The structural boundary between East and West Falkland: new evidence for movement history and lateral extent

Description/Abstract

The contrasting geology of East Falkland with its Lafonian Basin and E–W D1 fold-belt, and West Falkland, with Precambrian basement exposure and NE–SW D2 fold structures, has led previous researchers to infer a steep basement fault beneath the eastern margin of West Falkland. Recent research on the Falkland Islands has revealed further contrasts between East and West Falkland in: (a) the sedimentary, kerogen facies and thermal maturity of the West Falkland and Lower Lafonia groups and; (b) the structural relief of 6–8 km across the Hornby Anticline between West and East Falkland. These factors indicate that East Falkland has been downthrown to the SE along the Hornby Mountain Fault from Devonian until Jurassic times. Interval velocity and Bouguer Gravity data from a seismic line to the SW of the Falkland Islands reveal a similar basement structure to that interpreted under West Falkland and indicate that the fault continues offshore as a series of fault segments for at least 60 km along strike to the SW.