[SCG64-P03] Interaction of forearc basin stratigraphy with growth of accretionary wedge: Insights from numerical simulations
Keywords:forearc basin, accretionary wedge, sediment flux, subduction zone
The constant taper models showed positive relationships between QinFAB with Qtotal (= Qs + QinT – QoutT) or QinAC. Underfilled basin could exist only when Qs was smaller than depositional area produced by the wedge growth. At a time of transition from underfill to overfill, trajectories of QinFAB and QinAC broke and then returned to the equilibriums with some fluctuations. The dynamic taper models also showed linear relationships between QinFAB and Qtotal, although QinAC and QinFAB relationships were much more scattered than the constant taper models. A prominent feature of the dynamic taper model was a negative relationship between time-averaged differences of QinAC and QinFAB, when θ was increasing or decreasing. The sediment input rates to the basins (QinFAB) decreased, even though those to the wedge (QinAC) increased with reducing θ. Similar negative relationships could be observed during increase of θ. These results suggest that growing wedge with changing the taper angle significantly affects the basin stratigraphy. Two end members of the wedge-growth patterns can be considered; (1) progradation by frontal accretion with decreasing θ and (2) vertical growth by basal accretion or thickening by splay faults with increasing θ. For the former type (1), most of QinT are consumed for progradation of the wedge to approach the reduced θ, resulting in slower sedimentation rate and then occurrence of a condensed section or an unconformity, even though sufficient Qs is supplied to the basin. The latter type (2) yields more space for sedimentation landward side of the wedge due to uplift of the outer arc high, which leads to faster sedimentation rate or occurrence of an underfilled basin, depending on Qs.