Development of Mass-transport Deposits in Deep-water Areas of the Continental Margin:Insights from numerical stratigraphic forward modelling of the Late Quaternary Pearl River margin
[Objective]As an important part of the continental-margin strata,mass-transport deposits(MTDs)at-tract considerable attention from researchers worldwide.However,previous studies rarely related the development of MTDs to the building of depositional sequences.This study took SQ4 and SQ5 on the Late Quaternary Pearl River margin as the study objects to investigate the influence of different sequence-building backgrounds on the develop-ment of MTDs.[Methods]Through the integrated method of seismic interpretation and numerical stratigraphic for-ward modelling,MTDs are shown to primarily occur in the deep-water reaches of SQ4,whereas in the deep-water part of SQ5,they rarely occurred.Near the shelf-slope break,the existence of different systems tracts suggests that highstand system tracts in SQ4 are highly developed compared with their counterparts in SQ5.Based on the real con-dition of the Late Quaternary Pearl River margin,a total of 45 modelling experiments with varying relative sea-level changes were designed in Software DionisosFlow 2016 to investigate the development of mass-transport deposits for different backgrounds of depositional sequence building.[Results]The results prove that for high sediment supply(with sediment discharge being 5000 km3/My and water discharge being 1200 m3/s)and high amplitude of relative sea-level changes(up to 250 m),the development of MTDs is sensitive to the development of highstand systems tracts during sequence building;When highstand systems tracts are longer and experience sufficient development,MTDs are easily formed in deep-water areas,which is in consistent with the real condition of MTDs within SQ4 and SQ5.[Conclusions]Moreover,the models representing SQ4 and SQ5(Model C8 and Model E5)further explain the occurrence mechanism of MTDs.During the building of SQ4,highstand system tracts are fully developed(with the duration of highstand systems tracts accounting for 65%of the elapsed model run),and the associated delta-shoreline systems overreach the shelf break,causing delta fronts to merge onto the continental slope and form clinothems with high reliefs and slopes;those clinothems are highly unstable and drive the occurrence of mass wasting processes,leading to the deposition of MTDs in deep water.During the building of SQ5,the development of highstand systems tracts is limited(with the duration of highstand systems tracts accounting for 40%of the elapsed model run),and the associated delta-shoreline systems prograde to the outer shelf but do not overreach the pre-existing shelf-slope break,forming clinothems with low reliefs and slopes,which disfavor the occurrence of mass wasting processes and the development of MTDs in deep water.Those controls of different sequence-building backgrounds on the formation of MTDs in deep water provide a useful method for predicting thesubmarine depositional elements,which are important for hydrocarbon exploration and development in the future.
mass-transport depositsdepositional sequence buildingstratigraphic forward modellingPearl River marginLate Quaternary
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