Gravity survey of the Hawkdun basin.

Author:

Hughes, S. L. M.

Year:

Project type:

Advisers:

Abstract:

Gravity models provide evidence for extensive thrusts on two fault systems in the Hawkdun Basin. Central Otago. These sets of faults trend northwest and northeast and are referred to as the Hawkdun and Manuherikia Fault Systems respectively. The gravity profiles also reveal significant basement topography which is related to these faults.
The orientation of the basin margins departs from northeast and northwest trends where the Hawkdun and Manuhenkia faults do not control the range-fronts. Gravity profiles indicate low-angle sediment/ basement transition in these areas which may be original sedimentological contacts.
Truncation of the northeasterly trending faults by those which trend northwest, an observation which is supported by 1:1M and 1:250 000 Bouguer anomaly maps, implies that the northwesterly trending faults were generated earlier and/or are deeper seated.
Problems in removing the regional variation from the observed gravity wavelength of the values are complicated by the structures controlling the basin and structures which influence the regional gravity field.
The bulk density of the sediment infilling the basin compared to the basement rock is the critical parameter tor gravity interpretation. This density contrast ranges from 0.86 to 0.6Mg/m3 based on electric drill logs. Despite constraints from these logs on density and depth to basement under the sediment, the models presented do not always fit the observed residuals. It is concluded that the problem with regional removal is compounded by three-dimensional effects from complex lateral density changes in the Hawkdun Basin.
The Hawkdun and Manuherilda thrusting fault systems revealed by this study are the expression of the continuing compressional tectonic regime in New Zealand caused by the collision of the Indian and Pacific plates. Strain measurements from other regions in the South Island suggest that both sets of faults are currently active.

Named Localities:

Thesis description:

64 leaves : ill. (some col.), maps ; 30 cm.

Department:

OU geology Identifier:

1984Hughes

Author last name:

OURArchive handle:

OURArchive access level:

Location (WKT, WGS84):

POLYGON ((169.843932088292917 -44.865329939080048,169.8506967159542 -44.750475080303403,169.9595647268508 -44.749140835097755,169.956916995764857 -44.866255759474939,169.843932088292917 -44.865329939080048))

Files

http://download.otagogeology.org.nz/temp/Abstracts/1984Hughes.pdf

Collection

Citation

Hughes, S. L. M., “Gravity survey of the Hawkdun basin.,” Otago Geology Theses, accessed May 22, 2024, https://theses.otagogeology.org.nz/items/show/177.

Output Formats