Some physical properties of rocks in the East Cape-Mahia Peninsula Region, North Island, New Zealand

Garrick, R. A.

doi:10.1080/00288306.1969.10431109

Cited by 11 publications

(12 citation statements)

References 6 publications

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“…mudstones tend to flow plastically and form numerous landslips across the region. In exploration wells, the formation is seen to be highly ductile and of low density (Garrick 1969).…”

Section: Geological Settingmentioning

confidence: 96%

Overpressure associated with a convergent plate margin: East Coast Basin, New Zealand

Darby

Funnell

2001

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The East Coast Basin of New Zealand lies in the frontal arc of the Hikurangi subduction zone. Overpressure forms a major hazard for exploration in the basin. Fluid pressures of 12.8 MPa at 600 m depth have been encountered, equivalent to 90% of lithostatic pressure, and mud weights of up to 19.5 ppg are required to control formation fluids at subsurface depths of only 1400 m. The distribution and magnitude of overpressure shows no relation to present-day depth. Lithostratigraphy controls the distribution of overpressure and widespread lowpermeability bathyal mudstones form seals to overpressure across the basin. The transition from normal pressure to overpressure is not associated with any single stratigraphic unit. The Neogene evolution of the plate boundary has given rise to rapid Miocene sedimentation (400 m Ma 1 ) in areas of the basin and has caused disequilibrium compaction. Late Neogene compression has subsequently uplifted the overpressured, undercompacted sediments by up to 3000 m at rates of 1000 m Ma 1 . Lateral tectonic compression associated with the plate boundary has also caused undrained shear of thick mudstones, leading to extremely high overpressures in deformed sediments independent of depth.

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“…mudstones tend to flow plastically and form numerous landslips across the region. In exploration wells, the formation is seen to be highly ductile and of low density (Garrick 1969).…”

Section: Geological Settingmentioning

confidence: 96%

Overpressure associated with a convergent plate margin: East Coast Basin, New Zealand

Darby

Funnell

2001

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“…Some pioneering studies of the physical properties of North Island rocks were conducted by Garrick in the 1960s (e.g., Garrick 1969). …”

Section: G89018mentioning

confidence: 99%

Porosities and seismic velocities of mudstones from Wairarapa and oil wells of North Island, New Zealand, and their use in determining burial history

Wells

1990

New Zealand Journal of Geology and Geophysics

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The seismic velocities and porosities of mudstones and other fine-grained sedimentary rocks can be used to estimate burial history. The porosity of exhumed mudstone sequences of Wairarapa has been derived from density measurements, and can be used to estimate prior depth of greatest burial, to within about 100m, by the linear regression function, greatest depth of burial = -111 porosity + 4975, or the exponential function, greatest depth of burial = -8636 log porosity + 14384.The velocity trend of the exhumed mudstones of southeastern Wairarapa is not as good an indicator of burial history, as it has only a poor fit to the regression function, greatest depth = 2666 velocity -3331. However, fully loaded, fme-grainedsedimentaryrocks (mainly mudstones) still under lithostatic pressure in North Island oil wells have a good fit to the velocity-depth regression functions, depth = 1026 velocity -1419 or, depth = 6617 log velocity -1403. This relationship can be used to calculate the thickness of sediment missing from the stratigraphic column.Comparison of the velocity-depth trend of a partially unloaded, fme-grained sedimentary rock sequence in western Wairarapa with that of several other partially unloaded New Zealand sequences with a known history of vertical uplift (as shown by oil wells) indicates that 1100-1500 m of sediment has been unloaded by erosion.

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“…Garrick (1969) has proposed a velocity-age relationship for New Zealand geosynclinal sediments, based principally on rocks of the North Island. If this relationship (Garrick 1969, fig. 4) applies also to the Haast Schist Group of the South Island, these rocks must be of middle to lower Mesozoic age.…”

Section: Age Of Haast Schist Groupmentioning

confidence: 99%

Seismic Velocity Studies in the Southern Alps, New Zealand

Garrick¹,

Hatherton²,

Waiters

1973

New Zealand Journal of Geology and Geophysics

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Seismic velocities of outcropping basement rocks were measured at 3 5 sites east and west of the Alpine Fault. Velocities range from 3·20km/s to 5·15km/s and although there are no statistical differences between the velocity distributions east and west of the fault, local velocity variations have geological implications.Estimates of the contribution to velocity of metamorphic grade and alignment of schistosity are made on the basis of field and laboratory results. In some areas velocity is controlled by the degree of crushing of the rock although such low velocities have not been traced deep!'r than 100 m. The garnet oligoclase schist close to the Alpine Fault consistently has a low velocity (3 · 2-3 · 6 km/s).Reflections 11-21 km east of the fault are tentatively explained as being derived either from the top of an old magma chamber, or from the Alpine Fault plane should this dip south-east. The Haast Schist Group was found to have velocities similar to rocks of Mesozoic age.

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Some physical properties of rocks in the East Cape-Mahia Peninsula Region, North Island, New Zealand

Cited by 11 publications

References 6 publications

Overpressure associated with a convergent plate margin: East Coast Basin, New Zealand

Overpressure associated with a convergent plate margin: East Coast Basin, New Zealand

Porosities and seismic velocities of mudstones from Wairarapa and oil wells of North Island, New Zealand, and their use in determining burial history

Seismic Velocity Studies in the Southern Alps, New Zealand

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