The opening of Cook Strait: Interglacial tidal scour and aligning basins at a subduction to transform plate edge

hence drainage restriction at Taita Gorge. Elevated Last Glacial terraces at the northeast and southwest ends of the basin dip below Holocene gravels towards the middle of the basin, indicating relative longitudinal basin subsidence.Keywords NZMS 260 R27; Wellington; Upper Hutt Basin; Quaternary; sediments; seismic reflection; gravity; deformation; Wellington Fault; active basin development Abstract The Upper Hutt Basin is one of three onshore Quaternary basins in the Wellington region, New Zealand. This northeast-trending basin is bounded along its northwest margin by the predominantly strike-slip Wellington Fault, northwest of which upthrown Torlesse Terrane basement rocks crop out. Quaternary sediment filling the basin rests unconformably on the basement rocks, onlapping the sloping basement surface at the east side of the basin. Interpretation of the seismic and gravity data indicates a total sediment thickness of c. 360-480 m in the main Upper Hutt Basin and 225 m in the Witako Basin. Gravity modelling indicates a dip of c. 60° to the northwest for the Wellington Fault, and has defined a basement high within the basin, which is the subsurface continuation of a NNE-trending topographic spur. The basement high separates a sub-basin, the Witako Basin, from the main Upper Hutt Basin. A drillhole near the basement high penetrated interbedded 10-50 m thick gravel and silt/peat units and reached basement at 204 m. Other drillholes indicate that this stratigraphy, at least in the upper 80 m, is consistent in the southwest area of the basin. There are few constraints on the chronology of the sequence in the basin, but a unit of silt and peat between 51.5 and 68 m depth in one drillhole yielded cool climate pollen assemblages and is of early Last Glacial age (50-80 ka).

Section: The Age Of the Upper Hutt Basinsupporting

confidence: 62%

Quaternary stratigraphy, structure, and deformation of the Upper Hutt Basin, Wellington, New Zealand

Melhuish

Begg

Bannister

et al. 1997

“…1) (Lewis et al 1994). Reconstructions of the New Zealand plate boundary zone show that the strait has been situated approximately within this transition area for at least 20 m.y.…”

Section: Southern Cook Strait Forms the Transition Between Northmentioning

confidence: 93%

Quaternary faulting in the offshore Flaxbourne and Wairarapa Basins, southern Cook Strait, New Zealand

Barnes

Audru

1999

“…Sand is probably transported from the South Island into Greater Cook Strait, and onto the Wanganui shelf, chiefly during storms. Velocities of c. 20 cm/s are required 10 transport fine sand (Carter & Lewis 1995), and under normal conditions tidal currents on the open Wanganui shelf are typically slower than this (Carter 1980;Lewis et al 1994). However, when the tidal flows are intensified by grounding storm waves from the west, they are capable of stirring bottom sediment down to c. 70 m during annual storms and c. 130 m during the maximum 25 yr storm (Lewis 1979).…”

Section: Terrigenous Fractionmentioning

confidence: 99%

“…Greater Cook Strait, in contrast, receives a relatively large amount of terrigenous material from both North and South Island sources. Approximately 18 million tonnes per year is delivered by rivers from the Greater Cook Strait catchment (Harris 1990), plus an additional 6.7 million tonnes, largely detritus from erosion of the Southern Alps, is delivered by oceanic currents (Lewis et al 1994; Fig. 1).…”

Section: Terrigenous Inputmentioning

confidence: 99%

“…North Island river-derived sand remains trapped on the inner shelf, and most of the mud is either transported in suspension through the mid-shelf zone and deposited in the deeper, lowenergy Cook Strait Basin depocentre, or is carried directly southeast along the Manawatu coast and through the Cook Strait Narrows to be lost entirely from the Wanganui shelf system (Lewis 1979;Lewis et al 1994). There is a paucity of micas and chlorite in the sand fraction of high-carbonatezone sediments, indicating that much of the material being swept into Greater Cook Strait from the South Island passes to the south of this zone.…”

Section: Terrigenous Inputmentioning

confidence: 99%

See 1 more Smart Citation

Distribution and control of mixed terrigenous‐carbonate surficial sediment facies, Wanganui shelf, New Zealand

Gillespie

Nelson

1996

Shallow-marine, mixed temperate, terrigenouscarbonate sediments are accumulating on the shallow to deep Wanganui shelf (c. 20-110 m water depth). From cluster analysis of textural and compositional parameters, five surficial sediment facies and five subfacies have been defined for the shelf. Facies 1 (Bivalve-bearing [gravelly] sand), is a terrigenous-dominated, shallow shelf facies (<50 m), incorporating Subfacies la (Sand)-a modern felsic sand prism-and lb (Bivalve-bearing volcaniclastic gravelly sand)-modern to relict andesitic detritus and shell fragments. Facies 2 (Skeletal-dominated sandy gravel) comprises sediments containing >50% CaCO 3 , and occurs in the shallow to mid shelf region (c. 30-90 m) where levels of terrigenous input are reduced, and substrates and hydraulic conditions are favourable for carbonate production. Facies 2 comprises Subfacies 2a (Bivalve-dominated sandy gravel), 2b (Bryozoan/bivalve-dominated sandy gravel), and 2c (Bryozoan/bivalve-dominated muddy sandy gravel and gravelly muddy sand). Facies 2 sediments are