Sedimentary and structural features in southwest Taiwan orogen 

                                                     Gang-Yu Chan

                                                Abstract

                    The depozone in the southern Taiwan foreland basin system is confined by the 
                  topographic front of the Chaochou Fault to the east and by a submarine deformation 
                  front to the west. The northern boundary of the wedge-top depozone in southern 
                  Taiwan is placed along the southern limit of the Western Foothills where the frontal 
                  orogenic wedge progressively changes southward to a wedge-top depozone (Pingtung 
                  Plain), reflecting ongoing southward oblique collision between the Luzon Arc and the 
                  Chinese margin. The wedge-top depozone is bounded to the south by the continent 
                  -ocean crust boundary. The deep slope west of the Hengchun Ridge can be viewed as 
                  an infant wedge-top depozone, showing initial mountain building and the beginning 
                  of wedge-top depozone.

                   The Hsinhua structure, The Tainan anticline, and the offshore H2 amticline ate the 
                  first group of major culminations in the westernmost part of the Fold-and-Thrust belt 
                  that formed during the Penglay Orogeny. Structures in the the Tainan and Kaohsiung 
                  areas provide important features of the initial mountain building stage in Western 
                  Taiwan. A typical triangle is found by back thrusting, such as where the Hsinhua Fault 
                  cuts upsection of the Upper Pliocene and Pleistocene from a lower detachment along 
                  the lower Gutingkeng Formation. The triangle zone stops at H2 anticline offshore
                  Tainan and beyond the west of it. On the basal detachment, a major ramp interpreted 
                  as a tectonic discontinuity was found. Above the northeastern end of the major ramp 
                  of basal detachment, the Lungchuan Fault is associated with a triangle system 
                  development, while at the southwestern end a thrust wedge is present. It could be 
                  deduced that a thrust wedge intrudes northwestward. The area below the major ramp,
                  or equivalent to the trailing edge of the basal detachment, mud diapirs often occur in 
                  relation to the thickest deposits of the Gutingkeng Formation and caused by the 
                  mechanism of detachment floding.

                                                Reference

                  Cheng-Shing Chiang, Ho-Shing Yu & Ying-Wei Chou, 2004, Characteristics of the 
                  wedge-top depozone of the southern Taiwna foreland basin system, Basin research 
                  16, 65-78

                                                   (Abstract)(Full text)

                  Shiuh-Tsann Huang et al., 2004, Deformation front development at the northeast 
                  margin of the Tainan basin, Tainan-Kaohsiung area, Taiwan, Marine Geophysical 
                  Researches 25,139-156

        
                                                   (Abstract)(Full text)