Evidence of Early Cretaceous transpression in the Sulu orogenic belt

Abstract

Recent studies have documented marine turbidites with syn-sedimentary deformation features in the central Sulu orogenic belt of eastern China (Fu et al., 2010; Wu et al., 2010; Lu et al., 2011; Wang et al., 2014). These units preserve essential information on the Late Mesozoic evolution of the Sulu orogenic belt. Referred to as the Baxiandun Formation, turbidites exhibit similar lithologic characteristics to nearby units such as the Lingshandao Formation that have been well studied but precise geochronologic constraints are lacking in this formation for a more precise correlation. This study reports detrital zircon U-Pb age data that correlate the Baxiandun Formation turbidites of the central Sulu orogenic belt to the Early Cretaceous Lingshandao Formation. We also report Al-in-hornblende emplacement depth estimates for granitic intrusions of the Sulu orogenic belt’s Laoshan mountain. A sharp contact between the Laoshan granites and the marine Baxiandun Formation indicates that the Baxiandun basin rapidly subsided to the emplacement depth of the Laoshan plutons. Lateral correlation among marine turbidites, the Lingshandao and Baxiandun Formations, combined with information established by previous studies indicates initiation of transpressional tectonics at 122-121 Ma. Transpression ceased with the emplacement of the Laoshan granites, whose A1-type composition indicates a return to extensional tectonics at ca. 111 Ma.