Abstract
The Waimea-Flaxmore Fault System (W-FFS) from the Nelson-Richmond urban area to D’Urville Island is analysed through six regional transects that join depth-converted seismic lines in Tasman Bay to onshore cross sections. Reverse reactivation of basement faults of the W-FFS by mechanisms of fault-propagation folding at c. 19-10 Ma occurred along the entire length of the fault system. However, the W-FFS remained Quaternary active only from the vicinity of Cape Soucis southwards into onshore Nelson, in contrast with cessation of activity along eastern Tasman Bay since 7 Ma. The inactive western faults of the W-FFS are buried below Plio-Quaternary marine sediments and segmented by the newly identified, c. E-W, Croisilles Fault Zone, Cross Point and D’Urville faults, with cumulative dextral offset of c. 27 km. The c. E-W faults extend from the onshore into Tasman Bay and are interpreted as the northernmost Late Miocene strands of the Marlborough Fault System that have accommodated incipient distributed shear in the crustal block north of the Queen Charlotte Fault Zone. Segmentation and along-strike changes of the W-FFS occur at the transition from the contractional domain of onshore Nelson to the northern Marlborough strike-slip domain, driven by large-scale kinematics of the Australia-Pacific plate boundary.