Stratigraphic Architecture and Depositional Evolution of the Tai-Yuan Basin, Southern Coastal Range
Date Issued
2015
Date
2015
Author(s)
Lai, Larry Syu-Heng
Abstract
Located in southern Coastal Range of eastern Taiwan, the Tai-Yuan Basin is one of the arc-continent collisional forearc basins in the Luzon Arc between the Eurasian and the Philippine Sea plates. These basins are composed of Miocene volcanic basement (Tuluanshan Formation) sharply overlain by over 5 km thick Plio-Pleistocene siliciclastic sedimentary rocks (Fanshuliao Formation and Paliwan Formation) which recorded the geotectonical evolution of the Taiwan Orogeny. Despite the stratigraphic system has been established, the regional lithostratigraphic correlation and the depositional evolution of the basin are not well understood. For this purpose, this study first reexamines the stratigraphic subdivision, then discusses the sources and sedimentary processes of marker beds by deposits composition, paleocurrent and paleoslope analysis. Finally, an explanation of depositional history of Tai-Yuan Basin is proposed. The Fanshuliao Formation and Paliwan Formation contain sandy to muddy turbidites and several widespread marker beds, including 5 pebbly mudstones (Pm1 to Pm5) and 12 tuffaceous layers (T0 to T11). Based on these marker beds, this study subdivides Paliwan Formation into the lower, middle, and upper sections. In the turbidites facies, considerable lateral change of the sand to mud ratio could be recognized. According to the paleocurrent analysis, these turbidite are mainly derived from the north, partly from north-eastern source. The pebbly mudstones facies are originated by slumping and related debris flow processes in submarine canyon/slope or near slope environments. The results of paleocurrent and clast composition analysis imply that all pebbly mudstones were derived from northern instable slopes, where is at volcanic arc side for Pm1, Pm4, and Pm5, and at Taiwan orogenic wedge side for Pm2 and Pm3. The tuffaceous layers, which are mainly turbidites or debrites, are only discovered within the Paliwan Formation. Based on petrographic data, paleocurrent analysis and thickness variations, the volcanic clasts are considered to be derived from south-eastern side source, which could be Lutao volcano. Furthermore, the paleoslope analysis result shows that this basin was shaped by western orogenic wedge slope and eastern volcanic arc slope, and several slumped sturctures were formed by frequently slumping events. By integrating the above-mentioned, this study provides a new evolution model of Tai-Yuan Basin. Prior to the arc-continent collision, the subduction and arc volcanism subsided, and the arc andesite basement (Tuluanshan Formation) was established. The collisional orogeny started to grow around early Pliocene. During this period (4.0-1.4 Ma), lots of clasts eroded form the nortern mountain belts and submarine slopes were transported into the basin and formed Fanshuliao Formation and Paliwan Formation turbidites and pebbly mudstones Pm1 to Pm5. At around 2.13 to 1.4 Ma, several biotite-containing tuffaceous layers produced by eruptive events of the south-eastern side volcano are recorded in the sequence. As the collosion propogated toward the south, the Tai-Yuan forearc basin was progressively closed and accreted to the orogen, which eventually grew up to its present appearance.
Subjects
Coastal Range
Tai-Yuan Basin
Stratigraphic Architecture
Depositional Evolution
Basin Analysis
SDGs
Type
thesis
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