The efficacy of kinematic indicators in a complexly deformed Mass Transport Deposit: Insights from the deepwater Taranaki Basin, New Zealand

摘要

Analysis of a high-resolution three-dimensional (3D) marine seismic reflection dataset acquired in the Deepwater Taranaki Basin, New Zealand provides insights into the significance of kinematic indicators observed on the basal shear surface of a giant Mass Transport Deposit (MTh 2). The deposit covers an area of 22,397 km(2), has an estimated volume of 3733 km(3) and is of Pliocene age. Regional mapping using 2D seismic reflection data suggested a SW transport direction for MTD 2. Kinematic indicators derived from our 3D seismic interpretation provide conflicting evidence for the transport direction of at least a portion of MTD over only a few kilometres distance and so it was necessary to test their efficacy. Mapping of the basal shear surface revealed two sets of lineations, ramp, and scours (interpreted as paleo-channels) while 3D attribute analysis of the internal architecture revealed systematic domains of consistent internal deformation, including (i) a blocky Domain A dominated by extension, (ii) Domain B dominated by short wavelength folds and thrusts, (iii) Domain C characterised by strain overprinting, (iv) a homogenised Domain D with partially remnant (ghost) stratigraphy and (iv) a less deformed Domain E. The structural internal architecture suggests a SW transport direction which is consistent with previous interpretations from regional 2D seismic mapping of the entire MTD 2. However, the internal deformational pattern shows local deviations from this regional transport direction. The lineations rank the least; the ramp would be intermediate; and the structural internal architecture ranks the best. This study reinforces the notion that internal deformation of MTDs is often complex and varies laterally over short distances, and that a holistic approach to kinematic analysis is recommended.