Uplift Rate of Marine Terraces and Anticlinal Growth along the North Canterbury Fold and Thrust Belt, New Zealand

Abstract:

This study measures the uplift rates of a flight of marine terraces along the Glenafric coastal region of the South Island of New Zealand, which will provide a context for how local fold growth in the North Canterbury fold and thrust belt (NCFTB) contributes to local uplift rates. Several preliminary methods were used to measure uplift rate of the marine terraces including: 1) use of DGPS surveys to collect the elevations of marine terrace inner edges and possible erosional surfaces 2) collecting shell samples for AAR dating in order to refine terrace ages 3) creating several cross-sections based on the DGPS surveys to refine terrace boundaries; and 4) calculating the uplift rate of each flight of marine terraces along the North Canterbury fold and thrust belt to determine possible structural influence on local uplift.

Correlations of inner edge elevations to the Cass and Montserrat anticlines show that inner edges closest to the anticlinal axis were generally higher than points farther from the axis, indicating proximity to the anticlinal axis as a dominate control on terrace uplift. However, as this is not the case for all GPS survey points, another mechanism must contribute to marine terrace uplift as well. LIDAR topographic profiles and calculated uplift rates show evidence of marine terrace southwestward tilting, following the southwestward plunge of the Cass Anticline and the southwestward propagation of the Hamilton Fault. GPS points with the highest uplift rates (1.0-1.3 m/kyr) are closest to the structural culmination of the Cass or Montserrat anticline, therefore experiencing fold influence and uplift for the longest period of time. Proximity to the structural culmination of each anticline, not proximity to the anticlinal axis, is therefore the dominate control on marine terrace uplift rate.