Date of Award
Thesis open access
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 methods were used to measure uplift rate of the marine terraces: 1) collecting shell samples for AAR dating in order to refine terrace ages; 2) use of DGPS surveys to collect the elevations of marine terrace inner edges and possible marine terrace erosional surfaces; 3) creating several cross-sections based on the DGPS surveys to refine terrace boundaries; and 4) calculating the uplift rate of all marine terraces along the North Canterbury fold and thrust belt to determine possible structural influence on local uplift.
Amino acid rasterization (AAR) and optically stimulated luminescence (OSL) dating techniques were used to date the youngest terrace, Qt3, at ~100 ka, placing Qt3 at marine isotope stage (MIS) 5c. Correlations to sea level highstands from inner edge elevation projections from the cross-sections were used to date Qt2 at ~120 ka and Qt1 at ~210 ka. Correlations of inner edge elevations to the Cass and Montserrat anticlines show that inner edges closest to the anticlinal axis were generally higher in elevation than points farther from the anticlinal axis. However, this was not the case for all GPS survey points as GPS surveys in the southern region of the field exhibit low elevations and are in close proximity to the anticlinal crest. Therefore another mechanism must contribute to marine terrace uplift as well.
Topographic profiles created from LIDAR and calculated uplift rates provide evidence of marine terrace southwestward tilting, following the southwestward plunge of the Cass anticline and southwestward propagation of the Hamilton fault and other thrust faults in the NCFTB. The 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, or belong to the oldest terrace, Qt1 (MIS 7a), and have therefore experienced 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.
Stewart, Mary Kate, "Uplift rate of marine terraces and anticlinal growth along the North Canterbury fold and thrust belt, New Zealand" (2015). Geosciences Student Honors Theses. 15.