Temporal and spatial records of active arc-continent collision in Taiwan: A synthesis Chi-Yue Huang† Department of Earth Sciences, National Cheng Kung University, Tainan, Taiwan Peter B. Yuan Institute of Marine Geology and Chemistry, National Sun Yat-Sen University, Kaohsiung, Taiwan Shuh-Jung Tsao Central Geological Survey, MOEA, Taipei, Taiwan ABSTRACT earliest Pleistocene, as marked by the west- Grady, 1981; Liu, 1982; Liu et al., 2001; Lo and ward thrusting and accretion of the Luzon Yu, 1996; Wang et al., 1998; Hill and Raza, 1999; Well-documented stratigraphy and clearly arc-forearc against the accretionary wedge Ring et al., 1999; Harris et al., 2000; Willett et defi ned geodynamics in Taiwan, where some (north, 1.5 Ma; south, 1.1 Ma) and exhuma- al., 2003). However, in many arc-continent col- of the best records on arc-continent collision tion of the underthrust Eurasian continent lision belts, multiple stages of metamorphism, have been preserved, offer a unique example rocks (north, 2.0–1.0 Ma; south, 1.0–0.5 Ma). overprinting deformation, complicated tecton- for the study of collision belts worldwide. The fi nal stage of the tectonic process, arc ics, and inadequate age markers have obliterated The oblique arc-continent collision in Tai- collapse-subduction, began by 1 Ma off the or obscured most geologic records. wan caused a simultaneous and sequential northern Coastal Range. The geology of Taiwan is well known for its migration of four tectonic processes. Begin- The geologic records compiled and pre- active and oblique collision between the Luzon ning from 16 to 15 Ma, subduction of the sented in this study strongly support the Arc and the Eurasian continental margin (Fig. 1; South China Sea oceanic crust beneath the scenario of a continuous southward migra- Chai, 1972; Biq, 1973). The presence of an off- Philippine Sea plate resulted in volcanism tion of tectonic processes and a change in shore modern analog further allows Taiwan to in the Coastal Range and formation of an sediment source and structural style. Most offer one of the clearest overviews of arc-conti- accretionary prism in the Central Range. importantly, the model has a broad poten- nent collision (Huang et al., 1992, 2000). Beginning in the latest Miocene–earliest tial for reconstructing and predicting the Synthesizing new evidence and published Pliocene, the subduction was followed by ini- evolution of arc-continent collision through data, we present temporal and spatial records tial arc-continent collision, as supported by space and time. that support a persistent southward propagation the following: unroofi ng and erosion of the of the collision process, which in turn accounts deformed accretionary prism, and deposi- Keywords: Taiwan, arc-continent collision, for the sequential emergence and creation of tion of sediments thus derived in the adja- oblique collision, stratigraphic records, col- Taiwan. Other recent interpretations of the tec- cent accretionary forearc (5 Ma) and slope lision suture. tonic evolution of Taiwan are also compared basins (4 Ma); waning of volcanism (north, 6–5 Ma; south, 3.3 Ma); buildup of fringing INTRODUCTION reefs on the gradually quiescent volcanoes (north, 5.2 Ma; south, 2.9 Ma); arc subsid- Tectonic processes associated with arc-conti- Figure 1. Tectonic framework and the four ence by strike-slip faulting and the develop- nent collision can be recognized by the shifting geodynamic processes involved in the arc- ment of pull-apart intra-arc basins (north, of sediment provenance, deformation of arc- continent collision in the Taiwan region. 5.2–3.5 Ma; south, 2.9–1.8 Ma); thrusting forearc and accretionary wedge, abrupt change Refer to Huang et al. (2000) for details of of forearc sequences to generate a collision of sedimentation rate and depositional bathym- tectonic processes and their geological- complex starting from 3 Ma; and clockwise etry in forearc or foreland basins, and the inten- geophysical characteristics. A and B are rotation of the arc-forearc sequences (north, sity of arc volcanism (Teng, 1979; Charlton et locations for fi ssion-track studies (Fig. 9) 2.1–1.7 Ma; south, 1.4 Ma). The collision al., 1991; Abbott et al., 1994; Huang et al., 1995; along the Central and Southern Cross- propagated southward and reached southern Yang et al., 1995; Brown and Spadea, 1999). Island Highways. TT—Taitung Trough; Taiwan by 5 Ma, as evidenced by the succes- Geochemical studies, such as fi ssion-track and SLT—South Longitudinal Trough; CFS— sive deformation of the associated accretion- argon-isotope dating, and pressure-tempera- Chingshui fault scarp; arrow: magnetic dec- ary wedge en route. Afterward, the advanced ture-time path analyses on the underthrust con- lination. Compiled from Yang et al. (1983), arc-continent collision stage appeared in the tinental rocks in convergent zones, also can be Lee et al. (1991), Huang et al. (1992), Reed et used to reconstruct this exhumation history after al. (1992), Liu et al. (1998), Lallemand et al. †E-mail: [email protected]. subduction and subsequent collision (Berry and (1997, 1999), Malavieille et al. (2002). GSA Bulletin; March/April 2006; v. 118; no. 3/4; p. 274–288; doi: 10.1130/B25527.1; 9 fi gures; 1 table; Data Repository item 2006042. 