Understanding our dynamic landscape gives us great insight into the past and the ability to make educated predictions of possible future events of the world we live in today. The Mackenzie basin is a wide valley basin containing three glacial lakes which have the potential to provide understanding into the glacial, tectonic and climate history of the Southern hemisphere and in particular, New Zealand. The South Island of New Zealand is characterised by oblique continental collision of the Australian and Pacific tectonic plates, forming the dominant Southern Alps. The plate boundary is known as the Alpine fault and attention has often be associated with motion on the western side of the ...view middle of the document...
Gravity cores collected (P&I ’83) show that the lake basin is varved. Varved sediments are seasonal deposits which comprise of paired layers that contrast in appearance, typically light and dark layers. Counting of these deposits yielded a sedimentation rate of 1± 0.1cm.yr-1.
The geology of surrounding area consists of Torlesse greywacke on the south-western shores of Lake Tekapo and is of textural zone 1, meaning it is metamorphosed sandstone that has no recognisable alignment of minerals (foliation). Fault rocks are seen on the beaches of the lake north of the Torlesse greywacke outcrops. Upton et al1 infers that it is likely that fault rocks are more extensive underneath the beach, implying that the ICF does indeed trace into the lake basin, however I believe this has not been well constrained as a gap between mapped fault trace and seismic evidence of the ICF is evident.
Fine grained sediment is found well above current lake levels, most likely the result of high water levels from the last deglaciation (Cox and Barrell ’07). Small offsets and folds are observed in these sediments next to an inferred extension of the ICF. Deformation of these sediments is attributed to movement on the ICF or less likely drainage of the lake basin from deglaciation.
Seismic survey of Lake Tekapo
The seismic survey consisted of eight lines (three along the length and five bisecting those). Three seismic units were identified from the reflection data.
1) basement 2) Moraine 3) Fan and Lake Fill (1->3 younging)
and natural gas and mass movement deposits were observed.