Sedimentology of early Pliocene sandstones in the south-western Taiwan foreland: Implications for basin physiography in the early stages of collision

Abstract

a b s t r a c tThis work presents sedimentological observations and interpretations on three detailed sections of the Pliocene Yutengping/Ailiaochiao formations, deposited in the early stages of collision in Taiwan. Seven facies associations record paleoenvironments of deposition ranging from nearshore to lower offshore with a strong influence of tidal reworking, even in shelfal sub-tidal environments, and a pro-delta setting characterized by mass-flows. The association of shallow facies of the upper offshore to lower shoreface with pro-delta turbidite facies sourced in the orogen to the east suggests a peculiar setting in which turbidite deposition occurred below wave base but on the shelf, in water depths of probably less than 100 m. This adds to the examples of ''shallow turbidites" increasingly commonly found in foreland basins and challenges the classical view of a ''deep" early underfilled foreland basin. Time series analysis on tidal rhythmites allow us to identify a yearly signal in the form of periodic changes of sand-supply, energy and bioturbation that suggests a marked seasonality possibly affecting precipitation and sediment delivery as well as temperature. The Taiwan foreland basin may also present a potentially high-resolution record in shallow sediments of the early installation of monsoonal circulation patterns in east Asia. We confirm partly the paleogeography during the early stages of collision in Taiwan: the Chinese margin displayed a pronounced non-cylindrical geometry with a large basement promontory to the west in place of the modern Taiwan mountain range. Collision in Taiwan may have happened at once along the whole length of the modern mountain range, instead of progressively from north to south as classically considered.

Subduction of a buoyant plateau at the Manila Trench: Tomographic evidence and geodynamic implications

“…These observations indicate that the buoyant plateau does not stop but merely slow down the subduction of the Eurasian Plate. The current phase of active orogenesis in Taiwan is generally assumed to have begun 5–6 Ma ago [e.g., Teng , ; Castelltort et al ., ], which is concurrent with the initial subduction of the hypothesized buoyant plateau. These results suggest that the Taiwan Orogeny originates directly from the subduction of the buoyant plateau [ McIntosh et al ., ].…”

Mountain Building in Taiwan: Insights From 3‐D Geodynamic Models

“…These differences are probably caused by the difference in erosion rates. First, the erosion/sedimentation rates are supposed to vary among Taiwan based on the stratigraphic and sedimentary studies (e.g., Castelltort et al, 2011;Huang et al, 1995;Lin et al, 2003;Lundberg & Dorsey, 1990;Tensi et al, 2006) and studies of fission-track data (e.g., Dadson et al, 2003;Lee et al, 2006;Willett et al, 2003). Willett et al (2003) calculated erosion/exhumation rates in the range of 3-6 mm/year in the eastern CR and 1.5-2.5 mm/year in the western CR since~1 Ma.…”

Late Cenozoic metamorphism and mountain building in Taiwan: A review

“…In any case, comparing the different transects across the Taiwan wedge to discuss any type of steady state usually implies that the southward propagation of the collision and mountain building has been stationary over time, a concept that has been recently challenged (e.g. Castelltort et al, 2011).…”

“…The collision is very young (4-8 Ma (Chi et al, 1981;Lin et al, 2003;Sibuet and Hsu, 2004)) and propagates southward at a rate estimated to 31-60 mm/yr (Byrne and Liu, 2002;Simoes and Avouac, 2006), although the stationarity of the propagation has been recently questioned (Castelltort et al, 2011). To the north of Taiwan, because of the reversal of the subduction polarity (Suppe, 1981(Suppe, , 1984 with the Philippine Sea plate subducting beneath Eurasia along the Ryukyu trench, shortening is no longer active across the Taiwan mountain belt (Yu et al, 1997), which is then disrupted by active normal faults (Shyu et al, 2005;Suppe, 1984).…”

“…Shyu et al, 2005;Simoes et al, 2007b,c;Yue et al, 2011), sedimentary (e.g. Castelltort et al, 2011;Covey, 1984aCovey, ,b, 1986) and basin analysis (e.g. Lin et al, 2003;Simoes and Avouac, 2006) studies of the foothills and foreland basin to the west.…”