stratigraphy related to the former is the distal part near the forebulge, and it is belonging to uplifting and turned to rapid subsidence due to the forebulge moved to the craton. The depositional position of the stratigraphy related to the latter is the center of foreland basin, and belonging to rapid tectonic subsidence. However, the sea level changes turned to principal while entering second quiescent period. From the twice active period, we can speculate the timings of reverse fault rapid active events in neighboring orogenic belt are about 5.54Ma and 2.1Ma (NN12 and NN18, respectively).
| Identifer | oai:union.ndltd.org:TW/098NCKU5135153 |
| Date | January 2010 |
| Creators | Wei-ChengHuang, 黃緯誠 |
| Contributors | Kenn-Ming Yang, 楊耿明 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 126 |
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