Sequence Stratigraphy And Sedimentary Facies Analysis Of Middle Devonian-Early Carboniferous Strata,in The North Of Fitzory Trough,Canning Basin,Western Australia

The Late Devonian-Early Carboniferous strata in Lennard Shelf and Fitzory Trough which contains rich conventional and unconventional oil and gas resources,is the main exploration target of Canning Basin.Based on the theory of Sequence sequence and sedimentology,through the comprehensive analysis of the data related to logging,drilling,cores and thin sections,this thesis will identify sedimentary facies,identify sequence boundaries and divide sequence stratigraphy,establish sequence stratigraphic framework,study the sedimentary facies characteristics of different tectonic units within sequence stratigraphic framework,and finally summerise its sedimentary filling evolution.The Late Devonian-Early Carboniferous strata mainly developed carbonate platform,delta and gravity flow sedimantary system.Carbonate platform sedimantary system can be subdivided into tidal flat facies,lagoon facies,open platform facies,platform-margin reef and bank facies,foreslope facies,open shelf-basinal facies.Fluvial-delta deposition system can be subdivided into delta plain facies,delta front facies and prodelta facies.Gravity flow sedimantary system can be divided into alluvial fan-subaqueous fan and turbidite fan.The Late Devonian-Early Carboniferous strata is a Megasequence,and can be further dividied into 5 Supersequences(SSQ1-SSQ5)and 16 sequences(SQ1-SQ16).After the Price Creek Compressional Movement,the study area began to slowly subside,and delta developed during the SSQ1 Period.During the SSQ2 period,the Fitzory Trough subsided rapidly and transgression happened in the Lennard Shelf.Isolated reef platforms(Pillara reef complex)developed around the ranges which located in the northern margin and inner Lennard shelf.The reef growth was characterised by aggradation-retrogradation.In the early stage of SSQ3,upward tilting of the faulted blocks occured and produced thick coarse clastic sediments which deposited in the embayment areas.As tectonic conditions stablised,siliclastic detritus reduced so that a broader reef rimmed platform developed,then strongly prograded and eventually exposed.In the early stage of SSQ4,a large number of turbidite fans(Clanmeyer Formation)infilled the embayments and as sea level rose a regressive carbonate platform developed on the Lennard Shelf and eventually become flooded.At that time the embayments within the Lennard Shelf had been almost filled up.As sea level fell later,a broader carbonate ramp(Gumhole Formation-Yellow Drum Formation)devepoed in the Lennard Shelf and strongly progaraded basinwards.In the early stage of SSQ5,the area developed two periods of mixed carbonate and clastic ramp(Lower Laurel Carbonate Member-Lower Laurel Clastic Member,Upper Laurel Carbonate Member-Upper Laurel Clastic Member).At the Lennard Shelf,the deposits were quiet thin and only preserved the deposits during the transgressive periods.However since the activity of the syndepositonal faults in Fitzroy trough,the deposition thinkened into the Fitzroy trough and a large amount turbidite fans and predelta deposits developed during the regressive periods.Overall,during SSQ2-SSQ5 periods,platform slope break changed its location progrssively across the Lennard shelf,then across the Meda embayment and then into the northern part of Fitzroy Trough.At the end of SSQ5,the study area regionally subsided and the erosion of Kimberley Shield provided increased sediment supply,so that delta began to develope.Finally,Mid Carboniferous Meda transpressional Movement initiated a widespread fold and uplift and resulted in the erosion of the top of the sequece to varing degrees at the Lennard Shelf and the northern margin of the Fitzroy Trough.