Forebulge migration in late Cenozoic Western Taiwan Foreland Basin

Abstract

In the distal part of the Western Taiwan Foreland Basin, the forebulge is caused by emplacement and loading of the Taiwan orogenic belt onto a flexed Eurasian plate. Examining reflection seismic data collected from the shelf region in the Taiwan Strait, we present the merging of successive unconformities which is the result of regional uplift due to upwarp of flexural forebulge, erosion on elevated highs, and subsequent lateral shift of forebulge. The intersection points occurring along westward merging unconformities overstepped toward Chinese craton, representing cratonward migrations of a forebulge in the Western Taiwan Foreland basin. A hiatus map across foreland basal unconformity shows not only cross-strike increase in chronostratigraphic gap, but also a S-shaped distribution of similar hiatus intervals in the along-strike direction. Foreland basin sequence in the Taiwan Strait can thus be divided into two zones on the basis of seismic reflection patterns. The distal zone comprises flat-lying layers, while the proximal zone comprises feather-edging of reflection intervals and onlapping reflections. The current position of forebulge crest is suggested to be farther cratonward than that of the middle part of the Taiwan Strait. © 2011 Elsevier B.V.