No abstract

No abstract

Break-up ofthe NorthAtlantic inthe Paleocenewasaccompaniedbywidespread magmatism,which providesac hallenge bothto imagingb asins tructurea ndto modellingthe subsidence andd evelopment ofthe continentalm argins. The rationalef or newm ethodso fseismic acquisition andmodellinga rereported here, followed byanillustration ofthe techniqueswithdatafrom the Faroesregion,which laycloseto the hottest part ofthe mantleplumeatthe timeofcontinentalbreak-up. Igneous rockswereadded to the crust duringcontinental break-up on rifted margins asextrusivelavas,assills intruded into the subsurface, andaslowercrustalintrusions or underplate.Each provide different,but tractableproblems to seismic imaging.Itisshown thatmany ofthese difficultiescanbe surmounted byusingvery longoffsets (longstreamers or two-shipmethods) withabroad-band, low-frequencysource, andbyusingdensearrays ofoceanbottom seismometers to provide complementary P-and S-wavevelocity control. Thesemethodsarei llustrated usingnewr esults from the integrated Seismic Imaging andModellingofMargins (iSIMM)project,which acquired regionaldataacross the Faroesshelfandmarginin summer2002. The iSIMM profileused 85 four-component oceanbottom seismometers anda104litre(6340in 3 ) airgun arrayfor wide-angled ata, withverticalarrays for far-fieldsource signaturerecording.The wide-angle profileswereovershot usingthree single-sensor,Q-Marinestreamers,one12 kmlong, the othertwo 4kmlong. A48-gun,167 litre(10 170 in 3 )deep-towed, broad-bandairgun arraywasused withthe Q-marinestreamers. The airgun arrays wered esigned andtuned to enhance the bubblepulses,withpeak frequenciesat8-11 Hz. They performed well,withexcellent arrivals visibleto rangesbeyond120 kmonthe OBS, andpenetration through the basalts andwell into the uppermantle.Examplesareshown ofthe newseismic data, which enableimagingofthe basalt flows andunderlyingsediments,aswell aslower-crustaligneous intrusions.Thisallows goodconstraints to be placed on the igneous distribution andvolumesonthe rifted marginandadjacent continentalshelf.

No abstract

No abstract