Investigation of fold growth in North Canterbury, South Island, New Zealand

Open Access
Author:
Vanderleest, Rebecca Anne
Graduate Program:
Geosciences
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
July 16, 2015
Committee Members:
  • Donald Myron Fisher, Thesis Advisor
  • Roman Alexander Dibiase, Thesis Advisor
  • Kevin Patrick Furlong, Thesis Advisor
  • Michael Allan Arthur, Thesis Advisor
Keywords:
  • terraces
  • fold
  • trishear
Abstract:
The North Canterbury fold and thrust belt is seismically active and located at the southern end of the Hikurangi subduction zone on the South Island of New Zealand. The thrust belt is in a region where the Pacific plate transitions from subduction to transpression along the Alpine Fault leading to lateral migration of the edge of the Pacific plate. This lateral migration causes shortening beneath the South Island because basement normal faults related to Cretaceous-Paleocene rifting are reactivated as thrusts. These basement thrust faults generate folds within the North Canterbury thrust belt. In this region, the Montserrat Anticline is exposed along the coast where a spectacular flight of marine terraces records late Pleistocene tectonic uplift. The landward vergent Montserrat Anticline folds a Cretaceous to Pleistocene cover sequence. Paralleling the northwest limb, the Glendhu Fault thrusts Jurassic-Cretaceous basement rock against a Pliocene formation at the northeast end of the anticline and thrusts a Miocene formation against an early Oligocene formation at the southwest end. This juxtaposition reflects motion on a seaward dipping reverse fault rooted within the Jurassic-Cretaceous basement. On the southeast limb of the anticline, the Happy Valley fault offsets the MIS 3 terrace by 10 m. To constrain fault slip rate and fault ages, fault-related fold kinematics were modeled using the trishear fold model appropriate for basement faults that drive cover sequence folding. Batch inverse models were run to generate the bedrock geology and bedding attitudes and to develop probability density distributions for important variables such as ramp angle and slip. Marine terraces were dated using amino acid racemization and optically stimulated luminescence and constrain terrace ages to highstands MIS 3, MIS 5a, and MIS 5e. The time-averaged regional uplift rate is 1.0 m/ka ± 0.2 m/ka. The constraint on the uplift rate, fault slip, and fault age correspond to a recurrence interval for maximum displacement per Mw = 6.2 event for the Glendhu Fault of 262 to 310 years and for the Happy Valley Fault of 5,244 years.