Skip to Main Content
Skip Nav Destination
GEOREF RECORD

Strike-slip structure and sedimentary basins of the southern Alpine Fault, Fiordland, New Zealand

Philip M. Barnes, Rupert Sutherland and Jean Delteil
Strike-slip structure and sedimentary basins of the southern Alpine Fault, Fiordland, New Zealand
Geological Society of America Bulletin (April 2005) 117 (3-4): 411-435

Abstract

The Alpine Fault is an 850-km-long, continental dextral strike-slip fault that accommodates some 60%-90% ( approximately 20-30 mm/yr) of the obliquely convergent motion between the Pacific and Australian Plates in South Island, New Zealand. The southern 230 km of the fault traverses the continental margin off Fiordland and intersects the subduction thrust at the northern end of the Puysegur Trench. Marine seismic reflection profiles and bathymetric data are used to evaluate the late Quaternary structure and 3 m.y. evolution of the fault and five sedimentary basins. The fault offshore is more complexly segmented than its onshore counterpart, and at sedimentary basins has substantial (>1 km) bathymetric relief. Three right-stepping and overlapping active sections are identified on the basis of structural continuity and geomorphic expression. The northern, Milford-Caswell section, is 90 km long and continuous with the southern Westland section on land. The southern, Resolution section is 150 km long and developed from initially discontinuous, right-stepping segments. These sections overlap by 35 km at the large Secretary-Nancy Basin, which is currently being dissected longitudinally by the Nancy section, resulting in a straighter, almost fully linked principal displacement zone. The average strike of the fault differs from the azimuth of Pacific-Australian Plate motion by 11 degrees -25 degrees . Nevertheless, on the whole, the structure, tectonic geomorphology, and lateral displacements indicate predominantly dextral strike-slip displacement. The basins have the structural characteristics of pull-apart and releasing-bend basins. They commonly initiated at step-overs in the fault and evolved by development of very oblique cross- and along-basin faults that linked the principal displacement zone, resulting in longer, through-going surface traces. Localized transpressional features are developing contemporaneously with the basins and may relate to constrictional fault geometries and/or a 10 degrees rotation of part of the fault within the last 3 m.y., rather than to changes in plate motions. The absence of significant regional contraction across the fault indicates that obliquely convergent plate motion is strongly partitioned. The convergence normal to the boundary is accommodated largely on thrust and reverse faults offshore and onshore, to the northwest and southeast of the Alpine Fault, respectively. The position of the Alpine Fault is clearly associated with the position of inherited Eocene rift structures carried in the subducting Australian Plate. Our observations and kinematic model imply a spatial-temporal evolution where the position of the southwestern end of the fault trace is transitory on a time scale of 10 (super 5) -10 (super 6) years, and the fault matures toward the northeast. The data are consistent with models invoking dextral reactivation of the subducting rift structures and tearing of the Australian Plate in the approximate direction of plate convergence, and/or the loading of shear stresses and strike-slip deformation on the Alpine Fault in response to spatial differences in surface roughness and interplate coupling. Several potential earthquake scenarios on the Alpine Fault are considered, ranging from rupture of individual structural sections associated with earthquakes of magnitude M 7.0-7.8, to larger, onshore-offshore composite ruptures of up to M 8.1.


ISSN: 0016-7606
EISSN: 1943-2674
Coden: BUGMAF
Serial Title: Geological Society of America Bulletin
Serial Volume: 117
Serial Issue: 3-4
Title: Strike-slip structure and sedimentary basins of the southern Alpine Fault, Fiordland, New Zealand
Affiliation: National Institute of Water and Atmospheric Research, Wellington, New Zealand
Pages: 411-435
Published: 200504
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 72
Accession Number: 2005-031012
Categories: Structural geology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. sects., 1 table, geol. sketch maps
S47°00'00" - S44°00'00", E164°30'00" - E168°30'00"
Secondary Affiliation: Institute of Geological and Nuclear Sciences, NZL, New ZealandCNRS Geosciences Azur, FRA, France
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 200511
Close Modal

or Create an Account

Close Modal
Close Modal