274 For permission to copy, contact [email protected] © 2006 Geological Society of America TAIWAN COLLISION Tectonic Map of Taiwan 25 n a Ryukyu ~~~~~~~~~~~ w Ar c Tai Fold-and-thrust belt c ar Ryukyu T. 25° N Okinawa h (Passive Asian continental margin) c Chuchih fault zon Pleistocene-Holocene foreland Hsingchuang fault vTrough Lu 20 Tr en Miocene-Pleistocene shallow neritics Paleogene shallow neritics nila fault Ma Accretionary prism 125 (Deep marine slope-trench sequences) v v Luzon Ryu Miocene slate and turbidites kyu Subduction complex Arc-arcArc Arc Underthrust Eurasian continent A collapse/Collisionsubduction Hsüehshan Range CFS Eocene Ss-Ls-Sl V FoothillsFoothills e Pre-Tertiary metamorphic V basement Accreted Luzon arc-forearc Rang 24° N an y Forearc Hsuehshan V Range Hoping-Nanao-Forearc V V Collision complex Lish Central Volcanic arc Valle lain V P al Coastal Plain Yaeyama Basin V V Coastal Plain Central Range V RyukyuRidg Coastal e Longitudin V stern V Western V Ryukyu Tren Trench Western Foothills We V ch lRange Advanced V V V V arc-continent collision Lichi melange Coasta V V TAIWAN Longtudinal 23° N V V B V V ACCRETIONARY V in V V V fault Laonung fault Lichi TT PRISM V Pingtung g Taitung mélange Lutao Valley V 82 km/ m Laonun .y. V Arc a V Lanhsu Huatung Bas V T V ary Hengchun Ridge Peninsul SL 22° N V V V Initial V Kenting V Fold-and-thrust Mélange arc-continent collision Sea V V V arc-prism bound V Huatung V Kaoping Ridge V Luzon V V Slope V prism V V V Hengchun V V V V Intra-oceanic subduction 21° N retionary V V V V Acc V V V V V Trough Philippine basin) V V V V South V Batan V V V V V Luzon (Forearc V V V China V North V V V V V V North V Sea Trench Manila 20° N 119°E 120° E 121° E 122° E Geological Society of America Bulletin, March/April 2006 275 HUANG et al. and discussed, thus providing a comprehensive and Malavieille et al., 2002), which traverses (Fig. 2) and consists of three extinct volca- perspective on the time, space, and processes the collisional suture basin (South Longitudinal nic islands, three associated remnant forearc involved in this unparalleled collision terrain. Trough) and may correspond to the Longitudi- basins, two intra-arc basins, and a mélange nal Valley fault on land (Figs. 1 and 2). sequence derived from the shearing of forearc TECTONIC SETTING OF TAIWAN Bounded on the west by the Manila Trench, sediments (Huang et al., 1995, 2000; Chang et the Hengchun Ridge and Kaoping Slope widen al., 2000, 2001). Tectonics in the Taiwan region is character- northward as more sediments on the Asian ized by two opposite subduction systems: The continental slope and South China Sea Basin DATABASE Eurasian continent–South China Sea oceanic are progressively incorporated into this accre- crust (all on the Eurasian plate) subducts east- tionary prism. Diverse interpretations of the evolution of the ward beneath the Philippine Sea plate along the arc-continent collision in the Taiwan region have N-S-trending Manila Trench, whereas the Phil- Tectonostratigraphy of Taiwan been proposed. They were established either ippine Sea plate subducts northward beneath from limited fi eld data (e.g., paleomagnetism or the Eurasian plate along the E-W-trending Two major boundary faults are found in Tai- radiometric dating; Wang, 1976; Liu, 1982; Liu Ryukyu Trench (Fig. 1). Continuous subduc- wan (Fig. 1): The Lishan-Laonung fault, sepa- et al., 2001; Teng, 1990; Lee et al., 1991; Lo and tion brought the Luzon Arc closer to the edge rating the Hsuehshan Range–Western Foothills Yu, 1996; Wang et al., 1998; Huang et al., 1995, of the Eurasian continent and resulted in their and the Central Range–Hengchun Peninsula, 1997; Chang et al., 2001) or from marine survey collision in the late Neogene (Chai, 1972; Biq, marks the subduction suture that prevailed and modeling without stratigraphic evidence 1973). Because the Asian continental margin before the arc-continent collision (8.5 Ma). To (Lallemand et al., 1999; Chemenda et al., 2001; (trending N 60°E) is oblique to the N-oriented its east the Longitudinal Valley fault between Malavieille et al., 2002). In contrast, based on Luzon Arc, and the Philippine Sea plate moves the Central Range and the Coastal Range is the the progressive change of geological and geo- toward 310°–305°, the arc-continent collision collision suture formed during the advanced physical features within the modern active col- has been diagonal; hence the point of collision stage of collision (<2 Ma).